NEUROANATOMY

NEURO ANATOMY

Q. Which motor neurons activate both intrafusal and extrafusal muscle fibers?

A) α-motor neurons

B) β-motor neurons

C) Renshaw cells

D) Golgi tendon organs

E) γ-motor neurons

Ans:  B)

 α-Motor neurons are located in the anterior horn of the spinal cord and activate extrafusal muscle fibers responsible for muscle contraction. γ-Motor neurons innervate intrafusal fibers, which have small axons and control the level of tension on the muscle spindle to control overall muscle length and tone. β-Motor neurons innervate both intrafusal and extrafusal muscle fibers. Renshaw cells are found in the ventral horn and send inhibitory signals to the α-motor neurons. Golgi tendon organs are located in muscle tendons and send inhibitory signals to α-motor neurons that have input to extrafusal muscle fibers, which mediate the inverse stretch reflex.

Q. An injury to the peroneal nerve affects which muscle?

A) Semimembranosus

B) Semiteninosus

C) Adductor magnus

D) Short head of the biceps femoris

E) Long head of the biceps femoris

Ans: D)

The short head of the biceps femoris is the only muscle above the knee that is innervated by the peroneal nerve. The semimembranosus, semitendinosus, and long head of the biceps femoris muscles are innervated by the tibial nerve. The adductor magnus muscle is innervated by the obturator nerve.

Q. Which key neurotransmitter is responsible for innervation of sweat glands?

A) Norepinephrine

B) Dopamine

C) Acetylcholine

D) Serotonin

E) Glutamate

Ans C)

Acetylcholine is the neurotransmitter found in sweat glands. Serotonin, glutamate, and dopamine are central nervous system neurotransmitters not involved in direct innervation of sweat glands.

Q. Which nerve bundle is involved in postganglionic supply to the parotid gland?

A) Submandibular ganglion

B) Superior salivatory nucleus

C) Pterygopalatine ganglion

D) Otic ganglion

E) Inferior salivatory nucleus

Ans: D) The inferior salivatory nucleus projects preganglionic fibers along the glossopharyngeal nerve to the otic ganglion, which in turn projects postganglionic fibers to the parotid gland to stimulate saliva production. The superior salivatory nucleus projects fibers along the facial nerve to the preganglionic fibers to the pterygopalatine ganglion and submandibular ganglion. The pterygopalatine ganglion projects postganglionic fibers to the lacrimal gland and to the mucosa of the nose and palate.

The submandibular ganglion projects postganglionic fibers to the submandibular and sublingual glands.

Q.  You are seeing a patient for visual difficulties. On examination, you find that he has a right lower homonymous quadrantanopsia. Where do you localize the lesion?

A) Pituitary tumor

B) Optic radiation in the left temporal lobe

C) Optic radiation in the left occipital lobe

D) Optic radiation in the left parietal lobe

E) Left frontal lobe

Ans: D) A lesion affecting the optic radiation in the left parietal lobe may result in a right lower homonymous quandrantanopia. A pituitary tumor will usually result in a bitemporal hemianopsia. A lesion of the optic radiation in the left temporal lobe may result in a right upper homonymous quadrantanopia. A lesion of the optic radiation of the left occipital lobe results in a right homonymous hemianopsia. The optic radiation does not run through the frontal lobe. However, the frontal eye field lies in the frontal lobe, and a lesion may cause a gaze palsy in the direction of the side of the lesion.

Q. Which first-order receptor cell in the retina is responsible for day vision, color vision, and high visual acuity?

A) Rods

B) Bipolar neurons

C) Ganglion cells

D) Amacrine cells

E) Cones

Ans: E)

Cones operate at high illumination levels and are responsible for day vision, color vision, and high visual acuity. Rods are sensitive to low-intensity light and are responsible for night vision. Bipolar neurons and amacrine cells transmit stimulation from rods and cones to ganglion cells, which transmit the signals to the hypothalamus, superior colliculus, pretectal nucleus, and lateral geniculate body.

Q. Which structure is involved in the accommodation pathway but not in the pupillary

reflex?

A) Corticotectal tract

B) Posterior commissure

C) Edinger-Westphal nucleus

D) Brachium of superior colliculus

E) Short ciliary nerve

Ans: A)

The corticotectal tract is involved in relaying signal from the occipital lobe through the brachium of the superior colliculus to the accommodation center, which sends a signal to the Edinger-Westphal nucleus or the oculomotor nucleus to initiate accommodation. All other structures are involved in both the papillary reflex pathway and accommodation.

Q. A lesion of which hypothalamic nucleus will most likely result in disruption of the

circadian rhythm?

A) Supraoptic

B) Suprachiasmatic

C) Lateral hypothalamic nucleus

D) Anterior nucleus

E) Paraventricular nucleus

Ans: B)

 The suprachiasmatic nucleus receives direct input from the retina and plays a role in the circadian rhythm. The supraoptic nucleus synthesizes antidiuretic hormone and oxytocin. The lateral hypothalamic region, when stimulated, increases appetite, and destruction results in anorexia and starvation. The anterior nucleus takes part in regulating temperature, and destruction results in hyperthermia. The paraventricular nucleus regulates antidiuretic hormone, and destruction of this nucleus results in diabetes insipidus.

Q. Which is the only excitatory neuron in the cerebellar cortex?

A) Purkinje neuron

B) Basket neurons

C) Stellate cell

D) Granule cell

E) Golgi neuron

Ans: D)

The granule cell is the only excitatory neuron in the cerebellar cortex that is excitatory and stimulates the purkinje, baset, stellate, and golgi cells. Stellate and basket neurons inhibit Purkinje neurons. Golgi neurons inhibit granule cells. Purkinje neurons inhibit neurons in the cerebellar nuclei

Q. Which artery supplies the head of the caudate nucleus?

A) Middle cerebral artery

B) Paracentral artery

C) Pericallosal artery

D) Callosomarginal artery

E) Recurrent artery of Heubner

Ans: E)

Recurrent artery of Heubner. The recurrent artery of Heubner is a branch of the anterior cerebral artery that supplies the anteromedial head of the caudate nucleus.

The pericallosal artery and callosomarginal artery are also branches of the anterior cerebral artery that supply the corpus callosum. The paracentral artery is a branch off the callosomarginal artery that supplies the paracentral lobule (medial part of superior frontal gyrus)

Q. Which of these structures is involved in the auditory system?

A) Superior salivatory nucleus

B) Inferior salivatory nucleus

C) Inferior olivary nucleus

D) Lateral lemniscus

E) Superior colliculus

Ans: D)

The lateral lemniscus carries fibers from the superior olivary nucleus to the inferior colliculus as part of the auditory system. The superior salivatory nucleus projects preganglionic parasympathetic fibers to the pterygopalatine (to the lacrimal gland) and submandibular ganglia (to the submandibular gland). The inferior salivatory nucleus projects preganglionic parasympathetic fibers to the otic ganglion (which then supplies the parotid gland). The superior colliculus is part of the visual system. The inferior olivary nucleus is involved in Mollaret’s triangle, and lesions can contribute to the development of palatal tremor (formerly known as palatal myoclonus).