Functional Organization of the Nervous System

Nervous communication

A body system that performs electrical communication via action potentials ($APs$).

Endocrine communication

A body system that performs chemical communication via hormones.

Sensory function

The detection of stimuli, which can be external (outside the body) or internal (inside the body).

Integration

A function of the $CNS$ that involves processing and interpreting sensory input to decide if action is needed.

Motor function

The activation of effector organs, such as muscles (skeletal, cardiac, or smooth) or glands, to respond to stimuli.

Central Nervous System (CNS)

Composed of the brain and spinal cord; it interprets sensory input and determines responses.

Peripheral Nervous System (PNS)

Made of nervous tissue outside the $CNS$, including spinal nerves, cranial nerves, and sensory receptors.

Sensory (afferent) division

The part of the $PNS$ that takes information from sensory receptors to the $CNS$.

Motor (efferent) division

The part of the $PNS$ that takes information from the $CNS$ to effector organs.

Somatic Nervous System (SNS)

A voluntary part of the motor division that controls skeletal muscles.

Autonomic Nervous System (ANS)

An involuntary part of the motor division that controls smooth muscle, cardiac muscle, and glands.

Sympathetic branch

A branch of the $ANS$ associated with the "flight or fight" response.

Parasympathetic branch

A branch of the $ANS$ associated with "resting and digesting."

Action potential (AP)

The term for the voltage changes occurring across the membrane of a nerve cell.

Nerve impulse

Refers to the movement of an action potential along the axon of the nerve cell.

Neurons

Nerve cells that generate $APs$, conduct impulses, and secrete neurotransmitters at the terminal end.

Neuroglia

Also called glia or glial cells; these are supporting cells that do not generate $APs$ and can reproduce.

Nissl body

The specific name for rough endoplasmic reticulum ($ER$) in neurons, reflecting high metabolic activity and protein synthesis.

Cell body (soma)

The central part of a neuron containing the nucleus and organelles; it acts as the control center where integration occurs.

Nuclei

Clusters of neuron cell bodies found within the Central Nervous System ($CNS$).

Ganglia

Clusters of neuron cell bodies found within the Peripheral Nervous System ($PNS$).

Processes

Also called nerve fibers; these project from the cell body to send information to and from the neuron.

Tracts

Bundles of neuron processes found within the Central Nervous System ($CNS$).

Nerves

Bundles of neuron processes found within the Peripheral Nervous System ($PNS$).

Dendrite

A short, branched process that receives information in the form of graded potentials and sends it toward the cell body.

Axon

The single, long sending end of a neuron that generates $APs$ and conducts impulses away from the cell body.

Axon hillock

The anatomical junction where the axon and cell body meet; functionally, it is where the $AP$ is generated.

Terminal arborization

Also called terminal branches or presynaptic terminals; these are the branches at the end of an axon.

Synaptic bulb

A knob at the end of each terminal branch that stores neurotransmitters.

Astrocytes

The most abundant $CNS$ glial cells; they form the blood-brain barrier, provide nutrients, and remove excess neurotransmitters.

Oligodendrites

Glial cells in the $CNS$ responsible for producing the myelin sheath.

Microglia

$CNS$ glial cells that act as macrophages to remove microbes and debris at injury sites.

Ependymal cells

$CNS$ glial cells that line cavities and produce and circulate cerebrospinal fluid ($CSF$).

Satellite cells

$PNS$ glial cells that function to protect cell bodies (ganglia).

Schwann cells

$PNS$ glial cells responsible for producing the myelin sheath.

Myelin sheath

A coat covering the axon made of $$80 ext