11. Regulation of the cardiovascular system

Question 1

What is venous volume distribution affected by?

Answer 1

Peripheral Venous Tone
Gravity
Skeletal Muscle Pump
Breathing

Question 2

What are the ways of regulating flow?

Answer 2

Local Mechanisms - intrinsic to the smooth muscle
Hormonal
Autonomic Nervous System - innervates arterioles and veins to produce constriction or dilation

Question 3

Define autoregulation

Answer 3

The intrinsic capacity to compensate for changes in perfusion pressure by changing vascular resistance

Question 4

What happens to resistance when blood pressure decreases?

Answer 4

There is a gradual decrease in resistance and hence a gradual increase in flow

Question 5

What is the myogenic theory?

Answer 5

Smooth muscle fibres respond to stretch

Question 6

What is the metabolic theory?

Answer 6

When a vascular bed contracts the flow decreases and the more metabolites are produced. This feeds back on the vessel and causes vasodilation and hence allows more flow to the vascular bed washing the metabolites away

Question 7

What vasoconstrictor is released by platelets?

Answer 7

Serotonin

Question 8

What hormones regulate blood flow?

Answer 8

Kinins
ANP
Circulating vasoconstrictors

Question 9

What are the effects of kinins?

Answer 9

Interact with renin-angiotensin system

Relax vascular smooth muscle

Question 10

What are the effects of ANP?

Answer 10

ANP = Atrial Natriuretic Peptide

Causes vasodilation, secreted from the cardiac atria

Question 11

List some circulating vasoconstrictors

Answer 11

Vasopressin
Angiontensin II
Noradrenaline

Question 12

What does the sympathetic nervous system control?

Answer 12

The flow

Question 13

What does the parasympathetic nervous system control?

Answer 13

Heart rate - The parasympathetic ganglion will be right beside the sinoatrial node due to the long pre and short post ganglionic fibre

Question 14

What vessels do sympathetic nerve fibres not innervate?

Answer 14

Capillaries

Question 15

Which organs have the greatest sympathetic nerve supply?

Answer 15

Kidney, gut, spleen and skin

Question 16

Which organs receive the fewest sympathetic nerves?

Answer 16

Skeletal muscle and brain

Question 17

What does the distribution of nerve supply suggest?

Answer 17

The more nerves the more potential there is to constrict and redirect blood flow away from those organs

Question 18

What happens at low concentrations of adrenaline?

Answer 18

Binds to smooth muscle beta-2-adrenoreceptors causing vasodilation

Question 19

What happens at high concentrations of adrenaline?

Answer 19

Binds to alpha adrenoreceptors overriding the effects of the beta-2-adrenoreceptors. Vasoconstriction

Question 20

What receptor is responsible for constriction in blood vessels?

Answer 20

alpha-1-adrenoreceptor

Question 21

Where is the VMC located?

Answer 21

bilaterally in the reticular substance of the medulla and the lower third of the pons

Question 22

What is the VMC?

Answer 22

Vasomotor centre

Question 23

What does the VMC consist of?

Answer 23

Vasoconstrictor area
Vasodilator area
Cardioregulatory inhibitory area

Question 24

What portion of the VMC controls heart activity?

Answer 24

Lateral portions

Question 25

What do the lateral portions of the VMC control?

Answer 25

Heart rate and contractility

Question 26

What does the medial portion of the VMC send signals to?

Answer 26

Vagus nerve to the heart decreasing heart rate

Question 27

What response does the VMC allow before exercise?

Answer 27

Anticipatory response to excercise

Question 28

What neurotransmitter is involved with sympathetic innervation?

Answer 28

noradrenaline

Question 29

What happens if you increase the nerve traffic in a sympathetic nerve supplying a blood vessel?

Answer 29

You constrict the vessel

Question 30

What happens if you decrease the nerve traffic in a sympathetic nerve supplying a blood vessel?

Answer 30

You dilate the vessel

Question 31

What are the three factors that can control vessel radius?

Answer 31

1) Local Controls 2) Circulating Hormones 3) Sympathetic Vasocontrictor Nerves

Question 32

How is the heart rate changed?

Answer 32

By dual innervation - sympathetic and parasympathetic

Question 33

What innervates the SAN?

Answer 33

Sympathetic and parasympathetic nerves

Question 34

What is normal resting heart rate?

Answer 34

70 bpm

Question 35

How does parasympathetic nerves affect the heart?

Answer 35

It slows heart rate - acetylcholine decreases the gradient of the pacemaker potential

Question 36

How does the sympathetic nerves affect the heart?

Answer 36

Increases heart rate - adrenaline and noradrenaline increase the gradient of the pacemaker potential

Question 37

What can increase the force of contraction?

Answer 37

Starling's Law and Sympathetic activity

Question 38

How does the sympathetic activity increase the force of contraction?

Answer 38

Noradrenaline binds to Adrenoreceptors which increases the amount of cAMP which activates PKA which phosphorylates the L-type calcium channels and the SR calcium release channel and SERCA. So you get MORE CALCIUM INFLUX and more calcium taken back up into the stores

Question 39

What adrenoreceptor does noradrenaline bind to in the heart?

Answer 39

beta-1-receptors

Question 40

What does binding of beta-1-receptors cause in the heart?

Answer 40

Increased contraction

Question 41

What can increase stroke volume?

Answer 41

Starling's law Increased sympathetic nerves to heart Increased plasma adrenaline

Question 42

How does increasing respiratory movements increase venous return to the heart?

Answer 42

Decreasing intrathoracic pressure helps filling of the heart

Question 43

What does increasing the sympathetic activity to heart cause?

Answer 43

Increased heart rate and Stroke volume

Question 44

Where are baroreceptors located?

Answer 44

Aortic arch and in the carotid sinus (bodies)

Question 45

Where do the baroreceptors in the carotid bodies feedback to?

Answer 45

To the vasomotor centre via the glossopharyngeal nerve

Question 46

Where do the baroreceptors in the aortic arch feedback to?

Answer 46

To the vasomotor centre via the vagus nerve

Question 47

Aortic arch baroreceptor =

Answer 47

Vagus nerve

Question 48

Carotid sinus baroreceptor =

Answer 48

Glossopharyngeal nerve

Question 49

What pressure do the carotid sinus baroreceptors respond to?

Answer 49

60 and 80 mmHg

Question 50

What pressure do the aortic arch baroreceptors respond to?

Answer 50

90-100 mmHg

Question 51

Reciprocal innervation - What happens the baroreceptor detects a increase in pressure?

Answer 51

Increase in baroreceptor firing = Increase in parasympathetic activity and decrease in sympathetic activity. The decrease in sympathetic activity is brought about by inhibitory interneurones

Question 52

What is the overall effect when the baroreceptors detect a increase in blood pressure?

Answer 52

Decrease heart rate (increased parasympathetic stimulation and decreased sympathetic stimulation) and vasodilation (decreased sympathetic stimulation to the blood vessels)

Question 53

What can the strength of contraction not be altered by?

Answer 53

parasympathetic activity

Question 54

Where does an increase in baroreceptor fed to?

Answer 54

vasomotor centre causing increased increased traffic in the vagus nerve

Question 55

How does an increase in parasympathetic activity affect the SAN?

Answer 55

There is an increased production of acetylcholine in the SAN which serves to decrease the gradient of the pacemaker potential = decreasing heart rate

Question 56

Less innervation from the sympathetic nerves causes what?

Answer 56

Decreased force of contraction and increase in vessel radius

Question 57

Overall what does an increased parasympathetic and decreased sympathetic innervation cause?

Answer 57

Decrease in blood pressure