Your Nervous System

1. Your Nervous System

2. Engage • Lorenzo’s Oil Discussion

3. Explore • Quick Communications • Neuron Models

4. ExplainNervous System • Four Major Parts of the Nervous System • Neurons • Nerves • Brain • Spinal Cord

5. Two Major Nervous System • Central Nervous System • Peripheral Nervous System • Nerves and Neurons are found in both and this is where we will begin

7. Neuron”Nerve Cell” • Functional Unit of Nervous System • Cell Body – center part of the cell containing the nucleus • Dendrites • Carries messages toward the cell body. • Fingerlike projections • Axon • Carries messages away from the cell body. • Elongated extension of the cell body • End of the axon is divided into fingerlike projections called axon terminals.

8. Neuron Model • To check for understanding you will need to construct a neuron model that contains dendrites, a cell body (soma), axon, and axon terminals.

10. Types of Neurons • Sensory Neurons – picks up the stimuli (nerve impulse) and carries it to the spinal cord and brain. • Interneurons- Found within the brain and spinal cord. Relays the message between the sensory neurons and the motor neurons. • Motor Neurons – transfers impulses away from the brain to the spinal cord

11. How Neurons Work • Reception • Receptors in the skin sense stimuli • Transmission • Sensory neurons transmit the touch message • Data Interpretation • Information is sorted and interpreted • Transmission • Motor Neurons transmit a response message to a muscle • Response • Muscles are activated causing a response

12. Impulse Transmission • Start with a RESTING neuron – one NOT transmitting an impulse • Plasma membrane controls [ ] of ions inside the cell • Na+ and K+ on both sides of membrane • Na+ Higher Conc Outside • K+ Higher Conc Inside • Remember Na+/K+ ATPase Pump

13. Sodium Potassium Pump

14. How an Impulse Travels • Stimulus excites a neuron • Na+ channels open, Na+ build up inside • Inside more + that outside • Change in charge (depolarization) • Membrane immediately behind depolarization returns to RESTING STATE • RESTING STATE – inside negative, outside positive

15. 1. Resting State • A neuron is not conducting an impulse • The K+ concentration is much higher inside the cell than out • The Na+ concentration is much higher outside the cell than in

16. 2. Depolarization • A nerve cell is stimulated • Membrane becomes permeable to Na+ for an instant and they quickly move into the cell • The inner surface of the cell membrane is now more positively charged then the outside.

17. 3. Repolarization • When the cell membrane becomes depolarized, K+ automatically leaves the cell until the cell is back to its resting state.

18. 4. The Impulse Travels • “Wave” of depolarization – transmission of an impulse along length of axon • All or None Principle – must reach a threshold level or the impulse dies • Covered by a white covering called a myelin sheath (Schwann Cells), an insulator • Myelin sheath causes the ion exchange to occur only at the nodes which speeds up the process • For a short time after depolarization; the neuron cannot be stimulated

19. 5. Transmission Across a Synapse • Neurons do not actually touch. This gap between the two cells is call a SYNAPSE • Impulses are carried across a synapse by chemical messengers called neurotransmitters. • Approximately 30 different neurotransmitters; do one of two things: • Stimulate the action potential in a second cell • Inhibit the action potential in the next cell

20. 6. Refractory Period • The period of time it takes a neuron to return to its resting potential after being stimulated • A neuron cannot be stimulated during this period • This period of time is about 0.0004 of a second

22. Elaboration • Neurotransmission: Nifty Neurons and Muscle Messages

23. EvaluationParts of Nervous System • List the Four Major Parts of the Nervous System • Neurons • Nerves • Brain • Spinal Cord