In the CNS, star shaped, largest and most numerous type of glia, connect to both neurons and capillaries, transfer nutrient from the blood to the neurons

Microglia

In CNS small usually stationary cells found in inflamed brain tissue, they enlarge and move about. they cary on phagocytes

Ependymal

In CNS, resemble epithelial cells and form thin sheets that line fluid filled cavities in the CNS, some produce fluid and other aid in circulation of fluid

Oligodendrocytes

In CNS, smaller than astrocytes with fewer processes, hold nerve fibres together and produce the myelin sheath

Schawn cells

In PNS, found only in peripheral neurons, support nerve fibres and form myelin sheaths

Myelin sheath

These gaps are often called nodes of ranvier

Neurilemma

Ormed by the cytoplasm of the Schwann cells, wrapped around the myelin sheath, essential fro nerve regrowth

Satellite cells

They are Schwann cells that cover and support cell bodies in the PNS

Neurons

Excitable cells that imitate and conduct impulses that make possible all nervous system functions

Components of neurons

Cell body, ribosomes, rough endoplasmic reticulum, Golgi apparatus

Ribosomes, rough ER and golgi

Provide protein molecules needed for transmission of nerve signals from one neurone to another, neurotransmitters are packaged into vesicles, provide proteins for maintaining and regenerating nerve fibres

Mitochondria

Provide energy (ATP) for neurone, and some are transported to end of an axon

Dendrites

Conduct nerve signals to the cell body of the neuron

Axon

A single process extending form the axon hillock, sometimes covered by a fatty layer called a myelin sheath, conducts nerve impulses away from the cell body of the neuron, distal tips of axons are telodendria

Input zone

Dendrites and cell body

Summation zone

Axon hillock

Conduction zone

Axon

Output zone

Telodendria and synaptic knobs of axon

Multipolar

One axon and several dendrites

Bipolar

Only on axon and one dendrite, least numerous kind of neuron

Unipolar (pseudo unipolar)

One process come off neuron cell body, but divides almost immediately into two fibres central fibre and peripheral fiber

Afferent neurons

Conduct impulses to spinal cord or brain

Efferent neurons

Conduct impulses away from spinal cord or brain toward muscles or glandular tissue

Reflex arc

A signal conduction route to and from the CNS with the electrical signal beginning in receptors and ending in effectors

Three neuron arc

Most common, consists of afferent neurons, interneurons and efferent neurons

Synapse

When nerve signals are transmitted from one neuron to another

Chemical synapse

Located at the junction of the synaptic knob of one neuron and the dendrites or cell body of another neuron

Nerves

Bundles of peripheral nerve fibres held together by several layers of connective tissues

Endonurium

Delicate layer of fibrous connective tissue surrounding each nerve fibre

Perineurium

Connective tissue holding together fascicles (bundles of fibers)

Epineurium

Fibrous coat surrounding numerous fascicles and blood vessels to form a complete nerve

E tracts

Bundles of nerve fibres within the CNS, unlike nerves, tracts do not have connective tissue coverings

White mater- PNS

Myelinated nerves

White mater- CNS

Myelinated tracts

Egrey matter

Made up of cells bodies and unmyleinated fibres

Grey mater- CNS

Referred to as nuclei

Grey matter-PNS

Referred to as ganglia

Mixed nerves

Contain sensory and motor neurons

Sensory nerves

Nerves with predominantly sensory neurons

Motor nerves

Nerves with predominantly motor neurons

Membrane potentials

Slight excess of positively charged ions on the outside of the membrane and slight deficiency of positively charged ions on the inside of the membrane

Nerve impulse- potential

Difference in electrical charge

Polarized membrane

A membrane that exhibits a membrane potential

Resting membrane potential

The membrane’s selective permeability characteristics help maintain a slight excess of positive ions on the outer surface of the membrane

Sodium potassium pump

Active transport mechanism in plasma membrane that transports Na+ and K+ in opposite directions and at different rates

Local potentials

Slight shift away from the resting membrane in a specific region of the plans membrane

Excitation

When a stimulus triggers the opening of additional Na+ channels, allowing the membrane potential to move toward 0 (depolarization)

Inhibition

When a stimulus triggers the opening of additional K+ channels, increasing the membrane potential (hyperpolarization)

Graded potentials

The magnitude of deviation form the resting membrane potential is proportional to the magnitude of the stimulus

Action potential

The membrane potential of a neuron the tis conducting an impulse, also known as nerve impulse

Absolute refractor period

Brief period during which a local area of a neurons membrane resists re stimulation and will not respond to a stimulus, no matter how strong

Relative refractory period

Time during which the membrane is depolarized and restoring the resting membrane potential, the few milliseconds after the absolute refractor person, will respond to ONLY a very strong stimulus

Electric synapses

The cells join dby gap junctions allow an action potential to simply contrite along postsynaptic membrane

Chemical synapses

Presynaptic cells release chemical transmitters across a tiny gap to the postsynpatical cell possibly inducing an action potential there

Synaptic knob

Tiny bulge at the end of a terminal branch of a presynaptic neurons axon that contains vesicles housing neurotransmitters

Synaptic cleft

Space between a synaptic knob and the plasma membrane of a postsynaptic neuron

Axodendrite

Axon signals postsynaptic dendrite, they are common

Axiomatic

Axon signals postsynaptic soma, they are common

Axoaxonic

Axon signals postsynaptic axon, may regulate action potentials of postsynaptic axon

Plasma

Membrane of a postsynaptic neuron, has protein molecules that serve s receptors for the neurotransmitters

Acetylcholine

Small molecule neurotransmitter, present at various locations, sometimes in an excitatory role; other times, inhibitory

Amines

Synthesized from amino acid molecules, found in various regions of the brain, affecting learning, emotions, motor control

Amino acids

The most common neurotransmitters of the CNS, in the PNS amino aids are stored in synaptic vesicles and used in neurotransmitters

Neuropeptides

Short strands of amino acids called polypeptides, they have regulatory effects in the digestive tract and act as neurotransmitters in the brain

Sensory neurons

Act as receptors to detect changes in the internal and external environment; relay information to integrator mechanisms in the CNS,