nervous coordination and muscles Flashcards
state differences between the hormonal and nervous system
HORMONAL
- communication is via hormones
- transmission is via the bloodstream
- transmission is usually slow
- response is slow
- response is long lasting
- NERVOUS SYSTEM
- communication is via nerve impulses
- transmission is via neurones
- transmission is very rapid
-response is rapid
- response is short lived
what is the function of the cells body in a neurone
contains cell organelles - large amounts of RER though which is associated with the production of proteins and neurotransmitters
what is the function of a dendron
extensions of the cell body which subdivide into dendrites ( smaller branched fibres).
they will carry impulses towards the cell body
what is the function of the axon
a single long fibre that carries impulses away from the cell body
what is the function of schwann cells
provide electrical insulation, they also carry out phagocytosis
what is the function of the myelin sheath
forms a covering to the axon
what is the function of nodes of ranvier
constrictions between adjacent Schwann cells - electrical impulses can jump making transmission faster
what is the function of a relay neurone
transmit impulses between neurones
what is the resting potential in humans
-65mV
when the axon has a resting potential what is it said to be
polarised
describe how a resting potential is established
- sodium ions are actively transported out of the axon by na/k pumps
- potassium ions are actively transported into the axon by the Na/K pumps
for every 3 sodium’s moved out two potassium’s move in.
-an electrochemical gradient will be established due to a differential in charges - sodium will diffue back in
- potassium will diffuse back out
-however most of the potassium channels are open and the sodium ones will close
what happens when the axon becomes depolarised
an action potential is reached. the charge inside the membrane is +40mV
what happens in inhibiton
the presynaptic neurone releases a type of neurotransmitter that binds to a chloride ion protein channels on postsynaptic neurone.
- the neurotransmitter causes the chloride ion channels to open.
- chloride ions move into the post synaptic neurone by facilitated diffusion
-this binding causes the K+ channels to open
-k+ions move out of the postsynaptic neurone into the synapse
- the combined effect of cl- moving in and k+ moving out will make the postsynaptic membrane more negative than the outside
what si the function of a synapse
acts as a junction to allow a single impulse to initiate new impulses in numerous neurones. and or a number of impulses to be combined at the synapse.
what is temporal summation
where a presynaptic neurone releases neurotransmitter many times over a short period - if the concentration of neurotransmitter exceeds the threshold value then an action potential can be is triggered in the postsynaptic neurone
what is spatial summation
in which a number of presynaptic neurones together release a number of neurotransmitters to exceed the value to stimulate an action potential in the postsynaptic neurone.
where are the neurotransmitters stored
synaptic vesicles
what are features of synapses
- unidirectionality
- summation
what is a cholinergic synapse
a synapse where the neurotransmitter that is secretes acetylcholine
what are some factors that will affect the speed of a nervous impulse
- nodes of ranvier ( jumping or poshly described as saltatory conduction) this will increase the speed of conductance.
- the diameter of the axon - the greater the diameter of the axon the faster the speed of conductance
-temperature - this will affect the rate of diffusion of Na/K ions
higher = faster however denaturing of plasma proteins
what is the all or nothing principle
the threshold value of stimulus which is needed to trigger an action potential. nothing will happen without this threshold value so no action potential.
its all or nothing
what is the refractory period
when the sodium ion channels are closed - during this time it is impossible for a further action potential to be generated
what is the purpose of a refractory period
- it ensures that action potentials are only propagated in one direction
- it allows for action potentials to be separated from one another
- it limits the number of action potentials and therefore the strength of the stimulus that can be detected
what is a receptor
a protein or cell that can detect stimulus
define a neurotransmitter
a chemical which is secreted by a neurone within the nervous system to stimulate a target cell
what are the main ways that drugs act on the synapse
- drugs can mimic a neurotransmitter
- stimulate the release of a neurotransmitter
- inhibit the enzyme that breaks down the neurotransmitter
- block a receptor channel
describe the signal transmission of ACh at the cholinergic synapse
- an action potential arrives at the end of the presynaptic neurone
- this depolarises the membrane and stimulates the voltage-gated Ca2+ channels to open and an influx of Ca2+ to enter the synaptic knob
- this influx of Ca2+ causes the vesicles containing ACh to fuse to the presynaptic membrane and releasing ACh intot he cleft via exocytosis
- ACh diffuses across the cleft and binds to the specific receptors on the postsynaptic membrane - which will cause a slight delay in impulse
- the neurotransmitter binds to the Na+ channels which open and an influx of sodium depolarises the postsynaptic membrane
what happens when acetylcholine diffuses across to the postsynaptic neurone
acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid, which diffuses back across the synaptic cleft intot he presynaptic neurone. this is advantageous because discrete transfer of acetylcholine can occur across the synapse
How do we actually see
Pigment is bleached
