Nervous System: Communication and Control

Study Notes

The nervous system is one of the body's two primary communication systems, the other being the endocrine system.
The nervous system is responsible for rapid communication, triggering immediate responses.
The endocrine system controls slower, hormonal changes.
The nervous system controls all bodily functions, including voluntary and involuntary actions like breathing, walking, and thinking.

Sensing: Gathers information from inside the body and the environment through sensory neurons.
Integration: Processes and interprets information in the central nervous system (CNS). It uses past experiences to determine responses.
Motor Function: Sends messages from the CNS to muscles and glands through motor neurons.

Central Nervous System (CNS): Consists of the brain and spinal cord. Integrates sensory information and directs motor responses.
Peripheral Nervous System (PNS): Comprises nerves outside the CNS. Acts as a communication pathway between the CNS and the rest of the body, further divided into the somatic and autonomic systems

Somatic System: Controls voluntary movements and responses to external stimuli like touch, temperature, and pain.
Autonomic System: Controls involuntary functions such as heart rate, smooth muscle activity, and gland activity. This system is further divided into sympathetic and parasympathetic systems based on environmental demands.

Sympathetic System: Prepares the body for intense physical activity by increasing heart rate, blood flow to muscles, and energy release while reducing non-essential functions like digestion. This is known as the "fight or flight" response.
Parasympathetic System: Returns the body to a resting state by promoting functions like digestion, energy storage, and waste elimination. This is known as the "rest and digest" response.

Enteric Nervous System: Operates independently within the gastrointestinal tract to control peristalsis (muscle contractions in the digestive system) and secretion of digestive enzymes without needing input from the CNS.

Neurons: Electrically excitable cells that send and receive electrical impulses.
Glial cells: Support and protect neurons. There are more glial cells than neurons.
Sensory neurons: Respond to stimuli such as touch and sound.
Motor neurons: Control muscles and glands.
Relay neurons: Connect neurons within the CNS.

Dendrites: Receive information and transmit signals to the cell body (soma).
Soma: Contains the nucleus (containing DNA) and stores nutrients. It acts as a factory for the neuron.
Axon: Transmits electrical signals to other neurons.
Myelination: Schwann cells in the peripheral nervous system (PNS) produce myelin sheaths which insulate the axon and increase the speed of nerve signals.
Nodes of Ranvier: Unmyelinated gaps in the axon that help signals jump quickly along the axon through saltatory conduction.
Axon Terminals: Form connections (synapses) with the dendrites of other neurons allowing communication between nerve cells.