Lecture 8 Heart Physiology Flashcards
Arterial blood flows
Away from the heart.
Venous blood flows
towards the heart.
Design of the mammalian cardiovascular system. (4 points).
Four chambered heart.
Blood flows in one direction.
Arterial blood flows away from the heart.
Venous blood flows towards the heart.
Right and left pumps contract….
also what pumps 1st and 2nd
simultaneously.
Atria contract first…
ventricles contract second
Blood movement through the heart is gated by
valves
Tricuspid and mitral valves control flow between the
atria and ventricles
Aortic and pulmonary valves control flow from the
ventricles out to the circulatory vessels
Valves open and close to
direct blood
Cellular mechanism of cardiac contraction. (4 steps)
- Ca2+ levels go up, and more Ca2+ is released from the sarcoplasmic reticulum (SR).
- Myosin binds to actin to form cross-bridges.
- Myosin pulls on actin to shorten the sarcomere and generate force.
- Every myocyte activated during each heart beat.
How are cross bridges formed?
Myosin binds to Actin.
Myosin pulls on actin to
shorten the sarcomere and generate force.
What is activated during each heart beat?
Every Cardiomyocyte.
how can we increase force of contraction?
Extent of X- bridges formed not maximized at rest…..
↑ cytosolic Ca2+ level
↑ number of cross-bridges formed
↑ force of contraction.
Cellular mechanism of cardiac relaxation
Decrease in cytosolic Ca2+ levels.
(Ca2+ pumped back into the SR).
Cross-bridges release when ATP binds to myosin.
Reduction in force means the heart can relax.
All cardiac myocytes relax each beat.
Diastole
Relaxation
Falling pressure
Systole
Contraction
Rising pressure
Cardiac cycle and main phases
Starting point
Atrial contraction / systole
Atrial diastole
Isovolumetric ventricular contraction (Ventricular systole 1st phase )
Ventricular Ejection (Ventricular systole 2nd phase)
Isovolumetric ventricular relaxation (Ventricular diastole early phase)
Ventricular diastole late phase - passive filling phase
Starting point (atria, ventricles, AV valves, semilunar valves)
ready for heartbeat
Atria and ventricles full of blood
AV valves open (to allow blood into ventricles)
Aorta & Pulmonary valves close (Keep blood within heart)
Atrial contraction / systole
what contracts
Kicks of heartbeat
2 atria contract and pack as much blood into the ventricles
Atrial diastole
Atria is relaxing (pushed as much blood into the ventricles)
AV valves close (to prevent backflow into atria)
Isovolumetric ventricular contraction (Ventricular systole 1st phase)
(Valves, pressure, volume)
Ventricles contract
AV valve close
Aorta and Pulmonary valve close
Rapid build of pressure
No where for blood to escape the ventricles.
Blood volume is same
Ventricular Ejection (Ventricular systole 2nd phase)
The pressure is so high causes the aortic and pulmonary valve to open and blood is ejected out of ventricles into arteries
Pressure falls
Isovolumetric ventricular relaxation (Ventricular diastole early phase)
(valves, volume, ventricle)
AV valves close
Pulmonary and Aortic valves close
Lower blood volume
Ventricles relax
Space is getting larger the volume stays the same
Decrease pressure in the ventricles
Ventricular diastole late phase - passive filling phase
AV valves open
Blood from veins fill up atria and ventricles
Blood pressure
measure
Systolic point / diastolic point
highest point / lowest point
Pulse pressure
difference between systolic and diastolic blood pressure. (highest - lowest)
Mean arteriole blood pressure
A bit lower than the mid point of the systolic and diastolic point
why is the MAP lower than mid point?
Heart spends more time relax (diastole) than in systole.
Hypertension
Systolic pressure too high (mmHg) - millimeters of mercury
Heart failure / stroke
Hypotension
Diastolic pressure too low (mmHg)
Poor circulation through system.
Affects certain areas further from the heart (brain) more
Syncope (fainting, unconscious state brain not getting enough oxygen)
Pulmonary circuit
resistance
Moves blood to lungs from heart
Short circuit
Low resistance
Right side of the heart only needs low pressure as the resistance is low.
Systemic circuit
Moves blood throughout body
Long circuit
High resistance
Left side of the heart needs to create high pressure to overcome the resistance
