The diameter of blood vessels varies under the control of ________ neurons, which cause the diameter to ________.
answer
sympathetic; either increase or decrease, depending upon the type of receptor present
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Neurons in the parasympathetic pathway use which of the following neurotransmitters?
answer
ACH
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What type of acetylcholine receptor is present in the postganglionic neurons and on the target tissue in autonomic pathways?
answer
nicotinic on the postganglionic neurons and muscarinic on the target tissue
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What is a varicosity in the autonomic nervous system?
answer
A series of swollen ends that act as synapses
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In the autonomic nervous system, neurotransmitter activation of its receptor terminates when the neurotransmitter is metabolized by enzymes in the extracellular fluid, or when it diffuses away. Which other mechanism leads to termination of neurotransmitter activity?
answer
Active transport into surrounding cells
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The neurotransmitter that controls skeletal muscle causes which of the following?
answer
muscle contraction
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How do the synapses of the autonomic nervous system differ from a neuromuscular junction (NMJ)?
answer
Neurotransmitter receptors are concentrated on the postsynaptic membrane in the NMJ but diffusely arranged across the tissue in a varicosity.
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What is the trigger for ACh release into the synaptic cleft of a neuromuscular junction?
answer
An action potential at the axon terminal opens voltage-gated Ca2+ channels.
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What would be the effect of ACh binding to its receptor on the postsynaptic muscle cell?
answer
Na+ would flow into the cell and K+ would flow out of the cell.
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What immediately follows hydrolysis of ATP during muscle contraction?
answer
rotation of the myosin head to the cocked position
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Which is an example of an antagonistic muscle group?
answer
Gastrocnemius and tibialis anterior
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Which structural protein of skeletal muscle also acts as an enzyme?
answer
Myosin heavy chains
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What causes the latent period during excitation-contraction coupling?
answer
Time is required for calcium release, diffusion, and binding to troponin.
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How are cardiac muscle cells similar to smooth muscle cells?
answer
They are electrically linked to one another.
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Which type of muscle fiber(s) is/are uninucleate?
answer
smooth and cardiac
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The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
answer
A myosin head bound to actin
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What structure is the functional unit of contraction in a skeletal muscle fiber?
answer
the sarcomere
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Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
answer
Calcium ions are stored in the sarcoplasmic reticulum.
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After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
answer
ATP binds to the myosin head.
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How does the myosin head obtain the energy required for activation?
answer
The energy comes from the hydrolysis of ATP.
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What specific event triggers the uncovering of the myosin binding site on actin?
answer
Calcium ions bind to troponin and change its shape.
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When does cross bridge cycling end?
answer
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
question
The ability to distinguish different pitches (frequencies) of sound results from which of the following?
answer
changing sensitivity to pitch along the length of the basilar membrane
question
Which of the following structures contains sensory receptors for hearing?
answer
cochlea
question
Choose the correct order of structures that blood would contact as it traveled from the left atrium through the blood vessels and back to the right atrium. 1)abdominal aorta 2)ascending arteries 3)inferior vena cava 4)hepatic artery 5)superior vena cava 6)left ventricle 7)ascending veins
answer
6,1,4,7,3
question
why does blood flow through the whole body?
answer
to establish a pressure gradient
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The net pressure gradient in the cardiovascular system is created by _____.
answer
heart contraction
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heart valves open and close in response to
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pressure changes in heart chambers
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Changes in the radius of _____ has the most impact on resistance to blood flow, because radius can be changed quickly and precisely.
answer
arterioles
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As blood flows away from the heart, how does overall blood pressure in vessels change? Why?
answer
Blood pressure decreases, because of the effects of friction between the vessel walls and the moving blood.
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As blood flows away from the heart, how does overall blood pressure in vessels change? Why?
answer
Blood pressure decreases, because of the effects of friction between the vessel walls and the moving blood.
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Blood flows through a vessel at a particular flow rate and velocity. What happens to the velocity of the blood flow through that vessel after it constricts, narrowing its diameter? You may assume that the flow rate is unchanged.
answer
increases
question
In which tube would the flow be the highest?
Tube 1: Beginning pressure = 25mm Hg, ending pressure = 1mm Hg
Tube 2: Total hydrostatic pressure = 24mm Hg
Tube 3: Beginning pressure = 100mm Hg, ending pressure = 78mm Hg
answer
tube 1
question
If the radius of a tube decreases by half, what would happen to the resistance to fluid flow?
answer
resistance would increase 16 times
question
What is an advantage to the longer duration of cardiac action potential compared to the skeletal muscle action potential?
answer
The longer duration prevents tetanic contraction, which ensures that the heart chambers will relax and refill with blood before the next contraction.
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Which cells act as the heart's pacemaker? Why are they the pacemaker cells?
answer
Cells of the SA node are the usual pacemaker, because they are autorhythmic cells and set the pace of the heart rate.
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In skeletal muscle cells, action potentials cause the release of calcium from the SR by directly opening SR voltage-gated calcium channels. What causes the release of calcium from the SR in cardiac muscle cells?
answer
Influx of extracellular calcium ions opens ryanodine receptors allowing Ca2+ to flow out of the SR.
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Calcium ions are removed from the sarcoplasm of the cardiac cell by the action of the sarcoplasmic reticulum (SR) Ca2+-ATPase pump and which other mechanism?
answer
sodium-calcium exchanger on the sarcolemma
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What are If channels responsible for in cardiac auto-rhythmic cells?
answer
the pacemaker potential
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Which of the following does NOT directly influence cardiac stroke volume?
answer
rate of pacemaker potentials
question
The action potential in a cardiac contractile cell causes
answer
opening of L-type calcium channels.
question
the term myogenic indicates that the heart muscle is the source of
answer
the electrical signal that triggers heart contraction.
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The flattening of the action potentials of myocardial contractile cells, called the plateau phase, is due to a combination of ________ K+ permeability and ________ Ca2+ permeability.
answer
decreasing, increasing
question
Myocardial cells can generate action potentials spontaneously because they have
answer
unstable ion channels
question
in order for blood to enter the heart
answer
the atria must not only be at rest but the atrial pressure must be lower than the veins.
question
The ________ is the amount of blood in a ventricle at the beginning of systole.
answer
end-diastolic volume
question
Which statement is NOT true regarding cardiac muscle?
answer
Cardiac muscle cells must obey the all-or-none law of contraction.
question
Which of the following conditions would have the greatest effect on peripheral resistance?
Which of the following conditions would have the greatest effect on peripheral resistance?
answer
doubling the diameter of a blood vessel
question
Left ventricular pressure is higher than pressure in the aorta during
answer
ventricular systole
question
Manganese ions block the calcium channels in the cardiac muscle membrane. How would the presence of manganese in the extracellular fluid affect the contraction of the heart muscle?
answer
The heart would beat less forcefully.
question
Sympathetic stimulation to the pacemaker cells ________ heart rate by ________ ion flow through ________ and ________ channels.
Sympathetic stimulation to the pacemaker cells ________ heart rate by ________ ion flow through ________ and ________ channels.
answer
increases, increasing, If , calcium
question
Acetylcholine is excitatory at the neuromuscular junction, but inhibitory at the SA node. Explain why this is true.
answer
Acetylcholine receptors in the heart muscle are muscarinic, wheras they are nicotinic in skeletal muscle. These receptors are linked to different types of ion channels. At the nicotinic receptor, the response is excitatory due to a influx of sodium, at the muscarinic, the reponse is inhibitory doe to the potassium efflux.
question
Explain how Ca2+ levels inside myocardial cells are important to cell function.
answer
in both autorhytmic and contractile myocardium, calcium plays an important role in the action potential. The action potentials in myocardial cells are similar in several ways to those of neurons and skeletal muscle, as the depolarization phase is due to sodium entry, re-polarization due to sodium exit, the main difference is myocardial cells have longer action potentials due to ca entry.
question
Which blood vessels allow blood to move directly from the arterial to the venous circulation?
answer
metarterioles
question
Which is the correct relationship between pressure, flow, and resistance?
answer
pressure= flow times resistance
question
Mean arterial pressure is equal to diastolic pressure plus one-third of the pulse pressure. An equivalent equation is MAP = 2/3 DBP + 1/3 SBP. Why is diastolic blood pressure (DBP) a larger component of MAP than systolic blood pressure (SBP)?
answer
the heart spends more time in distole than systole
question
What compensatory mechanisms are available to help maintain blood pressure when a large volume of blood is lost, such as during a hemorrhage?
answer
Vasoconstriction, increased thirst, and decreased renal fluid output in the urine
question
What effect would an increase in venous return have on mean arterial pressure?
answer
It would increase it by shifting blood from the veins into the arteries.
question
At rest, the majority of blood flows through the ________
answer
liver and digestive tract
question
If there were a sudden increase in blood volume, what would the baroreceptors do and what would be the effect of that reflex?
Why is the velocity of blood lowest in the capillaries as compared to all other types of vessels?
answer
The capillaries have the largest cross-sectional area.
question
Which of the following is occurring during systole?
answer
blood pressure increases and more stress is placed on arterial walls
question
The mean arterial pressure (MAP) is important because
answer
it represents the driving pressure for blood flow.
question
All of the following would cause an increase in blood pressure EXCEPT
answer
a decrease in cardiac output
question
The integrating center for neural control of blood pressure resides in the
answer
medulla oblongata
question
When blood pressure receptors sense a loss of blood pressure, they ________ their firing rate.
answer
decrease
question
If a person is bedridden for several days, the baroreceptor reflex may fail upon standing. Why?
answer
The kidneys have reduced the blood volume.
question
Mean arterial pressure is ________ proportional to cardiac output and ________ proportional to resistance of arterioles.
answer
directly, directly
question
Norepinephrine binding to alpha receptors on vascular smooth muscle causes ________ and epinephrine binding to alpha receptors on vascular smooth muscle causes ________.
answer
vasoconstriction, vasoconstriction
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