Neurology

central nervous system

brain and spinal cord

peripheral

neural tissue outside of CNS

nerves

bundle of axons that travel together

synaptic terminal

communication with next neuron happens here

axon hillock

decision of sending signal made here

axolemma

plasma membrane surrounding axon

prototypical neuron

specialized for intercellular communication

anaxonic neuron

more than 2 processes but axons cannot be distinguished from neurons

bipolar neurons

two processes separated by cell body

unipolar neurons

single elongate process with cell body situated off to side

multipolar neuron

more than 2 processes with single axon and multiple dendrites

afferent neurons

carry information towards the spinal cord or brain

somatic

sensory information about external world

visceral

sensory information about internal systems

efferent neurons

carry information away from the brain and spinal cord

somatic

motor neuron that innervates skeletal muscles

visceral

motor neuron that innervates smooth and cardiac muscle, glands

interneurons

communicate between neurons

neuroglia

supporting cells; 1/2 of all nervous tissue; diverse set of structure and function

ependymal cells

generate cerebralspinal fluid

astrocytes

tightly regulate what passes through blood vessels (maintain BBB, regulate nutrients, structural support)

oligodendrocytes

myelination and structural support in CNS

schwann cells

myelination and repair in PNS

satellite cells

regulate nutrients

microglia

phagocytes and remove dead cells and waste

cerebrospinal fluid

functions in protection/support, circulation of nutrients, removal of waste, and immune protection (like the bloodstream)

blood brain barrier

highly selective permeable membrane
specialized capillaries and neuroglia tightly regulate what moves into CSF from plasma

myelin

insulating series of membranes which surround SOME axons

white matter

axons surrounded by myelin

gray matter

unmyelinated axons

myelin sheath by Schwann cell

schwann cell surrounded axon on cytoplasm, then begins to rotate around the axon creating the tightly packed membrane of myelin

voltage

difference in electrical potential between 2 points

current

movement of charge to eliminate potential

resistance

anything which impedes movement of charge

membrane potential

measuring inside of cell to outside

positive

outside of cell charge

negative

inside of cell charge

greater current

higher voltage =

ohms law

I=v/r

resting membrane potential

electrical potential difference across membrane during rest conditions

-70 mV

for the typical neuron the RMP is...

net electrochemical gradient

forces potassium ions out of the cell

-90mV

potassium equilibrium potential

drive sodium ions out of the cell

at normal resting potential, chemical and electrical gradients combine to...

-66mV

sodium equilibrium potential

K+

the membrane contains more _____ leak channels

leak channels

at rmp, movement of ions is regulated by ...

greater resistance

what gives sodium a smaller current

active transport

Na+/K+ pump in resting membrane potential

primary active transport

moves ions against passive gradient

remove sodium that leaks in and recapture potassium that leaks out

goal of primary active transport

3 sodium, 2 potassium

transport of ___ out of the cell and ____ into the cell

chemical gated channels, voltage gated channels

changed in rmp occur primarily due to activation of ____________ and spread via activation of ______________

chemically gated channels

chemical binds to channel and causes it to open

voltage gated channels

once voltage is reached, channel is opened and ions can flow in

polarized

inside of cell is negative relative to outside

depolarization

process of making inside of cell less negative (move toward zero)

both Na open
K close

depolarization channels

repolarization

process of returning membrane potential back to resting membrane potential

inactivation gate closed
K open

repolarization channels

hyperpolarization

process of making inside of cell more negative (less than -70)

graded potential

localized change in membrane potential

EPSP

stimulus opens chemically gated Na channels
leads to depolarization
increases likelihood of action potential

IPSP

stimulus opens chemically gated K channels
leads to hyperpolarization
decreases likelihood of action potential

action potential

propagated change in membrane potential down length of axon

threshold

-60 to -55mV
all or none
chemically gated channels
once achieved, an action potential is inevitable

depolarization

voltage gates sodium channels open
Na enters cell
electrically gated channels

repolarization

voltage na channels open
voltage k channels open
k ions leave cell
potential decreases toward rmp

hyper polarization

k movement out of cell continues
excess loss of positive charges
potential drops below rmp
voltage k channels close
return to rmp

closed

AT REST: na channels - activation gate _____

open

AT REST: na channels - inactivation gate _____

closed

AT REST: k channels _____

refractory period

period of rest following activity

absolute refractory period

the cell cannot be stimulated to fire another action potential

depolarization or repolarization

what causes ARP?

the na gates are already open

why does depolarization cause ARP?

the na gates are closed

why does repolarization cause ARP?

relative refractory period

the cell can only be stimulated to fire another action potential IF the depolarization event is GREATER than usual

the cell is hyperpolarized

what causes RRP?

continuous propagation

diffusion of sodium down axon on unmyelinated axons
depolarization of membrane in one region

unidirectional propagation

regions behind action potential are in refractory period and cannot be reactivated

saltatory propagation

ions cannot flow through membrane at myelinated regions so the action potential jumps from node to node

saltatory

which type of propagation is faster

saltatory conduction

gated depolarization brings axolemma to threshold, action potential develops at node 2, local current produces gated depolarization that brings axolemma to threshold at node 3

synapse

site of neural communication

synaptic transmission

neuron sends signal to communication with muscle cell

cholinergic synapse

acetylcholine in active neurotransmitter

glutamate

major excitatory nt
causes depolarization

GABA

inhibitory effect
causes hyperpolarization

Norepinephrine

excitatory effect

dopamine

excitatory or inhibitory depending on location

serotonin

excitatory effect (involved in emotion)

nitric oxide

primarily released by neurons