OS 202 B Samplex 2009 Flashcards
Which of the following is/are true of voltage gated potassium channels?
A. They display a high conductance in resting membrane
B. They open just before the peak of Na+ conductance in action potential
C. Their slow return to the closed state leads to after-depolarization
D. All of the above
B
Voltage-gated sodium ion channels
A. display a high conductance in resting membrane
B, are virtually closed when cell is at rest
C. pump 3 sodium ions out of the cell and 2 potassium ions inwards
D. are opened when the membrane is hyperpolarized
B
Temporal summation can occur with local potentials because
A. local potentials have a temporal course exactly corresponding to the duration of the stimulus
B. stimuli impinging on areas of the membrane near each other may result in a larger potential
C. unlike action potentials, local potentials are graded responses
D. local potentials remain localized in the region where the stimulus is applied
C
The trigger zone that integrates incoming signals from other cells and initiates the signal that the neuron sends to another neuron corresponds to the
A. cell body B. dendritic trunk C. dendritic spines D. axon hillock and initial segment E. axon trunk
D
Initiation of action potential is due to the opening of voltage-gated
A. Na+ channels
B, K+ channels
C. Cl– channels
D. Ca++ channels
B
Which if the following is true of action potential?
A. They can be summated temporally and spatially.
B. They can be in both depolarizing and hyperpolarizing directions.
C. Their magnitude depends on the magnitude of the stimulus.
D. None of the above
D
The following mechanisms contribute to the return of the membrane potential to its original resting value following an action potential:
A. rapid closure of open voltage – gated Na+ channel
B. opening of voltage sensitive K+ channels in the depolarized membrane
C. rapid influx of Cl– ions through voltage-gated channels
D. all of the above
E. only A and B
E
Because the voltage – gated potassium channels remain open during repolarization, the membrane
potential overshoots slightly beyond the previous resting level, making the membrane less excitable,
during the
A. absolute refractory period
B. relative refractory period
C. after – depolarization
D. after – hyperpolarization
D
Which of the following mechanisms account for the absolute refractory period?
A. opened state of all voltage – gated Na+ channels
B. efflux of potassium ion through voltage – gated K+ channels
C. closure of the activation gate of Na+ channels
D. all of the above
A
During after – hyperpolarization:
A. The membrane is more excitable
B. The potential is positive when measured with extracellular electrodes
C. There is cessation efflux of potassium ions
D. There is decreased oxygen consumption activity of the Na+ pump
B
During the supernormal period
A. continued efflux of K+ pushes the membrane potential nearer to potassium equilibrium potential
B. the membrane is hyperpolarized away from threshold
C. a larger stimulus is required to produce an action potential
D. the negative (depolarizing) after potential is subsiding
D
Acetylcholine is primarily removed from the synaptic cleft by the process of
A. reuptake into the presynaptic cell
B. diffusion into the interstitial compartment
C. enzymatic degradation
D. none of the above
C
Which factor is most crucial to the release of a neurotransmitter?
A. change in membrane potential
B. change in extracellular K+ concentration
C. change in extracellular Na+ concentration
D. change in extracellular Ca++ concentration
D
Which of the following is not a mechanical receptor?
A. Golgi tendon organ
B. vestibular hair cell
C. auditory hair cell
D. olfactory hair cell
D
Tetanus and botulinum toxins disrupts synaptic transmission by
A. disrupting the presynaptic membrane
B. inhibiting the VAMPs to dock
C. destroying the active zone
D. competitive inhibition at the postsynaptic receptor
B
Cerebral autoregulation is mainly controlled by
A. chemical-metabolic factors
B. pressure-controlled myogenic mechanisms
C. neurogenic factors
D. autonomic factors
B
All of the following can readily pass through the blood brain barrier to enter the central nervous system EXCEPT
A. caffeine B. ethanol C. mannitol D. nicotine E. oxygen
C
The statement that designates a chemical synapse include/s
A. The propagation of action potential across a chemical synapse is unidirectional.
B. There is direct ionic current flow from one cell to the next cell.
C. In a resting synapse, only the presynaptic membrane is normally polarized.
D. All of the above statements describe a chemical synapse
A
True of all sensory receptors:
A. The receptor potential produced by their stimulation directly brings about an all or none impulse discharge.
B. Stimulation produces depolarizing currents.
C. Stimulation brings about a change in conductance of an ion channel.
D. NOTA
C
Which statement is not true about perception?
A. They are direct records of the external environment.
B. They are constructed internally according to the capabilities of the nervous system.
C. They reflect the capacity of the brain to synthesize elementary sensations in a characteristic way.
D. They differ qualitatively from the physical qualities of stimuli.
A
The intensity of a stimulus may be altered by
A. changing the frequency of firing of a given receptor
B. recruiting more sensory units
C. contextual or environmental cues
D. any of the above
D
Which of the following statements demonstrate that sensory modality is encoded by a labeled line code?
A. Although light is the adequate stimulus for photoreceptors, a blow to the head can evoke a sense of light flash.
B. Electrical stimulation of some neurons in the right nucleus cuneatus evokes a sensation of touch
on the right upper extremity.
C. A deaf individual can still be made to hear some tones with direct stimulation of the auditory
nerve.
D. All of the above
D
Which of the following is not characteristic of a reflex action?
A. always involves transmission across at least one synapse
B. always occur with conscious perception
C. it can be modified by impulses from various parts of the central nervous system
D. may involve simultaneous excitation and inhibition of motor neurons
B
The inverse stretch reflex (is)
A. monosynaptic like the stretch reflex.
B. most sensitive to tension development of the muscle rather than its length.
C. requires the stimulation of the alpha motor neurons that innervate the agonist muscle from which the afferent fibers arise.
D. all of the above statements describe the inverse stretch reflex.
B
If you accidentally step on a pointed object, the following events occur in your spinal cord:
A. motor neurons to the ipsilateral extensors are excited while the motor neurons to the flexors are inhibited
B. motor neurons to the ipsilateral extensors and antagonist flexors are inhibited while at the same time those motor neurons innervating the contralateral flexors and antagonist extensors are stimulated
C. motor neurons to the ipsilateral flexors are excited while those innervating the antagonist
extensors are inhibited, at the same time, motor neurons innervating the contralateral extensors are excited while those innervating the antagonist flexors are inhibited
D. motor neurons to all extensors on both sides are excited while all flexors are inhibited so as to maintain good balance
C
It is advised to test the sensation of touch before testing for pain sensation so as to avoid _____ of touch receptors
A. sensory adaptation
B. sensitization
C. lateral inhibition
D. fatigue
B
A patient who sways on Rombergs much more with eyes closed most likely has a problem with his:
A. dorsal column
B. lateral lemniscus
C. vestibular apparatus
D. cochlear apparatus
A
