APK 3110C Study Guide - Quiz Guide: Atrioventricular Node, Purkinje Fibers, Tricuspid Valve

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17 Jan 2016
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PET3380 Exam II Study Guide
1. What are the expected training effects from aerobic exercise on: HR, SV and Q?
HR: heart rate; max heart rate does not change, but overall heart rate decreases (lower HR at
SV: stroke volume; SV eventually hits a plateau, with max at about 40% aerobic capacity; with
training you can increase your max SV because the myocardium becomes stronger and
contraction can generate more force, so the ventricles can hold more blood
Q: cardiac output(blood pumped by the heart (in Liters) per minute); increases with training
2. How are the electrical impulses passed through the heart? What are the physiological events associated
with the beat of the heart?
SA node atria AV node AV bundle (Purkinje fibers) ventricles
SA node: depolarizes and repolarizes to provide the innate stimulus for heart action, which is
why it is sometimes called the “pacemaker”; sets the heart beat
impulses start at the SA node and spread through the atria to a spot near the tricuspid valve called
the AV node
a short delay occurs after that to allow the atria to contract and propel blood into the ventricles
following the AV node comes the AV bundle, also referred to as the bundle of His
this bundle spreads farther into the Purkinje fibers, which form distinct bundle branches that
penetrate the right and left ventricles
othese fibers transmit impulses about 6 times faster than normal ventricular fibers
physiological events:
ocan use an electrocardiogram to find these physiological signs
oP wave: atrial depolarization
oQRS complex: ventricular depolarization
oS-T segment: ventricular repolarization
if there is depression in this S-T segment, it is a good predictor of an upcoming
heart attack because you aren’t getting enough O2 to the heart
oT wave: ventricular repolarization
oQ-T interval: ventricular depolarization and repolarization
3. Understand these relationships at rest, during sub maximal and maximal exercise.
a) Q = HR x S
Q depends on rate of pumping and how much blood is ejected from heart with
each stroke
b) Q = VO2 / a-vO2 diff
an increase in a-vO2 difference during exercise is due to an increase in the
amount of O2 taken up and used for production of ATP by skeletal muscle
c) Q = P / R
Darcy’s Law
also Q = MAP / TPR
MAP: mean arterial pressure
TRP: total peripheral resistance
increasing resistance decreases Q
d) VO2 = Q x a-vO2 diff
Fick equation
increasing Q or a-vO2 difference would increase VO2
4. What is blood flow redistribution and which tissues are affected? HOW?
Blood flow redistribution: blood flow from one organ to another by vasoconstriction in one
(inactive muscle) and vasodilation in the other (active muscle)
important during exercise because muscles needing blood are provided with more blood from
organs that do not need as much blood flow during exercise
during exercise, blood flow to the kidneys and visceral organs is greatly reduced, to make
available about 600 mL of oxygen each minute to be used by the active muscles
blood flow to the sin greatly increases during light and moderate exercise in response to the rise
in core body temperature; during max, blood flow to the skin is restricted to active muscles
cerebral and cardiac blood flow also increases during exercise so these vital organs can receive
the oxygen they need
two factors cause this blood flow redistribution: hormonal vascular regulation and local
metabolic conditions
5. What is venous return? What factors influence venous return?
venous return: the flow of blood back to the heart through the venous circuit; the output of the
heart depends on venous return
during exercise, venous return is pulsitile
factors affecting venous return:
ovenoconstriction: decrease volume capacities
oone way valves (pressure and gravity composition)
in veins; prevent back flow, especially to the lower extremities
omuscle pumps (mechanical process): squeezes vessels
as muscles contract, they compress veins and assist in pushing blood back to the
olungs (pressure and muscle composition): respiratory pump action
rhythmic pattern of breathing also provides a mechanical pump that increases
venous return by alternating changes in thoracic and abdominal pressures
6. Describe the immediate (acute) adjustments made by the heart and circulatory system to allow for
physical activity. Give neural and hormonal mechanisms. Give changes from rest, to sub-maximal, to
heavy-maximal exercise.
two factors increase SV: 1) increasing amount of blood in ventricle before systole (increase end-
diastolic volume) and 2) decreasing the amount of blood left in the ventricles at the end of
systole (decrease end-systolic volume)
Frank-Starling Law: increasing EDV in left ventricle causes a stretch of ventricular
myocardium which enhances contractility as well as SV
adaptations to aerobic training:
oat rest
resting HR reduces, but the resting Q does not differ between trained and
untrained individuals; so, it is the SV that is elevated at rest for trained individuals
osubmaximal exercise
for a trained person, HR is lower at a given workload (% VO2 max), but SV will
be greater at a given workload
Q will be the same between trained and untrained people
oat maximal exercise
trained individual achieves larger Q during exercise because of a larger stroke
volume than that of an untrained person
HR max does not change with training
7. Define cardiac output. EXPLAIN. How cardiac output is measured (Fick method)?
cardiac output: the amount of blood pumped by the heart during a one-minute period
maximal value reflects functional capacity of cardiovascular system
depends on heart rate (rate of pumping) and stroke volume (quantity of blood ejected with each
cardiac output (Q) = HR * SV
Fick principle: Q = (VO2 / a-v O2 difference) * 1002
oused to calculate cardiac output
oa-v O2 difference: average difference between oxygen content of arterial and mixed-
venous blood; mL per 100 mL of blood
oVO2: volume of oxygen consumed in one minute; mL/min
8. Give the mechanisms controlling stimulation in the heart rate prior to and during activity.
extrinsic controls: accelerate heart in anticipation before exercise begins, and then rapidly
adjust to intensity of physical effort; changes made by nerves that directly supply myocardium
and chemical messengers (neurotransmitters and hormones) that circulate the blood
osympathetic influence: causes the heart to beat faster (tachycardia)
oparasympathetic influence: causes the heart rate to be reduced (bradycardia)
intrinsic controls: the heart maintains its own rhythm; has spontaneous activity: muscle nerves
of heart can be excited
osee question 2
at rest, PNS keeps the HR low
during activity or exercise, SNS increases HR
9. Describe the effects of parasympathetic and sympathetic nerves on cardiac function.
parasympathetic nerves: cardio-accelerator nerves, from the nerve network in the spinal cord
omostly surrounds SA node, but AV too
odecreases heart rate and decreases rate of impulse conduction through the AV node
sympathetic nerves: comes from the Vagus nerve, from the medulla
omore abundant surrounding the AV node than the SA node
oincrease heart rate, increase force of contraction, increase rate of contraction, increase
ochronotropic effect: makes heart beat faster
oinotropic effect: makes heart beat harder, increasing contractility
10. EXPLAIN the indirect method of measuring blood pressure. What is systolic, diastolic pressure? What
changes occur during exercise? EXPLAIN peripheral resistance and factors which modify resistance to
blood flow in exercise.
blood pressure: force exerted by blood against the arterial walls during a cardiac cycle
systolic pressure: provides an estimate of the work of the heart and force that blood exerts
against the arterial walls during ventricular systole (contraction phase of heart)
diastolic pressure: during relaxation phase of cardiac cycle (diastole); indicates ease that blood
flows through arterioles into the capillaries (peripheral resistance
with high peripheral resistance, pressure in arteries after systole doesn’t rapidly dissipate, but it
remains elevated for a longer portion of the cardiac cycle
auscultation method: using a blood pressure cuff to find someone’s BP