Lecture 18 - The Baroceptor Reflex

Question 1

What is arterial blood pressure controlled by

Answer 1

Cardiac output, total peripheral resistance and blood volume

Question 2

How is arterial blood pressure regulated short term

Answer 2

Neuronal mechanisms

Question 3

How is arterial blood pressure regulated long term

Answer 3

Hormonal mechanisms

Question 4

Baroreceptors found where monitor arterial pressure

Answer 4

The aortic arch and carotid sinus

Question 5

Where do baroreceptors project nerve fibres to

Answer 5

The cardiovascular centre in the brain stem

Question 6

Is the baroreceptor reflex neuronal or hormonal

Answer 6

Neuronal

Question 7

What does the baroreceptor reflex consist of

Answer 7

A detector, afferent neural pathways, a coordinating centre, efferent neural pathways and effectors

Question 8

What is the function of the afferent neural pathways

Answer 8

Conway information to the CNS

Question 9

What is the coordinating centre and where is it

Answer 9

It compares signals detected in the periphery and compare them to a set-point and generates an error message. It is found in the CNS

Question 10

What is the function of efferent neural pathways

Answer 10

They relay the output of the coordinating centre to the periphery

Question 11

What is the function of the effectors

Answer 11

The execute an appropriate response and alter the controlled variable, correcting the deviation from the set-point

Question 12

What does increase mean arterial pressure cause

Answer 12

Vasodilation and bradycardia

Question 13

What does decreased mean arterial blood pressure cause

Answer 13

Vasoconstriction and tachycardia

Question 14

What does blood flow to the brain through

Answer 14

The carotid arteries

Question 15

What type of receptors are baroreceptors

Answer 15

Mechanoreceptors

Question 16

How are baroreceptors activated in vessels

Answer 16

By stretch, not directly by pressure

Question 17

What nerve do the carotid sinus afferents travel on

Answer 17

The sinus nerve

Question 18

What cranial nerve do carotid sinus afferent end up on

Answer 18

The glossopharyngeal

Question 19

What part of the brain stem is the cardiovascular centre found

Answer 19

In the medulla

Question 20

What nerve do the aortic arch afferents travel in

Answer 20

The vagus nerve

Question 21

What are baroreceptors the terminals of

Answer 21

Myelinated and unmyelinated sensory fibres

Question 22

What do myelinated and unmyelinated sensory fibres express

Answer 22

Cation-selective ion channels activated by stretch

Question 23

When the cation-selective ion channels are open what do they generate

Answer 23

A graded receptor potential that causes an action potential generation with both static and dynamic qualities

Question 24

What is dynamic in relation to pressure

Answer 24

When the pressure is changing

Question 25

What is static, in relation to pressure

Answer 25

When the pressure is constant

Question 26

When does baroreceptor activity stop

Answer 26

At very low pressures (40-60 mmHg)

Question 27

How is central coordination of the baroreceptor reflex accomplished

Answer 27

By a complex of medullary nuclei collectively termed the cardiovascular centre

Question 28

What is the most important transmitter within bulbospinal neurones

Answer 28

Glutamate

Question 29

Bulbospinal neurones synapse with preganglionic sympathetic neurones between what levels of the spinal cord

Answer 29

T1 and L3

Question 30

When preganglionic neurones excite post ganglionic neurones through the sympathetic nervous system what does it cause

Answer 30

Vasodilation, increased heart rate and force of contraction

Question 31

How do preganglionic neurones excite adrenomedullary chromaffin cells

Answer 31

Via the release of ACh and activation of nicotinic receptors causing the release of adrenaline and noradrenaline

Question 32

When preganglionic neurones excite post ganglionic neurones through the parasympathetic nervous system what does it cause

Answer 32

A decreased heart rate and limited vasodilation

Question 33

What are the reflex effects of baroreceptor unloading

Answer 33

Increased sympathetic activity, decreased vagal parasympathetic activity so this causes increased HR and contractility so increases CO, arteriolar vasoconstriction so increased TPR and venoconstriction which supports central venous pressure and stroke volume