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