Central - brain and spinal cord
Peripheral - everything else
soma - body
dendrites - the fingers that extend from the soma or cell body
afferent - from the body to the central nervous system (sensory information)
Sensory info - coming into the CNS (from the body)
Afferent neuron
Interneuron - in between CNS and PNS
Motor info - coming out of the CNS (to the body)
Efferent neuron
Neurons: nerve cells
Receive information in dendrites
Information flows through the axon
Eventually reaches an effector
Synapse: gap between two neurons
Synaptic terminals
Glial cells
Support the neurons
Schwann cells & Oligodendrocytes
Myelin sheath
On the axon
Function: prevents cross-talk and accelerates the speed of action potential
Schwann cell - produces myelin sheath in PNS
Oligodendrocytes - produces myelin sheath in CNS
Like an octopus: many arms wrapping around different / same neurons unlike Schwann cell
Node of Ranvier - space in between schwann cells
Saltatory conduction
Presence of node of Ranvier allows jumping of signals → much faster nerve impulse
jumps from node to node
Grey matter - cell body, dendrites, synapses
White matter - myelinated axons (white color comes from lipid)
Dorsal root ganglion
Large collection of afferent neurons near the spinal cord
Cell body
Location is different in Sensory vs. peripheral neurons
Sensory neurons - cell body in dorsal root ganglion
Peripheral neurons - cell body in gray matter
(make sure to know how to identify which microscope took what kind of pictures)
SEM vs. TEM
SEM - outer surface
TEM - inner matter, more detail?
Interneurons
Help with more complicated types of signals such as reflex
Non-decremental action potential: does not die out over space
Energy at first same as energy at the end
Nerve impulse
Resting membrane potential: Inside of axon is -70 mV due to negatively charged proteins inside
Inside: potassium outside: sodium
Ions cannot diffuse in and out of membrane: requires proteins to allow exchange
Depolarization (sodium influx)
Threshold hit: open voltage gated sodium channel → facilitated diffusion of sodium ions (NA+) into the cells → inner charge becomes more positive
Repolarization (potassium efflux)
Voltage gated potassium channels open a little later → facilitated diffusion of potassium ions (K+) to out of the cells → inner charge becomes more negative
hillock
Refractory period
Absolute: absolutely will not get an action potential during this period
Relative: membrane potential lower than -70mV → can get an action potential depending on the size of the stimulus because it requires a bigger stimulus to reach the threshold
Sodium-potassium pump
Active transport (against concentration gradient)
resets the sodium and potassium to allow the nerve impulse to happen again
pumps 3 sodium out, pumps 2 potassium in
Intensity is indicated by the frequency of action potentials
Ex. very hot - thousands of action potentials
Ex. nice and warm - some action potentials