The Human Body Systems

Chapters 35 -39

Levels of Organization

• Cells – basic units of structure.

• Tissues – groups of similar cells that perform a single function.

• Organs – groups of tissues that work together to perform a complex function.

• Organ systems – groups of organs that perform related functions. (11 systems make up the human body)

4 Types of Tissues

• Epithelial – tissue covers body surfaces like internal organs.

• Connective – supports the body and connects its parts.

• Nervous – carries messages throughout the body.

• Muscle – enables the body to move.

Homeostasis

• Organ systems work together to maintain stable conditions in the body.

• Homeostasis – is the process of maintaining stable internal conditions.

• Feedback inhibition- process that enables the body to maintain a stable temperature.

• Ex. The nervous system senses when the body cools and signals the cells to produce more heat.

Skeletal System

• Supports the body.

• Protects internal organs.

• Provides attachment sites for muscles to move body parts.

• Stores mineral reserves.

• Provides a site for blood cell formation.

• There are 206 bones found in an adult human skeleton.

Skeletal System

• 2 Parts:– Axial – skull, spine, and ribs.– Appendicular – all the bones associated with the

arms & legs, including bones of the shoulders, hips, hands, & feet.

• Made up of:– Periosteum – tough connective tissue.– Compact bone – thick layer of tubes (Haversian

canals) which contain blood vessels & nerves.– Bone marrow – cavities of soft tissue.

• Red marrow produces blood cells.• Yellow marrow is fat.

Skeletal System

• Cartilage – type of connective tissue that is tough but flexible.

• The skeleton of an embryo is composed almost entirely of cartilage.

• Joint – place where one bone attaches to another bone and permits the bones to move w/o damaging each other.

Skeletal System

• 3 types of Joints:– Immovable – skull, no movement.– Slightly movable – spine, allow small/restricted

movement.– Freely movable – movement in one or more directions.

• Ball-and-socket joints – allow the widest range of movement of any joint. Ex. Shoulder.

• Hinge joint – permit only back-and-forth movement. Ex. Knee.• Pivot joint – one bone rotates around another. Ex. Elbow.• Saddle joint – one bone slides in two directions. Ex. Hand.

• Ligaments – strips of tough connective tissue that connects bone to bone.

Skeletal System

• Arthritis – disorder that involves inflammation of the joints.

• Osteoporosis – condition in which bones weaken and could fracture or break.

Muscular System

• Muscle tissue is over 40% of the mass of the human body.

• 3 Types:– Skeletal – usually attached to bones; appear striped

(striated); responsible for voluntary movement. Ex. Dancing, running.

– Smooth – line blood vessels & the digestive tract; not striated and not under conscious control. Ex. move food through the digestive tract & control the flow of blood through the circulatory system.

– Cardiac – found only in the heart; not under conscious control.

Muscular System

• Fibers – Skeletal muscle cells.

• Myofibrils – smaller structures of fibers.

• Filaments – even smaller structure of myofibrils which can be thick or thin.

• A muscle contracts when the thin filaments in the muscle fiber slide over the thick filaments.

Muscular System

• Impulses from motor neurons in the nervous system control the contraction of skeletal muscles.

• The more muscle cells that are stimulated to contract, the stronger the contraction.

• Tendons – tough connective tissues that connect skeletal muscles to bones.

• Regular exercise helps maintain strength & flexibility of muscles, strengthens bones, & prevents injury.

Integumentary System

• The skin is the single largest organ of the body.

• Serves as a barrier against infection and injury.

• Helps regulate body temperature.• Removes waste products from the

body.• Provides protection against ultraviolet

radiation from the sun.

Integumentary System

• 2 Layers:– Epidermis – outer layer which is made of flat, dead

cells.• Produces keratin which is a tough, fibrous protein that helps

keep the epidermis flexible & waterproof. • Contains melanocytes which produce melanin ( a dark brown

pigment that helps protect the skin from ultraviolet rays).– Dermis – inner layer.

• Contains nerves, blood vessels, glands, & other structures not found in the epidermis.

• Works with other organs to maintain homeostasis.• Regulates body temperature.

– Sweat glands produce sweat when the body gets too hot. Sweat evaporates from the skin & cools the body.

Integumentary System

• Too much sunlight can produce skin cancer.

• Protect yourself by wearing hats, sunglasses, protective clothing, and sunscreen with a sun protection factor (SPF) of at least 15.

Integumentary System

• Other parts of this system:– Hair

• Composed of keratin.• On the head – protects scalp from sunlight and cold.• In the nostrils & around eyes – prevents dirt from entering the

body.• Produced by hair follicles in the dermis.

– Nails• Composed of keratin.• Grow from an area called the nail root.• Protect tips of fingers & toes.

Nervous System

• Controls and coordinates functions throughout the body.• Responds to internal and external stimuli.• Impulses – electrical signals that carry messages.• Neurons – smallest structural & functional unit that

transmit impulses.• Dendrites – short branches that carry impulses toward the

cell body.• Axon – long fiber that carries impulses away from the cell

body.• Synapse – at the end of an axon and is where a neuron

can transfer an impulse to another cell.• Neurotransmitters – transmit impulses across the

synapse.

Nervous System

• 2 Major Divisions:– Central Nervous System

• control center of the body.• Relays messages.• Processes information.• Analyzes information.

– Peripheral Nervous System• carries messages back & forth b/w the

environment & the central nervous system.

Nervous System

• Central Nervous System – Brain – divided into several regions:

• Cerebrum – controls voluntary (conscious) actions.• Cerebellum – controls actions of the muscles.• Brain stem – controls basic body functions.• Thalamus – receives impulses from the senses & sends

them to the cerebrum.• Hypothalamus – connects the nervous & endocrine systems.

– Spinal cord – connects the brain & the rest of the body.

• Processes certain kinds of information, reflexes.• Reflex – a quick, automatic response to a stimulus.• Ex. – sneezing.

Nervous System

• Peripheral Nervous System– Sensory division – transmits impulses from

sensory neurons to the central nervous system.

– Motor division – transmits impulses from the central nervous system to the muscles & glands.

• Somatic – voluntary actions.• Autonomic - involuntary

Nervous System

• Sense Organs– Sensory receptors are neurons that react to

stimuli in the environment & send impulses to the central nervous system.

– 5 Types• Pain receptors – respond to pain.• Thermoreceptors – respond to temperature.• Mechanoreceptors – respond to pressure.• Chemoreceptors – respond to chemicals.• Photoreceptors – respond to light.

Nervous System

• Vision– Pupil – light enters through this opening in

the front of the eye.

– Lens – light passes through.

– Retina – focuses the light.• Photoreceptors are on the retina

– Rods are sensitive to dim light.– Cones are sensitive to colors.

Nervous System

• Hearing– Sound enters the ear– Cochlea – fluid filled structure where the

vibrations create pressure waves.• Sensory receptors are in the cochlea.

– Send impulses to the brain.

– Semicircular canals – 3 tiny canals that help the central nervous system maintain balance.

Nervous System

• Taste– Taste buds - Sense organs that detect taste.

• Touch– Skin – largest sense organ.

• Contains sensory receptors that respond to:– Temperature– Touch– Pain

Nervous System• Drugs – any substance, other than food, that changes the

structure or function of the body.– Stimulants – speeds up actions controlled by the

nervous system. Ex. Heart rate.– Depressants – slows down actions that are controlled

by the brain. • Cocaine causes the sudden release of a substance in the

brain called dopamine.– Opiates – act like natural brain chemicals called

endorphins (normally help overcome pain).• Marijuana can cause memory and concentration problems.

– Alcohol – is a depressant that slows down the central nervous system.

• During pregnancy it may cause fetal alcohol syndrome & babies could have a birth defect.

Circulatory System

• Consists of the heart, blood vessels, & blood.

• The human body contains 4 – 6 liters of blood.

• With the respiratory system, it supplies the body’s cells with nutrients & oxygen and removes carbon dioxide & other wastes form the body.

Circulatory System

• Heart– Composed almost entirely of muscle.– Myocardium – thick layer of muscle that forms the

walls of the heart; contracts and pumps blood.– 4 chambers – 2 atria (top) & 2 ventricles (bottom).– 2 halves

• Pulmonary circulation – Right; pumps blood from heart to lungs.

• Systemic circulation - Left; pumps blood to the rest of the body.

– Valves – prevent blood from flowing backward in the heart.

Circulatory System

• Aorta – large blood vessel that leaves the heart• 3 types of vessels:

– Arteries – large thick vessels that carry blood away from the heart to capillaries.

– Capillaries - smallest vessels that bring nutrients & oxygen to the cells & absorb carbon dioxide & other wastes.

– Veins – blood from the capillaries enters these large, thin vessels which return blood to the heart.

Circulatory System

Blood Pressure – The force of the blood in the arteries caused by the heart pumping.

• It keeps the blood flowing through the body.

• Controlled by the autonomic nervous system and Kidneys.

Diseases of theCirculatory System

• Cardiovascular Disease are the leading causes of death.– high blood pressure – Atherosclerosis – fatty deposits build up in

the arteries.– Lead to heart attack and stroke.– Easier to prevent if you exercise

regularly, eat a low-fat diet, control weight, & don’t smoke.

Blood & the Lymphatic System

• Plasma – fluid portion of the blood; 90% water; helps clot blood & fight infections.

• Red blood cells – transport oxygen.• Hemoglobin – found in red blood cells; binds

to oxygen & carries it throughout the body.• White blood cells – guard against infection, fight

parasites, & attack bacteria.• Lymphocytes – produce antibodies.• Platelets – help blood clot.

Blood & the Lymphatic System

• As blood circulates, some fluid leaks from the blood into surrounding tissues. This fluid is called lymph.

• Lymphatic System consists of:– Network of vessels – Lymph nodes– Organs (ex. spleen)

• The system collects lymph & returns it to the circulatory system

• It also helps absorb nutrients & fight infections.