Structure and Function of the Mammalian Nervous System

Structure of the Nervous System

The mammalian nervous system comprises two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).
The CNS includes the brain and spinal cord. The brain is the control centre of the body, while the spinal cord acts as a communication link between the brain and other body parts.
The PNS is further divided into sensory (afferent) and motor (efferent) neurons. Sensory neurons transfer information from sensory receptors to the CNS, while motor neurons transmit signals from the CNS to effectors like muscles or glands.
The PNS further branches into the somatic nervous system, controlling voluntary actions, and the autonomic nervous system, controlling involuntary actions.
The autonomic nervous system is again subdivided into the sympathetic and parasympathetic systems, which often work antagonistically to maintain homeostasis.

Neurones and Neurotransmitters

Neurones are the fundamental units of the nervous system. They consist of a cell body, an axon and numerous dendrites.
Myelin sheaths, made by Schwann cells, insulate the axon and allow the rapid propagation of nerve impulses along the neuron.
Communication between neurons occurs at junctions called synapses via neurotransmitters, chemicals which transfer an impulse from one neuron to another.
Common neurotransmitters include acetylcholine, dopamine, and serotonin. Imbalances in neurotransmitters can affect mood and cause conditions like depression.

Function of the Nervous System

The primary function of the nervous system is to receive sensory input, process and integrate information, and coordinate output to muscles or glands.
Information from the environment is received by receptor cells and transmitted as nerve impulses along sensory neurones to the CNS.
The CNS processes this input, deciding the necessary action and response. This decision-making process is known as integration.
The CNS then sends instructions via the motor neurones to the effectors (muscle or glands), which perform the appropriate response.

Reflex Arcs

A reflex arc is a rapid, automatic response to a stimulus, bypassing the brain to prevent delay. It involves a sensory neurone, a relay neurone in the spinal cord, and a motor neurone.
Reflex arcs are crucial for survival as they enable quick responses to potentially harmful stimuli.

Understanding how these components interact with each other and their direct effects on the body is vital for understanding neural control in mammals.