AIM: How does the Nervous System work and how does it help the body maintain homeostasis?

• DO NOW: What is the function of the nervous system? What are the three types of neurons? What are their functions?

• Nervous System Vocabulary: neuron, cell body (soma), axon, dendrites, myelin sheath, synapse, neurotransmitter, receptor, central nervous system, peripheral nervous system, stimulus, impulse, regulation, effector, action potential, membrane (resting) potential, depolarization

• Have out HW for me to check

• Results and Discussion section due via turnitin.com on 12/23 (extended)

• HW due Tuesday pg 900 questions 1-5 and pg 905 ques 5

• Exam on Wednesday circulation, respiration and the nervous system

Function of the Nervous System• Process Information

• Stores Information

• Controls Voluntary movements

• Controls Involuntary process and actions

• Stimulus Vs Response

Parts of the Nervous System

What is Regulation?• Control and coordination of all life functions• 2 systems involved• Stimulus: change or activity in the environment

that causes a change in the organism; physical, chemical

• Receptors• Response: action or movement resulting from

a stimulus• Effectors• Impulses: electrical messages sent over a nerve

cell (neuron)

Aim: How is an action potential propagated in the nervous system?• Do Now: What is the central nervous system?

Distinguish between sensory, motor and interneurons

• Results and Discussion section due via turnitin.com on 12/23 (extended)

• HW due Tomorrow pg 900 questions 1-5 and pg 905 ques 5

• Exam on Wednesday circulation, respiration and the nervous system

Review of Do Now• Central Nervous System

– Brain and spinal cord• Sensory Neurons

– Carry signals betewen the central nervous system and a sense organ.• Motor Neurons

– Carry signals between the central nervous system and a muscle• Interneurons

– Carry signals between sensory and motor neurons• Demyelination

Neuron

Axon terminals

Myelin sheath

Nodes

Cell body

Axon

Nucleus

Dendrites

Sensory, motor, interneurons

What would you expect to happen if a person had a disease in which the myelin sheath is destroyed?

Sketch the diagram of a neuron below, and label each part AND its function. (See page 897)

Membrane Potential

Describe the difference in charge between the inside and outside of the nerve cell (a).How is this difference maintained? Explain based on the picture above (b). Be specific!

Follow-up Questions• Why is it impossible for ions to travel across the

membrane by simple diffusion? How do ions travel across the cell membrane (two ways)?

• What do you think would happen if the sodium channels in a nerve cell were suddenly opened? The potassium channels?

• What effect would each of these events have on the membrane potential?

Aim: How is an action potential propagated in a neuron

• Do Now: How does an influx of Na+ change the membrane potential? What about an influx of K+?

• Have out HW

• Test on Thursday

The Action Potential

Aim: How is an action potential propagated in the nervous system?

Cool Neuroscience Animation!

http://outreach.mcb.harvard.edu/animations/actionpotential.swf

Review Questions• How does an action potential stop, i.e., how

does a nerve cell return to its resting (membrane) potential?

• Why is an action potential an all or none event?

• If action potentials are all or none events, how does the nervous system distinguish between strong and weak stimuli?

The Action Potential

• Resting potential established by Sodium Potassium pump

• Sodium-potassium pump (3 Na+ out, 2 K+ in)

• Stimulation: Channels open Na+ in and K+ out• Threshold• Reversal of charges• All or none event• Like the Domino effect

The Synapse

Axon terminal

Synaptic cleft

Receptor

Neurotransmitter

Dendrite of adjacent neuron

Direction of Impulse

Vesicle

Axon-Junction between axon of one neuron and dendrites of another-Neuron can transfer an impulse to another cell

Electrical vs. Chemical Signaling

How would abnormal levels of neurotransmitters affect the function of the nervous system?

Questions For Review• How does the nervous system couple electrical and

chemical signaling? What events take place at the junction between two neurons?

• What is an action potential?

• Define depolarization.

• How does a neuron distinguish between a strong stimulus and a really strong stimulus?

• What is a synapse? What type of signaling takes place at the synapse?