Tag: nervous system

• The autonomic nervous system is divided into two subdivisions. They are the sympathetic and parasympathetic nervous system.
• The sympathetic nervous system (SNS) controls the body's responses to a perceived threat and is responsible for the "fight or flight" response while The parasympathetic nervous system (PNS) controls homeostasis and the body at rest and is responsible for the body's "rest and digest" function.
  
• Hence Sympathetic and parasympathetic nervous systems are often antagonistic(opposing) in their functions.
• So, the given statement is false.

• The nervous system is divided into two major subdivisions. They are the Central nervous system(brain and spinal cord) and peripheral nervous system.
• The peripheral nervous system is in turn divided into two divisions. They are a somatic and autonomic nervous system.
• The main function of the PNS is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body.
  
• The autonomous nervous system is completely independent of the central nervous system is a false statement because, within the brain, the autonomic nervous system is regulated by the hypothalamus(part of CNS).
  

The sympathetic nervous system controls the fight response in the body. The parasympathetic nervous system controls the feed and breed activities of the body. The sympathetic nervous system (SNS) acts as an antagonist to the action of the parasympathetic nervous system(PNS) and the PNS acts as an antagonist to the action of SNS.

Myelin sheath is the insulating envelope of myelin, that surrounds the core of a nerve fiber or axon and that facilitates the transmission of nerve impulses, formed from the cell membrane of the Schwann cell in the peripheral nervous system and from oligodendroglia cells. Nonmyelinated nerve fiber lacks the fatty myelin insulating sheath. Such fibers form the gray matter of the nervous system, as distinguished from the white matter of myelinated fibers. 

The pupillary light reflex is a reflex that controls the diameter of the pupil, in response to the intensity of light that falls on the retina of the pupil and the eye. Parasympathetic nerve fibres from the third (oculomotor) cranial nerve innervate the muscle that causes constriction of the pupil, whereas sympathetic nerve fibres control dilation. 

The sympathetic branch of our autonomic nervous system originates in the spinal cord. It goes into action to prepare the body for physical or mental activity. Its general action is to mobilize the body in a fight response. It increases muscle blood flow and tension, dilates pupils, accelerates heart rate and respiration, and increases perspiration and arterial blood pressure. To conserve and concentrate energy, it slows down digestive activity.

Sympathetic and parasympathetic divisions function in opposition to each other. 

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.