Ch. 48 Pt. 1-2 (Animal Neurons, Synapses, & Signaling)

action potential type stuff & neurons

some neurons can conduct speeds up to________

120 m/s (275 mph)

Peripheral Nervous System (PNS) has which neurons?

1) Sensory neurons(INPUT) →transmit info abt external stimuli (touch or smell)

2) motor neurons(OUTPUT) →transmit signals to muscle cells to contract

Central Nervous System (CNS) has what neurons?

interneurons→lots of dendrites (integration=analysis & interpretation of sensory input)

flow of information processing

sensory input(PNS)→CNS(integration)→motor output(PNS)→effector

know these structures: dendrites, cell body, nucleus, axon hillock, axon, synapse, synaptic terminal

do u know it?

pre-synaptic cell vs. post synaptic cell

pre-synaptic cell→sends the neurotransmitters across synapse

post-synaptic cell→ receives the neurotransmitter signals

examples of glia

these are supporting cells of neurons

1) astrocytes

2) microglia

3) Oligodendrocytes (CNS)→create myelin sheath around axon

4) Schwann Cells (PNS) →create myelin sheath around axon

node of ranvier

where signals “jump” or saltate from 1 node to another

Resting Potential membrane potential(mV) & distribution of ions

-70 mV (-60 to -80)

-more K+ ions inside membrane & more Na+ ions outside membrane

(also Cl- ions outside & proteins inside)

why is it that a neuron is more negative(-) inside & more positive(+) outside) during resting potential?

there are more ungated channels for K+ to diffuse outside than Na+ channels=most positive ions going out=more negative inside

ALL GATED CHANNELS ARE CLOSED

what kind of diffusion is going on in a neuron ALWAYS

passive diffusion of Na+ into cell & K+ ions out the cell

what does Sodium-Potassium Pump do?

active transport that requires ATP

—pumps 3 Na+ out & 2 K+ in to maintain concentration gradient =always more K+ inside than outside during resting potential

what happens during graded potential & what are the 2 types?

specific GATED channels will open when stimulated

1) depolarization

2) hyperpolarizaton

are graded potential actual nerve signals?

NO (only action potential), but they are major effect on generation of nerve signals

what causes depolarization & what happens as a result? its membrane potential?

a stimulus causes Na+ gated channels to open & flow into cell=inside is more positive

-56 to -70mV

what causes hyperpolarization & what happens as a result? its membrane potential?

a stimulus causes Cl- gated channels to open & flow into cell=inside more negative

-80 mV ish

types of GATED ion channels

1) stretch-gated channels→open when membrane is mechanical

2) ligand-gated ion channels→open/close in response to neurotransmitter

3) voltage-gated ion channels→respond to membrane potential

threshold potential to reach action potential?

-55 mV

what causes action potential & what happens as a result?

once threshold potential(-55mV) is hit, a WHOLE BUNCH of Na+ channels will open & flow inside cell=inside more positive

(nerve signal occurs)

sequence of events after resting potential?

resting potential→depolarization→rising phase of action potential→falling phase of action potential→hyperpolarization

(undershoot)→back to resting potential

what happens during the rising phase of action potential

K+ channels are closed & bunch of Na+ channels are open

what happens during the falling phase of action potential

K+ channels reopen & Na+ channels start to close