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Human physiology > Blood vessels + circulation > Flashcards

Blood vessels + circulation Flashcards

1
Q

Describe the tunica interna of the artery wall

A
  • smooth squamous endothelium
  • has basement membrane
  • contains internal elastic lamina
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2
Q

Describe the tunica media of the artery wall

A
  • thickest layer
  • elastic fibres
  • smooth muscle
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3
Q

Describe the tunica externa of artery walls

A
  • elastic + collagen fibres
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4
Q

List the functions of elastic (conducting) arteries

A
  • largest diameter arteries
  • carry blood away from the heart
  • store elastic energy which helps move blood during diastole
  • pressure reservoir
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5
Q

List the functions of muscular (distributing) arteries

A

Medium sized arteries
- distribute + regulate blood flow to muscles + internal organs (constrict + dilate)
- superficial muscular arteries form pressure points (eg. control bleeding/measure pulse) -> carotid, brachial, femoral

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6
Q

Describe the functions of arterioles

A
  • deliver blood to capillaries
  • regulate systemic vascular resistance through vasoconstriction + vasodilation
  • resistance vessels
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7
Q

Describe the function + structure of meta arterioles

A
  • supply capillary beds
  • distal end has no smooth muscle -> thoroughfare channel
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8
Q

Describe the structure + function of capillaries

A
  • walls consist of only endothelium + basement membrane
  • exchange of nutrients + waste via interstitial fluids (exchange vessels)
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9
Q

Describe true capillaries + what their flow is regulated by

A
  • emerge from arterioles + meta arterioles
  • flow regulated by pre capillary sphincter
    -> intermittent flow caused by alternating contraction/relaxation of meta arterioles + pre capillary sphincters
    -> RBCs move single file through capillary
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10
Q

List the 3 types of capillaries + their characteristics

A

continuous capillaries
- uninterrupted lining
- most common

fenestrated capillaries
- many fenestrations/pores
- found in kidney

sinusoidal capillaries
- large fenestrations + intercellular clefts
- incomplete basement membrane
- found in liver, spleen + bone marrow
-> enable drugs to be metabolised

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11
Q

Describe what venules are formed from

A

small veins formed from merging of several capillaries -> merge to form veins

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12
Q

Describe the 3 tunics of veins + their characteristics

A
  • tunica interna thinner
  • tunica media thinner -> less smooth muscle + elastic fibres
  • tunica externa -> collagen = elastic fibres / lack elastic lamina of arteries
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13
Q

What are the functions of veins

A
  • hold 60% of blood volume
  • capacitance vessels (volume reservoir)
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14
Q

Define blood flow

A

volume of blood that flows through a tissue per unit time
-> determined by blood pressure + resistance

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15
Q

Describe the conditions required for blood flow

A

circulatory pressure must be greater than total peripheral resistance (where TPR is determined by vascular resistance, blood viscosity + turbulence)

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16
Q

What factor determines blood viscosity

A

ratio of RBC to plasma

17
Q

Define turbulence + the factors which affect it

A
  • the slowing of blood flow
  • high flow rates, irregular surfaces eg. plaque build up, + sudden changes in vessel diameter -> all increase turbulence
18
Q

What is the relationship b/t velocity of blood flow + CSA + how does this change through the vessels

A
  • velocity inversely related to CSA
    -> velocity decreases as blood flows from aorta to capillaries
    -> velocity increases as blood flows from capillary to heart
19
Q

Why is velocity of blood flow slowest in capillaries

A

allows increased time for exchange

20
Q

Define blood pressure

A

Pressure exerted on walls of a blood vessel
-> decreases as moves further away from the heart

21
Q

What is venous return maintained by

A
  • pressure gradient est. by heart
  • skeletal muscle pumped
  • respiratory pump
  • valves
22
Q

List 3 things that occur if blood pressure is too low

A
  • vessels collapse
  • blood flow stops
  • tissues die
23
Q

list 2 things that happen if blood pressure is too high

A
  • vessel walls stiffen
  • capillary beds rupture
24
Q

List the 3 methods substances can enter + leave the capillaries by

A
  1. diffusion (most important)
  2. transcytosis (vesicular transport) -> lipid soluble across membrane
  3. bulk flow (filtration + absorption)
25
Q

Why is capillary exchange important + what drives it

A
  • regulates relative volumes of blood + interstitial fluid
  • driven by balance b/t hydrostatic + osmotic pressures (net filtration pressure)
26
Q

List the 3 mechanisms controlling cardiovascular regulation

A
  1. autoregulation
  2. neural mechanisms
  3. hormonal mechanisms
27
Q

Describe how autoregulation occurs through local factors + what is affected by this

A

local factors = alter pattern of blood flow through capillaries via local vasoconstrictors or local vasodilators
-> act on pre capillary sphincters to control blood flow through a single capillary bed

28
Q

List 4 local vasodilators

A
  • increased tissue CO2 or decreased O2
  • lactic/other acid from tissue cells
  • chemicals released during inflammation eg. histamines
  • elevated local temp
29
Q

what is an example of a local vasocontrictor

A

prostaglandins from activated platelets

30
Q

explain the negative feedback loop that occurs that has vasodilation as the effect

A
  • homeostasis disturbed by physical stress (increased temp), chem. changes or increased tissue activity
  • causes inadequate local blood flow/BP
  • results in local decrease in resistance + increase in blood flow
  • homeostasis restored
31
Q

state where neural control happens from + what it changes

A
  • neural control via cardiac centres + vasomotor centres in medulla oblongata
    -> changes HR, contractility + resistance of blood vessels (affects CO)
32
Q

List the 4 areas the cardiovascular system receives input from

A
  • higher brain regions eg. hypothalamus
  • proprioceptors
  • baroreceptors (monitor BP)
  • chemoreceptors (monitor blood acidity)
33
Q

what 2 mechanisms does the cardiovascular centre send outputs via

A

sympathetic impulses :
- cardio accelerator nerves (increase HR and contractility)
- vasomotor nerves (cause vasoconstriction + vasodilation)

parasympathetic impulses:
- vagus nerve decreases HR

34
Q

Explain the function + location of baroreceptors

A

function = monitors degree of stretch of blood vessels
-> BP falls when stretched less therefore send impulse to CV centre

location = carotid sinus + aorta

35
Q

Explain the response to increased baroreceptor stimulation when BP increases

A
  • homeostasis disturbed by increased BP
  • baroreceptors stimulated
  • cardio inhibitory centre stimulated = decrease CO
  • cardio accelatory + vasomotor centres inhibited = vasodilation occurs

-> homeostasis restored + BP decreases

opposite for decreased BP

36
Q

list the 4 hormones produced by the endocrine system to regulate the CV system + describe their functions

A

E + NE from adrenal medulla = increase CO + peripheral vasoconstriction

ADH from posterior pituitary= increase peripheral vasoconstriction -> increase BP

Angiotensin 2 = causes vasoconstriction -> increases BP

Erythropoietin from kidneys = stimulates RBC production in bone marrow

37
Q

list the 3 CV responses to exercise

A
  • extensive vasodilation
  • increased venous return
  • increased CO via increased venous return + increased sympathetic activity

Human physiology (12 decks)

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