MLT GlobePhysiology: Nervous system & special senses – page 3
68 Physiology MCQs on Nervous system & special senses with answers and explanations.
Broca's motor speech area is located in the:
Broca's area lies in the inferior frontal gyrus of the dominant hemisphere, above the lateral fissure. The strip in front of the central sulcus is the primary motor cortex.
Wernicke's area, needed for understanding spoken and written language, is found in which lobe of the dominant hemisphere?
Wernicke's area lies in the posterior part of the superior temporal gyrus, close to the auditory cortex. Broca's area, for speech production, is in the frontal lobe.
Drooping of the upper eyelid (ptosis) is due to weakness of which muscle?
The levator palpebrae superioris, supplied by the oculomotor nerve (with a small sympathetic smooth-muscle part), raises the upper eyelid. Orbicularis oculi closes the eye.
On the sensory homunculus, which region has a particularly large cortical area compared with its body size?
Cortical area reflects receptor density, not body size. The lips, face and fingers occupy large areas of the somatosensory cortex, while the trunk and proximal limbs occupy little.
Which glial cells form myelin sheaths in the central nervous system?
Each oligodendrocyte myelinates segments of several CNS axons. Schwann cells myelinate peripheral nerves; astrocytes support neurones and the blood-brain barrier.
When reading a line of text, the eyes jump rapidly from one word to the next. These quick jumps are called:
Saccades shift gaze between successive fixation points. Smooth pursuit tracks a moving target; vergence changes the angle between the eyes for near or far objects.
Touching the back of the pharynx triggers the gag reflex. Which cranial nerve carries the sensory (afferent) limb?
Pharyngeal sensation travels in cranial nerve IX; the motor response is mainly via the vagus (X). The hypoglossal nerve moves the tongue.
Earwax is produced in the external acoustic meatus because its lining contains:
The external canal is lined by skin with modified apocrine ceruminous glands and hairs that trap debris. The middle ear, not the external canal, is equalised via the auditory tube.
Conscious perception of sound as heard speech or music takes place in the:
Hair cells transduce vibration into nerve impulses, but perception happens in the primary auditory cortex of the superior temporal gyrus.
Which condition causes a conductive rather than a sensorineural hearing loss?
Middle-ear fluid in otitis media blocks sound transmission to the inner ear. The other options damage the cochlea itself, causing sensorineural loss.
Hair cells that detect head tilt and linear acceleration are found mainly in which structure?
Utricular and saccular maculae, with otoliths, sense static head position and linear acceleration. Semicircular canal cristae detect rotational acceleration; the organ of Corti serves hearing.
Which statement about the ciliary body is FALSE?
The ciliary muscle adjusts lens shape for accommodation; pupil dilation is performed by the dilator pupillae in the iris. The other statements about the ciliary body are correct.
After partial crossing at the optic chiasma, each optic tract carries fibres from:
Nasal fibres cross at the chiasma while temporal fibres stay ipsilateral, so each tract carries information about the opposite visual field from both eyes.
The primary somatosensory cortex in the postcentral gyrus corresponds to which Brodmann areas?
Areas 3, 1, 2 form the primary somatosensory cortex. Area 4 is primary motor, area 6 premotor, and areas 41–42 auditory cortex.
When the eyes shift focus to a book held close, which change does NOT occur?
Near vision involves accommodation (rounder lens), convergence and pupillary constriction, with light refracted onto the retina. Pupils constrict, not dilate, for near objects.
A driver with sight in only one eye struggles to judge the distance of oncoming cars. This reflects loss of:
Stereoscopic depth perception depends on combining slightly different images from both eyes. With monocular vision, distance and speed judgement is impaired.
In control of antigravity muscles, the pontine reticular formation mainly excites extensors. Which region has the opposite, inhibitory effect?
The pontine reticular system excites antigravity muscles, while the medullary reticular system inhibits them. Vestibular nuclei also excite extensors.
Climbing fibres that reach the cerebellum through the olivocerebellar tract arise from the:
The inferior olive is the sole source of climbing fibres to Purkinje cells. The superior olive is an auditory relay.
A lesion of the globus pallidus classically produces slow, writhing movements of the hands, known as:
Athetosis is linked to globus pallidus lesions. Hemiballismus follows subthalamic lesions, chorea caudate or putamen damage, and parkinsonian tremor substantia nigra loss.
When cochlear hair-cell stereocilia bend, which ion enters from the endolymph and depolarises the cell?
Endolymph is unusually rich in K+, so opening of mechanotransduction channels lets K+ flow in and depolarise the hair cell. Ca2+ entry then triggers transmitter release.