Unit 5: Chapter 13

Question 1

Glucose

Answer 1

Major fuel source for the NS
Neurons cant store, replies on blood glucose or glycogen stores for support of neuroglial cells

Question 2

Metabolic Requirements: Brain

Answer 2

Recieves 15-20% (750mL/min) total resting cardiac output
Consumes 20% of oxygen
Cannot store O2
Cannot engage in anaerobic metabolism

Question 3

Brain Cell Death

Answer 3

Begins within 4-6 mins
Unconsciousness occurs almost stimulatenously

Question 4

Action Potentials

Answer 4

Electrical impulses
How neurons communicate with other neurons
Transfers information from one location to another via the frequency and patten of the action potential

Question 5

Ion Channels

Answer 5

Contained in muslce and nerve cells that are excitable tissue.
Are responsible for generating action potentials

Question 6

Voltage gated Channels

Answer 6

Exist for Na, K, and Ca ions.
Each channel has a charactertisitc voltage at which it opens and closes.

Question 7

Ligand Gated channels

Answer 7

Respond to chemical messengers

Question 8

Mechanically gated channels

Answer 8

Respond to physical changes

Question 9

Light Gated Channels

Answer 9

Respond to flirtations in light levels

Question 10

Depolarization

Answer 10

Brings the membrane potential closer to the threshold so that a smaller tumulus is needed to cause the neuron to fire

Question 11

Hyperpolaization

Answer 11

Brings the membrane potential further from the threshold and has inhibitory effect decreasing hte likelihood that an action potential will be generated

Question 12

Action Potential Phase

Answer 12

1. Resting Or polarized state
2. Depolarization
3. Repolarization

Question 13

Action Potential Phase

Answer 13

1. Resting Or polarized state: -70 mV, not transmitting impulses
2. Depolarization: inward flow of pos ions (+30)
3. Repolarization: polarity of membrane is reestablished. Durning this stage, membrane remains refractory until 1/3 is complete. Last 0.4 to 4 ms.

Question 14

Absolute Refractory Period

Answer 14

During repolarization, the membrane remains refractory until repolarization is approximately one third complete.
lasts 0.4 to 4 ms
During the second part of the recovery period, the relative refractory period, the membrane can be excited by a stronger-than-normal stimulus.

Question 15

Messenger Molecules

Answer 15

include the neurotransmitters, neuromodulators, and neurotrophic or nerve growth factors.
The function of the NS relies on these chemical messengers.

Question 16

Neurotransmitters

Answer 16

chemical substances that excite, inhibit, or modify neuron response.
include amino acids, neuropeptides, and monoamines.
Nerouns comminucate through chemical synapses via neurotransmitters

Question 17

GABA

Answer 17

The amino acids glutamine, glycine, and gamma-aminobutyric acid (GABA) serve as neurotransmitters at most CNS synapses.
GABA mediates most synaptic inhibition in the CNS.

Question 18

Neuropeptides

Answer 18

Made up of 2 or more amino acids
Includes: endorphins, enkephalins
Involved in pain sensations and perception

Question 19

Synaptic Transmission

Answer 19

Neurons communicate through chemical synapses via neurotransmitters. Chemical synapses consist of a presynapse, a synaptic cleft, and a postsynapse. process relies on
(1) synthesis and release of a neurotransmitter from a presynaptic neuron
(2) binding of a neurotransmitter to receptors in the postsynaptic neuron
(3) neurotransmitter removal from the synapse.

Question 20

Synthesizes and Release of Neurotransmitters

Answer 20

Occurs in the cytoplasm of the axon terminal of the presynaptic neuron and stored in synaptic vesicles.
Nerve impulse is how 2 neurons communicate. This stimulates the presynapse neuron and movement of synaptic vesicles to the cell membrane.
Causes release of neurotransmitter into synaptic cleft

Question 21

Receptor Binding of neurotransmitters

Answer 21

Once released, neurotransmitter moves across the synaptic cleft, binds to receptors on the postsynaptic neuron.
The action of a neurotransmitter is determined by the type of receptor to which it binds.
Many presynaptic neurons also have receptors to which a neurotransmitter may bind.
The presynaptic receptors function in a negative feedback manner to inhibit further release of the neurotransmitter.

Question 22

Neurotransmitter Removal

Answer 22

Precise control of synaptic function relies on the rapid removal of the neurotransmitter from the synapse.
A released neurotransmitter can:
(1) be taken back up into the neuron in a process called reuptake
(2) diffuse out of the synaptic cleft
(3) be broken down by enzymes.

Question 23

Receptors

Answer 23

How neurotransmitters exert their actions through spefici proteins that are embedded in the Postsynaptic membrane.

Question 24

Dorsal Horn Cell Column

Answer 24

Four columns of afferent neurons in the dorsal root ganglia directly innervate four corresponding columns of IA neurons in the dorsal horn.
These columns are categorized as special and general afferents: special SA, general SA, special VA, and general VA

Question 25

Special SA Columns

Answer 25

fibers are concerned with internal sensory information such as joint and tendon sensation. Neurons in the special SIA column cells relay information to local reflexes concerned with posture and movement, to the cerebellum, contributing to coordination of movement, and to the forebrain, contributing to experience.

Question 26

General SA Columns

Answer 26

innervate the skin and other somatic structures and respond to stimuli such as those that produce pressure or pain. Relay the sensory information to protective and other reflex circuits and project the information to the forebrain, where it is perceived as painful, warm, cold, and the like.

Question 27

Special VA Columns

Answer 27

cells innervate specialized gut-related receptors, such as taste buds and olfactory mucosal receptors. Central processes communicate with special VIA column neurons that project to reflex circuits producing salivation, chewing, swallowing, and other responses. Forebrain projection fibers from these association cells provide sensations of taste and smell.

Question 28

General VA Columns

Answer 28

neurons innervate visceral structures such as the gastrointestinal tract, urinary bladder, and heart and great vessels. They project to the general VIA column, which relays information to vital reflex circuits and sends information to the forebrain regarding visceral sensations such as stomach fullness, bladder pressure, and sexual experience.

Question 29

Ventral Horn Cell Columns

Answer 29

contains three longitudinal cell columns: general visceral efferent, pharyngeal efferent, and general somatic efferent each contains OA and efferent neurons. OA neurons coordinate and integrate the function of efferent motor neurons of their column

Question 30

General Visceral Efferent

Answer 30

neurons transmit the efferent output of the ANS and are called preganglionic neurons. These neurons are structurally and functionally divided into sympathetic or parasympathetic nervous systems. Their axons project through segmental ventral roots to innervate smooth and cardiac muscle and glandular cells, most of which are in the viscera

Question 31

Pharyngeal Efferent

Answer 31

neurons innervate branchial arch skeletal muscles the muscles of mastication and facial expression and muscles of the pharynx and larynx. Pharyngeal efferent neurons also innervate muscles responsible for moving the head.

Question 32

General Somatic Efferent (or LMS)

Answer 32

neurons supply somite-derived muscles of the body and head, which include the skeletal muscles of the body and limbs, the tongue, and the extrinsic eye muscles. These efferent neurons transmit the commands of the CNS to peripheral effectors, the skeletal muscles. They are the “final common pathway neurons” in the sequence leading to motor activity. They are often called LMNs because they are under the control of higher levels of the CNS. LMNs have their cell bodies in the brain stem and spinal cord.

Question 33

Longitudinal Tracts: Gray Matter

Answer 33

The gray matter of the cell columns in the CNS is surrounded by bundles of myelinated axons and unmyelinated axons that travel longitudinally along the length of the neural axis.

Question 34

Longitudinal Tracts: White Matter

Answer 34

Divided into 3 layers: inner, middle and outer

Question 35

Whiter Matter: Inner Layer (Archilayer)

Answer 35

Contains short sobers that project for a maximum of approx. 5 segments before recentering the gray matter by collaterals (branches). Function: very slow, Felxor withdrawal reflex circuitry

Question 36

White Matter: Middle Layer (Paleolayer)

Answer 36

Projects to 6 or more segments. Have collaterals (branches) that enter the gray matter of interventions segments. Also contains suprasegmatal projections. Function: Fast, spinothalamic tracts

Question 37

White matter: Outer Layer (Neolayer)

Answer 37

Large diameter axons that can travel the entire length of the NS. Contains suprasegmetals projections that are higher levels of CNS (brain stem, cerebrum) Function: Fastest, corticospinal tracts

Question 38

Reflex

Answer 38

Respsone between a stimulus and an elicited motor reaction Consist of: afferent neuron, CNS interneurons and effector (motor) neuron. 2 types: withdrawal and myotatic reflex

Question 39

Withdrawal Reflex

Answer 39

stimulated by a damaging (nociceptive) stimulus and quickly moves the body part away from the offending stimulus, usually by flexing a limb part. Can also produce contraction of muslces other than the extremities

Question 40

Myotatic or Stretch Reflex

Answer 40

controls muscle tone and helps maintain posture. Sensory nerve terminals in skeletal muscles and tendons relay information on muscle stretch and joint tension to the CNS. This information is relayed to the thalamus and sensory cortex and is experienced as proprioception, the sense of body movement and position.

Question 41

Brain

Answer 41

Divided into 3 regions: Hindbrain: medulla Oblongata,pons, cerebellum Midbrain: 2 pairs of superior and inferior colliculi Forebrain: 2 hemispheres covered by the cerebral cortex. Contains masses of gray matter, basal ganglia, rostrum end of neural tube, Diencephalon, thalamus and hypothalamus

Question 42

Pons and Medulla

Answer 42

Contain reticular formation networks that control breathing, eating and locomotive fucntion.

Question 43

Midbrain

Answer 43

Higher level integration occurs here

Question 44

Vagus Nerve

Answer 44

X Sensory and motor components innervate the pharynx, gastrointestinal tract, heart, spleen, and lungs. Unilateral loss of vagal function can result in slowed gastrointestinal motility, a permanently husky voice, and uvula deviation away from the damaged side. Bilateral loss of vagal function can seriously damage reflex maintenance of cardiovascular and respiratory reflexes

Question 45

Thalamus

Answer 45

Dorsal horn part of the Diencephalon Consits of 2 large egg shaped masses on either side of 3rd ventricle. Relays critical information regarding motor activity to and from the selected motor cortex areas.

Question 46

Neural Circuits of the Thalamus

Answer 46

1. is the path from the cerebral cortex to the pons and cerebellum, the thalamus, and back to the motor cortex. 2. is the feedback circuit from the cortex to the basal ganglia to the thalamus and back to the cortex.

Question 47

Hypothalamus

Answer 47

Inferior to the thalamus Represent the ventral horn portion of the Diencephalon Boarder 3rd ventricle Includes: neurohypophysis(posterior pituitary) Master level integration of homeostatic control of the body’s internal enviroment via maintains of blood gas concentrations, water balance, food consumption and major aspects of endocrine and ANS control.

Question 48

Blood Brain Barrier

Answer 48

Maintain the stable chemical enviroment of the brain. Depends on unique characteristics of brain capillaries. Permits passage of esstail substances while excluding unwanted material. Water, CO2 and H2O can enter with ease.

Question 49

Blood Brain Barrier Funtion

Answer 49

Prevents large molecules (proteins, peptides) are excluded from crossing. Prevents many drugs from entering. Lipid soluble molecules cross with ease: alcohol, nicotine, heroin Trauma or infection alters permeability thus alters concentration of proteins, water and lytes.

Question 50

Blood-CSF Barrier

Answer 50

Formed by the ependymal cells covering the choroid plexus that are linked together by tight junctions between the blood plasma and CSF

Question 51

CSF

Answer 51

High sodium and low potassium content O2 and CO2 move in CSF via diffusion causing almost equal partial pressure of plasma. Due to high Na content, neg charged Cl and HCO3 diffuse into along ionic gradient. Bicarbonate is importnat for regulating pH.

Question 52

Areas of Brain that do Not Contain Blood-CSF Barrier

Answer 52

Caudal end of 4th ventricle where speciled receptors for the CSf CO2 level influence resp function Walls of 3rd ventricle, permit hypothalamic neurons to monitor blood glucose levels

Question 53

Catecholamines

Answer 53

Include: norepinephrine, epinephrine, dopamine Synthesized from tyrosine in sympathetic nerve terminal endings As they are synthesized , they are stored in vesicles Cause excitation or inhibition of smooth muscle contraction depending on the site, dose and type of receptor present.

Question 54

Epinephrine

Answer 54

80% of catecholamines Potent as both excitatory and inhibitor agent Released from the adrenal gland Syntheseized by the adrenal medulla is influenced by glucocorticoids secretion from the adrenal cortex. Transported through an intra-adrenal vascular network from the adrenal cortex to the adrenal medulla, where they cause the sympathetic neurons to increase their production of epinephrine through increased enzyme activity.

Question 55

Norepinephrine

Answer 55

50-80% that is released durning an action potential is actively taken back up by the action terminal This stops the action of the neurotransmitter and allows it to be reused Remaining diffuse into tissue where it is decreased by catecholamines-O-methyltransferase and MAO. Potential excitatory activity and low inhibitory agent

Question 56

a-Adrenergic Receptors

Answer 56

Subdivided into a1 and a2 A1: found primarily in Postsynaptic effectors sites, mediate responses in vascular smooth muscle contraction depending, mediate responses in vascular smooth muscle A2: mainly located presynaptic ally NS can inhibit release of norepinephrine from sympathetic nerve terminals. Are abundant int eh CNS ands are thought to influence the central control of BP.

Question 57

B-Adrenergic Receptors

Answer 57

Subdivided into B1 and B2 B1: Found in the heart Can be selectively blocked by B1 receptors blocking drugs B2: found int he bronchioles and other sites that have b-mediated functions

Question 58

Endogenous Neuromediators

Answer 58

Catecholamines produced in sympathetic nerve endings