Circulatory Physiology Flashcards Preview

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Flashcards in Circulatory Physiology Deck (46)
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1
Q

Distribution of cardiac output at rest

A

Blood flow is adjusted depending on metabolic need

2
Q

Blood flow

A

From higher to lower pressure
Directly proportional to pressure gradient
Inversely proportional to vascular resistance
F=🔺P/R
F = flow rate of blood through a vessel
P = pressure gradient
R = resistance of blood vessels

3
Q

Pressure change

A

Driving pressure for systemic flow is created by LV

If blood vessels construct = BP increases

4
Q

Resistance

A

Measure of opposition to blood flow
Depends on = blood viscosity (p), vessel length (1), vessel radius(r) (biggest effect)
R = 1xp/r^4

5
Q

Effect of vessel radius

A
If vessel radius decreases by a factor of 2, flow would decrease by a factor of 16
Decrease radius (vasoconstrict) = increased resistance, decreased flow 
Increase radius (vasodilate) = decreases resistance, increased flow 
Thus vessel vasoconstriction and dilation controls flow
6
Q

Vascular tree

A

Consists of = arteries, arterioles, capillaries, venules, veins, lymph vessels

7
Q

Vasculature

A

Layers = connective tissue, smooth muscle, endothelium

8
Q

Arteries

A

High flow rate/high pressure
Large radius (low resistance)
Pressure reservoir when heart is relaxing
Collagen fibres (tensile strength), elastin fibres (stretch/recoil of walls)
Pulsatile flow
Systolic pressure ~120, Diastolic pressure ~80

9
Q

Atherosclerosis

A

Cardiovascular disease

Caused by cholesterol buildup within arteries

10
Q

Arterioles

A

Major resistance vessels
Acts to smooth out pulsatile flow
Radius can be adjusted to: distribute cardiac output among organs depending on bodies need, help regulate arterial blood pressure

11
Q

Only blood supply to _______ remains constant

A

Brain

Blood supply to other organs alter via arteriole radius

12
Q

Vasoconstriction

A

Narrowing of vessel (increased resistance)

Contraction of smooth muscle

13
Q

Vasodilation

A

Enlargement of vessel
Relaxation of smooth muscle
Decreased resistance
Increased flow

14
Q

Factors affecting vascular tone

A

Local influences = local metabolic changes, histamine release, endothelial factors (nitric oxide, EDRF, endothelin)
Local physical influences = heat or cold, myogenic response to stretch

15
Q

Arterioles (vasodilation occurs with:)

A
Decreased oxygen 
Increased carbon dioxide 
Increased acid 
Increased potassium 
Increased osmolarity
Adenosine release 
Prostaglandin release
16
Q

Extrinsic control

A

Sympathetic input
Hormones
Alpha 1 receptors = norepinephrine (vasoconstriction)
Alpha 2 receptors = epinephrine, heart/skeletal muscles (vasodilation)

17
Q

Capillaries

A
Thin walled (decrease diffusion distance)
Small radius (velocity of blood flow is slow, gas exchange time increases)
Extensively branched (increased surface area)
Site of gas exchange
18
Q

Pre-capillary sphincters

A

Constrict sphincter = closes capillary bed (many capillaries are not open at rest)
Relax sphincter = opens capillary bed
Met arterioles = runs between an arteriole and a venule

19
Q

Capillary types

A
Continuous = most common, least permeable, (muscle, lungs, brain, CT)
Fenestrated = have pores, (kidneys, small intestine)
Sinusoids = large clefts for RBCs, proteins, (liver, bone marrow, spleen)
20
Q

Capillary bulk flow

A

Sterling forces that determine fluid flow between tissue and capillary
Capillary blood pressure
Interstitial fluid hydrostatic pressure (Pif)
Plasma colloid osmotic pressure (pi cap)
Interstitial fluid colloid osmotic pressure (pi if)

21
Q

Capillary blood pressure

A

Hydrostatic pressure

Encourages fluid flow into tissue

22
Q

Interstitial fluid hydrostatic pressure

A

Opposes hydrostatic pressure

23
Q

Plasma colloid osmotic pressure

A

Encourages movement of fluid into capillary

24
Q

Interstitial fluid colloid osmotic pressure

A

Opposes plasma colloid osmotic pressure

25
Q

Hydrostatic pressure and osmotic pressure regulate…

A

Bulk flow

26
Q

Lymphatic system

A

Network of open-ended vessels (helps drain fluid from tissues)
Lymph vessels = similar in structure to veins, low pressure, have valves
Functions = return of excess filtered fluid, defence against disease, (lymph nodes = phagocytes), transport of absorbed fat, return of filtered proteins

27
Q

Edema

A

Swelling of tissues
Occurs when too much interstitial fluid accumulates
Causes = reduced concentration of plasma proteins, increased permeability of capillary wall, increased venous pressure, blockage of lymph vessels

28
Q

Venules

A

Formed when capillary beds unite
Very porous (allows fluids and WBCs into tissues)
Larger venules have one or two layers of smooth muscles

29
Q

Veins

A
Return to heart 
Low pressure 
Low resistance 
Larger radius
Slow flow 
Serves as a blood reservoir 
Capillaries drain into venules (smaller venules merge to form larger vessels)
30
Q

Venous return

A

Decreased by = venous compliance
Increased by = driving pressure from cardiac contraction, sympathetically induced venoconstriction, skeletal muscle activity, effect of venous valves, respiratory activity, effect of cardiac suction
Venous valves = prevent backflow
Skeletal pump = pushes blood upward

31
Q

Varicose veins

A

Weak valve = allows backflow

Blood stagnates and clots

32
Q

Blood pressure is determined by

A

Cardiac output and total peripheral resistance

Mean arteriole pressure = cardiac output x total peripheral resistance

33
Q

Blood pressure control

A

Short term = within seconds, baroreceptors, cardiovascular system
Long term = minutes to hours, kidneys

34
Q

Short term control - baroreceptors

A

Fast control = cardiovascular

Pressure receptors = send input to cardiovascular centre, output to heart and blood vessels

35
Q

Response to low blood pressure

A

Decrease firing of baroreceptors to cardiovascular centre
Triggers = increase in vasoconstriction and venoconstriction, increase contractility so stroke volume increases and heart rate increases
These things increase cardiac output = increases blood pressure

36
Q

Long term mechanisms: renal regulation

A

Control blood pressure by altering blood volume

Kidneys = direct renal mechanism, indirect renal (renin-angiotensin) mechanism

37
Q

Direct renal mechanism

A

Alters blood volume independently of hormones
Increased blood pressure or blood volume (increased filtration, causes kidneys to eliminate more urine thus reducing blood pressure)
Decreased blood pressure or blood volume causes the kidneys to conserve water and blood pressure rises

38
Q

Indirect (renin-angiotensin) mechanism

A

Decreased arteriole blood pressure = release of renin
Renin triggers production of angiotensin ll (potent vasoconstrictor)
Angiotensin ll = aldosterone and ADH secretion (conservation of fluid)

39
Q

Blood pressure abnormalities

A

Hypertension and hypotension

40
Q

Hypertension

A

Blood pressure above 140/90 mm Hg

Two broad classes = primary hyper tension and secondary hypertension

41
Q

Primary hypertension

A
Potential causes = 
poor kidney function
Excessive salt intake or hormones 
Na+ K+ or Ca++ imbalance (eg- defective Na+/K+ pumps)
Abnormalities in arterioles 
Stress 
Smoking
42
Q

Secondary hypertension

A

Accounts for 10% of hypertension cases
Occurs secondary to another known primary problem
Examples - renal hypertension, endocrine hypertension, neurogenic hypertension

43
Q

Complication of hypertension

A
Congestive heart failure 
Stroke 
Heart attack 
Spontaneous hemorrhage 
Renal failure 
Retinal damage
44
Q

Hypotension

A

Blood pressure below 100/60 mm Hg
Low blood pressure
Occurs when = there is too little blood to fill the vessels, heart is too weak to drive the blood

45
Q

Orthostatic (postural) hypotension

A

Transient hypotension condition resulting from insufficient compensatory responses to gravitational shifts in blood when person moves from horizontal to vertical position

46
Q

Hypotension (circulatory shock)

A
Occurs when blood pressure falls so low that adequate blood flow to the tissues can no longer be maintained 
Four main types =
Hypovolemic (low volume) shock 
Cardiogenic (heart produced) shock 
Vasogenic (vessel produced) shock 
Neurogenic (nerve produced) shock