Block 5 Neurophysiotherapy BRS W Expl Part 2
- 1.
Muscle stretch leads to a direct increase in firing rate of which type of nerve?
- A.
A-Motoneurons
- B.
Y-Motoneurons
- C.
Group Ia fibers
- D.
Group lb fibers
Correct Answer
C. Group Ia fibersExplanation
Group Ia afferent fibers innervate intrafusal fibers of the muscle spindle. When the intrafusal fibers are stretched, the group Ia fibers fire and activate the stretch reflex, which causes the muscle to return to its resting length.Rate this question:
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- 2.
Which of the following is a characteristic of nuclear bag fibers?
- A.
They are one type of extrafusal muscle fiber
- B.
They detect dynamic changes in muscle length
- C.
They give rise to group lb afferents
- D.
They are innervated by a-motoneurons
Correct Answer
D. They are innervated by a-motoneuronsExplanation
Nuclear bag fibers are one type of intrafusal muscle fiberthat make up muscle spindles. They detect dynamic changes in muscle length, give rise to group Ia afferent fibers, and are innervated by 'y-motoneurons. The other type of intrafusal fiber, the nuclear chain fiber, detects static changes in muscle length.Rate this question:
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- 3.
Which reflex is responsible for polysynaptic excitation of contralateral extensors?
- A.
Stretch reflex (myotatic)
- B.
Golgi tendon reflex (inverse myotatic)
- C.
Flexor withdrawal reflex
- D.
Subliminal occlusion reflex
Correct Answer
C. Flexor withdrawal reflexExplanation
Flexor withdrawal is a polysynaptic reflex that is used when a person touches a hot stove or steps on a tack. On the ipsilateral side of the painful stimulus, there is flexion (withdrawal); on the contralateral side, there is extension to maintain balance.Rate this question:
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- 4.
Cutting which structure causes blindness in the temporal fields of the left and right eyes?
- A.
Optic nerve
- B.
Optic chiasm
- C.
Optic tract
- D.
Geniculocalcarine tract
Correct Answer
B. Optic chiasmExplanation
Optic nerve fibers from both temporal receptor fields cross at the optic chiasm.Rate this question:
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- 5.
Which of the following structures has a primary function to coordinate rate, range, force, and direction of movement?
- A.
Primary motor cortex
- B.
Premotor cortex and supplementary motor cortex
- C.
Prefrontal cortex
- D.
Basal ganglia
- E.
Cerebellum
Correct Answer
E. CerebellumExplanation
Output of Purkinje cells from the cerebellar cortex to deep cerebellar nuclei is inhibitory. This output modulates movement and is responsible for the coordination that allows one to "catch a fly."Rate this question:
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- 6.
Sensory receptor potentials
- A.
Are action potentials
- B.
Always bring the membrane potential of a receptor cell toward threshold
- C.
Always bring the membrane potential of a receptor cell away from threshold
- D.
Are graded in size, depending on stimulus intensity
- E.
Are all-or-none
Correct Answer
D. Are graded in size, depending on stimulus intensityExplanation
Receptor potentials are graded potentials that may bring the membrane potential of the receptor cell either toward (depolarizing) or away from (hyperpolarizing) threshold. Receptor potentials are not action potentials, although action potentials (which are all-or-none) may result if the membrane potential reaches thresholdRate this question:
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- 7.
Complete transection of the spinal cord at the level of T1 would most likely result in
- A.
Temporary loss of stretch reflexes belowthe lesion
- B.
Temporary loss of conscious proprioception below the lesion
- C.
Permanent loss of voluntary control of movement above the lesion
- D.
Permanent loss of consciousness above the Lesion
Correct Answer
A. Temporary loss of stretch reflexes belowthe lesionExplanation
Transection of the spinal cord causes "spinal shock" and loss of all reflexes below the level of the lesion. These reflexes, which are local circuits within the spinal cord, will return with time or become hypersensitive. Proprioception is permanently (rather than temporarily) lost because of the interruption of sensory nerve fibers. Fibers above the lesion are intact.Rate this question:
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- 8.
The inability to perform rapidly alternating movements (dysdiadochokinesia) is associated with lesions of the
- A.
Premotor cortex
- B.
Motor cortex
- C.
Cerebellum
- D.
Substantia nigra
- E.
Medulla
Correct Answer
C. CerebellumExplanation
Coordination of movement (synergy) is the function of the cerebellum. Lesions of the cerebellum cause ataxia, lack of coordination, poor execution of movement, delay in initiation of movement, and inability to perform rapidly alternating movements. The premotor and motor cortices plan and execute movements. Lesions of the substantia nigra, a component of the basal ganglia, result in tremors, lead-pipe rigidity, and poor muscle tone (Parkinson's disease).Rate this question:
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- 9.
Which autonomic receptor is activated by low concentrations of epinephrine released from the adrenal medulla and causes vasodilation?
- A.
Adrenergic a receptors
- B.
Adrenergic pi receptors
- C.
Adrenergic p, receptors
- D.
Cholinergic muscarinic receptors
- E.
Cholinergic nicotinic receptors
Correct Answer
C. Adrenergic p, receptorsExplanation
B2 Receptors on vascular smooth muscle produce vasodilation. a Receptors on vascular smooth muscle produce vasoconstriction. Because 02 receptors are more sensitive to epinephrine than are a receptors, low doses of epinephrine produce vasodilation, and high doses produce vasoconstriction.Rate this question:
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- 10.
A lesion of the chorda tympani nerve would most likely result in
- A.
Impaired olfactory function
- B.
Impaired vestibular function
- C.
Impaired auditory function
- D.
Impaired taste function
- E.
Nerve deafness
Correct Answer
D. Impaired taste functionExplanation
The chorda tympani [cranial nerve (CN) VII] is involved in taste; it innervates the anterior two-thirds of the tongue.Rate this question:
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- 11.
Which of the following would produce maximum excitation of the hair cells in the right horizontal semicircular canal?
- A.
Hyperpolarization of the hair cells
- B.
Bending the stereocilia away from the kinocilia
- C.
Rapid ascent in an elevator
- D.
Rotating the head to the right
Correct Answer
D. Rotating the head to the rightExplanation
The semicircular canals are involved in angular acceleration or rotation. Hair cells of the right semicircular canal are excited (depolarized) when there is rotation to the right. This rotation causes bending of the tereocilia toward the kinocilia, and this bending produces depolarization of the hair cell. Ascent in an elevator would activate the saccules, which detect linear acceleration.Rate this question:
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- 12.
Pathogens that produce fever cause
- A.
Decreased production of interleukin-1 (IL-1)
- B.
Decreased set-point temperature in the hypothalamus
- C.
Shivering
- D.
Vasodilation of blood vessels in the skin
Correct Answer
C. ShiveringExplanation
Pathogens release interleukin-1 (IL-1) from phagocytic cells. IL- 1 then acts to increase the production of prostaglandins, ultimately raising the temperature set point in the anterior hypothalamus. The hypothalamus now "thinks" that the body temperature is too low (because the core temperature is lower than the new set-point temperature) and initiates mechanisms for generating heat—shivering, vasoconstriction, and shunting of blood away from the venous plexus near the skin surface.Rate this question:
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- 13.
Which of the following statements about the olfactory system is true?
- A.
The receptor cells are neurons
- B.
The receptor cells are sloughed off and are not replaced
- C.
Axons of cranial nerve (CN) I are A-delta fibers
- D.
Axons from receptor cells synapse in the prepiriform cortex
- E.
Fractures of the cribriform plate can cause inability to detect ammonia
Correct Answer
A. The receptor cells are neuronsExplanation
Cranial nerve (CN) I innervates the olfactory epithelium. Its axons are C fibers. Fracture of the cribriform plate can tear the delicate olfactory nerves and thereby eliminate the sense of smell (anosmia); however, the ability to detect ammonia is left intact. Olfactory receptor cells are unique in that they are true neurons that are continuously replaced
from undifferentiated stem cells.Rate this question:
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- 14.
Which of the following is a step in photoreception in the rods?
- A.
Light converts all-trans retinal to 11-cisretinal
- B.
Metarhodopsin II activates transducin
- C.
Cyclic guanosine monophosphate (cGMP) levels increase
- D.
Rods depolarize
- E.
Release of neurotransmitter increases
Correct Answer
B. Metarhodopsin II activates transducinExplanation
Photoreception involves the following steps. Light converts 11-cis retinal to all-trans retinal, which is converted to such intermediates as metarhodopsin II. Metarhodopsin II activates a stimulatory G protein (transducin), which activates a phosphodiesterase. Phosphodiesterase breaks down cyclic guanosine monophosphate (cGMP), so intracellular
cGMP levels decrease, causing closure of Na + channels in the photoreceptor cell membrane and hyperpolarization. Hyperpolarization of the photoreceptor cell membrane inhibits the release of neurotransmitter. If the neurotransmitter is excitatory, then the bipolar cell will be hyperpolarized (inhibited). If the neurotransmitter is inhibitory, then the bipolar cell will be depolarized (excited).Rate this question:
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- 15.
Which of the following autonomic drugs acts by stimulating adenylate cyclase?
- A.
Atropine
- B.
Clonidine
- C.
Curare
- D.
Norepinephrine
- E.
Phentolamine
- F.
Phenylephrine
- G.
Propranolol
Correct Answer
D. NorepinephrineExplanation
Among the autonomic drugs, only B1 and B2 adrenergic agonists act by stimulating adenylate cyclase. Norepinephrine is a B1 agonist. Atropine is a muscarinic cholinergic antagonist. Clonidine is an a2 adrenergic agonist. Curare is a nicotinic cholinergic antagonist. Phentolamine is an al adrenergic antagonist. Phenylephrine is an al adrenergic agonist. Propranolol is a B1 and B2 adrenergic antagonist.Rate this question:
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- 16.
Aballet dancer spins to the left. During the spin, her eyes snap quickly to the left. This fast eye movement is
- A.
Nystagmus
- B.
Post-rotatory nystagmus
- C.
Ataxia
- D.
Aphasia
Correct Answer
A. NystagmusExplanation
The fast eye movement that occurs during a spin is nystagmus. It occurs in the same direction as the rotation. After the spin, post-rotatory nystagmus occurs in the opposite direction.Rate this question:
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- 17.
Which of the following has a much lower concentration in the cerebrospinal fluid (CSF) than in cerebral capillary blood?
- A.
Na+
- B.
K+
- C.
Osmolarity
- D.
Protein
- E.
Mg2+
Correct Answer
D. ProteinExplanation
Cerebrospinal fluid (CSF) is similar in composition to the interstitial fluid of the brain. Therefore, it is similar to an ultrafiltrate of plasma and has a very low protein concentration because large protein molecules cannot cross the blood–brain barrier. There are other differences in composition between CSF and blood that are created by transporters in the choroid plexus, but the low protein concentration of CSF is the most dramatic difference.Rate this question:
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Mar 21, 2023Quiz Edited by
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