Unformatted text preview: 2/9/2010 BIOL 260: Human Physiology Human
Spring 2010 Spring W, Feb. 10, 2010 Feb. www.smccd.edu/accounts/staplesn/biol260
1. Pre-Lab Writeups: Be sure to prepare before each Monday Lab W riteups Be before each Monday or Wednesday labs (for WHOLE week!)!! or Wednesday
– (What? Why? How? are we doing in the lab??) 2. THIS Week: Ex. 3: PhysioEx, Finish Ex. 4?, and Ex. 2. PhysioEx Ex. and Ex.
• Check that ALL of your GROUP data is entered in my Check Excel Spreadsheet!! This will be posted by TONIGHT Excel • (Nerves Report #2 Due week of 2/22) • NEXT WEEK: Open lab on Wednesday!!! 3. Quiz #1 due Tonight !!! Quiz
• WebAccess!! (http://smccd.mrooms.net/) • Read directions CAREFULLY!!!! 1. Describe and diagram how sodium and potassium permeabilities are altered to Describe permeabilities are establish resting membrane potentials, and to cause depolarizations….. depolarizations 2. Ch. 8: Outline or diagram the general organization of the nervous system into its central tem and peripheral pathways and subpathways. Include inputs, outputs, and target organs. and and subpathways 3. Diagram and compare the cell structures of sensory/ afferent neurons, CNS Diagram interneurons, and efferent neurons. interneurons REVIEW TODAY: Students should be able to…...
1. Compare and contrast 4 characteristics of graded potentials and action Compare graded and potentials. (re: initiation and conduction) potentials 2. Describe and diagram the sequence of events leading from neuron Describe stimulation, to Action Potential production, conduction, and release of Action conduction, neurotransmitter at axon termini. neurotransmitter 3. Explain what causes (what is happening to ion channels?) the Relative Explain and Absolute Refractory Periods following an AP. Refractory 4. Describe and diagram 2 ways to increase speed of neural conductance, Describe increase and diagram the movement of ions during saltatory conduction. saltatory 1 2/9/2010 Trigger Zone: Trigger
Sub-/Supra-Threshold Graded Potentials Sub
Diminishes to Diminishes subthreshold by the subthreshold by time it reaches TZ time Still SupraStill threshold threshold when it reaches TZ reaches Figure 8-8b: Subthreshold and suprathreshold graded potentials in a neuron 8b: suprathreshold graded Action Potential Stages: Overview a) a) b) b) c) c) "All or none" "All Rising/Falling phases Rising/Falling Signal does not Signal diminish over distance diminish Figure 8-9: The action potential 9: 2 2/9/2010 8.4) Membrane & Channel 8.4) Changes during an Action Potential Action
1. Initiation 2. Depolarization 3. Signal peak 4. Repolarization A. Action Potentials: Voltage-Gated Gated Na+ Channels Na+ 2 gates: activation, gates: inactivation (slow!) inactivation
Figure 8-10: Model of the 10: voltage-gated Na+ channel voltage channel 3 2/9/2010 B. Regulating the AP B.
1. Positive feedback loop – keeps Na+ channels keeps opening down axon opening 2. Absolute refractory period – Na+ Ch. Reset to resting 3. Relative refractory period – many, not all Na+ Ch many, reset; stronger depol’ng graded potential needed depol graded
Figure 8-11: Ion 11: movement during an action potential Regulating the AP Regulating
• Action Action potentials will not fire during an Absolute Refractory Period. Period • Restricts RATE Restricts and DIRECTION of AP’s. of Figure 8-12: 12: Refractory periods 4 2/9/2010 C. Frequency of Action Potentials • Firing rate:
– "Wave" of APs – triggered by most "Wave" APs triggered suprathreshold graded potentials suprathreshold – Proportional neurotransmitter (NT) release – Stronger GP initiates more APs & Stronger APs releases more NT releases Frequency of Action Potentials
Figure 8-13: Coding for stimulus intensity 13: 5 2/9/2010 D. Conduction of Action D. Potentials Potentials
• Kinetic energy, repulsion Kinetic
– Depolarizes ahead Depolarizes • Drives AP to terminal
– Positive feedback loop! Figure 8-15ab: 15ab: Conduction of action potentials potentials Conduction of Action Potentials Figure 8-15cd: Conduction of action potentials 6 2/9/2010 Conduction of Action Potentials
• Refractory periods prevent backflow of AP Refractory toward cell body toward Na+ ch. closed Na+ ch K+ ch. opened K+ ch Figure 8-15e: Conduction of action potentials Action Potential http://www.blackwellpublishing.com/matthews/channel.html http://www.blackwellpublishing.com/matthews/actionp.html (http://www.blackwellpublishing.com/matthews/animate.html) 7 2/9/2010 E. Speed of Conduction: Determinants
1. Larger diameter = faster conduction (↓R) Larger diameter 2. Myelinated axon = faster conduction; axon ↓ leakage of ions/current.
a) Salutatory Conduction b) Disease damage to myelin 3. Chemicals that block channels that block
a) Neurotoxins – block Na+ or Ca+ channels Neurotoxins b) Anaesthetics – block Na+ channels 4. Alteration of ECF ion concentrations Alteration ECF 1. Myelination Speed! 1. Myelination Animals with complex nervous Animals systems (vertebrates) systems Multiple, MYELINATED Multiple, axons per Nerve fiber. axons • Demyelination diseases: diseases:
• eg: Multiple Sclerosis Multiple • Weakness, fatigue, loss Weakness, of motor control of Figure 8-17b: Axon diameter and speed of conduction 17b: 8 2/9/2010 2. Saltatory Conduction
• “Skate Skate Skate GLIDE……” Skate Skate • Continual/periodic Na+ influx refreshes Continual/periodic AP strength does NOT diminish!! Fig. 8-18: 18: Saltatory conduction
http://www.brainviews.com/abFiles/AniSalt.htm http://www.blackwellpublishing.com/matthews/actionp.html 3. Electrical Signals: 3. Chemical Factors Chemical
Effect of extracellular potassium (-kalemia) Effect extracellular concentration of the excitability of neurons
Less potassium leakage Less out, but slow repolarization. out, HyperK HypoK More potassium leakage out. Fig. 8-19 9 2/9/2010 8.5) Cell to Cell Conduction: Cell The Synapse The
1. Electrical synapses: gap junctions
a) Very fast conduction Very fast b) Example: cardiac muscle 2. Chemical Synapses: 3 components – components
a) Pre synaptic terminal
1) Synthesis of Neurotransmitters 2) Ca2+ releases Neurotransmitters Few to 150K Few per target cell! per b) Synaptic cleft c) Postsynaptic cell: Neurotransmitter receptors Neurotransmitter in membrane in A. The Synapse: Structure
Figure 8-20: A chemical synapse http://www.mind.ilstu.edu/flash/ synapse_1.swf http://outreach.mcb.harvard.edu /animations/synaptic.swf 10 2/9/2010 B. Synapse Mechanism
VG, Ca2+ Channels “Kiss and Run” pathway? Figure 8-21: Events at the synapse C. Acetylcholine synthesis Figure 8-22: Synthesis and recycling of acetylcholine at the synapse 11 2/9/2010 D. Neurocrines D. Neurocrines
1. 2. 3. Neurotransmitters Neuromodulators Neurohormones / antagonist ß blockers Neurocrines Caffeine = antagonist Table 8-4-2: Major Neurocrines 12 2/9/2010 E. Multiple Receptors Modify E. Signal Signal
1. Amplification – depolarization (EPSP); );
• trap K+ inside (less out), or open Na+ Channels. 2. Inhibition – hyperpolarization (IPSP); );
• open Cll- influx channels, extra K+ efflux, less open C efflux, + influx. Na Na 3. Duration
a) Fast – channel opening. (direct channel activation) Fast channel (direct b) Slow – require protein synthesis; use Slow require secondary messengers. (indirect channel activation) (indirect Multiple Receptors modify signal
nACh, Glu AMPA Glu mACh, Adr Adr Figure 8-23: Fast & slow responses in postsynaptic cells 13 2/9/2010 F. Inactivation of Neurotransmitters F. (Termination of Signal) (Termination
1. Recycled 2. Enzyme degradation 3. Diffuse away
Figure 8-24: Inactivation 24: of neurotransmitters 8.6) Integration of Signals 8.6)
1. Information transfer at each exchange 1.
a) Signal can be lost b) Signal can be enhanced 2. Divergence – one cell to many 3. Convergence – many cells to one many 14 ...
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- Spring '09
- Physiology, Action Potentials, D. Potentials Potentials