Autonomic Physiology 1

Question 1

What does the autonomic nervous system exist to control?

Answer 1

Involuntary processes - the things you don’t think about.

Question 2

Give examples of things that the autonomic nervous system controls.

Answer 2

Smooth muscle surrounding blood vessels, airways, bladder, gut and sex organs.
Secretions from glands.
Focussing of the eye.
Etc…

Question 3

Where do afferent neurones carry impulses from and to?

Answer 3

From sensory receptors to the CNS.

Question 4

Where do efferent neurones carry impulses from and to?

Answer 4

From CNS to peripheral effector organs/structures.

Question 5

What does the somatic nervous system control?

Answer 5

Skeletal muscle control of voluntary body movements.

Question 6

Describe the fibre(s) involved in sending electrical signals in the somatic nervous system.

Answer 6

One neurone with a very long axon which reaches the skeletal muscle.

Question 7

Describe the fibre(s) involved in sending electrical signals in the autonomic nervous system.

Answer 7

Preganglionic fibre (small, myelinated) which passes signal to post ganglionic fibre and post-ganglionic fibre (unmyelinated) passes signal to smooth muscle/cardiac muscle.glands/GI neurones…

Question 8

Compare how specialised the junctions are in the somatic nervous system and autonomic nervous system.

Answer 8

Somatic nervous system - very specialised NMJ: neurotransmitters are directed towards very specific area (end plate).

Autonomic nervous system - less specialised junction (can be just released in the vicinity of lots of cells)

Question 9

What kind of receptors do the neurotransmitters bind to in the somatic nervous system?

Answer 9

Ionotropic receptors (integral channel - fast response).

Question 10

What kind of receptors do the neurotransmitters bind to in the autonomic nervous system?

Answer 10

Metabotropic receptors (G-coupled - slower)

Question 11

Comment on excitatory/inhibitory responses in the autonomic and somatic nervous system.

Answer 11

Neurones in the somatic nervous system always excite the target, so always cause depolarisation of end plate.

Neurones in autonomic nervous system may excite or inhibit target.

Question 12

What does the sympathetic system do?

Answer 12

Prepares you to fight or flight.
Heart rate and blood pressure increase, airways dilate, pupils dilate, eyes focus far away, hair stands on end, mouth is dry, glycogen stores mobilised, not digesting…

Question 13

What does the parasympathetic system do?

Answer 13

Let’s you rest and digest.
Heart rate and blood pressure decreases, pupils constrict, eyes focussed closer, hair down, laying down energy stores, digesting.

Question 14

Where do the parasympathetic neurones comes from the CNS? And where do they go to?

Answer 14

Parasympathetic system is crania-sacral, so there is cranial outflow to head and neck and sacral to the bladder and genitals.
Cranial (III, VII, IX, X) and sacral s(2-4).

Question 15

Where do the sympathetic neurones comes from the CNS? And where do they go to?

Answer 15

Sympathetic system is thoraco-lumbar. the ganglia lie close to the spinal cord in the sympathetic trunk (long post-ganglionic fibre).
T(1-12) and L(1-2)

Question 16

Describe the post and pre-ganglionic fibres in the parasympathetic system.

Answer 16

Long pre-ganglionic fibre and short post-ganglionic, meaning the ganglion are in or close to their target.

Question 17

Describe the post and pre-ganglionic fibres in the sympathetic system.

Answer 17

Ganglia close to spinal cord in sympathetic trunk (aka para-vertebral ganglia), this extends further into cervical ganglia. Normally the pre-ganglionic fibre enters the sympathetic trunk, makes synapse to long post-ganglionic fibre.

Question 18

How do other post and pre-ganglionic fibres in the sympathetic system differ from normal?

Answer 18

Some go straight through and make synapse in the pre-vertebral (collateral) ganglia, e.g. celiac and mesenteric ganglia then the post-ganglionic fibre carries on.

Question 19

How is the adrenal gland also an exception in terms of pre and post-ganglionic fibres in the sympathetic system?

Answer 19

Post-ganglionic cells of the adrenal medulla have no axon, but release adrenaline and noradrenaline (80%/20%) into the blood.

Question 20

In the spinal cord, where are the pre-ganglionic fibres found?

Answer 20

White ramus (white due to myelination).

Question 21

In the spinal cord, where are the post-ganglionic fibres found?

Answer 21

Grey ramus (grey as unmyelinated).

Question 22

What two things allow mass activation?

Answer 22

Convergence and divergence.

Question 23

What is convergence?

Answer 23

Many pre-ganglionic fibres synapsing onto one post-ganglionic fibre.

Question 24

What is divergence?

Answer 24

One pre-ganglionic fibre synapsing onto several post-ganglionic fibres.

Question 25

What are the autonomic neurotransmitters?

Answer 25

Acetylcholine.
Noradrenaline.
Adrenaline.

Question 26

What kind of receptors does acetylcholine act on?

Answer 26

Cholinergic receptors - nicotinic receptors or muscarinic receptors.

Question 27

What kind of receptors do noradrenaline and adrenaline act on?

Answer 27

Adrenergic receptors - aplha and beta receptors.

Question 28

In the sympathetic system, what do the pre-ganglionic fibres release and what kind of receptor does it act on?

Answer 28

Release acetylcholine.

Acts on nicotinic cholinergic receptors.

Question 29

In the sympathetic system, what do the post-ganglionic fibres release and what kind of receptor does it act on?

Answer 29

Release noradrenaline.

Acts on alpha or beta adrenergic receptors.

Question 30

In the parasympathetic system, what do the pre-ganglionic fibres release and what kind of receptor does it act on?

Answer 30

Release acetylcholine.

Acts on nicotinic cholinergic receptors.

Question 31

In the parasympathetic system, what do the post-ganglionic fibres release and what kind of receptor does it act on?

Answer 31

Release acetylcholine.

Acts on muscarinic cholinergic receptors.

Question 32

Give examples of when pre- or post-ganglionic fibres don’t follow normal rules.

Answer 32

Sympathetic cholinergic fibres innervate sweat glands.

Some post-ganglionic fibres release non-adrenergic non-cholinergic (NANC) transmitters (peptides or NO).