All Questions: 451-480
451. In the mammalian suprachiasmatic nucleus, the proteins CLOCK and BMAL1 bind together and promote the expression of which two genes central to the circadian negative-feedback loop?
- A. Per and Cry
- B. Tim and Dbt
- C. Clock and Bmal1
- D. Rev-erb and Ror
Show Answer
Correct answer: A
CLOCK and BMAL1 work together to turn on the Per and Cry genes. As PER and CRY proteins build up, they feed back and shut down CLOCK–BMAL1 activity, creating the daily on–off cycle that drives circadian rhythms in the suprachiasmatic nucleus.
452. Which term below refers to a collection of specialized midline brain structures that lack a normal blood–brain barrier in order to enable bidirectional communication between the brain and the blood?
- A. basal ganglia
- B. limbic system
- C. reticular formation
- D. circumventricular organs
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Correct answer: D
The circumventricular organs are a group of structures lacking a blood-brain barrier that are centered around the ventricles of the brain. These structures are thought to be lacking a blood-brain barrier because their functions require access to the bloodstream.
453. Which pathway within the anterolateral system terminates in the periaqueductal gray and is thought to play a role in pain inhibition?
- A. spinothalamic tract
- B. spinoreticular tract
- C. spinomesencephalic tract
- D. dorsal columns-medial lemniscus pathway
Show Answer
Correct answer: C
The spinomesencephalic tract plays an important role in the control and inhibition of pain. Fibers in the spinomesencephalic tract follow the same path as the spinothalamic tract but they synapse in an area of the midbrain called the periaqueductal gray.
454. Beta-endorphin is a peptide neurotransmitter whose best-understood role involves:
- A. pain inhibition
- B. memory consolidation
- C. fight-or-flight responses
- D. regulating circadian rhythms
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Correct answer: A
Beta-endorphin is a peptide neurotransmitter and hormone found in the central and peripheral nervous systems. It is best known for its role in pain inhibition. By binding to opioid receptors, beta-endorphin can elicit natural pain-relieving effects that have been found to be more potent than morphine.
455. How many different types of cone cells are required for typical human color vision?
- A. 1
- B. 2
- C. 3
- D. 4
Show Answer
Correct answer: C
Normal color vision relies on three types of cones—each sensitive to different ranges of wavelengths corresponding roughly to blue, green, and red.
456. Marcus is hit in the forehead with a baseball and immediately feels sharp pain in that area. Which division of the trigeminal nerve carries this sensory information?
- A. ophthalmic division (V1)
- B. maxillary division (V2)
- C. mandibular division (V3)
- D. none of the above; it would be carried by the facial nerve
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Correct answer: A
The trigeminal nerve is the main sensory nerve of the head. It has three divisions, the ophthalmic, maxillary, and mandibular divisions, which supply three different regions of the head and face. The forehead is supplied by the ophthalmic division of the trigeminal nerve.
457. A person experiences damage to Wernicke’s area. Which of the following deficits is most likely to occur?
- A. loss of vision in the right visual field
- B. fluent but nonsensical speech along with poor language comprehension
- C. inability to form new long-term memories
- D. difficulty producing fluent speech despite normal language comprehension
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Correct answer: B
Damage to this Wernicke's area often results in a condition called Wernicke's aphasia, where patients are able to produce speech that resembles fluent language but actually is meaningless. Patients with Wernicke’s aphasia also typically suffer from a deficiency in their ability to understand language.
458. Parasympathetic preganglionic neurons release acetylcholine. What is the primary neurotransmitter released by parasympathetic postganglionic neurons?
- A. acetylcholine
- B. serotonin
- C. norepinephrine
- D. dopamine
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Correct answer: A
Parasympathetic postganglionic neurons primarily release acetylcholine. This neurotransmitter binds to muscarinic receptors on target organs, producing effects like slowing the heart rate, stimulating digestion, etc.
459. Which of the following touch receptors have the largest receptive fields, making them well-suited to detect vibrations objects cause when they are contacted or grasped by the hand?
- A. Merkel's discs
- B. Meissner's corpuscles
- C. Pacinian corpuscles
- D. Ruffini's endings
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Correct answer: C
Pacinian corpuscles are rapidly-adapting receptors with very large receptive fields. They are thought to be most effective at transmitting information about vibrations objects cause when they are contacted or grasped by the hand. This information may be important for the use of tools.
460. What is the name for the extension of the meninges that extends from the end of the spinal cord to the tailbone and helps anchor the cord in place?
- A. cauda equina
- B. filum terminale
- C. dorsal root ganglion
- D. conus medullaris
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Correct answer: B
An extension of the meninges called the filum terminale extends from the end of the spinal cord to the tailbone to anchor the cord in place.
461. At around the fourth week of neural development, the neural tube expands into three bulges known as the:
- A. primary vesicles
- B. ventricles
- C. neural crests
- D. meninges
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Correct answer: A
As the neural tube closes, bulges begin to appear and they gradually become more noticeable. During the fourth week, there are three of these bulges present. They are called the primary vesicles. They are the prosencephalon, the mesencephalon, and the rhombencephalon.
462. Which of the following is the primary mechanism by which dopamine is cleared from the synaptic cleft?
- A. enzymatic breakdown by acetylcholinesterase in the synaptic cleft
- B. diffusion into the postsynaptic neuron through dopamine receptors
- C. storage inside synaptic vesicles in the postsynaptic neuron
- D. reuptake into the presynaptic neuron by dopamine transporters
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Correct answer: D
Dopamine is primarily removed from the synaptic cleft by a transporter protein called the dopamine transporter. Dopamine is taken back up into the presynaptic neuron and typically either repackaged into vesicles or broken down by the enzyme monoamine oxidase (MAO).
463. Which tract carries visual information from the lateral geniculate nucleus of the thalamus to the primary visual cortex?
- A. optic nerve
- B. optic tract
- C. optic radiation
- D. optic chiasm
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Correct answer: C
Most of the visual information that leaves the retina is sent to a nucleus in the thalamus called the lateral geniculate nucleus. From there it is sent back to the primary visual cortex via large bundles of axons called the optic radiations.
464. Which of the following best describes the defining difference between a transient ischemic attack (TIA), also known as a "mini-stroke," and a stroke?
- A. a TIA causes mild symptoms, while a stroke causes more severe symptoms
- B. a TIA does not cause lasting damage to the brain, while a stroke does
- C. a TIA only affects small blood vessels, while a stroke affects larger vessels
- D. a TIA occurs in individuals under the age of 45 only
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Correct answer: B
The defining difference between a TIA and an actual stroke is that TIAs do not result in a brain infarct, or death of brain tissue, while a true stroke does.
465. Which of the following neurodegenerative diseases specifically targets and causes the degeneration of motor neurons?
- A. Parkinson's disease
- B. Alzheimer's disease
- C. amyotrophic lateral sclerosis (ALS)
- D. Huntington's disease
Show Answer
Correct answer: C
ALS is a neurodegenerative disorder, meaning it is characterized by the degeneration and death of neurons. Specifically, the affected neurons in ALS are upper and lower motor neurons. Upper motor neurons extend from the cerebral cortex or brainstem and carry motor information down to the spinal cord. Lower motor neurons extend from the spinal cord or brainstem to skeletal muscle to cause movement.
466. This sulcus forms a boundary between the parietal and occipital lobes:
- A. intraparietal sulcus
- B. calcarine sulcus
- C. parieto-occipital sulcus
- D. lateral sulcus
Show Answer
Correct answer: C
The parieto-occipital sulcus forms a boundary between the occipital and parietal lobes, primarily on the medial surface of the brain.
467. The secretory cells in the pineal gland that produce melatonin are called:
- A. chromaffin cells
- B. pinealocytes
- C. astrocytes
- D. beta cells
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Correct answer: B
The pineal gland is made up of secretory cells called pinealocytes, which secrete melatonin throughout the 24-hour cycle. Secretion is highest in the middle of the night. It begins to decrease as it gets closer to dawn and is lowest during daylight hours.
468. Which part of a neuron integrates incoming signals to determine whether an action potential will be initiated?
- A. dendrites
- B. axon
- C. synaptic boutons
- D. axon hillock
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Correct answer: D
When information is received at the dendrites, it causes changes in the electrical properties of the cell, and the axon hillock is a region where those changes are integrated to determine if the incoming signals are strong enough for the neuron to initiate its own action potential.
469. A doctor lightly touches a patient's right cornea with a wisp of cotton. Her right eye blinks, but her left eye does not. What does this suggest?
- A. a deficit with the right trigeminal nerve
- B. a deficit with the right facial nerve
- C. a deficit with the left trigeminal nerve
- D. a deficit with the left facial nerve
Show Answer
Correct answer: D
The corneal reflex is used clinically to assess the trigeminal nerve (sensory/afferent limb) and the facial nerve (motor/efferent limb). Touching the right cornea should produce blinking in both eyes. Because the right eye blinks, the right trigeminal nerve and right facial nerve are intact. The absence of blinking in the left eye indicates a deficit in the left facial nerve.
470. The amygdala was named for its resemblance to:
- A. an almond
- B. an acorn
- C. an apricot
- D. an artichoke
Show Answer
Correct answer: A
The term amygdala means “almond,” referring to one of the most prominent nuclei of the amygdala that has an almond-like shape.
471. A patient has a tumor that compresses the dorsal columns-medial lemniscus pathway in the right thalamus. Which of the following deficits would most likely result?
- A. loss of pain and temperature sensation on the left side of the body
- B. loss of fine touch and proprioception on the left side of the body
- C. loss of fine touch and proprioception on the right side of the body
- D. loss of motor function on the right side of the body
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Correct answer: B
The dorsal column–medial lemniscus pathway decussates (crosses) in the medulla. By the time it reaches the thalamus, it is already carrying information from the opposite side of the body, so a lesion here causes loss of fine touch, vibration, and proprioception on the opposite side.
472. Many symptoms of Parkinson’s disease are caused by dopamine deficiency, yet patients are treated with L-DOPA rather than dopamine itself. Why isn’t dopamine administered directly?
- A. dopamine is converted into serotonin in the bloodstream
- B. dopamine causes excessive activation of motor neurons in the spinal cord
- C. dopamine cannot cross the blood-brain barrier, but L-DOPA can
- D. dopamine is less potent than L-DOPA at activating dopamine receptors
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Correct answer: C
While dopamine administered as a drug cannot pass the blood-brain barrier to enter the brain, L-DOPA can, and this characteristic has helped to make L-DOPA the most common treatment for Parkinson’s disease.
473. The somatosensory cortex is arranged in a somatotopic manner. What does this mean?
- A. sensory information is randomly distributed across the cortex
- B. specific regions of the cortex correspond to specific parts of the body
- C. sensory signals are processed according to their intensity, not their location
- D. each sensory modality is processed in separate layers of the cortex
Show Answer
Correct answer: B
Each of the four areas of the primary somatosensory cortex is arranged such that a particular location in that area receives information from a particular part of the body. This arrangement is referred to as somatotopic, and the full body is represented in this way in each of the four regions of the somatosensory cortex.
474. Caffeine's primary mechanism of action is to block receptors for which neurotransmitter?
- A. adenosine
- B. dopamine
- C. GABA
- D. serotonin
Show Answer
Correct answer: A
Most of the effects of caffeine are thought to be traceable back to its action as an antagonist at receptors for a neurotransmitter called adenosine. This means that caffeine binds to adenosine receptors and blocks adenosine from binding there and activating the receptor; thus, it reduces activity at the adenosine receptor.
475. Which of the following is a cell type that a glioma would most likely originate from?
- A. astrocyte
- B. neuron
- C. Schwann cell
- D. meningeal cell
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Correct answer: A
Gliomas are a category of brain tumors that begin in glial cells. The most common glioma is astrocytoma, which arises from the glial cells called astrocytes.
476. A patient presents with numbness and tingling in the thumb, index finger, and middle finger, along with decreased grip strength. The patient is diagnosed with carpal tunnel syndrome. Which nerve is most likely affected?
- A. ulnar nerve
- B. radial nerve
- C. axillary nerve
- D. median nerve
Show Answer
Correct answer: D
Carpal tunnel syndrome is a common condition caused by the compression of the median nerve, which carries sensations from the thumb, index finger, middle finger, and part of the ring finger—primarily on the palm side of the hand—as well as controls most of the muscles in the thumb, some muscles in the forearm that help with finger and wrist movements, and muscles in the index and middle fingers.
477. After a car accident, a patient is evaluated and is found to have experienced complete loss of the left side of her spinal cord at the cervical level. Which of the following deficits is likely to be part of the patient's clinical presentation?
- A. loss of pain and temperature sensation on the left side below the damage
- B. weakness or paralysis on the right side below the damage
- C. loss of touch sensations on the right side below the damage
- D. loss of pain and temperature sensation on the right side below the damage
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Correct answer: D
Complete damage of one half of the spinal cord can result in a condition known as Brown-Sequard syndrome. In this condition, the individual may experience loss of pain and temperature sensation on the opposite side of the damage, below the level of the damage. This is due to the fact that spinothalamic tract fibers (which carry pain and temperature sensations) decussate soon after entering the spinal cord.
478. A patient presents with a sudden, severe “worst headache of their life.” Imaging confirms rupture of a saccular (berry) aneurysm in the Circle of Willis. Which type of brain hemorrhage most commonly results from this event?
- A. epidural hemorrhage
- B. subdural hemorrhage
- C. subarachnoid hemorrhage
- D. intraparenchymal hemorrhage
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Correct answer: C
Subarachnoid hemorrhage can be caused by a variety of conditions, but the most common and severe cases typically result from the rupture of a brain aneurysm. Subarachnoid hemorrhage usually begins suddenly, with a severe headache that develops within seconds, sometimes referred to as a thunderclap headache.
479. Which neuron type is a modified bipolar cell specialized for transmitting sensory signals from the body to the central nervous system in humans?
- A. pyramidal neuron
- B. pseudo-unipolar neuron
- C. multipolar neuron
- D. Purkinje cell
Show Answer
Correct answer: B
Pseudo-unipolar neurons initially form as bipolar neurons, but the dendrite and axon fuse together to form a single process that extends from one part of the cell body. Pseudo-unipolar neurons carry sensory signals, such as information about touch to the spinal cord.
480. Which mechanism best explains how activation of the direct pathway of the basal ganglia is thought to facilitate movement?
- A. excitation of nuclei that inhibit thalamocortical activity
- B. direct excitation of motor cortex neurons by the striatum
- C. increased inhibitory signaling from the thalamus to the cortex
- D. inhibition of nuclei that inhibit thalamocortical neurons
Show Answer
Correct answer: D
The direct pathway promotes movement by inhibiting the globus pallidus internal and substantia nigra pars reticula, which normally inhibit the thalamus. This reduces inhibition of thalamocortical neurons, allowing increased cortical activity and facilitating movement.
