Module 8 Flashcards
State the 4 main functions of the cardiovascular system
transport O2 and nutrients to cells; transport CO2 and waste from cells; help regulate body temp and pH; transport and distribute hormones and other substances
List the path of blood through the heart, starting with the superior vena cava
Superior vena cava -> right atrium -> right AV valve -> right ventricle -> pulmonary semilunar valve -> pulmonary artery -> lungs -> pulmonary vein -> left atrium -> left AV valve -> left ventricle -> aortic semilunar valve -> aorta
Name the two types of myocardial cells
contractile cells and nodal/conducting cells
Describe contractile cells and their function
like skeletal muscle cells but only one nucleus and more mitochondria; form walls of atria and ventricles, efficient at extracting O2, contain tight junctions to bind cells together and gap junctions to allow movement of ions and conduct APs from cell to cell
Describe nodal/conducting cells and their function
like nerve cells but can spontaneously generate APs without nervous input; provide self-excitatory system for the heart to generate and transmit impulses (for heartbeat)
Explain the origin of self-excitability
the sinoatrial (SA) node is the site of origin for all spontaneously generated APs in the heart
List two characteristics of the SA node leading to self-excitability
located in the upper posterior wall of the right atrium (first area to spontaneously depolarize, producing an AP); fastest spontaneous depolarization rate compared to other areas of the heart
Name the area called the pacemaker of the heart and why
the SA node because it is the origin of every AP in the heart, has no stable resting membrane potential
Describe sequence of events leading to AP in SA node
Na+ and Ca++ move down concentration gradient into cell, slowly depolarizing; K+ permeability decreases over time while Na+/K+ pump continues working; cell depolarizes from -60mV to -40mV (threshold) called a pacemaker potential; special Ca++ voltage-gated channels open, Ca++ rapidly flows in, producing depolarization phase and SA node AP; voltage-gated K+ channels open as Ca++ channels close to repolarize cell
Describe the pacemaker potential
slow spontaneous depolarization of the SA node, responsible for setting the pace of the heartbeat, any alteration affects heart rate
Explain what an ECG is
electrical potentials generated by heart during the cardiac cycle read by electrodes on the skin picking up the electrical current conducted by fluid around the heart to the surface of the body
Describe the P wave on an ECG
electrical activity in the heart associated with depolarization of atrial muscle leading to contraction
Describe the large QRS complex on an ECG
produced by depolarization of ventricular muscle prior to contraction, obscures wave associated with repolarization of atrial muscle
Describe the T wave on an ECG
result of repolarization of ventricular muscle as it relaxes
Explain what an ECG can show about the health of a heart
can see how often atria and ventricles contract, whether the depolarizations and repolarizations are of the correct magnitude, can see if ventricles are contracting before atria have finished contracting
Name the two phases of the cardiac cycle
systole (period of isovolumetric contraction) and diastole (period of isovolumetric relaxation)
List the 5 phases of the cardiac cycle, when each ECG wave occurs, and what valves open and close in each step
atrial systole (P wave ends) (AV valve opens); isovolumetric ventricular contraction/early ventricular systole (QRS complex) (AV valve closes); ventricular systole/ejection period (T wave) (aortic valve opens); early ventricular diastole/isovolumetric relaxation phase (aortic valve closes); late ventricular diastole (P wave begins) (AV valve opens)
Name the percent of blood that enters the ventricles from the atrial contraction and ventricle relaxation
20-30% from atrial contraction (atrial systole); 70-80% from ventricle relaxation (during late ventricular diastole)
Name how many heart sounds there are and what causes each
3; first produced by AV valves closing, low pitch long duration; second produced by aortic and pulmonary semilunar valves closing, high pitch small duration; third middle of diastole, caused by blood flowing with rumbling motion into almost filled ventricles, difficult to hear
Define cardiac output (CO) and the average at rest, during exercise, and for highly trained athletes
the amount of blood each ventricle can pump in one minute; average 5L/min; during exercise 20L/min; for athletes 35-40L/min
Describe the equation for cardiac output
CO = HR x SV (mL)
Define heart rate (HR) and the average at rest
the number of times the heart beats in one minute; 70 beats per minute (bpm)
Define stroke volume (SV) and the average at rest
the amount of blood pumped by one ventricle during one contraction/heartbeat; 70mL/beat
Describe the factors controlling heart rate via the PSYN
PSYN nerves go mainly to SA and AV nodes, few to atrial and ventricular muscles; decreases heart rate by releasing ACh, causing membrane potential to hyperpolarize and slope of pacemaker potential to decrease
