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