4.2 The ANS and CVS

Question 1

What is the ANS split into?

Answer 1

The parasympathetic and the sympathetic nervous system

Question 2

Where does the sympathetic nervous system originate from?

Answer 2

The thoracolumnar area.

Segments T1 to L2

Question 3

Where does the parasympathetic nervous system originate from?

Answer 3

The craniosacral area
Cranial nerves (III, VII, IX, X)
Sacral nerves S2 to S4

Question 4

What do all preganglionic neurones release?

Answer 4

Acetylcholine

Question 5

What do postganglionic parasympathetic neurones release?

Answer 5

Acetylcholine

Question 6

What do postganglionic sympathetic neurones release?

Answer 6

Noradrenaline

Question 7

What is a chromaffin cell?

Answer 7

Present in the adrenal medulla

Specialised sympathetic neurone which releases adrenaline

Question 8

Why are there subtypes of adrenoreceptors?

Answer 8

Allows for diversity or action and selectivity of drug action

Question 9

When does the sympathetic nervous system tend to act?

Answer 9

Under stress

Question 10

When does the parasympathetic system tend to act?

Answer 10

Under basal conditions

Question 11

In what way does the ANS control the CVS?

Answer 11

Controls:
Heart rate
Force of contraction
Peripheral resistance of the blood vessels

Question 12

Which nerves supplies parasympathetic innervation to the heart?
Where does it synapse?

Answer 12

Vagus nerve

SAN and AVN

Question 13

How does parasympathetic innervation slow the heart rate?

Answer 13

Acetylcholine reacts with the muscarinic receptors to decrease AV node conduction velocity

Question 14

How does sympathetic innervation increase the heart rate?

Answer 14

Increases the force of contraction

Question 15

How does sympathetic activity change the shape of the SA node action potential graph?

Answer 15

The funny current slope gradient is increased so the threshold is reached more quickly.

Question 16

How is the force of heart contraction increased?

Answer 16

Noradrenaline acts on B1-receptors. This causes an increase in cAMP which activates PKA. Ca2+ channels are phosphorylised causing more Ca2+ to enter the cell during depolarisation. More Ca2+ in the sarcoplasmic reticulum means a greater contraction on depolarisation.

Question 17

In vasculature what happens with:

i. ) Increased sympathetic output
ii. ) Stable sympathetic output
iii. ) Decreased sympathetic output

Answer 17

i. ) Vasoconstriction
ii. ) Vasomotor tone
iii. ) Vasodilation

Question 18

What is the job of a baroreceptor and where are they found?

Answer 18

Detects high pressure in vessels

Found in the aortic arch and in the carotid sinus

Question 19

When is adrenaline given clinically?

Answer 19

Restores function after a cardiac arrest

Given for anaphylactic shock

Question 20

Name 3 mechanisms the ANS regulates

Answer 20

Heart rate
Blood pressure
Body temperature