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

• 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)

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

Action Potential – Resting II

• Concentration Gradient• 3 Na+ (sodium) vs. 2

K+ (potassium)• Active transport-does it

use energy?

Action Potential III

• How does the myelin sheath improve conductance speed?

• impulse jumps! between Nodes of Ranvier

All or none!

• Threshold Stimulus

• Subthreshold – those stimuli that are weaker than threshold (No AP)

Synaptic Gap

• Spaces between neurons

• Synaptic vesicles at bulb (end of axon) contain neurotransmitters

• Show video clip

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

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…)

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?