Nerves and Receptors A2 Flashcards
what are the three main types of neurone
sensory, intermediate and motor
structures in a neuron
cell body, dendrites, axon, Shwann cells, myelin sheath and nodes of Ranvier
electrical impulses move from where to where
dendrite to axon
process of a reflex arc
stimulus, receptor, sensory neurone, intermediate neurone, effector
purpose of a reflex arc
allows rapid reaction
prevents damage to body tissues
doesn’t have to be learnt
how is resting potential maintained
sodium ions pumped out of axon by sodium potassium pump
3 sodium ions out for every 2 potassium ions in
membrane is more permeable to potassium
how is an axon depolarised
some potassium ions always open with K+ leaving axon by diffusion
voltage gated sodium ion channels are open
sodium enters axon by diffusion
axon gets +40mV charge
how does an axon become hyperpolarised
more sodium channels open sodium channels close more potassium channels open potassium ions leave channel by diffusion axon gets -85mV charge some potassium ion channels close
define refractory period
time during which a new action potential cannot be generated as the cell is in hyperpolarisation
why is the refractory period necessary
helps action potential pass in one direction and form discrete impulses
what is the all or nothing principle
if enough sodium ions enter cell and reaches threshold it will cause more sodium ion voltage gated channels to open
if not, no impulse
all action potentials are the same size
why does increased number of impulses cause oxygen consumption to increase
more respiration
for more ATP for active transport in sodium potassium pump
what receptor in skin and joint detects pressure
pacinian corpuscle
how do pressure receptors work
membrane layers surrounding the end of the neurone are distorted
stretch-mediated sodium channels open
sodium moves into neurone
if enough enter then charge reaches generator potential then action potential is passed along the sensory neurone
define unidirectional
synapses pass in only one direction
define synapses
gaps between neurones
why are synapses unidirectional
neurotransmitters are only stored in the presynaptic neurones and receptors only on post synaptic neurones
what neurotransmitter does cholinergic synapses use
acetylcholine
stages in synaptic transmission
action potential causes calcium ion channels to open and calcium ions to enter synaptic knob by diffusion
causes synaptic vesicles to fuse with presynaptic membrane and release neurotransmitter into synaptic cleft
this diffuses across synapse
binds with specific receptor sites on post synaptic neurone
opens either sodium (excitatory) or chloride (inhibitory) channels to increase or reduce action potential
define spatial summation
number of different presynaptic neurones together release enough neurotransmitter to exceed threshold value of postsynaptic neurone
define temporal summation
single presynaptic neurone releases neurotransmitter several times over a short period to exceed threshold value
what colours do rod cells see
black and white
what do cone cells see
colour
what does low visual acuity mean
several to each bipolar cell
what does high visual acuity mean
lots near fovea
each connects to single bipolar neurone
brain receives info from each cone cell individually
