Systems Biology - GED Science

The heart has four chambers: two atria and two ventricles. The atria are responsible for receiving blood returning from the body, while the ventricles pump blood out of the heart. The right ventricle pumps blood to the lungs, while the left ventricle pumps blood to the rest of the body.

The flow of blood through the heart is: right atrium, right ventricle, lungs, left atrium, left ventricle, body.

Arteries are the high pressure blood vessels responsible for carrying blood away from the heart. All arteries in the body travel away from the heart toward other tissues.

Most arteries carry oxygenated blood, but the pulmonary arteries carry deoxygenated blood; these vessels are responsible for transporting deoxygenated blood from the right side of the heart to the lungs. Veins are responsible for returning blood back to the heart. Arteries do not allow for diffusion of nutrients; this process primarily occurs in capillaries.

The heart is able to pump independently of the brain thanks to a collection of cells that fire impulses automatically. These cells are located in the sinoatrial node, which leads to the node's nickname as the "pacemaker" of the heart. Even without stimulation by a nerve, the heart can continue beating.

The heart is made of cardiac muscle tissue; smooth muscle tissue lines internal organs and blood vessels. Both sides of the heart pump at the same rate, but the left side pumps with more force. Each side of the heart must pump the same volume, but the left side must pump it a greater distance since it pushes blood to the entire body. A normal resting heart rate is around 60-80 beats per minute. A heart rate of 120 would be more typical during exercise.

The respiratory system allows air to travel to the lungs. Air enters the mouth or nasal passages, travels through the trachea, and then into the bronchi. The bronchi split into smaller and smaller bronchioles before terminating in small sacs called alveoli.

The aorta is a major artery that carries blood away from the heart. The urethra carries urine from the bladder. The small intestine is a portion of the digestive tract that carries nutrients from the stomach to the large intestine.

Blood is composed of multiple cell types that have specific functions in the body. The red blood cells (erythrocytes) help carry oxygen to the tissues in the body. The white blood cells (leukocytes) help defend the body from bacteria and other illnesses. Platelets are cell fragments responsible for helping blood clot, and are created by megakaryocytes.

The chief cells are responsible for releasing pepsinogen. Pepsinogen is an inactive enzyme that will only become activated in acidic conditions, such as those found in the stomach. Acid converts pepsinogen into pepsin, which helps chemically digest protein nutrients in the stomach.

Parietal cells release hydrochloric acid into the stomach, which activates pepsinogen. Goblet cells, or mucous cells, secrete mucous to help prevent degradation of the stomach lining.

The esophagus assists moving food into the stomach using a wave-like contracting motion called peristalsis. Swallowing initiates the process of peristalsis, but unlike swallowing, peristaltic contractions are not voluntary and are generated by smooth muscle.

Mastication is another term for "chewing." Emulsification refers to the grouping together of fat molecules when in an aqueous environment, particularly during digestion in the small intestine.

Food is digested to some degree in many different parts of the digestive system. The mouth, stomach, and small intestine all contribute to food digestion. The mouth contains salivary amylase, which breaks down carbohydrates. The stomach contains pepsin, which breaks down proteins. The small intestine contains several enzymes, such as lipase and trypsin, and breaks down carbohydrates, lipids, and proteins.

The esophagus, however, does not contribute to chemical digestion in any way.

Bile is created by the liver and released into the small intestine from the gall bladder during digestion. Because fat tends to clump in the aqueous environment of the duodenum, bile helps to increase the surface area of fat, a process called emulsification. This helps lipase break down the fats adequately.

There are three primary types of hormones: peptide hormones, steroid hormones, and tyrosine derivative hormones. Of the three, peptide hormones are the only polar hormones, so they cannot pass the cell membrane. As a result, they must attach to a membrane-bound receptor in order to elicit a response in the cell.

Tyrosine derivatives and steroid hormones are smaller, nonpolar molecules. This allows them to pass directly through the membrane, rather than binding to a receptor on the surface. Steroid hormones are derived from cholesterol, but there is no such thing as "cholesterol hormones."

Steroid hormones are created in the gonads and the adrenal cortex. They include testosterone, estrogen, cortisol, aldosterone, and progesterone.

Human growth hormone, oxytocin, and insulin are all peptide hormones, meaning that they are proteins made of amino acids. In contrast, steroid hormones are derived from cholesterol and have distinct ring structures.

Managing blood sugar levels is primarily the responsibility of the pancreatic hormones glucagon and insulin. Glucagon is responsible for raising blood sugar levels while insulin helps reduce the sugar levels.

Oxytocin is a hormone secreted from the posterior pituitary gland; it induces labor and contractions during childbirth. Thyroxine (also known as thyroid hormone or T4) is secreted from the thyroid and helps regulate metabolism.

The pituitary gland is responsible for a number of peptide hormones, including follicle-stimulating hormone, thyroid-stimulating hormone, and prolactin. Aldosterone, however, is produced in the adrenal cortex and functions to raise blood pressure by preventing fluid loss via urination.

B-cell lymphocytes are responsible for the production of antibodies. These white blood cells secrete antibodies, which bind to and promote the destruction of pathogens

Macrophages attack pathogens directly. T-cell lymphocytes can help attack pathogens as well, and can also trigger B-cells to release antibodies. Red blood cells (erythrocytes) are not involved in the immune response.

When it comes to blood type, the type of blood you have is determined by the type of antigens present on your red blood cells. For example, people with type A blood have the A antigen on their red blood cells, but not the B antigen. People with O blood have no antigens on their red blood cells. The immune system of a person with A blood will respond negatively to B blood if it is introduced into the body.

A person with type A blood could receive type A blood (A antigens) or type O blood (no antigens), but could not receive type B blood (B antigens) or type AB blood (A and B antigens).

Your innate immunity is the generalized system responsible for first attacking incoming infectious agents and toxins. Innate means that it is not necessary to have previously seen the pathogen, and the body always has these general defense mechanisms. Macrophages, neutrophils, and basophils are some of the primary cell types of innate immunity.

In contrast, the adaptive immune system is only effective against pathogens that have previously entered the body. A previous infection will result in the body producing antibodies during any later infections. T-cells and B-cells (lymphocytes) are the primary cell types of adaptive immunity.

Muscles do not attach directly to bones. Instead, a tendon is used to attach the two structures. Ligaments connect a bone to another bone, while joints are the locations where bones move around one another.

There are three types of muscle in the body: skeletal, cardiac, and smooth muscle. Of the three, skeletal muscle is the only one that can be consciously controlled. Cardiac and smooth muscle are controlled involuntarily.

An example of skeletal muscle is your biceps brachii muscle; you can voluntarily control this muscle to flex your arm. An example of smooth muscle is the muscle surrounding your arteries; you cannot voluntarily contract this muscle to constrict your arteries. Cardiac muscle is found in the heart; you cannot voluntarily choose to slow your heart rate.

Red bone marrow is found in the ends (epiphyses) of long bones such as the femur and is responsible for red blood cell development. Yellow bone marrow is found in the center (diaphysis) of long bones and can store fat for energy.

Blood filtration primarily occurs in the spleen or kidney. Glycogen is primarily stored in the liver. Calcium is released from the mineral matrix of the bone, but is not actually found in the bone marrow.