ANS Revision

Question 1

In the autonomic nervous system (ANS), nerve fibers that connect the central nervous system to ganglia are known as ___?

Answer 1

Preganglionic fibres

Question 2

All preganglionic fibres of the ANS are cholinergic. What 2 features does this mean they have?

Answer 2

• They use acetylcholine as their neurotransmitter
• They are myelinated for faster transmission

Question 3

Differences between sympathetic and parasympatheic preganglionic fibers regarding a) length b) number of synapses

Answer 3

a) sympathetic preganglionic fibers tend to be shorter than parasympathetic fibers
b) sympathetic fibers tend to form more synapses than parasympathetic fibers

Question 4

The parasympathetic division (craniosacral outflow) consists of cell bodies from one of two locations. What are these?

Answer 4

1. Brainstem (cranial nerves III, IV, IX and X)
2. Sarcal spinal cord (S2, S3 and S4)

Question 5

Location of cell bodies of the sympathetic divison (thoracolumbar outflow)? What type of cell bodies are these?

Answer 5

• In the lateral horn of the spinal cord (intermediolateral cell columns) from T1 to L2.
• These cell bodies are GVE (general visceral efferent) neurons and are the preganglionic neurons

Question 6

Define ‘cholinergic’

Answer 6

Pertaining to, activated by, producing, or having the same function as acetylcholine

Question 7

Define ‘postsynaptic neuron’

Answer 7

The nerve cell that bears receptors for neurotransmitters released into the synaptic cleft by the presynaptic neuron.

Question 8

Define ‘preganglionic fibre’

Answer 8

In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers.

Question 9

Define ‘ganglion’

Answer 9

A cluster of interconnecting nerve cells outside the brain.

Question 10

Define ‘preganglionic neuron’

Answer 10

The nerve fibers that supply a ganglion.

Question 11

What do all preganglionic fibres of the ANS use as their neurotransmitter?

Answer 11

Acetylcholine

Question 12

Are all preganglionic fibres of the ANS myelinated or unmyelinated?

Answer 12

Myelinated

Question 13

How many neurons are involved in the efferent pathways of the ANS?

Answer 13

2; the preganglionic neuron must first cross a synapse onto a postganglionic neuron before innervating the target organ

Question 14

Why do sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers?

Answer 14

Because sympathetic ganglia are often closer to the spinal cord while parasympathetic preganglionic fibers tend to project to and synapse with the postganglionic fiber close to the target organ.

Question 15

Spinal cord exit point of sympathetic division of ANS vs parasympathetic division?

Answer 15

SNS: thoracolumbar outflow (T1-L2)

PSNS: craniosacral outflow (CN III, VII, IX, X, S2-S4)

Question 16

There are several locations where preganglionic neurons of the sympathetic NS create synapses with their postganglionic neurons. What are the 3 main locations?

Answer 16

1. The paravertebral ganglia of the sympathetic chain –> these run either side of the vertebral bodies;
   
   1. Cervical ganglia
   2. Thoracic ganglia
   3. Rostral lumbar ganglia
   4. Caudal lumbar ganglia
   5. Pelvic ganglia
2. The prevertebral ganglia –> lie between the paravertebral ganglia and their target organ;
   
   1. Celiac ganglion
   2. Aorticorenal ganglion
   3. Superior mesenteric ganglion
   4. Inferior mesenteric ganglion
3. The chromaffin cells of the adrenal medulla –> This is the one exception to the two-neuron pathway rule as they create a synapse directly onto the target cell bodies.

Question 17

What are the 6 main locations where the preganglionic neurons synapse with the postganglionic neurons of the parasympathetic nervous system?

Answer 17

Parasympathetic ganglia of the head:

1. Ciliary (CN III)
2. Submandibular (CN VII)
3. Pterygopalatine (CN VII).
4. Otic (CN IX).
5. In or near the wall of an organ innervated by the vagus (CN X)
6. In or near the wall of an organ innervated by the sacral nerves (S2, S3, S4).

Question 18

Define ‘divergence’ regarding neurons

Answer 18

the number of postsynaptic fibers a single preganglionic fiber creates a synapse with

Question 19

Divergence factor of parasympathetic division vs in the sympathetic division

Answer 19

Para –> 1:4

Symp –> 1:20

Question 20

What is a dorsal root ganglion?

Answer 20

A nodule on a dorsal root of the spine that contains the cell bodies of nerve cells that carry signals from sensory organs to the appropriate integration center.

Question 21

Which division of the ANS is responsible for the fight-or-flight response?

Answer 21

Sympathetic - sympathetic ganglia deliver information to the body about stress and impending danger,

Question 22

Where are sympathetic ganglia located?

Answer 22

located close to and on either side of the spinal cord in long chains

Question 23

What are the axons of dorsal root ganglion neurons known as?

Answer 23

Afferents

Question 24

In the PNS, what do ‘afferents’ refer to?

Answer 24

axons that relay sensory information into the central nervous system (i.e., the brain and the spinal cord)

Question 25

Define 'sympathetic ganglion'

Answer 25

The ganglia of the sympathetic nervous system. They deliver information to the body about stress and impending danger, and are responsible for the familiar fight-or-flight response.

Question 26

Define 'parasympathetic ganglion'

Answer 26

The autonomic ganglia of the parasympathetic nervous system. Most are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate.

Question 27

What are 'autonomic ganglia'

Answer 27

* Can be classified as either sympathetic ganglia and parasympathetic ganglia * Clusters of neuron cell bodies that transmit signals from the periphery to the integration centers in the CNS/from the CNS to the periphery \ I.e. They are essentially a **junction** between **autonomic** **nerves** originating from the **CNS** and **autonomic** **nerves** innervating their **target** **organs** in the periphery.

Question 28

Where do the dorsal root ganglia develop from in the embryo?

Answer 28

From neural crest cells, NOT neural tube --\> can be regarded as gray matter of the spinal cord that became translocated to the periphery

Question 29

Is the ciliary ganglion sympathetic or parasympathetic?

Answer 29

Parasympathetic

Question 30

Function of ciliary ganglion?

Answer 30

Involved in pupil constriction and accommodation

Question 31

What are the 4 parasympathetic ganglia of the head and neck?

Answer 31

1. Ciliary 2. Pterygopalatine 3. Otic 4. Submandibular

Question 32

What type of neurons are dorsal root ganglion neurons?

Answer 32

Pseudo-unipolar --\> they have an axon with two branches that act as a single axon; a distal process and a proximal process

Question 33

How does an action potential pass along a dorsal root ganglion neuron?

Answer 33

Unlike the majority of neurons found in the CNS, an action potential in a dorsal root ganglion neuron may initiate in the **distal** **process** in the **periphery**, bypass the cell body, and continue to propagate along the proximal process until reaching the **synaptic** **terminal** in the **dorsal** **horn** of the spinal cord

Question 34

The distal section of the axon of the dorsal root ganglion neuron may be 1 of 2 types. What are these 2 types?

Answer 34

1. Bare nerve ending 2. Encapsulated by a structure that helps relay specific information to a nerve.

Question 35

The nerve endings of dorsal root ganglion neurons have a variety of sensory receptors. What are these activated by?

Answer 35

mechanical, thermal, chemical, and noxious stimuli

Question 36

A Meissner’s corpuscle or Pacinian corpuscle may encapsulate the dorsal root ganglion nerve ending. What are these sensitive to?

Answer 36

Mechanical stimulation, such as stroking or vibration, respectively

Question 37

What is a neuroblastoma?

Answer 37

A cancer that develops from immature nerve cells found in several areas of the body

Question 38

Which tissue do neuroblastoma tumors arise from?

Answer 38

Sympathetic ganglia

Question 39

What are the bilateral symmetric sympathetic chain ganglia also called?

Answer 39

Paravertebral ganglia

Question 40

Where are paravertebral ganglia located?

Answer 40

Located just **ventral** and **lateral** to the spinal cord. The chain extends from the **upper** **neck** down to the **coccyx** (forming the unpaired coccygeal ganglion).

Question 41

Regarding the paravertebral sympathetic ganglia; a) where do the preganglionic nerves from the spinal cord create a synapse? b) where do the postganglionic fibres extend to?

Answer 41

a) create a synapse end at one of the chain ganglia b) extends to an effector (typically a visceral organ in the thoracic cavity)

Question 42

How many pairs of paravertebral ganglia are there?

Answer 42

There are usually 21 or 23 pairs of these ganglia: three in the cervical region, 12 in the thoracic region, four in the lumbar region, four in the sacral region and a single, unpaired ganglion lying in front of the coccyx called the ganglion impar.

Question 43

What are pervertebral ganglia also called?

Answer 43

Collateral ganglia

Question 44

Which nerves do the prevertebral ganglia receive input from?

Answer 44

Receive input from the **splanchnic** **nerves** and innervate organs of the abdominal and pelvic region.

Question 45

What are the 4 main prevertebral ganglia?

Answer 45

1. celiac ganglia 2. aortic–renal ganglia 3. superior mesenteric ganglia 4. inferior mesenteric ganglia.

Question 46

Most parasympathetic ganglia are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. What are the 4 exceptions to this?

Answer 46

The four paired parasympathetic ganglia of the head and neck; ciliary, pterygopalatine, otic, submandibular

Question 47

Describe the 2 neuron pathway of efferent parasympathetic nerves

Answer 47

*Preganglionic:* * Its cell body sits in the CNS * Its axon usually extends to a ganglion somewhere else in the body, where it synapses with the dendrites of the second neuron in the chain. * Postganglion:* * The axons extend from the CNS into a ganglion that is either very close to or embedded in their target organ.

Question 48

In the autonomic nervous system, fibers from the ganglion to the effector organ are called \_\_\_?

Answer 48

Postganglionic fibres

Question 49

Postganglionic fibers in the sympathetic division are adrenergic. What does this mean?

Answer 49

Use **noradrenaline** as their neurotransmitter

Question 50

Compare the **postganglionic** fibres of the SNS and PSNS

Answer 50

SNS: * Adrenergic * Noradrenaline as neurotransmitter PSNS: * Cholinergic * Acetylcholine as neurotransmitter

Question 51

Postganglionic fibers in the sympathetic division are adrenergic. What is the one exception to this?

Answer 51

The postganglionic neurons of sweat glands

Question 52

What neurotransmitter do the postganglionic neurons of sweat glands release? Why?

Answer 52

Release **acetylcholine** for the activation of **muscarinic** receptors.

Question 53

What are chromaffin cells of the adrenal medulla analogous to?

Answer 53

Post-ganglionic neurons (the adrenal medulla develops in tandem with the sympathetic nervous system and acts as a modified sympathetic ganglion)

Question 54

In the sympathic nervous system, presynaptic nerves' axons terminate in which 3 locations?

Answer 54

1. Prevertebral ganglia 2. Paravertebral ganglia 3. Adrenal medulla

Question 55

Define adrenergic

Answer 55

Containing or releasing adrenaline.

Question 56

At the synapses within the ganglia, the preganglionic neurons of the SNS release what? Onto what receptors?

Answer 56

Release **acetylcholine**, a neurotransmitter that activates **nicotinic** **acetylcholine** receptors on postganglionic neurons.

Question 57

In response to ACh, what do postganglionic neurons of the SNS release? What receptors does this activate on peripheral target tissues?

Answer 57

Release **noradrenaline** --\> activates **adrenergic** receptors on the peripheral target tissues. The activation of target tissue receptors causes the effects associated with the sympathetic system.

Question 58

In response to ACh, postganglionic neurons of the SNS release noradrenaline. What are the 2 exceptions to this?

Answer 58

* The postganglionic neurons of **_sweat glands_** * The chromaffin cells of the **_adrenal medulla_**

Question 59

What do the postganglionic neurons of sweat glands release?

Answer 59

acetylcholine for the activation of muscarinic receptors

Question 60

Within the adrenal medulla (an endocrine gland), the pre-ganglionic neurons create synapses with chromaffin cells and stimulate the chromaffin cells to release what?

Answer 60

Adrenaline and noradrenaline directly into the blood

Question 61

Whether synapsing in them or not, all presynaptic axons of the SNS enter the paravertebral ganglion. At what level do they enter?

Answer 61

The axon enters the paravertebral ganglion at the level of its originating spinal nerve.

Question 62

After the presynaptic nerve axon of the SNS enters the paravertebral ganglion, what are its 4 options?

Answer 62

1. create a synapse in this ganglion 2. ascend to a more superior paravertebral ganglion and synapse there 3. descend to a more inferior paravertebral ganglion and synapse there 4. **pass** **through** to a prevertebral ganglion and synapse there

Question 63

Why are presynaptic neurons of the SNS generally much shorter than their postsynaptic counterparts?

Answer 63

Because paravertebral and prevertebral ganglia are relatively close to the spinal cord, presynaptic neurons are generally much shorter than their postsynaptic counterparts, which must extend throughout the body to reach their destinations.

Question 64

In the cranium, **preganglionic** fibers of the parasympathetic NS (cranial nerves III, VII, and IX) usually arise from specific nuclei in the CNS. Where do they create a synapse?

Answer 64

Create a synapse at one of four parasympathetic ganglia of the head: ciliary, pterygopalatine, otic, or submandibular.

Question 65

From these four parasympathetic ganglia of the head, how do the the postsynaptic fibers complete their journey to target tissues?

Answer 65

Via cranial nerve V (trigeminal)

Question 66

Which parasympathetic cranial nerve does NOT participate in the parasympathetic ganglia of the head? Why?

Answer 66

Vagus nerve (CN X) --\> as most of its fibers are destined for a broad array of ganglia on or near the thoracic viscera (esophagus, trachea, heart, lungs) and the abdominal viscera (stomach, pancreas, liver, kidneys).

Question 67

Where do the **pelvic splanchnic** **efferent** preganglionic nerve cell bodies reside?

Answer 67

In the **lateral grey horn** of the spinal cord at the S2-S4 spinal levels.

Question 68

Where do the pelvic splanchnic efferent preganglionic nerve axons synapse?

Answer 68

Their axons continue away from the CNS to synapse at an autonomic ganglion close to the organ of innervation.

Question 69

How do synapses between pre- and post-ganglionic efferent nerves differ between SNS and PSNS?

Answer 69

SNS: synapses between pre- and post-ganglionic efferent nerves in general occur at ganglia that are farther away from the target organ. PSNS: synapse at an autonomic ganglion close to the organ of innervation

Question 70

What 2 types of receptors can ACh act on?

Answer 70

1. muscarinic cholinergic receptors 2. nicotinic cholinergic receptors

Question 71

When stimulated, the **parasympathetic** preganglionic nerve releases what? What does this act on?

Answer 71

releases ACh at the ganglion, which acts on the **nicotinic** receptors of the postganglionic neurons

Question 72

When stimulated, what does the **parasympathetic** postganglionic fibre release? What does this act on?

Answer 72

releases ACh to stimulate the muscarinic receptors of the target organ.

Question 73

Location of muscarinic vs nicotinic receptors?

Answer 73

Muscarinic receptors predominate at higher levels of the central nervous system, while nicotinic receptors, which are much faster acting, are more prevalent at neurons of the spinal cord and at neuromuscular junctions in skeletal muscle.

Question 74

How does an autonomic plexus differ from an autonomic ganglion?

Answer 74

Ganglion: cluster of nerve cell bodies, either sympathetic or parasympathetic Plexus: formed from **sympathetic** and **parasympathetic** fibers that innervate and regulate the overall activity of visceral organs

Question 75

What are the 5 autonomic plexuses?

Answer 75

1. Cardiac plexus 2. Pulmonary plexus 3. Oesophageal plexus 4. Abdonimal aortic plexus 5. Superior and inferior hypogastric plexuses

Question 76

What are autonomic plexuses formed from?

Answer 76

Autonomic plexuses are formed from **sympathetic** **postganglionic** axons, **parasympathetic** **preganglionic** axons, and some **visceral** **sensory** axons.

Question 77

What do autonomic plexuses provide?

Answer 77

Plexuses provide a **complex** **innervation** pattern to the target organs, since most organs are innervated by both divisions of the autonomic nervous system.

Question 78

What fibres form the pulmonary plexus?

Answer 78

The pulmonary plexus is an autonomic plexus formed from pulmonary branches of **vagus** **nerve** and the **sympathetic** **trunk**.

Question 79

What type of parasympathetic fibres form autonomic plexuses? Sympathetic fibres? Visceral fibres?

Answer 79

Parasympathetic --\> preganglionic Sympathetic --\> postganglionic Visceral --\> sensory

Question 80

Do the different fibres (e.g. para, symp, visceral) of the autonomic plexuses interact or synpase together?

Answer 80

The nerves in the each plexus are close to each other but typically do not interact or synpase together.

Question 81

What is the cardiac plexus?

Answer 81

The cardiac plexus is an autonomic plexus of nerves situated at the base of the heart that innervates the heart.

Question 82

Each parasympathetic **ganglion** has 3 roots. What are these?

Answer 82

1. a motor root 2. a sympathetic root 3. a sensory root

Question 83

What is the 'lacrimal gland'

Answer 83

One of a pair almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film.

Question 84

How does a sympathetic fibre pass through a parasympathetic autonomic ganglion?

Answer 84

Postsynaptic sympathetic fibers that **traverse** the ganglion **without crossing a synapse**.

Question 85

Describe the sympathetic root in the parasympathetic ganglion

Answer 85

This carries postsynaptic sympathetic fibers that traverse the ganglion without crossing a synapse.

Question 86

Describe the motor root of the parasympathetic ganglion

Answer 86

This carries **presynaptic** **parasympathetic** nerve fibers that **terminate** in the ganglion and create **synapses** for the postsynaptic fibers to travel to their target organs.

Question 87

Describe the sensory root of the parasympathetic ganglion

Answer 87

The **proximal** end of a **dorsal** **afferent** **nerve** that is attached to the spinal cord.

Question 88

Most parasympathetic ganglia are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. What are the exceptions to this?

Answer 88

The exceptions are the four paired parasympathetic ganglia of the head and neck.

Question 89

What parasympathetic innervation does the ciliary ganglion supply?

Answer 89

spincter pupillae, ciliary muscle

Question 90

What parasympathetic innervation does the pterygopalatine ganglion supply?

Answer 90

lacrimal gland, glands of nasal cavity

Question 91

What parasympathetic innervation does the submandibular ganglion supply?

Answer 91

submandibular and sublingual glands

Question 92

What parasympathetic innervation does the otic ganglion supply?

Answer 92

parotid

Question 93

Each parasympathetic ganglia of the head has three roots entering the ganglion (motor, sympathetic, and sensory roots) and a variable number of exiting branches. Describe these 3 roots

Answer 93

1. The **_motor root_** carries **presynaptic** parasympathetic nerve fibers (**general** **visceral** **efferent** fibers) that terminate in the ganglion by creating a synapse for the postsynaptic fibers traveling to target organs. 2. The **_sympathetic root_** carries **postsynaptic** sympathetic fibers (**general** **visceral** **efferent** fibers) that traverse the ganglion **without** creating a synapse. 3. The _**sensory** **root**_ carries **general** **sensory** fibers (general **somatic** **afferent** fibers) that also **do** **not** create a synapse in the ganglion.

Question 94

What is a reflex arc? What are the 2 types?

Answer 94

A neural pathway that controls an action reflex. There are two types of reflex arcs: 1. the **autonomic** reflex arc that affects the inner organs 2. the **somatic** reflex arc that affects muscles

Question 95

Define somatic

Answer 95

Part of, or relating to, the body of an organism.

Question 96

Within the brain, where is the ANS located?

Answer 96

In the medulla oblongata

Question 97

What are the major ANS functions of the medulla?

Answer 97

respiration (the respiratory control center, or RCC), cardiac regulation (the cardiac control center, or CCC), vasomotor activity (the vasomotor center or VMC), and certain reflex actions (such as coughing, sneezing, vomiting and swallowing).