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Physiology S2 > T3: Circulatory System (cont.) > Flashcards

T3: Circulatory System (cont.) Flashcards

1
Q

What is the normal blood flow rate of humans?

A

5L/min

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2
Q

What is the vital function of the cardiovascular system?

A

Chemical and gaseous exchange between blood and interstitial fluid.

across capillary walls

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3
Q

What is the function of capillaries?

A

transport gases, nutrients and waste products.

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4
Q

What are the three types of capillaries?

A
  • continuous
  • fenestrated
  • discontinuous
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5
Q

What is the function of continuous capillaries?

A
  • permit diffusion of water, small solutes and lipid soluble materials into the surrounding interstitial fluid
  • prevent the loss of blood and plasma cells
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6
Q

What is the function of fenestrated capillaries?

A

Exchange of water and solutes (as large as small peptides) between plasma and interstitial fluid.

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7
Q

Where are continuous capillaries located?

A

all tissues except:
- epithelia
- cartilage

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8
Q

Where are fenestrated capillaries located?

A
  • Kidneys: glomerulus
  • GI tract: gut
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9
Q

Where are sinusoidal capillaries located?

A
  • liver
  • bone
  • spleen
  • endocrine glands (pituitary, adrenal glands)
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10
Q

What is microcirculation comprised of?

A
  • arterioles
  • capillaries
  • venules
  • terminal lymphatic vessels
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11
Q

What is a precapillary sphincter? What is its function?

A
  • a circular band of smooth muscle at the entrance to the capillary
  • regulates number of perfused capillaries
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12
Q

How do substances pass through the capillary wall?

A
  • diffusion (O2, CO2)
  • filtration
  • osmosis
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13
Q

What is fluid movement across capillary walls determined by?

A
  • hydrostatic pressure
  • osmotic pressure
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14
Q

What is an arteriovenous anastomose? What is its function?

A
  • direct connections between arterioles and venules
  • allows blood to bypass the capillary bed and flow directly into the venous circulation
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15
Q

What is the function of capillary beds?

A

allow gas, nutrient and waste exchange

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16
Q

What is the function of arterioles (in relation to capillaries)?

A
  • regulate capillary hydrostatic pressure
  • influence capillary fluid exchange
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17
Q

How do venules play a role in regulating capillary hydrostatic pressure?

A

Sympathetic innervation of larger venules can alter venular tone which plays a role in regulating capillary hydrostatic pressure.

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18
Q

What is the function of valves?

A
  • keep blood flowing towards the heart
  • allow blood flow against the force of gravity
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19
Q

What is the colour of blood flowing through veins? Why?

A

deep red colour <– lacks oxygen

20
Q

What is turbulance?

A

The upset of smooth blood flow caused by:
- high flow rates,
- irregular surfaces
- sudden changes in vessel diameters
which increases resistance and slows the flow of blood.

21
Q

Where does turbulance usually occur?

A
  • between atria and ventricles
  • between ventricles and the aortic/pulmonary tunk
  • aorta (high flow rates)
  • small vessels (unless the wall is damaged–>plaque –> restricts blood flow)
22
Q

Is arterial pressure stable?

A

No!
- rises during ventricular systole
- falls during ventricular diastole

23
Q

What is a pulse?

A

The rhythmic pressure oscillation that accompanies each heartbeat.

24
Q

What is pulse pressure?

A

The difference between systolic and diastolic pressures.

25
Q

What is used to report a single blood pressure value?

A

a MAP (mean arterial pressure)

26
Q

What is hypertention?

A

abnormally high blood pressure

27
Q

What is hypotention?

A

abnormally low blood pressure

28
Q

What instrument is used to measure blood pressure?

A

sphygmomanometer (around arm)

29
Q

What factors are involved in the regulation of cardiovascular function?

A
  • local factors (AUTOREGULATION: chemical changes in interstitial fluid)
  • neural mechanisms (pressure changes or blood gas level changes)
  • endocrine mechanisms (releases hormones enhancing short term adjustments and direct long term changes)
30
Q

What is autoregulation? What does it cause?

A

causes immediate, localized homeostatic adjustments

31
Q

State examples of factors promoting autoregulation.

A
  • decreased O2 levels
  • increased CO2 levels
  • generation of lactic acid
  • release of nitric oxide (known as EDRF)
  • increased K+
  • increased H+
  • release of histamine
  • elevated local temperatures

EDRF- endothelium derived relaxation factor

32
Q

What neural centers are responsible for regulatory activities of the cardiac output?

A

Medulla Oblongata:
- cardiac centers
- vasomotor centers

33
Q

What does each cardiac center consist of? What are they innervated by?

A
  • cardioacceleratory center (sympathetic innervation)
  • cardioinhibitory center (parasympathetic innervation)
34
Q

What does the neurotransmitter norepinephrine (NE) cause?

A
  • stimulation of smooth muscle cells (arteriole walls)
  • vasoconstriction
35
Q

What neurotransmitter causes vasoconstriction?

A

norepinephrine (NE)

36
Q

How do vasodilator neurons function?

A
  • innervate blood vessels in skeletal muscles and brain
  • stimulation of vasodilator neurons relaxes smooth muscle cells (arteriole walls)
37
Q

What is vasodilation triggered by?

A

appearance of NO in the surroundings

38
Q

What are the most common vasodilator synapses? What do they release? What does it cause?

A

Cholinergic:
- releases ACh
- ACh stimulates NO release
- local vasodilation achieved

Nitroxidergic:
- release NO
- local vasodialtion

39
Q

What do baroreceptor reflexes respond to?

A

changes in blood pressure

40
Q

What do chemoreceptor reflexes respond to?

A

changes in the chemical composition of arterial blood

41
Q

What are baroreceptor and chemoreceptor reflexes regulated through?

A

negative feedback loop

42
Q

Where are baroreceptors involved in cardiovascular regulation located?

A
  • carotid sinuses (regulate blood flow to the brain)
  • aortic sinuses (regulate blood flow through the systematic circuit)
43
Q

What happens when blood pressure falls below normal?

A
  • cardiac output increase (stimulation of heart sympathetic innervation)
  • widespread peripheral vasoconsriction (stimulation of sympathetic vasoconstrictor neurons (by vasomotor centers))
44
Q

What is the function of the antidiuretic hormone (ADH)?

A
  • stimulates water conservation at the kidneys
  • prevents a reduction in blood volume (which would reduce blood pressure)
45
Q

What is the function of the angiotensin II?

A
  • stimulates ADH secretion, Na+ retention, K+ loss, aldosterone production
  • stimulates thirst (increased fluid consumption)
  • stimulates cardiac output
  • triggers vasoconstriction of arterioles

Elevates systemic blood pressure.
- 4-8x more than norepinephrine

46
Q

What does venous return depend on?

A
  • skeletal muscle action
  • respiratory movements
  • constriction of smooth muscle in venous walls
47
Q

Compare the “laminar” and “turbulent” blood flow.

A

Laminar flow is linear flow, mainly found in the middle of the vessel. Turbulent flow is any disruption in the laminar flow.

Physiology S2 (17 decks)

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