Question

23.  The separate effects of sympathetic and parasympathetic innervation of the pacemaker region of the heart can best be described as _______.

a) synergistic    b) complementary   c) cooperative    d) antagonistic   e) none of these

24.  A decrease in body temperature is sensed by the ________ which communicates with the       ________ of the brainstem to __________ output to the sympathetic nervous system.

      a) cerebral cortex; pons; increase      b) hypothalamus; cardiac center; decrease

      c) thalamus; basal nuclei; increase      d) hypothalamus; vasomotor center; increase

      e) basal nuclei; pons;decrease

29. When Robin kicks a soccer ball, her leg makes contact with the ball by _______ of the knee.  This is an example of a/an __________ contraction of the quadriceps.

       a)  flexion; concentric         b)  flexion; eccentric      c)  extension; eccentric

       d) extension; concentric      e)  flexion; isometric     

31.  The relaxation phase of a muscle twitch contraction coincides with

      a) calcium pumped back into the sarcoplasmic reticulum

      b) repolarization of the action potential   

      c) potassium voltage gates opening

      d) two of the above  

      e) all of the above

32.  Key differences between fast and slow muscle fibers include:

1. fast fibers always produces less force than slow fibers of the same diameter
2. slow fibers have more mitochondria than fast
3. fast fibers generally fatigue more easily than slow
4. two of the above
5. all of the above

33.  Which of the following circumstances would cause a muscle fiber to produce lactic acid?

      a) activity which requires recruitment of oxidative (slow) motor units and fibers

      b) activity which requires recruitment of glycolytic (fast) motor units and fibers

      c) both activities would yield the same amount of lactate

      d) neither activity would yield any lactate

34.  The smallest amount of muscle tissue that can be activated to produce force would be

      a) a single motor unit       

      b) a single muscle fiber

      c) all muscle fibers activated at the lowest frequency of stimulation

      d) a whole muscle    

      e) none of the above

35. Which of these statements is correct regarding skeletal muscle contraction?

a)  all motor units are activated simultaneously.

b)  muscle contraction continues for long periods after nervous stimulation ceases.

c)  the crossbridges bind to the actin and shorten the sarcomeres.

d)  tropomyosin binds calcium so that troponin can expose G actin binding sites.

e)  all of the above are correct

Answer 1

23. (d). anatagonist- Sympathetic division of ANS acts as stimulatory on heart increasing heart rate, cardiac output while parasympathetic has inhibitory effects this both are opposing therefore anatagonist to each other .

24.(d). hypothalamus, vasomotor centre, increase

When the body temperature becomes low, it is activated by hypothalamus which causes vasomotor centre to cause vasoconstriction as by increasing sympathetic activity and leading to decrease blood flow to the skin retaining heat.

29. (b). flexion, eccentric

When the player kicks the soccer ball, in the entire process there is flexion of the knee. There is lengthening of the anterior muscle quadriceps therefore called eccentric contraction.

31. (e). all of these

During relaxation it is started when calcium is pumped back to the sarcoplasmic reticulum leading to opposite of the action potential that is repolarization of action potential. The K gated channels are open for the K to efflux resulting in all the events of relaxation.

32. (e). all of the above

Slow twitch fibres have more number of mitochondria allowing them to carry out aerobic respiration at high rate and have more myoglobin and this these features allow them to sustain for long period of time without fatigue. Therefore, fast twitch fibres with less mitochondria and using anerobic mode fatigue quicker and can be used for shorter duration work.

33. (b). activity which requires recruitment of glyocolytic (fast) motor units and fibres

In the glyocolytic (fast) motor fibres, there is use of anaerobic pathway thus excess glucose is converted to lactic acid.

34. (c). All muscle fibres activated at the lowest frequency of stimulation

Without reaching the threshold, there cannot be initiation of muscle activity. Therefore all muscle fibres when reaching the threshold value will start an activity.

35. (c). crossbridges binds to actin and shorten the sarcomere

To prevent muscle fatigue, some motor units are rest and some active to allow for longer muscle contraction.

When the stimulation of the motor neuron providing the impulse to the muscle fibers stops, the chemical reaction that causes the rearrangement of the muscle fibers' proteins is stopped. This reverses the chemical processes in the muscle fibers and the muscle relaxes.

Troponin binds to calcium, not tropomyosin to expose the myosin binding site on actin.