Cardiovascular systems 6 - Cardiovascular control 2

Question 1

What three factors does constriction of arterioles determine?

Answer 1

• Bloodflow to downstream organs
• Mean arterial blood pressure
• Pattern of blood flow to organs

Question 2

What is the local method of regulating blood flow?

Answer 2

Autoregulation - changing diameter in response to flow.

Question 3

What are the local hormones that affect radius of arterioles?

Answer 3

• Nitric oxide (vasodilator)
• Prostacylin (vasodilator)
• Thromboxane (vasoconstrictor)
• Endothelins (vasoconstrictors)

Question 4

What are the circulating hormones that affect the radius of arterioles?

Answer 4

• Kinins (vasodilator)
• Atrial natriuretic peptide (vasodilator)
• Vasopressin (vasoconstrictor)
• Noradrenaline (vasoconstriction)
• Angiotensin II (vasoconstrictor)

Question 5

What are the primary roles of the SNS and PNS of the cardiovascular system?

Answer 5

• SNS controls circulation

- PNS controls heartbeat

Question 6

Where do parasympathetic nerves arise from?

Answer 6

• Cranial part of the spinal chord

- Sacral part of the spinal chord

Question 7

Where do sympathetic nerves arise from?

Answer 7

• Thoracic vertebra

- Lumbar vertebra

Question 8

What neurotransmitters are used in pre-ganglionic fibres?

Answer 8

Acetylcholine

Question 9

What neurotransmitters are used in post-ganglionic fibres?

Answer 9

• PNS uses acetylcholine

- SNS uses noradrenaline

Question 10

Where does noradrenaline bind on smooth muscle?

Answer 10

• a1 adrenoreceptors

- Causes vasoconstriction

Question 11

Describe the location and structure of the vasomotor centre.

Answer 11

• Located in the medulla
• Contains a vasoconstrictor (pressor) area, and a vasodilator (depressor) area, as well as a cardioregulatory inhibitory area

Question 12

What is the function of the vasomotor centre?

Answer 12

• Controls blood vessels
• Influences heart rate and contractility
• Controlled by hypothalamus

Question 13

What are the locations of baroreceptors?

Answer 13

• Mechanoreceptors in the carotid sinus, which change their firing rate due to pressure changes
• Mechanoreceptors in the aortic arch change their firing rate due to changes in pressure

Question 14

What pressures are baroreceptors most sensitive to?

Answer 14

90-100mmHg

Question 15

What is the consequence of increased baroreceptor activity?

Answer 15

• Parasympathetic nerves are stimulated

- Sympathetic nerves are inhibited, this is by inhibiting the basal tonic activity of sympathetic nerves

Question 16

What is the consequence of hemorrhage?

Answer 16

• Blood volume decreases
• Venous pressure and atrial pressure decrease
• Cardiac output and blood pressure decreases. This is detected by baroreceptors, which increases venous pressure.
• This results in increased loss of blood.

Question 17

When is afferent activity highest in baroreceptors?

Answer 17

When systolic blood pressure is high, and pulse pressure is high

Question 18

Do sympathetic efferent nerves or parasymapathetic nerves have shorter post ganglionic fibres?

Answer 18

Parasympathetic nerves have the shorter postganglionic fibres.

Question 19

What is the myogenic mechanism hypothesis for autoregulation?

Answer 19

Smooth muscle fibres respond to tension in the vessel wall

Question 20

What is the metabolic mechanism hypothesis for autoregulation?

Answer 20

Metabolites accumulate as blood flow decreases, causing vessels to dilate so metabolites are washed away.

Question 21

What do local molecules which affect vascular smooth muscle contraction respond to?

Answer 21

Respond to local stimuli - metabolism and shear stress

Question 22

What determines resting heart rate?

Answer 22

PNS and SNS stimulation

Question 23

How are blood vessels innervated?

Answer 23

• By SNS efferents only

- Capillaries recieve no innervation