Nervous System

• Divided into two parts based on organs1. CNS (Central Nervous System) composed of the

brain and spinal cord.2. PNS (Peripheral Nervous System) composed of the

nerves to connect CNS to rest of body.• Functions:1. Sensory—sensory neurons gather information by

detecting changes in the environment. Stimulus can be light, sound, temperature, etc. Info is passed to the CNS.

Functions

2. Interneurons interpret impulses and sends them to the brain. (Stored as memory, thought, decision, etc.)

3. Motor neurons carry impulses from CNS to muscles or glands to cause a reaction.

• Reflex Arc—impulse moves from (1) sensory neuron to (2) interneuron and back to (3) motor neuron without going to the brain. This is an automatic, unwilled response.

• Kinds are: 1. Knee jerk and 2. Withdrawal reflex

Neurons are Nerve Cells

•

Parts of Neuron

• Cell body - has organelles, a large nucleus with a nucleolus but does not undergo mitosis.

• Dendrites - may have many receptors. Conduct impulses to the cell body.

• Axon - only one but may be branched. Conduct impulses away from cell body. Has an end brush and a myelin sheath with nodes.

• Impulse “jumps” from node to node.

Conducting Across the Synapse

• Synapse - place where nerve impulses are transmitted from one neuron to another.

• Made of:

1. Synaptic Knob—tiny end of the axon

2. Synaptic Cleft—space between knob and dendrite of next neuron

3. Membrane of the next dendrite.

Synapse

• Neurotransmitters are released

from the knob into the space.

• Neurotransmitters cross the

space and bind to the dendrite’s

membrane making openings.

• This sets up the stimulus on the new neuron.

Transmitters

• Neurotransmitters

1. Acetylcholine

2. Monoamines (nor-epinephrine)

• Excitatory transmitters—increase ability to pass impulse.

• Inhibitory transmitters—raise threshold so passing impulse is not likely.

Types of Sensory Receptors

1. Pain - all parts of body except brain.

2. Thermoreceptors - detect heat and cold

3. Mechanoreceptors - detect touch, pressure, stretch and motion

4. Chemoreceptors - nose and taste buds

5. Photoreceptors - found in eyes and result in vision

Vision

Hearing and Balance

Smell and Taste

• Basic tastes are: sweet, sour, salty, and bitter

Drugs• How drugs affect:

1. Increase the rate that a neuron releases neurotransmitters.

2. Slow the rate that neurotransmitters are removed from the synaptic cleft.

3. Bind to receptor sites causing abnormal patterns of action potentials.

4. Drugs always affect the receptor sites of the neuron.

Definitions

• Tolerance—more and more of the drug is needed to produce the same effect.

• Addiction—uncontrolled dependence on a drug.

• Withdrawal—physical and psychological symptoms like shaking, nausea, increased heart rate, hallucinations and depression.

Stimulants

• Ex: Caffeine, nicotine, cocaine, and methamphetamine

• Increase heart rate and blood pressure

1. Cocaine blocks the removal of pleasure-inducing neurotransmitters giving a temporary high going to depression. Causes permanent damage to the brain.

2. Methamphetamine (crank, ice, speed) increases activity, decreases appetite and well being. Can cause violent behavior, confusion, sleeplessness, and permanent damage to nervous system.

Depressants

• Slows CNS activity

1. Alcohol—coordination, judgment slowed. Severe liver and brain damage, cardiovascular disease and some cancers. Can cause death.

2. Also includes tranquilizers and barbituates

Marijuana (Hemp)

• Contains more than 400 different chemicals

• THC is main one.

• Brain changes—loss of memory and learning, loss of coordination and high anxiety

Narcotics• Ex: morphine, codeine, heroin (opiates)

• Bind to receptors causing euphoria.

• Slows functioning of the brain stem and blocks pain.

• All but heroin are used medically to reduce pain.

• Addiction is quick—withdrawal is painful

Hallucinogens

• Ex: Mushrooms, peyote, LSD

• Cause confusion and panic

• See, hear and perceive things not present.

Ecstasy

• Increase energy and cause hallucinations

• Give blurred vision and memory loss.

• Cause paranoia.

Inhalants

• Vapors—solvents, aerosols, some gases, nitrates.

• Mind altering effects

• Cause increased heart rate, clumsy, slurred speech, damage to lungs and liver.

• Can cause death.