1.27.25 lecture: white & grey matter, principles of electricity

true/false: nerve is a term that only refers to the PNS, NOT the CNS

TRUE

what's that neck part at the base of the soma and top of the axon?

axon hillock

what color is myelin?

white

when you see white matter in the nervous system, you're looking at ________________ axons of neurons

myelinated

grey matter means it could be ________, _____________, or ____________-

cell bodies, dendrites, or unmyelnated axons

_______ and _________ are never myelinated

dendrites and cell bodies

cortex is always ___________ matter, which is composed mostly of __________ and ____________

grey; cell bodies and dendrites

__________ refers to the wrappings associated with the axon

myelin

the myelin producing cells are ______________ and ________________

Schwann cells and oligodendrocytes

what is the most important function of myelin?

increases the speed of nerve impulse transmission from the axon hillock to the terminal

a ______________ is the concentric layers of Schwann cell membrane

myelin sheath

what is unique about the plasma membrane where the myelin producing cells wrap around the axon?

where the myelin producing cells wrap around the axon, we have no means for ions to cross the membrane (no channels or pores)

true/false: not all axons are myelinated

true, but the unmyelinated axons are very slow

______ and _________ are never myelinated

dendrites and cell bodies

what are nodes of Ranvier?

gaps between myelin sheath along axon

true/false: all action potentials work the exact same

true. we cannot distinguish one action potential from another, you either have one or you don't.

the resting potential energy value for neurons is _________________

-70 milivolts

we measure the potential energy of the cell membrane with ________

voltage

_____________ is the hindrance of charge flow (provided by the plasma membrane)

Resistance

______ is a substance with high electrical resistance

insulator

_____________ is an insulator

myelin

____________ is a substance with low electrical resistance

conductor

____________ is a conductor

water with electrolytes

at homeostasis, sodium is on the ______ of the cell and potassium is on the _________ of the cell

outside; inside

as ions diffuse down their channels across the membrane, the cell is taken out of homeostasis. how do we fix this?

sodium potassium pump

__________________ uses ATP directly to restore homeostasis of resting membrane potential

sodium potassium pump

why does the Na K pump need ATP?

because it pumps ions up their concentration gradient

explain how the sodium/potassium pump works

sodium enters, the pump is phosphorylated, sodium is release into ec space, K enters, Pi falls off, pump changes shape and releases K into cytosol