Nervous coordination Flashcards
What does the nervous system involve
-detection of stimuli by receptors
-transmission of nerve impulses by neurons
-response by effectors
Types of neurons
-sensory neuron
-relay neuron
-motor neuron
structure of the neuron
-dendrites
-cell body
-nucleus
-axon
-myelin sheath
-nodes of ranvier
-schwann cell
-terminal end branch
function of the nucleus
found in the cell body and contains the DNA which codes for neurotransmitters
function of dendrites
extensions of the cytoplasm of the cell body receiving chemical signals from other neurons at the postsynaptic membrane
function of cell body
contains the nucleus and groups of ribosomes needed to synthesise neurotransmitters
function of axon
long extension of the cytoplasm that transmit impulses away from cell body towards the terminal ends
function of myelin sheath
formed as schwann cells grow around the axon
provide electrical insulation
speeds up transmission
function of schwann cells
surround peripheral nerves and forms myelin sheath
K+ and Na+ ions cannot diffuse through
function of terminal end branch
connect to other neurons or effectors
How is resting potential established
high conc of Na+ on outside of neuron
high conc of K+ on the inside of the neuron
many Na+/K+ pumps that move
3 NA+ out and 2K+ in
via ATP hydrolysis
Na+ voltage gated channel proteins are closed
Na+ pumped out cannot diffuse back in
K+ channel proteins are leaky
K+ can diffuse back out
net result= more positive on outside than inside
How a nerve impulse is transmitted
membrane is stimulated
action potential is where the membrane reaches a threshold and becomes depolarised
an action potential is the reversal of the resting potential
-70mV to 40mV
process of depolarisation
stimulus causes membrane to become more permeable to Na+ ions
Na+ channel proteins are open
higher conc of Na+ outside the cell
Na+ ions rapidly diffuse into the cell via FD
higher conc of Na+ inside the cell reverses action potential
inside is more positive
K+ voltage gated channel proteins remain closed
high conc of + ions is action potential
process of repolarisation
once the internal potential reaches +40mV
Na+ ion voltage gated channel proteins close
K+ voltage gated channel proteins open
more K+ ions inside than outside
K+ ions diffuse out down a conc gradient
process of hyperpolarisation
K+ ion channel proteins remain open longer than needed to reach action potential
inside of the cell more negative to -90mV
sodium potassium pump restores the resting potential back to -70mV
The all or nothing principle
above the threshold the full sized action potential is given regardless of the increase in the size of the stimulus
the refractory period definition
the time taken to restore the resting potential potential
what is the impulse transmission along the axon
action potential acts as a stimulus to adjacent polarised areas of the membrane and this causes the action potential to be passed along
what is saltatory conduction
impulse travels by jumping from one node of ranvier to the next node of ranvier
to increase the rate of transmission
how does temperature affect the rate of transmission
increase in temp
increase in kinetic energy
increase in the rate of diffusion
increase the rate of conduction
how does axon diameter affect the rate of transmission
the larger the axon diameter
the greater the speed of conductance
larger membrane surface area
increase in number of channel proteins
process of synaptic transmission
action potential arrives
ca2+ channel opens
ca+ ion diffuse into the presynaptic neuron via facilitated diffusion
vesicles fuse with presynaptic membrane to release acetylcholine via exocytosis
ACh bind to receptors
Na+ channels open allowing Na+ into postsynaptic neuron
K+ channels open allowing K+ out into the cleft
enzyme acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid using water to break the etser bond
types of neurotransmitters
excitatory
inhibitory
type of inhibitory neurotransmitter
GABA
how do inhibitory neurotransmitters work
resting potential hyperpolarized
less likely to reach threshold in postsynaptic membrane
cannot generate action potential
what is the neuromuscular junction
a synapse between a motor neuron and a muscle cell
uses acetylcholine which binds to recptors
adaptations to muscular junctions that differentiate them from synapses
- lots of folds, increase in surface area for more enzymes
- more receptors
- always triggers a response
what is summation
the build up of neurotransmitters within the synapse
what are the two types of summation
spatial
temporal
process of spatial summation
different neurons converge at a single synapse
action potentials arrive from several different neurons
release of enough neurotransmitter to reach threshold and cause an action potential
process of temporal summation
only one presynaptic neuron
impulses arrive in rapid succession giving a cumulative effect
sufficient to depolarise the post synaptic neuron
