Anatomy - Nerve

neurons

regeneration, nerve impulses to target organs

neurological cells

maintain homeostasis, provide support and protection

neuron consists of:

cell body

axon conducting nerve impulses

dendrites receive stimuli

anaxonic

axon cannot be distinguished from dendrites

bipolar

axon and single dendrite opposite ends

unipolar

dendrite and axon emerge from same process, sensory neuron

multipolar

2 or more dendrites separate from axon, motor neuron

neuron cell body

produces all proteins

nissl bodies - combination of free ribosomes and RER

neuropil - mass of interwoven nerve endings and dendrites from other neurons

axon hillock - domain of neuronal cell body from which the axon originates

axon

primary transmission lines

neurotubules - conveyor belts to transport

neurofilaments - provide strcutural support

myelinated axons

allow faster transmission of nerve signals

myelination steps

1. schwann cell begins to wrap around portion of axon.

2. this forms consecutive layers around axon.

3. overlapping inner layers form sheath.

4. schwann cell cytoplasm and nucleus are pushed to the periphery.

connective tissue in peripheral nerves

individual axon - endoneurium

nerve fascicle - perineurium

nerve - epineurium

CNS - oligodendrocyte

1 will form myelin sheath for several axons

CNS - astrocytes

fibrous (white) and protoplasmic (grey) - blood brain barrier and restraint of spread of electrical disturbance

CNS - ependymal cells

lines cavities

CNS - microglia

when activated become macrophage cells and antigen presenting cells

PNS - schwann cells

increase impulse

PNS - satellite cells

enclose each perikaryon and regulate microenvironment

neuronal endings

synapse - neuron to neuron

motor end plate - neuromuscular junction

muscle spindle - muscle fibre to muscle fibre

sensory endings - signal back to CNS for processing

synapses

regions at axons transporting impulse from one neuron to another. can be chemical or electrical

motor end plates

axon loses myelination and forms dilated termination - neuromuscular bulb

forms chemical synapse between motor neuron and muscle fibre

botulinum toxin (botox)

produced by bacterium clostridium botulinum which blocks acetylcholine releases