1
Q
What are the two main sections that make up the overall nervous system?
A
The Central Nervous System (CNS) The Peripheral Nervous System (PNS)
2
Q
What are the anatomical components of the Central Nervous System (CNS)?
A
The Brain and the Spinal Cord.
3
Q
What constitutes the Peripheral Nervous System (PNS) and what is its general function?
A
Composition: It consists of the rest of the nervous system (outside of the brain and spinal cord). Function: It generally serves as a link between the CNS and the effector organs.
4
Q
Based on the direction of information carried, how is the PNS further divided? (Include alternate names)
A
Afferent division (also called the Sensory division). Efferent division (also called the Motor division)
5
Q
What is the specific function of the Afferent (Sensory) division?
A
It is responsible for sending afferent information towards the nervous system.
6
Q
What are the two types of “environments” the Afferent division carries information from? Provide examples for each
A
External environment: e.g., light and sound. Internal environment: e.g., information about blood pressure
7
Q
What is the specific function of the Efferent (Motor) division?
A
It sends information from the nervous system to the organs of the body, which then carry out the appropriate response.
8
Q
Functionally, how does the CNS interact with incoming information?
A
The CNS receives and processes incoming sensory information and responds by sending out signals that initiate a response.
9
Q
The efferent division of the Peripheral Nervous System (PNS) is further divided into what two components?
A
The Somatic Nervous System (SNS). The Autonomic Nervous System (ANS)
10
Q
What is the Somatic Nervous System (SNS) associated with and what specific effectors does it utilize?
A
It is associated with the voluntary control of body movements via skeletal muscles.
11
Q
What is an alternative name for the Somatic Nervous System?
A
The voluntary nervous system
12
Q
How does the Autonomic Nervous System (ANS) function relative to consciousness?
A
It functions largely below the level of consciousness.
13
Q
What specific functions and effectors does the Autonomic Nervous System (ANS) control?
A
It controls visceral functions and visceral organs via: Smooth muscles Cardiac muscles Glands
14
Q
What are two alternative names for the Autonomic Nervous System (ANS)?
A
Involuntary nervous system. Visceral nervous system.
15
Q
What is the fundamental difference in “Control” between the Somatic Nervous System (SNS) and the Autonomic Nervous System (ANS)?
A
Somatic Nervous System: It is a voluntary motor system under conscious control. Autonomic Nervous System: It is an involuntary system.
16
Q
How does the “Number of neurons in the pathway” differ between the SNS and the ANS?
A
Somatic Nervous System: Controlled by a Single neuron (motoneuron) along the pathway. Autonomic Nervous System: Controlled by Two neurons (Preganglionic and Postganglionic neuron) along the pathway.
17
Q
Compare the “Cell body location” for the neurons in the SNS versus the ANS.
A
Somatic Nervous System: The single neuron is located in the CNS. Autonomic Nervous System: Preganglionic neuron: Located in the CNS. Postganglionic neuron: Located in the autonomic ganglion (a mass of neuron bodies outside of the CNS)
18
Q
In the context of the ANS, what is a “ganglion” and what happens there?
A
Definition: A ganglion is a mass of neuron bodies outside of the CNS. Function: It is the place where the two neurons (preganglionic and postganglionic) form a synapse.
19
Q
What are the specific terms for the first and second neurons in the ANS pathway?
A
1st Neuron: Called the preganglionic neuron. 2nd Neuron: Called the postganglionic neuron.
20
Q
What are the “Effectors” (target organs) for the SNS and the ANS?
A
Somatic Nervous System: Skeletal muscles. Autonomic Nervous System: Cardiac muscles, smooth muscles, and glands.
21
Q
Describe the molecular mechanism (neurotransmitter and receptor) of the Somatic Nervous System pathway
A
Neurotransmitter: Motor neurons release ACh (Acetylcholine). Receptor: Binds to nAChR (nicotinic Acetylcholine receptors) located on the skeletal muscle. Result: Triggers physiological actions.
22
Q
Describe the molecular mechanism at the first synapse (between neurons) in the Autonomic Nervous System.
A
Neurotransmitter: The Preganglionic neuron releases ACh. Receptor: Binds to nAChR (nicotinic Acetylcholine receptors) on the Postganglionic neuron
23
Q
Describe the molecular mechanism at the effector junction (target organ) in the Autonomic Nervous System (include all specific receptors mentioned)
A
Neurotransmitters: The Postganglionic neuron releases either ACh or Norepinephrine. Receptors: For ACh: mAChR (muscarinic Acetylcholine receptors). For Norepinephrine: Adrenoreceptors (specifically $\alpha_1$, $\alpha_2$, $\beta_1$, $\beta_2$).
24
Q
Into what two subsystems is the Autonomic Nervous System (ANS) classically divided?
A
Sympathetic Nervous System (SNS). Parasympathetic Nervous System (PSNS)
25
How do the Sympathetic and Parasympathetic divisions generally interact with each other regarding physiological responses?
They often have opposite actions. One usually activates a physiological response, while the other inhibits it.
26
What is the general responsibility of the Sympathetic Nervous System (SNS)?
t is responsible for stimulating activities associated with the 'fight-or-flight' response.
27
What are specific examples of situations where the Sympathetic Nervous System (SNS) is activated?
Fear. Taking a difficult exam. Running away from a burning house. Fighting an attacker
28
What is the general responsibility of the Parasympathetic Nervous System (PSNS)?
It is responsible for the stimulation of 'rest-and-digest' activities that occur when the body is at rest.
29
What specific bodily activities are associated with the Parasympathetic Nervous System (PSNS)?
Sexual arousal.Salivation.Lacrimation (tearing).Urination.Digestion.Defecation.
30
Based on the diagram on Slide 6, from which regions of the CNS do Sympathetic fibers originate
The Thoracic region (T1–T12). The Lumbar region (L1–L2). (Collectively known as the Thoracolumbar outflow).
31
Based on the diagram on Slide 6, from which regions of the CNS do Parasympathetic fibers originate?
The Brainstem (via Cranial Nerves). The Sacral region of the spinal cord (S2–S4). (Collectively known as the Craniosacral outflow).
32
Which specific Cranial Nerves carry parasympathetic fibers as shown in the Slide 6 diagram?
Cranial nerve III (Oculomotor).Cranial nerve VII (Facial).Cranial nerve IX (Glossopharyngeal).Cranial nerve X (Vagus).
33
What is the specific segmental breakdown of the spinal cord (total number and specific regions)?
The spinal cord is made up of 31 segments: 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal
34
Where are the cell bodies of preganglionic sympathetic neurons located?
They are located in the thoracic and lumbar regions of the spinal cord, specifically from T1 to L2.
35
Due to the location of its preganglionic neurons, what is the Sympathetic Division also referred to as?
The Thoracolumbar division.
36
How do the axons of preganglionic sympathetic neurons exit the spinal cord?
They leave the spinal cord via the ventral roots.
37
Where are the ganglia of the sympathetic nervous system generally located relative to the spinal cord?
They are located near the spinal cord.
38
What are the two distinct groups of sympathetic ganglia
Paravertebral ganglia. Prevertebral ganglia.
39
What is another name for Paravertebral ganglia and why are they named that way?
They are also known as the sympathetic chain because these ganglia form a chain-like structure along the spinal cord.
40
What is another name for Prevertebral ganglia and what specific ganglia does this group include?
They are also called collateral ganglia. This group includes the:
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
41
What are the two synaptic pathways a preganglionic sympathetic neuron can take regarding the sympathetic chain?
Synapse within the chain: The neuron synapses on a postganglionic neuron within the sympathetic chain.
Pass through: The neuron passes through the sympathetic chain without synapsing and continues on to synapse in a prevertebral ganglion.
42
Describe the relative lengths of the preganglionic and postganglionic axons in the Sympathetic Division.
Preganglionic axon: Short. Postganglionic axon: Long
43
Why are the sympathetic axon lengths arranged as short (preganglionic) and long (postganglionic)?
Because the sympathetic ganglia are located near the spinal cord, the postganglionic axons must be long to travel to the periphery to reach and innervate the effector organs.
44
In the context of the Sympathetic Nervous System, how is the Adrenal Gland classified?
It is classified as a specialized sympathetic ganglion.
45
Describe the basic anatomical structure of the adrenal gland mentioned in the text.
Its core is called the adrenal medulla, which is surrounded by the adrenal cortex.
46
Where are the cell bodies of the preganglionic neurons that innervate the adrenal medulla located? (Be specific).
They are located in the thoracic spinal cord, specifically segments T5-T9
47
Describe the unique pathway of the preganglionic axons traveling to the adrenal medulla regarding the other ganglia they encounter.
The axons pass through the sympathetic chain and the celiac ganglion without synapsing.
48
Upon reaching the adrenal medulla, what specific cells do the preganglionic neurons synapse on?
They synapse on chromaffin cells.
49
What neurotransmitter is released by the preganglionic sympathetic neurons that innervate the adrenal medulla?
Acetylcholine (ACh).
50
What specific receptor on the Chromaffin cells of the adrenal medulla does ACh activate?
Nicotinic AChR (nAChR)
51
Once activated by ACh, what class of chemical substances do the chromaffin cells secrete?
Catecholamines
52
What are the two specific types of catecholamines secreted by the adrenal medulla?
Epinephrine. Norepinephrine.
53
Unlike typical postganglionic neurons that release neurotransmitters at a specific synapse, where do chromaffin cells release catecholamines?
They secrete them into the general circulation (specifically into capillaries) to cause physiological actions.
54
What is the general structural similarity between the sympathetic and parasympathetic pathways connecting the CNS to effector organs?
Both pathways consist of two neurons in series that connect the CNS and effector organs.
55
From which specific locations do the preganglionic neurons of the parasympathetic division arise? (List specific nerves and segments).
Nuclei of Cranial Nerves: III, VII, IX, and X. Spinal Cord: Sacral region segments S2-S4.
56
Where are the cell bodies of the preganglionic parasympathetic neurons located?
They are located in the brain stem and the sacral region of the spinal cord
57
Due to the origin of its preganglionic neurons, what is the Parasympathetic Division also referred to as?
The Craniosacral division.
58
How does the location of parasympathetic ganglia differ from sympathetic ganglia?
Sympathetic ganglia: Located near the CNS (spinal cord).Parasympathetic ganglia: Located near, on, or even in the effector organs
59
Where specifically are the cell bodies of the postganglionic parasympathetic neurons located?
They are located within or very close to the effector organs
60
Describe the relative lengths of the axons in the Parasympathetic Division and the reason for this arrangement.
Preganglionic axons: Long. Postganglionic axons: Short. Reason: This is because the parasympathetic ganglia are located near or in the effector organs.
61
Within the ganglia of the ANS, what type of connection does the preganglionic axon make with the postganglionic neuron?
It forms a synapse that is the same as any other synapse between two neurons.
62
What is the specific term for the connections made by the end of postganglionic neurons with their target tissues (effector organs)?
Neuroeffector junctions.
63
To what structure in the somatic nervous system is the neuroeffector junction analogous?
The Neuromuscular junction (NMJ) (the synapse formed between motor neurons and muscles).
64
Structurally, how does the organization of the Neuromuscular junction differ from the Neuroeffector junction?
Neuromuscular junction: Has a discrete and organized structure called the motor end plate. Neuroeffector junction: The postganglionic neurons form diffuse and branching networks.
65
What is the specific site of neurotransmitter synthesis, storage, and release in the Neuromuscular junction?
The nerve terminals.
66
What are the specific sites of neurotransmitter synthesis, storage, and release in the Neuroeffector junction?
Varicosities (or beads) that line along the branching networks.
67
To what structure in the neuromuscular junction are the varicosities of the neuroeffector junction analogous?
The presynaptic nerve terminals.
68
Compare the structural arrangement of the Neuromuscular junction (NMJ) versus the Neuroeffector junction.
Neuromuscular junction: Has a discrete, organized structure called the motor end plate. Neuroeffector junction: The postganglionic neurons form diffuse, branching networks.
69
Compare the innervation patterns of the target tissues in the NMJ versus the Neuroeffector junction.
Neuromuscular junction: A skeletal muscle fiber is innervated by a single motoneuron. Neuroeffector junction: Target tissues may be innervated by many postganglionic neurons.
70
What are the specific neurotransmitter storage and release sites in the NMJ versus the Neuroeffector junction?
Neuromuscular junction: Nerve terminals. Neuroeffector junction: Varicosities (beads along the branches).
71
What analogy is drawn between the neurotransmitter release sites of the NMJ and the ANS?
The varicosities of the neuroeffector junction are analogous to the presynaptic nerve terminals of the neuromuscular junction.
72
Compare the distribution of postsynaptic receptors in the NMJ versus the Neuroeffector junction.
Neuromuscular junction: Receptors are located in the specialized motor end plate. Neuroeffector junction: Receptors are widely distributed on the target tissue, and there is no specialized region of receptors analogous to the motor end plate.
73
What are the two stages of neurotransmission in the general ANS pathway?
The preganglionic neuron releases neurotransmitter at the ganglion, which acts on the receptors of the postganglionic neuron. The postganglionic neuron releases neurotransmitter to stimulate receptors on the target organ.
74
What defines an "Adrenergic" neuron?
A neuron that synthesizes and releases norepinephrine.
75
What are the receptors for norepinephrine called and what are the four specific types?
Name: Adrenoreceptors. Types: $\alpha_1$, $\alpha_2$, $\beta_1$, $\beta_2$.
76
Besides norepinephrine, what other substance activates adrenoreceptors
Epinephrine (secreted by the adrenal medulla).
77
: What defines a "Cholinergic" neuron?
A neuron that synthesizes and releases ACh (Acetylcholine).
78
What are the two types of Cholinoreceptors?
Nicotinic acetylcholine receptors (nAChR). Muscarinic acetylcholine receptors (mAChR).
79
Why are the two cholinoreceptors named "Nicotinic" and "Muscarinic"?
Nicotinic: Sensitive to nicotine (a natural product found in tobacco). Muscarinic: Sensitive to muscarine (a natural product found in certain mushrooms).
80
What neurotransmitter is released by ALL preganglionic neurons (Sympathetic and Parasympathetic) in the ANS?
Acetylcholine (ACh).
81
What specific receptor is found on ALL postganglionic neurons to receive the preganglionic signal?
Nicotinic acetylcholine receptors (nAChR).
82
Based on the neurotransmitter released, how are all preganglionic neurons classified?
They are always cholinergic.
83
What neurotransmitter do Sympathetic postganglionic neurons typically release?
Norepinephrine.
84
What receptors do Sympathetic postganglionic neurons typically act on?
$\alpha$- and $\beta$-adrenergic receptors.
85
What is the specific exception regarding Sympathetic postganglionic neurons (location and neurotransmitter)?
Location: Thermoregulatory sweat glands. Neurotransmitter: They release ACh (Acetylcholine).
86
What receptor is activated in the sweat gland exception?
Muscarinic receptors (mAChR).
87
What neurotransmitter do Parasympathetic postganglionic neurons release?
Acetylcholine (ACh).
88
What receptors do Parasympathetic postganglionic neurons act on at the target cells?
Muscarinic receptors (mAChR).
89
Compare the secretions of Sympathetic postganglionic neurons versus the Adrenal Medulla.
Sympathetic Postganglionic: Release only norepinephrine.Adrenal Medulla: Secretes mainly Epinephrine (80%) and a small amount of Norepinephrine (20%).
90
Why is the secretion composition of the Adrenal Medulla different from sympathetic neurons?
Due to the presence of an enzyme in the adrenal medulla which converts norepinephrine to epinephrine.
91
At the ganglion level, what is the neurotransmitter released and the receptor activated for both the Sympathetic and Parasympathetic divisions?
Neurotransmitter: ACh (Acetylcholine). Receptor: nAChR (Nicotinic Acetylcholine Receptor).
92
At the effector organs of the Parasympathetic division, what is the classic neurotransmitter released and what receptor does it activate?
Neurotransmitter: ACh. Receptor: mAChR (Muscarinic Acetylcholine Receptor)
93
At the effector organs of the Sympathetic division, what are the potential neurotransmitters released?
Norepinephrine (most common). ACh (specific cases like sweat glands).
94
At the effector organs of the Sympathetic division, what receptors are activated by the released neurotransmitters?
Adrenoreceptors ($\alpha_1, \alpha_2, \beta_1, \beta_2$)7. mAChR (Muscarinic Acetylcholine Receptor)8
95
Describe the specific pathway of neurotransmission in the Adrenal Medulla (from preganglionic neuron to secretion).
Preganglionic neurons release ACh9. ACh activates nAChR on Chromaffin cells10. Activated chromaffin cells release Epinephrine and Norepinephrine into the circulation11. These hormones activate Adrenoreceptors ($\alpha_1, \alpha_2, \beta_1, \beta_2$) on target cells12
96
Why does a substantial amount of nicotine consumption cause physiological effects in both the Sympathetic and Parasympathetic systems?
Because nicotine activates nAChR (nicotinic receptors) which are located on the postganglionic neurons (at the ganglia) in both systems.
97
Besides classic neurotransmitters, what is the general function of non-classic neurotransmitters released by postganglionic neurons?
They can regulate the action of classic neurotransmitters.
98
What are the specific non-classic neurotransmitters found in the Parasympathetic nervous system?
VIP (Vasoactive Intestinal Peptide). NO (Nitric Oxide)
99
What are the specific non-classic neurotransmitters found in the Sympathetic nervous system?
ATP. Neuropeptide Y
100
What initiates the sequential signal transduction events in the ANS?
The binding of neurotransmitters to their receptors, which leads to the activation of the receptors.
101
Structurally, what type of proteins are G protein-linked receptors (GPCRs)?
They are seven-pass transmembrane proteins.
102
To what larger group of enzymes do G proteins belong?
GTPases.
103
Describe the molecular structure of a G protein (subunits).
It is a heterotrimer made up of three subunits: $\alpha$ (alpha) $\beta$ (beta) $\gamma$ (gamma) 3
104
Which specific subunit houses the activity of the G protein?
The $\alpha$ subunit
105
How does the $\alpha$ subunit act as a molecular switch?
Inactive state: When bound to GDP (guanosine diphosphate). Active state: When bound to GTP (guanosine triphosphate).
106
Step 1 of GPCR Signal Transduction: What is the state of the system when no ligand is bound?
The $\alpha$ subunit is bound to GDP and is in the inactive state.
107
Step 2 of GPCR Signal Transduction: What happens when a ligand binds to the receptor?
The receptor changes its conformation and becomes activated.
108
Step 3 of GPCR Signal Transduction: What exchange is triggered by the activation of the receptor?
The exchange of GDP for GTP on the $\alpha$ subunit. 9999
109
Step 4 of GPCR Signal Transduction: What happens to the heterotrimer after GTP binds?
The $\alpha$ subunit dissociates from the $\beta/\gamma$ subunits.
110
Step 4 (continued): What does the now activated $\alpha$ subunit (bound to GTP) do?
It binds to and activates a target molecule—usually an enzyme—to execute physiological actions.
111
What are two specific examples of target enzymes mentioned in the text?
Phospholipase C Adenylyl cyclase
112
Step 5 of GPCR Signal Transduction: How does the system return to the inactive state?
Ligands dissociate from the receptor. GTP is hydrolyzed to GDP by the intrinsic GTPase activity of the G protein.
113
Which specific receptors in the Autonomic Nervous System are classified as GPCRs?
Adrenoreceptors Muscarinic AChR (Note: Nicotinic are ion channels, not GPCRs).
114
What do the subscripts "s" and "i" stand for in the G protein classes Gs and Gi?
s: Stands for stimulatory. i: Stands for inhibitory.
115
Which specific enzyme is associated with both Gs and Gi proteins?
Adenylyl cyclase (AC).
116
Describe the signaling cascade initiated by the activation of $G_s$ or $G_i$ (enzyme $\rightarrow$ second messenger $\rightarrow$ target).
Enzyme: Activity of Adenylyl cyclase is increased ($G_s$) or decreased ($G_i$)4444. Second Messenger: This causes a change in cyclic adenosine monophosphate (cAMP) levels5555. Target: cAMP interacts with Protein Kinase A (PKA)6666. Action: PKA phosphorylates downstream targets to induce physiologic responses7777.
117
Which specific enzyme is activated by the $G_q$ protein?
Phospholipase C (PLC)
118
: What specific membrane lipid does Phospholipase C (PLC) cleave upon activation by $G_q$?
A minor membrane phosphoinositol called $PI_{4,5}P_2$ (Phosphatidylinositol 4,5-bisphosphate)9999.
119
What are the two second messengers produced when PLC cleaves $PI_{4,5}P_2$?
$IP_3$ (Inositol-1,4,5-triphosphate)10101010. DAG (Diacylglycerol)11111111.
120
What are the downstream physiological effects of increased $IP_3$ and DAG?
$IP_3$: Leads to an increase in intracellular $Ca^{2+}$12121212. DAG: Leads to Protein Kinase C (PKC) activation13131313.
121
Describe the "Direct Action" mechanism of G proteins that does not involve a second messenger.
The G protein directly alters the function of an ion channel.
122
What specific example is given for the direct action mechanism (receptor, location, and channel)?
Receptor: mAChR (Muscarinic Acetylcholine Receptor)15151515. Location: Sinoatrial node of the heart16161616. Action: Direct interaction with $K^+$ (Potassium) channels17171717.
123
To which class of receptors does the $\alpha_1$ receptor belong?
Adrenoreceptors
124
What are the specific locations where $\alpha_1$ receptors are found?
Vascular smooth muscle (of the skin, skeletal muscle, and splanchnic region). Sphincters (of the gastrointestinal tract and bladder). Radial muscle of the iris.
125
What is the general physiological result of activating $\alpha_1$ receptors in these tissues?
Contraction
126
To which specific G protein is the $\alpha_1$ receptor coupled?
The Gq protein.
127
Step 1 ($\alpha_1$ mechanism): Why are $\alpha_1$ receptors inactive under resting conditions?
Because of the binding of GDP (guanosine diphosphate).
128
Step 2 ($\alpha_1$ mechanism): What initiates the activation process?
Postganglionic neurons release norepinephrine, which binds to and activates the $\alpha_1$ adrenoreceptor.
129
Step 3 ($\alpha_1$ mechanism): What happens to the G protein subunits upon receptor activation?
GDP is released from the $\alpha_q$ subunit and replaced by GTP. The active $\alpha_q$-GTP complex detaches from the rest of the G protein.
130
Step 3 (continued): What enzyme does the active $\alpha_q$-GTP complex activate?
Phospholipase C (PLC).
131
Step 4 ($\alpha_1$ mechanism): What does activated Phospholipase C catalyze?
The liberation of Diacylglycerol (DAG) and IP3 from Phosphatidylinositol 4,5-diphosphate (PIP2).
132
Step 5 ($\alpha_1$ mechanism): What is the specific function of IP3?
It causes Ca2+ release from intracellular stores (in the endoplasmic or sarcoplasmic reticulum), resulting in an increase in intracellular Ca2+ concentration.
133
Step 6 ($\alpha_1$ mechanism): What two components are required to activate Protein Kinase C (PKC)?
Ca2+ Diacylglycerol (DAG)
134
Step 7 ($\alpha_1$ mechanism): How does activated Protein Kinase C execute the final physiologic action (e.g., contraction)?
It phosphorylates proteins.
135
Step 8 ($\alpha_1$ mechanism): How does the $\alpha_q$ subunit return to its inactive state?
Its intrinsic GTPase activity converts GTP back to GDP.
136
To which specific G protein and enzyme are Beta-1 and Beta-2 receptors coupled?
They are coupled to adenylyl cyclase via the Gs protein (Stimulatory G protein)
137
Mechanism of Beta Receptor Activation: Step 1 (Inactive State)
In the inactive state, the alpha-s (αs) subunit of the Gs protein is bound to GDP.
138
Mechanism of Beta Receptor Activation: Step 2 (Agonist Binding)
When an agonist (like norepinephrine) binds, a conformational change occurs. GDP is released and replaced by GTP, and the activated alpha-s subunit detaches from the G protein complex.
139
Mechanism of Beta Receptor Activation: Step 3 (Migration)
The alpha-s-GTP complex migrates within the cell membrane and binds to and activates adenylyl cyclase.
140
Mechanism of Beta Receptor Activation: Step 4 (Enzymatic Action)
Activated adenylyl cyclase catalyzes the conversion of ATP to cAMP. cAMP serves as the second messenger.
141
Mechanism of Beta Receptor Activation: Step 5 (Downstream Effect)
cAMP activates downstream protein kinases, which initiate the final physiologic actions.
142
Mechanism of Beta Receptor Activation: Step 6 (Termination)
The intrinsic GTPase activity of the alpha-s subunit converts GTP back to GDP, returning the subunit to its inactive state.
143
What are the specific anatomical locations of Beta-1 receptors?
Heart: Sinoatrial (SA) node, Atrioventricular (AV) node, and Ventricular muscle. Other: Salivary glands, Kidney, and Adipose tissue.
144
What are the specific physiologic functions of Beta-1 receptor activation?
Heart: Increases heart rate, conduction velocity, and contractility. Secretion/Metabolism: Increases secretion of saliva, renin, and lipolysis.
145
What are the specific anatomical locations of Beta-2 receptors?
Vascular smooth muscle of skeletal muscle.Walls of the gastrointestinal tract and bladder.Bronchioles.
146
What is the general physiological function of Beta-2 receptor activation?
Relaxation or dilation.
147
What are the three specific locations of $\beta_1$ receptors within the heart?
Sinoatrial (SA) node. Atrioventricular (AV) node. Ventricular muscle
148
What is the specific physiological effect of activating $\beta_1$ receptors in the Sinoatrial (SA) node?
Increased heart rate.
149
What is the specific physiological effect of activating $\beta_1$ receptors in the Atrioventricular (AV) node?
Increased conduction velocity .
150
What is the specific physiological effect of activating $\beta_1$ receptors in the Ventricular muscle?
Increased contractility
151
Besides the heart, what are three other tissues where $\beta_1$ receptors are expressed?
Salivary glands. Kidney. Adipose tissue.
152
What are the physiological effects of activating $\beta_1$ receptors in salivary glands, kidneys, and adipose tissue?
Salivary glands: Increased secretion. Kidney: Increased secretion of renin. Adipose tissue: Increased lipolysis.
153
: What is renin and what is its function?
It is an enzyme secreted by the kidney that participates in the regulation of blood pressure.
154
What are the three specific locations of $\beta_2$ receptors mentioned?
Vascular smooth muscle of skeletal muscle . Walls of the gastrointestinal tract and bladder. Bronchioles.
155
What is the general physiological result of activating $\beta_2$ receptors in these tissues?
Relaxation and dilation
156
To which specific enzyme and G protein are $\alpha_2$ receptors coupled?
They are coupled to adenylyl cyclase via an inhibitory G protein ($G_i$).
157
Why are $\alpha_2$ receptors considered inhibitory?
Because their coupling via the Gi protein leads to the inhibition of adenylyl cyclase.
158
Mechanism of alpha-2 Receptor Activation: Step 1 (Inactive State)
In the inactive state, the alpha-i subunit of the Gi protein is bound to GDP.
159
Mechanism of alpha-2 Receptor Activation: Step 2 (Agonist Binding)
When an agonist (like norepinephrine) binds, a conformational change occurs. GDP is released from the alpha-i subunit and replaced by GTP, and the activated alpha-i subunit detaches from the G protein complex.
160
Mechanism of alpha-2 Receptor Activation: Step 3 (Enzyme Interaction)
The alpha-i-GTP complex migrates within the cell membrane and binds to and inhibits adenylyl cyclase
161
Mechanism of alpha-2 Receptor Activation: Step 4 (Downstream Effect)
As a result, cAMP levels decrease, which leads to the final physiologic actions.
162
Mechanism of alpha-2 Receptor Activation: Step 5 (Termination)
The intrinsic GTPase activity of the alpha-i subunit converts GTP back to GDP, and the subunit returns to its inactive state.
163
According to Slide 21, where are alpha-2 (a2) receptors located?
In the vascular smooth muscle of certain blood vessels.
164
What is the overall physiological function of activating alpha-2 (a2) receptors in vascular smooth muscle?
To cause tissue relaxation.
165
Besides the postsynaptic membranes of effector cells, where else is the alpha-2 (a2) receptor located?
It is also located on the presynaptic membranes of the postganglionic neurons in both the sympathetic and parasympathetic systems.
166
What are the two forms of presynaptic alpha-2 (a2) receptors?
Autoreceptors. Heteroreceptors.
167
Where specifically are alpha-2 (a2) autoreceptors found?
They are present on the sympathetic postganglionic nerve terminals.
168
How are alpha-2 (a2) autoreceptors activated?
They are activated by norepinephrine released from the same presynaptic nerve terminals.
169
What is the physiological result of activating an alpha-2 (a2) autoreceptor?
It inhibits further release of norepinephrine from that terminal.
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What is the functional purpose of the negative feedback provided by autoreceptors?
It conserves norepinephrine in states of high stimulation of the sympathetic nervous system.
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Where specifically are alpha-2 (a2) heteroreceptors found?
They are present on the parasympathetic postganglionic nerve terminals.
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How are alpha-2 (a2) heteroreceptors activated?
They are activated by norepinephrine released from sympathetic postganglionic nerve terminals that synapse on these parasympathetic neurons.
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What is the physiological result of activating an alpha-2 (a2) heteroreceptor?
It inhibits the release of acetylcholine (ACh) from the parasympathetic postganglionic nerve terminals.
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What is the overall effect of the alpha-2 (a2) heteroreceptor mechanism on organ function?
The sympathetic nervous system indirectly inhibits organ function by inhibiting parasympathetic activity.
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What are the two types of cholinoreceptors found in the ANS, and what are their alternative names?
Muscarinic receptors (also called m-type AChR). Nicotinic receptors (also called n-type AChR).
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Why are they named "Muscarinic" and "Nicotinic"?
Because they are sensitive to two natural products: muscarine and nicotine.
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Where are Muscarinic (mAChR) receptors located?
In all effector organs of the parasympathetic nervous system. In certain effector organs of the sympathetic nervous system (e.g., sweat glands).
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Describe the signaling mechanism for some mAChRs (similar to alpha-1 receptors).
They are coupled to phospholipase C (PLC) via the Gq protein.
179
Describe the "Direct Action" mechanism of mAChRs found in the cardiac sinoatrial node.
When activated by ACh, they activate the Gi protein. The G-beta-gamma subunit is released. This subunit binds directly to and activates K+ channels (Potassium channels).
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What is the physiological result of the direct activation of K+ channels in the sinoatrial node?
It slows the rate of depolarization. It decreases the heart rate.
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Does the direct action mechanism in the heart involve second messengers?
No. There is no stimulation or inhibition of adenylyl cyclase or phospholipase C, and no involvement of any second messenger.
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Where are Nicotinic (nAChR) receptors located?
Motor end plate of skeletal muscle. All postganglionic neurons of both sympathetic and parasympathetic systems. Chromaffin cells of the adrenal medulla.
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Describe the molecular structure of the Nicotinic (nAChR) receptor
It is an integral cell membrane ion channel consisting of five subunits.
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What happens structurally when ACh binds to the alpha subunits of the nAChR?
A conformational change occurs, resulting in the opening of the channel.
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When the nAChR channel opens, which ions flow and in what direction?
Na+ (Sodium) and K+ (Potassium) flow down their electrochemical gradients.
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What is the resulting membrane potential after nAChR activation?
It reaches a depolarizing state around 0 millivolts (midway between the Na+ and K+ equilibrium potentials).
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Why does Curare (an nAChR blocker) cause relaxation of skeletal muscle?
Because Curare blocks the nAChR that is required for the initiation of action potential and muscle contraction.
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Why does Atropine (an mAChR blocker) increase heart rate?
Atropine inhibits mAChR, subsequently inhibiting the parasympathetic division. Since the parasympathetic division is normally inhibitory (it slows the heart), suppressing this inhibitory pathway leads to an increase in heart rate.
189
According to the summary table, which two types of autonomic receptors share the mechanism of "Stimulation of phospholipase C"?
Alpha-1 (Adrenoreceptor) Muscarinic (Cholinoreceptor
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According to the summary table, which two types of autonomic receptors share the mechanism of "Stimulation of adenylyl cyclase" and increasing cAMP?
Beta-1 Beta-2
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Which specific adrenoreceptor is unique in its action of "Inhibition of adenylyl cyclase" and decreasing cAMP?
Alpha-2
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in terms of Vascular Smooth Muscle, how does the location distribution differ between Alpha-1 and Beta-2 receptors?
Alpha-1: Found in vascular smooth muscle of skin, renal, splanchnic, AND skeletal muscle. Beta-2: Found specifically in vascular smooth muscle of skeletal muscle (and not the others).
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According to the table, what are the two distinct groupings of "Effector organs" containing Muscarinic receptors?
Effector organs of the Parasympathetic Nervous System (PNS). Sweat glands of the Sympathetic Nervous System (SNS).
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What is the shared cellular effect of increasing IP3 (Inositol trisphosphate) in both Alpha-1 and Muscarinic receptor pathways?
Increased intracellular Ca2+ (Calcium concentration).
195
What is meant by the term "dual innervation"?
It means that most organs have both sympathetic and parasympathetic innervation.
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Why do the two divisions of the ANS work together via dual innervation?
To finely control the functions of the organs so that they can operate appropriately in different situations.
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How is the functional relationship between the sympathetic and parasympathetic divisions usually described?
They are usually antagonistic; whatever effect one division has on effector cells, the other usually has the opposite effect
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What specific analogy is used to describe the antagonistic relationship between the two divisions?
Sympathetic division: Acts as the accelerator. Parasympathetic division: Acts as the brake.
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What is the overall function of the Sympathetic Nervous System regarding energy and stress?
Its function is to mobilize the body for activity ('fight or flight' responses) when the body is under stress.
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What are four specific examples of situations requiring the Sympathetic "quick response"?
Responding to fear. Taking a difficult exam. Running away from a burning house. Fighting an attacker.
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What is the overall function of the Parasympathetic Nervous System regarding energy?
It is restorative to conserve energy ('rest and digest' activities) when the body is at rest, especially after eating.
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What are the five specific actions listed that are controlled by the Parasympathetic division?
Salivation. Lacrimation (tearing). Urination. Digestion. Defecation.
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Which specific organs are the exceptions to reciprocal innervation, having ONLY Sympathetic innervation?
Sweat glands. Adrenal medulla. Blood vessels.
204
What analogy is used to describe the reciprocal activation of the two ANS divisions?
Driving a car: The Parasympathetic division acts as the brake, and the Sympathetic division acts as the accelerator.
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Which two muscles of the iris reciprocally control the size of the pupil?
The dilator (or radial) muscle. The constrictor (or sphincter) muscle.
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Which iris muscle is controlled by the Sympathetic division?
The dilator (radial) muscle.
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What specific receptor mediates the Sympathetic control of the pupil?
Alpha-1 (a1) receptors.
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Describe the mechanism and result of Sympathetic activation in the iris.
Increased Norepinephrine release activates alpha-1 receptors, causing contraction of the radial muscle. This leads to dilation of the pupil (also called Mydriasis).
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Under which light condition is the Sympathetic pupil response active?
Dim light.
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Which iris muscle is controlled by the Parasympathetic division?
The constrictor (sphincter) muscle.
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What specific receptor mediates the Parasympathetic control of the pupil?
Muscarinic (mAChR) receptors
212
Describe the mechanism and result of Parasympathetic activation in the iris.
Increased ACh release activates muscarinic receptors, causing contraction of the sphincter muscle. This leads to constriction of the pupil (also called Miosis).
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Under which light condition is the Parasympathetic pupil response active?
Bright light
214
What are the two characteristic symptoms of Horner syndrome mentioned in the text?
Decreased pupil size (called miosis). Decreased sweating (called anhidrosis).
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Which division of the ANS is defective in Horner syndrome?
The Sympathetic division.
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What are the two reasons (based on symptoms) that confirm the Sympathetic division is defective in Horner syndrome?
Sweat glands are only innervated by the sympathetic division (explaining the lack of sweating). Loss of sympathetic control (dilation) leads to abnormal constriction (due to unopposed parasympathetic tone).
217
What typically causes the nerve damage associated with Horner syndrome?
Damage to nerves traveling from the brain to the eyes/face, normally due to stroke, tumor, or spinal cord injury.
218
What are the three muscles involved in micturition (emptying of the bladder)?
The external sphincter. The internal sphincter. The detrusor muscle.
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What type of muscle is the external sphincter composed of, and what type of control is it under?
It is composed of skeletal muscle and is under voluntary control.
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What specific receptor mediates the voluntary control of the external sphincter (according to the table on Slide 28)?
Nicotinic (N) receptor.
221
What type of muscle are the internal sphincter and detrusor muscle composed of?
Smooth muscle.
222
Where does the sympathetic innervation of the detrusor and internal sphincter muscles originate?
In the lumbar spinal cord (L1-L3).
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Where does the parasympathetic innervation of the bladder muscles originate?
In the sacral spinal cord (S2-S4).
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Which division of the ANS predominates during the Filling of Bladder?
The Sympathetic control predominates.
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During bladder filling, what is the state of the Detrusor muscle and which receptor mediates this?
State: Relaxed. Receptor: Beta-2 (B2) receptor.
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During bladder filling, what is the state of the Internal sphincter and which receptor mediates this?
State: Contracted. Receptor: Alpha-1 (a1) receptor.
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What triggers the Micturition reflex (emptying)?
When the bladder is full, the fullness is sensed by mechanoreceptors in the bladder wall.
228
Where is the micturition reflex coordinated in the brain?
In centers in the Pons (brain stem).
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Which division of the ANS predominates during the Emptying of Bladder?
The Parasympathetic control predominates.
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: During bladder emptying, what is the state of the Detrusor muscle and which receptor mediates this (according to the table)?
State: Contracted. Receptor: Muscarinic (M) receptor.
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During bladder emptying, what is the state of the Internal sphincter and which receptor mediates this (according to the table)?
State: Relaxed.Receptor: Muscarinic (M) receptor.
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Summarize the reciprocal actions of the ANS on bladder structures:
Sympathetic: Dominates for bladder filling (relaxes detrusor, contracts internal sphincter). Parasympathetic: Dominates for bladder emptying (contracts detrusor, relaxes internal sphincter).
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Why do the sympathetic and parasympathetic divisions need to be regulated by autonomic centers?
To balance their competing influences and maintain homeostasis.
234
In which two specific brain structures are the autonomic centers located?
Hypothalamus Brain stem.
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What are the three specific functions controlled by centers in the Hypothalamus?
Body temperature (Temperature regulation). Food intake. Water balance (Thirst).
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What are the three primary physiological functions regulated by centers in the Brain stem?
Micturition (urination). Breathing (Respiratory/Pneumotaxic centers). Cardiovascular function (Vasomotor center).
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Besides the primary functions, what three specific reflex actions are regulated by centers in the Brain stem?
Swallowing Coughing Vomiting.
238
What is the term for the negative feedback mechanism normally used by autonomic centers to control organs?
Servomechanism.
239
Which specific autonomic center is used as the example for this mechanism in the text?
The vasomotor center (in blood pressure regulation).
240
Where specifically is the vasomotor center located?
In the medulla oblongata.
241
From where does the vasomotor center receive information about blood pressure?
From baroreceptors located in the: Carotid sinus. Aortic arch
242
According to the diagram on Slide 30, which nerves carry the sensory information from the baroreceptors to the brain?
Glossopharyngeal nerve (from Carotid sinus). Vagus nerve (from Aortic arch).
243
What does the vasomotor center do with the incoming blood pressure information?
It compares this information to a blood pressure set point in the medulla.
244
If blood pressure corrections are necessary, what outputs does the vasomotor center orchestrate?
It changes the output of both the sympathetic and the parasympathetic innervation.
245
Which organs are the targets of this sympathetic and parasympathetic regulation to adjust blood pressure?
The heart. Blood vessels.
246
According to the diagram, which nerve carries the parasympathetic output to the heart?
The Vagus nerve
247
According to the diagram, which structures carry the sympathetic output?
Sympathetic chain. Sympathetic nerves.
248
What defines homeothermic animals?
They maintain a relatively constant temperature in the face of fluctuating environmental temperatures [
249
How does the body adjust when environmental temperature decreases?
By reducing heat loss and increasing heat production
250
How does the body adjust when environmental temperature rises?
By increasing heat loss and reducing heat production
251
Where are the receptors located that provide information about external temperature?
Thermoreceptors in the skin (Cutaneous thermoreceptors)
252
Where are the receptors located that monitor internal temperature?
Central thermoreceptive neurons in the hypothalamus
253
What specifically do central thermoreceptors monitor?
The temperature of the blood
254
In the servomechanism of temperature regulation, what triggers the restorative responses?
Error signals, which represent a deviation from the set point
255
According to the diagram on Slide 31, what are the three effector mechanisms used for temperature regulation?
Sudomotor (sweating).Vasomotor.Metabolic
256
What is fever characterized by?
An elevation of body temperature above the normal range (around 36 degrees Celsius)
257
What are the agents that induce most common fevers called?
Pyrogens (e.g., bacterial endotoxin, bacterial debris, or mechanical tissue trauma)
258
What is the specific mechanism by which pyrogens cause fever?
They increase the temperature regulation set point in the hypothalamus
259
What physiological responses occur due to the increased set point during a fever?
Increased heat production by shivering. Heat conservation by cutaneous vasoconstriction
260
How is food intake regulated via a servomechanism?
Glucoreceptors in the hypothalamus sense blood glucose levels to control intake
261
How is water intake regulated via a servomechanism?
Osmoreceptors in the brain detect increases in the osmotic pressure (osmolality) of extracellular fluid
262
What three factors determine the final physiologic responses of effector organs?
The type of transmitters. The type of receptors. The locations.
263
How is Diversity demonstrated regarding transmitters?
Different transmitters mediate different functions. For example, the same effector cells may respond differently depending on whether they receive cholinergic or adrenergic input.
264
How is Diversity demonstrated regarding receptors?
Different receptors mediate different functions. For example, the same effector cells (like smooth muscle) may either contract or relax when receiving adrenergic input, depending on the specific type of adrenergic receptor present.
265
How is Specificity defined in the context of ANS function?
It refers to instances where there is the same transmitter and the same receptor (and activation mechanism), but the physiologic response is different.
266
Specificity is typically defined by what two factors?
It is tissue-specific and cell type-specific.
267
Specificity Example: What is the effect of Beta-1 (B1) receptor activation in the Sinoatrial (SA) node?
Increased heart rate.
268
What is the effect of Beta-1 (B1) receptor activation in the Atrioventricular (AV) node?
Increased conduction velocity
269
What is the effect of Beta-1 (B1) receptor activation in the Ventricular muscle?
Increased contractility.
270
What is the effect of Beta-1 (B1) receptor activation in the Salivary gland?
Increased secretion.
271
What is the effect of Beta-1 (B1) receptor activation in the Kidney?
Increased renin secretion.
272
What is the specific effect of Parasympathetic stimulation (via M receptors) on the Heart's contractility?
It decreases contractility, but specifically in the atria only
273
regarding Vascular Smooth Muscle, what unique effect does the Parasympathetic system have on the Endothelium?
It releases EDRF (Endothelium-derived relaxing factor), also known as NO (Nitric Oxide).
274
What is the effect of Parasympathetic stimulation (via M receptors) on the Bronchioles?
Constriction.
275
Compare the Sympathetic and Parasympathetic effects on the Walls of the Gastrointestinal Tract.
Sympathetic (Beta-2): Relaxes. Parasympathetic (M): Contracts.
276
What are the effects of Parasympathetic stimulation on Gastric and Pancreatic secretions?
It increases both gastric acid secretion and pancreatic secretion.
277
What are the specific roles of the ANS divisions in Male Genitalia function?
Sympathetic (Alpha): Causes Ejaculation. Parasympathetic (M): Causes Erection
278
What is the effect of the ANS on the Ciliary Muscle of the eye (involved in focus)?
Sympathetic (Beta-2): Dilates (relax) for Far vision. Parasympathetic (M): Contracts for Near vision
279
How does the receptor involved in sweating differ based on the type of sweating (Thermoregulatory vs. Stress)?
Thermoregulatory: Uses Muscarinic (M) receptors (Sympathetic Cholinergic). Stress: Uses Alpha-1 receptors.
280
What specific metabolic actions does the Sympathetic division trigger in the Liver?
Gluconeogenesis and Glycogenolysis
281
Which receptors mediate the Sympathetic metabolic effects in the Liver?
Alpha-1 and Beta-2 receptors
