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Bioregulatory systems 3 > The circulation > Flashcards

The circulation Flashcards

1
Q

What is the basic structure of microcirculation?

A

1st arteriole(contains smooth muscle) -> terminal arteriole(has precapillary sphincter muscle) ->cappillaries ->pericytic venule -> venule

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2
Q

What is the definition of the blood flow rate?

A

volume of blood passing through a vessel per unit of time

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3
Q

What is Darcys Law ?

A

Pressure gradient = flow rate x resistance

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4
Q

What is the equation to calculate flow rate?

A

Flow rate(Q) = pressure gradient/ Resistanvce(R)

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5
Q

What will increase the blood flow to the capillaries?

A

-increase in the pressure gradient will increase the flow -decreased resistance

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6
Q

What 3 things effect the resistance of a blood vessel?

A
  • length
  • radius
  • blood viscosity
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7
Q

What happens to the pressure gradient, resistance, and flow rate if your blood pressure increase?

A

p=increase r= f=increase

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8
Q

What happens to the resistance and flow rate when the arterioles narrow?

A

R=increase F=decrease

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9
Q

What has the biggest influence on resistance?

A

arterioles-they have lots of muscle, so lots of abiltiy to restrict and dialate and therefore change the pressure?

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10
Q

Where is the biggest pressure drop in the cardiac system?

A

from one end of an arteriole to the other

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11
Q

Which vessels have the greatest resistance and how does this relate to pressure?

A

ARTERIOLES have the greatest resistance (due to small lumen) and therefore this is where there is the greatest drop in pressure

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12
Q

What is the equation that relates the flow of blood in the organ to the resistance an pressure?

A

Flow to the organ=pressure gradient/resistance of the organ

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13
Q

What is the pressure gradient the same as?

A

mean arteriole pressure in an organ

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14
Q

What would happen if there was nor pressure gradient along the arterioles?

A

The blood would not reach the capillary bed

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15
Q

What happens to the radius, resistance, and flow in a vessel during vasoconstriction and vasodialation?

A

VASOCONSTRICTION: Radius-decrease Resistance-increase Flow-decrease VASODIALATION: Radius-increase Resistance-decrease Flow-increase

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16
Q

How do we describe the state of Arteriolar smooth muscle at rest and why is this important?

A

PARTIAL CONSTRICTION-this is called VASCULAR TONE This gives the arterioles the opportunity to either dilate if more blood is needed or constrict if less is needed

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17
Q

What are the 2 major functions of the arterioles?

How are these achieved?

A

1) Match blood flow to the metabolic needs of specific tissues (depending on the bodies momentary needs)-regulated by LOCAL INTRINSIC CONTROLS and independent of nervous or endocrine stimulation(brain)
2) Help regulate the systemic arterial blood pressure -regulated by EXTRINSIC CONTROLS which travel via nerves or blood and are usually centerally coordinated

changing the radii of the arteriole

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18
Q

What happens to the blood flow in the arterioles if the tissue becomes more active?

A
  • metabolite increase
  • oxygen usage increase

these lead to VASODIALATION = increase blood flow

This called active Hyperaemia

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19
Q

What 2 mechanisms allow for arterial blood flow to change to accomadate the changing metabolism of tissues?

A
  • Autoregulation
  • Active Hyperaemia
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20
Q

Describe myogenic autoregulation?

A
  • decreased blood temp
  • increased arteriole vessel stretch due to high BP

both lead to VASOCONSTRICTION of arterioles

21
Q

How can cold temperature help and injured person?

A

put n icebag on them and this will result in less swellingdue to vasoconstriction

22
Q

What happens if a certain tissue type needs more blood but another nearby does not?

A

blood pressure increase

but if certain tissue doesnt need this extra blood it will CONTRACT to ensure that blood doesnt enter every tissue in the body

23
Q

What happens to the skeletal muscle arterioles during exercise?

A

ACTIVE HYPERAEMIA-dilation due to tissues needing more blood(vessels going to other tissues not needed during exercise will CONTRACT to prevent excess blood flowing this ways)

24
Q

What happens to the small intestine arterioles during exercise?

A

Myogenic Autoregulation/vasoconstriction-vessels will CONTRACT to prevent excess blood flowing this way as the small intestine is not needed during exercise

25
Q

What is Darcys Law?

A

Blood flow=pressure gradient/resistance

OR

Cardiac Output=Blood pressure/ total peripheral resistance

26
Q

What helps regulate blood pressure?

A

Cardiovascular control centre in the MEDULLA- this controls vasocontriction and vasodialation HORMONAL control by the brain-Vasopresin/ADH, Angiotensin II, Adrenaline/noradrenaline(all these hormones cause vasoconstriction)

27
Q

What 3 hormones cause vasoconstriction and which is the most powerful?

A
  • Vasopressin
  • Angiotensin II(most powerful)
  • Adrenaline/noradrenaline
28
Q

What is the lumen diameter and cell width of the capillaries?

A

lumen-7micrometres

Celll width-1 micrometre

29
Q

What is the function of the capillaries?

A
  • delivery of metabolic substrates to the cells of the organism (ultimate function of of the CVS)
  • ideally suited to enhance diffusion Fick’s Law -minimise diffusion distance and maximise the surface area and the time for diffusion
30
Q

Why is capillary density important?

A

The more metabolically active the tissue is the more capillaries it needs

31
Q

What is the capillary density of the brain, skeletal muscle and the lungs?

A

Skeletal muscle=100cm^2/g

Brain=500cm^2/g

Lung=3500cm^2/g

32
Q

What is the general rule relating to why a certain type of tissue will have a higher capillary density vs others? What is the exception to this

A

denser capillary networks in highly metabolically active tissues have

The lungs are an exception to this because they have the largest capillary volume because it wants to be as efficient as possible at extracting oxygen that you breath in so needs to make sure that there is an capillary as close as possible to all the alveolis

33
Q

Why is blood flow through the skeletal muscles limited at rest?

A

Becuase the skeletal muscle is the largest mass in the body so if blood was flowing through it even when it was not needed, this would be a massive challenge to the cardiovascular system as it would take longer for the blood to be pumped around the body to tissues where it is actually needed

-so if skeletal muscle is needed the arterioles are heavily constricted to prevent blood flow through them

34
Q

What is the structure of the continuous capillary wall?

A
  • one cell thick endothelium layer
  • there is a H2O filled gap junction between the endothelium cells
35
Q

How do things leave the capillaries?

A
  • if small enough they can diffuse through the gaps in the endothelium wall
  • diffuse across the epithelium lining
  • Or pass via a protein in the endothelium cell wall
36
Q

What is the structure of the Fenestrated capillary wall

A

-CIRCULAR HOLES in the capillary wall which allow slightly larger things to move through

37
Q

What structure has fenestrated capillaries and why?

A

The glomeralus (sack of capillaries in the kidney) -allows glucose to pass out glomeralus and into the kidney tissue

38
Q

What is the most uncommon type of capillary wall structure?

A

DISCONTINUOUS - different sized gaps in the walls -can have very big gaps to allow much larger substances into the tissue/blood

39
Q

What are the types of capillary cell wall structures?

A

-Continuous -Fenestrated -Discontinuous

40
Q

Where can you find discontinuous capillaries?

A

BONE MARROW-because you need white cells to move out of the bone marrow into the blood liver

41
Q

What type of capillary is the blood brain barrier and why?

A

CONTINUOUS- as the brain is the most important thing in the body basically

  • NO GAP JUNCTIONS whatsoever, instead it has TIGHT JUNCTIONS in between the endothelial cells
  • means its more difficult for things to leave the blood and enter the brain, allowing the brain to have tighter control over what what enters
42
Q

What is bulk flow?

A

PROTEIN FREE PLASMA that filters out of the capillaries and mixes with the surrounding interstitial fluid and is reabsorbed

43
Q

What causes plasma to leave the capillaries ?

A

hydrostatic pressure in the capillaries

44
Q

What causes the plasma to be reabsorbed into the capillaries?

A

ONCOTIC PRESSURE

45
Q

What is Starlings hypothosis?

A

There has to be a balance between the hydrostatic pressure of the blood in the capillaries and the oncotic force drawing it back in and if there wasnt a balance you would be losing to much fluid from the blood

46
Q

Describe the pressures in the capillaries and how this effect fluid movement in and out of the capillaries?

A

Hydrostatic pressure- high at the beginning of the capillary and decreases as you go along it(acts outwards)

Oncotic pressure/osmotic pressure- stays the same (acts inwards) -At the start of the capillary the osmotic pressure is less than the hydrostatic pressure and therefore overall the net effect is fluid moving out(ULTRAFILTRATION)

-at the end of the capillary the oncotic pressure>hydrostatic pressure so fluid is drawn in, therefore =REABSORPTION of flui

47
Q

What is meant by ultrafiltration is more effective than reabsorption?

A

It means that there is a net loss of fluid as some of the plasma that leaves doesnt re-enter(a very small amount)

48
Q

What does the lymphatic system do?

A

-pick up the fluid that was lost from the capillaries and not reabsorbed, and at some point return it back to the blood to ensure blood pressure is maintained

Bioregulatory systems 3 (11 decks)

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