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Neuron
4 regions:– Cell body
Contains nucleus Metabolic center
– Presynaptic terminals– Dentrites
Receive incoming signals from other nerve cells
– Axon Transports signals away to
other neurons
What is an Action Potential?
Defn. Electrical signal conveyed down an axon What causes it?
– An environmental stimulus (ex. Light, pressure, odor, mechanical contact, etc.)
These stimuli cause the axon hillock (start of the axon) to create an action potential
The action potential continues to the end of the axon
Action Potential Properties
Travel small or large distances (.1mm-3m) Rapid and transient (duration of about 1ms) Constant amplitude (100mV) All or none nerve impulse Travels in one direction (principle of dynamic
polarization)
(Dominos display)
Action Potential Overview
K + cha n n e l c lo sesre tu rn s to re stin g p o ten tia l
h yp e rp o la riza tionm e m b ran e m o re p erm ea b le to K + th a n n o rm a l
R e p o la riza tion K + o u tf lo w th ru o pe n vo lta ge -ga te d K + ch a nn e lsN a + ch a nn e l in a c tiva tion g a te s c lo se
a d jace n t m e m b ra ne vo ltag e g a ted N a + ch an n e ls op end e p o la riza tion p ro p ag a te d (a ka co nd u ctio n )
re s ting m e m bra n e p o ten tia l (-7 0m V )th re sho ld (-55 m V )
N a + in flu x th ru o p en N a+ cha n ne l a ctiva tio n ga te s (+ 3 0m V )d e p o la riza tion
A xo n h illo ck(in it ia l seg m e n t)
e n v iro n m e n ta l s t im u lus
How does the action potential impact the neuromuscular junction?
m u scle co n trac tion
m u sc le a c tio n po ten tia l c rea ted
ca tion (N a +) ch an n e l o pe n s cha n g in g th e re s tin g m e m b ran e po ten tia l
A C h b ind s to re ce p to rs a t the m u sc le m ote r e n dp la telo ca ted in m id -m u sc le
syn a p tic ve s ic lesb in ds to p lasm a m em bra ne
syn ap tic e n d b u lbs
a xo n te rm in a ls
a c tion po ten tia l