Cardiovascular systems 6 - Cardiovascular control 2 Flashcards Preview

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Flashcards in Cardiovascular systems 6 - Cardiovascular control 2 Deck (23)
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1
Q

What three factors does constriction of arterioles determine?

A
  • Bloodflow to downstream organs
  • Mean arterial blood pressure
  • Pattern of blood flow to organs
2
Q

What is the local method of regulating blood flow?

A

Autoregulation - changing diameter in response to flow.

3
Q

What are the local hormones that affect radius of arterioles?

A
  • Nitric oxide (vasodilator)
  • Prostacylin (vasodilator)
  • Thromboxane (vasoconstrictor)
  • Endothelins (vasoconstrictors)
4
Q

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

A
  • Kinins (vasodilator)
  • Atrial natriuretic peptide (vasodilator)
  • Vasopressin (vasoconstrictor)
  • Noradrenaline (vasoconstriction)
  • Angiotensin II (vasoconstrictor)
5
Q

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

A
  • SNS controls circulation

- PNS controls heartbeat

6
Q

Where do parasympathetic nerves arise from?

A
  • Cranial part of the spinal chord

- Sacral part of the spinal chord

7
Q

Where do sympathetic nerves arise from?

A
  • Thoracic vertebra

- Lumbar vertebra

8
Q

What neurotransmitters are used in pre-ganglionic fibres?

A

Acetylcholine

9
Q

What neurotransmitters are used in post-ganglionic fibres?

A
  • PNS uses acetylcholine

- SNS uses noradrenaline

10
Q

Where does noradrenaline bind on smooth muscle?

A
  • a1 adrenoreceptors

- Causes vasoconstriction

11
Q

Describe the location and structure of the vasomotor centre.

A
  • Located in the medulla
  • Contains a vasoconstrictor (pressor) area, and a vasodilator (depressor) area, as well as a cardioregulatory inhibitory area
12
Q

What is the function of the vasomotor centre?

A
  • Controls blood vessels
  • Influences heart rate and contractility
  • Controlled by hypothalamus
13
Q

What are the locations of baroreceptors?

A
  • 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
14
Q

What pressures are baroreceptors most sensitive to?

A

90-100mmHg

15
Q

What is the consequence of increased baroreceptor activity?

A
  • Parasympathetic nerves are stimulated

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

16
Q

What is the consequence of hemorrhage?

A
  • 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.
17
Q

When is afferent activity highest in baroreceptors?

A

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

18
Q

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

A

Parasympathetic nerves have the shorter postganglionic fibres.

19
Q

What is the myogenic mechanism hypothesis for autoregulation?

A

Smooth muscle fibres respond to tension in the vessel wall

20
Q

What is the metabolic mechanism hypothesis for autoregulation?

A

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

21
Q

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

A

Respond to local stimuli - metabolism and shear stress

22
Q

What determines resting heart rate?

A

PNS and SNS stimulation

23
Q

How are blood vessels innervated?

A
  • By SNS efferents only

- Capillaries recieve no innervation

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