The Nervous & Immune System

Bio and the Body 2014Ms. Boehm

What is the Nervous System?

A network of nerve cells and fibers that transmit signals between parts of the body, and the brain- the control center.

Functions of the Nervous System1) Control of all of the body’s activities

-the brain being the control center

2) Responds & adapts to changes that occur both inside & outside the body (helps maintain homeostasis)

- pain, temperature, fear, etc.

2 Main Parts:

2 Main Parts:1) Central Nervous System (CNS)

a. The body’s main processing center, includes the brain and spinal cord.

b. Plans the body’s response to a stimulus (an environmental change)

c. Orders a response to the stimulus

Ex. You put your hand on a very

hot stove top (stimulus= heat)

and you move your hand away

quickly.

Anatomy of the CNSBrain = Control center of entire body

Brain Stem = Connects brain to spinal cordControls breathing, heart rate, digestion, etc.

Spinal Cord = Column of nerves from brain to tailboneProtected by vertebrae of spineSends impulses from brain to rest of body, and relays

messages from the body to the brain

2 Main Parts:2) Peripheral Nervous System(PNS)a. Receives information from a

stimulus.b. Delivers information to the CNS.

Anatomy of the PNSNerves –bundles of neurons that

extend from spinal chord to the rest of the body

The Nervous SystemThe nervous system sends messages throughout

entire body (to & from brain)

• Neurons = Specialized nerve cells that make up the brain, spinal cord, & nerves• Send impulses (messages) throughout body

Anatomy of Neuron

Anatomy of NeuronEach Neuron has:

Cell Body = holds the nucleus

Dendrites = fibers that receive signals from other neurons

Axon = conducts electrical impulses along neuronMyelin Sheath = insulates axon to increase speed of signalSchwann Cells = help to make myelin sheathNode of Ranvier = gaps along axon that are not insulated.

This is where electrical activity is generated.

Axon Terminal = transmit electrical signal across synapse & onto another neuron

Communication within a NeuronA signal is received at the dendrites.

An electrical signal is sent down the axon to the axon terminalsThis is done by ion exchange (Na+ and K+ ions)Na+ and K+ pumps, a form of active transport,

help make a neuronhave a negative charge.

The myelin sheath’sjob is to insulatethe electrical signal-just like rubber on the outside of a cord.

Communication between NeuronsNeurons do not touch – there is a gap between them called a

synapse An electrical signal can not cross a gap

Messages are sent across synapses through special chemicals called neurotransmitters, a chemical signal Neurotransmitters leave the axon terminal by the process of

exocytosis, a form of active transport.

Summary of Neuron Function

Types of NeurotransmittersSome neurotransmitters excite receiving

neurons, causing an electrical signal (Excitatory)

Others prevent, or block, the electrical signal from forming in receiving neurons (Inhibitory)

Examples:

1. Acetylcholine- causes muscle cells to contract (Botox fun fact)

2. Dopamine- reward motivated behavior, a feel good chemical(low levels related to depression)

Effect of Drugs on the Nervous System

Drugs can affect the nervous system in different waysDrugs can:

Increase the release of neurotransmittersDecrease the release of neurotransmittersMimic a neurotransmitter

Drug AddictionAbuse of drugs can cause a tolerance of the

drugMeaning that more and more of the drug is needed

to produce the same effects.

Addiction is an uncontrollable dependence on a drug.

Withdrawal is experienced when the drug is not takenSymptoms are physical and psychological Examples are shaking, sweating, nausea,

depression

Types of DrugsStimulants

Increase the activity of the CNS, highly addictive Typically increase heart rate, blood pressure, and

decrease appetite. Examples: caffeine, nicotine, cocaine,

methamphetamines

Depressants Slow the activity of the CNS, overdoses prevent the CNS

from functioning leading to death Cause drowsiness, poor judgment, lack of coordination Examples: alcohol, sedatives, sleeping pills

Marijuana Acts as both a stimulant and a depressant Side effects include problems with memory and learning,

distorted perception, loss of coordination and anxiety.

Types of Drugs, cont.Narcotics

Mimic natural chemicals in the CNS and bind to receptors, HIGHLY addictive, and withdrawal is extremely painful.

Opiates are narcotics derived from the opium poppy, a plant.

Side effects include feelings of euphoria, block pain signals

Examples: morphine, codeine, heroin

Inhalants Vapors from certain substances can cause mind altering

effects. Causes slurred speech, clumsiness, increased heart rate,

damage to major organs First time users can die suddenly from heart failure or

suffocation. Examples: volatile solvents, aerosols, certain gases