Human Physiology

1. Human Physiology By: Ian Pendleton

2. Overview • There are eleven main organ systems that make up the human body. They are made up of combinations of different tissues, and work together to create a person. They are the circulatory, nervous, respiratory, excretory, endocrine, digestive, muscular, immune, integumentary, reproductive, and skeletal systems.

3. Circulatory System • 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. • The circulatory system has three main parts: the heart, the blood, and the blood vessels. It also connects with organs from other systems, such as the lungs, intestines, and kidneys to add nutrients and remove waste from the blood. This will be elaborated on later.

4. The Heart • The heart is an organ about the size of a fist that is made up almost entirely of muscle. There are three layers to the heart, two protective layers, and the middle layer, or myocardium. The myocardium is the powerful muscle that contracts to send blood rushing through your body.

5. The Heart • The heart is divided into two sides by a wall, called a septum. On each side of the septum there are two chambers. The upper chamber which receives blood and is called the atrium. The lower chamber pumps blood out of the heart and is called the ventricle. There are a total of four sections to the heart, a right atrium and ventricle, and a left atrium and ventricle.

6. The Heart • The heart is actually two separate pumps. Each side of the heart functions as a pump to a different part of the body. The right side of the heart pumps blood between the heart and the lungs, and is known as pulmonary circulation. The left side of the heart pumps blood to the rest of the body, and is known as systemic circulation.

7. Pulmonary and Systemic Circulation • Pulmonary circulation is the movement of blood to the heart. Pulmonary arteries pump blood with large amounts of carbon dioxide to the lungs, where the carbon dioxide is exchanged for oxygen. The oxygen rich blood is then pumped back to the heart by the pulmonary veins to be transported to the rest of the cells in the body. Systemic Circulation is the flow of blood from the heart to the rest of the body.

8. Blood • Blood is an extremely important substance. It brings nutrients to cells, and removes waste from them. It also helps regulate parts of homeostasis, such as body temperature. It is also important for fighting off infections, and creating clots to repair damaged blood vessels. Blood is about half plasma, and half red blood cells, with a few white blood cells and platelets added. White blood cells are a part of the immune system.

9. Blood Vessels • Blood vessels are small tubes that move blood throughout the body. Arteries are blood vessels that move blood from the heart to the rest of the body. Veins then take the blood back to the heart to be replenished. They meet in capillaries, which are extremely tiny vessels. Capillaries are where nutrients are dropped off and wastes picked up through diffusion.

10. Skeletal System • The skeletal system is made up of bones and various connective tissues. It provides support for the body, protects internal organs, stores minerals, and is the center of blood cell creation. • The skeletal system also provides a system of levers, called joints, that allow muscles to move the body. There are five main types of joints.

11. Skeletal System • The first type is the ball and socket joint. It allows a wide range of movement. One example of this is the hip. • The next type is the Condyloid or ellipsoid joint. This provides movement is one direction, and limited movement in another. An example is the knee. • The third type is the saddle joint. This allows the same type of movement as the condyloid joint. The thumb is an example. • Hinge joints, such as the elbow, allow movement in on only one plane, like a door hinge. • The elbow is also an example of a pivot joint, which allows for rotation of one bone around another.

12. Muscular System • There are three types of muscles in the human body: smooth, cardiac, and skeletal. • Smooth muscles are involuntary, so you don’t have conscience control over them, and they don’t get fatigued. They are found in the intestines, throat, and blood vessels. • Cardiac muscles are also involuntary, but they are found only in the heart. They are what causes the heart to beat, pumping blood throughout the body. • Skeletal muscles are the muscles attached to the skeletal system, they allow the body to move. Smooth Cardiac Skeletal

13. Muscular System • Students know the cellular and molecular basis of muscle contraction, including the roles of actin, myosin, Ca+2, and ATP. • Skeletal muscles are made up of bundles of muscle fibers, which are themselves made up of myofibrils. Each myofibril is composed of actin and myosin filaments, which can be sub-divided into sacromeres. Sacromeres are separated from each other by Z disks. • When the nervous system sends the signal to contract a muscle, calcium ions (Ca+2) are released, which affect the interactions between the myosin and actin. The actin then use ATP as energy to slide over the myosin, causing the sacromere to be shorter. When all of the sacromeres contracts simultaneously, the muscle contracts and it pulls the bone it is attached to with it. This causes movement. Amazingly, this all happens within milliseconds of receiving the signal from the nervous system.

14. Nervous System • Students know the functions of the nervous system and the role of neurons in transmitting electrochemical impulses. • The nervous system is the system that controls and coordinates functions throughout the body, and responds to both internal and external stimuli. • The messages that the nervous system transmits are electrical currents called impulses. The cells that transmit these impulses are called neurons.

15. Nervous System • Students know the roles of sensory neurons, interneurons, and motor neurons in sensation, thought, and response. • There are three classifications of neurons: Sensory neurons, interneurons, and motor neurons. • Sensory neurons carry information from sense organs to the spinal cord and brain. • The information is then processed by interneurons and then a response to the information is sent out to the motor neurons. • The motor neurons then activate the correct response for the situation.

16. Nervous System • Students know how the nervous system mediates communication between different parts of the body and the body's interactions with the environment. • The nervous system is the control station of the human body. It connects the senses to the brain, so that you can understand what you are sensing. It also responds to the body’s environment. For example, if it was too hot outside, the nervous system would send an impulse to the brain to slow down activity, thereby producing less heat.

17. Nervous System • The largest part of the neuron is the cell body. This contains the nucleus and most of the cytoplasm. • Spreading away from the cell body are short, branched extensions called dendrites. These carry impulses from the environment and other neurons to the cell body. • A long branch called an axon also extends from the cell body. This is used for taking impulses from the cell body, away to other cells. Although a cell usually has many dendrites, it generally has only one axon. • The axon is also sometimes surrounded by a myelin sheath. The sheath also leaves gaps in its covering, called nodes. An impulse can jump from node to node, increasing its speed.

18. Integumentary System • The integumentary system is the system that covers the entire body: skin, hair, nails, and the glands associated with them. Skin is the largest part of the integumentary system, and contains several layers of sensory receptors. Due to this, it is this system that transmits sensations like heat, cold, pain and pressure to the nervous system.

19. Integumentary System • The skin is made up of two main layers, the dermis and the epidermis. • The epidermis is the upper layer of skin. The part that actually comes in contact with the environment is all dead cells, while the living cells are underneath. • The dermis is beneath the epidermis, and contains blood vessels, nerve endings, glands, sense organs, smooth muscles, and hair follicles.

20. Integumentary System • Hair is almost everywhere on the human body, and it is important. The hair on the top of the head protects the scalp from damaging ultraviolet rays. The hair in the nose, ears, and around the eyes prevents harmful materials from entering the body. • Nails protect the fingertips and toes. They grow from the nail root, a rapidly dividing area of cells. Fingernails grow around four times faster than toenails.

21. Respiratory System • The job of the respiratory system is to exchange the body’s waste of carbon dioxide for much needed oxygen. The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, and lungs. • The nose, or nasal passageway, is where oxygen enters the body and carbon dioxide leaves. However, the mouth can also serve the same purpose.

22. Respiratory System • The pharynx is a passageway for both air and food. Air moves from the pharynx into the trachea. When swallowing food, a piece of cartilage covers the trachea. While passing through the trachea, the air must be cleaned and moistened, so as not to harm the lungs. Nasal hair traps the large dust particles, and a layer of mucus moistens the air and traps smaller particles. Cilia remove the dirt and mucus from the trachea, and what is left is either swallowed or spit out.

23. Respiratory System • The larynx is your voice box, and when muscles contract it, the air flowing through it cause the sounds we produce when we speak. • The trachea then splits into two bronchi, one going to each lung. Within each lung, the bronchi divide into smaller bronchi which lead to smaller passageways called bronchioles. The bronchioles continue to subdivide until they reach alveoli.

24. Respiratory System • In the alveoli, oxygen from the air diffuses through the capillaries and into the blood. At the same time, carbon dioxide from the blood diffuses into the alveoli. The respiratory system is quite efficient at gas exchange. The exhaled air has about one-third of its oxygen removed, and has 100 times more carbon dioxide than it had when it entered.

25. Digestive System • The digestive system is a one-way passageway through the body. It includes the mouth, pharynx, esophagus, stomach, small intestines, large and large intestines. The salivary glands, pancreas and liver add secretions to the digestive system. • Food starts out in the mouth. The purpose of the mouth is to convert large food materials into smaller particles that will be easier to digest.

26. Digestive System • Students know the individual functions and sites of secretion of digestive enzymes (amylases, proteases, nucleases, lipases), stomach acid, and bile salts. • Amylase is chemical found in saliva that brakes the bonds between sugar monomers and starch. It is produced with the saliva in the salivary glands. • The food is then passed though the pharynx and into the esophagus. Muscle contractions in the esophagus pull food down into the stomach.

27. Digestive System • In the stomach, stomach acids digest the food and allow for nutrients to be removed. The stomach eventually turns the food into a substance called chyme. The chyme is then moved into the small intestines. • In the small intestines, chemicals are added to the chyme to help with the digestion of chemicals.

28. Digestive System • Protease, nuclease, and lipase are added in the small intestines. • Protease is a chemical that breaks the peptide bonds between amino acids in proteins. This allows for the proteins in the foods we eat to be reused to create our own proteins. • Nuclease breaks the bonds between the subunits of nucleic acid, thereby allowing the parts to be reused during DNA replication. • Lipase breaks down fat, which allows for greater energy digestion.

29. Digestive System • Below the stomach is pancreas. The pancreas produces hormones which regulate blood sugar levels. It also produces the enzymes in the last slide, along with a few others for breaking down substances. Finally, it produces sodium bicarbonate, which neutralizes the stomach acids so that the enzymes can function. • Assisting the pancreas is the liver. The liver produces bile, a fluid loaded with lipids and salts. Bile is used to dissolve the fat found in fatty foods. Bile is stored in the gallbladder.

30. Digestive System • 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. • The liver is also important in the removal of toxins from the body. Although every biological tissue has the ability to remove toxins, the liver is the organ with the largest aptitude, and therefore the largest responsibility. • In addition, the liver helps to add balance to the glucose levels in the body. When glucose levels get too low, glucagon is released into the blood. The liver than converts the glycogen to extra glucose. If levels drop too low, insulin is released, which stimulates the liver to turn glucose back into glycogen.

31. Digestive System • When the food leaves the small intestines, just about all of the nutrients have been removed. The large intestine removes water from the material that is left. Bacteria live on the walls of the large intestine, and aid in the digestive process. Anything left after the water has been removed passes through the rectum and out of the body.

32. Excretory System • The excretory system is primarily the skin, lungs, and kidneys. The skin is the removal facility for sweat, which is excess water, salt, and small amounts of toxic urea. The lungs are the main removal facility for carbon dioxide. The kidneys do the rest.

33. Excretory System • Each kidney is connected by a small tube called a ureter to the urinary bladder. The urinary bladder is where urine is stored before it can be excreted.

34. Excretory system • 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. • The kidney’s job is to clean and filter the blood. Toxic, unclean blood enters the kidney through the renal artery. As blood travels through, it is filtered. Most of what gets filtered out is reabsorbed where it is needed, and the toxic wastes are moved to the urinary bladder as urine. The clean blood is then returned to the body through the renal vein. • The kidneys also work to promote homeostasis. If you drink too much water or eat too much salt, for example, your kidney would return less water and salt to your system, thereby maintaining homeostasis.

35. Endocrine System • The endocrine system is made up of glands which produce hormones that can affect your entire body at once. • Hormones can target specific cells by only connecting to cells that have the correct receptors. Hormones are generally slower and longer lasting than nerve impulses, and can affect more cells.

36. Endocrine System • Students know how feedback loops in the nervous and endocrine systems regulate conditions in the body. • The nervous system sends out different messages depending on the situation, and when it has been fixed, it will stop sending those messages. Controlling body temperature is an example of this. • The endocrine system, however, is different. An example is the thyroid gland. Thyroxine affects the activity of cells, and therefore the amount of heat they produce, and is created by the thyroid. When the thyroxine levels need to be higher a hormone called TRH is released, which stimulates the creation of TSH. TSH gets the thyroid to create more thyroxine, which will in turn tell the brain to stop producing TRH. If thyroxine levels were to drop again, nothing would stop the production of TRH, and thyroxine levels would increase.

37. Endocrine System • Students know how hormones (including digestive, reproductive, osmoregulatory) provide internal feedback mechanisms for homeostasis at the cellular level and in whole organisms. • The pancreas uses insulin and glucagon to regulate blood sugar levels. As earlier stated, when levels drop too low, the pancreas releases glucagon, and when the get too high, insulin is released. The liver then responds accordingly.

38. Reproductive System • The male reproductive system has five main parts: the testes, the epididymis, the vas deferens, the urethra, and the penis. The testes produce sperm, the male reproductive cell. The epididymis stores sperm until it matures. The vas deferens moves the sperm up to the urethra. During ejaculation, the sperm is released out through the urethra, which is being protected by the penis.

39. Reproductive System • The female reproductive system has four main parts. The ovaries, Fallopian tubes, uterus, and vagina. The ovaries release an egg, the female reproductive cell, about once a month. It travels down the Fallopian tubes, where it has the chance to be fertilized by sperm. If it is, it will implant on the uterine wall, and a baby will begin to develop. If it is not fertilized, it will pass out of the woman’s body during menstruation. The vagina is the “birth canal” through which a baby would be born.

40. Immune System • The immune system is the body’s defense system against pathogens, which include germs like bacteria and viruses. • Students know the role of the skin in providing nonspecific defenses against infection. • The body’s first line of defense is the skin. Few pathogens can penetrate the layer of dead cells to achieve the penetration required to make a person sick. It is considered nonspecific because it will try to stop any kind of germs, it does not target certain ones.

41. Immune System • Students know the role of antibodies in the body's response to infection. • Students know the roles of phagocytes, B-lymphocytes, and T-lymphocytes in the immune system. • Antibodies are y-shaped proteins produced by B-lymphocytes. They attach themselves to certain antigens, and then link themselves together, creating a massive clump of pathogens. This attracts phagocytes, cells which engulf and destroy germs. They then destroy the entire clump at one time.

42. Immune System • When an antigen gets into the body, only a small number of the body’s B-cells will have the right antibody to fight it. The ones that do will rapidly grow and divide, producing a large number of specialized cells called plasma cells. The plasma cells then release the antibodies in huge amounts. The activation of these plasma cells is regulated by T-lymphocytes. • Students know how vaccination protects an individual from infectious diseases. • A vaccination is an artificial way to bolster your immune system. A vaccine is an injection of dead viruses which can then teach your antibodies how to fight those viruses if they were alive.

43. Immune System • 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. • There are many differences between bacteria and viruses. Bacteria can break down tissues and release toxins, but a virus takes control of host cells and copies itself until the host bursts. Bacteria can be killed with antibiotics, but once a virus takes hold, it’s up to your immune system to protect you. Bacteria are also usually transmitted through nonliving substances, while viruses generally rely on a living carrier to spread them.

44. Immune System • 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. • When a person’s immune system loses its effectiveness, routine germs that are normally fought off with ease cause major problems. They never get killed, and each new infection brings with it a new slew of problems, that increase with time. If the immune system is not working properly, the mechanisms that are relied on to fight off diseases simply do not work. This will generally lead to death if nothing can be done to increase the immune system again.

45. Bibliography • “Anatomy of the Human Circulatory System”. users.rcn.com. 10 August 2003. <http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Circulation.html> • Cardoso, Silvia. “Parts of the Nerve Cell and Their Functions”. www.cerebromente.org. <http://www.cerebromente.org.br/n07/fundamentos/neuron/parts_i.htm > • Miller, Kenneth R., Levine, Joseph S. Biology. Upper Saddle River, New Jersey: Pearson Education, Inc, 2002. • “The Endocrine System”. www.emc.maricopa.edu. 2001. M.J. Farabee. <http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookENDOCR.html >