1. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Functional Properties of Neurons  Irritability  Ability to respond to stimuli & convert to nerve impulse  Conductivity  Ability to transmit an impulse to other neurons, muscles, or glands

2. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses: Electrical Conditions  Resting neuron  The plasma membrane at rest is polarized  Fewer positive ions are inside the cell than outside the cell so cell interior is more negative  Major ion inside cell is K+  Major ion outside cell is Na+  As long as inside remains more negative than outside, neuron stays inactive

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulse: Action Potential & Generation  Many types of stimuli excite neurons: light, sound, pressure, smell, temperature, neurotransmitters  Most neurons are excited by neurotransmitters released by other neurons  Result is always the same:  Na+ channels open & Na+ diffuses into the cell  This causes Depolarization (inside becomes more positive)  This causes the neuron to transmit a signal called an Action Potential (AKA Nerve Impulse)

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9a–b

5. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulse: Action Potential & Generation  Action potential  If the action potential (nerve impulse) starts, it is propagated over the entire axon  Impulses travel faster when fibers have a myelin sheath

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9c–d

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulse: Action Potential & Generation  Repolarization  K+ ions rush out of the neuron after Na+ ions rush in, which repolarizes the membrane  The sodium-potassium pump, using ATP, restores the original ion concentrations  This must happen before the neuron can conduct another impulse

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9e–f

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses  Impulses are able to cross synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrite  Nerve impulse  neurotransmitter  nerve impulse  neurotransmitter  effector  “Electrochemical Event” because impulse is electrical but next neuron is stimulated by a neurotransmitter, which is chemical

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Neurotransmitter broken down and released Ion channel opensIon channel closes

11. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 1 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 2 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Vesicle fuses with plasma membrane Synaptic cleft Ion channels Receiving neuron Transmitting neuron

13. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 3 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron

14. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 4 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron

15. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 5 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Ion channel opens

16. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 6 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Neurotransmitter broken down and released Ion channel opensIon channel closes

17. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 7 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Neurotransmitter broken down and released Ion channel opensIon channel closes

18. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Reflex Arc  Reflex—rapid, predictable, and involuntary response to a stimulus  Occurs over pathways called reflex arcs  Reflex arc—direct route from a sensory neuron, to an interneuron, to an effector

19. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Reflexes and Regulation  Somatic reflexes  Stimulation of skeletal muscles  Example : When you move your hand away from a hot stove

20. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Reflexes and Regulation  Autonomic reflexes  Regulate activity of:  Smooth muscle  Heart and blood pressure  Glands  Example: saliva secretions, change in eye pupil size, digestion, excretion, blood pressure, sweating

21. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 5 Elements of a 3 Neuron Reflex  1. Sensory Receptor (reacts to a stimulus)  2. Sensory Neuron (afferent)  3. Integration Center (CNS)  4. Motor Neuron (efferent)  5. Effector Organ (stimulated to react)

22. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Reflex Arc Figure 7.11a Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Effector Sensory neuron Motor neuron Integration center (a)

23. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Reflex Arc Figure 7.11a, step 1 Stimulus at distal end of neuron Skin Receptor (a)

24. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Reflex Arc Figure 7.11a, step 2 Stimulus at distal end of neuron Skin Receptor Sensory neuron (a)

25. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Reflex Arc Figure 7.11a, step 3 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Sensory neuron Integration center (a)

26. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Reflex Arc Figure 7.11a, step 4 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Sensory neuron Motor neuron Integration center (a)

27. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Reflex Arc Figure 7.11a, step 5 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Effector Sensory neuron Motor neuron Integration center (a)

28. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11b–c Spinal cord Sensory (afferent) neuron Inter- neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (quadriceps muscle of thigh) Effector (biceps brachii muscle) Synapse in ventral horn gray matter (c) (b)

29. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11b, step 1 Spinal cord Sensory receptors (stretch receptors in the quadriceps muscle) (b)

30. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11b, step 2 Spinal cord Sensory (afferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) (b)

31. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11b, step 3 Spinal cord Sensory (afferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Synapse in ventral horn gray matter (b)

32. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11b, step 4 Spinal cord Sensory (afferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Synapse in ventral horn gray matter (b)

33. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11b, step 5 Spinal cord Sensory (afferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Effector (quadriceps muscle of thigh) Synapse in ventral horn gray matter (b)

34. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11c, step 1 Spinal cord Sensory receptors (pain receptors in the skin) (c)

35. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11c, step 2 Spinal cord Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)

36. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11c, step 3 Spinal cord Inter- neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)

37. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11c, step 4a Spinal cord Inter- neuron Motor (efferent) neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)

38. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11c, step 4b Spinal cord Inter- neuron Motor (efferent) neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (biceps brachii muscle) (c)

39. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Simple Reflex Arc Figure 7.11b–c Spinal cord Sensory (afferent) neuron Inter- neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (quadriceps muscle of thigh) Effector (biceps brachii muscle) Synapse in ventral horn gray matter (c) (b)

40. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Types of Reflexes and Regulation  Patellar, or knee-jerk, reflex is an example of a two-neuron reflex arc Figure 7.11d