What makes up the CNS

cerebral cortex, cerebellum, brainstem, spinal cord

Afferent neurons

info from periphery to spinal cord via dorsal roots

Efferent neurons

info from spinal to periphery via ventral roots

Types of glia & functions

Oligodendrocytes: make myelin in CNS, make Schwann cells in PNS Astrocytes: buffer K+, maintain BBB Microglia: immunity

Types of neurons

Bipolar, Psuedo-unipolar (aff/eff neuron), multipolar

What is the resting membrane potential?

-70 mv

Pumps vs ion channels?

Pumps: active transport Ion channels: passive or gated (ligand/voltage)

T/F: 3Na/2K pump requires ATP

True

T/F: Na wants to go inside cell

True, but 3 Na come out and 2 K come in due to conc gradient = net negative charge inside cell (which is why Na wants to come in)

Leak channels

- Passive flow in or out - always open - selective

Equilibrium potential for K

-90 mv (Eq movement = no net movement)

Equilibrium potential for Na

+55 mv

Which ion is more permeant? Na or K

K+ - the more permeant = the greater ability to force Em to its Eq potential

What causes depolarization

stimulus to get resting membrane to -50 mv

How does a neuron depolarize

- a stimulus causes voltage-gate ion channels to open and makes Na flow inside cell = less negative membrane potential

What is the absolute refractory period

1. Na channels open 2. K channels open, Na is inactivating - cannot fire another AP

What is the relative refractory period

1. K channels are still open, Na channels in resting state - need a strong stimulus to fire an AP

What causes hyperpolarization

K is going through leak channels AND OPEN voltage gated channels at the end of AP

Electrotonic conduction

spread of current inside axon - AP at one point, current spreads to adjacent membrane then depolarizes the next one w/ AP

T/F: there is myelin of the cell body and dendrites

False

T/F: Many Schwann cells ensheath many axons in the PNS

False, they ensheath 1 axon in the PNS

T/F: One Oligodendrocyte ensheath many axons in the CNS

True

Saltatory Conduction

AP doesn't depolarize every cell, it goes from node to node

Group 1 fiber type

- thickest diameter - fastest conduction

T/F: electrical synapses are bidirectional

True

Directly gate synapses

- binds - receptor channels open - ions pass through - fast, short lasting effects - receptor/effector are same molecule

Indirectly gated synapses

- binds - 2nd messenger system: ATP to cAMP - ions flow - slow, long effects - receptor/effector are different molecule

What does cAMP do?

activates protein kinases to phosphorylate = open or close channel / change permeability

T/F: inhibition is only possible with electrical synapses

False, inhibition is only possible with CHEMICAL synapses

EPSP

Na pass through

IPSP

Cl- or K+ pass through

Excitatory presynaptic neuron

glutamate binds and opens Na channels - creates EPSP - doesnt reach threshold

Inhibitory presynaptic neurons

GABA/glycine binds and opens Cl- channels - hyperpolarizes - creates IPSP

T/F: synaptic potentials decay as they travel away from synapse

True, it can only travel short distances

Temporal summation

PSP's from presynaptic neuron overlap and add together

Spatial summation

PSP's in diff regions of postsynaptic neurons are added together

Smooth muscle

- found in walls of hollow organs - regulates blood flow, moves food, expels urine, regulated air flow - involuntary

Cardiac muscle

- striated walls of heart - propels blood through heart circulatory system - involuntary

Skeletal muscle

- muscle attached to skeleton - voluntary control

Endomysium

electrically isolates muscle fibers from one another

Ionotropic receptors

form ion channels after ligand-binding ACh binds to nicotinic receptors