Class 1: Introduction to Human Physiology PDF

1/17 Class 1: Introduction to Human Physiology PHSL 3051: Human Physiology Hannah Thompson, M.S. January 17th, 2024 Department of Integrative Biology and Physiology Email: [email protected] Office: 6-125 Jackson Hall /2023 How to be successful in the Cell and Neuro Section (and the rest of class!) 1....

1/17 Class 1: Introduction to Human Physiology PHSL 3051: Human Physiology Hannah Thompson, M.S. January 17th, 2024 Department of Integrative Biology and Physiology Email: [email protected] Office: 6-125 Jackson Hall /2023 How to be successful in the Cell and Neuro Section (and the rest of class!) 1.Use the learning objectives in your studying 2.Watch the pre-lab videos before lab/class 3.Come to class ready to engage 4.Use the weekly study guides 5.Do NOT hesitate to ask questions!!! Class 1: Introduction to Human Physiology Learning Objectives 1. Diagram the body plan, showing the various organ systems and their interrelationships with one another and with the external environment (Chapter 1.4, Fig 1.4) 2. Describe the main components of a feedback system (Chapter 1.4, Fig 1.4) 3. Compare and contrast negative and positive feedback and feedforward systems and give an example of each in the human body. What are these types of systems designed to do? 4. Define what set point is and how this relates to homeostasis. Let’s Start with an Exercise Turn to your neighbor and tell them… 1. How would you define physiology? (without using your notes) 2. What is one thing you are excited about/hope to learn in this class? 3. What is something you are nervous about in this class? Let’s regroup in a few minutes! Human Physiology is the study of how the human body and its parts work Organ System Atom Nerve Cell (Neuron) Nervous (Neural) Tissue Brain Tissue Organ O H H O C O G Cell Molecule We’ll start here Organism Physiology is the study of how a living organism and its parts function Organ System Atom Nerve Cell (Neuron) Nervous (Neural) Tissue Brain Tissue Organ O H H O C O G Cell Molecule Organism Cells are the Smallest Unit of Life Cells are the smallest unit that can demonstrate the characteristics of life. Cells can…. Move Use energy Reproduce Remove wastes React Grow Evolve, etc. We Can Divide Our Body’s Fluids into Three Parts Intracellular Fluid (ICF) The fluid found within cells Interstitial Fluid Cells Intracellular Fluid Blood Vessel Plasma Extracellular Fluid (ECF) 1. Interstitial Fluid The fluid found between cells 2. Plasma The fluid portion of the blood The make up (composition) of the ECF is very important to cell health and survival. Therefore, the ECF is considered our body’s internal environment The Body is In Contact with the External Environment The fluids in the lungs, gut and urinary system are part of the external environment To maintain our body’s internal (cellular) environment, the internal and external environments must interact. Nutrients and wastes move between the external environment and internal environment by crossing a cell layer Moving Between the Internal and External Environments Example: Gas Exchange Homeostasis is the Maintenance of our Internal Environment Let’s say you have eaten a chocolate bar… After you eat the chocolate bar, the GI tract will digest the contents of your chocolate bar into glucose The small intestine is then responsible for the absorption of glucose into the plasma This increases the amount of glucose in the plasma But too much glucose in the plasma can be harmful… Our body therefore tightly regulates the amount of glucose within our plasma. How? Stimulus Sensor (Receptor) The Body Maintains Homeostasis through Feedback Loops In the previous slide, eating a chocolate bar caused our extracellular glucose levels (controlled variable) to fall out of its set point. (Stimulus) Input Signal Control (Integrating Center) Output Signal Control box Target (Effectors) Response The controlled variable is the variable that we are regulating. Feedback The set point is a range of a controlled variable that is considered stable/optimally healthy. In our chocolate bar situation, our set point is the range of glucose levels in the extracellular fluid considered stable/optimally healthy. Our body maintains glucose homeostasis through a feedback loop! 1 Plasma glucose increases. 2 A sensor detects the increase in glucose Stimulus Sensor (Receptor) The Glucose Feedback Loop (Example) Situation: You just finished eating a chocolate bar. 3 The sensor sends an input signal to the… Input Signal Control (Integrating Center) 4/5 …Pancreatic β-Cell. The beta cell integrates the information from the input Output Signal signal and now sends Control an output signal: insulinbox 6 Target Insulin then goes to its (Effectors) targets: skeletal muscle, fat and the liver 7 Response Plasma glucose decreases Negative Feedback 8 The decrease in plasma glucose opposes the stimulus. This causes the feedback loop to be “turned off” now that plasma glucose levels have returned to its set point. Negative Feedback Opposes the Initial Stimulus Initial stimulus Response loop shuts off Response Stimulus Plasma glucose increases Pancreatic β-Cells release insulin which causes skeletal muscle, fat and the liver to take glucose and either use glucose to make energy or store the glucose for later. Extracellular glucose decreases Negative feedback loops are very common in human physiology. There are many variables controlled by negative feedback: blood pressure, blood volume, etc. 1 Labor causes the fetus’ head to stretch the cervix Stimulus 2 Stretch detectors detect the degree of stretch in the cervix 3 Sensor (Receptor) The sensor sends an input signal to the… Input Signal 4/5 Control (Integrating Center) …brain. The brain integrates the input signal and now sends an output signal: oxytocin Control Output Signal box 6 Oyxtocin now goes to its target: muscles within the uterine wall. 7 Target (Effectors) The uterine wall contracts Response Parturition (Childbirth) is an Example of a Positive Feedback Loop Positive Feedback Situation: After 9 months of gestation (pregnancy), a patient starts labor 8 As the uterine wall contracts, the fetus’ head causes the cervix to stretch even further. The feedback loop will not stop until the fetus is fully delivered and there is no longer any stretch to the cervix. Positive Feedback Reinforces the Initial Stimulus Initial stimulus The cervix stretches The uterus contracts, pushing the fetus further down the vaginal canal Response + Feedback cycle Stimulus An outside factor is required to shut off + feedback cycle. The brain will keep on releasing oxytocin, causing contraction of the uterus until the fetus is fully delivered. The cervix is stretched even more Positive feedback loops are very rare in human physiology. We will see more of positive feedback loops primarily during the female reproduction units with Dr. O! Let’s Practice! Which of the following is NOT an example of a negative feedback system: A. While fasting, your liver releases glucose it has stored. B. Low oxygen from hiking in altitude results in increased respiration rate C. Cold temperatures outside induce shivering of skeletal muscles to generate heat within the body D. Platelets in the blood release clotting factors which causes more platelets to coagulate Feedforward Mechanisms After class, you have plans to eat lunch. It’s the last 5 minutes of class and you are getting hungry… You notice that you begin to salivate. Your body also sends signals to the stomach to increase the production of stomach acid. This is an example of a feedforward mechanism. Your body is preparing for when you eat food before you even begin eating! Unlike feedback responses, feedforward mechanisms occurs when your body is anticipating a change. What you should have learned… What the three body fluid compartments are What the “internal” and “external” environments are How the external and internal environments exchange various molecules The parts of a feedback loop Understand what set point is and how it relates to homeostasis The difference between a positive feedback loop, negative feedback loop and feedforward mechanism.