C2.2 Neural Signalling Flashcards
Features of nervous system (4)
central nervous system - brain + spinal cord protected by bone
receives + processes bodily information + activity
composed of neurons that carry electrical impulses
peripheral nervous system - non-CNS nerves - connects CNS to organs, muscles, sensors
Structure of a neuron (4)
cell body/soma
dendrites (one or more)
long axons
axon terminal (synaptic) knobs
Features of the cell body/soma for neurons (2)
nucleus + cytoplasm
neurons do not multiply - have no centrioles
Features of dendrites for neurons (2)
short + branched nerve fibers from cell surface
make connection with other neurons - have increased SA
Features of the axon hillock in neurons (2)
connects cell body to axon
site where action potential generated
Features of the axon for neurons (2)
long single fibre away from cell body
covered by Schwann cells/a myelin sheath
Features of axon terminal (synaptic) knobs
axon terminal (synaptic) knobs - end of nerve where impulse leaves
3 Types of neurons
Sensory neurons
Motor Neurons
Relay Neurons
Define sensory neurons (2)
long axons
transmits nerve impulses from sensory receptors to CNS
Define motor neurons
long axons
transmit nerve impulses from CNS to effectors
Define Relay neurons
smaller cells with more interconnections
Define resting potential of a neuron (4)
membrane potential when a neuron is not transmitting a signal
more Na+ outside, more K+ inside
potential difference - voltage is at -70 mV
sodium-potassium pump - pumps 3 Na+ out and 2 K+ in
channels - K+ ions flow out at faster rate than Na+ ions flow in
Features of sodium-potassium pump (2)
uses ATP
3 Na+ pumped out, 2K+ pumped in
Role of Sodium Potassium Pump for maintaining resting potential for Na+ ions (4)
few Na+ channels –> Na+ ions diffuse at slower rate
no pump –> more Na+ ions will enter cell due to diffusion
more Na+ ions –> more positive = depolarisation
pump - actively removes Na+ ions
Role of Sodium-Potassium pump for maintaining resting potential for K+ ions (4)
diffusion - K+ ions will leave cell (more inside)
electropotential gradient - K+ ions will re-enter (because insides is more negative from diffusion)
diffusion force > electropotential gradient (gradient charge less negative hence weaker)
pump - pumps K+ ions in to maintain resting potential
Factors which impact speed of nerve impulse (3)
amount of myelinaton
diameter of axon
temperature
Myelinated neurons as a factor which impacts speed
prevents leakage of neurons into the axon
Diameter of axons as a factor which impacts speed
wider surface area
for charges to hop from sections in resting potential
Temperature as a factor which impacts neuron speed
myelination
action potential hop between gaps of myelin sheath
called nodes of ranvier
Pre-synaptic neuron (2)
carries impulse towards synapse
“sender”
Post-synaptic neuron (2)
carries impulse away from synapse
receiver
Synaptic transmission (3)
neurotransmitter binds to neuroreceptors in post-synaptic membrane
ligand-gated sodium channels open - sodium ions flow in
creates depolarisation - may initiate action potentials if threshold reached
Break-down of neurotransmitters in synaptic transmission
specific enzyme breaks down neurotransmitter
broken-down products reabsorbed by the pre-synaptic neuron
Acetylcholine (2)
nuerotransmitter that triggers muscle contraction
promotes parasympathetic responses (relaxing body after stress)
How is acetylcholine made
made in axon terminal
combines chlorine with acetate group from Acetyl CoA
Where acetylcholine is made (3)
stored in vesicles in axon terminal
performs exocytosis in response to nerve impulse
activates post-synaptic cell by binding to specific receptor
Breakdown of Acetylcholine (4)
must be continually removed from synapse - may lead to fatal convulsions + paralysis
broken down by enzyme acetylcholinesterase (AChE)
enzyme released into presynaptic neuron
or embedded onto membrane of post-synaptic neuron
Neuromuscular Junction (4)
specialised synapse between motor neuron + muscle fiber
motor neuron releases acetylcholine
binds to receptors on plasma membrane of muscle fiber –> initiates muscle contraction
causes depolarisation of muscle membrane + release of calcium
Neuroglandular junction (2)
synapses between neurons + glandular cells
regulate secretory activities
Excitatory synapses (2)
depolarises the local membrane potential of post-synaptic cell
makes cell more prone to firing
Inhibitory synapses (2)
hyperpolarises (more negative) the local membrane potential of postsynaptic cell
less prone to firing
Explain repolarisation (3)
voltage gated sodium- ion channels close
voltage-gated potassium ion channles open when 40+ reached
K+ ions rush out of cell –> membrane is repolarised then hyperpolarised
Factors which determine strength of action potential (2)
amount of neurotransmitter released –> more neurotransmitter = more channels open
time neurotransmitter is in area
Explain excitatory postsynaptic potential (4)
opening of channels –> leads to depolarisation + increases chances of action potential happening
inside of post-synaptic cell becomes less negative
Na+ channels (come in)
Ca2+ comes in
Explain inhibitory postsynaptic potential (5)
opening of ion channels –> leads to hyperpoarisation
makes action potential less likely
inside of psot-synaptic cell becomes more negative
influx of Cl-
efflux of K+
