| Reflex arc | stimulus - receptor- (sensory neurone) -CNS (Relay neurone) - (motor neurone)- effector response |
| the receptor for the following stimuli
light-
sound-
temp-
smell
-pressure
blood pressure
blood co2 | photoreceptors
-ear
-thermoreceptors
- nose
-panincal corpuscle
-pressure receptors
-chemoreceptos |
| Features of the structure of a neurone | -cell body
-axons conduct implulses
- myelin sheath - eletrical insulation contains many lipids
-nodes of ranvier - gaps in myelin
-synaptic knob - communication to other nuerones |
| resting potential | sodium potassium pump in the axon membrane actively transports 3 NA+ out of the axon for every 2K+ transported in.
Potassium chanels in axon membrane diffuse K+ ions of the axon from high to low by facitlilated diffusion making the charge -70mv |
| Action potential | Depolarisation occurs when sodium gated channels open
sodium diffuses in by FD
stimulating others to topen
passing a threshold
40mv
repolarisation
Na+ channels CLOSE
K+ chanells open so K+ diffuses out of the axon lowering membrane potential to -70mv |
| All or nothing principle | all - sodium gated channels pass threshold impulses travel
nothing - weak stimulus threshold not passed |
| what is a refractory period | the time when time in when action potential occurs |
| why are refractory periods occur | produces discrete impulses in one direction
limits the freq of impulses
action potentials are unidirectional |
| Factors affecting speed of transmission | -myelin sheath
insulates - nodes of ranvier are where depolarisation occurs , impulses jump from node to node called saltatory conduction
-axon diamter - bigger = less resistance
-temp diffusion faster |
| diffusion across synaspes | Action potential arrives at the pre synaptic knob
stimulates calcium channels to open diffusing calcium in
causing vesicles containing neurotransmitters to fuse with pre synaptic membrane realasing ach
ach diffuses across synaptic cleft
ach binds with receptor proteins trigerring sodium gated channels to open so sodium diffuses in by FD , if enough sodium diffuses in , threshold is passed. impulses continue |
| How are synapses unidirectional | vesicles containing neurotransmitters are only found in the pre synpatic knob
receptors
receptors are only found in post synaptic knob
so neurotransmitters cam only go from pre to post |
| What are excitatory and inhibitory synapses | excitatory - synaptic synapses
inhibitory - prevent transmission |
| differences in inhibitory synapses | Potassium channels open and K+ DIFFUSES OUT
CL channels open and CL- diffuses in so more negative so threshold not passes |
| what is spatical summation | multiple pre synaptic neurones - lots of ach - threshold |
| what is temporal summation | one after the other in the same place
ach - threshold |
