5.3-nerves (why is this hard) Flashcards
where is the cell body of a motor neurone found?
spinal cord or brain
what is a Dendron?
long projection that carries impulse towards a cell body
where are the cell bodies of sensory neurones found?
dorsal root ganglia, just outside the spinal cord
what produces myelin?
Schwann cells
what is salutatory conduction?
when the nerve impulses jump from node to node
what is the function of myelin?
speeds up nerve impulses
insulates neurone
why are not all nerves myelinated?
not necessary: short neurones, thick axons
where’s the myelin in non myelinated neurones and why?
neurones not individually wrapped but still associated with myelin, because it helps keep nerve alive and is involved in regeneration.
what is a fibroblast?
specialised tissue found in pacinian corpuscles
what is the axon hillock?
where the action potential will propagate from
what is an action potential?
a brief reversal of the potential across the membrane of the neurone.
what type of neurone has dendrites?
motor
relay
what type of neurone has a Dendron?
sensory
what are the channels like in a neurone at resting potential?
Na+/K+ pump going
Na+ channels closed
some K+ channels open
what are the channels like in a neurone when the stimulus is detected?
Na+ channels open
Na+/K+ pump still going
K+ channels closed
what are the channels like in a neurone during depolarisation?
Na+ channels open
voltage gated Na+ channels open
Na+/K+ pump still going
why is transmission of action potentials along the axon slower in the absence of saltatory conduction?
no nodes of ranvier
shorter local currents
whole axon needs to be depolarised
what is a pacinian corpuscle?
pressure sensor found in the skin
what is a transducer?
cell that converts one form of energy to another
which sensory receptors detect a change in light intensity?
rods and cones in retina
which sensory receptors detect a change in pressure on skin?
pacinian corpuscles
which sensory receptors detect movement?
hair cells in inner ear
which sensory receptors detect change in muscle length?
muscle spindles in skeletal muscle
which sensory receptors detect chemicals in the air?
olfactory cells in epithelium lining fo nose
what’s a pacinian corpuscle made of ?
series of concentric rings of connective tissue wrapped round the end of a nerve cell
what happens to the pacinian corpuscle when pressure on the skin changes?
rings of connective tissue get deformed-pushes against nerve ending-sodium channels open-generator potential
in the pacinian corpuscle what produces the connective tissue?
fibroblast
what is a generator potential also called?
receptor potential
what does it mean when a neurone is polarised?
negatively charged inside compared to outside
what is a generator potential?
change in potential across a receptor membrane
what are non myelinated neurones often used in?
coordinating body functions eg breathing and action of digestive system
what is an action potential?
brief reversal of the potential across the membrane of a neurone
whats the voltage of a neurone during an action potential?
+40mV
whats the resting potential of a neurone?
-60-70 mV
why are action potentials referred to as an all or nothing response?
all action potential are the same magnitude-the strength of stimulus is transmitted as more frequent action potentials, not bigger ones.
what are the brief stages of an action potential?
resting
Na+ channels open-Na+ goes into cell
membrane depolarises-reaches threshold of -50mV
voltage gated Na+ open-loads of Na+ go in-reaches +40mV
Na+ close, K+ open-K+ diffuse out bringing pd back to negative-repolarisation
hyperpolarisation then resting
what is the refractory period?
a short time where after the action potential it’s impossible to get another one-allows cell to recover, ensures APs only transmitted 1 direction
why does the action potential continue to move in the same direction during transmission?
conc of Na+behind AP still high
what is a cholinergic synapse?
synapse that uses acetylcholine as its neurotransmitter
what is a neurotransmitter?
chemical used as signalling molecule between 2 neurones in a synapse
what is a synapse?
a junction between 2 or more neurones
what is between the 2 neurones in a synapse?
synaptic cleft
the pre synaptic neurone ends in a…
swelling called the pre-synaptic bulb or knob
what are the specialised features of the pre synaptic bulb?
many mitochondria
lots of SER
lots of vesicles
Ca2+ channels on surface membrane
why does the pre synaptic bulb have loads of SER?
it packages the neurotransmitter into vesicles
what does the post synaptic membrane contain?
specialised Na+ channels that respond to neurotransmitter
what happens to the Na+ channels on the post synaptic membrane when neurotransmitter is present?
neurotransmitter binds to 2 receptor sites on Na+ channels-they open
what reaction does acetylcholinesterase catalyse?
acetylcholine–> ethanoic (acetic) acid + choline
what happens to the ethanoic (acetic) acid + choline after they’ve gotten made?
recycled-enter synaptic bulb by diffusion+made back into acetylcholine using ATP fro mitochondria.
when does summation occur?
when the effects of several EPSPs are added together
what’s the difference between temporal and spatial summation?
temporal: all from same pre synaptic neurone
spatial: from different ones
what do IPSPs do?
reduce effect of summation+prevent action potential in post synaptic neurone
what is an EPSP?
excitatory post synaptic potential-small post synaptic potential that makes neurone more likely to fire action potential
what is an IPSP?
inhibitory post synaptic potential-synaptic potential that makes post-synaptic neurone less likely to generate an action potential, neurotransmitters may bind to post synaptic membrane + close ion channels.
when could spatial summation be useful?
when several different stimuli are warning of danger
when is 1 pre synaptic leading to many post synaptic neurones useful?
reflex arc-one yeets and does the reflex the other informs the brain
if a low level stimulus creates an action potential in the pre synaptic neurone why is it unlikely to pass through the synapse to the next neurone?
several vesicles of neurotransmitter must be released to create action potential in post synaptic neurone
after repeated stimulation what might happen to a synapse?
may run out of vesicles containing neurotransmitter-synapse said to be fatigued
what happens when we become habituated to something?
nervous system no longer responds to the stimulus
what is a direct effect of the neurotransmitter binding to the receptor on the post synaptic neurone?
Na+ travels through postsynaptic membrane.
