Cells of the NS and neuromuscular joint

Question 1

name the 9 cells of the nervous system

Answer 1

neurones, pyramidal cells, purkinje cells, Golgi cells, oligodendrocytes, astrocytes, microglia, ependyma, Schwann cells

Question 2

name the 4 morphological types of neurones

Answer 2

unipolar, pseudopolar, bipolar, multipolar

Question 3

what are pyramidal cells

Answer 3

they have a pyramid shaped cell body

Question 4

what are purkinje cells

Answer 4

GABA neurones found in the cerebellum

Question 5

what are Golgi cells

Answer 5

GABA neurones found in the cerebellum

Question 6

what are GABA neurones

Answer 6

inhibitory neurotransmitter

Question 7

what are neurones

Answer 7

excitable cells of the CNS that are responsible for electrical transmission

Question 8

common features of cells

Answer 8

soma, axon, dendrites

Question 9

features of the soma/perikaryon

Answer 9

contains nucleus and ribosomes

also has neurofilaments for structure and transport

Question 10

features of the axon

Answer 10

a long process aka nerve fibre
originates from soma at axon hillock
can branch off into collaterals
usually covered in myelin

Question 11

features of dendrites

Answer 11

highly branched cell body
not covered in myelin
receives signals from other neurones

Question 12

what are oligodendrocytes

Answer 12

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

Question 13

what are astrocytes

Answer 13

the most abundant cell type
structural cells
cell repair, synapse formation, neuronal maturation and plasticity

Question 14

what are microglia

Answer 14

neuronal macrophages

immune function in CNS

Question 15

what are ependyma

Answer 15

epithelial cells lining the ventricles regulation movement/production of CSF

Question 16

what are Schwann cells

Answer 16

myelin production in PNS and only myelinates a single axonal segment

Question 17

what are the 4 main physiological ions and relate to cell membrane

Answer 17

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

Question 18

ion distribution in relation to extracellular space

Answer 18

high extracellular Na+ and Cl- (and also Ca2+ compared to inside)
low extracellular K+
high conc gradient for Ca2+

Question 19

what creates potential difference across membrane

Answer 19

the difference in ion concentrations

Question 20

RMP of neuronal cells

Answer 20

RMP between -40 and -90
negative charge inside compared to outside
charges are concentrated around membrane

Question 21

ions for generation of action potential

Answer 21

Na+ and K+

Question 22

STEPS for generation of AP

Answer 22

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

Question 23

STEPS for restoration of ion imbalance by Na/K ATPase

Answer 23

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

Question 24

normal AP conduction is..

Answer 24

through “cable transmission”

Question 25

what does myelin do

Answer 25

prevents the AP from spreading due to its | high resistance and low capacitance (stops AP travelling through) :. forced to go through nodes of ranvier

Question 26

what are nodes of Ranvier

Answer 26

small gaps of myelin along axon

Question 27

what is saltatory conduction

Answer 27

action potential jumping between nodes (AP cannot jump across gap at axon terminal)

Question 28

STEPS for neurotransmission at the synapse

Answer 28

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

Question 29

what is the communication between nerve cells

Answer 29

autocrine and paracrine

Question 30

3 types of synaptic organisation between neurones

Answer 30

axodendritic synapse (between terminal and dendrite) axosomatic (between terminal and soma) axoaxonic (between terminal and axon)

Question 31

what is the neuromuscular junction

Answer 31

a specialised structure incorporating axon terminal and muscle membrane (sarcoplasmic membrane/sarcolemma) allowing unidirectional chemical communication between peripheral nerve and muscle

Question 32

what type of communication exists between nerve and effector cells

Answer 32

paracrine - NT release

Question 33

STEPS for AP at neuromuscular junction

Answer 33

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)

Question 34

what is excitation-contraction coupling

Answer 34

sarcolemma is depolarised due to nACHR activation (opens Na+ channels) > depolarisation and AP > travels through T tubules to cause contraction

Question 35

what are T-tubules

Answer 35

continuous with the sarcolemma and are closely connected to sarcoplasmic reticulum connects to myofibrils causing contraction

Question 36

3 roles of sarcoplasmic reticulum

Answer 36

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

Question 37

disorder - what is botulism

Answer 37

botulinum toxin (BTx) : irreversible, disrupts vesicle binding and releasing ACh from presynaptic nerve terminal - no muscle contraction

Question 38

disorder - what is myasthenia gravis (MG)

Answer 38

type 2 hypersensitivity autoimmune disorder - antibodies directed against ACh receptor - degrading the receptor causes fatigable weakness

Question 39

disorder - what is Lambert-Eaton myasthenic syndrome (LEMS)

Answer 39

autoimmune disorder : antibodies directed against VG calcium channels - muscle degradation

Question 40

the hemispheres are separated into 4 distinct regions

Answer 40

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

Question 41

what does the brainstem contain (descending order)

Answer 41

midbrain pons medulla