Review of the Sympathetic Nervous System

Question 1

Which tract supplies the sympathetic preganglionic neurones?

Answer 1

Reticulospinal tract

Question 2

What is the sympathetic chain?

Answer 2

Where the cell bodies of postganglionic sympathetic neurones lie

Question 3

What is the superior cervical ganglion?

Answer 3

Most superior sympathetic ganglion which projects into cervical region but isn’t connected to cervical ventral roots

Question 4

Describe how sympathetic postganglionic fibres travel

Answer 4

Form nerve plexuses around the carotid arteries and enter the skull with the carotids

Question 5

How do thoracic and abdominal preganglionic sympathetic neurones differ?

Answer 5

Thoracic have short preganglionic neurones whereas abdominal have long ones so sympathetic ganglia is a long way from the spinal cord and have different names (e.g. coeliac ganglion)

Question 6

Describe the coeliac ganglion and what is supplies

Answer 6

Present below diaphragm and anterior to aorta, supplies stomach and initial parts of small intestine

Question 7

What is the mesenteric ganglia?

Answer 7

Found around the lower abdominal aorta and has superior and inferior types

Question 8

What does the superior mesenteric plexus supply?

Answer 8

Innervates small intestine, ascending and transverse colon

Question 9

What does the inferior mesenteric plexus supply?

Answer 9

Innervates descending colon and rectum

Question 10

What is the consequence of coeliac ganglion stimulation?

Answer 10

Sphincter contraction, abdominal vasoconstriction, mobilisation of liver glycogen and secretion of adrenaline (adrenal medulla)

Question 11

What is the consequence of superior mesenteric ganglion stimulation?

Answer 11

Relaxation of small intestine and colon walls

Question 12

What is the consequence of inferior mesenteric ganglion stimulation?

Answer 12

Relaxation of small intestine and colon walls, constriction of sphincters and relaxation of urinary bladder and genital vasoconstriction

Question 13

How is adrenaline produced?

Answer 13

Tyrosine –> DOPA –> dopamine –> noradrenaline –> adrenaline

Question 14

What are catecholamines?

Answer 14

Dopamine, noradrenaline and adrenaline

Question 15

What axon type are sympathetic preganglionic neurones?

Answer 15

Myelinated type B

Question 16

How do sympathetic preganglionic neurones activate postganglionic neurones?

Answer 16

Release ACh

Question 17

What type of receptor is present on all autonomic ganglia?

Answer 17

Cholinergic nicotinic receptor

Question 18

What is the role of sympathetic postganglionic neurones?

Answer 18

Project to smooth muscle in arterioles –> vasoconstriction

Question 19

What type of axon do sympathetic postganglionic neurones have?

Answer 19

Unmyelinated type C

Question 20

How do sympathetic postganglionic neurones activate smooth muscle in

Answer 20

Noradrenaline release –> alpha 1 adrenoreceptors –> vasoconstriction

Question 21

What is the main function of the sympathetic nervous system?

Answer 21

Regulates blood distribution around the body

Question 22

What is the role of the sympathetic nervous system in preventing postural hypotension?

Answer 22

Normally keeps all arterioles of vascular beds slightly constricted to maintain blood pressure in the leg muscles when you stand

Question 23

What happens in the fight or flight response?

Answer 23

Vasoconstriction in non-working muscles (e.g. digestion), adrenaline release, pupil dilation

Question 24

Which sympathetic ganglion is involved in pupillary dilation and thickened salivary secretions?

Answer 24

Superior cervical ganglion

Question 25

Which sympathetic ganglion is involved in ejaculation and voiding the bladder?

Answer 25

Hypogastric ganglion

Question 26

Which sympathetic ganglion is involved in peristaltic inhibition of the gut?

Answer 26

Coeliac ganglion

Question 27

What does sympathetic activation of alpha receptors achieve?

Answer 27

Constriction of vessels in gut --> shunt to working muscles

Question 28

What does sympathetic activation of beta 1 receptors achieve?

Answer 28

Increase CO

Question 29

What does sympathetic activation of beta 2 receptors achieve?

Answer 29

Relax bronchial SM and increase glycogenolysis and lipolysis

Question 30

What does sympathetic activation of beta 3 receptors achieve?

Answer 30

Increase glycogenolysis and lipolysis

Question 31

How do stressors affect the sympathetic nervous system?

Answer 31

Stressors activate SNS ad hypothalamo-pituitary-adrenal axis --> adrenocorticotrophic hormone --> cortisol release from adrenal cortex --> stimulates adrenaline and noradrenaline synthesis

Question 32

How does the sympathetic nervous system react to injury or haemorrhage?

Answer 32

Constriction of veins increases (increase/maintain venous return to heart to maintain BP and CO), severe blood loss --> vasoconstriction to non-essential organs, renin and ADH release to reduce urine flow and fluid loss (increase BP), alpha receptors in vascular SM --> constriction and sensitise platelets to collagen to make endothelium 'sticky' --> clotting

Question 33

Describe sympathetic alpha adrenoreceptors

Answer 33

``` a1 = on vascular smooth muscle --> constriction a2 = on presynaptic sympathetic nerve terminals (negative feedback for noradrenaline release) ```

Question 34

Describe sympathetic beta adrenoreceptors

Answer 34

``` B1 = on cardiac muscle to increase HR and contraction force B2 = relaxes bronchial smooth muscle B3 = on adipose tissue --> lipolysis ```

Question 35

What molecule do alpha adrenoreceptors mainly respond to?

Answer 35

Noradrenaline

Question 36

What molecule do beta adrenoreceptors mainly respond to?

Answer 36

Adrenaline (but can respond to noradrenaline)

Question 37

How do beta blockers work?

Answer 37

Antagonist of B1 receptors to reduce HR and contraction force in hypertensive patients

Question 38

How does salbutamol work?

Answer 38

Agonist of B2 receptor --> bronchodilation