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has organelles that provide structural support and energy, and manufacture needed materials (neurotransmitters)

cell body

olfactory

neurons do regenarate--research is focusing on triggers to activate stem cells

neurons

cannot divide--can't be replaced if damaged or killed

extensions of the cell body

dendrites and axons

usually only one

axon

axon

carries action potential away from the cell body

branches many times (hundreds or thousands) and end at the synaptic end bulb

axon

axon hillock

enlarged area of the cell body

extends from the axon hillock

axon

site where a neuron communicates with another cell

synapse

presynaptic cell and postsynaptic cell

two cells of the synapse

presynaptic cell

synaptic terminal; cell that sends a message--usually a neuron

postsynaptic cell

receives the message--almost any cell in the body

involves neurotransmitters released by the presynaptic cell that affect the postsynaptic cell

communication

stored in vesicles at the end of the axon and are released into the synaptic cleft

neurotransmitters (like ACH)

movement of materials between the cell body and the synaptic end bulbs

axoplasmic transport

flow from the cell body

anterograde

anterograde

neurotransmitters and other materials (like calcium) needed at the end of the axon

flow toward the cell body

retrograde

retrograde

waste products and debris

classified by structure and function

neuron

anaxonic, bipolar, unipolar, multipolar, sensory (afferent) neurons, motor (efferent), interneurons (association neurons)

classifications of neurons

small, all processes look alike

anaxonic

two processes: one dendrite and one axon with the cell body inbetween

bipolar

found in the brain and special sense organs (eyes, ears), but their function isn't clear

anaxonic

found in special sense organs

bipolar

unipolar

dendrite and axon are continuous and cell body is off to the side

sensory neurons in the peripheral nervous system

unipolar

multipolar

most common type of neuron in the central nervous system

has two or more dendrites and a single axon

multipolar

motor nerves that control skeletal muscles

multipolar

somatic, visceral, proprioceptors

sensory (afferent) neurons

sensory (afferent) neurons

deliver sensory information from the pns to the cns (about 10 million)

somatic

monitor the outside world (exteroceptors)

visceral

monitor the internal environment (interoceptors)

proprioceptors

monitor the body's position

carry instructions from the cns to the pns (about 500,000)

motor (efferent)

somatic and visceral

motor neurons

somatic motor neurons

innervate skeletal muscles

cell body lies in the cns and the axon extends to the target muscle

somatic motor neurons

innervate cardiac and smooth muscle as well as glands and organs

visceral motor neurons

provide communication between sensory and motor neurons ( 20 billion)

interneurons

interneurons

association neurons

most common type of neuron; found in the brain and spinal cord; involved in learning and memory

interneurons (association neurons)

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