NERVOUS SYSTEM LECTURE OUTLINE
I. Function of the Nervous System:
II. Divisions of the Nervous System
Anatomical (structural) divisions of the Nervous System:
Functional divisions of the Nervous System
Sensory and Motor Subdivisions:
1. ANS (automatic ) glands, smooth muscle, heart
ANS divided into SYMPATHETIC and PARASYMPATHETIC
2. SNA (somatic) skeletal
III. Nervous system structures
IV. Cells and Tissues
1: Extreme longevity
3: High Metabolic Rate
Structure of Neuron
Two types of cells:
3 categories based on the number of processes or poles
4 types of cutaneous sensory receptors: Majority are pain receptors (bare endings) WARNING MECHANISM
Pain : naked
Meissners corpuscle : touch
Pacinian corpuscle: deep pressure
Ruffini corpuscle: heat
Krause end bulb: touch/pressure
2: Structural and Functional classification of supporting cells: GLIAL
d) ependymal cells
V. Neuron Physiology HOW THEY MAKE ELECTRICITY !
1. Beginning in Brain /or beginning at a sensory neuron receptor, a thought or stimulus is applied. *stimulus can be either: chemical, electrical, tactile…..
2. Na+ rushes into receptor=depolarization (there must be ENOUGH Na+ to cause this to happen and that is determined by THE STRENGTH OF THE STIMULUS or THE NUMBER OF RECEPTORS STIMULATED SIMULTANEOUSLY). This is called ACTION POTENTIAL WHEN THE ELECTRICITY IS CREATED.
3. The electricity at that point causes the NEXT section at the node of Ranvier Na+ gate to open and more Na+ rushes into the next section and this causes the electricity to jump to the next section AND SO ON AND SO ON …..= PROPAGATION OF NERVE IMPULSE. *NOTE…while the electricity moves onward, the section of neuron behind it gets REPOLARIZED and ready for it to happen again…see #8 below.
4. At the end of the axon…is the SYNAPTIC KNOB. The electricity causes the Ca+ gates to open, (and you SHOULD know what happens next)…just in case you don’t though….
5. Ca+ enters, causing the Vacuoles containing neurotransmitter to fuse the end of the synaptic knob and open.
6. The neurotransmitter enters the synapse (gap between a neuron and another neuron or an effector)
7. The neurotransmitter opens the Na+ gates of the next neuron or effector and the electricity enters.
8. REPOLARIZATION. ATP is used to power an ion pump = Na+K+ pump. This will pump Na+ out of the neuron and K+ back in to re-establish the RESTING POTENTIAL of the neuron so it can be stimulated again…
9. During the repolarization period, the neuron is in an ABSOLUTE REFRACTORY PERIOD, when it cannot be restimulated….UNLESS a huge stimulus comes along…like your wet finger gets stuck into an electrical outlet…or lightening strikes you…
10. A neuron is basically ready to FIRE again within .001 sec on the average.
- Presynaptic neuron
- Postsynaptic neuron
Disorders and such