Introduction to the Nervous System

Central nervous system (CNS) functions

Gather and process information form the peripheral nervous system

execute and coordinate voluntary movements

subcnoncious regulation of internal environment

• heart rate, blood pressure

• digestion

• metabolism

• reproductive function

Peripheral nervous system (PNS) functions

Carries information between the CNS and body tissues

Afferent vs Efferent division

Afferent: carries info towards the CNS

Efferent: carries info away from the CNS

Neurons

Specialised cells that receive and transmit electrical impulses.

• Cell body (soma)

• Dendrites

• Axon

• Synaptic terminals, synapses

Cell b

Dendrites

Elongated branched extensions that receive signals and carry them towards the cell body.

Axon

A single elongated, tubular extension that conducts impulses away from the cell body.

Nerve fibre

The elongated projection of a neuron, usually the axon.

Nerves

Individual nerve fibres bundled together with blood vessels and connective tissue.

Myelin

A fatty sheath wrapped around axons that acts as an electrical insulator.

Oligodendrocytes

Glial cells that form the myelin sheath around CNS axons.

Schwann cells

Glial cells that myelinate axons in the peripheral nervous system.

Neuron classification (three ways)

Classified by function, structure (number of projections), and neurotransmitter produced.

Afferent neurons

Transmit information towards the central nervous system.

Efferent neurons

Transmit information away from the central nervous system.

Interneurons

Connect motor and sensory neurons within the central nervous system.

Neuroglial cells

Non-excitable supporting cells of the CNS that provide physical and metabolic support.

Astrocytes

Abundant glial cells that provide structural support and aid in blood-brain barrier formation.

Microglia

Immune cells and phagocytic cells of the CNS.

Ependymal cells

Line internal cavities of the CNS and help form and circulate cerebrospinal fluid.

Spinal reflex arc components

Receptor, sensory neuron, integration center, motor neuron, and effector tissue.

Spinal reflex arc sequence

Receptor -> sensory neuron -> integration center -> motor neuron -> effector tissue.

Blood-brain barrier (BBB) function

Regulates substance entry, excludes toxins, and maintains a constant environment for the brain.

Blood-brain barrier (BBB) structure

Endothelial cells with tight junctions, surrounded by basal lamina, pericytes, and astrocyte end-feet.