NEURONS - MICRO LEVEL
 

THE SMALLEST FUNCTIONAL UNIT IN OUR BRAIN -

50 TO 100 BILLION WITH UP TO 80,000 CONNECTIONS


CELL BODY- houses metabolic functions of that neuron - to keep it alive and
                        functioning - contains the nucleus

DENDRITE-  branch-like formation that receive signals

AXON-  nerve fiber - long fiber that send signals (electrical impulses), received from the
                dendrites, relays it to terminal buttons

MYELIN SHEATH (MS)-   fatty lipid sheath surrounding axon - speed of message
                                           is controlled here - thicker MS transmits message faster -
                                                thinner MS transmits message slower

GLIAL CELLS-  supports neuron with nutrients, cleans wastes, separates neurons
                               from the MS
 
 




ELECTRICAL (ELECTRONS) ARE BEING TRANSMITTED
 
 
 

3 TYPES OF NEURONS
        1 sensory neuron - from receptor to surface in sense organ
         2 motor neuron - sends message to moving body parts
        3 interneuron  -  neurons interacting with each other


 

NEUROTRANSMITTERS ARE CHEMICALS THAT CROSS THE SYNAPTIC GAP AND EITHER
EXCITE OR INHIBIT POST-SYNAPTIC NEURONS - allows communication between neurons
They are like a lock and key - they must match up

EXAMPLES OF NEUROTRANSMITTERS

ACETYLCHOLINE - muscle activity, memory and learning - peripheral nervous system
                                      affecting the heart, stomach, liver, sweat glands, blood vessels,
                                      and others.  Alzheimer's patients have a 90% deficiency of this
                                      chemical in their brain.
CATECHOLAMINES - BIOGENIC AMINES
   - EPINEPHRINE - functions as both hormone and neurotrans - increases alertness and energy
    - NOREPINEPHRINE - aids in memory, learning, and emotion - affects mood and attention
    - DOPAMINE - deals with fine motor control (Parkinson disease sufferers have a deficit of this chemical
                          (Mohammed Ali suffers from this disease)
    - SERATONIN - linked with mood,emotions, sleep, consciousness, and digestion
GABA (GAMMA AMINO BUTYRIC ACID) - Central Nervous System (CNS) main amino acid
                                                                               inhibitory neurotransmitter - induces sleep
 
 

NEURON FIRING

ION     charged particles [sodium Na (+ outside; potassium k (+ inside) chloride Cl (-)]

RESTING POTENTIAL    equilibrium of ions at -70 millivolts (mv)

ACTION POTENTIAL is the firing of the neuron - sodium rushes in causing a change in
                                           neural polarization or charge.  The charge travels down the axon to
                                           terminal buttons, neurotransmitters are released - cross the
                                           synapse - thus stimulating other neurons

"ALL OR NOTHING FIRING"  happens when a neuron will fire only when the conditions
                                                         are right

notes by Dawn Meyer