Wk 4 Flashcards
(21 cards)
Metabolic activity within capillary perfusion; what happens to precapillary sphincters at rest and active
at rest; are constricted and metarteriole acts as a shunt
active; become relaxed
- if more capillaries open the diffusion distance betw capillaries and surrounding cells decrease
What are the 4 ways exchange occurs across capillary walls
- simple diffusion; lipid-soluble substances pass through endothelial cells
2.facilitated diffusion; small water soluble substances pass through pores
- transcytosis; exchangeable proteins are moved across vesicular transport
- filtration and reabsorption; water and solute move across capillary walls
What are the 4 pressure involved in filtration and reabsorption- what does it result in
capillary hydrostatic pressure
capillary colloid osmotic pressure
interstitial fluid hydrosatic pressure
interstitial fluid coloid osmotic pressure
Results in the forces outweighing the reabsorption forces and net filtration occurs
Role of capillary hydrostatic pressure and osmotic pressure
Pc matches the PiC to provide balance and minimise fluid movement across the capillary
Direction of action potential in cardiac muscle cells
CA+2 released from extracellular fluid or release of Ca+2 from sarcoplasmic reticulum
leads to increase of intracellular Ca+2
increase in cross bridge cycling betw thick and thin filaments in sarcomeres
myocardial contraction occurs
What is cross bridge cycling
the binding and unbinding of thick filament in thin filament when Ca+2 binds to troponin-tropomyosin complex
What are the 5 phases of the cardiac cycle
- ventricular diastole;
- ventricular systole- isovolumetric phase;
- ventricular systole- ventricular ejection
- ventricular diastole
- ventricular diastole- early
what happens in phase 2 of the cardiac cycle
- ventricular systole- isovolumetric phase; ventricular contraction pushes AV valves closed and there is not enough pressure to open semilunar valves
what happens in phase 1 of cardiac cycle
- ventricular diastole; artrial contraction forces blood into relaxed ventricles (small vol.)
astrial systol ends and atrial diastole begins
what happens in phase 3 of the cardiac cycle
ventricular systole- ventricular ejection; ventricular pressure rises and exceeds pressure in arteries-
semilunar valves are open and blood ejection
what happens phase 4 of cardiac cycle
ventricular diastole; isovulumetric relaxtion
as ventricles relax, pressure in ventricles drop and blood flows back against cusps of semilunar valves and makes them close
blood is in relaxed atria
what happens in phase 5 of cardiac cycle
ventricular diastole- early
chambers are relaxed and ventricles fill passively
From Wigger’s diagram; explain what is happening in the P wave
- depolarization of atria and contraction, hence increase in atrial pressure
wigger’s diagram what is happning in the QRS complex
depolarization of ventricles and contraction– increase in ventricular pressure
What happens to ventricular pressure at stage 3
becomes greater than atrial pressure and the pressure gradient changes across AV valve
AV valve closes
What happens to ventricular pressure at stage 4
ventricular pressure becomes greater than aortic pressure and pressure gradient changes- aortic valve opens and blood flows into the aorta (ventricular ejection)
What occurs at the T wave at stage 5
ventricles repolarize and ventricular relaxation occurs but pressure falls
what happens at stage 6 to ventricular pressure
pressure falls below aortic pressure and aortic valve closes
What is venous return
the flow of blood back to the heart to maintain stroke volume and cardiac output- dependent on venous pressure gradient
How to increase cardiac output
Increasing heart rate via the autonomic nervous system;
- sympathetic activation HR
parasympathetic decreases HR
How to increase stroke volume
Increasing pre-load (end diastolic volume)
decreasing after-load (arterial pressure)
increasing contractility
