9.2 Flashcards
peripheral nervous system
afferent
-sensory
efferent
-motor
central nervous system
central -brain and spinal chord
peripheral - pairs of nerves which originate from the brain or spinal chord
efferent nervous sytem
somatic
-under voluntary control
autonomic
-involuntary
autonomic nervous system
sympathetic
-positive stimulation
-speed up
-fight or flight
parasympathetic
-inhibitory
-slows down activity
-resting and digesting
compare and contrast sym and para
sim -
NS fibres leave the CNS in a ganglion (collection of nerve fibres)
dis-
sym, ganglia close to the CNS
para, ganglia close to the effector organ y
compare and contrast sym and para funtions
sym
-produces noradrenaline
-fight or flight response
-activated in times of stress or active
-adrenergic synapses
para
-slower, inhibitory effect
-acetychloine neurotransmitter produced
-maintains normal functioning of the body
-chloinergic synapses
resting potential
inside of the axon is negatively charged compared to the outside of the axon
outside ions more concentrated
axon is polarised
-70mV
sodium pottasium pump
requires energy
3 Na+ ions moved out of the membrane for every 2 K+ ions in
ATPase in pump uses ATP to move cations
how is resting potential maintained
sodium pottasium pump
Na+ out K+ in
K+ move through pottasium chanells
NA chanells close
outside more positive than inside
action potential
stimulus is recieved
causes a tempary reversal of the charge on the axon membrane - inside less negative
moves to about +40mv
membrane depolarised
depolarisation
-resting potential some k voltage-gated channels are open but Na channels are closed
-the stimulus causes some Na gates in the axon membrane to open and therefore some sodium ions move into the axon via facilitated diffusion
as they are +vly charged they trigger a reversal in the pd
-as it is more +ve more voltage-gated sodium channels open - +ve feedback
-once the action potential is around +40mv the voltage-gated sodium ion channels close
-excess sodium ions are pumped out by Na-K pump
repolarisation
-voltage-gated potassium channels open so K ions move out the axon by facilitated diffusion down the conc grad
-cell is repolarised and becomes more negative
hyperpolarisation
-more potassium flows out
- the inside is more negative than the outside so more negative than the resting potential
after hyperpolarisation
gates on K+ channels now close and Na-K pumps Na to be out and K in
-70 mv is reestablished
action potential simplified
Na+ voltage gated channels open
Na+ diffuse rapidly into axon
potential difference reversed
Na+ voltage gates close
K+ voltage gated chanells open
K+ diffuse out of axon
inside axon returns to negative
resting potential restored
absolute refractory period
sodium chanells are completly blocked and the resting potential hasnt been restored
milisecond
second stimulus will not trigger a second action potential
relative refractory period
pottasium chanells are able to repolarise the membrane and pottasium ions difuse out of axon
Normal resting potential can not be restored until these K channels are closed.
Last several milliseconds.
During this time, a greater than normal stimulus is required to initiate an action potential.