neuronal communication Flashcards
what is the role of the sensory neurone
transmits nerve impulses from receptors to the CNS
what is the role of a motor neurone
transmits nerve impulses from CNS to effectors
what is the role of a relay neurone
transmit nerve impulses between sensory and motor neurones
whta is the order of neuronal communication
stimulus, receptor, sensory neurone, CNS, relay, motor, effectors, response
what is the central nervous system
brain and spinal cord
What is the peripheral nervous system
all neurones which bring information to the CNS and that take information away
the PNS is split into two systems, name and describe them
somatic- responses under voluntary control, uses neurotransmitter acetylcholine
autonomic- responses under subconscious control, uses acetylcholine and noradrenaline as neurotransmitters
the autonomic system is divided into two, name and describe them
sympathetic- involved in flight or fight response, uses noradrenaline
parasympathetic-used in rest and digest system and uses acetylcholine
why are sensory neurones referred to as biological transducers
convert a stimulus such as touch or light into an electrical nerve impulse
what type of receptor is the sensory neurone named in the spec, what stimuli does it respond to, where is it found and what is it called
Pacinian corpuscle, mechanoreceptor, mechanical energy, skin
how is resting potential established and maintained
in resting state the inside of the cell is negatively charged compared to outside, this creates voltage across the membrane (also known as potential difference)
sodium potassium pumps use active transport to move three sodium ions out for every two potassium ions in
potassium channels allow facilitated diffusion of potassium ions out of the neurone, down the conc. gradient
the membrane is not permeable to sodium ions therefore they cannot diffuse back in and an electrochemical gradient is created
at cell rest most of the potassium ion channels are open
how is generator potential established
when a stimulus is detected the cell membrane becomes excited and more permeable
this allows more ions to move in and out
this alters the potential difference
how is action potential established
if generator potential is big enough (reaches threshold level) it’ll trigger an action potential along a neurone
when a neurone is stimulated sodium ion channels open and if the stimulus mis big enough it’ll trigger a rapid change in p.d what does this cause the cell membrane to become
depolarised
describe the series of events that make up an action potential
stimulus- excited cell membrane causing Na+ channels to open, ions diffuse down electrochemical. gradient into the neurone and it becomes less negative
depolarisation- if p.d reaches the threshold around -55mV voltage-gated Na+ sodium channels open and more sodium ions diffuse into the neurone (positive feedback)
polarisation- occurs at +30 mV sodium ion channels close and voltage gated potassium ion channels open, membrane more permeable to potassium so potassium ions diffuse out down potassium ion gradient, bringing the membrane back to resting potential, negative feedback
hyperpolarisation- potassium ions are slow to close so there is an overshoot where too many potassium ions diffuse out of neurone, p.d becomes more negative than the resting potential
resting potential is retuned
draw a graph and label it tow show an action potential
describe the refectory period
the neurone cell cannot be excited again straight away as ion channels are recovering and cannot be made to be open, acts as a time delay between action potentials, prevents overlap and makes sure they are unidirectional
what is the all or nothing principle
once the threshold is reached an action potential will always fire with the same change in voltage no matter how big the stimulus is
how does myelination affect speed of conduction
myelin sheath acts as an electrical insulator, myelin sheath is made up of Schwaan cells and between these are bare membrane down as Nodes of Ranvier
what is saltatory conduction
when the neurones cytoplasm conducts enough electrical charge to depolarise the next node so the impulse ‘jumps’ from node to node
how dos axon diameter affect speed of conduction
action po. conducted quicker along axons with bigger diameters because there us less resistance to flow of ions
how does temperature affect speed of conduction
increases as temp increases as ions diffuse faster
what is a synapse
the junction between one neurone and another
hat is gap between cells at a synapse called
the synaptic cleft
draw a diagram with a cholinergic synapse
describe how a nerve impulse is transmitted across a cholinergic synapse
action potential arrives at synaptic knob of presynaptic neurone
action po. stimulates voltage gated calcium ion channels to open
calcium ions diffuse into synaptic knob
influx of calcium ions causes synaptic vesicles to move to presynaptic membrane
they fuse with the presynaptic membrane
vesicles release ACh into synaptic cleft via exocytosis
ACh diffuses across synaptic cleft and binds to specific cholinergic receptors on the postsynaptic membrane and this causes sodium ion channels to opne
influx of sodium ions causes depolarisation
action potential on the postsynaptic membrane is then generated if the threshold is reached
ACh is removed from synaptic cleft and broken down by acetylcholinesterase and products are reabsorbed by the presynaptic neurone and used to make more ACh
