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Nervous System

Nervous System. Divisions. Central Nervous System Brain & Spinal Chord Peripheral Nervous System Autonomic- involuntary Somatic- voluntary. Neurons I. Nerve=bundle of neurons Neurons draw and label) have: 1. Cell Body Nucleus and organelles 2. Dendrites Receive impulses. Neurons II.

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Nervous System

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  1. Nervous System

  2. Divisions • Central Nervous System • Brain & Spinal Chord • Peripheral Nervous System • Autonomic-involuntary • Somatic-voluntary

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

  4. 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)

  5. 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

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

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

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

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

  10. 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

  11. Spinal Reflexes • Does not reach higher brain levels! • No thought involved • Receptor Stimulated • Sensory • Association neurons in spinal column • (Multiple) Motor signal • Effectors (muscles…)

  12. 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?

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