Physiology Flashcards
Cardiac output
the amount of blood pumped into circulation by each ventricle in 1 minutes (Stroke Volume x Heart Rate)
Cardiac muscle
innervation is not required from initiating contraction, myogenic via pacemaker potentials, modifies contraction, excitatory/inhibitory, contribuites to gradation of contractile rate and strength
has gap junctions
Skeletal muscle
innervated by the somatic nervous system- acetylcholine, neurogenic, initiates contraction
No gap junctions
Steps of action potential and ion movement
Phase 0: Local depolarization where voltage gated sodium channels open to become more positive
Phase 1+2: Membrane potential is sustained, decreased by calcium
Phase 3: Repolarization by rapidly returning to negative membrane potention by inactivating calcium channels and K+ rapidly moves outwards
Phase 4: ATP dependent Na/K pumps move sodium out and potassium back into the cell to re-establish same ionic distribution as before
Atrial Depolarization
where there is a + voltage detected by an electrode generating P wave
P wave corresponds to
atrial depolarization
Q wave corresponds to
early ventricular depolarization where as movement across septum wall
R wave corresponds to
ventricular depolarization as the action potential conducted towards the apex base via Purkinje fibers.
S wave corresponds to
The late ventricular depolariation where there is a negative volatage detected by the electrode
T wave corresponds to
tje ventricular repolarization where the outside surface of the ventricle is last to depolarize but first to be repolarized.
Tachycardia
short time between R waves
Bradycardia
long time between R waves
Preload
the filling pressure that is a determinate of end-diastolic volume by venous return
What factors influence venous return and therefore the End-Diastolic volume
1) Venous valves - prevent back flow and therefore increase venous return
2) Pressure gradient: between the central venous pressure and the right atrial pressure
3) Venoconstriction: under sympathetic tone, increases the pressure and blood flow back into the right atrium
4) Arteriolar dilation: Increasing the radius, decrease the resistance to increase flow and venous return
5) Skeletal muscle and respiratory pump
6) Increasing blood volume, greater the mean circulatory filling pressure
What are the determinants of the End-Systolic Volume?
1) Afterload: all factors that contribute to total myocardial wall stress or tension during systolic ejection. by increasing afterload you increase stroke volume and increase end-systolic volume
2) Contractility of myocardial cells (extrinsic) by neural control or hormonal control
Steps of heart contraction
The mitral/bicuspid valve opens allowing the filling phase from blood from the LA to the LV. The mitral valve then closes where isovolumic contraction occurs until the aortic valve opens causing ejection of blood into the systemic circulation. Once aortic pressure is greater than the LVP, the aortic valve closes (second heart sound) then isovolumic relaxation occurs where the aortic and mitral valves are closed and the myocardium relaxes. Once LAP is greater than the LVP the mitral opens
S1
the sound of the closure of atrioventricular valves (systole)
low pitched, occurs at the onset of ventricular ejection
S2
the sound of the closure of the aortic and pulmonic valves (diastole)
higher pitch, shorter/shaper, caused by the change in direction of blood flow in the aorta and and pulmonary trunk at the end of the systole
S3
the abrupt checking of the ventricular wall. In dogs, detecting S3 may be associated with dilated cardiomyopathy
