Topic 6 - Autonomic Nervous System

Question 1

Role of ANS

Answer 1

To maintain homeostasis by regulating and coordinating vital visceral function –> cardiac muscle, smooth muscle and glands

Question 2

Physiological roles

Answer 2

1. Reg of heart –> BP, HR, contractility
2. Reg of smooth muscles –> GI, BV, bronchi, urogenital
3. Reg of secretory glands –> salivary, bronchiole, sweat

Question 3

Patterns

Answer 3

1. S opposes PS effect - HR
2. S compliments PS effect - PSN causes erection while SNS causes ejaculation
3. Innervation by only one division of ANS - veins only innervated by SNS

Question 4

Adrenergic Receptors

Answer 4

a1 = BV, pupils, urinary bladder sphincter
a2 = pancreas
b1 = heart
b2 = bronchioles of lungs

Question 5

Cholinergic Receptors

Answer 5

Nicotinic = first syNapse of both SNS + PNS
Muscarinic = effecter organ (<3, gland SM)

Question 6

Preganglionic Neurons

Answer 6

cell body in brainstem or SC
axon is myelinated type b fibre that extends to autonomic ganglion
NT = ACh

Question 7

Postganglionic Neurons

Answer 7

cell body lies outside CNS in an autonomic ganglion
axon is unmyelinated (slower) type c fibres that terminates in a visceral effector
ParaS NT = ACh
SymNT = noradrenaline + adrenaline

Question 8

Sympathetic NS

Answer 8

“Thoracolumbar division” lat horn of SC T1-L2
F+F response
PreG = Short
1. When preG leave cord, enter chain ganglia, may synapse in chain ganglia or leave w/o synapsing
2. If no synapse, preG form splanchnic nerves and synapse in collateral ganglia or cells of adrenal medulla and postG serve the abdominal viscera

Question 9

Parasympathetic NS

Answer 9

“craniosacral division” brainstem via CNS + sacral region S2-S4
Rest and digest
PreG = Long

Question 10

Vasovagal Syncope

Answer 10

Common faint and triggered at sight of blood, needles or emotional distress
Reaction: baroR and medullary centres activate sympathetic tone through vagal efferent fibres = decrease HR +BP
Recovery in supine with legs elevated

Question 11

Exercise Induced VS

Answer 11

Fainting during exercise - more common in young people

May occur as a result of exertion or something more sinister requiring investigation –> refer

Question 12

Anaphylaxis

Answer 12

An acute allergic reaction to an anitgen to which the body has become hypersensitive to - rapid and life threatening

• sudden drop in BP - vasoD, ↓CO, dizziness
• airways narrow - bronchospasm - bronchoconstriction and ↑ mucus production
• GI cramps and malabsorption - ↑ acid production and ↑ intestinal contraction

Question 13

EpiPen

Answer 13

contains single pre-measured dose of adrenaline which works by activation of SNS - acts on many body systems

Question 14

Symptoms of anaphylaxis

Answer 14

GI cramps = nausea, vomiting, diarrhoea
narrowing of airways = difficulty breathing, wheezing, nasal discharge, change in voice quality, coughing
Skin = itching, hives, enlarged tongue or lips, feelings of being flushed

Question 15

EpiPen = bronchoconstriction

Answer 15

1. B2 receptors of bronchiole vasculature stimulated
2. causes relaxtion of bronchiole smooth muscle = bronchodilation
3. results in increase oxygenation, improving ease of breathing

Question 16

EpiPen = ↓ in BP

Answer 16

1. adrenaline causes arteriolar SM to contract causing vasocon via a1 receptors
2. Cause ↑ in peripheral resistance and venous return = ↑CO
3. this then causes ↑ in BP