Lecture 11: CV response to exercise 1 Flashcards
closed loop design of circulatory system
- what does the heart do? (aka what?)
- what are the 3 circulations ish –> do they have low or high resistance and conductance?
HEART = the pump
- creates pressure needed to move blood through circulatory system
1. SYSTEMIC ARTERIAL CIRCULATION:
- large, low resistance (high conductance) tubes conducting blood from left heart to various organs
2. MICROCIRCULATION:
- small tubes, high resistance, low conductance vessels
3. SYSTEMIC VENOUS CIRCULATION:
- large, low resistance (high conductance) tubes conducting blood back to the right heart
what are the 3 components of the microcirculation?
- describe tubes + function ish
- ARTERIOLES: small tubes within tissue that control tissue blood flow –> high resistance (low conductance) vessels
- CAPILLARIES: thin tubes allowing exchange of substances (O2, CO2, nutrients) btw blood and tissue
- VENULES: small tubes within tissue for collection of blood from capillaries
what is arterial blood pressure?
- determined by relationship btw (2)
force exerted by blood against arterial walls
- cardiac output and total vascular conductance!
what is systolic vs diastolic blood pressure?
SYSTOLIC: pressure generated as blood is ejected from the heart during ventricular systole/contraction (120 ish)
*influenced by body size, sex
DIASTOLIC: pressure during ventricular diastole/relaxation (when heart is filling up) (80 ish)
what is MAP?
- determines what?
- formula? + derive its components
- Mean Arterial Pressure is the average pressure during a cardiac cycle
- it determines the rate of blood flow through the systemic circulation = pressure required for blood flow to muscles, organs and tissues
- MAP (mm Hg) = CO/TVK
MAP = HR * SV * (length * viscosity)/r^4
what is the formula for CO?
for TVK?
Cardiac output:
CO = heart rate x stroke volume (volume of blood pumped out at L ventricle at each systolic contraction)
total vascular conductance:
TVK = 1/SVR (systemic vascular resistance)
SVR = (length * viscosity)/r^4
*small change in r = HUGE impact!
what is the relationship btw conductance and resistance?
low resistance = high conductance
high resistance = low conductance
bc TVK = 1/SVR
what is the major regulated variable if you want to increase systemic circulation?
mean arterial pressure (MAP)!
- MAP represents the _______ ________ for blood flow through all the organs
- what is CO
- what is TVK
- CO and TVK determine ______ _______ ______, and thus, MAP
- the driving force (pressure reservoir in the arteries *schéma)
- CO is the rate of blood pumped from the heart into the systemic circulation in L/min (ie how much blood goes into the bucket *schéma)
- TVK is the sum of conductance to flow provided by all systemic blood vessels (ie how wide the arterioles are)
- CO and TVK determine arterial blood volume and thus MAP
formula of blood flow and its components
- what happens to flow if decrease arteriole radius by 1/2?
flow = delta(P) x K
- delta (P) = pressure gradient
- K = 1/R
- R = (length * viscosity)/r^4
- if decrease r by 0.5 –> 16 fold increase in resistance or decrease in conductance = decrease flow
what is the primary way in which cardiovascular system regulates tissue blood flow to a particular vascular bed?
through changes in conductance given a vascular bed –> which is secondary to changes in arteriole radius (vasodilation, vasoconstriction)
- where vasodilation comes from ie contraction of muscles (bc signals for more blood to come/feedforward)
what is the formula for VO2?
CO x arterial-mixed venous O2 content difference (C(a-v)DO2)
C(a-v)DO2 is determined by (2) + describe subthings
- is it good to have a big or small C(a-v)DO2?
- O2 carrying capacity of arterial blood:
- hemoglobin concentration (Hb)
- partial pressure of O2 in arterial blood (PbO2)
- affinity of Hb to O2, which is affected by PaO2, temperature and pH (O2 dissociation curve) - muscle O2 utilization/extraction: capillary density, mitochondrial density and function, adequacy of tissue perfusion and diffusion
- big! that means more O2 in blood and more O2 is utilized by muscles
sex and training related differences in maximal exercise CO are due primarily to differences in which variable?
in stroke volume!
- during max exercise, everyone will probably reach a max heart rate (ie 200 bpm for everyone)
- therefore, it’s the SV that changes
- men have higher SV then women (110 vs 90 for untrained, and 180 vs 125 for trained)
- trained have bigger SV than untrained (180 vs 110 for men and 125 vs 90 for women)
- which nodes are contacted by which nervous systems for HR regulation?
- explain how the nervous system regulates HR before, at onset and during exercise
- both PNS and SNS innervates both SA and AV nodes
1. when stimulated, PNS nerves (ie vagus nerve)release the neurotransmitter acetylcholine –> decreases HR by decreasing SA and AV node activity
2. at the onset of exercise, there is a rapid PNS withdrawal, which increases HR UP to 100 bpm
3. as exercise intensity increases, SNS stimulation causes release of neurotransmitter norepinephrine –> increases HR + increases force of myocardial contractility (from increasing action potentials) by increasing SA and AV node activity - SNS stimulation is responsible for increasing exercise HR above 100 bpm