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Physiology, anatomy and biomechanics (2) > Venous return and distribution of cardiac output > Flashcards

Venous return and distribution of cardiac output Flashcards

1
Q

Name the five venous return mechanisms

A 
Gravity 
Muscle pump 
Respiratory pump 
Smooth muscle 
Pocket valves
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2
Q

Describe gravity

A

Aids vins in the upper body

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3
Q

Describe the muscle pump

A

Many veins are situated between skeletal muscles so squeeze veins when thy contract

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4
Q

Describe the respiratory pump

A
  • Helps to return blood in the thoracic cavity and abdomen to the heart
  • When exercising, blood pressure changes in the thorax between high and low to squeeze blood to the heart
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5
Q

Describe smooth muscle

A

On the wall of each vein, contracts to push blood towards the heart

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6
Q

Describe pocket valves

A

Located in the veins to prevent back flow of blood and pushes it to the heart

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7
Q

How much blood must be part of venous return?

A

3 fifths of circulating blood

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8
Q

What is the average cardiac output?

A

Rest: 5l/min
Exercise: 14-20l/min

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9
Q

Describe the cardiac control centre

A

(Medulla oblongata)
Autonomic nervus system
Sympathetic nervous system (increases HR)
Parasympathetic nervous system (decreases HR)
SA Node

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10
Q

What neural controls input the autonomic nervous system?

A

Chemoreceptors
Proprioreceptors
Baroreceptors

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11
Q

Describe chemoreceptors

A

Located in muscles, aorta and carotid arteries

Inform CCC of chemical changes in the blood e.g. increased CO2

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12
Q

Describe proprioreceptors

A

Located in the muscles, tendons and joints

Inform the CCC of motor activity

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13
Q

Describe baroreceptors

A

Located in the walls of blood vessels

Inform the CCC of blood pressure

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14
Q

What intrinsic controls input the autonomic nervous system?

A

Temperature and venous return

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15
Q

Describe temperature as an intrinsic control

A

Temperature changes will affect the viscosity of blood and speed up nerve impulse transmission

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16
Q

Describe venous return as an intrinsic control

A

Venous return changes affect the stretch in the ventricle walls and force of ventricular contraction and therefore stroke volume

17
Q

Describe the hormonal controls inputting the autonomous nervous system

A

Adrenaline and noradrenaline released from the adrenal glands increase the force of ventricular contraction and speed of cardiac electrical activity

18
Q

How does the sympathetic nervous system increase HR?

A

Releases adrenaline and sends stimulation to the SA node via the accelerator (cardiac) nerve

19
Q

How does the parasympathetic nervous system decrease HR?

A

Actioned to inhibit the effects of adrenaline via the vagus nerve

20
Q

Describe the vasomotor control centre

A

Medulla oblongata
Redistributes cardia output
Vascular shunt mechanism

21
Q

What inputs info to the Vasomotor control centre?

A

Chemo and baro receptors

22
Q

What does the VCC do during exercise?

A
  • Decreases sympathetic stimulation in the muscle cells
  • Arterioles and pre-capillary sphincters vasodilate
  • Increase blood flow to muscles
  • Sympathetic stimulation increased to organs
  • Arterioles and pre-capillary sphincters vasoconstrict
  • Decrease blood flow to organs
23
Q

What does the VCC do during recovery?

A
  • Increase sympathetic stimulation in muscle cells
  • Arterioles and pre-capillary sphincters constrict
  • Decrease blood flow to muscles
  • Sympathetic stimulation decreased to organs
  • Arterioles and pre-capillary sphincters dilate
  • Increased blood flow to organs
24
Q

Describe the vasomotor control when blood pressure decreases

A
  • Stimulates baroreceptors
  • Vasoconstriction of arterioles
  • Blood pressure increases
25
Q

Describe the vasomotor control when blood pressure increases

A
  • Stimulates baroreceptors
  • Vasodilates arterioles
  • Decreases blood pressure
26
Q

Describe venomotor control

A
  • Stimuli from sympathetic and parasympathetic nervous system
  • Veins alter their shape to increase the venomotor tone of their walls
  • Increase or decrease blood pressure
  • Not as effective as vasomotor control
27
Q

How does blood flow increase during physical activity?

A
  • Metabolism speed increases
  • Muscle oxygen demand increases
  • Heart rate increases
  • Speed of blood flow increases

Physiology, anatomy and biomechanics (2) (27 decks)

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