Human Physiology

By: Susie ZhouPeriod 5

Nervous System

Circulatory System

Skeletal System

Integumentary System

Respiratory System

Excretory System

Muscular System

Endocrine System

Digestive System

Immune Response

Areas of Human Physiology

Reproductive System

Nervous SystemStructures Brain, spinal cord, peripheral nerves

Basic Function Coordinates the body’s response to changes in its internal and external environments

State Standards

● Students know how the nervous system mediates communication between different parts of the body and the body's interactions with the environment ● Students know the functions of the nervous system and the role of neurons in transmitting electrochemical impulses ● Students know the roles of sensory neurons, interneurons, and motor neurons in sensation, thought, and response.

The messages carried by the nervous system are electrical signals called impulses, which are transmitted by cells called neurons. There are three kinds. Sensory neurons carry impulses from the sense organs to the spinal cord and brain. Motor neurons carry them from the brain and spinal cord to muscles and glands. Interneurons connect sensory and motor neurons and carry impulses between them. The biggest part of an average neuron is its cell body, which has the nucleus and most of the cytoplasm. It’s where most metabolic activity of the cell takes place.

A nerve impulse beings when a neuron is stimulates by another neuron or by its environment. The minimum level of a stimulus that is required to activate a neuron is called the threshold.

The central nervous system (brain and spinal cord) relays messages, processes information, and analyzes information.

Motor Neuron

Interneuron

The brain consists of about 100 billion neurons, which are mainly interneurons. The largest part of the human brain is the cerebrum (site of learning and judgment) which controls the activities of the body. The brain stem connects the brain and spinal cord, and controls blood pressure, heart rate, breathing, and swallowing. The thalamus and hypothalamus are located between the cerebrum and the brain stem. The thalamus “receives information from the sense organs” and the hypothalamus is the “control center for analysis of hunger, thirst, fatigue, anger, and body temperature”. The spinal cord is the main communications link between the brain and the rest of the body where certain kinds of information are processed, such as reflexes (quick, automatic responses to a stimulus).

The peripheral nervous system lies outside of the central nervous system consisted of the brain and spinal cord. “The sensory division of the peripheral nervous system transmits impulses from sense organs to the central nervous system. The motor division transmits impulses from the central nervous system to the muscles of glands”. The body contains millions of sensory receptors, neurons that react to stimuli from the environment. They react to light, sound, motions, etc and there are five kinds of sensory receptors: pain receptors, thermoreceptors, mechanoreceptors, chemoreceptors, and photoreceptors.

We use eyes to sense light, which enters through the cornea. Lens focuses your eyes. Optic nerves carry impulses to the brain and the brain interprets them as images and provides information about of the outside environment. The human ear is used to hear and maintain balance in the nervous system. Sense of smell is an ability to detect chemical, as well as taste. Taste buds are the sense organs that detect taste.

Circulatory System

Structures The heart, blood vessels, blood

Function Brings oxygen, nutrients, and hormones to cells; fights infection; regulates blood temperature

The heart, located near the center of your chest, delivers oxygen and its beating produces the force to move oxygen-rich blood through the circulatory system. The septum serves as a wall between the right part of the heart and the left. It prevents oxygen-poor blood from mixing with oxygen-rich blood. The atrium is the upper chamber of the heart, and the lower chamber is the ventricle, which pumps blood out from the heart. There is a total of two atriums and two ventricles.

“The heart serves as two separate pumps”. On the right side of the heart, the pulmonary circulation pumps blood from the heart to the lungs. Carbon dioxide leaves the blood in the lungs and oxygen is absorbed. The pathway called systemic circulation is responsible for the oxygen-rich blood that flows into the left side of the heart that is then pumped to the rest of the body. “Blood that returns to the right side of the heart is oxygen-poor because cells have absorbed much of the oxygen and loaded the blood with carbon dioxide.”

Blood enters the heart through the arias and blood flows into the ventricles and out when the heart contracts. The one-way flow of the blood makes the pumping of the heart more efficient. Valves are extremely important because it keeps the blood flow flowing one way.

When blood leaves the left ventricle, it passes into the aorta, a large blood vessel. It’s the first of a series of blood vessels that carry the blood throughout the body and back to the heart. The blood moves through arteries, capillaries, and veins while traveling through the body. Arteries are the large vessels that all carry oxygen-rich blood. Capillaries are the smallest of the blood vessels. Their walls are only one cell thick and most blood cells have to pass through them in a single file. Capillaries brings nutrients and oxygen to the body’s tissues and absorbs carbon dioxide and other waste products. Veins are in charge of bring the blood make to the heart once it has passed through the capillaries. The blood flow that takes place in veins usually defies gravity.

The heart produces pressure when pumping blood, caused by the force of blood against the arteries’ walls. Blood pressure decreases when the heart relaxes, although the system still remains under pressure. Without blood pressure, blood would stop flowing throughout the body. The average blood pressure of an adult is 120/80. Whenever blood pressure is too high, neurotransmitters are released to relax the muscles around blood vessels. When blood pressure is too low, the muscles are contracted. Kidneys also help regulate blood pressure by removing more from the blood when blood pressure is too high.

Many circulatory system disorders come from atherosclerosis, in which plaque builds up on artery walls. High blood pressure may also cause medical problems. A heart attack occurs when the arteries bringing nutrients to the heart becomes blocked, causing the heart to die from lack of oxygen. Blood clots that break free and become lodged in blood vessels leading to the brain are known as a stroke. Such disorders are easily prevented with exercise, weight control, and a good healthy diet.

Skeletal SystemStructures Bones, cartilage, ligaments, tendons

Function Supports the body and protects internal organs. Allows movements and provides a site for blood cell formation.

The bones in the skeletal system supports the human body like a frame supporting a house. The skull serves as a protective shell around the brain and the ribs is a cage that protects the heart and lungs. Together with muscles, bones allow the body to move. Bones are also where blood cells form. The skeletal system is divided into two sections, the axial skeleton and the appendicular skeleton. The axial skeleton consists of the skull, vertebral column, and the rib cage. The appendicular system consists of the bones of the arms and legs, the bones of the pelvis and shoulder area.

Bones are living tissue, with a network of living cells and fibers that are surrounded with calcium salts. The bone is surrounded with the periosteum, a layer of connective tissue. Haversian canals run through compact bone that contain blood vessels and nerves. After the compact bone is the spongy bone. There are also cavities that contain soft tissues called bone marrow, which can be either yellow (fat cells) or red (blood cells).

Bones begin as cartilage, a type of connective tissue. Cartilage does not contain blood vessels like bones, so they much rely on the blood vessels in its surrounding tissues. Even though cartilage is extremely flexible, it can still support weight with its density. During ossification, bone forms and replaces cartilage. It beings seven months after birth. Long bones grow plates at either end and lengthen when cartilage grow at the plates. Eventually, that cartilage is replaced with bone tissue, which makes the bone stronger. Ossification finished around late teens or early adulthood, and bone growth stops completely. When a bone is broken, bone formation will occur also. Once bone growth stops, cartilage is only found where flexibility is needed, like the nose and ears.

Immovable joints as the name suggests are not movable. The joints are locked or fused together, like in the places where bones in the skull meet.

Some joints are slightly movable; the bones are separated from each other.

Freely movable joints (ball-and-socket, pivot, saddle) allow movement in many directions.

Bones that are movable are covered with cartilage at the end that protects the bone as it moves against other bones. Those joint capsules consists of two layers, one with strips of though tissue called ligaments. They hold the bones together and the bursa reduces the friction between the bones of a joint and even serves as a shock absorber. When a tissue is damaged, symptoms such as swelling and redness will occur.

Muscular System

Structures skeletal muscle, smooth muscle, cardiac muscle

Function Helps produce movement and circulate blood while moving food around the digestive system

State Standards

● Students know the cellular and molecular basis of muscle contraction, including the roles of actin, myosin, Ca+2, and ATP

Skeletal muscles are usually attached to bones and are responsible are voluntary actions. The muscle, when viewed under a microscope, has light and dark bands called striations. Most of the skeletal muscles are control by the nervous system. The muscles consist of muscle fibers, connective tissues, blood vessels, and nerves.

Smooth muscles are found in the stomach, blood vessels, and the large and small intestines. They help move food through the digestive system, controls blood flow, and changes the size of your pupil in light. Most smooth muscles can function without nervous stimulation since they are connected, which allows electric impulses to travel from one cell to another.

Cardiac muscle is found only in the heart. Cardiac muscle is similar to skeletal muscle, except cardiac muscles have smaller cells. It is also similar to smooth muscle because they are connected and do not need the nervous system to function.

Muscle fibers are made of smaller structures called filaments. Thick filaments contain a protein called myosin. Thin filaments are made up mainly of another protein called actin. They are arranged in units, called sarcomeres. When a muscle relaxes, there are no thin filaments in a sarcomere. “A muscle contracts when the thin filaments in the muscle fiber slide over the thick filaments”. ATP supplies the energy needed for muscle contraction. ATP can be produced by either cellular respiration or fermentation.

Acetylcholine is a neurotransmitter that is released by vesicles. They produce an impulse in the cell membrane of the muscle fiber, which causes the release of calcium ions in the fiber. A muscle cell stays contracted until the release of acetylcholine stops and any remaining is destroyed by an enzyme.

Tendons join skeletal muscles to bones and cause them to work like levers. A few muscle cells are being stimulated while others are not. That causes some muscles to tighten, which is called resting muscle tone. It’s responsible for keeping the back and legs straights and the head upright.

Integumentary System

Structures Skin, hair, nails, sweat and oil glands

Function Acts as a barriers against infection and injury, helps regulate body temperature, provides protection against radiation from sun

State Standards

● Students know the role of the skin in providing nonspecific defenses against infection.

The skin’s main purpose is for protection. It’s made up of two layers: the epidermis and the dermis. The epidermis itself has two layers. The outer layer is made of dead cells, while the inner layer is made of living cells. Older cells that move up being making keratin, a tough protein. The outer layer of skin is shed or washed away once every four to five weeks. Melanocytes in the epidermis produce melanin, a dark brown pigment.

The dermis lies beneath the epidermis and consists of fibers, blood vessels, never endings, glands, sense organs, muscles, and hair follicles. The blood vessels narrow or widen, depending on the outside temperature that limit of increase heat loss. The dermis also contains sweat glands and oil glands. Release of perspiration is stimulated by nerve impulses.

Hair and nails are made up of mostly keratin. Hair on the head protects the scalp from light from the sun and provides insulation from the cold. Hairs in ear canals, nostrils, and around the eyes are there to prevent dirt and small particles from entering the body. Hair follicles are structures where hair is produced. They are pockets of epidermal cells that extend down into the dermis. Nails serve to protect the tips of the fingers and toes. They grow from the nail root, where cells are constantly dividing. The cells of the nail root fill with keratin and produces a tough nail on the tips of fingers and toes. Fingernails grow about three millimeters per month, about four times as fast as toenails.

Respiratory System

Structures Nose, pharynx, larynx, trachea, bronchi, bronchioles, lungs

Function Provides oxygen for cellular respiration and removes carbon dioxide from the body

State Standards

● Students know how the complementary activity of major body systems provides cells with oxygen and nutrients and removes toxic waste products such as carbon dioxide.

Respiration is defined as the release of energy from the breakdown of molecules in food in the presence of oxygen. Air moves through the nose to a tube called the pharynx, a passageway for both air and food. Then the air moves from the pharynx into the trachea (windpipe). The larynx, which contains two elastic folds of tissue called vocal cards, enable us to produce sounds. The air then passes from the larynx, through the trachea, and into two passageways in the chest called bronchi, which leads to the lungs. The real work of the respiratory system takes place in alveoli (tiny air sacs) that are surrounded with thin capillaries. The lungs are sealed in two sacs, and at the bottom of the chest cavity is a flat muscle called the diaphragm. The brain controls breathing in a center in the medulla oblongata.

“There are about 350 million alveoli in a healthy lung, providing an enormous surface area for gas exchange”. Carbon dioxide in the bloodstream diffuses in the opposite direction as oxygen. The lungs remove about one third of the oxygen in the air and increases the carbon dioxide content of that air by a factor of 100. Hemoglobin, the oxygen-carrying protein in the blood, is needed for efficiency. It increases the oxygen-carrying capacity of the blood.

When you breath, the diaphragm contracts and expands. It creates a partial vacuum inside the chest cavity. Breathing only works because the chest cavity is tightly sealed. Chest wounds are particularly serious because if the chest is punctured, air can leak into the chest cavity and make breathing impossible.

Breathing can not be completely controlled because the nervous system does not let you since it’s such an important function. The brain controls the breathing in a center in the medulla oblongata. Cells in the breathing center keep track of the amount of carbon dioxide in the blood.

When the level of carbon dioxide rises, nerve impulses from the breathing center makes the diaphragm contract, which brings air into the lungs. The strength of the impulse depends on the level of carbon dioxide.

While oxygen decreases as altitude increases, passengers in a plane do not need oxygen masks because the cabin is pressurized. Even though their bodies are starving for oxygen, they have no more carbon dioxide in their blood than usual.

The lungs in the respiratory system can be damaged by dust and foreign particles, especially tobacco. Nicotine, carbon monoxide, and tar are three of the most dangerous substances to the body. Nicotine increases heart rate and blood pressure. Carbon monoxide is a poisonous gas that blocks the transport of oxygen in the blood and deprives the heart of the oxygen they need in order to function. Tar also causes cancer. Smoking causes coughing and reduces air flow to the alveoli.

Smoking reduces life expectancy. It can cause respiratory diseases such as chronic bronchitis, emphysema, and lung cancer.

Excretory System

Structures Skin, lungs, kidneys

Function Removes and eliminates metabolic wastes such as excess salts, carbon dioxide, and urea

State Standards

● Students know the homeostatic role of the kidneys in the removal of nitrogenous wastes and the role of the liver in blood detoxification and glucose balance. ● Students know how hormones (including digestive, reproductive, osmoregulatory) provide internal feedback mechanisms for homeostasis at the cellular level and in whole organisms.

Homeostasis not only involves the outside environment, but it also requires the body to deal with internal processes and might disturb the cellular environment. Each cell in the body produces waste, including salts, carbon dioxide, and urea (a toxic compound produce when amino acids are used for energy). The skin is the organ that excretes water and salts, and small amounts of urea as sweat. The lungs excrete carbon dioxide as well. The kidneys are another part of the excretory system. The kidneys are located on either side of the spinal cord, with a tube called the ureter carrying urine to the urinary bladder. The kidneys collect waste as urine and the clean filtered blood is returned to circulation.

The inner part of the kidney is called the renal medulla, and the outer part is called the renal cortex. Nephrons are small, processing units of the kidney. It filters and purifies blood. There are three stages of purification: filtration, reabsorption, and secretion.

Most filtration occurs in the glomerulus. Fluids flows from the blood into Bowman’s capsule. The kidneys filter the blood every forty-five minutes. During reasborption, material removed from the blood goes back into the blood. 99% of the water that goes into Bowman’s capsule is reabsorbed into the blood.

The material that remains after reabsorption is urine. It is then minimized in the loop of Henle.

Kidneys regulate the water content of the blood, maintain blood pH, and remove waste products from the blood. The activity of the blood is controlled mainly by the composition of the blood.

Humans can survive with only one kidney. However, if both are damaged, they can get a kidney transplant or a kidney dialysis machine.

Endocrine System

Structures Hypothalamus, pituitary, thyroid, parathyroids, adrenals, pancreas, ovaries

Function Controls growth, development, metabolism, and reproduction

The endocrine system is made up of glands that release substances out into the bloodstream, which broadcast messages throughout the body. Hormones are chemicals that travel through the bloodstream and affect other cells’ activities. Target cells are cells that have receptors for a certain hormone.

Hypothalamus: makes hormones that control the pituitary gland

Pituitary gland: produces hormones that control many of the other endocrine glands

Thymus: releases thymosin, which stimulates T-cell development

Adrenal glands: deals with stress

Pineal gland: involved with rhythmic activities

Thyroid: regulates metabolism

Pancreas: produces insulin and glucagon, which regulate the level of glucose in the blood

Ovary: produces estrogen and progesterone and prepares the uterus for a fertilized egg

The pituitary gland is a small bean shaped structure located at the base of the skull. It releases hormones that control many body functions and controls other endocrine glands.

Hypothalamus controls secretions of the pituitary gland. It’s influenced by the levels of hormones in blood.

The thyroid gland has the most important role in regulating the body’s metabolism. Thyroid cells produce thyroxine, which affects almost all of the cells in the body by regulating their metabolic rates.

Adrenal glances helps the body prepare for and deal with stress, and consists of an outer part called the adrenal cortex and an inner part called the adrenal medulla. A hormone called cortisol helps control the rate of metabolism of carbs, fats, and proteins.

The nervous system regulates the release of hormones from the adrenal medulla. The adrenal medulla releases two hormones: epinephrine and norepinephrine. It also produces the “fight-or-flight” response to stress, which occurs whenever one is excited or scared.

The pancreas releases insulin and glucagon to keep the glucose in the blood stable. It causes sugar to be removed from the blood and stores it as glycogen or fat. It also makes the liver break down or release glucose back into the blood.

Digestive SystemStructures Mouth, pharynx, esophagus, stomach, small and large intestines

Function Coverts food into smaller molecules, absorbs food

State Standards

● Students know the individual functions and sites of secretion of digestive enzymes (amylases, proteases, nucleases, lipases), stomach acid, and bile salts.

The mouth beings the work of the digestive system. The teeth is used to tear and crush food, which begins mechanical digestion (breaking down large pieces of food into smaller pieces). Saliva helps moisten the food and make it easier to chew and swallow. It eases food through the digestive system. It contains amylase, an enzyme that breaks chemical bonds between sugar monomers in starches. After food is swallowed, enzymes begin to break down food molecules into smaller molecules. The process is called chemical digestion.

Once chewed, the clump of food also called a bolus is pushed down the throat, passes through the esophagus, and goes into the stomach. Food does not travel down the esophagus because of gravity, it is pushed down by contractions of smooth muscle. The cardiac sphincter, a thick ring of muscle, prevents food from moving back up the esophagus.

The combination of pepsin and hydrochloric acid starts the process of protein digestion.

Stomach muscles contract to churn and mix stomach fluids and food, which produces a mixture called chyme. After an hour or two, the chyme is released and flows into the small intestine.

After the chyme is pushed out, it enters the duodenum, the first of three parts of the small intestine. It’s where most of the chemical digestion takes place. When it enters the duodenum, it mixes with enzymes and digestive fluids from the pancreas, the liver, and the lining of the duodenum.

Below the stomach is the pancreas, which produces hormones and enzymes and sodium bicarbonate, a base that neutralizes stomach acid so they can be effective. The liver helps the pancreas with its job by making bile, a fluid filled with lipids and salts. It dissolves and disperses droplets of fat found in fatty foods. That makes it possible for enzymes to reach and break down fat molecules.

The rest of the small intestine consists of the jejunum and the ileum, which are about three meters long. When it enters these two parts of the small intestine, chemical digestion would have been almost completed. The surfaces of the intestine is covered with villi which makes it easier for nutrient molecules to be absorbed. Molecules of fat and fatty acids are absorbed by lymph vessels called lacteals.

When food finally leaves the small intestine, it’s mostly nutrient-free. Only water, cellulose, and other indigestible substances are left behind. The large intestine removes water from the material that is left. Water is quickly moved across the wall of the large intestine. Bacteria growing on the material help digestive process. Some bacteria produces compound that can be used by the body, like vitamin K. The waste material that is left after the water is removed by passed out and eliminated from the body. When water is not removed from the waste, it creates a condition known as diarrhea, which results from bacterial infections and drinking contaminated water.

Immune ResponseStructures Skin, inflammatory response, interferons

Function Defends the body against pathogens and guards the body against infections

State Standards

Students know the role of the skin in providing nonspecific defenses against infection.

Students know the role of antibodies in the body's response to infection.

Students know how vaccination protects an individual from infectious diseases.

Students know there are important differences between bacteria and viruses with respect to their requirements for growth and replication, the body's primary defenses against bacterial and viral infections, and effective treatments of these infections.

Students know why an individual with a compromised immune system (for example, a person with AIDS) may be unable to fight off and survive infections by microorganisms that are usually benign.

The body’s most important barrier against pathogens is the skin. However, it can easily be infected with a minor scrape or cut. Pathogens can enter through the skin and afterwards can multiply, which causes an infection with redness, swelling, and pain. However, if bacteria enters the body through the nose or mouth, there are several ways the body eliminates them. Mucus in the throat and nose can trap viruses and keep them from entering. The cilia in the lungs pushes the bacteria away. If they make their way to the stomach, stomach acid and digestive enzymes will destroy them. Bodily secretions (mucus, saliva, sweat, and tears) also gets rid of pathogens.

When pathogens enter the body, they can multiply and release toxins. Once that occurs, the inflammatory response is activated. The tissue area may become swollen and painful as white blood cells released from the expanded blood vessels are engulfing the bacteria. When many pathogens are detected, a fever may also occur. A fever means that body temperature is elevated, and the heat can fight off pathogens, as well as increase white blood cell production.

Interferons are also produced by virus infected cells to help slow down infection and give the immune system time to respond.

If a pathogen still gets past those defenses, an antigen will trigger the immune response. B cells produce antibodies, which are proteins that destroy pathogens.

Cell-mediated immunity, another immune response, causes the pathogen cell to rapidly loss material and die. It is important in regards to diseases especially caused by eukaryotic pathogens.

Killer T cells make it difficult to transplant organs. The second person’s organ is recognized as foreign and attacks it. The immune system ends up damaging and destroying the new organ.

Some people are have a permanent immunity. If they survive a disease, it would not develop a second time. “Once the body has been exposed to a pathogen, millions of memory B and T cells remain capable of producing specific antibodies to that pathogen”.

A vaccination can be injected to weaken a pathogen and produce immunity. The body of the person getting vaccinated can mount an immediate immune response against the pathogen after getting a vaccine.

Reproductive System

Structures Testes, epididymis, vas deferens, urethra, penis (male), vagina (female)

Function Produces reproductive cells, nurtures embryo for females

The primary reproductive organs are the ovaries in the female and the testes for male.

The female reproductive system usually does through the menstrual cycle, in which an egg is released so that it can be fertilized. The lining of the uterus is eliminated. The phase lasts about four to five days.

In order for a woman to become pregnant, the sperm must swim through the cervix and meet with the released egg. One sperm must enter the egg for their nuclei to fuse, which is called fertilization. The egg then beings to divide and develop further to produce progesterone.

Works Cited

1.) Google Image Search2.) ClipArt.com3.) Biology Textbook 4.) http://mcb.berkeley.edu/courses/mcb135k/outline/repro.html5.) http://training.seer.cancer.gov/module_anatomy/unit12_1_repdt_intro.html6.) http://www.biotopics.co.uk/human2/reprsy.html7.) http://www.cerebromente.org.br/n07/fundamentos/neuron/parts_i.htm

Quoted Work From: Biology Textbook