Nervous System In Man - SS3 Biology Past Questions and Answers - page 2

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The human nervous system is a complex network of cells, tissues, and organs that coordinates and controls various bodily functions. It is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord, while the PNS includes all the nerves that connect the CNS to the rest of the body. The brain is the central control centre of the nervous system, responsible for processing sensory information, initiating motor responses, and performing higher cognitive functions. The spinal cord serves as a relay system, transmitting signals between the brain and the peripheral nerves. The PNS, on the other hand, carries information to and from the CNS, enabling communication with the body's organs, muscles, and glands. The nervous system communicates through specialized cells called neurons, which transmit electrical signals, or nerve impulses, across synapses. Neurotransmitters facilitate the transmission of signals between neurons. This communication network allows for the regulation of bodily processes, perception of sensory stimuli, and execution of voluntary movements, among other functions.

The human nervous system is further divided into the autonomic nervous system (ANS) and the somatic nervous system (SNS), each serving distinct functions in maintaining homeostasis. The autonomic nervous system regulates involuntary activities of internal organs and glands. It consists of two branches: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic division prepares the body for "fight or flight" responses during stressful or dangerous situations. It increases heart rate, dilates pupils, and diverts blood flow to muscles, enabling quick reactions. Conversely, the parasympathetic division promotes "rest and digest" responses, conserving energy and aiding in digestion, reducing heart rate, and constricting pupils. On the other hand, the somatic nervous system controls voluntary movements and sensory information. It allows individuals to interact with the external environment through conscious actions. Sensory neurons convey information from the senses to the CNS, while motor neurons carry signals from the CNS to muscles, enabling precise movements. The ANS and SNS work together to maintain internal balance (homeostasis) in the body. For instance, when the body experiences stress (e.g., running from a predator), the sympathetic system activates to increase heart rate and release adrenaline, while the parasympathetic system later counteracts this response, slowing down the heart rate once the threat has passed.