Autonomic nervous system

Question 1

What are the 2 subdivisions of the autonomic nervous system?

Answer 1

parasympathetic
sympathetic

Question 2

Autonomic nervous system functions

Answer 2

fight or flight response (sympathetic)
simple involuntary reflexes (parasympathetic)
maintenance of homeostasis

Question 3

Parasympathetic neurons length pre and post ganglion

Answer 3

long pre and short post ganglionic neurones

Question 4

Sympathetic neurons length pre and post ganglion

Answer 4

short pre and long post ganglionic neurones

Question 5

Describe preganglionic neurones of the ANS

Answer 5

cell bodies in intermediolateral grey column of spinal cord or homologous nuclei of brain (cranial nerves)

axons are mostly myelinated
slow conducting type B fibres

Question 6

Are postganglionic neuron axons myelinated?

Answer 6

mainly unmyelinated C fibres

Question 7

What neurotransmitter do postganglionic parasympathetic neurones produce and which receptors does this stimulate?

Answer 7

Acetylcholine
stimulate muscarinic receptors (M1, M3, M5 or M2, M4)

Question 8

What neurotransmitter do postganglionic sympathetic neurones produce and which receptors does this stimulate?

Answer 8

norepinephrine (noradrenaline)
stimulate adrenergic receptors (alpha1,2 or beta1,2,3)

Question 9

Name 2 cholinergic receptors

Answer 9

nicotinic
muscarinic

Question 10

What type of receptor is a nicotinic receptor?

Answer 10

ligand-gates (ionotropic) ion channel

Question 11

What type of receptor is a muscarinic receptor?

Answer 11

G-protein coupled (metabotropic) ion channel

Question 12

Describe the pupillary light reflex

Answer 12

when light shone into eyes, the pupils constrict
light on retina stimulates optic nerve fibres that innervate pretectal nuclei
secondary impulses pass to Edinger-Westphal nucleus and back through parasympathetic nerves to constrict the sphincter of the iris
in darkness, the reflex is inhibited, leading to dilation of the pupil

Question 13

What role do sympathetic and parasympathetic nerves play in the pupillary light reflex?

Answer 13

Parasympathetic nerves:
- excite ciliary muscles that control focussing of eye lens
- sphincter of iris that constricts pupil

Sympathetic nerves:
- radial fibres of iris that dilate pupil and several extraocular muscles of eyes

Question 14

Which cranial nerves are involved in the blink reflex?

Answer 14

eyelids are closed by:
- relaxation of levator palpebrae muscles (CN 3)
- contraction of orbicularis muscles (CN 7)
- corneal irritation - afferent is CN 5

Question 15

What cells mediate pupillary reflexes?

Answer 15

retinal ganglion cells