neurons

neurons have

unidirectional flow of information

the nervous system

is the main controlling and communicating centre of the body

coordinates and controls all bodily functions

processes information from environment and enables body to respond accordingly

3 parts of axon

axon hillock

axolemma

axoplasm

nucleolus is post mitotic → diffused chromatin in neurons allows for

transcription

neuronal cytoskeleton composed of

microtubules

neurofilaments

microfilaments

microtubules have

alpha and beta tubulin dimers → transport within the neuron

neurofilaments have

coiled-coil fibres → structural maintenance

microfilaments have

actin dimers → structural movement of cargo

kinesins are

slower than dyneins

many axons are myelinated by

glial cells

multiple sclerosis

when immune system attacks myelin sheath of nerves in brain and spinal cord

myelination speeds up

nerve conduction

saltatory conduction

coverings of peripheral nerves

endoneurium

perineurium

epineurium

endoneurium

delicate connective tissue layer surrounding axon and schwann cells

perineurium

connective tissue layer surrounding groups of axons forming fascicles

epineurium

robust connective tissue layer surrounding individual fascicles, contains blood vessels

nissl staining

basic dyes i.e. cresyl violet → stains cell body

nissl substance

rER

chromatolysis

dissolution of nissl substance

functional classification of neurons

sensory/afferent neurons

motor/efferent neurons

interneurons

structural classification of neurons

multipolar

bipolar

(pseudo)unipolar

example of multipolar neuron

motor neuron in spinal cord

example of bipolar neuron

cells in retina

example of pseudo unipolar

primary somatosensory neuron in the dorsal root ganglion

neurons connect via

synapses

two types of synapses

electrical

chemical

synapses can be

axo-dendritic

axo-somatic

axo-axonic

axo-dendritic

terminal synapses onto dendrites

axo-somatic

terminal synapses onto cell body

axo-axonic

terminal synapses onto axon

neurons can only make a binary decision

to fire an action potential or not (all or nothing)

convergence

when one neuron receives multiple inputs from many other neurons

divergence

when one neuron sends out and synapses with many other neurons

5 types of nervous system disorders

• vascular disorders e.g. stroke

• infections e.g. meningitis

• structural disorders e.g. bell’s palsy, brain and spinal cord tumors

• functional disorders e.g. epilepsy

• degeneration e.g. Parkinson’s, Huntington’s, Alzheimer’s

treatment for parkinson’s symptoms

Levodopa - precursor to dopamine

Carbidopa - given with levodopa so cells outside brain do not use levodopa and more gets to the brain

MAO-B inhibitors - less dopamine breakdown