Short term control of blood pressure

Question 1

State the equation for MAP

Answer 1

MAP = CO x TPR

Question 2

What is the driving force pushing blood through circulation?

Answer 2

MAP

Question 3

Describe the mechanism of arterial baroreceptors

Answer 3

Stretch reflex
Sensory neurone fire APs when stretched
Have tone and are fired all through the cardiac cycle

Question 4

State the two types of arterial baroreceptors

Answer 4

Carotid sinus baroreceptors

Aortic arch baroreceptors

Question 5

What nerve are sensory fibres of carotid sinus baroreceptors carried in?

Answer 5

Sensory fibres travel in GLOSSOPHARYNGEAL NERVE

Question 6

What nerve are sensory fibres of aortic arch baroreceptors carried in?

Answer 6

Sensory fibres travel in VAGUS NERVE

Question 7

What arterial baroreceptors have sensory fibres in the vagus nerve?

Answer 7

Aortic arch baroreceptors

Question 8

What arterial baroreceptors have sensory fibres in the glossopharyngeal nerve?

Answer 8

Carotid sinus baroreceptors

Question 9

Where do arterial baroreceptors signal to?

Answer 9

Medullary cardiovascular centres

Question 10

Describe the effect of increased stretch on arterial baroreceptors

Answer 10

More APs fired
Activates parasympathetic (vagus nerve) system
Ach acts on muscarinic receptors
Reduced sinoatrial node activity -> reduced HR ->
reduced CO; since MAP = CO x TPR, MAP is also reduced

Question 11

Describe the effect of reduced stretch on arterial baroreceptors

Answer 11

Less APs fired
Activates sympathetic (thoracolumbar) system
Noradrenaline and adrenaline act on Beta 1 receptors in the sinoatrial node -> increased HR
Beta 1 receptors in myocytes -> increased contractility and SV, therefore increased CO
Alpha 1 receptors - arteriolar constriction leads to increased TPR and increased MAP and venoconstriction leads to increased EDV

Question 12

List the other inputs into short term control of BP

Answer 12

Cardiopulmonary baroreceptors
Chemoreceptors in muscle 
Joint receptors 
Higher centres
Posture

Question 13

Describe the input of cardiopulmonary baroreceptors into short term BP control

Answer 13

Low pressure receptors in atrial walls and lung vessels

Respond to increased blood volume and tell medullary receptors that BP is high

Question 14

Describe the input of chemoreceptors in muscle into short term BP control

Answer 14

Detect increased K+ or reduced pH

Question 15

Describe the input of central chemoreceptors into short term BP control

Answer 15

Detect CO2 and O2 and determine rate and depth of breathing - contribute to respiratory drive

Question 16

Describe the input of joint receptors into short term BP control

Answer 16

Detect movement and send blood back to that area

Question 17

Describe the input of higher centres into short term BP control

Answer 17

Hypothalamus tells heart going to have to work hard

Question 18

Describe the input of posture into short term BP

Answer 18

Standing increases hydrostatic pressure leading to the pooling of blood in veins and venules of the feet and legs.
This leads to reduced venous return, reduced EDV, reduced preload, reduced SV, reduced CO and reduced MAP

Question 19

Describe how there is a reflex response to standing posture to control short term BP

Answer 19

Reduced vagal tone increases HR
Increased sympathetic tone -> increased HR and CO
Increased contractility -> increased SV and CO
Increased venoconstriction -> increased VR, increased EDV, increased SV and increased CO
Increased arteriolar constriction -> increased TPR

Question 20

Define the valsalva manoeuvre

Answer 20

Forced expiration against a forced glottis, resulting in an increase in thoracic pressure

Question 21

Describe changes in blood pressure during the valsalva manoeuvre

Answer 21

Increased thoracic pressure transmitted to aorta
Increased thoracic pressure -> reduced venous return -> reduced EDV -> reduced SV -> reduced CO and reduced MAP
Reduced MAP detected by baroreceptors which reflexly increase CO and TPR those increasing MAP
Decreased thoracic pressure transmitted to aorta but reflex doesn’t wear off that quickly
Back to normal - pressure added is subtracted as aortic compression is removed when a person starts to breathe again

Question 22

What is different about long term BP control?

Answer 22

Cardiopulmonary receptors only

Mostly hormonal