Unit III -the Heart Flashcards
Where can we find intecalated discs?
Between cardiac muscle cells
What is the resting membrane potential of cardiac muscle?
Ca. -85 to -95 millivolts
What is the action potential of cardiac muscle?
105 millivolts
For how long is the membrane depolarized in atria?
0.2 seconds
For how long is the membrane depolarized in the ventricle?
0.3 seconds
Striated muscles
- Cardiac muscle
- Skeletal muscle
Which muscles have fast sodium channels?
Skeletal muscles
Which muscle has slow calcium channels?
Cardiac muscle
Calcium that enters these channels also promotes cardiac muscle contraction
What promotes muscle contraction?
Diffusion of calcium into the myofibrils
Isovolemic relaxation
Is caused by ventricular relaxation
Period of ejection
Is when ventricular outflow occur
Most ejection occurs during this period
Period of rapid ejection
Ejection fraction
The fraction of end-diastolic volume that is ejected
End-diastolic volume
The volume of each ventricle (110-120 milliliters) atthe end of diastol
The stroke volume
- 70 milliliters
- Is the amount of the blood ejected with each beat
The end-systolic volume
- 40-50 milliliters
- Is the remaining volume in th ventricle at the end of systole
Incisura
A slight increase in aortic pressure. It is caused by a slights backflow of blood followed by a sudden cessation of flow
Diastolic pressure
80mm Hg
The A-V valves are:
- Triquspid valve
- Mitral valve
Semilunar valves are:
- Aortic valve
- Pulmonar valve
The stroke work output of the ventricles
Is the output of energy by the heart during each heartbeat
Cardiac output
Is the sum of all the local tissue blood flows
Poiseuille’s law
- vessle diameter has a marked effect on resistance to blood flow
- vascular resistan ce is directly propotional to the viscosity of blood and the length of the blood vessles and inversily propotional to the radius of the vessles raised to the fourth power
Conductance
Is a measure of ease of which blood can flow through a vessle and is the resiprocal of resistance
Hematocrit
- The precentage of blood comprising the cells
- Normally about 40% -> 40% of the blood is cells the rest is plasma
Vascular compliance (capacitance)
Is the total quantity of blood that can be stored in a given part of the circulation for each millimeter mercury of pressure
What three muscles is the heart composed of?
- atrial muscle
- ventricular muscle
- excitatory and conductive muscle fibers
What type of junction is in the intercalated discs?
They form permeable junctions (gap junctions)
What three muscles is the heart composed of?
- atrial muscle
- ventricular muscle
- excitatory and conductive muscle fibers
What type of junction is in the intercalated discs?
They form permeable junctions (gap junctions)
What is the normal refractory period of the ventricle?
0.25-0.30 seconds, which is about the duration of the prolonged plateau action potential
Relative refractory period is about……. Seconds
0.05
What does the term “exitation-contraction coupling” refer to?
It refers to the mechanism by which the action potential causes the myofibrils of muscle to contract.
