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BIOL 273 - Principles of Human Physiology 1 > 4.4 - Regulation of Cardiac Output > Flashcards

4.4 - Regulation of Cardiac Output Flashcards

1
Q

What is cardiac output?

A

volume of blood pumped by the heart in a given period of time
CO = heart rate x stroke volume
CO = 72 beats/min x 70mL/beat
= 5 L/min

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2
Q

How is stroke volume calculated?

A

Stroke Volume = EDV - ESV

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3
Q

What are factors influencing heart rate?

A
  • Parasympathetic stimulation: decreases HR
    via vagus nerve: ACh (muscarinic receptors)
  • Sympathetic stimulation: increases HR
    via great cardiac nerve: NE (b1 adrenergic receptors)
  • plasma epinephrine: increases HR
    from adrenal medulla
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4
Q

What are factors influencing Stroke Volume?

A

Parasympathetic stimulation: decreases contractility
Sympathetic stimulation: increases contractility
Plasma Epinephrine: increases contractility
Increased End Diastolic Volume: increases stroke volume

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5
Q

What are factors affecting venous return?

A
  • Total blood volume: more blood means more can be loaded into the ventricles
  • Sympathetic vasoconstrictor nerves: constrict blood vessels pushes blood towards the heart
  • Skeletal muscle pump: muscle contractions push blood toward heart
  • Respiratory pump: creates low pressure in thorax and high pressure in abdomen
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6
Q

Describe the structure and components of blood vessels

A

hollow tube made up of:

  • Lumen: central cavity where blood flows
  • Wall: made of layers (not all vessels have all 4 layers)
    1. inner lining: endothelial cells make up the endothelium (all vessels have inner lining)
    2. Elastic connective tissue: stretch and recoil, elastic proteins
    3. Vascular smooth muscle: vasoconstriction/dilation
    4. Fibrous connective tissue
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7
Q

List and describe the types of blood vessels:

A
  1. Artery: thick walled to withstand high BP (all 4 layers)
  2. Arteriole: smallest arteries, can adjust by vasoconstriction and dilation
  3. Capillary: smallest blood vessel: exchange of material
    - only endothelial layer cells
  4. Veins: transport blood at low pressure (all 4 layers)
  5. Venules: smallest veins
    - inner lining and fibrous connective tissue
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8
Q

TRUE OR FALSE:

Blood flows due to a pressure gradient between the arteries and veins

A

TRUE

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9
Q

What are factors affecting blood flow through the vessels of the body?

A
  1. myogenic autoregulation: stretch receptors in wall of arterioles when activated cause vasoconstriction (vascular smooth muscle)
  2. paracrine hormones: released from vascular endothelium and tissues causing either vasoconstriction or vasodilation
  3. Innervation by sympathetic division of ANS
    - N.E: binds to alpha receptors, cause vasoconstriction
    - E: binds to alpha receptors, reinforces vasoconstriction
  4. Hormonal signals via circulating epinephrine: binds to b2 receptors
    - found ONLY in vascular smooth muscles in heart, liver, and skeletal muscles
    - causes vasodilation
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10
Q

Explain the rs between pressure and volume in the circulatory system

A
  • when heart contracts, volume decreases, pressure increases
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11
Q

Where does friction occur in the circulatory system?

A

between the walls of the blood vessel and the blood (fluid)

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12
Q

Friction exerted by a tube is generally called ____

A

resistance

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13
Q

List the variables that contribute to calculating resistance of a fluid in a tube. Which of them are changed in the human body?

A 
L = length of the tube
n = viscosity of the fluid
r = radius of the tube

r is generally changed while L and n remain constant

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14
Q

TRUE OR FALSE:

Flow is proportional to resistance

A

FALSE: Flow is INVERSELY proportional to resistance

As resistance decreases, flow increases and vice versa

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15
Q

What does the arterial blood pressure reflect?

What does your pulse represent?

A

the driving pressure caused by the heart pumping

  • highest in arteries
  • lowest at point of return to the heart

the pulse represents an increase in pressure caused when ventricles contract and push blood in aorta

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16
Q

What are the 2 types of blood pressure?

A
  • systolic pressure: when heart contract, highest arterial pressure
  • diastolic pressure: when heart relaxes, lowest arterial pressure
17
Q

How do we estimate blood pressure?

A

Sphygmomanometry; use of BP cuff and stethoscope

18
Q

List the steps of sphygmomanometry

A
  1. Inflate cuff: cuts off blood flow
  2. cuff is gradually deflated, when pressure in cuff = systolic pressure, blood starts to flow
  3. turbulent flow results in sound (korotkoff)
  4. cuff pressure further reduced
  5. eventually all sound will cease because flow is no longer turbulent: diastolic pressure
19
Q

How is Mean Arterial Pressure calculated?

A

diastolic P + 1/3 (systolic P - diastolic P)

20
Q

What are factors affecting Mean Arterial Pressure?

A
  • cardiac output
  • changes in blood volume (normally constant)
  • peripheral resistance: controlled by arterioles
  • can modify diameter
  • small changes in radius = big changes in resistance
  • influenced by both local and reflex control mechanisms
21
Q

What regulates blood pressure?

A

coordination by CNS

  • sensory input from baroreceptors: sensitive to stretch mechanoreceptors found in vessel walls of:
  • carotid artery: monitors blood pressure to brain
  • aorta: monitors blood pressure to body
22
Q

What happens when there is an increase in blood pressure from normal (i.e. initial blood pressure is high)?

A
  • membrane of baroreceptors stretches
  • increases fire rate of receptor
  • AP travels to cardiovascular control centre of CNS (medulla)
  • control center integrates the sensory input
  • efferent output carried out by autonomic neurons
  • decrease in sympathetic output and increases in parasympathetic output
    causes: vasodilation, decrease in force of cardiac contraction and heart rate, decrease in peripheral resistance and cardiac output
  • results: decrease in BP
23
Q

What happens when there is a decrease in blood pressure from normal (i.e. initial blood pressure is low)?

A
  • baroreceptors decrease firing rate
  • fewer A.Ps travel to cardiovascular control center in CNS in medulla
  • control center integrates sensory input
  • efferent output carried out by autonomic neurons
  • increase in sympathetic output, decrease in parasympathetic output
  • causes: vasoconstriction, increase in force of cardiac contraction, increase in heart rate, increase in peripheral resistance, increase in cardiac output

BIOL 273 - Principles of Human Physiology 1 (24 decks)

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