Module 8

Question 1

State the 4 main functions of the cardiovascular system

Answer 1

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

Question 2

List the path of blood through the heart, starting with the superior vena cava

Answer 2

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

Question 3

Name the two types of myocardial cells

Answer 3

contractile cells and nodal/conducting cells

Question 4

Describe contractile cells and their function

Answer 4

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

Question 5

Describe nodal/conducting cells and their function

Answer 5

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)

Question 6

Explain the origin of self-excitability

Answer 6

the sinoatrial (SA) node is the site of origin for all spontaneously generated APs in the heart

Question 7

List two characteristics of the SA node leading to self-excitability

Answer 7

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

Question 8

Name the area called the pacemaker of the heart and why

Answer 8

the SA node because it is the origin of every AP in the heart, has no stable resting membrane potential

Question 9

Describe sequence of events leading to AP in SA node

Answer 9

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

Question 10

Describe the pacemaker potential

Answer 10

slow spontaneous depolarization of the SA node, responsible for setting the pace of the heartbeat, any alteration affects heart rate

Question 11

Explain what an ECG is

Answer 11

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

Question 12

Describe the P wave on an ECG

Answer 12

electrical activity in the heart associated with depolarization of atrial muscle leading to contraction

Question 13

Describe the large QRS complex on an ECG

Answer 13

produced by depolarization of ventricular muscle prior to contraction, obscures wave associated with repolarization of atrial muscle

Question 14

Describe the T wave on an ECG

Answer 14

result of repolarization of ventricular muscle as it relaxes

Question 15

Explain what an ECG can show about the health of a heart

Answer 15

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

Question 16

Name the two phases of the cardiac cycle

Answer 16

systole (period of isovolumetric contraction) and diastole (period of isovolumetric relaxation)

Question 17

List the 5 phases of the cardiac cycle, when each ECG wave occurs, and what valves open and close in each step

Answer 17

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)

Question 18

Name the percent of blood that enters the ventricles from the atrial contraction and ventricle relaxation

Answer 18

20-30% from atrial contraction (atrial systole); 70-80% from ventricle relaxation (during late ventricular diastole)

Question 19

Name how many heart sounds there are and what causes each

Answer 19

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

Question 20

Define cardiac output (CO) and the average at rest, during exercise, and for highly trained athletes

Answer 20

the amount of blood each ventricle can pump in one minute; average 5L/min; during exercise 20L/min; for athletes 35-40L/min

Question 21

Describe the equation for cardiac output

Answer 21

CO = HR x SV (mL)

Question 22

Define heart rate (HR) and the average at rest

Answer 22

the number of times the heart beats in one minute; 70 beats per minute (bpm)

Question 23

Define stroke volume (SV) and the average at rest

Answer 23

the amount of blood pumped by one ventricle during one contraction/heartbeat; 70mL/beat

Question 24

Describe the factors controlling heart rate via the PSYN

Answer 24

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

Question 25

Describe the factors controlling heart rate via the SYN

Answer 25

SYN nerves go to SA and AV nodes and strong innervation to ventricular muscle; releases norepinephrine, causing Na+ and Ca++ channels to open, more ions enter SA nodal cells, pacemaker potential reaches threshold faster

Question 26

Describe vagal tone

Answer 26

without PSYN or SYN, heart rate would be 100bpm, but constant PSYN activity keeps heart rate at 70bpm through vagus nerve transmitting signals from PSYN to the heart

Question 27

Describe the equation for stroke volume

Answer 27

SV = EDV - ESV

Question 28

Define EDV and the average at rest

Answer 28

end diastolic volume; the amount of blood in the ventricle at the end of diastole, or just before it contracts; usually 120mL at rest

Question 29

Define ESV and the average at rest

Answer 29

end systolic volume; the amount of blood in the ventricle at the end of systole, or just after it contracts; usually 50mL at rest

Question 30

Name the 3 things that can alter stroke volume

Answer 30

input from the ANS - either the PSYN or the SYN; EDV and preload; ESV

Question 31

Describe how input from the PSYN alters stroke volume

Answer 31

decreases force of contraction by releasing ACh onto cardiac muscle, decreasing Ca++ entering cells

Question 32

Describe how input from the SYN alters stroke volume

Answer 32

releases norepinephrine onto cardiac muscle, increases Ca++ entering cells, leads to more forceful contraction

Question 33

Define preload

Answer 33

the “load” on the heart just before it contracts (directly related to EDV); load comes from blood in ventricle that stretches muscle of the heart

Question 34

Describe the Frank-Starling Law of the Heart

Answer 34

law states that an increase in EDV will cause an increase in SV, and vice versa

Question 35

Describe the main way to change EDV

Answer 35

squeezing veins to fill heart with more blood before it contracts (increasing venous return); can be done by exercising or activating SYN to innervate smooth muscle in walls of veins