Neural Control and Coordination – Human Neural System: NEET MCQs with Answers

Explanation: The X cranial nerve is the vagus or pneumogastric nerve, which originates from the lateral side of the medulla oblongata behind the IX cranial nerve. It is a mixed nerve whose sensory fibres innervate receptors in the walls of visceral organs and whose motor fibres innervate the muscles of the heart, alimentary canal, trachea, lungs, kidneys and genital tracts; it also regulates the heartbeat.

Explanation: The parasympathetic nervous system relaxes the body after periods of stress or danger. It conserves energy and brings about relaxation, comfort and pleasure at times of rest. During an emergency the sympathetic system dilates the pupil for more light; afterwards the parasympathetic system constricts the pupil back to its normal condition.

Explanation: Afferent nerve fibres are formed of sensory nerve fibres only. They conduct nerve impulses from sensory organs or receptors to the central nervous system to produce sensation — the optic nerve is an example.

Explanation: Sympathetic nerves arise from the thoracic and lumbar spinal segments. The system is represented by a chain of 21 sympathetic ganglia on either side of the spinal cord.

Explanation: Both sympathetic and parasympathetic nerve fibres innervate the visceral organs and coordinate their activity antagonistically. However, this coordination is autonomic — it is not under the body's conscious control.

Explanation: The vagus nerve is the X cranial nerve. It is mixed in nature, having both sensory and motor fibres.

Explanation: Sympathetic nerves of the autonomic nervous system increase the rate and strength of the heartbeat, preparing the body for emergencies. Secretion of saliva and digestive juices is stimulated mainly by the parasympathetic system.

Explanation: The vagus nerve has the highest number of branches. It originates from the medulla oblongata of the brainstem and gives off five main branches — the superior laryngeal, recurrent laryngeal, cardiac, pneumogastric and depressor nerves. The facial nerve mainly controls facial expression and taste sensation, while the trigeminal is the local nerve for sensation in the face.

Explanation: The vagus is a mixed cranial nerve that controls much of the gut, the ventilatory system and the heart. It does not affect tongue movement, which is controlled by the glossopharyngeal (and hypoglossal) nerves.

Explanation: The abducens (abducent) nerve is a cranial nerve originating from the ventral surface of the medulla oblongata. It innervates the lateral rectus muscle of the eyeball, and being a motor nerve it controls the movements of the eyeball; injury to it will therefore affect eyeball movement.

Explanation: The nervous and endocrine systems regulate each other: the hypothalamus controls the pituitary and other endocrine glands, and hormones in turn influence neural activity.

Explanation: Parasympathetic neural signals reduce both the heart rate and the cardiac output. They act through the post-ganglionic fibres, which are very short and cholinergic in nature.

Explanation: Parasympathetic neural signals, a component of the autonomic nervous system, decrease the rate of the heartbeat and the speed of conduction of the action potential, and thereby reduce the cardiac output.

Explanation: In the cold, the body narrows skin blood vessels to reduce heat loss and shivers to generate heat, correcting the fall in temperature, which is negative feedback. In heat the skin vessels dilate rather than constrict, and tear secretion or salivation at the sight of food are simple reflexes.

Explanation: Peristalsis proceeds without any awareness on our part and is regulated by the autonomic supply to the gut. Swallowing has a voluntary first stage, and the knee jerk is a somatic spinal reflex involving skeletal muscle rather than smooth muscle or glands.