exchange in and control of peripheral circulation Flashcards

1
Q

Identify the processes involved in transport between capillaries and tissues.

A

Specialised for exchange. There are lots of them and every tissue is close to a capillary. Very thin wall so a small diffusion barrier

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2
Q

Explain the significance of the blood-brain barrier.

A

Protect against circulating toxins or pathogens that could cause brain infections, while at the same time allowing vital nutrients to reach the brain.

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3
Q

Explain the significance of Starling forces and the lymphatic system in relation to oedema.

A

bulk flow results on 3 L of fluid remaining which need to be drained by the lymphatic system.

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4
Q

Justify the importance of Poiseuille’s Law in relation to the control of resistance and blood flow.

A

varying radius of resistance vessels can be used to control flow and redirect blood.

reducing resistance of vascular bed increases flow through vascular bed but reducing TPR also reduces mean arterial pressure. you cannot effect one without the other.

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5
Q
  • Define active hyperaemia, pressure autoregulation and reactive hyperaemia.
A
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6
Q

Explain the basis of the injury response.

A

c fibres are triggered by external stimuli. Results in arteriolar dilation which increases blood low and increases permeability. Aids delivery of blood front leucocytes to injured area

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7
Q
  • Identify the various neural tone, affecting arteriolar tone.
A

sympathetic nerves release noradrenaline and binds to alpha one receptors causing arteriolar constriction therefore a decreased blood flow though the tissues and tends ti increase TPR and increases MAP

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8
Q
  • Describe the dominant factors controlling blood flow in cardiac, cerebral, pulmonary and renal vascular beds.
A

cardiac- blood supply Is interrupted by systole. expresses beta 2 receptors which swamp any sympathetic arteriolar constriction

cerebral- needs to be kept stable. shows excellent pressure auto regulation

pulmonary- decreased O2 causes arteriolar constriction and entrees blood is directed to best ventilated parts of lung

renal- main job is filtration, kept constant during fluncuations in MAP due to pressure auto regulation

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9
Q

describe continuous capillaires

A

Tight junctions as endothelial cells are pressed really tightly together. No clefts or pores e.g brain

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10
Q

describe fenestrated capillaries

A

large pores and clefts making them specialised for fluid exchange

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11
Q

describe transcytosis

A

brings proteins and macromolecules across the endothelium and some vesicles fuse to create temporary channels

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12
Q

discontinous capillaires

A

clefts and massive pores e.g liver large proteins can move across

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13
Q

exchange of gases in capillaries

A

via diffusion. self regulating, non saturable- does’nt need transporter proteins
no polar substances can cross through membrane and polar substances through clefts and pores

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14
Q

active metabolic hyperaemia (local)

A

Trigger is an increase in local metabolism
During exercise (increase in metabolism) you will get an increase in skeletal muscle and increased porduciton in medabolites which increases concentration and trigger a local chemical signal called endothelial derived relaxing factor

When it is released from the endothelium it will diffuse into smooth muscle and surround arteriole. Arteriole will dilate, radius increase and resistance will go down and increased blood flow. Increased blood flow will remove metabolites and return to steady flow.

Only benefits this tissue

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15
Q

Pressure flow auto regulation

A

Triggered by decrease in perfusion pressure. Increases mean arterial pressure decreased blood flow. Metabloites increase. Releases EDRF. arterioles dilate and flow is rested to normal.

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16
Q

reactive hyperaemia

A

. Occlusion of blood supply- cuff around arm metabolites build up in artery and aren’t being washed away and endothelium will relase EDFR causes it to dilate. When cuff is removed lots of blood will flow making the arm red

17
Q

reactive hyperaemia

A

. Occlusion of blood supply- cuff around arm metabolites build up in artery and aren’t being washed away and endothelium will relase EDFR causes it to dilate. When cuff is removed lots of blood will flow making the arm red

18
Q

Identify the various HORMONAL tone, affecting arteriolar tone.

A

Releases adrenaline from adrenal medulla and binds to alpha 1 receptors causing arteriolar constriction. Therefore decreased blood flow though the tissue which increases TPR and MAP

but in some tissues skeletal and cardiac muscle also activated beta receptors causing arterial dilation and increases blood flow and decreases TPR