MLT GlobePhysiology: Nervous system & special senses – page 2
68 Physiology MCQs on Nervous system & special senses with answers and explanations.
A patient with a lesion causing an unsteady, wide-based gait and poor balance most likely has damage to the:
The cerebellum coordinates movement and keeps posture, balance and equilibrium. Damage produces ataxia, an unsteady wide-based gait and intention tremor.
A 50-year-old needs reading glasses because the lens stiffens and can no longer thicken for near vision. This is:
Presbyopia is age-related loss of accommodation as the lens loses elasticity. Myopia is short-sightedness and astigmatism is uneven corneal curvature.
Shining a torch into a patient's eye makes both pupils constrict. What kind of response is this?
The pupillary light reflex runs from the optic nerve to the midbrain and back via parasympathetic fibres of the oculomotor nerve to the sphincter pupillae; it needs no conscious control.
An elderly patient has cloudy vision due to clouding of the lens. This condition is called:
Cataract is opacification of the lens. Retinal detachment separates retinal layers, strabismus is ocular misalignment, and glaucoma involves raised intraocular pressure damaging the optic nerve.
The retinal point of sharpest vision, packed with cones, lies in the centre of the:
The fovea centralis sits within the macula and contains only cones. The optic disc lacks photoreceptors and forms the blind spot.
A tonometry reading is being interpreted. What is the usual normal range of intraocular pressure?
Normal intraocular pressure is about 10–21 mmHg. Sustained higher values are a major risk factor for glaucoma.
With eyes closed, a person can tell the position of a bent knee. This is which type of sensation?
Proprioception from muscle spindles, tendon organs and joint receptors signals limb position and movement without vision.
Because its preganglionic neurons arise from spinal segments T1–L2, the sympathetic division is called the:
Sympathetic preganglionic cell bodies lie in the lateral horns of T1–L2. The parasympathetic division is the craniosacral outflow.
Loss of pain and temperature sensation on one side of the body suggests damage to which spinal pathway?
Pain and temperature fibres cross near their entry level and ascend in the lateral spinothalamic tract. Dorsal columns carry fine touch and vibration; corticospinal tracts and ventral roots are motor.
Which cranial nerve does NOT carry taste fibres?
Taste travels in the facial (anterior two-thirds of tongue), glossopharyngeal (posterior third) and vagus (epiglottis) nerves. The olfactory nerve carries smell.
Which brain region acts as the body's thermostat?
The preoptic hypothalamus sets core temperature. Pyrogens such as IL-1 and PGE2 raise this set-point to produce fever.
When the eye focuses on a nearby object, the main change that increases refractive power is:
Ciliary muscle contraction slackens the zonules, so the elastic lens becomes rounder. Pupil constriction and convergence accompany this but add little refractive power.
The vestibulocerebellum (flocculonodular lobe), with brainstem and spinal connections, chiefly controls:
The vestibulocerebellum receives vestibular input and controls equilibrium, posture and eye movements. The cerebrocerebellum plans skilled movements.
The resting membrane potential of a neurone is mainly set up by:
Resting membranes are most permeable to K+ through leak channels, so K+ efflux brings the potential near the K+ equilibrium potential. The pump maintains gradients but adds only a few mV directly.
Most sound energy would be reflected at the air-fluid interface of the inner ear without a mechanism that matches impedance. This role is performed by the:
The large drum and ossicle lever concentrate force on the small oval window, amplifying pressure about 20-fold. The two muscles dampen loud sound instead.
A patient with a fourth cranial nerve palsy has difficulty looking down while the eye is adducted. The paralysed muscle is the:
The trochlear nerve (CN IV) supplies only the superior oblique. The oculomotor nerve supplies the recti except lateral rectus, plus the inferior oblique.
Which statement about normal cerebrospinal fluid is correct?
CSF is clear, pH about 7.3, SG about 1.005, made at about 0.35-0.5 mL/min, with up to 5 lymphocytes/uL and no neutrophils.
Rods contain rhodopsin. What is the protein part of the photopigments in cones called?
Cone pigments combine retinal with one of three photopsins. Rhodopsin in rods is scotopsin plus retinal, and transducin is the G protein in the cascade.
The fovea centralis gives the sharpest visual acuity mainly because it contains:
The fovea is a small pit of tightly packed cones, with overlying layers pushed aside and no rods, giving high acuity and colour vision. The optic disc is the blind spot.
After severe damage to Wernicke's area, a patient would most typically:
Wernicke's area interprets language, so damage causes fluent but meaningless speech and poor comprehension (receptive aphasia). Halting speech with good understanding points to Broca's area.