Biology: Human Body Systems | High School Study Notes
Human Body Systems
High School Biology | Complete Study Notes
Covers: All major body systems | Organs | Functions | Key Terms
The human body is made up of 11 major organ systems that work together to maintain life. Each
system has specific organs and functions that help keep the body in balance (homeostasis).
Overview of Body Systems
System Main Organs Primary Function
Skeletal Bones, cartilage, ligaments Support, protection, movement
Muscular Skeletal, smooth & cardiac Movement and posture
muscles
Nervous Brain, spinal cord, nerves Control and coordination
Circulatory Heart, blood vessels, blood Transport nutrients and oxygen
Respiratory Lungs, trachea, diaphragm Gas exchange (O2 / CO2)
Digestive Stomach, intestines, liver Break down and absorb food
Excretory Kidneys, skin, lungs Remove waste from the body
Endocrine Glands (pituitary, thyroid, etc.) Hormone regulation
Immune White blood cells, lymph nodes Fight infection and disease
Reproductive Ovaries / testes Produce offspring
Integumentary Skin, hair, nails Protection and temperature
control
1. The Skeletal System
The skeletal system is the framework of the body, made up of 206 bones in adults.
Key Functions
• Provides structure and shape to the body
• Protects vital organs (e.g., skull protects the brain)
• Works with muscles to allow movement
• Produces blood cells in the bone marrow
• Stores minerals like calcium and phosphorus
Key Terms
Page 1
, Biology: Human Body Systems | High School Study Notes
• Hard tissue that forms the skeletonBone:
• Flexible connective tissue at jointsCartilage:
• Connects bone to boneLigament:
• Connects muscle to boneTendon:
• Where two or more bones meet (e.g., knee, elbow)Joint:
2. The Muscular System
The body has over 600 muscles that work in pairs to produce movement.
Three Types of Muscle
Type Location Control
Skeletal (striated) Attached to bones Voluntary (you control it)
Smooth Walls of organs (stomach, Involuntary (automatic)
intestines)
Cardiac Heart only Involuntary
How Muscles Work
• Muscles can only pull, never push — they work in antagonistic pairs
• Example: Bicep contracts (shortens) to lift arm; tricep contracts to lower it
3. The Nervous System
The nervous system controls and coordinates all body activities by sending electrical signals (nerve
impulses).
Two Main Divisions
• Brain and spinal cord — the control centreCentral Nervous System (CNS):
• All other nerves connecting the CNS to the bodyPeripheral Nervous System (PNS):
Parts of the Brain
• Thinking, memory, language, voluntary movementCerebrum:
• Balance and coordinationCerebellum:
• Controls automatic functions (breathing, heartbeat)Brain stem:
The Neuron (Nerve Cell)
• Dendrites receive signals
• Cell body processes the signal
• Axon sends the signal to the next neuron
• Synapse: the gap between neurons where signals are passed by chemicals called
neurotransmitters
Page 2
Human Body Systems
High School Biology | Complete Study Notes
Covers: All major body systems | Organs | Functions | Key Terms
The human body is made up of 11 major organ systems that work together to maintain life. Each
system has specific organs and functions that help keep the body in balance (homeostasis).
Overview of Body Systems
System Main Organs Primary Function
Skeletal Bones, cartilage, ligaments Support, protection, movement
Muscular Skeletal, smooth & cardiac Movement and posture
muscles
Nervous Brain, spinal cord, nerves Control and coordination
Circulatory Heart, blood vessels, blood Transport nutrients and oxygen
Respiratory Lungs, trachea, diaphragm Gas exchange (O2 / CO2)
Digestive Stomach, intestines, liver Break down and absorb food
Excretory Kidneys, skin, lungs Remove waste from the body
Endocrine Glands (pituitary, thyroid, etc.) Hormone regulation
Immune White blood cells, lymph nodes Fight infection and disease
Reproductive Ovaries / testes Produce offspring
Integumentary Skin, hair, nails Protection and temperature
control
1. The Skeletal System
The skeletal system is the framework of the body, made up of 206 bones in adults.
Key Functions
• Provides structure and shape to the body
• Protects vital organs (e.g., skull protects the brain)
• Works with muscles to allow movement
• Produces blood cells in the bone marrow
• Stores minerals like calcium and phosphorus
Key Terms
Page 1
, Biology: Human Body Systems | High School Study Notes
• Hard tissue that forms the skeletonBone:
• Flexible connective tissue at jointsCartilage:
• Connects bone to boneLigament:
• Connects muscle to boneTendon:
• Where two or more bones meet (e.g., knee, elbow)Joint:
2. The Muscular System
The body has over 600 muscles that work in pairs to produce movement.
Three Types of Muscle
Type Location Control
Skeletal (striated) Attached to bones Voluntary (you control it)
Smooth Walls of organs (stomach, Involuntary (automatic)
intestines)
Cardiac Heart only Involuntary
How Muscles Work
• Muscles can only pull, never push — they work in antagonistic pairs
• Example: Bicep contracts (shortens) to lift arm; tricep contracts to lower it
3. The Nervous System
The nervous system controls and coordinates all body activities by sending electrical signals (nerve
impulses).
Two Main Divisions
• Brain and spinal cord — the control centreCentral Nervous System (CNS):
• All other nerves connecting the CNS to the bodyPeripheral Nervous System (PNS):
Parts of the Brain
• Thinking, memory, language, voluntary movementCerebrum:
• Balance and coordinationCerebellum:
• Controls automatic functions (breathing, heartbeat)Brain stem:
The Neuron (Nerve Cell)
• Dendrites receive signals
• Cell body processes the signal
• Axon sends the signal to the next neuron
• Synapse: the gap between neurons where signals are passed by chemicals called
neurotransmitters
Page 2
