The Nervous & Immune System Bio and the Body 2014 Ms. 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 System  Control of all of the body’s activities -the brain being the control center  Responds & adapts to changes that occur both inside & outside the body (helps maintain homeostasis) - pain, temperature, fear, etc.

2 Main Parts:

 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 CNS Brain = Control center of entire body Brain Stem = Connects brain to spinal cord Controls breathing, heart rate, digestion, etc. Spinal Cord = Column of nerves from brain to tailbone Protected by vertebrae of spine Sends 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 PNS Nerves –bundles of neurons that extend from spinal chord to the rest of the body

The Nervous System The 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

Each Neuron has: Cell Body = holds the nucleus Dendrites = fibers that receive signals from other neurons Axon = conducts electrical impulses along neuron Myelin Sheath = insulates axon to increase speed of signal Schwann Cells = help to make myelin sheath Node 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 Neuron A signal is received at the dendrites. An electrical signal is sent down the axon to the axon terminals This is done by ion exchange (Na+ and K+ ions) Na+ and K+ pumps, a form of active transport, help make a neuron have a negative charge. The myelin sheath’s job is to insulate the electrical signal- just like rubber on the outside of a cord.

Communication between Neurons Neurons 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 Neurotransmitters Some neurotransmitters excite receiving neurons, causing an electrical signal (Excitatory) Others prevent, or block, the electrical signal from forming in receiving neurons (Inhibitory) Examples:  Acetylcholine- causes muscle cells to contract (Botox fun fact)  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 ways Drugs can: Increase the release of neurotransmitters Decrease the release of neurotransmitters Mimic a neurotransmitter

Drug Addiction Abuse of drugs can cause a tolerance of the drug Meaning 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 taken Symptoms are physical and psychological Examples are shaking, sweating, nausea, depression

Types of Drugs Stimulants 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