Topic 9: Human Body Systems Science 8

Nervous System

Regulates and controls all other systems in the body; receives and interprets signals (stimuli).

Stimulus

A signal received by the body that causes a response.

Neuron

A nerve cell that picks up and transmits impulses.

Impulse

A message carried by neurons to the brain.

Response

The reaction of the body to a stimulus.

Brain

The organ where impulses are interpreted and responses are coordinated.

Cerebrum

Part of the brain controls voluntary activities, intelligence, memory, language, and senses.

Cerebellum

Part of the brain responsible for coordination and balance.

Medulla

Part of the brain controls involuntary activities like breathing and heart rate.

Spinal Cord

A bundle of nerves running from the brain down the back, protected by vertebrae.

Peripheral Nervous System

Nerves outside the brain and spinal cord; transmits impulses to/from the CNS.

Central Nervous System (CNS)

Consists of the brain and spinal cord; processes and interprets impulses.

Cancer (nervous system)

Uncontrolled growth and division of nerve cells.

Receptor

A structure that detects stimuli.

Neurotransmitter

Chemical messenger transmitting signals between neurons.

Stimulant

Drug that increases neurotransmitter activity (e.g., caffeine, nicotine).

Depressant

Drug that lowers brain and nerve activity (e.g., alcohol, benzodiazepines).

Respiratory System

System responsible for gas exchange (oxygen in, carbon dioxide out).

Lungs

Organs where gas exchange occurs.

Mouth

Entry point for air into the respiratory system.

Trachea

Windpipe; connects mouth to bronchi.

Bronchi

Two main branches from the trachea into the lungs.

Bronchioles

Smaller branches of the bronchi in the lungs.

Alveoli/Alveolus

Tiny air sacs in the lungs where gas exchange occurs.

Diaphragm

Muscle that helps move air in and out of the lungs.

Capillaries

Small blood vessels where gas exchange occurs with alveoli.

Medulla (respiratory)

Brain region controlling breathing rate.

Circulatory System

Transports nutrients, wastes, water, and gases throughout the body.

Red Blood Cells

Cells that transport oxygen.

White Blood Cells

Cells that protect the body from invaders.

Platelets

Cell fragments that help blood clot.

Antigen

Foreign substance that stimulates an immune response.

Antibody

Protein produced by white blood cells to destroy antigens.

Artery

Blood vessel carrying blood away from the heart.

Vein

Blood vessel carrying blood toward the heart.

Atrium (Atria)

Upper chambers of the heart.

Ventricle

Lower chambers of the heart.

Aorta

Major artery carrying oxygenated blood from the heart to the body.

Pulse

Surge of blood through arteries with each heartbeat.

Feedback Mechanism

Process where the body maintains homeostasis (e.g., brain controlling heart rate).

Digestive System

System that breaks down food for nutrient absorption.

Mechanical Digestion

Physical breakdown of food (chewing, stomach churning).

Chemical Digestion

Breakdown of food molecules by enzymes.

Enzyme

Protein that speeds up chemical reactions in digestion.

Salivary Glands

Secrete saliva with amylase to break down starches.

Esophagus

Muscular tube connecting mouth to stomach; moves food by peristalsis.

Stomach

Muscular organ where food is digested mechanically and chemically.

Small Intestine

Organ where most digestion and nutrient absorption occur; contains villi.

Villi

Small projections in the small intestine that absorb nutrients.

Amino Acids

Building blocks of proteins.

Glucose

Simple sugar from carbohydrate digestion.

Fatty Acids

Building blocks of lipids.

Pancreas

Gland that secretes insulin and digestive enzymes.

Liver

Organ producing bile and involved in digestion and excretion.

Gallbladder

Stores and releases bile into the small intestine.

Large Intestine

Absorbs water and forms feces.

Anus

End of digestive tract; expels waste.

Ulcer

Sore from excess stomach acid damaging digestive lining.

Excretory System

Removes waste products from the body.

Kidney

Organ that filters blood to produce urine.