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Chapter 1 - Introduction to Physiology

by: Melissa Notetaker

Chapter 1 - Introduction to Physiology BIO 327

Marketplace > Stephen F Austin State University > Biology > BIO 327 > Chapter 1 Introduction to Physiology
Melissa Notetaker


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The introductory material to physiology. Includes homeostasis and positive/negative feedback mechanisms.
Human Physiology
Dr. Langford
Class Notes
Biology, Physiology
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This 4 page Class Notes was uploaded by Melissa Notetaker on Tuesday July 19, 2016. The Class Notes belongs to BIO 327 at Stephen F Austin State University taught by Dr. Langford in Summer 2016. Since its upload, it has received 17 views. For similar materials see Human Physiology in Biology at Stephen F Austin State University.


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Date Created: 07/19/16
Introduction to Physiology -Chapter 1 Lecture Physiology – the study of the mechanical, physical, and biochemical functions of living organisms Two Critical Control Centers: 1. Endocrine glands (indirect) a. Reproduction b. Metabolism c. Plasma/lymph composition d. Urine output e. Digestion 2. Nervous system (direct) a. Psychoneuroimmunology (PNI) i. The study of the interaction between psychological processes and the nervous and immune systems Regulatory Mechanisms: 1. Intrinsic – “built in” to the organs they regulate 2. Extrinsic – regulated from a distance a. Ex. endocrine and/or neuronal Homeostasis – the property of a living organism that regulates its internal environment by using sensory input and effectors so as to maintain a state of dynamic constancy - Claude Bernard o Father of physiology o Published in 1865 Health – the optimal state of physical, mental, and social wellbeing of an individual and not merely the absence of disease or infirmary Major Components of the Homeostatic Unit 1. Sensors – receptors collecting information about the external and internal environment 2. Integrating centers – brain and spinal cord 3. Effectors – muscles/glands - Constantly active - Insure that the specific conditions are maintained within a certain acceptable range above and below a set point (the target or ideal condition for a particular psychological setting Feedback Loops - Enhance or buffer changes that occur in a system - Negative feedback loops – dampen or buffer changes o Stabilizes the system o Most common - Positive feedback – enhance or amplify changes o Moves system away from equilibrium o More unstable I. Negative feedback feeds part of a system’s output into the system’s input a. Ex. increase in body temperature from being outside on a hot day i. Sensors – temperature sensors detect increasing temperature on the skin and core body temperature ii. Integrating center – brain determines that in response to increasing temperatures, the body should work to lower core body temperature 1. Above 105 C, brain cells start to die iii. Effectors – sweat glands produce sweat which cools the skin iv. Result – core body temperature lowers v. Sensors – detect decreased fluid volume and increasing Na+ concentration in the blood vi. Integrating center – hypothalamus receives information about Na+ levels and signals the posterior pituitary to release ADH (anti-diuretic hormone) vii. Effectors – ADH travels in the bloodstream to the kidney tubules where it causes them to retain more water viii. Result – increase in fluid volume of the blood b. Feedback works in an antagonistic way to give a greater degree of control to the condition i. Glucose levels are largely controlled by cells of the pancreas 1. B cells a. Respond to high blood glucose levels b. Secrete insulin i. Causes cells to increase their uptake of glucose and store the extra as glycogen (a polymer of glucose) 2. Alpha cells a. Respond to low blood glucose levels b. Secrete glucagon i. Causes cells to release their stores of glycogen as glucose into the blood stream II. Positive Feedback a. “cumulative causation” b. A feedback loop system in which the system responds to perturbation in the same direction as the perturbation c. Leads to unstable equilibrium d. Ex. oxytocin-contraction = baby birth Cellular Homeostasis I. Molecular Regulation (DNA and protein) a. Ex. protein production may be controlled at the level of the gene (DNA) or by the activation of the protein through processing by enzymes b. Negative feedback – high levels of a product will result in inactivation of gene transcription for the enzyme leading to the product II. Cell Division a. Cells possess the ability to recognize their own numbers b. Contact dependent inhibition of growth – when the density of cells reaches a point of contact between normal cells, mitosis slows and even stops c. Secreted chemical signals – various chemical and/or mechanical signals at the point of an injury stimulate the activation of mitosis in cells during wound healing d. Ex. the Axolotl (salamander) – very successful at regeneration e. Once cell numbers reach a point to produce a threshold level of the inhibitor, cell division would halt. If cell numbers were mechanically lowered (wounding), the level of inhibitor would fall below threshold and cell division would resume. f. Consequences of failed recognition: i. Failure to control cell replication most frequently is traced back to mutations at the molecular level ii. Cause Effect Mistake in DNA mutation Loss of number recognition no CDIG Cell division unabated cell replication Excessive cell numbers overcrowding Limited nutrient supply starvation Cellular functions fail death (necrosis) e. The typical manifestation of a DNA mutation is a tumor and possibly cancer f. Cancerous (malignant) tumors i. When cancer cells invade normal tissues and spread (metastasize) to distant sites, they are called malignant tumors ii. Hyper – more than/above iii. Dys – different iv. Plasia – form v. Dysplasia – cells change form g. Common Causes of Genetic Mutations i. Increased stress/perturbation of cells 1. i.e., acid reflux, cigarette smoke, etc. 2. increases cell turnover and cellular replication (more divisions, the greater chances of a mistake) ii. environmental agents that have an affinity for the nucleus 1. Benzypyrene (carcinogenic agent) in cigarette smoke iii. Ionizing radiation 1. X-rays, UV light iv. Viruses 1. Ex. Human Papillomavirus (HPV) 2. Gardasil – the only cervical cancer vaccine that helps protect against four types of HPV: two types that cause 70% of cervical cancer v. Hereditary predisposition 1. ~5-10% of breast cancer cases are thought to be hereditary, resulting directly from mutations inherited from a parent 2. Ex. BRCA 1 and BRCA 2 – the most common inherited mutations BRCA 1 (breast cancer 1, early onset) - A human gene that belongs to a class of genes called tumor suppressors, which maintain genomic integrity to prevent uncontrolled proliferation - Protein product is involved in DNA damage repair, ubiquitination, transcriptional regulation, etc. - Women with an inherited BRCA1/BRCA2 mutation have up to an 80% chance of developing breast cancer o Often at an earlier age


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