Digestive system Mechanical digestion- mouth teeth, stomach Chemical digestion- stomach, small intestine Hydrochloric Acid made by stomach lining Enzymes: Amylase in saliva breaks down starch in the mouth; Pepsin breaks down proteins into small peptides in acidic stomach Many enzymes made by the pancreas break down all carbs, proteins and nucleic acids in small intestine until they are small enough tobe absorbed. Bile salts break down fats into small droplets to be absorbed by the lymphatic system. Mouth, pharynx, esophagus, stomach, small intestine, large intestine, colon, anal sphincter. Only the first two and the last are voluntary. The rest moves involuntarily by peristalsis. The large intestine absorbs water, makes vitamins and forms solid feces. Purpose to break down food mechanically into small pieces then break down polymers into monomers so they can be absorbed by diffusion into the circulatory system. Excretory system: homeostasis of blood fluids and nutrients/wastes. Kidney filters out molecules from the blood such as urea (nitrogenous wasete), water, sugar, and salts. By diffusion, and sometimes active transport, the kidney nephrons reabsorbs necessary molecules (water if you are dehydrated, sugar if you are hypoglycemic). Waste molecules or excess molecules are sent to the bladder for storage, then out the urethra when you excrete (pee). Hormones like ADH help to regulate water balance and protect from dehydration. Circulatory system delivers nutrients throughout the body and collects CO2 and delivers O2 to all cells. Arteries move blood away from the heart. Veins bring blood back to the heart. There is a pulmonary circuit for gas exchange to the lungs, and a systemic system that moves blood throughout the body. Capillaries are small and are where exchange of gas nutrients or wastes. Each cell of the body is no more than a few cells away from a capillary. The heart has 4 chambers: the right atrium which collects blood from the body, the right ventricle which pushes blood to the lungs, the left atrium that collects blood from the lungs and the left ventricle that pushes blood out to all parts of the body. Muscles in the arms and legs help to push blood back to the heart (why you must stay active for good circulation in the legs). Skeletal and muscular system work together for movement. Voluntary muscle is striated. Involuntary muscle/Smooth muscle is not. Muscles move in pairs- examples are: biceps and triceps tendons attach muscle to bone - ex. achilles tendon heel bone to calf muscle. ligaments attach bones together Nervous system The central nervous system consists of the brain and the spinal cord. The peripheral nervous system consists of sensory neurons (nerve cells) and motor neurons. Sensory neurons pick up stimuli messages and send them to the spinal cord, they go through the spinal cord and out to the motor neuron to move your muscle in an instant response. This path is called the arc reflex. Another message is sent to the brain to activate the thought process to interpret what information was received and how to further respond to it. The arc reflex is autonomic and not under your control (e.g. flinching or the rubber hammer to the knee at the Dr’s office).