ROT 2: Human Heart Function and Blood Pressure

Question 1

In humans, the pacemaker cells of the heart are located near the ___ atrium near the entrance of the superior vena cava and are called the ___-____ node.

Answer 1

In humans, the pacemaker cells of the heart are located near the RIGHT atrium near the entrance of the superior vena cava and are called the SINO-ARTRIAL node.

Question 2

The AV node, located within the ____ septum, relays the electrical impulse from the ___ to the ____

Answer 2

AV node located within the lower INTERATRIAL septum. Relays the impulse from the ATRIA to the VENTRICLES.

Question 3

After the electrical impulse passes through the AV node, it enters the fiber tract known as the ___ ___ ____. This short pathway subdivides into right and left branches.

Answer 3

Bundle of His

Question 4

the smallest conductive elements, aka the ___ fibers, are distributed throughout the inner walls of the ____.

Answer 4

aka the Purkinje fibers. Distributed throughout the inner walls of the VENTRICLES. makes CONTACT with CONTRACTILE elements of the heart.

Question 5

In terms of electrical impulse, when will the ventricles fully contract?

Answer 5

after being dispersed throughout the entire inner surgace of the ventricles, and after the impulse moves towards the outer surface of the heart as a generalized wave of depolarization.

Question 6

P wave represents

Answer 6

atrial depolarization.

Question 7

QRS complex represents

Answer 7

ventricular depolarization?

Question 8

When do we see atrial repolarization on the ECG?

Answer 8

we don’t. It occurs at the time of the QRS complex, but it is overshadowed compared to ventricular depolarization.

Question 9

T wave represents

Answer 9

ventricular repolarization.

Question 10

Systole is ___ and diastole is ___

Answer 10

systole = contraction, diastole = relaxation.

Question 11

What are the AV valves?

Answer 11

tricuspid and bicuspid.

Question 12

when does the “lubb” sound occur? the “dubb” sound? When on the ECG?

Answer 12

lubb sound: occurs at the BEGINNING of ventricular contraction. Associated with the CLOSURE of the AV valves that separate the atria and ventricles. Occurs at the R-S point of ECG.

dubb sound: occurs at the START of ventricular RELAXATION. Due to closure of SEMILUNAR valves. Occurs at T point of ECG

Question 13

On the ECG, when is “systole”? diastole?

Answer 13

systole occurs from R to T. diastole (ventricular relaxation) is from T to P.

Question 14

when the ventricles of the heart contract, blood is pumped into the __ ___ and ___

Answer 14

pulmonary trunk and aorta

Question 15

Starting from the left side of the heart, name the blood vessels that blood progressively flows through

Answer 15

aorta, arteries, arterioles, capillaries, venules, veins, then back to atria.

Question 16

When the heart pushes blood into the arteries, what happens to the pressure?

Answer 16

there is a sudden increase in pressure, which slowly declines until the heart contracts again.

Question 17

when is the force on the blood vessel walls the greatest? in terms of BP, what is this called?

Answer 17

during ventricular systole (ventricular contraction), force on the blood vessel walls is greatest. Known as SYSTOLIC PRESSURE.

Question 18

when is the force on the blood vessel walls the weakest? in terms of BP, what is this called?

Answer 18

during ventricular diastole, the pressure falls to its lowest value. Known as DIASTOLIC PRESSURE.

Question 19

Blood pressures are reported in terms of ____

Answer 19

mmHg.

Question 20

What is pulse pressure?

Answer 20

the difference between systolic and diastolic pressures Pp= Ps-Pd.

Question 21

Equation for mean arterial pressure

Answer 21

MAP = Pd + (1/3 (Ps-Pd))

MAP = average pressure in the ARTERY throughout the cardiac cycle.

Question 22

What is a dichrotic notch?

Answer 22

a small fluctuation in pressure between systolic and diastolic points of a pulse pressure graph. Related to BACKFLOW of blood in the ascending aorta just prior to the closure of the aortic valve.

Question 23

___ ___ is the amount of blood pumped by one side of the heart in one minute.

Answer 23

cardiac output

Question 24

__ ___ is the amount of blood pumped by one ventricular beat

Answer 24

stroke volume

Question 25

formula for cardiac output

Answer 25

CO = HR x SV

Question 26

An increase in cardiac output can ____ the BP

Answer 26

increase the BP because there is more blood in a vessel at a given time.

Question 27

The primary control of heart rate is through ____ innervation of the heart.

Answer 27

autonomic

Question 28

sympathetic stimuli ____ the rate, and parasympathetic simuli ____ the rate.

Answer 28

sympathetic stimuli INCREASE the rate and FORCE OF CONTRACTION, and parasympathetic simuli DECREASE the rate.

Question 29

What is venous return?

Answer 29

the volume of blood returning to the heart.

Question 30

3 factors that influence stroke volume

Answer 30

1) venous return
2) sympathetic nerve activity which causes cardiac muscle cells to contract with greater FORCE
3) levels of circulating epinephrine.

All 3 things occurs during exercise.

Question 31

What is peripheral resistance

Answer 31

general resistance to blood flow in arteries.

Question 32

peripheral resistance is principally due to :

What does this cause?

Answer 32

the contraction of SMOOTH MUSCLES in the walls of the arteries. Arteries are located between the heart and the arterioles, and constriction of the arterioles elevates arterial blood pressure.

Question 33

changes in arterial pressure occur due to changes in __ __, ___ ___ , or both

Answer 33

cardiac output, peripheral resistance, or BOTH.

Question 34

cardiac output and peripheral resistance are influenced by regulatory centers in the brain located in the ___

Answer 34

medulla.

Question 35

In terms of ECG amplitude, what type of person would exhibit larger waves? smaller waves?

Answer 35

waves may have a higher amplitude with muscular hypertrophy, aka someone with ATHLETIC PHYSIQUE, or a thin chest wall.

waves may appear reduced in obese people.

Question 36

On an ECG, what does the PR interval represent?

Answer 36

represents how long it has taken the electrical impulse to travel from the SA node through the atria and through the AV node to the bundle of His in the ventricles.

aka time delay between the beginning of depolarization of the atria and depolarization of the ventricles.

Question 37

What happens to the PR interval if premature ventricular contractions occur? if there is an incomplete atrioventricular block?

Answer 37

if there is a premature ventricular contraction: the PR interval will be shorter

if there is a block: it will be considerable longer.

Question 38

What does it mean if a person’s ECG has P waves differing in shape and size?

Answer 38

may mean irritability in the ATRIAL TISSUE or damage near the SA node.

Question 39

What is a compensatory pause and why/when does this occur?

Answer 39

compensatory pause: prolonged interval prior to the next contraction. Occurs when there was a premature systole/contraction of the heart. It occurs to maintain cardiac output and regain rhythym. The pause allows for increased time of ventricular filling, resulting in more blood being ejected from the heart in the subsequent contraction.

Question 40

A person is suspected of having a myocardial infarction (heart attack). what segment of the ECG is most tell tale?

Answer 40

ST segment. Normally it is a flat line, but an abnormality provides the earliest clues in diagnosing myocardial infarction.

Question 41

How can various degrees of heart block be observed on an ECG? (particularly SA node blockage)

Answer 41

A heartblock reflects a separation or disruption in the conduction system of the heart.

If there is a disruption in conduction, another pacemaker site will be the pacemaker.

If there is a blockage in SA node, there is a LONGER PQ interval, and it takes longer for electrical signal to move through the ventricle.

APs from the SA node may not be able to move to AV node, results in the ABSENSE of a QRS complex, but the presence of P wave. You’d have more P waves than QRS waves because the ventricle cannot cotnract.

QRS complex may widen because it takes longer for electrical stimulus to move through the ventricle.

Question 42

Why does SA node acts as the primary pacemaker of the heart?

Answer 42

because it depolarizes the fastest.

Question 43

Why is an ECG an important diagnostic tool when evaluating the response to the stress of physical exercise?

Answer 43

you can see premature extrasystoles. Many extrasystoles may reflect O2 deprivation in the cardiac muscle.

Question 44

cardiac output for this lab equation

Answer 44

CO= SV x (pulse pressure/40) x HR

Question 45

Briefly explain the effects of standing up from a reclining position, on HR and BP

Answer 45

in general, the main effect on VENOUS RETURN TO THE HEART is GRAVITY. Standing from reclining causes blood to pool in your legs, causing a sharp drop in BP followed by a general increase in HR to compensate, resulting in an overshoot and increase in BP.

Pooling of blood in veins of legs when standing causes a DECREASE in venous return due to gravity. Takes a while to get to the heart.

Question 46

How does the body exert BP and HR effects after reclining? (mechanism)

Answer 46

through baroreceptors. They are stretch receptors that detect the sharp drop in BP when you standing up quickly from reclining. They send afferent signals to the cardio center in the MEDULLA, which stimulates the sympathetic nervous system and acts on BETA 1 receptors in the heart, increasing the force of the heart.

increaseing force of contraction = higher cardiac output and higher blood pressures.

cranking up SNS also increases vasocontstriction in the ARTERIOLES, which also contributes to increase in bp.

Question 47

In the cardiovascular control center in the medulla, the cardio_____ governs sympathetic input, and the cardio____ center governs parasympathetic input.

Answer 47

In the cardiovascular control center in the medulla, the cardioACCELERATOR governs sympathetic input, and the cardioINHIBITOR center governs parasympathetic input.

Question 48

Baroreceptors can be found in:

Answer 48

1) the aortic arch

2) the carotid sinus.

Question 49

Orthostatic hypotension

Answer 49

poor circulation resulting in passing out when stand up from lying down because of a huge BP drop.

Question 50

Explain the effects of exercise on HR and BP. What happens 5 minutes into exercise? 5 minutes into stopping exercise?

Answer 50

1) your body starts to prepare for exercise subconsciously, resulting in an increase in sympathetic NS activity, and a bit of inhibition of the parasympathetic system.
2) 5 minutes after exercise, BP INCREASES because symp stimulations causes increase in Cardiac output due to more forceful contractions beucase of BETA 1 STIMULATION on the myocardium (ion influx causes faster APs)
3) Beta 2 receptors in the skeletal muscle are also activated by PHYSICAL ACTIVITY because the adrenal medulla releasesNE and E. (2=inhibitory) and thus promotes vasodilation o f skeletal muscle ARTERIOLES so muscles can work harder. Beta 2 in the gut stops digestion during working out.

5 minutes after exercising
-there is a bit of a drop in sympathetic NS activity. Arterial BP may drop a bit lower and baroreceptors bring things back to normal by detecting changes and relaying them to the cardiocontrol center in the medulla.

Question 51

How does beta 1 stimulation on myocardium increase force of contractioN?

Answer 51

beta 1 receptor activations facilitates an increase in Na+ channels and Ca2+ flux speeds up rate of myocyte depolarization.

Ca2+ influx in this case primarily helps with facilitate muscle contraction rather than being involved with the plateau phase of the cardiac myocyte AP. Ca2+ binds with troponin-tropomyosin complex of the cardiac cell to initiate STRONGER CONTRACTIONS because of MORE CROSS BRIDGING.

Question 52

When working out,there is a general increase in __ ___ resistance. What does this cause?

Answer 52

increase in total peripheral resistance. Causes an increase in BP and increase in HR. Increase in HR and BP causes an increase in venous return

Question 53

How would you expect atherosclerosis to affect systolic and diastolic BP?

Answer 53

Atherosclerosis is the hardening of the arteries. There is a loss of elasticity and results in a fixed diameter of vessels.

Because the vessels cannot stretch, the artery cannot accommodate for when a large volume of blood is pushed into it. Therefore, the pressure exceeds greatly during heart contraction (systolic BP goes up)

Likewise, the fixed diameter prevents the arteries from bending back after a large amount of fluid just passed through it, and thus there is a huge drop in pressure in during relaxation when there is no blood in the artery. (diastolic BP goes down)

the increase in systolic BP and decrease in diastolic BP = INCREASE PULSE PRESSURE in people with atherosclerosis.

Question 54

What factors affect venous return in the body?

Answer 54

1) sympathetic activity. arteriolar vasoconstriction immediately reduces flow through increased resistance, therefore, there is less blood moving through to veins and thus decreases venous return.

2) skeletal muscle.
contraction of external muscle resutls in external venous compression, increasing venous pressure and squeezing blood towards the heart. Results in increase in venous return.

3) Venous valves
large veins have one way valves that prevent backflow and work against gravity effects. Damage to these valves will cause a decrease in venous return

4) Respiratory Pump
- the decreased pressure in the chest promotes venous return because blood will flow from the higher pressure body through the veins to the lower pressure chest region where the heart is

5) cardiac suction
- the expansion and contraction of the VENTRICLES causes a pressure differential, which works as a suction effect on the blood helping pull it towards the heart.

6) increased blood volume
- all blood must circulate through the veins at some point. If there is more blood in the veins, more blood will be returned to the heart.

Question 55

what is the valsalva manoevre and its effects on venous blood pressure and heart rate?

Answer 55

during the manoever, you pretend to exhale air. TESTS THE RESPIRATORY PUMP MECHANISM OF VENOUS RETURN

The diaphragm goes up, and BP goes up but you keep the air in your thoracic cavity. This prevents VENOUS RETURN. You can raise your hand higher because blood stays in peripheral veins rather than moving into chest cavity BECAUSES THERE NO PRESSURE GRADIENT LIKE USUAL!

Question 56

After the valsalva manoevre, what happens to arterial pressure?

Answer 56

this manouvre causes a decrease in venous return which means a decrease of blood returning to the heart which means a decrease of blood being pumped back out of the heart

therefore, causes a deccrease in arterial pressure. This is only transient; HR picks up after the baroreceptor reflex kicks in when detecting the drop in arterial pressure.

Question 57

During Valsalva, you should see a ___ in heart rate. Once you release valsalva, you get a surge of blood back to the heart, causes a ____ in BP and ___ in heart rate.

Answer 57

During Valsalva, you should see a DECREASE in heart rate (because there is less blood going to the heart that needs to be pumped). Once you release valsalva, you get a surge of blood back to the heart, causes a INCREASE in BP and INCREASE in heart rate.