L13 Flashcards
describe a multipolar neuron
multiple dendrites project from cell body
describe a bipolar neuron
single dendrite opposite from axon
describe a pseudo-unipolar neurone
axon and dendrite rise from a common stem of the cell body
what does it mean if a neuron has a large nucleus
large metabolic demand
what does many mitochondria in a neuron mean?
high metabolic demand
where can ER be found and in what kind of neurons?
found in dendrites of large neurons
what makes up the cytoskeleton of a neuron?
neurofilaments and microtubules
where are synapses found? 2
dendrites and cell body
what is the CNS split into?
white matter and grey matter
what is grey matter?
neuron cell bodies, dendrites and axons
what is white matter?
axons, many myelinated
what do glial cells do?
support the CNS
what is an oligodendrocyte equivalent to?
Schwann cell
what does an oligodendrocyte do in the CNS?
myelinates axons
what do astrocytes do?
provide mechanical support
What are astrocytes also a part of?
blood brain barrier
what are microglia?
specialised immunological cells of the CNS
what are ependymal cells?
ciliated cuboidal epithelial cells
where do you find ependymal cells?
lining the cavities of the brain and spinal cord
what 4 things do peripheral nerves consist of?
fascicle, endoneurium, perineurium and epineurium
what is a fascicle?
a bundle of nerve fibres
what is endoneurium?
a collagenous support tissue that surrounds axons inside the fascicles
what is perineurium?
a dense collagenous tissue surrounding indvidual fascicles
what is epineurium?
loose collagenous tissue surrounding bunch of fascicles/the nerve
what are PNS axons enveloped by?
Schwann cells
what do Schwann cells provide PNS axons?
structural and metabolic support
are axons with small diameter fibres myelinated?
no
are axons with large diameter fibres myelinated?
yes
when an axon is becoming myelinated, what is it first invaginated into?
the Schwann cell cytoplasm
what does the outer membrane of the Schwann cell fuse to form?
a mesaxon
what does the mesaxon do?
rotates around the axon, wrapping it in concentric layers of membrane
what does the wrapping of the membrane around the mesaxon form?
the myelin sheath
what are the gaps in between Schwann cells on an axon called?
Nodes of Ranvier
are these gaps also found in CNS in oligodendrocyte myelination?
yes
what exists across the plasma membrane of all cells?
an electrical potential
what kind of excess charge does the fluid inside the cell have?
negative
what kind of excess charge does the fluid outside the cell have?
positive
are myelinated or non-myelinated nerves slower to conduct AP’s?
non-myelinated
how do the Nodes of Ranvier increase conduction velocity?
the AP can jump quickly between the nodes
what are multiple sclerosis, Guillain-Barre syndrome and myasthenia gravis?
autoimmune diseases
what does the immune system attack if you have MS?
the myelin of CNS
what is the result of the attack on myelin of CNS if you have MS?
slows down or blocks messages between brain and body
what are 5 symptoms of MS?
visual disturbances, muscle weakness, trouble with coordination and balance, numbness (and pins and needles), thinking and memory problems
what does the immune system attack if you have GB syndrome?
myelin of PNS
what are 2 direct symptoms of GB syndrome?
tingling in hands and feet, progressing weakness of limbs and respiratory muscles
effects on autonomic nervous system can lead to what 2 symptoms if you have GB syndrome?
altered heart rate and blood pressure
what is a synapse?
a specialised intercellular junction which links neurones to each other and to muscles
where does the propagating axon terminate?
the terminal bouton
what does the AP from the propagating axon elicit release of?
neurotransmitter
where is neurotransmitter released from?
synaptic vesicles
where is neurotransmitter released into?
synaptic cleft
neurotransmitter diffuses across the synaptic cleft and stimulates what?
the receptor on the postsynaptic membrane
when neurotransmitter stimulates the postsynaptic cell, how does it respond?
usually an AP in the effector cell
what are the 5 neurotransmitters?
noradrenaline, glutamate, dopamine, acetyl-choline, serotonin
what are neurotransmitters synthesised by?
biochemical pathways
the loss of what enzyme leads to deficiency in several neurotransmitters?
GTP cyclohydrase 1
what 5 symptoms does GTPCH deficiency cause?
intellectual disability, convulsions, irritability, hypersalivation, difficulty breathing
how long does GTPCH deficiency take to onset?
4-5 months
what can you treat GTPCH deficiency with?
neurotransmitter precursors
what is a neuromuscular junction?
the synapse between motor neurons and muscle fibre
what is the neuromuscular junction also known as?
motor end plate
how many muscle fibres can one motor neuron innervate?
thousands
what is a motor unit?
a motor neuron and connected skeletal muscle fibres
in terms of athletic performance, what does more muscle fibres mean?
better at power movements
in terms of athletic performance, what does less muscle fibres mean?
better at endurance
what is the first step of neuromuscular activity?
acetylcholine is released from synaptic vesicles
in the second step of neuromuscular activity, what does the acetylcholine bind to and to cause what?
binds to nicotinic ion channels that cause sarcolemma membrane depolarisation
what are secondary synaptic clefts?
when the synaptic cleft folds to accept the neurotransmitter, between the folds are secondary synaptic clefts
what occurs in the third part of neuromuscular activity?
NMJ occupies a recess on the muscle surface
what is a sole plate?
a recess on the muscle surface
what are the stops of an AP’s activity?
acetylcholine is released in response to AP in motor neuron, binds to nicotinic receptors, then travels along the sarcolemma, into the t-tubule and into the sarcoplasmic reticulum
what does your body produce if you have myasthenia gravis?
antibodies to nicotinic receptors
what is blocked if you have myasthenia gravis and what does this inhibit?
binding of acetylcholine meaning muscle activation is inhibited
what are the most commonly affected muscles of myasthenia gravis?
eyes and face (those associated with swallowing)
what can alleviate symptoms of myasthenia gravis?
acetylcholinesterase inhibitors and immune suppressors
what is botox called?
botulinum toxin A
what does botox regulate?
ACh release from nerve terminals
what does botox selectively inhibit?
underlying muscles ability to contract
