NEURONES Flashcards
outline the basic nervous pathway
stimulus -receptor - sensory neurone - CNS(relay neurone) - Motor neurone - effector-response
function to receptor
recieve stimuli and send it to CNS via sensory neurone
what does cns consist of
brain + spinal chord
what are 2 types of effects
muscles, glands
what is function of dendron
send impulse to the cell body
function of cell body
holds organelles and releases neurotransmitters
how can we identify the type of neuron
looking at position of cell body
function of axon
sends impules away from cell body
what is the function of myelin sheath
insulation layer on neurone that helps speed up the rate of nervous transmission
what are branches on dendron called
dendrites
where is cell body on a sensory neuron
found in the middle of the neurone
what are the nodes of ranvier
gaps in neurone that aren’t covered by myelin sheath
where is the cell body on a motor neuron
At the start of neurone
do motor neurones have a dendron
No have dendrites (as cell body is at start of cell so only have axon)
what is the smalllest neurone and where is it found
relay neurone found in CNS
what makes the myelin sheath
schwann cells (stretched and wrapped up = myelin sheath)
how can we tell apart the different neurones
relay neuron has no myelin sheath
sensory neuron cell body found in the middle of cell
motor neuron cell body found at start of cell
function of sensory neurone
transmit nervous impulses from a sensory receptor cell to relay neuron,motor neuron or the brain
function of relay neurone
transmit impulese between neurones
function of motor neurone
transmit impulses from relay or sensory neurone to an effector
myelinated vs unmyelinated neuron - rate and method of transmission
myelinated - faster transmission of electrical impulse as jumps from one node of ranvier to the other
unmyelinated - slower transmission as electrical impulse must pass continuously along neurone.
what cells detect changes in the environment
sensory receptors
what is meant by sensory receptors are ‘transducers
transducers convert a stimulus into a nerve impulse
what are the 2 main features of sensory receptors
- specific to single type of stimulus
- act as transducer(convert stimulus to neve impulse(generator potential)
4 type of sensory receptors and what their stimulus
photoreceptor - light
thermoreceptor - heat
chemoreceptor - chemicals
mechanoreceptor - pressure and movement
what type of receptor is a pacinian corpuscle
mechanoreceptor(detects changes in pressure or movement)
how does structure of pacinian corpuscle allow it to change physical stimulus to generator potential
- end of sensory neurone found within centre of corpuscle
- stretch mediated sodium channel and when they change shape- the permeability of sodium ions also change.
In normal state - sodium ion channels are too narrow
When pressure is applied - change shape allowing more ions to diffuse into neurone - influx of sodium ions depolarises cell resulting in generator potential
- generator turns into action potential and then passed along sensory neurone.
How does body detect your finger has touched a pin
- pressure exerted onto skin
- pacinian corpuscle detects pressure change
- change in pressure widens gated sodium channels allowing more ions to diffuse through
- influx of ions causes membrane to depolarise
- creating general potential that turns into action potential (once threshold is met)and is transmitted along neurones to CNS
how does the body detect difference between large and small stimulus
more frequent action potentials
Explain synapse mechanism and how excess neurotransmitters are dealt
- action potential arrives
- depolarisation of pre-synaptic neurone triggers calcium channel to open
- influx of calcium ions causes synaptic vesicles to fuse aginst pre synaptic membrane
- vesicles release neurotransmitters into synaptic cleft via exocytosis
- neurotransmitters diffuse across and bind onto receptors on post synaptic neurone
- causing sodium gated channels on post synpatic neurone to open
- influx of sodium ions causes depolarisation and action potential is generated if threshold is met
- excess neurotransmitter is broken down by enzmes
how does motor neurone cause a post synaptic neurone to depolarise
- action potential reaches pre synaptic neurone
- depolarisation of pre synaptic membrane triggers ca2+ channels to open
- influx of ca2+ ions causes vesicles to fuse with pre-synaptic membrane
- neurotransmitter diffuse across synaptic cleft
- bind to to receptors on post synaptic membrane
- allows sodium channels to open and sodium ion diffuse into neurone
- threshold potential reached
- muscle cell contracts
what is a cholinergenic synapse
synapses that use acetylcholine
what is the post synaptic receptor in cholinergenic synapses
cholinergenic receptors
How is an action potential generated
A; resting potential -70mv - Sodium potassium pump open(actively transport 3NA+ out and 2K+ in), gated sodium pump closed (no na+ can diffuse back into axon), potassium pump open(K+ can diffuse out of axon)- inside membrane (-) outside membrane(+)
B- energy from stimulus triggers some of sodium gated channels to open allowing sodium ions to diffuse down chemical gradient
C - depolarisation -positive feedback so more sodium voltage pump open - allowing influx of sodium ions into membrane - causing more (+) inside membrane (-)outside membrane. Threshold is met- greater number of sodium pumps open(-55mv)
+E - repolarised membrane - from +40 mv potassium channel opens, allowing potassium ions to diffuse out of axon to decrease potential difference, sodium gated channels close
F-hyperpolarisation -80mv - too much K+ diffused out so more negative potential difference
G - repolarisation - K gated channels shut, sodium potassium pump opens , -70mv re-established
What is saltatory conduction
Propogation of axon potential along neurone with myelin sheath (saltatory conduction)
