Unit-I: Nervous System Overview

The nervous system is a complex network of specialized cells that transmit information throughout the body. It plays a crucial role in coordinating actions, thoughts, and sensations.

The nervous system is composed of two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).

The CNS consists of the brain and spinal cord, which serve as the command center, processing information and sending out commands.

The PNS comprises all nerves outside the CNS, responsible for connecting the CNS to the rest of the body, carrying sensory information to the brain and motor commands from the brain to muscles and glands.

The somatic nervous system controls voluntary movements of skeletal muscles, enabling purposeful actions like walking or writing.

The autonomic nervous system regulates involuntary functions like heart rate, digestion, and breathing, operating unconsciously to maintain bodily homeostasis.

The sympathetic nervous system is responsible for the 'fight-or-flight' response, preparing the body for action by increasing heart rate, breathing, and alertness.

The parasympathetic nervous system promotes 'rest and digest' functions, slowing down heart rate, promoting digestion, and enabling relaxation.

Neurons are specialized cells that transmit electrical impulses across the nervous system, enabling communication between different parts of the body.

The cell body of a neuron, also known as soma, contains the nucleus and most of the neuron's organelles, responsible for maintaining the cell's life functions.

Dendrites are branched extensions of the neuron's cell body that receive signals from other neurons, acting like the neuron's 'antennae'.

The axon is a long, slender extension of the neuron that carries signals away from the cell body, transmitting information to other neurons, muscles, or glands.

Myelin is a fatty substance that insulates the axon, speeding up the transmission of nerve impulses.

The nodes of Ranvier are gaps in the myelin sheath, allowing for faster signal transmission by jumping from node to node.

The axon terminal is the end of the axon, where the signal is transmitted to the next neuron or target cell.

A synapse is the junction between the axon terminal of one neuron and the dendrite or cell body of another neuron, where signals are transmitted.

Neurotransmitters are chemical messengers released from the axon terminal that cross the synaptic cleft and bind to receptors on the receiving neuron, influencing its activity.

Sensory neurons carry information from sensory receptors throughout the body to the CNS, conveying information about the environment and internal states.

Motor neurons carry information from the CNS to muscles and glands, initiating and controlling actions and responses.

Interneurons are neurons that connect and integrate information between different neurons within the CNS, forming complex neural circuits for information processing.

Glial cells are non-neuronal cells that provide support and protection for neurons, ensuring proper function and maintaining the health of the nervous system.

Astrocytes are star-shaped glial cells found in the CNS, responsible for providing structural support, regulating the chemical environment, and aiding in blood-brain barrier function.

Oligodendrocytes are glial cells found in the CNS that produce myelin, insulating axons and enhancing signal transmission speed.

Schwann cells are glial cells found in the PNS that produce myelin, similar to oligodendrocytes, but they wrap around individual axons.

Microglia are the immune cells of the CNS, responsible for removing debris, damaged cells, and pathogens, protecting the brain and spinal cord.

Ependymal cells line the cavities of the CNS, producing cerebrospinal fluid, which cushions and protects the brain and spinal cord, and helps transport nutrients and waste.

Satellite cells are glial cells in the PNS that surround and support neuron cell bodies in ganglia, providing a protective and nurturing environment.