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Discuss how cellular structures, including the plasma membrane, specialized endoplasmic reticulum, cytoskeletal elements, and mitochondria, function together in the contraction of skeletal muscle cells. The plasma membrane of a muscle cell (the sarcolemma) is an excitable membrane, meaning that it can propagate an action potential. You need to explain how the membrane and transverse tubules (T tubules) propagate the action potential. The specialized endoplasmic reticulum of a muscle fiber (i.e., muscle cell) is called the sarcoplasmic reticulum. It stores Ca2+ (calcium ions). When released, the calcium ions cause contraction; when actively transported back into the sarcoplasmic reticulum, the dropping levels of calcium ions in the cytoplasm cause muscle contraction to cease. The cytoskeletal elements refers to the microfilaments, made of actin, and the associated proteins, such as myosin. Together, these various proteins form units called sarcomeres; these are the functional un...

Describe the negative and positive feedback loops, and discuss how feedback mechanisms regulate each of the following. The menstrual cycle in nonpregnant human female.  Blood glucose levels in humans. Negative feedback loops occur when the substrate cause a decrease in the hormone that is stimulating it keeping the substrate at a constant or near constant level. For example estrogen and FSH. This can also happen if the substrate increases the hormone which regulates its excretion. For example calcium and calcitonin or glucose and insulin.

The graph below shows the response of the human immune system to exposure to an antigen. Use this graph to answer part a and part b of this question. A) Describe the events that occur during period I as the immune system responds to the initial exposure to the antigen.  B) Describe the events that occur during period II following a second exposure to the same antigen.  C) Explain how infection by the AIDS virus (HIV) affects the function of both T and B lymphocytes. A) the first time the body is exposed, selective proliferation and differentiation of lymphocytes occur. Selected B cells produce antibody-secreting effector B cells (plasma cells) and selected T cells are activated to their effector forms. Eventually, T cells clear the antigen from the body. B) The second time the same antigen is exposed, the response is faster. The antibodies produced in the secondary immune response have a greater affinity for the antigen.Clones of the T and B memory cells gener...

Many physiological changes occur during exercise. Design a controlled experiment to test the hypothesis that an exercise session causes short-term increases in heart rat and breathing rate in humans.  Explain how at least three organ systems are affected by this increased physical activity and discuss interactions among these systems. A) Two groups made up of 100 people, all of about the same body size, and age. Each is monitored for heart rate, and respiration rate during the test. You have the test group run for 30 minutes, and have the control group simply stand for 30 minutes. After the test is done, compare the test and the control group creating graphs of both. B) Circulatory- The body increases blood flow to carry oxygen and nutrients to the working muscle cells, and to carry excess CO2 out of the body. Respiratory- The body increases the rate of respiration to expel the extra CO2 gas that is being produced by the working muscle cells while they are preformi...

Describe the following mechanisms of response to foreign materials in the human body.  A) The antigen-antibody response to a skin graft from another person.   B) The reactions of the body leading to inflammation of a wound infected by bacteria. A) The antigen recognizes the new skin as foreign. Then it is rejected by the immune system. The antigens surface to the graft cells. Then they stimulate antibody production and T cell production. B Lymphocytes are turned into plasma cells which synthesizes antibodies. The antibodies circulate to the sites needed and precipitate antigens and/or complex. The antibodies make the antigens susceptible to phagocytosis by WBCs. Then the antibodies specify and it fights off the graft and other infections that come with it. B)When injured, mast cells release their histamine which triggers dilation and it increases permeability of nearby capillaries. Activated macrophages and other cells discharge additional signals that further p...

Describe the processes of fat and protein digestion and product absorption as they occur in the human stomach and small intestine. Include a discussion of the enzymatic reactions involved. 1. Stomach: Region- Cardiac and pyloric sphincter Layers of muscle and thick walls Digestive Function: a) Chief cells secretes renin, lipase, and pepsinogen b) Parietal cells Secretes HCL c) mucus protects stomach Endocrine Function: Gastrin Function: stimulates production of digestive juices Presence of food: stimulus for gastrin release 2. Small Intestine: Contains villi which are blood vessels Region: duodenum Digestive Function: 3 enzymes= lipase, amylase, nuclease Function: Bile= produced in liver, stored in gall bladder, emulsifier Endocrine Function: Stimulates release of alkaline secretions by pancreas, stimulates gallbladder to release bile, stimulates pancreas to secrete digestive enzymes. 3. Pancreas: Connects to small intes. by pancreatic duct made up of exocr...

Describe the structure of a mammalian respiratory system. Include in your discussion the mechanisms of inspiration and expiration. From the nasal cavity and pharynx inhaled air passes through the larynx, trachea, and bronchi to the bronchioles, which end in microscopic alveoli lined by a thin, moist epithelium. branches of the pulmonary arteries convey oxygen poor blood to the alveolar, branches of the pulmonary veins transport oxygen rich blood from the alveoli back to the heart. Air enters through the nostrils and is then filtered by hairs warmed, humidified, and sampled for odors as it flows through a maze of spaces in the nasal cavity. As the external intercostals & diaphragm contract, the lungs expand. The expansion of the lungs causes the pressure in the lungs (and alveoli) to become slightly negative relative to atmospheric pressure. As a result, air moves from an area of higher pressure (the air) to an area of lower pressure (our lungs & alveoli). During inspirati...