Chapter Six

• Homeostasis


  The maintenance of a relatively stable internal environment in the body despite changes in the external environment
• Stimulus-response model


  A model that describes how a system responds to a stimulus
• Positive feedback system


  A stimulus–response process in which the response increases the stimulus
• Negative feedback system


  A stimulus–response process in which the response counters the stimulus
• Stimulus


  An event or molecule that can initiate a response
• Receptor


  A structure that detects a signal or external change, usually a protein
• Modulator


  Location where information from receptors is sent to and compared to a set point, and where molecules altering the functioning of an effector are released. Also known as the processing centre
• Effector


  A molecule, cell, or organ that responds to a signal and produces a response
• Hormone


  A signalling molecule released from endocrine glands that regulates the growth or activity of target cells
• Response


  The action of a cell, organ, or organism caused by a stimulus
• Transduction


  The series of events that occur after the reception of a signal which results in the generation of a response
• Conduction


  The transfer of heat through physical contact with another object
• Convection


  The transfer of heat via the movement of a liquid or gas between areas of different temperature
• Evaporation


  The loss of heat via the conversion of water from liquid to gas
• Radiation


  The transfer of heat via electromagnetic waves
• Metabolism


  The set of chemical reactions within cells that help maintain the body’s normal functioning including converting food and drink to energy
• Thermoregulation


  The homeostatic process of maintaining a constant internal body temperature
• Endotherm


  An animal that produces the majority of its own heat via metabolic processes
• Ectotherm


  An animal that obtains heat primarily from the environment, rather than its own metabolic heat
• Hypothalamus


  A section of the brain in mammals that controls the maintenance of the body’s internal environment
• Vasodilation


  The widening of blood vessels
• Cerebral cortex


  The outer layer of the brain that plays a key role in a number of processes including memory, attention, and perception
• Arrector pili muscles


  Small muscles attached to hair follicles
• Skeletal muscle


  A type of muscle that is voluntarily controlled and that is usually attached to bones
• Vasoconstriction


  The narrowing of blood vessels
• Brown fat


  A type of body fat that is activated when the human body experiences low temperatures
• Glucose


  A six-carbon carbohydrate that comes from the food we eat
• Carbohydrate


  A class of biomacromolecules made from monosaccharide monomers consisting of carbon, hydrogen, and oxygen. Also known as saccharides or sugars
• Glucose transporter

  A group of membrane proteins that transport glucose across the plasma membrane
• Glycogen

  A polysaccharide of glucose that stores energy. Serves as the main storage of glucose in the body
• Glycogenesis


  Creating glycogen from glucose
• Glycogenolysis


  Breaking down glycogen into glucose
• Blood plasma

  The liquid component of blood that supports blood cells
• Blood glucose level

  A measure of the amount of glucose present in the blood. Normal homeostatic mechanisms keep blood glucose levels between 4.0 – 7.8 mmol/L
• Hyperglycaemia


  The state of having blood glucose levels above the normal range (>7.8 mmol/L)
• Hypoglycaemia


  The state of having blood glucose levels below the normal range (<4.0 mmol/L)
• Pancreas


  An organ of the digestive and endocrine system that releases both digestive juices and hormones
• Islets of Langerhans


  Regions of the pancreas that contain cells that secrete hormones
• Alpha cells


  Cells that occupy the islets of Langerhans and secrete glucagon
• Beta cells

  Cells that occupy the islets of Langerhans and secrete insulin