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Action Potential

Action Potential. Neurons have a resting potential of -70 millivolts, creating a state of polarization Neurons are surrounded by a salty liquid environment which has a high concentration of sodium ions (Na+)

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Action Potential

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  1. Action Potential

  2. Neurons have a resting potential of -70 millivolts, creating a state of polarization Neurons are surrounded by a salty liquid environment which has a high concentration of sodium ions (Na+) The inside of the neuron has some positively charged potassium ions (K+) and many other negatively charged ions The combination creates the resting potential

  3. SOURCE OF THE RESTING MEMBRANE POTENTIAL The resting membrane potential results from the concentrations of ions that are in & out of the cell and the permeability to those ions.

  4. THE RESTING MEMBRANE POTENTIAL If we measure voltage between the inside of a neuron and the outside we find that the neuron is more negative inside than outside with a potential of about - 70 mV.

  5. Nerve Conduction: The Action Potential

  6. Nerve Conduction: The Action Potential Dendrites are stimulated by axons of other neurons Na+ ions flow into the neuron by action of ion channels, making the membrane voltage more positive (depolarization) If the partial depolarization reaches - 65 millivolts (action potential threshold), the neuron fires according to the all-or-none law

  7. Action potential in ACTION!! • Stand side by side forming a ‘U’ shape • The first person should be facing the last person • Hold hands • The first person says “GO!” and squeezes the hand of the next person • When that person feels the squeeze, he or she should squeeze the hand of the next person in line. • When the squeeze has reached the last person in the line, he or she should says “STOP!”. • Record the time it took for the signal to travel the length of the line.

  8. What do we know about the nervous system? Central Nervous System Peripheral Nervous System Major Divisions Central (CNS) – the brain and spinal cord Peripheral (PNS) – the nerves connecting muscles and organs to the CNS

  9. What do we know about the Peripheral Nervous System? Nerves 3 kinds of neurons • sensory – sensory receptors • motor – connected to muscles and organs • interneurons – connection within the CNS

  10. What do we know about the Peripheral Nervous System? How many cranial nerves? How many spinal nerves? 12 pairs 32 pairs P e r i p h e r a l N e r v o u s S y s t e m Somatic Autonomic S y m p a t h e t i c P a r a s y m p a t h e t i c

  11. What do we know about the Somatic Nervous System? Brain Sensory Neuron Motor Neuron Skin receptors Interneuron Muscle Nerves to and from spinal cord Controls both voluntary muscle & reflex movements Simplest reflex Reflex arc

  12. What do we know about the Autonomic Nervous System? Pupils dilate EYES Pupils contract Decreases SALVATION Increases Perspires SKIN Dries Increases RESPERATION Decreases Accelerates HEART Slows Inhibits DIGESTION Activates Secrete stress hormones ADRENAL GLANDS Decrease secretion of stress hormones Two divisions Sympathetic Parasympathetic Controls Involuntary functions

  13. What do we know about the Action Potential? When no signal is being sent Resting potential – state of polarization Na+ is found and K+ is found creating a more charge inside & a more charge outside OUTSIDE INSIDE negative positive How many millivolts is Resting potential? - 70 mV

  14. What do we know about the Action Potential? A signal is being sent De-polarization Na+ flows and K+ flows through INSIDE OUTSIDE Ion channels Neurons fire according to what law? All or nothing

  15. Spinal Nerves Cranial Nerves

  16. Spinal Nerves: 31 Pairs Cervical: 8 C1-C7 Emerge above the vertebra for which they are named C8 Emerges between C7 and T1 Thoracic: 12 Thoracic, Lumbar, Sacral & Coccygeal spinal nerves emerge below the vertebra for which they are named Lumbar: 5 8 + 12 + 5 + 5 + 1 = 31 pairs Sacral: 5 Coccygeal: 1

  17. Spinal Nerves….

  18. Spinal Nerves

  19. Dorsal Root(Afferent=Sensory) Posterior (Dorsal) Dorsal Root Ganglion (Cell bodies of sensory neurons) Anterior(Ventral) Spinal Nerve Mixed motor and sensory. Ventral Root (Efferent=Motor)

  20. Spinal Cord Ventral Roots (Motor) Dorsal Roots (Sensory) Spinal Nerve(this is where sensory and motor mix) Dorsal Ramus(mixed) Ventral Ramus(mixed) Rami Communicantes(White ramus + Gray Ramus) Nerve Plexuses Sympathetic ganglia

  21. Just a reminder…. Intact reflexes require Intact sensory afferent nerves (coming to the spinal cord) Intact synapse within the spinal cord Intact efferent motor nerves coming from the spinal column Adequately functioning muscle. Patellar reflex = L2, L3, L4 Babinski sign = L4 to S2 Withdrawal reflex = pain sensors

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