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Human Physiology H5
Handout 5 Neurophysiology
| Question | Answer |
|---|---|
| The BIG Picture: 2 Main parts of the nervous system | CNS and PNS |
| Central Nervous System | CONTROLS BRAIN AND SPINAL CORD; many ways to brkdwn system |
| Periferal nervous system | controls EVERYTHING ELSE; several ways to brkdwn system; 3 major divisions Somatic, Autonomic and Enteric |
| 3 Major divisions of the PNS | Somatic, Autonomic and Enteric |
| Somatic | CONSCIOUS BODY: SENSORY OR MOTOR funx were ARE AWARE OF |
| Somatic Sensory | temp, pain, touch, smell, sight, sound, taste, pressure, vibration |
| Somatic Motor | Knee jerk response= SKELETA MUSCLES+ Somatic motor neurons apply to ALL SKELETAL MUSCLE (NOT SM or CM) |
| Autonomic | UNCONSCIOUS BODY: Sensory and Motor funx we are NOT AWARE OF |
| Autonomic Sensory | pH, BP, Oxygen saturation, glucose levels |
| Autonomic Motor | pSNS and SNS; SM, CM and glands |
| Enteric | The gut; network of neurons entirely located in the GI tract.NO AXON exits or connects to CNS-entirely seperat; essential for health. |
| Cells of the NERVOUS SYSTEM | neurons and glia |
| Neurons | primary role is in signaling that CNS and PNS does. Functionally, Sensory to CNS, motor from CNS; afferent neurons, interneurons and efferent neurons' produce ELECTRICAL signals and its unique anatomy allows complex connex to develop to allow processing |
| Afferent Neurons | Sensory TO CNS |
| Interneurons | entire cell anatomy IN CNS |
| Efferent neurons | Motor FROM CNS; somatic and autonomic directly controlling an effecor EX. Skeletal muscle, gland, SM and CM |
| Glia | Primary role is to SUPPORT the neuron; 10x as many glial cells as neurons in the nervous system |
| Anatomy of a Neuron | cell body, dendrites, axon, axon terminals |
| Cell body | same as other cells |
| Dendrites | Specific to neuron; RECEIVE INPUT fromother neurons; "INPUT PORTION" of a neuron; each dendritic spine has a synapse |
| Axon | 1 per neuron; have collaterals |
| Collaterals | branch off an axon to two diff localities |
| Axon terminals | form presynaptic end of a synapse; OUTPUT SIGNAL happens across the axon to the axon terminal; dendrites or effector has the postsynaptic synapse |
| Axon Hilloc | decision point area of a neuron to produce produce an AP signal or not |
| Axonal transport | axons and axon terminals do not contain ribosomes or ER; travel happens in both directions: materials are SENT TO THE TERMINAL via ANTEROGRADE transport; materials RETURNED FROM THE TERMINALS via RETROGRADE transport; trans. of vesicles and mitochondria |
| Anterograde transport | TOWARDS synapse= AWAY from axon |
| Retrograde transport | FROM synapse= Back to axon |
| Glial cells | Provide structure and stability, metabolic and nutritional support, maintenance of homeostasis for ECF around neurons and involved in nervous system development and repair |
| 4 types of Glial cells in CNS | Oligodendrocytes, Astrocytes, Microglia, and Ependymal cells |
| Glial cells are involved in myelination (layer of insulation) | PNS = Schwann cells and satellite cells CNS = Oligadensdrocytes |
| Neurophysiology | is the study of how neurons engage n signaling; electrical signaling within a single neuron, chemical signaling (neurotransmitter) btwn 2 neurons at the synapse and how networks of neurons funx to control behavior/tasks |
| Neurons (and musce) are EXCITABLE cells | an excitable cell can undergo transient, rapid changes in its MP, electrical signals are prod. by changes in ion mvmnt across cell membranes thru gated chnlsa dn neuron use the elect. sigs. to recieve, process, initiate adn transmit msgs |
| electrical signals | result from ion mvmnt(charged particles) in the plasma membrane thru gated chnls |
| receive information | as a response to any stimulus |
| transmit messages | like an AP along an axon |
| WHAT DETEERMINES THE RMP? | 1. Chemical force adn concentration gradient of ions 2. 2. Selecttive permeability at rest to those ions Electrical force will act towards equilibrium |
| Nernst equation | equilibrium potential Na = +60mV K = -90mV Cl = -70mV Ca = +120mV |
| Concentration distribution | Na = high outside and low inside K = high inside and low outside Cl = high inside and low outside Ca = high outside and low inside |
| Effects of changes in ions w/ concentration distribution | ? |
| Ion movement = Electrical signal | depolarization and hyperpolarization |
| depolarization of an electrical signal | More + from less; less negative |
| hyperpolarization of an electrical signal | increase in negativity from rest |
| Reminder: | Concentrations aren't changing to any significant degree |
| Gated channels control ion permeability | signals happen by addt'l chnls coming into play; there are 3 general classes of gated channels, channels vary, and there are isoforms of most channels |
| 3 general classes of gated channels when initiated by Graded potentials | if Na gated chnls = Na IN = DEPOOLARIZING (more +) Response is to open CA chnls = depolarization (more +) if gated K cnl = K rushes OUT = HYPERPOLERIZING (more -) |
| Channels can vary by: | conductance, threshold and temporally |
| conductance | how many ions move thru chnl-diff conductances |
| threshold | minimum change input is req'd to open gate; if voltage gated then minimum depolarization change toopen a voltage sensitive gate = 15mV. Threshold less than that will NOT OPEN |
| Channels | ARE CLOSED AT REST |
| Temporally | Timing: activation or inactivation |
| Activation | up until it opens |
| Inactivation | remain open til shut |
| Not all electrical signals are the same (2 kinds) | Graded potential and Action potentials |
| Graded potentials | SHORT distance communication; varying magnitudes so changeable, vary in strength; IN DENDRITES AND CELL BODY; RECIEVE INFO= INPUT signals = grades potential INPUTS |
| Action Potential | LONG distance communication, very fast, NOT variable in magnatude, always same bo matter how strong; IN AXON |
| Graded Potentials ( powerpoint) | Initiated by a stimulus opening ion (ligund gated)chnls STRONGER STIMULUS = LARGER GP GP spread by passive current flow GP die out over short distances (decay) A GP may be depolarizing or hyperpolarizing |
| graded Potentials continued | GP spread from location of synapse in both directions TOWARD AXON HILLOCK, some of charge will leak so loss of charge: SIGNAL DECAYS W/DISTANCE; SIZE OF RESPONSE CHANGES DEENDING ON SIZE OF STIMULUS |
| GP's losse strength but may SUMMATE | GP's ;ose strength as they move away fromteh location of stimulus b/c they leak charge, GP's EPSPs andIPSPs) are summed at the axon hillock, if summation is > or equal to threshold = AP subthreshold or suprathreshold |
| EPSP | Excitatory Postsynaptic Potential;Excitatory is response is on postsynaptic side = postsynaptic GP; if depol referred to as excitable b/c it influenced electrical status@ hillock = threshold is reached to prod. an AP |
| IPSP | Inhibitory Postsynaptic Potential:happens in same way butisa hyperpolarizing event as in a ligund gated Cl chnl decays with travel so lowers (makes more negative) at hillock so LESS likely to reach threshold = NO AP |
| Summation | ADD UP to depolarization or hyperpolarization in 2 ways: Temporal or Spacial |
| Temporal Summation | over time; diff time summation; individual effort |
| Spacial Summation | Multiple inputs at the same time (hundreds); summate together; same time summation |
| Action Potentials (powerpoint) | initiated by GPs that activate voltage gated channels to threshold to open gate, APs DO NOT vary in magnitiude (-100mv depol), AP's DON NOT vary in duration (1ms in a neuron) adn APs DO NOT degrade w/distance |
| AP continued | initiated GP arriving at Axon Hillock; Axon has VGCs reaching threshold to open gate, dendrited do not; VGCs first location is at the AH which makes the decision to open or not; |
| Phases of the AP | happen b/ of specific VGCs; depolarization, repolarization and hyperpolarization 2 types necessary: VG Na chnls and VG K chnls |
| VG Na chnls 3 states of existance: | resting state = INact: OPEN and ACT: CLOSED, so gate is CLOSED open state = BOTH GATES OPEN, both respond to depol but diff temoral characterisitics = Activation gate fast to open and inactivation state = INact: closed and ACT: open, so is SLOW TO CLOSE |
| AP phases are determined by specific VGCs | depolarization = VG Na chnl w activated or inactivated gates both sensitive to voltage, repolarization = VG K chnl and hyperpolarization = VG K chnl |
| VG K chnl | draw it from power point |
| Action Potential initiation | APs are initiated at the AXON HILLOCK. Why? 1st time we have VGCs |
| Refractory Periods DRAW IT TOO | stubborn; a time ehen the neuron CANNOT be triggered or is less likely to happen or inititate; Absolute refractory period, and relative refractory period |
| ABSOLUTE refractory period | NO AP POSSIBLE; produces a limit of APs= about 1000 per sec but not faster |
| RELATIVE refractory period | MORE DIFFICULT to get an AP; requires a larger stimulus thsn normal to reach threshold, related to al things driving the cell to become more negative (-) to threshold, ENDS when we get back to RMP |
| When does the relative refractory period end? | when we get back to RMP |
| In Absolute refractory period: | ALL VG Na chnls are open, at the peak they are inactivated so cannot produce another AP again until the RMP |
| In Relative Refractory period: | at about -50 VG Na chnsl will go from inactivated to resting, and then we can have a second AP |
Created by:
Lkellyfly
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