The autonomic nervous system

Question 1

What is in the sensory part of the Peripheral Nervous System?

Answer 1

-somatic nervous system
-visceral nerves

Question 2

What does the somatic nervous system do?

Answer 2

Gathers information from skeletal muscle and skin

Question 3

What do the visceral nerves do?

Answer 3

Innervate the bladder +gastrointestinal tract

Question 4

What is an afferent nerve fibre/neuron?

Answer 4

Anything going from the sensory part to the CNS

Question 5

What makes up the CNS?

Answer 5

-brain
-spinal cord

Question 6

What is in the motor part of the peripheral nervous system?

Answer 6

-somatic nervous system
-autonomic nervous system

Question 7

What does the somatic nervous system do?

Answer 7

-involved in muscle contraction at skeletal muscle
-voluntary

Question 8

What does the autonomic nervous system do?

Answer 8

-involved in smooth muscle and cardiac muscle contraction
-involved in gland secretion
-involuntary

Question 9

What is an efferent nerve fibre/neuron?

Answer 9

Takes information from CNS into the periphery

Question 10

What are the 2 major efferent pathways in the autonomic nervous system?

Answer 10

-sympathetic nervous system
-parasympathetic nervous system

Question 11

When and how is the sympathetic nervous system activated?

Answer 11

when - exercise, excitement, emergency, embarrassment
how - co-ordinated, whole body response or discrete and organ specific

Question 12

How and when is the parasympathetic nervous system activated?

Answer 12

when - digestion, defecation, urination (diuresis)
how - discrete and organ specific

Question 13

What is stimulated by the parasympathetic nervous system?

Answer 13

-eyes
-heart –> decreases natural heart rate
-GI tract –> secretions + movement of smooth muscle
-bladder –> bladder wall relaxes + contraction of bladder sphincter
-reproductive organs

Question 14

What is stimulated by the sympathetic nervous system?

Answer 14

-eyes –> pupil dilation + eyelid contraction to increase visibility
-heart –> increased rate + force of contraction
-blood vessels –> b.v to areas that don’t need blood constrict + b.v to important areas relax to increase blood flow
-lungs –> dilation of bronchioles so more oxygen in and more carbon dioxide out
-liver –> synthesises and releases glucose for muscle contraction
-adrenal medulla –> releases insulin
-bladder –> smooth muscle relaxes to prevent urination
-reproductive system –> prevent orgasm

Question 15

How is the response from the 2 pathways of the autonomic nervous system balanced?

Answer 15

-generally innervate the same tissues but have opposing effects
-actions are antagonistic, but work synergistically
-allows for rapid, precise control of tissue function

Question 16

Where does mainly sympathetic innervation occur, rather than a balance between the 2 pathways?

Answer 16

-sweat glands
-hair follicles
-blood vessel smooth muscle
-adrenal medulla

Question 17

Describe preganglionic neurons

Answer 17

-always cholinergic fibres, so acetylcholine is its primary neurotransmitter
-acetylcholine activates the nicotinic acetylcholine receptor (ligand gated) on postsynaptic cell

Question 18

What is the importance of the vagus nerve?

Answer 18

-carries roughly 80% of total parasympathetic outflow
-carries tonnes of visceral afferents
-important for internal state of the body

Question 19

What does the spinal cord do?

Answer 19

-mediated autonomic reflexes
-receives sensory afferent + brainstem input

Question 20

What does the brainstem nuclei do?

Answer 20

-mediate autonomic reflexes
-medulla contains vagus nerve + where a lot of autonomic output is

Question 21

What does the hypothalamus do?

Answer 21

-involved in integration + coordination
-involved in: feeding, thermoregulation, circadian rhythms, water balance, sex drive, reproduction

Question 22

What does the forebrain do?

Answer 22

-regulates ANS output
-minimal conscious cortical control but cortical processes do regulate autonomic output

Question 23

What do the visceral afferents do?

Answer 23

-regulate ANS output
-sensory input from visceral afferent neurons takes priority over cortical function –> nothing else seems to matter

Question 24

Describe the general organisation of the autonomic nervous system for both the parasympathetic and sympathetic?

Answer 24

-preganglionic neuron in CNS
-sends an axon into periphery + synapses with postganglionic neuron in peripheral ganglion
-postganglionic neuron sends axon out to target cell

Question 25

What is a ganglion?

Answer 25

A group of neurons that have a similar function

Question 26

What type of fibres are preganglionic neurons always?

Answer 26

-cholinergic –> acetylcholine = primary neurotransmitter
- acetylcholine activates the nicotinic acetylcholine receptor on postsynaptic cell

Question 27

Describe transmission via the sympathetic pathway

Answer 27

-short, cholinergic preganglionic neurons from thoracic + lumbar spinal cord
-long, adrenergic postganglionic neurons
-target tissues express alpha and beta adrenergic receptors

Question 28

What are the neurotransmitters used in the sympathetic nervous system?

Answer 28

-acetylcholine between pre and postganglionic neuron
-noradrenaline from postganglionic to target cell (main neurotransmitter)

Question 29

Describe transmission via the parasympathetic nervous system

Answer 29

-long, cholinergic preganglionic neurons from brainstem + sacral spinal cord
-short, cholinergic postganglionic neurons
-target tissues express muscarinic acetylcholine receptors

Question 29

What are the main neurotransmitters in the parasympathetic nervous system?

Answer 29

Acetylcholine for pre + postganglionic neurons