Autonomic nervous system

Question 1

What is the purpose of the autonomic nervous system?

Answer 1

Maintaining homeostasis and survival

Question 2

Which tissue types does the CNS innervate?

Answer 2

Everything except the CNS tissue and skeletal muscle

Question 3

What are the three divisions of the ANS?

Answer 3

Sympathetic NS

Parasympathetic NS

Enteric NS

Question 4

Describe the general pattern of innervation of the sympathetic and parasympathetic NS?

Answer 4

Most organs are innervated by both sympathetic and parasympathetic nerves, but each system usually innervates different tissues.

Question 5

Which spinal cord segments are the sympathetic and parasympathetic nerves derived from?

Answer 5

Sympathetic: thoraco-lumbar

Parasympathetic: cranio-sacral

Question 6

Where in the spinal cord do autonomic pathways NOT originate from?

Answer 6

Cervical or lumbar enlargements

Question 7

Why don’t autonomic pathways originate from cervical or lumbar enlargements?

Answer 7

Upper and lower limb nerves originate from here

Question 8

Describe the location of sympathetic and parasympathetic ganglia?

Answer 8

Sympathetic ganglia are more distant from organs

Parasympathetic ganglia are closer to or within organs

Question 9

What are the two divisions of sympathetic ganglia?

Answer 9

Prevertebral ganglia

Paravertebral ganglia

Question 10

Describe the general organisation of sympathetic and parasympathetic nerves (in terms of strucutre, ganglia, etc.)?

Answer 10

Sympathetic: short preganglionic, long postganglionic fibres

Parasympathetic: long preganglionic, short postganglionic fibres

Preganglioinc fibres are lightly myelinated or unmyelinated, whereas all postganglionic fibres are unmyelinated

Question 11

Which NTs are used by sympathetic and parasympathetic nerves?

Answer 11

Question 12

What are non-classical transmitters?

Give some examples?

Answer 12

NTs that are not Ach or NA

aka ‘non-adrenergic, non-cholinergic’

eg. NO, ATP, NPY

Question 13

What is co-transmission?

Answer 13

More than one NT can be released at one time

Question 14

How does the ANS differ from the CNS in terms of the primary transmitters?

Answer 14

ANS: Ach and NA

CNS: glutamate and GABA

Question 15

Describe the junctions of ANS nerves and their target organs?

Answer 15

No easily visible junction

More than one transmitter release site per axon

Extra-junctional receptors present

Question 16

Where are sympathetic preganglionic neurons found?

Answer 16

Interomediolateral cell column of spinal cord

Question 17

Where are sympathetic postganglionic neurons located?

Answer 17

Two locations and functional classes:

Paravertebral

Prevertebral

Question 18

What is the function of sympathetic ganglia?

Answer 18

Essential for integration and coordination of sympathetic control between organs/tissues

Question 19

What are the functions of paravertebral and prevertebral sympatheitc ganglia?

Answer 19

Paravertebral: primary source of vasoconstrictor neurons

Prevertebral: primary source of neurons innervating non-vascular smooth muscle

Question 20

Describe the concept of convergence and divergence of sympathetic postganglionic neurons?

Answer 20

Convergence: particularly prevertebral ganglion neurons integrate signals from multiple inputs

Divergence: up to 200 ganglion neurons can be activated by one preganglionic neuron

Question 21

Why is divergence in postganglionic neurons important?

Answer 21

Allows coordination of effects in many tissues at once

Question 22

What is the major function of the sympathetic nervous system?

Answer 22

‘Fight or flight’ functions

Also activation of adrenal gland > release A and NA, broad activation of adrenoceptors

Question 23

List the three nuclei in the cranial component of preganglionic parasympathetic neurons?

Answer 23

Edinger-Westphal nucleus

Salivatory nuclei

Dorsal motor nucleus of vagus and nucleus ambiguus

Question 24

Where are the sacral preganglionic parasympathetic neurons located?

Answer 24

Sacral spinal cord

Question 25

Describe the special features of autonomic supply to the pelvic organs?

Answer 25

Project in pelvic splanchnic nerves to pelvic ganglia (pelvic plexus) Extensions of this plexus lie close to or within pelvic organs Many of the PS ganglion neurons have unusually long axons Also contain many sympathetic neurons: mixed ganglia

Question 26

What is the function of the parasympathetic nervous system?

Answer 26

'Rest and digest' functions

Question 27

Do the sympathetic and parasympathetic nervous systems always act antagonistically?

Answer 27

No There are very few cases when the two systems are genuinely antagonistic at the cellular level More commonly, actions are on different tissues to cause different types of actions

Question 28

Give examples of situations when the sympathetic and parasympathetic nervous systems are not acting genuinely antagonistically?

Answer 28

Question 29

What is the best way to distinguish between the sympathetic and parasympathetic nerves?

Answer 29

Anatomically: location of preganglionic neurons Sympathetic: thoracic, lumbar spinal cord Parasympathetic: cranial nuclei, sacral spinal cord

Question 30

Describe a typical autonomic reflex?

Answer 30

Visceral afferent neurons provide input to local interneurons and projection neurons Most autonomic reflexes are supraspinal, and involve brain input Output to periphery via autonomic ganglion

Question 31

Describe the nucleus of the solitary tract?

Answer 31

Caudal part located in medulla Major integrative centre for autonomic function Second order sensory neurons

Question 32

Describe the inputs and outputs of the nucelus of the solitary tract?

Answer 32

Input: visceral afferents Output: 1. feedback to local reflexes that control organ function; or 2. provide info to higher centres to drive more complex responses

Question 33

Why is the hypothalamus important in the ANS?

Answer 33

Most importnant brain region for coordination of autonomic output

Question 34

What are the inputs to the hypothalamus?

Answer 34

Sensory pathways Intrinsic sensory stuctures Circularting hormones

Question 35

What is the major role of the hypothalamus in the ANS?

Answer 35

Compares situation to biological set points, and adjusts behaviour and autonomic function if necessary

Question 36

What does the hypothalamus integrate with to determine its output?

Answer 36

Higher cortical and limbic systems