Notes Pt 2.pdf

Intro to Neurophysiology Wednesday, September 4, 2024 12:22 PM - Anatomy of Neuron ○ Dendrite ▪ Receives stimuli ▪ Sends to Soma ○ Soma ▪ Body that synthesizes neurotransmitter ○ Myelin sheath ▪ Speeds up transmission...

Intro to Neurophysiology Wednesday, September 4, 2024 12:22 PM - Anatomy of Neuron ○ Dendrite ▪ Receives stimuli ▪ Sends to Soma ○ Soma ▪ Body that synthesizes neurotransmitter ○ Myelin sheath ▪ Speeds up transmission ○ Node of Ranvier ▪ Gap between myelin sheaths ○ Axon ▪ Actual area where impulse travels ○ Axon terminal ▪ Synapses with muscle, gland, or another nerve to send signal down ○ ○ Thinking/ performing ▪ Axo-dendritic synapse □ An example of this is: Beginning to learn, starting to develop ▪ Axo-somatic synapse □ An example of this is: Been doing something for a while now, few years ▪ Axo-axonic synapse □ An example of this is: Been doing something for whole life now - RMP ○ Electrochemical gradient ▪ Concentration gradient □ Ions moving from high to low concentration ▪ Extracellular □ Na ▪ Intracellular □ K ○ Action potential ▪ Depolarization Exam 1 Page 1  ▪ Depolarization □ Influx of Na ▪ Hyperpolarization □ Efflux of K ○ Channels ▪ Voltage-gated □ A change in intracellular charge opens this channel ▪ Ligand-gated □ A molecule binds to a specific site on the on the channel causing it to open ▪ Leaky channels □ A channel that facilitates passive diffusion of a specific ion/molecule - Neural communication ○ Post-synaptic potentials ▪ Excitatory post-synaptic potential (EPSP) □ Glutamate ▪ Inhibitory post-synaptic potential (IPSP) □ GABA ▪ EPSP and IPSP are examples of graded potentials that are generated in dendrites. This potential is proportional to the strength of the stimuli received. ○ Graded potentials ▪ Spatial summation □ Space: Receives stimuli from multiple neurons close together in the same timeframe ▪ Temporal summation □ Time: Receives repeated stimuli from one neuron in a small time frame (another stimuli is received before the initial one fades) ▪ - Axon ○ Myelin is electrical conductor ▪ Created by Schwann cells in PNS & oligodendrocytes in CNS ○ Action potential ▪ All or nothing ▪ Need to hit -55 mV ▪ Exam 1 Page 2  ▪ ○ Steps ▪ 1) RMP □ Both Na & K gates closed ▪ 2) Graded potential □ Some Na gates open due to influx of Na through ligand-gated Na channels in dendrite ▪ 3) Depolarization □ Threshold reached, more Na gates open, large influx of Na ▪ 4) Repolarization □ Na gates close, K gates open, efflux of K outside of the cell ▪ 5) Hyperpolarization □ K continues to leave cell, leads to overshoot, eventually the K gates close ○ 3 factors that impact speed of an axon, increasing firing rate ▪ Size of axon ▪ Size of myelination ▪ Heat ○ Note: ▪ Pain fibers usually don’t have myelin sheaths - Axon terminal ○ Communication b/w neurons ○ Steps 1) AP arrives 2) Influx of Ca through Ca voltage-gated channels 3) Exocytosis of neurotransmitter-containing vesicles into synaptic cleft 4) Binding of ACh to post-synaptic membrane channel 5) Influx of Na 6) Generation of AP Exam 1 Page 3