L13

Question 1

what is the purpose of the cardiovascular system

Answer 1

Purpose us to circulate blood to/from every cell/organ in body

Question 2

what are the extrinsic mechanisms of the cardiovascular system

Answer 2

○ Autonomic nervous system
○ Hormones/neurotransmitters
- More involved with overall control of BP

Question 3

what are the intrinsic mechanisms of the cardiovascular system

Answer 3

○ Autoregulation
○ Local factors found within blood vessels in each organ
- Ensures each organ has adequate flow at all times

Question 4

what is Ohms law?

Answer 4

Pressure gradient/resistance = flow

Question 5

what is the relationship between CO and MAP

Answer 5

○ CO = MAP/TPR (SVR)
§ TPR= total pheripheral resistance
MAP = mean arterial rpessure

		§ If CO or TPR increases, then MAP increases If CO or TPR decreases, then MAP decreases

Question 6

how to ensure adequate blood flow

Answer 6

• To ensure adequate flow to each organ, must maintain a constant rpessure head
  
  • E.g. Mean arterial blood pressure
    Vasodilation/vasoconstriction regulates blood flow

Question 7

what is the result of hypotension/hypertension

Answer 7

• Hypotension
  ○ Low BP = less tissue perfusion = ischemia, shock

*Hypertension
High BP = more afterload = cardiac failure = raptured blood vessels = stroke + cerebral ischemia

Question 8

how to control BP in the short term

Answer 8

• Baroreceptors- Short term control of BP
  
  • Fast repsonse
    ○ Have naked nerve endings
    ○ Function as mechanoreceptors- so respond to stretch (effected by pressure)
    ○ Are tonically active- means important for maintaining
    ○ Are more sensitive to rapid change sin BP then absolute BP
    ○ Found in high pressure vessels
    § E.g. Aortic arch- ensure coronary perfusion
    § E.g. Carotid sinus- ensure cerebral perfusion

Question 9

what is the effect of increasing/decreasing BP on baroreceptor firing rate

Answer 9

§ Increase BP = increase stretch on vessel walls = increase baroreceptor firing rates
§ Decrease BP = decrease stretch on vessel walls = decrease baroreceptor firing rates

Question 10

how to control BP in the long term

Answer 10

• Kidney
  ○ Slow response
  ○ Uses ECF and blood volume
  Increase blood volume = increase BP = acts on kidneys = increases water + salt excretion = decreases ECF = restores blood volume

Question 11

explain the BP pathway

Answer 11

• Input: Baroreceptors- monitor blood pressures
  
  • Send nerve impulses of cardiovascular centre (medulla oblongata)
  • Goes through nerves to effectors, response
    ○ vagus nerves (parasympathetic, DECREASE heart rate)
    ○ cardiac accelerator nerves (sympathetic, INCREASE heart rate + contractility)
    vasomotor nerves (sympathetic, vasoconstriction in blood vessels)

Question 12

what is the feedback loop for INCREASED BP

Answer 12

○ Blood pressure increase
○ Increase carotid sinus + aortic arch receptor potential
○ Icnrease rate of firing in afferent nerves
○ Detected by baroreceptors
○ Send impulses to cardiovascular centre
○ decreases sympathetic cardiac nerve activity and vasoconstrictor nerve activity, increases parasympathetic nerve activity
○ Decreases heart rate + stroke volume and vasodilation of arteries + veins
○ Decrease cardiac output + total peripheral resistance
Leads to decreased blood pressure

Question 13

What is the feedback loop for DECREASED BP

Answer 13

○ Blood pressure decrease
○ Decrease carotid sinus + aortic arch receptor potential
○ Decrease rate of firing in afferent nerves
○ Detected baroreceptors
○ Sends nerve impulses cardiovascular centre
○ increase sympathetic cardiac nerve activity and vasoconstrictor nerve activity, decrease parasympathetic nerve activity
○ increase heart rate + stroke volume and vasoconstriction of arteries + veins
○ Increase cardiac output + total peripheral resistance
Leads to increased blood pressure

Question 14

explain the baroreceptor reflex

Answer 14

• Immediate response to changing BP
  
  • Minimises normal daily fluctuations in BP
  • Returns BP to survival levels when sever change- e.g. Haemorrhage
  • Renin + volume receptors
    ○ Act to maintain effective blood volume circulation
    Involved in long term control of MAP

Question 15

describe autoregulation

Answer 15

• Each organ receives blood at a pressure of 93mmHg (MAP)
  
  • Each organ regulates its own flow mechanisms to meet their own metabolic requirements
    As metabolic rate increases, required blood flow increases

Question 16

how are blood vessels control by intrinsic mechanisms

Answer 16

§ Autoregulation
§ INSIDE organ/tissue
§ Distributes blood flow to individual organs/tissues as needed
Controlled by metabolic + myogenic controls

Question 17

how are blood vessels controlled by extrinsic mechanisms

Answer 17

§ Maintains MAP
§ OUTSIDE organ/tissue
§ Only influences blood flow to skeletal muscles + delievery of blood
§ Re-distributes blood during exercise + thermoregulation
Controlled by nerves + hormones

Question 18

explain blood flow distribution at rest for;
CO, brain, heart, kidney, Gi, skin, other tissues, skeletal muscles

Answer 18

○ CO = 5.8L/min
○ Brain = 13%
○ heart = 4%
○ Kidney = 19%
○ GI = 24%
○ Skin = 9%
○ Other tissues= 10%
Skeletal muscles = 21%

Question 19

explain blood flow distribution when exercising:
CO, brain, heart, kidney, Gi, skin, other tissues, skeletal muscles

Answer 19

○ CO= 25.6L/min
○ Brain = 3%
○ Heart = 4%
○ Kidney = 1%
○ GI = 1%
○ Skin = 2.5%
○ Othe tissues = 0.5%
Skeletal muscles = 88%

Question 20

what is the effect of aging on the cardiovascular system

Answer 20

• Results in ‘wear + tear’
  
  • E.g.
    ○ Loss of compliance of aorta
    ○ Loss of cardiac muscular strength
    ○ Slower baroreceptor reflex
  • Related diseases
    ○ Valve disease
    ○ Hypertension
    ○ obesity