2. Nervous System

3. Divisions Central Nervous System –Brain & Spinal Chord Peripheral Nervous System –Autonomic-involuntary –Somatic-voluntary

4. Neurons I Nerve=bundle of neurons Neurons draw and label) have: 1. Cell Body –Nucleus and organelles 2. Dendrites –Receive impulses

5. Neurons II 3. Axon –Always only 1 –Conducts impulse AWAY from cell body –Encased by Schwann cells  Myelin sheath –Nodes of Ranvier Three types of neurons- Sensory Neurons (from sense receptors to central nervous system) Interneurons (relay info to Motor neurons) Motor Neurons (From CNS to body)

6. Action Potential – Resting I Resting Potential (-70mV) –Result of unequal distribution of ions –At rest, more positive (Na+) on outside –During signal, NA+ moves inside neuron

7. Action Potential – Resting II Concentration Gradient 3 Na+ (sodium) vs. 2 K+ (potassium) Active transport-does it use energy?

8. Action Potential III How does the myelin sheath improve conductance speed? impulse jumps! between Nodes of Ranvier

9. All or none! Threshold Stimulus Subthreshold – those stimuli that are weaker than threshold (No AP)

10. Synaptic Gap Spaces between neurons Synaptic vesicles at bulb (end of axon) contain neurotransmitters Show video clip

11. Chemical Influences How might stimulants work? (Amphetamines, caffeine, nicotine) –Increase synaptic transmission  increased energy/mood, decreased appetite. Increased irritability and anxiety How might depressants work? (Alcohol, anti-anxiety drugs, heroin) –Inhibition of impulses (blocking receptors of NT Can result in depression

12. Spinal Reflexes Does not reach higher brain levels! –No thought involved 1.Receptor Stimulated 2.Sensory 3.Association neurons in spinal column 4.(Multiple) Motor signal 5.Effectors (muscles…)

13. Reflex test Try the knee-jerk reflex yourself. –Do you have any voluntary control? Can you find any other places on your body that have a similar reflex? –What do the knee-jerk and other reflex spots have in common?