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Biology bradycardia

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					BIOLOGY 131                                 NAME:____KEY_________
SPRING 2009
EXAM #2
100 POINTS                                  I would like to dedicate this exam to:
                                            _______________________________


INSTRUCTIONS:

1.    Use Scan-Tron Form 882 for all multiple-choice questions and true-false
      questions.
2.    A #2 pencil MUST be used.
3.    Erasures MUST be complete.
4.    Choose the BEST answer to each question.
5.    You may write on the exam itself, but please do not make any extraneous marks
      on the answer sheet (Scan-Tron form).
6.    Answer short answer questions directly on the exam in the space provided
      CLEARLY AND LEGIBLY.
7.    If you include a diagram or figure in your explanation, it must be clearly
      labeled.
8.    Make sure you carefully answer ALL portions of the question.
9.    Multiple choice and true-false questions are worth 2 points each; short answer
      questions are labeled with appropriate points.
10.   In the event you think a question is ambiguous, you may explain your reasoning
      below. Make certain you include your Scan-Tron answer in your explanation.
      Limit yourself to 3 questions. Your explanation will not be considered unless
      you are a borderline case at the end of the course.


QUESTION #:___           _______________________________________________
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QUESTION #:___           _______________________________________________
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QUESTION #:___           _______________________________________________
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1. A synapse at the neuromuscular junction…
   A. may result in either an EPSP or an IPSP
   B. always results in the successful transmission of the action potential onto the muscle membrane.
   C. Causes an end plate potential that is generally smaller in magnitude when compared to a neuronal
       synapse.
   D. Results in the release of epinephrine for binding to the end-plate receptors.
   E. Both A and B are correct.

The following three questions relate to this scenario: Larry can normally lift 35 lbs (max) with his right arm.
Stella can normally lift 25 lbs (max) with her right arm. Assume each has 20 motor units per arm.

2. If both Stella and Larry lift 15 lbs…
   A. the number of motor units recruited will be the same for each
   B. an EMG from Larry’s arm would show greater amplitude than an EMG from Stella’s arm
   C. Larry would experience asynchronous recruitment, but Stella would not
   D. Stella would recruit more motor units than would Larry
   E. None of these are correct.

3. If both Stella and Larry lift their own maximal weight….
   A. they would each recruit the same number of motor units
   B. an EMG from Larry’s arm would show greater amplitude than an EMG from Stella’s arm
   C. they would each experience asynchronous recruitment
   D. Both A and C are correct.
   E. All of the above are correct.

4. You can assume, from what is described, that Larry….
   A. has a greater percentage of slow-twitch muscles than does Stella
   B. has more actin and myosin within his muscle cells compared to Stella
   C. can have asynchronous recruitment at a heavier weight than Stella can
   D. Both B and C are correct.

5.   Optimal length in muscle is “optimal” because…
     A. there are more motor units recruited in contractions that begin at optimal length
     B. contracting at optimal length results in more calcium release from the sarcoplasmic reticulum
     C. beginning a contraction at optimal length allows more calcium to bind to troponin
     D. a contraction at optimal length causes more sodium entry at the neuromuscular junction
     E. prior to the contraction, there is optimal positioning of the myosin relative to the actin

6. You should find more motor units in muscles used for fine movements (e.g. fingers)
   A. True            B. False         *More of them, as they're smaller in size (fewer fibers per unit)

7. An increase in sympathetic nervous system activity may
   A. cause stronger contractions in cardiac muscle fibers
   B. cause stronger contractions in skeletal muscle fibers
   C. cause stronger contractions in smooth muscle fibers.
   D. A and C are correct.
   E. B and C are correct.

8. The ventricle fills only when the pressure in the ventricle exceeds the pressure in the atrium.
    A. True               B. False
9. Isovolumetric relaxation occurs
    A. just before the first heart sound           B. just after the first heart sound
    C. just before the second heart sound          D. just after the second heart sound

10. Digitalis increases intracellular calcium levels in cardiac muscle cells. Thus,
    A. digitalis would increase stroke volume
    B. digitalis would reduce end-systolic volume
    C. digitalis would not affect end-diastolic volume
    D. Two of these are correct.
    E. All of these are correct.

11. Which of the following is consistent with an increase in parasympathetic activity?
   A. increased sodium entry through If (“funny”) channels in the SA node
   B. increased EDV
   C. increased contractility
   D. increased TPR

12. If the stomach needs more blood, the radius of the arterioles leading into the stomach area should
    _________________, and their resistance should ______________________.
   A. Increase; decrease     B. increase; increase
   C. decrease; increase     D. decrease; decrease

13. Tanner’s heart rate is 65 beats/min and his cardiac output is 5.2 L/min. He puts on a cape (like a super hero)
and begins skipping down the sidewalk, causing his heart rate to increase to 120 beats/min, while his cardiac
output reaches 15 L/min. What is Tanner’s stroke volume before and after skipping?
    A. 70 ml; 100 ml      B. 80 ml; 125 ml      C. 125 ml; 140 ml      D. 65 ml; 120 ml E. 80 ml; 120 ml

14. Which of these would cause edema?
    A. increased plasma proteins                   B. increased number of lymphatics in the tissue space
    C. reduced capillary blood pressure            D. proteins in the interstitial space
    E. Two of these are correct.

15. If you drop epinephrine on the frog heart, it should exhibit an increased ESV.
    A. True             B. False

16. A stenotic aortic semilunar valve would cause:
    A. increased stroke volume          B. higher-than-normal pressure in the pulmonary artery
    C. increased MAP                    D. increased ESV                E. bradycardia

17. At the exact moment when a person rises quickly from a reclined position (assume they feel a bit lightheaded),
    A. the carotid baroreceptors are stretched more
    B. venous return is higher than normal
    C. the cardiovascular control center will reflexively induce bradycardia
    D. More than one of the above are correct.
    E. None of the above are correct.

18. Blood flow to a tissue will increase if the ___________________.
    A. level of carbon dioxide at the tissue increases
    B. tissue is cold
    C. arterioles leading to the tissue bed reduce their diameter
    D. veins leading away from the tissue bed are dilated
19. Based on its high oxygen requirement, one would expect cardiac muscle to have
    A. many mitochondria
    B. relatively few capillaries
    C. a relatively high concentration of glycolytic enzymes
    D. a color that is similar to fast twitch muscle
    E. Both A and C are correct.

20. During which phase of the cardiac cycle does aortic pressure exceed ventricular pressure?
    A. ejection                         B. all phases except ejection
    C. isovolumetric contraction        D. ventricular filling           E. Both C and D are correct.

21. Electrical activity is passing through the AV node
    A. during the P wave
    B. between the P wave and the QRS complex
    C. between the QRS complex and the T wave
    D. during the T wave
    E. just after ventricular contraction

22. A diuretic is helpful to someone with fluid in the lungs because…
    A. it increases capillary blood pressure, thus increasing capillary filtration
    B. it increases the number of plasma proteins, thus increasing reabsorption
    C. it increases capillary reabsorption relative to filtration
    D. it vasoconstricts arterioles, thus reducing capillary filtration

23. In a patient with left ventricular failure and normal blood pressure, one would expect to find….
    A. Normal heart rate           B. Increased heart rate                  C. Decreased heart rate

24. In a normal, healthy person, the average blood pressure in the pulmonary circulation equals the average
blood pressure in the systemic circulation.
    A. True                       B. False

25. As a result of a fall in arterial blood pressure, one would expect increased….
    A. acetylcholine release        B. renin         C. baroreceptor firing D. Both B and C are correct.


For Questions 26-30, choose which is greater (A or B) and indicate that choice on your scantron.


26. A. blood pressure in the arterioles            B. blood pressure in the arteries

27. A. arteriole diameter normally                 B. arteriole diameter with histamine release

28. A. aortic pressure when semilunar valve shuts          B. left ventricle pressure when semilunar valve shuts

29. A. level of intracellular Ca2+ in a skeletal muscle twitch
    B. level of intracellular Ca2+ in a cardiac muscle twitch

30. A. resting HR in 75 degree heat                B. resting HR in 105 degree heat
SHORT ANSWER QUESTIONS

1. (8 pts) A. What happens to diastolic pressure during exercise? Explain.
           B. How is this effect different from the changes expected in a non-exercise fight-or-flight response?

During exercise, diastolic pressure either stays the same or decreases. Because there is so much
vasodilation in skeletal muscle (due to both sympathetic nervous system activity AND local metabolite
build-up), this drops the overall vascular resistance (TPR). This affects diastolic pressure specifically,
lowering it.

This is different from a non-exercise situation because of the local factors (metabolites). In a non-
exercise state, the only vasodilation to skeletal muscle arterioles is via the sympathetic ("body-wide")
actions - there isn't a local influence. In exercise, the local metabolites cause vasodilation above and
beyond what the sympathetic nervous system does, causing a much larger overall drop in resistance.




2. (15 pts) The figure below represents Chuck’s pressure/volume loop at rest. On the figure, indicate the
changes that would occur if Chuck went for a moderate bike ride (sustained max HR = 135 bpm). Below the
figure, explain exactly how these changes occur (you must accurately describe each mechanism involved)




Graph should extend a bit to the right on filling (increased venous return, with a moderate increase in
HR, so overall filling might be slightly larger). If explained correctly, no change in filling or even a
slight decrease in filling (if HR is assumed to be high enough to limit filling) are acceptable. In every
case, the increase in venous return must be acknowledged.

Ejection should be at higher pressure, and graph should extend more to the left, indicating a lower
ESV. This is because the increase in contractility (due to increased Ca2+) results in less blood being left
in the heart.
3. (3 pts each) These should be brief, but precise answers! Mechanisms (where appropriate) must be explained!!

        A. Why do veins have valves?

        To maintain one-way flow


        B. What is a typical symptom for a patient with a stenotic mitral (bicuspid) valve?


        dyspnea (difficulty breathing)

        C. How would vasoconstriction of arterioles affect filtration in the associated capillary bed?

        it would reduce filtration, because capillary blood pressure would be lower



        D. In skeletal muscle, WHY does tetany produce greater tension than a muscle twitch?


        because there is more intracellular calcium present during tetany




4. (8 pts) A patient in the hospital is diagnosed with aortic semilunar valve stenosis.

        A. In the space below, draw the appropriate pressure tracings (from cardiac catheterization) that
        would show this problem. Make sure that you label your figure correctly, and explain exactly why
        your picture indicates aortic semilunar valve stenosis.


        YOU DID NOT HAVE THIS LAB, SO WOULD NOT SEE THIS TYPE OF QUESTION




        B. Your patient initially presented with symptoms similar to congestive heart failure. Name at least
        two effects (symptoms or measurable variables) that are common to both congestive heart failure and
        semilunar valve stenosis, and explain why they occur with each condition.



        THIS PART YOU CAN ANSWER: In both cases, the ventricle is not emptying to the degree that
        it should. This could cause (among other things) an increased ESV, back-up of blood into the lungs
        causing dyspnea, reduced cardiac output, causing the HR to increase to balance blood pressure,
        skin that is pale/cold due to reduced blood flow, etc.
5. (10 pts) Atropine is an anticholinergic drug that binds to and blocks muscarinic receptors. It is commonly used
by paramedics to treat bradycardia in emergency situations.

            Why could bradycardia be a life-threatening condition?

                 If HR is too low, it can reduce blood pressure, causing shock



            How would an anticholinergic drug like atropine alleviate the bradycardia?


                 By blocking Ach binding at the SA node, HR will automatically increase


            In heart transplant patients, atropine is ineffective and dopamine, a catecholamine, must be
            administered intravenously instead. Why? You must fully explain both why atropine is ineffective
            and why dopamine works to receive full credit. [Hint: remember that only the primary vessels are
            reconnected in a heart transplant]

                 In a heart transplant, the nerves are severed, but the vasculature is still intact; thus, the
                 only effective treatment would be using something that arrives via the blood, not via a
                 nerve ending. Dopamine, like Epi and NE, can travel through the blood (they are
                 hormones as well as neurotransmitters). Ach is only a neurotransmitter, and thus wouldn't
                 be having an effect in the first place, so blocking it would do no good.




6. (12 pts) A man who was stabbed during a fight is being cared for by paramedics. He has the following
 vital signs: BP 110/55; HR 135 bpm; resp. rate 22 breaths/min (normal 16-18); skin pale and cool.

        A. He has lost quite a bit of blood, yet his blood pressure is within the normal range. Explain.
        If he's lost blood, his stroke volume is reduced, but he can still increase HR to maintain BP.
        Since BP is a regulated variable, all other variables will change to make sure it stays constant.


        B. Why is his skin pale and cool?
        His stroke volume is reduced because he's lost blood; thus the blood he does have is being
        routed to the most vital organs. Skin is not "vital", so it has less blood flow, making it both
        pale and cold

        C. What effects will the kidney have on this situation? Explain in detail.

        The kidney will attempt to limit further volume loss by reducing urine formation. It will also
        release renin in response to the initial drop in BP, and this will result in the formation of
        Angiotensin II, which makes him thirsty (so he'll take in water to replace lost volume), causes
        vasoconstriction (to keep BP up), and helps the kidney retain volume. The kidney will also
        release EPO to begin the process of making new red blood cells to replace what he lost (this
        takes time, so not immediate)

				
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