Cell Biology 1 - Homeostasis PDF

Dr. Simon Wells [email protected] Ms. Manvi Gandhi [email protected] Adapted from a lecture produced by Dr. Emma Parkinson-Lawrence at UniSA ▪ To understand the importance and provide a definition of homeostasis. ▪ Understand how the negative and positiv...

Dr. Simon Wells [email protected] Ms. Manvi Gandhi [email protected] Adapted from a lecture produced by Dr. Emma Parkinson-Lawrence at UniSA ▪ To understand the importance and provide a definition of homeostasis. ▪ Understand how the negative and positive feedback loops contribute to maintaining homeostasis. Readings Fundamentals of Anatomy & Physiology, Global Edition, 11th Edition Chapter 1 Section 1-7 and 1-8, pg 64-70; Chapter 3 Section 3-1 to 3-3 pg 112-131.  Physiologia (Latin): ‘natural science’ Living things have been around for a long time Ancient processes Function and processes of cells, tissues and organs https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQtb4LKU3YFA4G0AvCCeweeAj9lJU8DFipcoEnUs8TvNrexpgSe_Q Levels of Organisation Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings  You get too hot? You get too cold? Homeo = same Stasis = standing still ▪ all body systems working together to maintain a stable internal environment ▪ physiological response to changes INSIDE and OUTSIDE the body ▪ resistance to change - ensuring that our body functions within a normal range An organism is said to be at homeostasis when its internal environment: contains the optimum amount of chemicals has optimal temperature has optimal pressure for the survival of living cells We may become ill when homeostasis is disturbed Three components required for homeostasis ▪ Receptor: sensor that monitors the physiological environment and signals a change. ▪ Control Centre: processes the signal & sends instructions for a response to occur. Determines the level of change required. ▪ Effector: carries out instructions sent by the control centre. Negative Feedback Loop ▪ The response of the effector reduces or stops the stimulus ▪ Body is brought back into homeostasis ▪ Normal range is achieved Positive Feedback Loop ▪ The response of the effector increases change of the stimulus ▪ Body is moved away from homeostasis ▪ Normal range is lost ▪ For speeding up dangerous processes An example of negative feedback is the air-conditioning system What is the environmental condition being monitored? What is the ‘receptor’? What is the ‘control centre’? What is the ‘effector’? An example of negative feedback is the air-conditioning system What is the environmental condition being monitored? What is the ‘receptor’? What is the ‘control centre’? What is the ‘effector’? Thermoregulation Regulation of Blood Sugar Blood Glucose – too high Blood Glucose – too low  Insulin Blood Glucose – normal range  glucagon pancreas pancreas liver removes blood glucose liver breaks down glycogen excess glucose stored as glycogen glucose released into blood  Thermoregulation Blood glucose level Environmental Body temperature Blood glucose condition concentration Receptor Body’s temperature sensors Glucose receptors in the pancreas Control centre Brain/hypothalamus/ Pancreas thermoregulatory centre Effector(s) Blood vessels, sweat Insulin + glucagon glands, skeletal muscles For a summary watch the following video: https://www.youtube.com/watch?v=14SQT97EE4c Labour Extremely risky for mother and baby. Uses a positive feedback system to accelerate out of danger. Well defined endpoint – birth, limits the positive feedback. Break or tear of a blood vessel Dangerous as blood leaks uncontrollably. Positive feedback mechanism used to accelerate the process. Well defined endpoint – clotting, limits the positive feedback.  Labour Blood clotting Environmental Childbirth Blood loss condition Receptor Stretch receptors in the Damaged blood vessel cervix cells Control centre Brain No real control centre Effector(s) Oxytocin Clotting chemicals For a summary watch the following video: https://www.youtube.com/watch?v=5UN9hCBBJ0A How does the body maintain/regulate homeostasis? ▪ Intrinsic/autoregulation o Automatic response within a cell, tissue, or organ to some environmental change ▪ Extrinsic regulation o Responses controlled by the nervous and endocrine systems How does the body maintain/regulate homeostasis? ▪ Many functions vital for life are controlled by the autonomic nervous system osmosis.org Coordination by control centres in the brain stem: ▪ Medulla oblongata + Pons ▪ Sympathetic nervous system ≡ fight or flight ▪ Parasympathetic nervous system ≡ rest and digest Oppenlander (2021) Neurosurgical care of athletes ▪ Physiology is the branch of science concerned with the function of organisms ▪ Physiological systems integrate with each other to ensure our body works within the normal range ▪ Negative feedback involves stopping the stimulus to return homeostasis ▪ Positive feedback involves enhancing the stimulus temporarily, eventually returning to homeostasis Useful summary video: https://www.youtube.com/watch?v=Iz0Q9nTZCw4 ▪ Define homeostasis. Explain the parts of a general homeostatic feedback system. ▪ Define negative feedback. Describe a specific negative feedback process in humans. ▪ Define positive feedback. Describe a specific positive feedback process in humans. ▪ Describe the feedback mechanism involved in regulating body temperature/blood glucose level/childbirth/blood clotting.