Cells of the NS and neuromuscular joint Flashcards
name the 9 cells of the nervous system
neurones, pyramidal cells, purkinje cells, Golgi cells, oligodendrocytes, astrocytes, microglia, ependyma, Schwann cells
name the 4 morphological types of neurones
unipolar, pseudopolar, bipolar, multipolar
what are pyramidal cells
they have a pyramid shaped cell body
what are purkinje cells
GABA neurones found in the cerebellum
what are Golgi cells
GABA neurones found in the cerebellum
what are GABA neurones
inhibitory neurotransmitter
what are neurones
excitable cells of the CNS that are responsible for electrical transmission
common features of cells
soma, axon, dendrites
features of the soma/perikaryon
contains nucleus and ribosomes
also has neurofilaments for structure and transport
features of the axon
a long process aka nerve fibre
originates from soma at axon hillock
can branch off into collaterals
usually covered in myelin
features of dendrites
highly branched cell body
not covered in myelin
receives signals from other neurones
what are oligodendrocytes
glial cells
responsible for production of myelin in CNS
sends out numerous projections that form internodes of myelin covering axons of neurones
myelinates many axons
what are astrocytes
the most abundant cell type
structural cells
cell repair, synapse formation, neuronal maturation and plasticity
what are microglia
neuronal macrophages
immune function in CNS
what are ependyma
epithelial cells lining the ventricles regulation movement/production of CSF
what are Schwann cells
myelin production in PNS and only myelinates a single axonal segment
what are the 4 main physiological ions and relate to cell membrane
K+ Na+ Ca2+ Cl- cell membrane is impermeable to these ions so transportation is regulated by channels and pumps which causes an uneven ion distribution
ion distribution in relation to extracellular space
high extracellular Na+ and Cl- (and also Ca2+ compared to inside)
low extracellular K+
high conc gradient for Ca2+
what creates potential difference across membrane
the difference in ion concentrations
RMP of neuronal cells
RMP between -40 and -90
negative charge inside compared to outside
charges are concentrated around membrane
ions for generation of action potential
Na+ and K+
STEPS for generation of AP
at RMP
1) membrane depolarisation - opening of VGSC > Na+ influx > further depolarisation
2) VGKCs open at slower rate causing efflux of K+ from cell (membrane repolarisation)
3) ion imbalance needs to be restored by Na/K ATPase
STEPS for restoration of ion imbalance by Na/K ATPase
1) resting configuration - Na+ enters pump vestibule
2) pump is phosphorylated (by ATP) and ions are transported through protein extracellularly
3) active configuration - Na+ is removed from the cell and K+ enters vestibule
4) pump returns to resting configuration > K+ transported into cell
normal AP conduction is..
through “cable transmission”
what does myelin do
prevents the AP from spreading due to its
high resistance and low capacitance (stops AP travelling through) :. forced to go through nodes of ranvier
what are nodes of Ranvier
small gaps of myelin along axon
what is saltatory conduction
action potential jumping between nodes (AP cannot jump across gap at axon terminal)
STEPS for neurotransmission at the synapse
1) propagation of AP (depolarisation and repolarisation)
2) NT release from vesicles - AP opens VGCCs at the presynaptic terminal leading to a Ca2+ influx > vesicle exocytosis
3) activation of postsynaptic receptors - NT binds to receptors on post synaptic membrane which modulate postsynaptic activity
4) NT reuptake - NT dissociates from receptor and can either be metabolised by enzymes or recycled by transporter proteins
what is the communication between nerve cells
autocrine and paracrine
3 types of synaptic organisation between neurones
axodendritic synapse (between terminal and dendrite)
axosomatic (between terminal and soma)
axoaxonic (between terminal and axon)
what is the neuromuscular junction
a specialised structure incorporating axon terminal and muscle membrane (sarcoplasmic membrane/sarcolemma) allowing unidirectional chemical communication between peripheral nerve and muscle
what type of communication exists between nerve and effector cells
paracrine - NT release
STEPS for AP at neuromuscular junction
1) AP propagated along axon > Ca2+ entry at presynaptic terminal
2) ACh release into synapse
3) ACh binds to nAChR on skeletal muscle membrane > membrane depolarisation > change in EPP (depolarisation in membrane neuromuscular junction)
what is excitation-contraction coupling
sarcolemma is depolarised due to nACHR activation (opens Na+ channels) > depolarisation and AP > travels through T tubules to cause contraction
what are T-tubules
continuous with the sarcolemma and are closely connected to sarcoplasmic reticulum
connects to myofibrils causing contraction
3 roles of sarcoplasmic reticulum
location - surrounds myofibrils which are contractile units of muscle
function - Ca2+ storage - releases Ca2+ following sarcolemma depolarisation
effect - Ca2+ causes myofibril contraction and muscle contraction
disorder - what is botulism
botulinum toxin (BTx) : irreversible, disrupts vesicle binding and releasing ACh from presynaptic nerve terminal - no muscle contraction
disorder - what is myasthenia gravis (MG)
type 2 hypersensitivity
autoimmune disorder - antibodies directed against ACh receptor - degrading the receptor
causes fatigable weakness
disorder - what is Lambert-Eaton myasthenic syndrome (LEMS)
autoimmune disorder : antibodies directed against VG calcium channels - muscle degradation
the hemispheres are separated into 4 distinct regions
frontal lobe - personality
parietal lobe - somatosensory cortex > tactile info processing
temporal lobe - hippocampus (short term memory), the amygdala (behaviour) and Wernickes area (auditory perception and speech)
occipital lobe - processing of visual info
what does the brainstem contain (descending order)
midbrain
pons
medulla
