Transcript B 11.A
B 11.A Describe the role of internal feedback mechanisms in the maintenance of homeostasis. Vocabulary Central Nervous System Peripheral Nervous System Reflex Arch Negative Feedback Positive Feedback Central Nervous System The central nervous system consists of the brain and spinal cord and relays messages, processes information, and analyzes information. Peripheral Nervous System Consists of all the nerves and associated cells not part of the brain or spinal cord: Sensory Division – from sense organs to CNS. Motor Division – from CNS to muscles and glands Reflex Arch Sensory receptor, sensory neuron, motor neuron, and effector that are involved in a quick response to a stimuli. Negative Feedback When the body senses an internal change and activates mechanisms that reverse, or negate, that change. Example: When blood temperature becomes too high, the body responds by cooling itself down. Positive Feedback A process in which the body senses a change and activates mechanisms that accelerate or increase that change. Example: The presence of partially digested protein in the stomach triggers the secretion of hydrochloric acid and pepsin, the enzyme that digests protein. Internal Feedback Mechanisms Many body functions help maintain homeostasis: Feeding Respiration Circulation Excretion Movement Body Temperature Control Homeostasis and Digestive System: Stomach empty for several hours The individual eats something and contractions stop Stomach muscles begin to contract causing an unpleasant sensation Glucose levels begin to drop Homeostasis and Respiration/Breathing Exercise causes a build up of Carbon Dioxide in the blood. Oxygen from the air is brought into the lungs and the CO2 buildup is sent out of the lungs by exhaling. This signals the nerve impulses in the breathing center of the brain telling the diaphragm to contract. The higher the level of CO2 the stronger the impulses. Homeostasis and Circulation Other hormones are released into the bloodstream to help in the calming process. When the attack is over hormones are released to help the kidneys filter adrenaline from the bloodstream. The hypothalamus detects stress such as being attacked. The nervous system releases adrenaline into the bloodstream. Blood is directed toward muscles and limbs where more energy is required for running or fighting. Homeostasis and Excretion Excessive salt ingested causing high salt concentration in blood. Filtered blood leaves the kidneys with a normal salt concentration. Blood enters the kidneys where regulatory hormones control the filtration of excess salt from the bloodstream. Salt and wastes are collected and carried to the urinary bladder Homeostasis and Body Temperature Muscle fibers connected to hair follicles tighten to form warm air pockets (goose bumps). Muscles become active involuntarily causing shivering (can increase heat production x 5). Body is exposed to extremely cold temperatures. Hypothalamus activates to control heat loss. Blood flow is restricted to all non essential areas (fingers and toes) in order to maintain temperature of vital organs. Blood Flow and Thermoregulation Use the link below to view a model of thermoregulation. http://www.teachersdomain.org/asset/lsps07_i nt_heatexchange/ Thermoregulation Why do you get a fever when you are sick? http://www.teachersdomain.org/asset/tdc02_v id_fevervid/ Interdependent Body Systems See if you can maintain a young girl’s homeostasis in this interactive activity. http://www.teachersdomain.org/asset/tdc02_i nt_bodycontrol/