Lecture 1.pdf

BPK 205 Introduction to Human Physiology Lecture 1 Overview of the Course; Homeostasis & Physiological Organization Dr. N. Wicks Fall 2024 1 Lecture Objectives Define the term “phy...

BPK 205 Introduction to Human Physiology Lecture 1 Overview of the Course; Homeostasis & Physiological Organization Dr. N. Wicks Fall 2024 1 Lecture Objectives Define the term “physiology” Define and give examples of homeostasis – Negative and positive feedback loops affect homeostasis – Feedforward control and homeostasis Describe the biological hierarchy of organization in the context of compartments – Functional compartments: Cells, tissues, organs – Fluid compartments: Intracellular vs Extracellular Describe the key properties of cellular membranes 2 Readings Chapter 1: Introduction to Physiology Chapter 2: Molecular interactions (review) Chapter 3: Compartmentalization: Cells and Tissues 3 What is Physiology? “Physiology is the study of living things and how they function. Physiology helps us understand how the body works, from the smallest part (cells) all the way to the whole body. It helps us understand how different parts of the body work together.” American Physiological Society http://www.the-aps.org/ 4 Where does physiology fit into the life sciences? PHYSIOLOGY ECOLOGY CELL MOLECULAR BIOLOGY CHEMISTRY BIOLOGY Organ Populations of Ecosystem of Atoms Molecules Cells Tissues Organs Organisms Biosphere systems one species different species Fig 1.1 5 The Goal of Physiological Systems: HOMEOSTASIS Homeostasis = Constancy The maintenance of a relatively stable internal environment We have a “set point” that dictates the level of certain variables. The goal is to maintain these variables within a tight range based on the set point Body must maintain mass balance (deviation from – i.e. if the amount of a substance in the body set point) is to remain constant, then: input + production = output + consumption; see Fig. 1.6 Examples: – Temperature – Blood pressure – Blood glucose level – pH 6 Fig. 1.4 Homeostasis ≠ Equilibrium Fig. 1.7 Consider homeostasis as maintenance of a dynamic steady-state 7 Maintaining Homeostasis: Negative Feedback loops Signal to Signal to effector to integrating center initiate change Integrating Center Stimulus Sensor Effector Output Output level changes and “feeds back” to sensor 8  Negative Feedback loop e.g. Regulation of Body Temperature Signal to Signal to effector to integrating center initiate change Nerve Signal Nerve signal about  Integrating Center temperature Hypothalamus Stimulus Stimulus: Temperature Sensor Effector Nerve endings Skeletal Muscles Output Blood vessels Output level changes and “feeds back” to sensor 9 Negative vs. Positive Feedback Loops In a negative feedback system, the feedback reduces the difference between the desired setpoint and the actual value; i.e. it works to reduce the initial stimulus and regain homeostasis. In a positive feedback system, the feedback increases the difference between the normal setpoint and the actual value; i.e. it enhances the stimulus and moves the system away from homeostasis 10 Positive Feedback Loops: A deviation from homeostasis e.g. Labour and childbirth Stimulus Baby Drops, presses on cervix Sensor Stretch Receptors in Cervix Integrating Center Brain  Oxytocin release Effector Smooth muscles of the uterus Response Increased contractions 11 Fig. 1.13 Feedforward Control Initiation of a response in anticipation of the stimulus – E.g. Sight, smell or thought of food is enough to initiate salivation and digestion – E.g. Increase in ventilation (breathing) as soon as exercise begins 12  Biological Hierarchy of Organization Compartmentalization allows for separation of complex processes 13 Organ Systems A collection of parts that work together in a predictable way to achieve a common function. Fig.141.2 Compartments of the Body Organs Tissues Cells Compartments Are Separated by Membranes Pericardial Tissue membranes Phospholipid bilayers membrane have many cells. create cell membranes. Cell Heart Loose connective tissue The pericardial sac is Seen magnified, the pericardial Each cell of the The cell membrane a tissue that surrounds membrane is a layer of pericardial membrane is a phospholipid the heart. flattened cells supported by has a cell membrane bilayer. connective tissue. surrounding it. Fig 3.1 Lumen: The interior of hollow organs Cytoplasm: The interior of cells 15 Body Fluid Compartments 16 Fig. 5.1a Body Fluid Distribution Volumes for standard 70 kg male (60% water) Water content varies with age and sex (Table 5.1) 3L 11 L 28 L Plasma Interstitial Intracellular fluid fluid ECF ICF ECF = Extracellular Fluid 1/3 2/3 ICF = Intracellular Fluid Cell membrane See fig 5.1 17 The Cell: Review Cell membrane = plasma membrane Provides structural support The Cell Physical barrier between ICF/ECF Selectively permeable Regulates exchange Regulates communication Cytosol = intracellular fluid Cytoplasm = intracellular fluid + organelles, inclusions, proteins Free pass: can pass by diffusion (O2 and CO2) Fig 3.4 REVIEW: Ch 2 – Basic Chemistry & Protein interactions Ch 3 – Cell membranes & Intracellular compartments of the cell, pp 65-72 (Fig. 3.4) 18 The Cell Membrane: Review Mostly phospholipid Fig 3.2 bilayer Also contains: Polar hydrophilic ▫ Proteins Span whole bilayer Channels ‘ Transmembrane Carriers Non-polar hydrophobic ‘ Peripheral (non-covalent attachment) ‘ Lipid-anchored (covalent bond) ▫ Carbohydrates ▫ Glycoproteins & Glycolipids ▫ Cholesterol ▫ Affects membrane fluidity and permeability 19 Lecture Review Questions Chapter 1, Level 1 Questions 1-5, 7-8 Chapter 1, Level 2 Questions 12-13 Chapter 3, Level 1 Questions 1-3, 10-12 Chapter 3 Level 2 Questions 16, 19, 21 *Review questions are recommended to reinforce key concepts and most often do not represent exam-style questions. Practice questions are given in tutorials and provided prior to exams. 20