1. Pages 234-239

2.  http://highered.mheducation.com/sites/007 2495855/student_view0/chapter14/animatio n__the_nerve_impulse.html http://highered.mheducation.com/sites/007 2495855/student_view0/chapter14/animatio n__the_nerve_impulse.html

3.  Neurons have two functional properties ◦ Irritatability – respond to a stimulus and convert it into a nerve impulse ◦ Conductivity – ability to transmit the impulse to other neurons, muscles, or glands

4.  When neurons are in a “resting” state: ◦ They are polarized  inside the plasma membrane is more negative than outside  more potassium (K  ) inside the cell  More sodium (Na  ) outside the cell  a gradient is created  the cell stays at rest © 2015 Pearson Education, Inc. [Na + ] [K + ]

5.  A stimulus depolarizes the neuron’s membrane  The membrane is now permeable to sodium  sodium channels open  sodium (Na  ) diffuses into the membrane  the inside becomes more positive  This is how an action potential can be initiated © 2015 Pearson Education, Inc.

6.  A nerve impulse (action potential) is generated:  If the stimulus is strong enough  If sodium influx great enough  If enough sodium enters the cell, the action potential (nerve impulse) starts and is propagated over the entire axon © 2015 Pearson Education, Inc. Na +

7.  the nerve impulse is propagated or it is not  There are no partial impulses  Repolarization:  the membrane is restored to resting potential  Negative inside, positive outside  The sodium-potassium pump restores resting potential using energy supplied by ATP  Another impulse cannot take place until the entire membrane has been repolarized © 2015 Pearson Education, Inc. K+K+ K+K+

8.  When the action potential reaches the axon terminal: 1.calcium channels open 2.vesicles containing neurotransmitters fuse with the axonal membrane 3.neurotransmitters diffuse across the synapse and bind to receptors on the membrane of the next neuron  The amount of neurotransmitter released will determine if the action potential will continue ◦ This is known as graded potential © 2015 Pearson Education, Inc.

9. Action potential arrives. Axon of transmitting neuron 1 Receiving neuron Dendrite Axon terminal Vesicles Synaptic cleft Slide 2

10. Transmitting neuron Vesicle fuses with plasma membrane. Synaptic cleft Ion channels Neurotransmitter molecules Receiving neuron Slide 3 2

11. Transmitting neuron Vesicle fuses with plasma membrane. Neurotrans- mitter is released into synaptic cleft. Synaptic cleft Ion channels Neurotransmitter molecules Receiving neuron Slide 4 23

12. Transmitting neuron Vesicle fuses with plasma membrane. Neurotrans- mitter is released into synaptic cleft. Neurotrans- mitter binds to receptor on receiving neuron’s membrane. Synaptic cleft Ion channels Neurotransmitter molecules Receiving neuron Slide 5 23 4

13.  The transmission of a nerve impulse down neuron is electrical  The transmission of a nerve impulse to next neuron is chemical © 2015 Pearson Education, Inc.

14.  Somatic reflexes ◦ Reflexes that stimulate the skeletal muscles ◦ Example: pulling hand away from a hot object  Autonomic reflexes ◦ Regulates smooth muscles, heart, and glands ◦ Example: regulation of blood pressure, glands, digestive system © 2015 Pearson Education, Inc.

15.  Reflexes are rapid, predictable, involuntary responses to a stimulus  A reflex arc can include: 1.Sensory receptor—reacts to a stimulus 2.Sensory neuron—carries message to integration center 3.Integration center (CNS) –  processes information  directs motor output 4.Motor neuron —carries message to an effector 5.Effector organ —muscle or gland to be stimulated © 2015 Pearson Education, Inc.

16. 12345 Stimulus at distal end of neuron Skin Receptor Effector Sensory neuron Motor neuron Spinal cord (in cross section) Integration center Interneuron