3 - Cardiac Physiology Flashcards
Describe functions of the heart
- BP
- routing blood through systemic and pulmonary circulations
- regulating blood supply
- one way flow
Describe structures of the heart
Pericardium
- fibrous: tough outer layer (anchor)
- serous: thin transparent inner layer
- parietal:
- visceral:
Heart Wall:
- epicardium
- myocardium
- endocardium
Describe the conducting system of the heart
1) SA node: produces action potential
2) signal passes to AV (atrioventricular nodes) a delay of 120 milliseconds occurs - atria contracts and blood moves through ventricles
3) the signal splits down the atrioventricular septum and travels down the 2 sides of the heart (supplying Purkinje fibres).
4) contraction occurs
Where are the action potentials of the CARDIAC MUSCLE transmitted?
Action Potentials are conducted from cell to cell.
What is the rate of Action Potential propogation in the cardiac muscle
Slow = small diameter of fiber + gap junctions
Where are the action potentials of the SKELETAL MUSCLE transmitted?
Action potentials are conducted along length of SINGLE fIber
What is the rate of Action Potential propagation in the SKELETAL muscle
Skeletal Muscle is faster due to larger due to larger diameter fibers.
Describe the SA node
SA node: Sinoatrial node is what originates the action potential in the right atrium.
Describe the AV node
AV node: atrioventricular node is what holds the Action Potenital, passess it down the intraventricular septum to the Purkinje fibers.
Define absolute and relative refractory periods
Absolute: Cardiac muscle cell is completely insensitive to further stimulation
Relative; cell exhibits reduced sensitivity to additional stimulation.
What are the different waves
P Wave: Atria Depolarisation
QRS Complex: Ventricle Depolarisation and Atria Repokarisation
T Wave: Ventrcile Repolariasation
What are the 5 events of the cardiac cycle?
- Isovolumetric Conteraction (during the compltion of
the QRS complex)- Ventricular Systole: period of isometric contraction
- Ventricular Systole: period of ejection
- Ventricular Diastole: period of isometric relaxation
- Ventricular Diastole: passive ventyricular filling
• Define the terms systole and diastole
Systole: Contraction
Diastole: Relaxation
• Define mean arterial pressure (MAP)
Is the average blood pressure in the aorta
MAP = Cardiac Output (CO) x Peripheral Resistance
What factors effecting MAP
- CO
- peripheral resistance: decreased blood pressure
What is CO?
Cardiac Output: the amount of blood pumped by the heart per min (formula = SV x HR)
What is SV?
Stroke Volume: Amount of blood pumped out by left ventricle per min (litres per min)
What is PR?
Peripheral resistance: Resistance of the arteries to blood flow
What is Intrinsic Regulation?
Intrinsic Regulation: Involves Neural Control.
* Parasympathetic Stimulation: supplied by vagus nerve, decreases HR, AcH is secreted and hyperpolarization of the heart. * Sympathetic Stimulation: Supplied by cardiac nerves. Innervate the SA and AV nodes, coronary vessels and the atrial and ventricular myocardium. Increases HR and force of contraction. Epinephrine and norepinephrine released. (effects > increase HR, incresaed cardiac output. Increased force of contractin causes a lower end systolic volume, heart empties to a greater extent. Limitations: heart has time to fill.
What is Extrinsic Regulation?
Extrinsic Regulation:
> Hormonal control: involves hormonal control: epinephrine (adrenaline) and norepinephrine from the adrenal medulla. Occurs in response to increased physical activity, emotional excitement and stress.
How does the heart maintain homeostasis?
- BP (controlled by baroreceptors)
- pH, CO2, O2 (receptors in hypothalamus)
- extracellular concentration (K+ conc. effects HR)
- body temp ( HR increases or decreases body temp)
How is BP maintained?
Baroreceptors
What are the effects of aging on the heart?
- Max HR decreases
- Arrhythmias are more common
- Hypertrophy of ventricles (thickening)
