GRE Subject Test: Biology : Understanding Nervous System Structures

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Brain And Central Nervous System

An individual presents to his physician with an abnormal breathing rhythm. The physician suspects that the problem may be originating from his brain. What part of his brain is most likely not functioning properly?

Possible Answers:

Medulla oblongata

Hippocampus

Hypothalamus

Midbrain

Cerebellum

Correct answer:

Medulla oblongata

Explanation:

The medulla oblongata is responsible for autonomic functions, such as breathing rate and heart rate regulation. Dysfunction of the medulla oblongata could result in problems with breathing rhythm.

The cerebellum is responsible for coordination and balance. The hypothalamus regulates the fight-or-flight response, sex drive, thirst, and hunger. The midbrain is the center for auditory and visual signal relay to the cortex. The hippocampus functions in the retention of memories.

Example Question #1 : Understanding Nervous System Structures

Which portion of the neuron receives electrical signals from other neurons?

Possible Answers:

Dendrites

Axon hillock

Axons

Cell body

Correct answer:

Dendrites

Explanation:

The neuron has three major portions: the dendrites, the cell body, and the axon. The dendrites receive electrical stimulation from other neurons, and the axon sends electrical signals to other neurons.

Signals travel down the axon until they reach the axon terminal. Vesicles of neurotransmitter are released from the axon terminal, where they travel across the synapse to the dendrite of the post-synaptic neuron. This initiates a signal in the dendrite, which is carried to the cell body. Signals from different dendrites sum together in the axon hillock, which can stimulate depolarization of the axon and allow for signal propagation.

Example Question #2 : Understanding Nervous System Structures

Which response would be expected from parasympathetic nervous system activity?

Possible Answers:

Contraction of the urethral sphincter

Pupil dilation

Increased heart rate

Relaxation of bronchial smooth muscle

Accommodation of the eye lens for near vision

Correct answer:

Accommodation of the eye lens for near vision

Explanation:

Accommodation of the lens for near vision is a parasympathetic controlled response. Each of the other answer choices is a sympathetic controlled response. The parasympathetic nervous system pertains to "rest and digest" activities. The sympathetic nervous system pertains to "fight or flight" activities. In the case of the eye lens, the ciliary muscle is innervated by parasympathetic fibers, which, when activated, cause the muscle to contract and change the shape of the lens. This alters the refractive capability in a way to accommodate near vision.

Example Question #3 : Understanding Nervous System Structures

Which of the following is true of spinal nerves coming off of the spinal cord?

Possible Answers:

They contain a mixture of motor and sensory neuron axons.

They carry motor neuron axons only.

They do not innervate skeletal muscles.

They do not contain autonomic neuron axons going to organs.

Correct answer:

They contain a mixture of motor and sensory neuron axons.

Explanation:

Spinal nerves coming off of the spinal cord can be thought of as the combination of both posterior and anterior roots. This means that they contain both sensory and motor neuron axons. These nerves can also carry autonomic functions to organs of the body as well.

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