Human Body Systems

Organization of the Human Body

• The human body is organized into cells, tissues, organs, and organ systems
• Homeostasis is defined as a controlled, stable internal environment, despite changes in internal and external environment

Digestive System

• Breaks down food molecules
• Converts energy from food into ATP, which cells use to power processes
• Supplies raw materials like water, carbohydrates, fats, proteins, vitamins, and minerals

Nutrients

• Water is the most important nutrient for chemical reactions, blood, and bodily fluids
• Humans need to consume at least 1 liter of fluid each day to replace fluids lost from sweat, urine, and exhaling

Carbohydrates

• Major source of energy

Fats

• Help the body absorb fat-soluble vitamins
• Part of cell membranes, nerve cells, and certain hormones
• Protect body organs and insulate the body

Proteins

• Supply amino acids for growth and repair of structures such as skin and muscle
• Regulate chemical reactions as enzymes
• Transport materials across cell membranes

Vitamins

• Organic molecules that the body needs in small amounts
• Help perform important chemical reactions
• Examples include: A, B's, C, D, E, and K

Minerals

• Inorganic nutrients that the body needs in small amounts
• Examples include: calcium, iron, sodium, and zinc

Balanced Diet and Weight

• A balanced diet provides adequate nutrients and energy to maintain a healthful weight
• Regular physical activity helps to maintain a healthful weight
• Physical activity burns excess calories, strengthens the heart, bones, and muscles

Alimentary Canal

• The digestive system is built around this
• It is a one-way tube that passes through the body, allowing for specialization

Stages of Digestion

• Ingestion occurs in the mouth
• Physical digestion occurs in the mouth and stomach
• Chemical digestion occurs in the small intestine
• Absorption occurs in the small intestine
• Elimination occurs in the large intestine

Excretory System

• Excretion: metabolic wastes are eliminated (toxic products from cellular chemical reactions removed from the body) to maintain homeostasis
• Carbon dioxide is produced by every cell during cellular respiration and is toxic therefore must be transported to the lungs via bloodstream for removal
• Nitrogen wastes from protein breakdown are converted into urea by the liver and then delivered to the kidneys via the bloodstream for elimination
• The kidneys are responsible for producing and excreting a waste product known as urine
• Other parts of the excretory system are pathways to get urine out of the body

Circulatory System

• Transports oxygen, nutrients, and other substances throughout the body
• Removes wastes from tissues
• The heart consists almost entirely of myocardium muscle that begins contracting before birth and stops only when you die
• Powerful heart muscle contractions pump blood through the circulatory system
• An adult’s heart contracts 72 times a minute on average, pumping about 70 milliliters of blood with each contraction

Heart Structure

• Four chambers: 2 atria and 2 ventricles
• Valves prevent backflow, so blood flows in one direction

Circulation

• The right side of the heart pumps oxygen-poor blood to the lungs
• The left side of the heart pumps oxygen-rich blood to body tissues
• Blood is designed to stay inside vessels at all times as part of a closed circulatory system
• Diffusion occurs at capillaries

Respiratory System

• For most organisms, respiration is the process of gas exchange between a body and the environment
• Takes oxygen and expels carbon dioxide

Breathing

• Air moves in and out of lungs based on differences between pressure inside the lungs versus outside the body
• Inhale = contract muscles, which decreases pressure inside lungs and allows air to move in
• Exhale = relax muscles, which increases pressure inside lungs and forces air to move out

Alveoli

• Lungs contain millions of small air sacs, called alveoli, that are grouped in clusters
• A network of capillaries surrounds each alveolus
• The alveoli increase surface area for more gas exchange
• Gas exchange between air inside lungs and blood in pulmonary capillaries based on laws of diffusion

Breathing and Homeostasis

• Conscious control is possible over breathing
• Breathing is not purely voluntary
• The nervous system has final control of breathing muscles consciously or not

Smoking Effects

• Three dangerous substances in tobacco smoke are nicotine, carbon monoxide, and tar
• Nicotine is an addictive stimulant that increases heart rate and blood pressure, so then the heart has to work harder
• Carbon monoxide is a poisonous gas that blocks hemoglobin from binding with oxygen
• Tar contains at least 60 compounds known to cause cancer
• Smoking can cause permanent damage to the respiratory system
• Smoking can lead to diseases such as chronic bronchitis, emphysema, and lung cancer
• Secondhand smoke exposure increases the risk for respiratory and circulatory system disease

Nervous System

• Collects information about the body’s internal and external environment
• Processes that information and responds to it
• Neurons are specialized cells that can transmit and conduct nerve impulses

Nerve Impulse

• Electrochemical process based on opening protein channels and using protein pumps to move ions into/out of a nerve cell

Divisions of the Nervous System

• The Central Nervous System (CNS) includes the brain and spinal cord
• The Peripheral Nervous System (PNS) includes cranial and spinal nerves
• Those nerves aka branch off the spinal cord

Spinal Cord

• Main communication link between brain and rest of body
• Housed in the spinal cavity within the vertebral column (backbone)
• Spinal nerves branch off and spread out into parts of the body

Meninges

• Protective membranes (3 layers) that surround the brain and spinal cord

Addiction and the Brain

• When we engage in an activity that brings us pleasure, neurons in the hypothalamus and the limbic system release dopamine
• Dopamine molecules stimulate other neurons across synapses, producing the sensation of pleasure

Addiction

• Methamphetamine releases a flood of dopamine, producing an instant “high”
• Cocaine keeps dopamine in the synaptic region longer, intensifying pleasure and suppressing pain
• Opiates stimulate receptors elsewhere in the brain that lead to dopamine release
• Nicotine and alcohol also cause increased release of dopamine

Dopamine Levels

• Excessive dopamine from drugs, causes the brain to reduce receptors
• As a result, normal activities are not pleasurable
• Addicts feel depressed and sick without the drugs
• Because there are fewer receptors, larger amounts of drugs are needed
• This results in a deeper spiral of addiction that is difficult to break

Developing Brain

• Introducing substance to alter a developing brain (before about 25 years old) significantly increases the chance of developing an addiction later in life

Endocrine System

• Acts as the 2nd controlling system
• Includes glands that produce and release hormones
• Hormones travel through the blood and control the actions of cells, tissues, and organs

Endocrine Control

• Food intake increases blood glucose
• Pancreas releases insulin or glucagon in response to blood glucose levels
• Between meals, blood glucose level drops

Skeletal System

• Supports the body
• Protects internal organs
• Assists movement
• Stores minerals and is a site of blood cell formation

Joints

• Places where two or more bones meet and connect

Muscular System

• Muscles generate the force and produce movement
• The body has 3 types of muscle tissue: smooth, skeletal, and cardiac

Integumentary System

• Serves as a layer of dead cells, that is a barrier against infection and injury
• Helps regulate body temperature
• Removes wastes from the body
• Gathers information
• Produces vitamin D

Reproductive System

• Male and female reproductive system development guided by testosterone and estrogen
• Becomes fully functional (capable of producing offspring) during puberty
• Puberty begins in the brain, when the hypothalamus signals the pituitary to produce hormones that affect the reproductive organs

Fertilization

• Fertilization has to occur 1-2 days after ovulation (egg released from ovary)
• A sperm's chromosomes enter the egg cell (both cells are haploid)
• A single diploid (2N) nucleus forms within the egg cell, containing a set of chromosomes from each parent cell

Zygote

• The fertilized egg
• Shortly after fertilization, the zygote or embryo begins to undergo rapid mitosis
• Groups of cells will develop into tissues and then organs throughout embryonic development

Pregnancy

• The placenta forms around the 3rd week of development and acts as the embryo's organ of respiration, nourishment, and excretion.
• Fetal heart becomes large enough to be heard, and things like hands, feet, eyes, ears, and a nose are well developed by the 14th week.

Fetus

• The embryo is called this after 8 weeks of development
• Most of the major organs and tissues are fully formed by the end of three months, when it is about 8 centimeters long and begin to move/show signs of reflexes
• The mother begins to feel movement, and bone continues to replace cartilage to form the early skeleton

Pregnancy (7-9 months)

• The fetus doubles in mass.
• Organs undergo a series of changes that prepare them for life outside the uterus
• Central nervous system
• Lungs
• Body temperature regulation