MCAT Biology : Divisions of the Nervous System
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Example Question #175 : Mcat Biological Sciences
Which of the following accurately describes white matter?
White matter is denser than gray matter
White matter is only found in the peripheral nervous system
White matter is located in the central part of the spinal cord and is surrounded by gray matter
White matter features the cell bodies of the neurons in the spinal cord
White matter consists of myelinated axons in the central nervous system
White matter consists of myelinated axons in the central nervous system
White matter refers to the white-colored myelin that surrounds the axons of neurons in the central nervous system. These axons are grouped together, creating distinct regions of white matter. In contrast, grey matter refers to the cell bodies of neurons in the central nervous system. The cell bodies are packed together into dense regions to create grey matter.
In a cross-section of the spinal cord, gray matter is located in the center and is surrounded by white matter.
Example Question #176 : Mcat Biological Sciences
Which is the correct order of sequences during the knee-jerk reflex?
Patella tendon stretches – sensory neuron – spinal cord –brain – motor neuron – quadriceps contract (reflex bypasses the brain)
Patella tendon stretches – motor neuron – spinal cord – sensory neuron – quadriceps contract
Patella tendon stretches – sensory neuron – spinal cord – motor neuron – quadriceps contract
Patella tendon stretches – spinal cord – sensory neuron – motor neuron – quadriceps contract
Quadriceps stretch – sensory neuron – spinal cord – motor neuron – patella tendon contracts
Patella tendon stretches – sensory neuron – spinal cord – motor neuron – quadriceps contract
During the knee-jerk reflex, the neural signal is initiated by the stretching of the patella tendon, which is transmitted via sensory neuron to the spinal cord. In turn, the signal is transmitted to the motor neuron, resulting in the contraction of quadriceps. Most importantly, the reflex bypasses the brain, allowing a speedy reaction of the body to the stimulus.
Example Question #21 : Divisions Of The Nervous System
A patient who is unable to modulate his own ventilation and heart rate may be suffering damage to which part of his brain?
Midbrain
Medulla oblongata
Temporal lobes
Corpus callosum
Cerebellum
Medulla oblongata
The medulla oblongata, a part of the hindbrain, is primarily responsible for the control of ventilation and heart rate. The midbrain serves as a relay station for visual and auditory information. The cerebellum is responsible for balance and coordination. The corpus callosum is a connective tissue between the two hemispheres of the brain and allows for their intercommunication. The temporal lobes are primarily responsible for auditory processing. Therefore, the patient is most likely suffering from a damage to the medulla oblongata.
Example Question #21 : Divisions Of The Nervous System
The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.
Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma.
Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.
When a physician performs a lumbar puncture, he/she is extracting cerebrospinal fluid. Through which of the follow structure(s) must the needle pass?
I. Dura mater
II. Arachnoid mater
III. Pia mater
II only
I and II
I only
III only
I, II, and III
I and II
As described in the passage, the innermost layer is the pia mater, then the arachnoid space, arachnoid mater and finally the dura mater. The dura mater is the outermost layer prior to the skull/vertebral column. Therefore, during a lumbar puncture, the needle will have to pass through the dura mater first then through the arachnoid mater to get to the sub-arachnoid space.
Example Question #13 : Brain And Central Nervous System
The central nervous system consists of the brain and the spinal cord. In general, tracts allow for the brain to communicate up and down with the spinal cord. The commissures allow for the two hemispheres of the brain to communicate with each other. One of the most important commissures is the corpus callosum. The association fibers allow for the anterior regions of the brain to communicate with the posterior regions. One of the evolved routes from the spinal cord to the brain is via the dorsal column pathway. This route allows for fine touch, vibration, proprioception and 2 points discrimination. This pathway is much faster than the pain route. From the lower limbs, the signal ascends to the brain via a region called the gracile fasciculus. From the upper limbs, the signal ascends via the cuneate fasciculus region in the spinal cord.
Patient A has a tumor in his spinal cord. He is able to feel fine touch below the waist. Above the waist, he is unable to feel fine touch on either side. Where is the tumor most likely located?
I. All levels of the spinal cord
II. In the gracile fasciculus region
III. In the cuneate fasciculus region
II only
None of these
I only
III only
I and II
III only
Patient A is unable to feel fine touch above the waist. A tumor in the cuneate fasciculus region will prevent the signal to travel from above the waist to reach the brain.
Example Question #14 : Brain And Central Nervous System
The central nervous system consists of the brain and the spinal cord. In general, tracts allow for the brain to communicate up and down with the spinal cord. The commissures allow for the two hemispheres of the brain to communicate with each other. One of the most important commissures is the corpus callosum. The association fibers allow for the anterior regions of the brain to communicate with the posterior regions. One of the evolved routes from the spinal cord to the brain is via the dorsal column pathway. This route allows for fine touch, vibration, proprioception and 2 points discrimination. This pathway is much faster than the pain route. From the lower limbs, the signal ascends to the brain via a region called the gracile fasciculus. From the upper limbs, the signal ascends via the cuneate fasciculus region in the spinal cord.
Which of the following sentences correctly explains what happens when a person steps on a pin?
I. Transmit to the brain rapidly
II. Will utilize the gracile fasciculus region in the spinal cord
III. Will utilize the cuneate fasciculus region in the spinal cord
I only
None of these
II and III
II only
III only
None of these
Fine touch, vibration, proprioception and 2 points discrimination all utilizes the dorsal column pathway. The upper region utilizes the cuneate fasciculus in the spinal cord while the lower region depends on the gracile fasciculus. According to the passage, these sensations are of the rapid pathway whereas other sensations such as pain is not as fast. The dorsal column pathway is heavily myelinated while the pain pathway is not as myelinated.
Example Question #83 : Nervous System And Nervous Tissue
The central nervous system consists of the brain and the spinal cord. In general, tracts allow for the brain to communicate up and down with the spinal cord. The commissures allow for the two hemispheres of the brain to communicate with each other. One of the most important commissures is the corpus callosum. The association fibers allow for the anterior regions of the brain to communicate with the posterior regions. One of the evolved routes from the spinal cord to the brain is via the dorsal column pathway. This route allows for fine touch, vibration, proprioception and 2 points discrimination. This pathway is much faster than the pain route. From the lower limbs, the signal ascends to the brain via a region called the gracile fasciculus. From the upper limbs, the signal ascends via the cuneate fasciculus region in the spinal cord.
Patient A has a tumor in his spinal cord. He is able to feel fine touch above the waist. Below the waist he is unable to feel fine touch on either side. Where is the tumor most likely located?
I. All levels of the spinal cord
II. In the gracile fasciculus region
III. In the cuneate fasciculus region
I only
I and II
II only
None of these
III only
II only
Patient A is unable to feel fine touch below the waist. A tumor in the gracile fasciculus region will prevent the signal from below the waist to reach the brain.
Example Question #21 : Divisions Of The Nervous System
Your hand jerks back when you touch a hot stove. Which of the following describes the pathway of nerve impulses responsible for this reflex?
Motor neuron → sensory neuron → interneuron
Interneuron → sensory neuron → motor neuron
Sensory neuron → interneuron → motor neuron
Motor neuron → interneuron → sensory neuron
Sensory neuron → motor neuron → interneuron
Sensory neuron → interneuron → motor neuron
Messages are picked up by sensory neurons in the peripheral nervous system and passed to interneurons in the central nervous system; responses are passed on to motor neurons in the peripheral nervous system
Example Question #22 : Divisions Of The Nervous System
When you stare directly at an object, the image focuses on what part of the retina?
Lens
Optic disk
Fovea centralis
Choroid
Pupil
Fovea centralis
The fovea centralis, also known as the focal point, is the point where an image is centered when you stare at objects. This region of the retina has a high number of cone and rod cells, and explains why we can only clearly focus on one object at a time. Only the object lined up with the fovea centralis will remain clear, while peripheral objects appear blurry.
Example Question #3 : Sensory Organs
Which of the following is true about the cornea?
It is largely made of lipids
It is avascular
It is clear with a refractive index of 0.6
Elasticity of the cornea declines with age
It is avascular
The cornea is avascular and made primarily of collagen, not lipids. When light first reflects off of a focused object, it strikes the eye on the cornea, where its high refractive index (1.4) allows most of the bending of light to occur at the interface between air and cornea. Unlike the lens, the cornea does not change its shape. The lens is tethered by suspensory ligaments, which are further connected to ciliary muscles. When the ciliary muscles contract, they release tension on the suspensory ligaments, thus making the lens more spherical and bringing the focal point closer to the lens.
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