Blood vessels + circulation

Question 1

Describe the tunica interna of the artery wall

Answer 1

• smooth squamous endothelium
• has basement membrane
• contains internal elastic lamina

Question 2

Describe the tunica media of the artery wall

Answer 2

• thickest layer
• elastic fibres
• smooth muscle

Question 3

Describe the tunica externa of artery walls

Answer 3

• elastic + collagen fibres

Question 4

List the functions of elastic (conducting) arteries

Answer 4

• largest diameter arteries
• carry blood away from the heart
• store elastic energy which helps move blood during diastole
• pressure reservoir

Question 5

List the functions of muscular (distributing) arteries

Answer 5

Medium sized arteries
- distribute + regulate blood flow to muscles + internal organs (constrict + dilate)
- superficial muscular arteries form pressure points (eg. control bleeding/measure pulse) -> carotid, brachial, femoral

Question 6

Describe the functions of arterioles

Answer 6

• deliver blood to capillaries
• regulate systemic vascular resistance through vasoconstriction + vasodilation
• resistance vessels

Question 7

Describe the function + structure of meta arterioles

Answer 7

• supply capillary beds
• distal end has no smooth muscle -> thoroughfare channel

Question 8

Describe the structure + function of capillaries

Answer 8

• walls consist of only endothelium + basement membrane
• exchange of nutrients + waste via interstitial fluids (exchange vessels)

Question 9

Describe true capillaries + what their flow is regulated by

Answer 9

• emerge from arterioles + meta arterioles
• flow regulated by pre capillary sphincter
  -> intermittent flow caused by alternating contraction/relaxation of meta arterioles + pre capillary sphincters
  -> RBCs move single file through capillary

Question 10

List the 3 types of capillaries + their characteristics

Answer 10

continuous capillaries
- uninterrupted lining
- most common

fenestrated capillaries
- many fenestrations/pores
- found in kidney

sinusoidal capillaries
- large fenestrations + intercellular clefts
- incomplete basement membrane
- found in liver, spleen + bone marrow
-> enable drugs to be metabolised

Question 11

Describe what venules are formed from

Answer 11

small veins formed from merging of several capillaries -> merge to form veins

Question 12

Describe the 3 tunics of veins + their characteristics

Answer 12

• tunica interna thinner
• tunica media thinner -> less smooth muscle + elastic fibres
• tunica externa -> collagen = elastic fibres / lack elastic lamina of arteries

Question 13

What are the functions of veins

Answer 13

• hold 60% of blood volume
• capacitance vessels (volume reservoir)

Question 14

Define blood flow

Answer 14

volume of blood that flows through a tissue per unit time
-> determined by blood pressure + resistance

Question 15

Describe the conditions required for blood flow

Answer 15

circulatory pressure must be greater than total peripheral resistance (where TPR is determined by vascular resistance, blood viscosity + turbulence)

Question 16

What factor determines blood viscosity

Answer 16

ratio of RBC to plasma

Question 17

Define turbulence + the factors which affect it

Answer 17

• the slowing of blood flow
• high flow rates, irregular surfaces eg. plaque build up, + sudden changes in vessel diameter -> all increase turbulence

Question 18

What is the relationship b/t velocity of blood flow + CSA + how does this change through the vessels

Answer 18

• velocity inversely related to CSA
  -> velocity decreases as blood flows from aorta to capillaries
  -> velocity increases as blood flows from capillary to heart

Question 19

Why is velocity of blood flow slowest in capillaries

Answer 19

allows increased time for exchange

Question 20

Define blood pressure

Answer 20

Pressure exerted on walls of a blood vessel
-> decreases as moves further away from the heart

Question 21

What is venous return maintained by

Answer 21

• pressure gradient est. by heart
• skeletal muscle pumped
• respiratory pump
• valves

Question 22

List 3 things that occur if blood pressure is too low

Answer 22

• vessels collapse
• blood flow stops
• tissues die

Question 23

list 2 things that happen if blood pressure is too high

Answer 23

• vessel walls stiffen
• capillary beds rupture

Question 24

List the 3 methods substances can enter + leave the capillaries by

Answer 24

1. diffusion (most important)
2. transcytosis (vesicular transport) -> lipid soluble across membrane
3. bulk flow (filtration + absorption)

Question 25

Why is capillary exchange important + what drives it

Answer 25

- regulates relative volumes of blood + interstitial fluid - driven by balance b/t hydrostatic + osmotic pressures (net filtration pressure)

Question 26

List the 3 mechanisms controlling cardiovascular regulation

Answer 26

1. autoregulation 2. neural mechanisms 3. hormonal mechanisms

Question 27

Describe how autoregulation occurs through local factors + what is affected by this

Answer 27

local factors = alter pattern of blood flow through capillaries via local vasoconstrictors or local vasodilators -> act on pre capillary sphincters to control blood flow through a single capillary bed

Question 28

List 4 local vasodilators

Answer 28

- increased tissue CO2 or decreased O2 - lactic/other acid from tissue cells - chemicals released during inflammation eg. histamines - elevated local temp

Question 29

what is an example of a local vasocontrictor

Answer 29

prostaglandins from activated platelets

Question 30

explain the negative feedback loop that occurs that has vasodilation as the effect

Answer 30

- homeostasis disturbed by physical stress (increased temp), chem. changes or increased tissue activity - causes inadequate local blood flow/BP - results in local decrease in resistance + increase in blood flow - homeostasis restored

Question 31

state where neural control happens from + what it changes

Answer 31

- neural control via cardiac centres + vasomotor centres in medulla oblongata -> changes HR, contractility + resistance of blood vessels (affects CO)

Question 32

List the 4 areas the cardiovascular system receives input from

Answer 32

- higher brain regions eg. hypothalamus - proprioceptors - baroreceptors (monitor BP) - chemoreceptors (monitor blood acidity)

Question 33

what 2 mechanisms does the cardiovascular centre send outputs via

Answer 33

sympathetic impulses : - cardio accelerator nerves (increase HR and contractility) - vasomotor nerves (cause vasoconstriction + vasodilation) parasympathetic impulses: - vagus nerve decreases HR

Question 34

Explain the function + location of baroreceptors

Answer 34

function = monitors degree of stretch of blood vessels -> BP falls when stretched less therefore send impulse to CV centre location = carotid sinus + aorta

Question 35

Explain the response to increased baroreceptor stimulation when BP increases

Answer 35

- homeostasis disturbed by increased BP - baroreceptors stimulated - cardio inhibitory centre stimulated = decrease CO - cardio accelatory + vasomotor centres inhibited = vasodilation occurs -> homeostasis restored + BP decreases opposite for decreased BP

Question 36

list the 4 hormones produced by the endocrine system to regulate the CV system + describe their functions

Answer 36

E + NE from adrenal medulla = increase CO + peripheral vasoconstriction ADH from posterior pituitary= increase peripheral vasoconstriction -> increase BP Angiotensin 2 = causes vasoconstriction -> increases BP Erythropoietin from kidneys = stimulates RBC production in bone marrow

Question 37

list the 3 CV responses to exercise

Answer 37

- extensive vasodilation - increased venous return - increased CO via increased venous return + increased sympathetic activity