Nervous Systemp. 944, 950-952, 961-966

• Pre-Movie:http://kidshealth.org/kid/closet/movies/how_the_body_works_interim.html

• Major structures:– Brain– Spinal cord– Nerves– Sense organs

Nervous System Functions

• Regulates behavior• Maintains homeostasis• Regulates other organ systems• Controls sensory and motor functions

Neurons• A complex network of nerve cells which

transmit information throughout the body.• Enable movement, perception, thought,

emotion, learning, etc.

http://www.web-books.com/eLibrary/Medicine/Physiology/Nervous/neuron.jpg

Make-up of neurons• Dendrites – extend from the cell

body of the neuron and are the “antennae” of the neuron. Dendrites receive information from other cells

• Axon – a long membrane-covered extension of the cytoplasm that conducts nerve impulses (its ends are called axon terminals, which is where a neuron communicates with other cells)– Bundles of axons are called nerves

http://blog.lib.umn.edu/trite001/studyinghumananatomyandphysiology/axon.jpg

2 main divisions of the nervous system:

• Central Nervous System (CNS)– Consists of the brain and spinal cord

• Peripheral Nervous System (PNS)– Contains sensory neurons and motor

neurons• Sensory neurons send information from sense

organs, such as the skin, to the CNS• Motor neurons send commands from the CNS

to muscles and other organs

Brain and Cerebrum• Brain - the body’s main

processing center• Contains about 100 billion

neurons and weighs about 3 lbs.

• Cerebrum – largest part of the brain which has a long, deep groove down its center which divides it into right and left halves, or hemispheres

Hemispheres

Left hemisphere: receives sensation from and controls movements of the right side of the body

Right hemisphere: receives sensations from and controls movements of the left side of the body

Cerebellum and Brain Stem

• Cerebellum – regulates balance, posture, and movement

• Brain stem – at the base of the brain; is a collection of structures leading down to the spinal cord and connecting the cerebral hemispheres with the cerebellum

Parts of the Brain Stem

• Lower brain stem: midbrain, pons, medulla oblongata • Relay info throughout the CNS, play in role in homeostasis by helping regulate heart

rate, breathing rate, body temperature, and sleep

• Upper brain stem: thalamus, hypothalamus• Important relay centers that direct information to and from different parts of he brain• Thalamus: critical for sensory processing• Hypothalamus: along with the medulla oblongata helps regulate homeostatic functions

such as breathing and heart rate; lets you know when you are hungry or thirsty, etc.

Spinal cord• A dense cable of nervous tissue

that runs through the vertebral column, extending from the medulla oblongata through the vertebrae to a level just below the ribs.

• Links the brain to the PNS, receiving information that travels upwards through the spinal cord and also allows the brain to send commands to control the rest of the body

Drugs and the nervous system

• Drug – a chemical that alters body structures or biological functions

• Psychoactive drugs – drugs that alter the functioning of the CNS

• Examples: caffeine, alcohol, marijuana, cocaine

• Many psychoactive drugs produce physiological dependence and addiction; abuse of them can cause damage to the body or can even result in death

Example psychoactive drugs, their effects, and their risks

Key Terms• Addiction – a physiological response caused by the use of a

drug that alters the normal functioning of neurons and synapses. Once a neuron or synapse has been altered by a drug, it cannot function normally unless the drug is present.

• Tolerance – caused by repeated exposure to a drug, this is a characteristic of addiction in which increasing amounts of the drug are needed to achieve the desired sensation

• Withdrawal – emotional and physical symptoms caused by the removal of the drug from the body. Symptoms may include: vomiting, headache, depression, seizures. From barbituates and in severe alcohol addiction withdrawal can cause death.

• Stimulant - a drug that generally increases the activity of the CNS (Read about cocaine, pp. 962-63)

Alcohol (ethanol)

• A depressant, or a drug that generally decreases the activity of the CNS

• Reaction time decreases, coordination, judgment and speech become impaired– Produces a state of intoxication known as being

“drunk”• Drunkenness results as blood-alcohol

concentration (BAC) increases

Effects of alcohol• Alcohol affects neurons throughout the nervous system,

changing the shape of receptor proteins• Alcoholism is the most prevalent drug-abuse problem in

the USA• Many alcoholics don’t eat properly when drinking heavily,

which can lead to malnutrition, abnormalities in the circulatory system, inflammation in the lining of the stomach, etc.

• Liver will start to use alcohol as an energy source and therefore will accumulate fat deposits and potentially the fatal liver condition of cirrhosis (liver cells are replaced with scar tissue and liver functioning is impaired)

Nicotine• Smoking is linked to mouth cancer, heart disease, lung cancer

and emphysema but smokers have a hard time quitting because of their addiction to nicotine, a drug in cigarette smoke

• Nicotine – highly addictive stimulant found in the leaves of the tobacco plant

• In the brain, nicotine mimics the action of the neurotransmitter acetylcholine and it binds to brain cells at specific sites usually reserved for acetylcholine. These sites are the central controls of the brain so nicotine binding to them produces many changes which the body adjusts to and the systems return almost to normal – as long as smoking continues. Without nicotine those adjustments throw everything out of balance all at once.

Effects of Tobacco• Inhaled smoke does not just contain nicotine, it

also contains hundreds of toxic and mutagenic chemicals that pass through the mouth, air passages, and lungs (called tars)– Reason why smoking causes lung cancer

• The tars in smoke irritate mucous membranes in the mouth, nose, and throat. They accumulate in the lungs and paralyze cilia that move debris from the lungs. They blacken lung tissue and decrease breathing capacity.

Smokeless tobacco

• Causes cancers of the lips, mouth, and gums• When chewing tobacco is placed between the

cheek and gum, nicotine and other chemicals are absorbed into the bloodstream

Drugs of Abuse• Narcotics: extremely addictive

psychoactive drugs that relieve pain and induce sleep

• Some of the most potent are derived from the poppy plant. The sap that oozes from the cut seed pod forms a thick, gummy substance called opium. Opiates, drugs derived from opium, include codeine, morphine, and heroin.

Marijuana• Comes from various species of

the hemp plant.• The active ingredient in

marijuana and hashish (which also comes from the hemp plant) is commonly known as THC.

• When smoked, marijuana may cause disorientation, impaired judgment, short-term memory loss, and general loss of motivation

Practice/Enrichment Activities• http://highered.mcgraw-hill.com/sites/0072972

408/student_view0/nervous_system_labeling.html#

• http://www.purposegames.com/game/neuron-labeling-holes-ap-ch10-quiz

• http://www.purposegames.com/game/brain-labeling-nervous-system-quiz

• http://www.healthline.com/vpbody/nervous-brain

• http://faculty.washington.edu/chudler/chgames.html

• http://www.anatomyarcade.com/games/jigsaws/BrainJigsaw/BrainJigsaw.html

• http://www.purposegames.com/game/neuron-labeling-3-quiz

• http://www.indiana.edu/~anat215/virtuallab/index.html