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Nerve Impulses

Nerve Impulses. How does an impulse travel along a nerve pathway? Fill in your notes as you go. Effector Interneuron Motor neuron Receptor Sensory neuron Stimulus. C. B. F. D. E. A. Nerve impulses have a domino effect.

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Nerve Impulses

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  1. Nerve Impulses

  2. How does an impulse travel along a nerve pathway? Fill in your notes as you go. Effector Interneuron Motor neuron Receptor Sensory neuron Stimulus C B F D E A

  3. Nerve impulses have a domino effect. Through a chain of chemical events, the dendrites pick up an impulse that’s shuttled through the axon and transmitted to the next neuron.

  4. The entire impulse passes through a neuron in about 7 milliseconds- faster than a lightning strike.

  5. NaK pumps in the cell membrane actively transport 3 Na+ ions out of the cell for every 2 K+ ions pumped into the cell The result- the interior of the cell is negatively charged with respect to the exterior- polarization Step 1Resting Potential(the nerve fiber is not sending a signal)

  6. A threshold stimulus is received. (the stimulation level that must be exceeded to elicit a nerve impulse) Na+ channels in the membrane open and Na+ diffuses inward depolarizing the membrane Step 2 Depolarization

  7. What charge are sodium ions? • + • What will happen to the charge inside of the neuron? • It will become more +

  8. K+ channels in the membrane open K+ diffuse outward, repolarizing the membrane Step 3Repolarization

  9. The resulting action potential causes a local bioelectric current that stimulates adjacent portions of the membrane The wave of action potential travels the length of the nerve fiber as a nerve impulse Step 4Action Potential

  10. Summary of Nerve Impulse • Nerve impulse summary video

  11. Dramatizing an Action Potential 2. What happens to the charge during an action potential? 1. What is the name of the stimulus that causes an action potential? +++ ------- +++ ---- +++ ---- Threshold stimulus!!!! +++ ------+++------++++ +++ ------- +++ ---- +++ ---

  12. Dramatizing an Action Potential 3. During rest, what is the charge on the outside of the cell membrane? Resting 1. What part of the neuron does this rectangle represent? Neuron Cell Body +++ ++++ +++ ++++ +++ 2. What branch is this? Axon +++ ++++ +++ ++++ +++ ++

  13. Monday 12/11/17 • Warm-up (complete hand out) • Review • Synapse – structure and function • Project time

  14. Summary of Nerve Impulse

  15. Synaptic Transmission • Communication between a neuron and an adjacent cell occurs by neurotransmitters • Synapse • The site of communication between a neuron and another cell, such as another neuron or a muscle cell • Synaptic cleft: • Gap between two cells • Neurotransmitters diffuse across the gap • In the case of two neurons, the presynaptic neuron sends a message to the postsynaptic neuron

  16. The Synapse

  17. Structures of the synapse 1 Presynaptic cell 2 Synaptic knob 3 7 8 4 6 5 Postsynaptic cell Axon, Dendrite, Mitochondria, Neurotransmitter, Receptor site, Synaptic cleft, Synaptic knob, Synaptic vesicle

  18. What’s happening? Arrival of the nerve impulse

  19. Arrival of the nerve impulse Opening of the calcium channels Binding of Ca2+ to synaptic vesicles, neurotransmitter released into the gap Neurotransmitter binds to receptor Na+ enter the Ligand-gated channel Action potential generated in postsynaptic neuron

  20. The Neurotransmitter synapse animation

  21. Tuesday 12/12/17 • What are the events/steps that occur in the synapse as the message is sent from one neuron to the next?

  22. Synaptic transmission • Inhibitory synapse • Binding of neurotransmitter opens different ion channels • Less likely a threshold stimulus will be reached in postsynaptic cell • Cell’s interior becomes more negatively charged than usual • Cell will require larger than usual excitatory transmitter to reach threshold Excitatory synapse • Binding of neurotransmitter to receptor opens Na+ channels • Allows Na+ to enter • Increase likelihood a nerve impulse(action potential) will begin in postsynaptic cell

  23. Something else to think about….. The synaptic knobs of a thousand or more neurons may communicate with the dendrites and cell body of a single postsynaptic neuron. What will happen if both excitatory and inhibitory signals are received?

  24. Summation of Input from Excitatory & Inhibitory Synapses • As many as 10,000 synapses with other neurons at the same time • Some with excitatory effects, others with inhibitory effects • Summation (combined effects) on neuron at any given moment determines if action potential is generated. • Integration of input gives nervous system fine control over responses

  25. Removal of Neurotransmitter • After released, neurotransmitter quickly removed so their effects are temporary • If not removed, they continue to excite or inhibit the postsynaptic membrane indefinitely • Disposal: two ways

  26. Wednesday 12/13/17 • What are the two ways for the removal of a neurotransmitter from the synaptic cleft

  27. Roles of Different Neurotransmitters • There are dozens of neurotransmitters • Some neurotransmitters produce different effects on different types of cells • Example: acetylcholine • Acts in both the PNS and the CNS • Released at every neuromuscular junction • Myasthenia gravis: autoimmune disease that attacks the acetylcholine receptors at neuromuscular junctions, resulting in little muscle strength

  28. Roles of Different Neurotransmitters • In the CNS, different neurotransmitters are associated with different behavioral systems • Norepinephrine regulates mood, hunger, thirst, and sex drive • Serotonin promotes a feeling of well-being • Dopamine regulates emotions and complex movements

  29. Presentation 12/14-12/15, Paper 12/18 • Present abbreviated version of your 20-30 minute routine (approx. 10 min) • Either present in person OR submit video BEFORE class (night before or by 7:45am the morning of) • You can use “pretend” weights, equipment, or machines BUT you need to clarify what you are using (name of equipment and the weight you are using) • All of the written work/components of the project are due at the beginning of class on Monday 12/18/17. NO electronic submissions (otherwise automatic 50% deduction in grade) • Check to make sure you have all components (see hand out) • Check spelling, grammar and punctuation (points will be deducted) • DO NOT wait until the last minute to print your paper! Too many things can (and often do) go wrong. • NO late submissions accepted

  30. Dendrite neurotransmitters receptor Na+ receptor Axon synapse Dendrite Cell Body Cell Body Cl- Presynaptic Neuron Synaptic knob Postsynaptic Neuron

  31. Explain the function of ATP in muscle contraction: • ATP binds to myosin head, allowing myosin heads to disengage from actin • Myosin heads split the ATP molecules to ADP and inorganic phosphate. • The energy released from splitting the ATP allows the myosin heads to swivel in preparation to form the cross-bridges. • Aerobic exercises initiate: • the development of new blood vessels to muscles • the development of more mitochondria to facilitate energy use • An increase in muscle coordination • Improvement of digestive tract movement • An increase in the strength of the skeleton by exerting force on the bones • Cardiovascular and respiratory system improvements that help muscles to function more efficiently

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