Neurophysiology 2 PDF

NEURONS conducting cells of NS ; processesa transmits info. celectrical chemical...

NEURONS conducting cells of NS ; processesa transmits info. celectrical chemical structure : · some cell body contains organelles essential for survival dendrites short , highly branched ; receives info · from other neurons · long , single axon carries electrical signal (AP) to target common in CNS vara commoninSenT leg sight sound , types :. , S Mell) 1 bipolar neuron I long dendrite, I some , I long axon. 2 unipolar neuron dendrites & axon continuous, some to one side. multipolar neuron 3 multiple short dendrites, single long axon  NEUROGLIA supports neuronal function ; X conducting cell ~ 50 % of total Is cell population types : 1. astrocytes : regulate chemical environment of extracellular space where neutrons reside in. 2 myelinating glid oligodendrocytes (CNs) & Schwann Cells (PNS) - myelinates neurons respectively. 3 microglia phagocytic role Cengulf cell debris/wasted 4. ependymal produces CF ↳ found in ventricles of brain NEURAL COMMUNICATION nerve a muscle cells = excitable +issue v neurons produce , 2 contracts upon receiving process , transmit ventral signal & surface & receive electrical signals  polarisation membrane potential not Omi creating membrane potential of neuron = - 70mV ; polarised ( depolarisation membrane potential ( 70) - becomes less-re repolarisation potential returns to resting potential after depolarising huperpolarisation potential more polarised - ve than resting potential RESTING MEMBRANE POTENTIAL + 1. NatK pump constantly working ; pumps Nat Nathigh ICFiKthigh) + out & K into cell (ECF ; , +. Nat & K 2 move down conc. gradients ; act of each ion moving in out is Ek+ = - 90mV , ENat =+ 60m equilibrium potential +. K exerts dominant 3 effect on resting potential ; membrane more permeable to k + ↓ closer to Ekt * membrane resting potential due to conc. diff of Nat & K + inside & outside cell  MEMBRANE CHANNELS regulated by membranepotential electrical signals produced by changes in ion movement across plasma membrane open/close & physical force (touch sensation ; in response to chemicals/ e.. stretch g neurotransmitters ↓ response to temp. GRADED POTENTIAL local changes in membrane potential occur in varying magnitude degree # Ap ; all or none only spreads throughout dendrites & soma ; X travel across axon Conly AP travels across axon) spreads by passive current flow * if graded potential crosses threshold > Apgenerated & travels across axon  ACTION POTENTIAL brief , rapid , large change in membrane potential call or none ; no magnitude changes in membrane permeability & on > Ap movement propagated from axon hillock to axon terminals VOLTAGE-GATED Nat &K +CHANNEL onration gate! closed state V W V inactivation both activation gate open, open gate open, inactivation activation gate closed gate closed 1. resting potential (-70mv) ; all voltage-gated channels closed (Nat channel in closed state; closed but capable of opening 2. At threshold ; Nat channel opens (activated state. Nat rushes into cell 3 (high Nat conc ECF) ; to + 30mV. in rapid depolarisation Crising phase of APC (delayed opening triggered & + 4. Nat channel inactivated at peak ; K channel opens V threshold) slowclosing triggered at threshold 5. K+ leaves cell K+ couc ICF) ; resting potential (falling of 5 (high. in repolarisation to phase AP). Not channel reset 6 to 'closed' state at return to resting potential. Kt still 7 exiting cell >huperpolarization of cell (-80mv) [K + channel 'Slow'] +. 8 closed> K channel membrane returns to renting potential  + NATK Pump gradually restores conc. gradients disrupted by AP although membrane potential restored after Ap, ion distribution slightly disrupted pump has 3 high-affinity sites for Nat & 2 low-affinity sites for K + * when exposed to ICF 23 Nat from ICF bind to pump ; requires + Pi) energy CATP Nat & K + channels only found in * Nodes of Ranvier (not found in muclinated areas) TYPES OF CONDUCTION no muain contiguous conduction : Slower ; propagation of AP via segments is saltatory conduction faster ; Ap jumps from node to node (concentrated w :  SYNADSES synapse : junction btw neurons electrical synapse : neurons connected directly by gap junctions not common in humans * chemical synapse : chemical messenger transmits info. across space btw 2 neurons V ayon terminals connects to 3 other call synaptic bodies cleft CHEMICAL SYNADSE 1. axon of presynaptic neuron 2. synaptic cleft 3. dendrite of postsynaptic neuron SYNAPTIC TRANSMISSION 1 depolarisation of presynaptic terminal ; opens voltage-gated cast channel > - contains. 2 influx of cast into presynaptic terminal neurotransmitters. 3 Ca2+ signals docking of synaptic vesicles to docking protein Cacetylcholine) 4. release of neurotransmittern. Diffusion of neurotransmitters across synaptic 5 (chemicallygated ion channel) into synaptic cleft cleft ; binds w/ receptor on postsynaptic terminal graded results in lacctulcholine broken down by acetylcholinesterase after potential  generation generation of IPSP SYNAPSES & NEURONAL INTEGRATION of EPSP graded - M potentials brings closer to excite threshold some synapses , others inhibit postsynaptic neuron O moves further from threshold neurons linked through converging & diverging pathways V V many neurons one axon sunapsing on branches into I neuron many axon terminals ; synapses on many other neurons I