CH. 6
Cardiac muscle cells have these characteristics
a. multinucleated, like skeletal muscle
b. branched
c. linked by intercalated discs
d. stimulated involuntarily
If pH of the blood is low (acidic), the oxyhemoglobin-dissociation curve will shift ___________.
to the right
Resting heart rates of elite endurance athletes can be approximately
45 beats/min
In general, the sympathetic nervous system causes __________ systemic blood vessels.
vasoconstriction of
Most of the carbon dioxide is transported through the veins as_______.
bicarbonate
Veins have a _____ partial pressure of oxygen than arteries.
lower
Most of the oxygen is transported through the arteries as_______.
oxyhemoglobin
Mechanisms that help return blood to the heart include
a. valves in the veins
b. muscle pump
c. respiratory pump
At rest, _____________ receive(s) about 50% of cardiac output, but during exercise receives less than 10%.
the liver & kidneys
Which type of blood vessel is primarily responsible for redirecting (resistance vessels) blood flow?
arterioles
_________ are located in the aortic arch and carotid arteries and are sensitive to changes in blood pressure.
baroreceptors
When the oxyhemoglobin curve shifts to the right during exercise, what is the result?
O2 unloading becomes more difficult at the muscles
Urine produced after strenuous exercise is most likely _______ compared to urine produced before exercise.
acidic
In the heat, more blood flow will be redirected to the _______.
skin
Which is the main pacemaker of the heart _____________.
SA node
The rate-pressure product is an index of
(RPP=HRxSystolicBP)
myocardial metabolism
When venous blood from exercising and nonexercising tissues is included in the calculation, it is called
arterial-mixed venous O2 difference
a. reduces preload by temorarily slowing venous return of blood to the heart
b. reduces cardiac output
c. increases, then lowers arterial blood pressure
The Valsalva maneuver
Chemoreceptors stimulate the CNS to increase breathing rate and depth, which occurs when
excess CO2 needs to be "blown off"
The increase in heart rate at the very beginning of exercise (before HR reaches 100 bpm) is due to
withdrawal of vagal stimulation
When you inhale, which of the following occurs as a result of the respiratory pump?
Thoracic vena cavae fill
When PO2 is approximately 20 mmHg, what is myoglobin doing?
loading O2
Norepinephrine leads to an increase in stroke volume, this is mainly due to
increased contractility
The mechanism that underlies preload's (venous return of blood to heart) effects on stroke volume is the
Frank-Starling mechanism
Which chamber of the heart has the thickest walls?
left ventricle