851. Factors affecting the activity of the vasomotor area in the medulla are
A. Inhibitory inputs from carotid and aortic chemoreceptors
B. Direct stimulation by C02
C. Excitatory inputs from the carotid, aortic and cardiopulmonary baroreceptors
D. Excitatory input from lungs
E. Inhibitory input from cortex via hypothalamus
852. Regarding cardiovascular regulatory mechanisms, all of the following are true except
A. Decreases in oxygen tensions and increases in local carbon dioxide concentration lead to coronary arterial dilatation
B. Circulating vasoconstrictor hormones include angiotensin II and aldosterone
C. Vasomotor control is mediated by baroreceptor reflexes
D. Increased baroreceptor activation slows down heart rate
E. The vasomotor area is stimulated by hypoxia and PC02
853. Poiseuille’s Equation states
A. Flow is proportional to density
B. Viscosity multiplied by flow is proportional to the pressure gradient
C. Flow is inversely proportional to the radius 4
D. Flow is not related to the length of the tube
E. Flow is proportional to the radius
854. Which of the following is an example of monosynaptic reflex?
A. Stretch reflex
B. Withdrawal reflex
C. Abdominal reflex
D. Baroreceptor reflex
E. All of the above
855. Which of the following statements regarding muscle spindle is FALSE?
A. It contains nuclear bag & nuclear chain fibers, which are responsible for dynamic & static responses respectively.
B. It is important as a feedback sensor to give information about muscle length
C. It has no contractile elements at all
D. Increased Ay motor efferent discharge to muscle spindle will lead to increased muscle spindle sensitivity to stretch.
E. Muscle spindle afferent does not fire if the muscle is actively contracted as extrafusal fiber shortened without intrafusal fiber being shortened.
856. Duration of knee jerk reflex response is in the order of:
A. 10ms
B. 20ms
C. 30ms
D. 40ms
E. 50ms
857. Increased muscle spindle sensitivity to stretch secondary to increased Ay efferent discharge can occur with:
A. Anxiety
B. Hypertonia
C. Skin stimulation on the ipsilateral skin
D. Jendrassiks maneuver
E. All of the above
858. Which of the following statement regarding withdrawal reflex is INCORRECT?
A. It is characterized by flexion of the ipsilateral limb & extension of the contralateral limb when strong noxious stimuli are applied to the skin.
B. Flexing pattern is constant despite the site of stimuli varying in the limb.
C. Withdrawal reflex is prepotent& excludes other reflex activity from taking place.
D. Increased strength of stimuli will increase the number of motor units being recruited & increase the duration of response.
E. Supramaximal stimulation of sensory nerve of a limb never produces as strong a contraction in flexural muscle as elicited by direct electrical stimulation of the muscle itself.
859. Which of the following statements regarding sensory nervous system is INCORRECT?
A. 10 sensory nerve fibers for fine touch & proprioception travels up the ipsilateral dorsal column of spinal cord to reach the medulla
B. 10 sensory nerve fibers for temperature & pain travel up the ipsilateral antero-lateral column of spinal cord to reach the thalamus.
C. Fibers in the dorsal column do not decussate in spinal cord
D. Antero-lateral column also give sensory input to the reticular formation
E. Impulses from sensory nuclei in the substantia gelatinosa are modified by the impulses from descending tracts from the brain & collateral fibers.
860. Which of the following statement regarding sensory fiber arrangement in the spinal cord is CORRECT?
A. In the ventral spino-thalamic tract, cervical sensory fibers are arranged closer to the midline than the sacral fibers
B. In the dorsal column, sacral sensory fibers are arranged closer to the midline than the cervical fibers
C. In the lateral spino-thalamic tract, cervical sensory fibers are arranged closer to the midline than the sacral fibers
D. All of the above
E. None of the above