Anatomy Concept 2 Homeostasis and Regulation

VOCABULARY • Homeostasis = - Stability of the internal environment and the mechanisms that maintain that stability • Receptor = - Sensory organ that receives the stimulus • Stimulus = - An action that evokes a response • Effector = - An organ that does the response • Response = - The effect, caused by the stimulus • Feedback inhibition = - When the output of a process is used as an input to control the behavior of the overall process itself, usually leading to inhibition of the process VOCABULARY • Passive transport = - The movement of molecules across the cell membrane that doesn’t require extra energy, moving down the concentration gradient • Active transport = - The movement of molecules across the cell membrane that does require extra energy, moving against the concentration gradient • Hypertonic solution = - A solution with a water concentration lower than the cell’s cytoplasm • Hypotonic solution = - A solution with a water concentration higher than the cell’s cytoplasm • Isotonic solution = - A solution with a water concentration identical to the cell’s cytoplasm • Ligand = - Molecules that bind to other molecules (receptor proteins) for signaling purposes VOCABULARY • Signal transduction pathway = - A sequence of events initiated by a signal that leads to a cellular response • Inhibitor = - Any molecule that blocks the normal ligand from binding, thus preventing communication along the signal transduction pathway • Transduction = - The passing along of the signal until the desired response is reached • Phosphorylation = - Addition of a phosphate group by kinases that changes a molecule’s shape and contributes to transduction • Dephosphorylation = - Removal of a phosphate group by phosphatases that changes a molecules shape and contributes to transduction • Second messenger = - A small molecule that serves as an intermediate between the receptor and the cascade of responses after OBJECTIVES 1. Differentiate between dynamic and static equilibrium. • A static equilibrium would be constant and unchanging. • A dynamic equilibrium fluctuates above and below the constant state, but the overall rate of “loss” balances out with the overall rate of “gain”. 2. Describe the relationship between response to stimuli and homeostasis. • Our bodies are designed to take in different stimuli via receptors, communicate the messages of those stimuli, and then initiate a response. This is how our bodies maintain constant internal stability, also known as homeostasis. OBJECTIVES 3. Differentiate between positive and negative feedback loops. Include an example of each. • Positive feedback loop – the output of a system intensifies the response, leading to amplification - Ex. Hormones released in human child birth • Negative feedback loop – the output of a system causes a counter response to return to a set point, leading to stabilization - Ex. Thermoregulation OBJECTIVES 4. Draw an example of a feedback loop, clearly labeling all parts. OBJECTIVES 5. Summarize the role of enzymes in the regulation of homeostasis. • Enzymes speed up biochemical reactions by the lowering the activation energy needed to get the reaction going. All biological processes are highly regulated and controlled by the presence (or absence) of specific enzymes. 6. Summarize the role of cellular transport in the regulation of homeostasis. • Cells maintain homeostasis with highly regulated transport mechanisms. The selective permeability of the cell membrane allows the cell to control what moves in and out as it brings needed resources in, expels waste, and transports signals in and out of the cell to maintain constant and stable internal conditions. OBJECTIVES 7. Describe the six types of cellular transport, including an example of a substance transported for each. • Simple diffusion: net movement of molecules from high to low concentration; Ex. O2 and CO2 • Facilitated diffusion: uses a transport protein (channel or carrier) to aid in the movement of molecules from high to low concentration; Ex. Polar molecules like Ca+2 and large molecules like glucose • Osmosis: diffusion of water from high to low concentration; Ex. Water • Molecular pumps: use energy to pump molecules through a protein channel against the concentration gradient; Ex. Na+/K+ Pump • Endocytosis: uses energy and vesicles to move particles into the cell; Ex. White blood cells engulf bacteria for destruction • Exocytosis: uses energy and vesicles to move particles out of the cell; Ex. Neurons secrete neurotransmitters for signaling OBJECTIVES 8. Explain the importance of cell signaling and communication in maintaining homeostasis. Include a brief description of a real-world example of a breakdown in cell communication and how that impacted homeostasis in the organism. • Cell signaling and communication is critical for maintaining homeostasis in humans because we are made of trillions of cells. • It allows cells in the body to process information from the environment and communicate to other cells in order to coordinate a response that maintains homeostasis. • Example: - Caffeine acts as an inhibitor by binding to receptors on nerve cells in our brains to block and not activate the receptors that tell our body we are tired, so that instead we remain feeling alert. OBJECTIVES 9. Draw a sketch of a signal transduction pathway, labeling the key parts. OBJECTIVES 10. Distinguish between the types of chemical signals that can initiate a signal transduction pathway. • Autocrine: ”self”; affect the same cell that releases them • Paracrine: diffuse to nearby cells • Juxtacrine: require direct contact between the signaling cell and the receiving cell • Hormones: chemical signal that travels to distant cells 11. Explain the importance of specificity in receptor proteins. Include the difference between intracellular and membrane receptors and the types of ligands they would bind to. • Only certain ligands can bind certain receptors. This specificity allows for highly regulated signaling pathways. - Intracellular receptors: inside the cell, thus bind small and/or nonpolar molecules that can easily diffuse through cell membrane - Membrane receptors: on surface of the cell, thus bind large and/or polar molecules that cannot easily diffuse through cell membrane OBJECTIVES 12. Describe the importance of a second messenger in certain signal transduction pathways. • A second messenger is a small molecule that serves as an intermediate between the receptor and the cascade of responses after • Plays a critical role in regulation as it can either distribute and/or amplify an initial signal received by a receptor 13. Explain several types of responses that can be triggered by a transduction pathway. • One signal can cause several responses, like: - Opening ion channels by changing the balance of concentration in and out of the cell - Altering gene expression by upregulating and downregulating them - Altering an enzyme’s activity to either happen (and thus make a reaction happen) or not (and thus prevent a reaction from happening) OBJECTIVES 14. Be able to analyze data to determine the effect of a feedback mechanism on homeostasis. 15. Be able to process information about a real-world feedback mechanism and translate it into a feedback loop diagram. 16. Classify a type of cellular transport based on a diagram or description. 17. Classify solutions as hypertonic, hypotonic, or isotonic based on a diagram or description. 18. Be able to interpret a diagram of a signaling mechanism and infer what type of response is being triggered.