NERVE IMPULSE NERVE IMPULSE l An electric message

NERVE IMPULSE

NERVE IMPULSE l. An electric message sent on neurons. 4 stages of sending message.

STEP 1 l. Resting potential: -70 m. V (millivolts) difference between inside and outside. l. Na+ ions outside l. K+ and Proteins inside.

STEP 2 l. Action potential: Membrane stimulated l. Na+ gates open (come in) l. Depolarization (+30 m. V)

Step 3 l. Repolarization: l. K+ ions gates open (go out) l. Returns to -70 m. V

Step 4 l. Recovery: l. Na/K pumps use ATP (energy) to pump back to original places. l. Shuts down until complete!

CONDUCTION l. The nerve impulse travels like a wave. l 2 different methods.

CONDUCTION l. Myelinated: impulse jumps from node to node. FASTER (100200 m/sec)

CONDUCTION l. UN-myelinated: impulse goes from point to point. SLOWER (1 m/sec)

l. Look at your textbook example on page: 223

Synaptic Transmission

Synaptic Transmission l. Chemical message going from one neuron to another.

SYNAPSE l. Where impulse crosses gap by changing from electric chemical electric

COLOR CODE l. Please color code the synapse l. B, I, g, j, h, k

Synaptic knob l. B. Enlarged end of the axon.

Synaptic Cleft li. The gap between dendrite and knob.

Synaptic Vesicle l. G. Hold chemical neurotransmitter.

Neurotransmitter l. J. Chemical released to cross cleft and start impulse. l. Aceytlcholine (Ach) l. Page 216

Presynaptic Membrane l. H. Membrane of axon before Cleft.

Postsynaptic Membrane l. K. Membrane of dendrite AFTER cleft. l. Contain receptor sites for neurotransmitter.

EVENTS l. There are basically seven steps that happen when a signal is sent over the synaptic cleft.

EVENTS l 1. Action potential arrives at synaptic knob (+30 m. V)

EVENTS l 2. Ca ++ ions flow into the synaptic knob.

EVENTS l 3. Vesicles merge with pre-synaptic membrane and release neurotransmitter.

EVENTS l 4. Neurotransmitter (Ach) diffuses across cleft (key).

EVENTS l 5. Neurotransmitter binds with receptor (lock) on postsynaptic membrane.

EVENTS l 6. Na+ gates open and action potential begins.

EVENTS l 7. Neurotransmitter broken down by enzyme (Ache). l. Gates close.