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Animal Physiology: Homeostasis > Week 4 > Flashcards

Week 4 Flashcards

1
Q

Vascular structure of viens

A
  • Lowest pressures
  • thin muscled walls
  • highly distensible
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2
Q

Vascular structure of arteries

A
  • Highest pressures
  • Strong muscular walls
  • low flow resistance
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3
Q

Vascular structure of microcirculation

A
  • Arterioles are main site of vascular resistance
  • Capillaries and venules are sites of exchange
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4
Q

calculating vascular compliance

A

change in volume over change in pressure

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5
Q

Vascular compliance in the veins

A
  • Highly compliant
  • Small changes in pressure cause large changes in volume
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6
Q

Vascular compliance in arteries

A
  • less compliant than veins
  • still respond to increase in pressure with slight increases in volume
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7
Q

Aortic Complience

A
  • High systolic pressure expands the volume of the aorta
  • stretching stores potential energy
  • aortic walls recoil during diastole, squeezing the blood and helping maintain aortic pressure and blood flow
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8
Q

Aortic Pulse Pressure

A
  • Systolic pressure usually similar to that in left ventricle
  • Pulse pressure= SP - DP
  • Pulse pressure magnitude determined by stroke volume and arterial compliance (PP proportional to SV/Compliance)
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9
Q

Why is a dicrotic notch observed in pulse pressure

A

Closure of the aortic valve prevents any possible back flow

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10
Q

Aortic Valve Stenosis definition and effect

A
  • A condition in which the diameter of the aortic valve opening is reduced, which reduces flow into aorta
  • Increased resistance = decreased SV = decreased pressure
  • Smaller systolic pulse pressure
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11
Q

Aortic Regurgitation definition and effect on pulse pressure

A
  • the aortic valve does not close completely and blood flows back into the ventricle in late systole and diastole
  • decrease pressure in diastole due to faster decrease in blood volume
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12
Q

Transmission of pressure pulse through the arteries

A
  • Pressure (and flow) oscillations are transmitted along the arteries
  • The pressure decreases progressively in smaller arteries due to VESSEL COMPLIANCE and VASCULAR RESISTANCE
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13
Q

Arterial wall tension

A
  • Def: Force needed to resist the outward push of hydrostatic pressure
  • Calculation: T(tension) = Transmural pressure (r/h(wall thickness))
  • Vessels with larger radius and/or higher pressures have stronger walls with more smooth muscle and are reinforced with fibrous bands of collagen
  • high transmural pressure and radius leads to significant wall tension
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13
Q

Transmural pressure

A

Internal (intravascular) pressure - External (tissue) pressure

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14
Q

Effect of chronic increase in blood pressure on wall thickness

A

Causes remodeling increasing vessel wall thickness and reducing radius

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15
Q

Purpose of high compliance in venous system

A
  • Helps keep the pressure in the venous system low
  • can accommodate large changes in blood volume with only small changes in pressure
  • Acts as a blood reservoir ( volume can be controlled via changes in vascular tone, shifting blood to/from other parts of the circulation)
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16
Q

Venous blood reservoir

A

Blood in reservoir can be redistributed to perfuse more/fewer capillary beds as necessary

17
Q

Central Venous pressure

A
  • Diastolic pressure in the right atrium
  • normally very low (0 mmHg) but can vary with changes in EDV
  • increases in pressure stimulate heart pumping via intrinsic mechanisms (Frank-starling)
  • increases in atrial pressure can reduce atrial filling leading to back up because of a decrease in pressure gradient
18
Q

Gravity and the venous system

A
  • Hydrostatic pressure is affected by gravity and increases with fluid height
  • Gravity tends to increase venous pressure in the lower extremities)
19
Q

Venous Valves

A
  • assure blood only flows back toward the heart
  • helps control pressure increases due to gravity
20
Q

Venous muscle pump

A

Muscle contraction squeezes the veins and thus pushes blood out of that section of vein back toward the heart

21
Q

Functions of microcirulation

A

Transport nutrients to the tissues and remove cell waste

22
Q

Muscle of Arterioles

A

Arterioles are highly macular and control blood flow based on signals from local tissuee

23
Q

Capillaries

A

think-walled vessels where most blood-tissue exchange happens
- most cells are generally within 50um of a capillary

24
Q

Branching in vascular networks

A
  • Arteries branch 6-8 times to arterioles
  • arterioles branch 2-5 times to metarterioles (each of which supplies a capillary network)
  • branching increases total cross-sectional area, slowing the blood and maximizing time for exchange
25
Q

Blood Capillary Structure

A
  • Single layer of endothelial cells surrounded by basement membrane
  • intercellular clefts between endothelial cells allow water, ions and small solutes to cross
  • Caveolae are believed to play a role in endocytosis and transcytosis of large macromolecules across the interior of the endothelial cell
26
Q

Flow of gases through capillaries

A

Driven by partial pressure gradient
- can permeate surface
- O2 in and CO2 out

27
Q

Flow of lipid soluble substances through capillaries

A

driven by concentration gradient
- can permeate capillary surface
- moves substance inward

28
Q

Flow of small water-soluble solutes through capillaries

A

driven by concentration gradient
- must pass through intracellular cleft

29
Q

Flow of water-soluble proteins through capillaries

A

Must use membrane transport proteins or transcytosis to move through surface

30
Q

Water movement across blood capillaries

A
  • Water flow is determined by the combination of hydrostatic pressure and osmotic pressure
31
Q

Hydrostatic pressure gradient in the capillaries

A

Capillary pressure (Pc) > Interstitial pressure (Pif)
- Flow out of vessel

32
Q

Osmotic Pressure gradient in the capillaries

A

Plasma Colloid osmotic pressure (PIp) > Interstitial fluid colloid osmotic pressure (PIif)

33
Q

Colloid Osmotic pressure

A

The osmotic pressure that arises from the effects of the water soluble plasma proteins that cannot easily cross the endothelium

34
Q

Net filtration pressure (NFP)

A

NFP= (Pc - Pif) - (Pip - Piif)
- Flow from blood to interstitial fluid called filtration (positive NFP)
- Flow from interstitial fluid to blood is called absorption (negative NFP)
- Filtration is slightly higher than absorption in most capillary beds

35
Q

Capillary characteristics in the brain

A

Blood brain barrier
- Intracellular clefts are closed by tight junctions that only allow small uncharged molecules to pass

36
Q

Capillary characteristics in the glomerular capillaries

A

Kidneys have channels through cells so small molecules and ions can pass much easier (high rates of filtration)

37
Q

Capillary Characteristics in the liver

A

intercellular clefts are wider to allow larger macromolecules to pass
- due to liver’s role in nutrient processing

38
Q

Lymph Vessels

A
  • Highly permeable
  • junctions between adjacent endothelial cells can flap open and closed allowing fluid to flow in
39
Q

Lymph flow

A
  • interstitial fluid pressure drives fluid into lymph capillaries
  • increases in Pif will drive an increase ink lymph flow
40
Q

Lymphatic Pump

A
  • Valves created by the junction between endothelial cells exist all along lymphatic vessels to direct lymph fluid towards the heart
  • lymphatic vessels contract when filled with fluid, pumping lymph fluid along the vessel
  • after contraction, anchoring filaments cause vessels to recoil, reducing inside pressure and drawing fluid in
  • skeletal muscle contraction pumps lymph fluid
41
Q

What are some potential causes of edema

A
  • Hypertension
  • leaking of endothelium
  • not moving for extended periods of time (on flights)
  • Infections and congenital issues (elephantiasis)

Animal Physiology: Homeostasis (12 decks)

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