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