1. Nervous System General Functions
Recognizes and coordinates the body’s response to changes in its internal and external environments.
Sensory input – vision, hearing, balance, smell, taste, and touch
Motor output – muscle contraction and movement
Memory and integration of information

2. Neurons (Nerve Cells)
A. Neurons are specialized cells that carry electrical signals called impulses
1. 3 Types of Neurons:
a. Sensory – carry impulses from the sense organs to the spinal cord and brain
b. Motor – carry impulses from brain and spinal cord to muscles and glands
c. Interneurons – Connect sensory and motor neurons and carry impulses between them
Neurons can protect themselves against infection with HIV, new research has demonstrated. They owe their hardiness to a protein called FEZ-1, made uniquely by neurons, and which appears to lock out the virus

3. Anatomy of a Neuron Draw Fig. 35-5; pg. 897
1. Cell Body
a. Largest part of the neuron
b. Contains the nucleus and most of the cytoplasm
c. Metabolic activity takes place in the cell body
Cell Body

4. Dendrites
Carry impulses from the environment or from other neurons to the cell body
Dendrites
“Dendron” is Greek for tree

5. Axon Long fiber that carries impulses away from the cell body
Ends in small swellings called axon terminals
Sciatic nerve axon is ~ 1 meter long
Axon

6. Insulates the axon; leaves small gaps where the axon is exposed
Myelin Sheath
Insulates the axon; leaves small gaps where the axon is exposed
Allows impulse to jump from gap to gap, thus increasing its speed
Produced by supporting cells called Schwann cells. Made mostly of lipids, which is why they are poor conductors

7. Nervous Tissue (Neurons)
Which part of the neuron is yellow?
Which parts are blue?

8. The Nerve Impulse A. The resting neuron
1. At rest, the outside of the cell has a net positive charge, and the inside has a net negative charge. This charge difference is called the resting potential (-70mVolts).
-70mV is about 5% of voltage in AA battery

9. 2. This charge difference is due to active transport by the sodium-potassium pump.
3. The sodium-potassium pump moves sodium (Na+) outside the cell, and potassium (K+) inside the cell.
DRAW FIG 35-6, pg. 898

10. B. The nerve impulse begins
An impulse begins when a neuron is stimulated by another neuron or by the environment.
Sodium pores open on the membrane and sodium ions flood into the neuron.
The internal charge goes from -70 mVolts to +30 mVolts.
This is called the action potential. _ + _ + _ + _ +

11. 6. This restores the resting potential to normal.
5. The influx of sodium stimulates the opening of potassium pores and (K+) flows out.
6. This restores the resting potential to normal. + _ _ _ _ +
Large concentration gradient for diffusion of K+ out of the cell. Membrane has high permeability to K+, so there will be a net flux off K+ out of the cell. When K+ exits the cell it transfers + charge from the inside of the cell out
7. But now all of the sodium is inside and the potassium is outside.
How does the cell go back to its original condition?
The sodium/potassium pump kicks in.

12. 8. The depolarization on one segment starts a domino
8. The depolarization on one segment starts a domino effect down the neuron. _ + _ + _ + _ + _
The larger the diameter of the axon, the faster the transmission speed. Thin axons have transmission speeds of several cm/sec, but large axons such as in squid have transmission speeds of 100m/sec + + _ + _ _ +

13. A Nerve Impulse (Action Potential)
DRAW FIG 35-7, pg. 899

14. Nerve Impulse Pathway (Action Potential)

15. Dendrite of adjacent neuron
The Synapse (Draw Fig. 35-8, pg. 900)
Def: The gap between the axon of one neuron and the dendrites or cell body of the next neuron.
When the impulse reaches the end of the axon, chemicals called neurotransmitters are released and carry the impulse to the next neuron.
Direction of Impulse
Dendrite of adjacent neuron
Axon
Receptor
Vesicle
Axon terminal
Synaptic cleft
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Neurotransmitter

16. Synaptic Transmission

17. Organization of the NS Central NS 1. Brain 2. Spinal Cord
B. Peripheral NS
1. Somatic NS
2. Autonomic NS
a. Sympathetic
b. Parasympathetic

18. The Brain (Draw Fig. 35-9,p. 901) Cerebrum
Largest region; folds and grooves increase surface area
Controls voluntary activities and all higher brain functions (intelligence, learning and judgment)
Right and left hemispheres are connected by corpus callosum
Corpus callosum
Cerebrum
Brain weighs ~3lbs. Most evolved of all organisms because of cerebrum. Outermost layer is cerebral cortex. Only 5mm thick, but occupies over 80% of total brain mass bc of folds and grooves. Porpoise’s cerebral cortex is second only to humans. Corpus callosum is how the left and right lobes communicate. Often cut to treat epilepsy. Left lobe is for right side of body and vise-versa.

19. Center for balance and coordination of voluntary muscle movements.
B. Cerebellum
Center for balance and coordination of voluntary muscle movements.
Latin for “little brain”, Hand eye coordination is here. It contains more nerve cells (neurons) than all the rest of the brain combined, it is a more rapidly acting mechanism than any other part of the brain, and therefore it can process quickly whatever information it receives from other parts of the brain. Third, it receives an enormous amount of information from the highest level of the human brain (the cerebral cortex), which is connected to the human cerebellum by approximately 40 million nerve fibers.
Cerebellum

20. Relays information between brain and spinal cord
Brain Stem
Relays information between brain and spinal cord
Comprised of the pons and medulla oblongata
Work together to control involuntary processes like breathing, heart rate, blood pressure, digestion, and swallowing
Medulla oblongata: lowest part of the brain,
Pons
Medulla oblongata

21. Thalamus Hypothalamus
Relay station for all sensory input to the cerebrum.
Hypothalamus
Homeostatic center that controls endocrine system (hormones), body temperature, thirst, hunger, fatigue, etc.
Thalamus
Thalamus is integration center. Sorts out sensory info. Hypothalamus weighs only a few grams, but is very important as link between endocrine and nervous systems.
Hypothalamus

22. Spinal cord Two main functions: Reflex center
Carries info to and from brain to body

23. Reflexes B. Controlled by 5-part reflex arc:
A. Reflexes are automatic responses to stimuli
B. Controlled by 5-part reflex arc:
1. Sensory receptor reacts to stimulus (heat on finger)
2. Impulse is carried to the spinal cord by a sensory neuron
3. In the spinal cord, the impulse is transferred to a motor neuron
4. Motor neuron conducts a nerve impulse to an effector (arm muscles)
5. Effector responds to the impulses by contracting (hand gets pulled away from the heat)

24. Peripheral Nervous System
Receives information from the environment and relays to and from CNS and sensory, motor and gland cells

25. Two divisions: Sensory and Motor Motor is divided into:
Somatic NS (voluntary) responds to external stimuli.
Regulates activities that are under conscious control (e.g. picking your nose)
Some reflex control
Autonomic (involuntary) NS respond to internal stimuli; two divisions:
Sympathetic ↑energy consumption (increase HR)
Parasympathetic ↓energy consumption (decrease HR)
Both help maintain homeostasis by having opposing effects
Parasympathetic center controls things like digestion and slowing heart to conserve energy. Sympathetic center controls accelerating HR, increasing metabolism, thus increasing energy consumption

26. Autonomic Nervous System

27. The Senses
5 General Sensory Receptors: pain, thermo-, mechano-, chemo- and photoreceptors.
Where do you think these different types of receptors are found and what is their function?
Pain – everywhere but brain
Thermo – temp; skin and hypothalamus
Mechano – pressure, motion and sound; skin, muscles, and ears
Chemo – chemicals; nose and tongue
Photo – light; eyes
pain-everywhere but brain, respond to chemicals released by damaged cells
thermo-skin, body core, hypothalamus, detect variations in temp
mechano-skin, skeletal muscles, inner ear, sensitive to pressure, touch, stretching of muslces, sound, motion
chemo-nose, taste buds,
photo-eyes

28. Nervous System Disorders
Bell’s Palsy – unexplained episode of facial weakness or paralysis
Dementia - damaged brain cells caused by injury or disease (Alzheimer’s); memory loss, confusion and personality change
Migraine Headaches – caused by a drop in serotonin levels? (triggered by stress, hormones, certain foods)
Multiple sclerosis (MS) – myelin sheaths deteriorate resulting in progressive loss of coordination
Parkinson’s – uncontrollable shaking caused by damage to dopamine transmitters; no cure
Tay-Sachs – fatal genetic lipid storage disorder where fat builds up on brain tissues and neurons during the first few months of life causing mental and physical deterioration

29. Drugs and the Nervous System
Stimulants
1. Accelerate HR, BP, and breathing rate
2. Increases the release of neurotransmitters; leads to release of energy and feeling of well-being
3. When effect wears off, brain’s supply is depleted leaving the user depressed and fatigued
a. Caffeine – prevents binding of adenosine
b. Cocaine – sudden release of dopamine
c. Methamphetamines – same effect as cocaine
Endorphins help overcome pain; Dopamine is release when a basic need (hunger/thirst) is met; serotonin gives feeling of wellbeing. Adenosine binds to receptors and makes you drowsy. Caffeine binds to adenosine receptors and blocks the drowsy feelings

30. Depressants
Slow down HR, lower BP and breathing rate, relax muscles and relieves anxiety
Alcohol – physical and mental impairment, depression, liver damage
Marijuana – more lung damage than cigarettes; memory loss, reduced levels of testosterone in males
Sleeping Pills