L21- Structure and function of the nervous system Flashcards
NS can be divided into the
central and peripheral NS
CNS
brain stem and spinal cord
- has relay neurones- reflex
Peripheral NS
cranial and spinal nerves
- Somatic NS
- ANS

peripheral nervouss sytem contains
sensory and motor neurones
grey matter in the brain
found in the periphery in areas called nuclei
grey matter in the spinal cord (butterfly shaped)
central

grey matter consists of
Nerve cell bodies
Dendrites
Axon terminals
Non-myelinated axons
Neuroglia (support cells)
white matter found where in the brain
central
white matter found where in the spinal cord
the periphery
white matter consits of
myelinated axons
cross section of the human spinal cord (grey)
Grey matter- butterfly
- Anterior and posterior prongs are referred to as ventral horns (VH) and dorsal horns (DH_ respectively
- Connected by grey commissure (GC)

white matter in the spinal cord
white matter in the soinal cord contains
nerve fibres that form ascending and descending tracts
normal structure of a neurone
Normal set of cell organnels
Cytoplasmic projections- dendrites and a single axon

parts of neurone found within the CNS
- Cell body (soma)
- Dendrites
- Proximal part of the axons
parts of the neurone found within the PNS
Distal axon
Sometime coated with insulation (myelin)
Myelin in the CNS produced by
Oligodendrites
Myelin in the PNS produced by
Schwann cells
three types of neuroens
sensory
interneuron
motor neurone

sensory neurones
- Location: periphery towards CNS
- Function: send environmental signals to integrative centre
- Structure:
- Body sits to one side
- Sometimes body in the middle of the axon
integrative (interneurons)
- Location: CNS
- Function: collate all info
- Structure:
- Purkinje cells have a massive number of dendrites- allows a number of different inputs- just one or two signals out
- Pyramidal cells- body looks like pyramid- many dendrites- one axon
Anaxonic neurone
Location: Retina
Function: act as relays
majority of neuroens in the CNS are
interneurones- collate all infor
Unipolar, bipolar and postsynaptic autonomic neurone cell bodies are located
outside the CNS
multipolar neurones
One axon and multiple dendrites
Most common
Most neurones in the brain and spinal cord

biploar neurones
One axon and one dendrite
Olfactory cells, retina and inner ear

Unipolar neurones
- Single process leading away from the soma (body)
- Sensory from skin and organs to spinal cord

anaxonic neurone
Many dendrites but no axons
Help in visual processes
characteristics of neuroens int he CNS
Have lots of RER (protein synthesis)
Golgi (vesicles e.g. for NT)
Many free ribosome
Mitochondria, peroxisome and lysosomes found in axon hillock NISSAL bodies- RER and ribosomes
Majority of material go out through the zones

axon hillock
neck of the neurone
transport of vesicles from the soma to the axon terminals
Empty vesicles transported to the axons via intracellular neurofilaments (intermediate filaments)
- antegrade
- retrograde

antegrade
Assembly of kinesin- transport empty vesicle and mitochondria from the axon hillock to the distal end of the neurone via microtubules
retrograde
- Brings empty vesicles back
- Does not bring the mitochondria back
NT synthesis and vesicle transport
Immature vesicle contains only enzymes in its membrane.
- As it travels down the axon it starts to synthesise the NT
outlien movement of vesicles in neurones
- Synthesis of NT and formation of vesicle in the cell body
- Transport of NT down axon via microtubules using kinesin
- AP travels down the axon
- AP causes calcium to enter- evoking release of NT
- NT attaches to receptor, exciting or inhibiting postsynaptic neurone
- Separation of NT from receptor
- Reuptake of NT to be recycled
Vesicles have 2 fates:
1) recycled through clathrin-coated endocytosis
2) Lost to neuormolemma:
different types of synapses (5)
- axosomatic
- axodendritic
- axoaxonic
- dendro
- axo-axonal
axosomatic
Directly to the plasma membrane of nerve or cell

axodendritic
Axon terminal synapses with a dendritic spine
axoaxonic
Synapse at the axonic bouton
dendro-dendritic
dendritic dendron touching another dendron
Axo-axonal
impinging dendritic/ atonal synapse usually inhibits other inputs
the synapse and fusion of vesicles
SNARE complex and synaptotagmin (calcium dependent)
• Fuse vesicle (membrane) and create pore for NT to leave (porocytosis)

nerves bundle together to form
fibres- look like skeletal muscle
all 3 types of nevre fibres (motor, sensory and integrative) can be
present in peripheral nerves
- each are separated y connective tissue layers

endonuerium
loos connectiev tissue- surrounds single nerve cells

perineurium
- Specialised connective tissue- transport proteins
- Maintain ionic composition
- Surrounds clusters of axons (fascicles)
epineurium
- Around all the fascicles
- Dense irregular connective tissue
- Separates different types of nerves and fills spaces between fascicles
paraneurium
Fascia that separates nerves from surround structures
what stain is used to visualise neuroens and myelin
toluidine blue- stains fat e.g. myelin
myelination
Saltatory condcution faster in myelinated nerves
Conduction faster in large diameter axons
electrical conduction fastest in
A fibre- thickest
electrical conduction is intermediate in
B fibres- medium thickness
electrical conduction is slowest in
C fibres- thinnest
