5.1.3 Neuronal Communication Flashcards
what does the sensory neurone do
carry electrical messages from sensory receptors to CNS
what does motor neurone do
carry action potential from CNS to effector such as muscle/gland
what does relay neurone do
connect sensory and motor neurones - interneurones
what do interneurones do
carry info between other neurones only found in the brain and spinal cord
cell body
round, centrally located structure
contain DNA
controls protein manufacturing
directs metabolism
no role in neural signalling
dendrites
info collectors from CNS
recieve inputs from neighbouring neurones- relay
input may be thousands
dendritic growth
new dendrites can growth
provides room for more connections to other neurones
new connection are basis for learning
mature neurones generally can’t divide
axon
cells output structure
1 axon per cell - 2 distinct parts
tube-like structure branches at end that connect to dendrites of others
myelin sheath
act as electrical insulators
not present on all cells - presnt in motor and sensory neurones
made of schwann cells
schwann cells
type of lipid
which neurones can conduct impulses faster
myelinated neurones
where are chemoreceptors found
taste buds and aortic and cartoid bodies
what energy is detected by chemoreceptors
chemical stimuli in environment or blood
where are photoreceptors found
rods and cones in retina of eye
what energy is detected by photoreceptors
detect changes in light
where are thermoreceptors found
skin
hypothalmus
what energy is detected by thermoreceptors
changes in heat
where are mechanoreceptors found
touch and pressure receptors
inner ear
what energy is detected by mechanoreceptors
mechanical deformation of receptor cell membrane
where are nocioreceptors found
internal and external
what energy is detected by nocioreceptors
pain receptors
higher threshold for activate than do other receptors
need more intense stimulus required to activate
where are propioreceptors found
muscle spindles
golgi endon
joint receptors
what energy is detected by propioreceptors
sense of body position and allow fine control of skeletal movements
what does pacini corpuscle detect
pressure changes
examples of internal enviroment
blood glucose conc
internal temperature
water potential
cell pH
external enviroment
humidity
external temperature
light intensity
new or sudden sound
Depolarisation ion movenment
pottasium gates close
sodium gates open
sodium ions move into cell by diffusion
voltage gated sodium ions open
inside of neurone becomes less negative
Resting potential ion movenment
sodium poattasium pumps open
3 Na go out and 2 K ions go in
the inside of neurone is more negative charged
Repolarisation and hyperpolarisation ion movement
K+ move out of cell
K+ channels open
Na+ channels close
inside neurone is more negatively charged
Back to resting potential ion movenment
Na+ closed
K+ closed
sodium pottasium pump open
3 Na+ out
2K+ in
Action potential
occurs when a nerone sends info down an axon
when stimulated membrane potential is briefely depolarised
stimulus causes membrane at one part of neurone to increase in permeability to Na+
peak of action potential
once action potential of +40 mV has been estabilished the voltage gates on Na channel close
hyperpolarisation
slight overshoot in movement of K+ meaning that the inside of the axon is more negative than usual
gates on K+ channels now close
refraction period
time after each action potential
cell membrane can’t be stimulated to pass another signal as it takes time to recover from the last one
why do you need a refraction period
makes sure action potential is only transmitted in one direction
AP - Repolarisation
K+ rush out making inside cell more negative
synaptic cleft
the gap which seperates the axon of one neurone from the dendrite of the next neurone
approx. 20-30 nm across
presynaptic neurone
neurone along which the impulse has arrived
postsynaptic neurone
neurone that recieves the neurotransmitter
synaptic knob
swollen end of presynaptic neurone
contains many mitchondria and large amounts of endoplasmic reticulum to enable it to manufacture neurotransmitters
synaptic vesicles
vesicles containing neurotransmitters
vesicle fuse with presynaptic membrane and release their contents into synaptic cleft
neurotransmitter receptor
receptor molecules which the neurotransmitter binds to in the postsynaptic membrane
excitatory neurotranmitters
results in depolarisation of the postsynaptic neurone
if threshold is reached in postsynaptic membrane an action potential is triggered
inhibitory neurotransmitter
results in hyperpolarisation of
why does synaptic transmission occur
-action potential reaches end of the presynaptic neurone
-depolaristaion of the presynaptic neurone causes Ca2+ channels to open
-Ca2+ diffuse into presynaptic knob
-causes synaptic vesicles containing neurotransmitters to fuse with presynaptic membrane
-neurotransmitter is released into synaptic cleft by exocytosis
-neurotransmitter diffuses across synaptic cleft and binds to specific receptor molecule on postsynaptic membrane
-causes Na+ channels to open and Na+ to diffuse into postsynaptic neurone
-triggers action potential and impulse is propagated along postsynaptic neurone
what does a synapse act as
junctions
2nd step for synapse - neurotransmitter release
influx of Ca2+ cause synaptic vesicles to fuse with presynaptic membrane
releases neurotransmitter into cleft
Ca2+ cause release of neurotransmitter
3rd step for synapse - sodium channels
neurotransmitter released into synaptic cleft
moves across by diffusion
Acetylcholine binds to receptor site on Na+ channels
Na+ channels open
Na+ diffuse in
postsynaptic neurone depolarise
4th step for synapse - new action potential
depolarisation inside postsynaptic neurone must be above threshold value-55mV
if threshold reached a new action potential is sent along the axon of post synaptic neurone
5th step for synapse
hydrolytic enzyme acetylcholinesterase breaks acytylcholoine into acetyl(ethanoic acid) and choline
Na+ channels close
2 bits diffuseback across cleft into presynaptic neurone to allow neurotransmitter to be recycled
6th step for synapse
ATP released is used to recombine acetly and choline to recycle acetylcholine which is stored in synaptic vesicles
more acetylcholine can be made in SER
synapse is now ready to be used again
roles of synapses
ensure impulses are undirectional
allow impulses from one neurone to be transmitted to a number of different neurones at multiple synapses
number of neurones may lead in to same synapse with a single postsynaptic neurone
