Human Anatomy and Physiology : Nervous System

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

Example Question #11 : Nervous System

Which cranial nerves (CN) are responsible for the pupillary light reflex?

Possible Answers:

CNs V and VII

CN V only

CN XII

CNs II and III

CNs IX and X

Correct answer:

CNs II and III

Explanation:

The pupillary light reflex and ocular accommodation reflex involves cranial nerve II for the sensory aspect and cranial nerve III for the motor application. The jaw jerk reflex uses cranial nerve V for both sensory and motor. The corneal (blink reflex) utilizes cranial nerve V for sensory and VII for motor. The gag reflex utilizes cranial nerve IX for sensory and X for motor. 

Example Question #12 : Nervous System

Which cranial nerves are responsible for the gag reflex?

Possible Answers:

CNs V and VII

CNs IX and X

CNs II and III

CN V only

CN X only

Correct answer:

CNs IX and X

Explanation:

The gag reflex utilizes cranial nerve IX for sensory and X for motor. The pupillary light reflex and ocular accommodation involves cranial nerve II for the sensory aspect and cranial nerve three for the motor application. The jaw jerk reflex uses cranial nerve V for both sensory and motor. The corneal (blink reflex) utilizes cranial nerve V for sensory and VII for motor.

Example Question #13 : Nervous System

Which of the following is the nerve root for the sciatic nerve?

Possible Answers:

L3-L5

L4-S1

L2-L4

L4-S2

L4-S3

Correct answer:

L4-S3

Explanation:

The sciatic nerve is a large nerve that runs through the buttocks and down the lower limb. The sciatic nerve innervates skin of the leg, and muscles in the posterior thigh, leg, and foot. The sciatic nerve is derived from spinal nerves L4-S3. The L4-S3 nerve root also supplies the tibial nerve.

L4-S1 is the nerve root for the superior gluteal nerve. Common fibular nerve is supplied by spinal nerves L4-S2. The obturator and femoral nerves are derived from L2-L4.

Example Question #14 : Nervous System

Which of the following is the nerve root for the femoral nerve?

Possible Answers:

L2-L4

L4-S3

L1-L4

L4-S2

L4-S1

Correct answer:

L2-L4

Explanation:

The femoral nerve is a nerve in the thigh that innervates the skin on the upper thigh and inner leg and shin. It also innervates the muscles that extend the knee (quadriceps). It is the largest branch of the lumbar plexus and derives from spinal nerves L2-L4. The obturator nerve is also supplied by spinal nerves L2-L4.

The sciatic nerve is derived from spinal nerves L4-S3. The L4-S3 nerve root also supplies the tibial nerve. L4-S1 is the nerve root for the superior gluteal nerve. Common fibular nerve is supplied by spinal nerves L4-S2.

Example Question #15 : Nervous System

The ankle jerk (Achilles) reflex tests which nerve root?

Possible Answers:

S1, S2

S3, S4

L2, L3, L4

C5, C6

L5, S1

Correct answer:

S1, S2

Explanation:

The ankle jerk (Achilles) reflex tests the nerve root S1, S2. Biceps reflex tests roots C5, C6. Brachioradialis tests C5, C6, C7. Triceps reflex tests C6, C7, C8 nerve roots. Patellar (knee jerk) reflex tests the L2, L3, L4 nerve roots. The hamstring reflex tests nerve roots L5 and S1.

Example Question #16 : Nervous System

A sudden, uncontrolled flinging movement of a limb can best be described by which of the following?

Possible Answers:

Hemiballism

Chorea

Tremor

Dystonia

Correct answer:

Hemiballism

Explanation:

Hemiballism describes a sudden, uncontrolled flinging movement; this occurs if there is damage/destruction of subthalamic nuclei. Chorea is an abnormal, involuntary movement that can be seen in Huntington's disease; it occurs after destruction of the caudate nucleus. Dystonias are abnormal movements and are most often referred to as resting tremors of Parkinson's disease. Parkinsons disease results from a loss of dopamine from the substantia nigra. 

Example Question #17 : Nervous System

The dermatome for the inguinal region is which of the following?

Possible Answers:

S2

L5

L1

S1

L4

Correct answer:

L1

Explanation:

A dermatome is an area of skin supplied by a single spinal nerve. Along the thorax and abdomen the dermatomes are stacked like coins/discs, each layer supplied by a different spinal nerve. Along the arms and legs the pattern is different. Symptoms that follow a dermatome may indicate a pathology that involves the nerve root. There are a number of important dermatomes one being the inguinal region innervated by the L1 nerve root.

Example Question #18 : Nervous System

Which of the following innervates the dermatome at the umbilicus?

Possible Answers:

T4

T10

T9

L4

T11

Correct answer:

T10

Explanation:

A dermatome is an area of skin supplied by a single spinal nerve. Along the thorax and abdomen the dermatomes are stacked like coins/discs, each layer supplied by a different spinal nerve. Along the arms and legs the pattern is different. Symptoms that follow a dermatome may indicate a pathology that involves the nerve root. There are a number of important dermatomes one being the layer of the umbilicus innervated by the T10 nerve root.

Example Question #19 : Nervous System

In a comatose patient, how is a positive doll’s eyes test interpreted?

Possible Answers:

The patient does not a have an intact oculocephalic reflex

The patient has an intact oculocephalic reflex

The patient has a spinal cord injury

The patient has an intact flexor withdrawal reflex

Correct answer:

The patient has an intact oculocephalic reflex

Explanation:

Because comatose patients cannot visually track objects, brainstem function is assessed by testing the oculocephalic reflex. Making sure any cervical spine pathology, the patients eyelids are held open, and her head is turned to side. If the eyes move in the opposite direction, the oculocephalic reflex is said to be positive, and indicates that there is some intact brainstem function. Because it is reminiscent of the way a doll's eyes move, this test is sometimes called a doll's eyes test. 

Example Question #20 : Nervous System

Which of the following might you see in an adult patient with a suspected upper motor neuron lesion?

Possible Answers:

Positive pronator drift

All of these signs could suggest an upper motor lesion

Positive Babinski sign

Positive crossed adductor reflex

Positive Hoffman’s reflex

Correct answer:

All of these signs could suggest an upper motor lesion

Explanation:

An upper motor neuron lesion is an injury to the motor pathways of the central nervous system, before the level of the cranial nerve nuclei, or the ventral horn of the spinal cord. The key to this question is that the patient is an adult; in children, under the age of 2, a positive Babinski sign is a normal finding. However, a positive crossed adductor reflex, a positive pronator drift sign, and a positive Hoffman's reflex are always pathological, and may indicate an upper motor neuron lesion.

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