topic 5.1.3: neuronal communication Flashcards
what is a transducer?
converts one form of energy into another ie in receptors they convert stimulus energy into nervous impulse
outline the 4 types of receptors
photoreceptors (light)
chemoreceptors (chemicals)
mechanoreceptors (pressure and movement)
thermoreceptors (temperature)
outline how receptor cells function
- differing ion concs cause voltage (resting potential)
- stimulus makes membrane more permeable
- ions cause voltage to change (generator potential)
- if GP reaches threshold level, action potential is triggered (signal sent down neuron)
describe the structure of a Pascinian corpuscle
end of sensory neuron wrapped in lamellae which detect pressure changes
outline what happens when a Pascinian corpuscle is stimulated
lamellae deform, pressure on neurone ending, neurone memb deforms, more ions let in, voltage changes and action potential triggered
describe the structure and function of a sensory neurone
one dendron with dendrites, one axon
receptors –> CNS
describe the structure and function of a relay neurone
lots of short dendrons and axons
impulses around CNS
describe the structure and function of a motor neurone
lots of dendrites, one long axon
CNS –> effectors
describe the structure and function of a Schwann cell
wraps around axon, memb forms myelin sheath
insulator that prevents the passage of ions in or out of the axon
how do impulses travel through myelinated axons?
impulse jumps between gaps (nodes of Ranvier) in sheath to increase the speed
describe the structure of a non-myelinated axon
Schwann cells loosely contains a few neurones- action potential moves in a wave
what are the 3 types of receptors?
photo, thermo, mechano
what does transducer mean?
receptors convert energy to electrical impulses
describe the function and structure of a pacinian corpuscle
-formed by rings of lamellae around the end of a sensory neurone
-pressure changes on skin deform lamellae and membrane which widens Na+ channels
what is resting potential?
more Na+ and K+ outside neurone than inside so inside is comparatively negative (-70mV)
maintained by Na+/K+ pump which actively transports 3 Na+ out for every 2K+ in
what is action potential?
neurone’s voltage increases past set point and generates impulse
describe the graph produced by a nervous impulse
stimulus triggers Na+ channels to open, charge reaches threshold (-50mV) so voltage gated channels open, action potential (+40mV) reached so voltage gated channels close, K+ channels permanently open so no Na+ entering while K+ leaves, enters refractory period during hyperpolarisation while pump restores K+
why is the refractory period important?
stop backflow, keep impulses separate, prevent overstimulation
describe the process of synaptic transmission
depolarisation opens ca2+ channels, causes synaptic vesicles to fuse with membrane, releasing neurotransmitters which diffuse across cleft to receptors. na+ channels are conformationally changed by binding, neurone becomes depolarised, neurotransmitter recycled in presynaptic neurone
what is a cholinergic synapse?
neurotransmitter is acetylcholine, enzyme acetylcholinesterase hydrolyses it to acetate and choline
define the term saltatory conduction
the way in which nerve impulses move more quickly down myelinated neurones
define the term spatial summation
multiple neurones meet and collectively trigger an ap in next neurone by releasing neurotransmitters into shared cleft
define the term temporal summation
one neuron releasing neurotransmitters repeatedly into a synapse to collectively trigger ap
what is an excitatory neurotransmitter?
results in the depolarisation of post synaptic neurone
what is an inhibitory neurotransmitter?
results in the hyperpolarisation of post synaptic neurone
