Short term control of blood pressure

Question 1

What happens if MAP is too high?

Answer 1

Risk of hyperension

Question 2

What happens if MAP is too low?

Answer 2

Risk of fainting (syncope)

Question 3

Where are the two stretch receptors for the heart?

Answer 3

Aortic arch

Carotid sinus baroreceptors

Question 4

What happens to the baroreceptors if the blood pressure is raised?

Answer 4

More action potentials will be set off

Question 5

What are the sensory nerves for the heart and where do they go?

Answer 5

Vagus and glosspharyngeal nerves

Both are sent to medullary cardiovascular centres

Question 6

How does the parasympathetic system affect the heart rate?

Answer 6

Reduces the heart rate

Releases ACh on muscarinic receptors -> hyperpolarisation

Question 7

How does the sympathetic system affect the heart rate?

Answer 7

Releases noradenaline to SAN, acts on β1=receptors -> depolarises pacemaker faster -> increased heart rate
Act on ventricular muscle -> increases Ca2+ -> increases contractility -> increases SV -> increases CO
Venoconstriction -> increases preload, increases SV
Arteriolar constriction -> increases TPR and MAP -> act on α1 receptors
Offshoot to the adrenal medulla directly releases adrenaline into the blood, acts on SAN

Question 8

What are the other inputs to the medullary cardiovascular centres?

Answer 8

All minor in comparison
Cardiopulmonary baroreceptors
Central chemoreceptors
Chemoreceptors in muscle
Joint receptors
Higher centres

Question 9

What are the cardiopulmonary baroreceptors?

Answer 9

In heart and lungs
In low pressure regions like atria
Start firing in high pressure

Question 10

What are the central chemoreceptors?

Answer 10

Respond to CO2 and O2 concentration

Respiratory drive increased -> affects medullary CV system

Question 11

What do joint receptors do?

Answer 11

Activated when move joints more frequently

Question 12

What are higher centres?

Answer 12

Hypothalamus

• > feed forward system
• > anticipates doing work

Question 13

What affects MAP?

Answer 13

CO (HR, SV)

TPR

Question 14

What is the effect of standing on the cardiovascular system?

Answer 14

Increased hydrostatic pressure -> causes pooling of blood in veins/venules of feet/leg
Decreased venous return, decreased EDV, decreased preload, decreased SV, decreased CO, decreased MAP
Decreased baroreceptor firing rate

Question 15

What is the body’s response to the effect of standing?

Answer 15

Decreased vagal tone -> increased HR and CO
Increased sympathetic tone -> increased heart rate and CO, increased contractility, increased SV, increased CO, increased venoconstriction, increased venous return, increased EDV, increased SV, increased CO
Increased arteriolar resistance, increased TPR

Question 16

What is the valsalva maneouvre?

Answer 16

Forced expiration against a closed glottis

Question 17

What are the 6 steps in the valsalva manoeuvre?

Answer 17

1. Increase in pressure inside thorax
2. Exhalational pressure
3. Reflex response
4. Extra pressure removed from thorax
5. Venous return restored
6. Heart rate and BP back to normal

Question 18

What happens when the pressure inside the thorax increases?

Answer 18

Transmitted straight to arteries

Thoracic pressure and arteriolar pressure increases

Question 19

What happens in exhalational pressure?

Answer 19

Stops blood coming back

Decrease in venous return, decrease in EDV, decreaes in contraction, decrease in CO, decrease in arteriolar pressure

Question 20

What happens in the reflex response in Valsalva manoeuvre?

Answer 20

Decreased MAP is detected by baroreceptors

Initiates reflex, increased CO and increased TPR

Question 21

What happens when the extra pressure is remove from the thorax?

Answer 21

Decrease in pressure is transmitted through the aorta

Question 22

What happens when venous return is returned in the Valsalva manoeuvre?

Answer 22

Increases: EDV, SV and reflexes via adrenaline