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Circulatory physiology Flashcards

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1
Q

Distribution of cardiac output

Blood flow

F = ΔP
_______
R

A
  • Blood flow is adjusted depending on metabolic need
  • exercise: heart and muscle
  • NEEDS gradient, bigger gradient = more flow
    -From higher to lower pressure
  • directly proportional to pressure gradient

F = flow rate of blood through a vessel
ΔP = pressure gradient
R = resistance of blood vessels

  • Pressure not important just gradient for flow
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2
Q

Pressure change

A
  • Driving pressure for systemic flow is
    created by LV
  • If blood vessels constrict, BP↑
  • diameter is biggest factor
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3
Q

resistance with bloodflow

what does it depend on

radius relationship

R is proportional to l x ρ
_____
r4

A
  • measure of opposition to blood flow

-Blood viscosity, ρ
* vessel length, l
* vessel radius , r (major
determinant – biggest effect)

  • radius up then blood flow up and resistance down
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4
Q

Effect of vessel radius

effect of viscosity

A

Eg. If vessel radius decreases by a factor of 2, Flow would decrease by a factor of 16 (r4)

Thus - Vessel vasoconstriction and
dilation controls flow

  • Increased viscosity will decrease blood flow
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5
Q

Vascular tree

A

Consists of
-Arteries
-Arterioles
-Capillaries
-Venules
-Veins
- Lymph Vessels

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6
Q

Vasculature

A

Layers:

Tunica Intima
* Endothelium: controls vasconstriction, prevents clotting

Tunica Media
* Smooth muscle

Tunica Externa
* Connective tissue

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7
Q

Variance in blood vessels

Comparison of vessel cross section in terms of velocity and pressure

A

Arterioles
-Highest proportion of smooth muscle

Capillaries
-single layer of endothelium

Arteries
-Reinforced with collagen and elastin

Ex: Slow capillary flow = gas exchange

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8
Q

Arteries
Pressure/Radius

What is constant in arteries

Pressures

Parts of arteries for function

A

High flow rate / High pressure
* Large radius (low resistance)
-pulsating flow

Pressure reservoir when heart is relaxing

Systolic pressure of ~120
Diastolic pressure of ~80 mmHg

Collagen fibers
* tensile strength
Elastin fibers
* Stretch / Recoil of walls

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9
Q

Atheroscleriosis

A

Is caused by the buildup of cholesterol within arteries
-plaque/fat build up

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10
Q

Arterioles

  • what is job

Major resistance vessels
Radius can be adjusted to:

Vasoconstriction

Vasodilation

A

Major resistance vessels

-Distribute cardiac output among organs, depending on body’s needs
-Help regulate arterial blood pressure
-acts to smooth out pulsatile flow

-narrowing of vessel (↑ resistance)
* Contraction of smooth muscle
* Reduced flow, at rest

-enlargement (↑ radius) of vessel
* relaxation of smooth muscle
* ↓ resistance and ↑ flow

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11
Q

Blood supply

A
  • Only blood supply to brain
    remains constant

-Blood supply to other organs
alter via arteriole radius

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12
Q

Factors affecting vascular tone:

Local influences

Local physical influences

A

-Local metabolite changes
-Histamine release
-Endothelial factors
* Nitric oxide, EDRF, Endothelin

-heat (dilates) or cold (constricts)
-Myogenic response to stretch
* Reflex contraction

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13
Q

Arterioles: Vasodilation occurs with

A

-Decreased O2
-Increased CO2
-Increased acid
-Increased K+
-Increased osmolarity
-Adenosine release
-Nitric Oxide
-Heat

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14
Q

Arterioles - extrinsic control

A

-Sympathetic input
- Hormones

Alpha 1 Receptors
* Norepinephrine
* Vasoconstrictor vessels

Beta 2 Receptors
* Epinephrine
* Heart / skeletal muscle
* Vasodilate

Angiotensin II
* vasoconstricts

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15
Q

Capillaries purpose

Why thin walled?

Small radius because

why extensively branched

Types:

Continuous

Fenestrated

Sinusoids

A
  • site for gas exchange

-Thin-walled, ↓ diffusion distance

-Small radius, velocity of blood
flow is slow
- gas exchange time ↑

-Extensively branched, ↑ surface area

-most common
* Least permeable
* Muscle, lungs, brain, CT

  • have pores
  • Kidneys, Small intestine
  • Large clefts for RBCS, proteins
  • Liver, bone marrow, spleen
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16
Q

Pre capillary sphincters

constrict sphincter

relax sphincter

Metarteriole

Study These Flashcards
A

Constrict sphincter – close capillary bed
At rest, many capillaries are not open

Relax sphincter – opens capillary bed

-Runs between an arteriole and a venule

17
Q

Capillary bulk flow - Starling forces that determine the fluid flow between tissue and capillary

Study These Flashcards
A

Capillary blood pressure
* hydrostatic pressure
* Encourages fluid flow into tissue

Interstitial fluid hydrostatic pressure (PIF)
* Opposes hydrostatic pressure
Plasma colloid osmotic pressure (πCAP)
* Encourages movement of fluid into capillary

Interstitial fluid colloid osmotic pressure (π IF)
* Opposes plasma colloid osmotic pressure

18
Q

Fluid exchange at capillary

Hydrostatic pressure

colloid osmotic pressure

net pressure

arterial vs venous end of capillary

Study These Flashcards
A
  • Hydrostatic pressure and osmotic pressure regulate bulk flow
  • hydrostatic pressure forces fluid out of capillary

-osmotic pressure of proteins within capillary pulls fluid in

= hydrostatic - colloid osmotic pressure

  • arterial end has higher pressure
  • Plasma colloid osmotic pressure stays the same but capillary hydrostatic pressure decreases as it goes from arterial to venous
19
Q

Lymphatic system

what are properties of the vessels

function of the system of vessels

Study These Flashcards
A

Network of open-ended vessels
- Helps drain fluid from tissues

-Similar in structure to veins
-Low pressure
-Have valves

-Return of excess filtered fluid
-Defense against disease
* Lymph nodes (phagocytes)
-Transport of absorbed fat
-Return of filtered protein

20
Q

Edema - what happens and why

cause of edema

Study These Flashcards
A

-Swelling of tissues
-Occurs when too much interstitial fluid
accumulates

-Reduced concentration of plasma proteins
-Increased permeability of capillary wall
-Increased venous pressure
- Blockage of lymph vessels, cannot drain

21
Q

Venules - how formed and what they do

Study These Flashcards
A

-Formed when capillary beds unite

Very porous
-allow fluids and WBCs into tissues

Larger venules have one or two layers of smooth muscle cells

22
Q

Veins - job and properties

how it works

radius

Study These Flashcards
A

-Return to heart, deoxygenated blood
-Low pressure, low resistance
-Slow flow

Capillaries drain into venules
* Smaller venules merge to form larger vessels

  • Large radius (low resistance to blood flow)
    -Serves as blood reservoir
23
Q

what is venous return

decreased by

Increased by

Study These Flashcards
A

-the flow of blood from the body’s veins back to the heart’s right atrium

  • Venous compliance (decreases return)

-Driving pressure from cardiac contraction
-Sympathetically induced venoconstriction
-Skeletal muscle activity
-Effect of venous valves
-Respiratory activity
-Effect of cardiac suction

24
Q

factors that influence venous return

venous valves

-skeletal pump

varicose veins

Study These Flashcards
A
  • cardiac output, stoke volume, end diastolic volume

-Prevent back-flow

-pushes blood upward

-Weak valve – allows back-flow
-Blood stagnates and clots

25
Atherosclerosis what is atheromas what happens what lifestyles lead to atheromas what are the risks how to treat
- fatty plaques within vessel walls , that can harden into plaques and restrict blood flow (thickening of the wall) - lead to clot formation or - stiffer blood vessels so faster flow and high blood pressure - obesity/ inactivity, smoking, alcohol, genetics, diabetes -also happens with aging -atheroclerosis leads to risks of cardiac ischemia, infarct and strokes - treated with exercise, diet changes, bp medication and anti coagluants
26
Peripheral vascular disease what is it - what are consequences - lifestyle choices leading to this
- Decreased flow to the peripheral vessels. Plaques, clots, vascular spasm - Can cause pain, fatigue, poor circulation -Can lead to heart attack, stroke, or tissue necrosis (amputation) – obesity, diabetes, smoking, high cholesterol etc
27
-Deep vein thrombosis - How do they form what is needed
- Thrombus / Thrombi -Blood clots. Pain, redness, swelling -Can form if blood is not moving Eg. Restrictive clothing, plane flights - Need anti-coagulants
28
Aneurysms - ball in the wall - what happens if ruptures in brain
Fusiform - both side Saccular - one side Dissection -strokes
29
Aortic dissection - what happens what can this lead to dissection surgery
- Where the inner wall of the aorta gets a split. Allows blood into site -Outer wall pulls away and “balloons” due to high pressure -The force of blood within the “balloon” causes the aortic dissection to spread -Risk of rupture Stents – smaller segments, replace aortic wall Grafts - aortic arch replacment if bad
30
Embolism - blockage of a blood vessel (moving clot) what is it locations
- Sudden blockage of a blood vessel (Blood clot) - from Fat deposits, tissue fragments, cancer cells, clumps of bacteria, bubbles of air -Pulmonary embolism—chest pain, shortness of breath ▪ Cerebral embolism—may cause a stroke ▪ Cardiac embolism—may cause a heart attack
31
Strokes what happens reasoning for stoke types (TIA and CVA) symptoms
- ↓ blood supply to brain Ischemic (87%, most common) * Due to thrombus or embolus or plaque blockage Haemorrhagic (13%) * Bleeding (week wall rupture) TIA’s - transient ischemic attacks (Mini-strokes) CVA- permanent damage (big stroke) -Drooping face, Confusion, Dizziness, Sudden loss of consciousness, Poor coordination, Arm weakness, Sudden headache, Difficulty with speech, Loss of vision
32
Stroke - CVA and TIA Controllable Risk factors: Non-controllable: CVA facts Assessment treatment
- 80% of all strokes are preventable - Smoking / Alcohol High-fat diet / Obesity Lack of exercise High blood pressure Diabetes -Age, gender, ethnicity genetics - EEG, CT scan, and MRI Angiogram, Doppler flow * Anticoagulants * Hypertensive meds * Carotid endarterectomy * Change diet * Exercise regime
33
Blood pressure Primary determinants Short term control: Long term control:
-Cardiac output -Total peripheral resistance -Mean arterial pressure = cardiac output x total peripheral resistance Within seconds Baroreceptors Cardiovascular system Minutes to hours Kidneys - look at slide 70
34
Short term control - baroreceptors - carotid sinus receptors - aortic arch receptors Pressure receptors Response to low blood pressure what happens what triggers
Fast control - cardiovascular -Send input to cardiovascular centre -Output to heart and blood vessels - look at slide 71-74 - ↓ firing of baroreceptors (*) To Cardiovascular centre ↑ vasoconstriction and venoconstriction ↑ contractility so ↑ stroke volume ↑ heart rate These increase cardiac output – so ↑ blood pressure
35
- Long term mechanisms: renal regulation Kidneys ( hormone and urine control) Direct renal mechanism Indirect renal mechanism:
-Control BP by altering blood volume - Direct renal mechanism -Indirect renal (renin-angiotensin) mechanism -Alters blood volume independently of hormones. Increased BP or blood volume * Increased filtration, causes the kidneys to eliminate more urine, thus reducing BP - Decreased BP or blood volume causes the kidneys to conserve water, and BP rises -The renin-angiotensin mechanism Controls blood volume and arterioles
36
Renin-Angiotensin System
-Decreased arterial blood pressure → release of renin - Renin→ triggers production of angiotensin II * potent vasoconstrictor Angiotensin II → aldosterone and ADH secretion * Conservation of Fluid
37
High BP abnormalities -Hypertension Primary hypertension Secondary hypertension
-Blood pressure above 140/90 mm Hg Two broad classes - Potential causes: Excessive salt intake or hormones, Abnormalities in arterioles, Poor kidney function (RAAS), Age / genetics, Stress, Smoking, Diet / obesity -Accounts for about 10% of hypertension cases -Occurs secondary to another known primary problem -Examples of secondary hypertension * Renal hypertension * Endocrine hypertension * Neurogenic hypertension
38
Hypertension Complications and treatments Complications: Treatments:
-Congestive heart failure Stroke / Heart attack Spontaneous hemorrhage Renal failure Retinal damage -ACE inhibitors, beta blockers, Ca blockers, Diet, exercise
39
High BP abnormalities - Hypotension what happens - symptoms circulatory shock - what is it four main types
-Blood pressure below 100/60 mm Hg -Low blood pressure -There is too little blood to fill the vessels - Heart is too weak to drive the blood -Dizziness, fainting, blurry eyes, confusion, palpitations -Alcohol may make it worse (RAAS) - Occurs when blood pressure falls so low that adequate blood flow to the tissues can no longer be maintained * Hypovolemic (“low volume”) shock * Cardiogenic (“heart produced”) shock * Vasogenic (“vessel produced”) shock * Neurogenic (“nerve produced”) shock

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