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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 the Circulatory 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.