Lecture 23 Cardio 3 (2)

Question 1

Control of blood flow to the tissues

Answer 1

Intrinsic control - metabolic

Extrinsic control -autonomic & hormones

Question 2

Intrinsic Control

Answer 2

metabolic control - repsonse of vascular smooth muscle to local chemical changes due to metabolism
hyperemia and ischemia

Question 3

Hyperemia

Answer 3

increase in blood flow to tissue in response to increase metabolic demand

Question 4

Ischemia

Answer 4

insufficient (reduction) blood flow to tissue

Question 5

Perfusion

Answer 5

blood flow to tissue or organ

Question 6

Extrinsic control

Autonomic NS

Answer 6

sympathetic NS: NE -> a1 adrenergic receptors -> vasoconstriction in most tissues
this reduces blood flow
no dual innervation

Question 7

Extrinsic control

Hormones

Answer 7

Epi -> B2 adrenergic receptors -> vasodilation in skeletal muscles
ADH (vasopressin) -> vasoconstriction in most tissues
Paracrine regulators:
nitric oxide (NO) -> vasodilation
Prostaglandins -> vasodilation or vasoconstriction

Question 8

Capillary Circulation (Microcirculation)

Answer 8

Flow through capillary beds
Exchange across capillary walls
Filtration and reabsorption

Question 9

Flow through capillary beds

Answer 9

blood flow (perfusion) through capillaries is highly variable
regulated by: arteriolar smooth muscle (vasoconstiction/vasodilation), precapillary sphincters

Question 10

Exchange across capillary walls

Answer 10

capillaries interstitial fluid

fluid and substance exchanged across endothelium via diffusion, transcytosis, and bulk flow

Question 11

Bulk flow across capillary walls - Filtration

Answer 11

filtration out of a capillary - driven mostly by blood pressure in the capillary bed (BPcap)

Question 12

Bulk flow across capillary walls - Reabsorption

Answer 12

reabsorption back into capillary - driven mostly by colloid osmotic pressure (COP)
(oncotic pressure) which is due to plasma proteins (albumin) that stay in capillaries
COP = 25 mmHg

Question 13

Filtration and reasborption is determined by

Answer 13

the balance between BP and COP in the capillary

Question 14

Net filtration pressure

arteriole end vs venule end

Answer 14

NFP = BPcap - COP
at arteriole end: BPcap > COP -> NFP is positive -> filtration
at venule end: BPcap < COP -> NFP is negative -> reabsorption
total filtration exceeds reabsorption by approx. 2-3 L/day
excess interstitial fluid is collected by the lymphatic system and returned to veins

Question 15

Edema

Answer 15

results when filtration&raquo_space; reabsorption

Question 16

Histamine

Answer 16

local vasodilator

increases capillary permeability, plasma proteins leak out

Question 17

high arterial BP

Answer 17

can increase BPcap slightly, regualted by local vasoconstriction

Question 18

high venous BP (back pressure)

Answer 18

increases BPcap, hard to regulate

e.g. venous obstruction, congestive heart failure

Question 19

Atherosclerosis

Answer 19

fatty deposits in arterial wall

carried by LDL

Question 20

If TPR decreases

Answer 20

CO increases to maintain MAP