Tag: nervous system of man

Vagus is $10^{th}$ cranial nerve. It originates from the sides of medulla oblongata. In vertebrates it consists of sensory and motor fibres.

The central nervous system includes brain and spinal cord. It integrates and stores the sensory information from external and internal sense organs and commands different organs to respond accordingly. This makes option A incorrect. Peripheral nervous system lies outside the central nervous system. It serves to carry the sensory information from external sensory receptors to CNS and motor signals from CNS to skeletal muscles via its somatic division (the voluntary actions). The autonomous division of peripheral nervous system controls the cardiac and smooth muscles and glands, thereby the functioning of internal organs, without our conscious control (the involuntary actions). This makes option B incorrect and option C correct. The 12 pairs of cranial nerves are part of peripheral nervous system and are mostly concerned with head, neck and facial region of the body (vagus nerve X being the part of autonomous division serves as an exception). Option D is incorrect.  Correct answer is C. 

• Myenteric plexus is also called as Auerbach's plexus, they are nerve cells and are controlled by the parasympathetic nervous system. It controls peristalsis (Swallowing of food).
  
• Argentaffin cells are present at the lining of the gastrointestinal tract and perform the function of secretion thus produces serotonin.
• Meissner's plexus is also called as submucosal plexus, it is located on the lining of the mucosa. It is responsible for the secretion of intestinal juice.
• The liver also called as 'Hepar' that contains hepatic cells. These hepatic cells are responsible for the secretion of heparin.
• So, the correct option is 'A - (ii), B - (i), C - (iv), D - (iii)'.

The sense of smell and sight of food are governed by olfactory and optic responses which work together to initiate the neural response during cephalic phase of digestion. Sight, smell and sense of food initiate the neural response in which central nervous system prepares the stomach to receive food. The responses include salivation and secretion of gastric juices. This makes options C and D incorrect and option B correct. The ingestion of food stimulates the hormonal responses to food which includes endocrine system to ensure releases of various digestive hormones at appropriate time. Correct answer is B.

The sympathetic system is the system which mainly controls the involuntary actins. There are two kinds of neurons involved in the transmission of any signal through the sympathetic system: pre-ganglionic and post-ganglionic. The shorter preganglionic neurons originate from the thoracolumbar region of the spinal cord (levels $T _1$-$L _2$). So, the correct answer is option C.

The tissue of the brain and spinal cord, consisting mainly of nerve fibres with their myelin sheaths is the white matter, that transmit signals from one region of the cerebrum to another and between the cerebrum and lower brain centres. In contrast, the darker tissue of the brain and spinal cord, consisting mainly of nerve cell bodies and branching dendrites is the grey matter. The function of grey matter is to route sensory or motor stimuli to interneurons of the CNS in order to create a response to the stimulus through chemical synapse activity.
So, the correct answer is option C.

Based on the presence and absence of notochord animals are distinguished into chordates and non chordates. Nerve cord is ganglionated, double ventral and solid.