Tag: zoology

The autonomic nervous system (ANS), also known as the visceral nervous system and involuntary nervous system, is a division of the peripheral nervous system, that influences the function of internal organs. The autonomic nervous system is a control system, that acts largely unconsciously and regulates the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.

If parasympathetic nerve of the rabbit is cut, the most immediate effect would be an increase in heart rate. Also, the regulation of heart rate, contractile state, and conduction of electrical impulses through the heart would be impaired. The reason for the observed effects is that the vagus nerve carries important information to the heart from a part of the central nervous system called the parasympathetic nervous system. The parasympathetic nervous system is often considered the "rest and digest" system. It decreases heart rate, decreases how strongly the heart contracts with each beat, and decreases the rate at which electrical impulses are conducted through the heart.

Parasympathetic autonomic nervous system (PNS) responses are highly specific, as supported by the direct innervation of target organs. The PNS is inhibitory, and promotes energy conservation. The primary defense strategies supported by the PNS involve energy conservation. PNS activation promotes passive coping strategies, such as withdrawal or disengagement, dissociation and the immobility response. Examples of passive coping styles include physical or emotional withdrawal.

The autonomic nervous system is the part of the nervous system, that supplies the internal organs, like blood vessels, stomach, intestine, liver, kidneys, bladder, genitals, lungs, pupils, heart, and sweat, salivary, and digestive glands. 

Urinary storage is a function of the sympathetic nervous system, whereas micturition is a function of the parasympathetic nervous system.

Parasympathetic innervation leads to pupillary constriction. A circular muscle called as the sphincter pupillae accomplishes this task. Sympathetic innervation leads to pupillary dilation. Dilation is controlled by the dilator pupillae, a group of muscles in the peripheral 2/3 of the iris.

Acetylcholine is the main vagal neurotransmitter. The vagus nerve controls the heart rate by electrical impulses to the SA node of the heart in which acetylcholine release slows down the pulse rate and decreases the blood pressure. Thus the correct answer is option A.

Sympathetic nervous system inhibits salivary gland secretion, accelerates the heart rate, decreases intestinal peristalsis and dilate the pupil of the eye. Whereas parasympathetic nervous system stimulates salivary gland secretion, slows heart rate, stimulates intestinal peristalsis and constricts pupil of the eye. The sympathetic and the parasympathetic nervous system are parts of the autonomic nervous system. These systems work in balance with each other and directly or indirectly affect almost every structure in the body. The sympathetic nervous system has an active "pushing" function, the parasympathetic has mainly a relaxing function.

Constriction of the pupil is the function of the parasympathetic system. The parasympathetic nervous system is one of the two divisions of the autonomic nervous system, the other is the sympathetic nervous system. The autonomic nervous system is responsible for regulating the body's unconscious actions. The parasympathetic system is responsible for stimulation of "rest and digest" or "feed and breed" activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion and defecation. 

The central nervous system (CNS) 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.