Vertebrate Form and Function

Transcription

1 11/7/12 Dr Áine Kelly Dept of Physiology, School of Medicine Diagrams: Sherwood, Human Physiology (7th Ed.) Textbooks: Fox, Human Physiology Sherwood, Human Physiology, from Cells to Systems Germann and Stanfield, Principles of Human Physiology Vertebrate Form and Function Form (structure): Anatomy Function: Physiology This lecture: Organisation of the body and Homeostasis Homeostasis: The Foundation of Physiology Defined as maintenance of a relatively stable internal environment Does not mean that composition, temperature, and other characteristics are absolutely unchanging Essential for survival and function of all cells Physiologists research cell and molecular biology, systems biology and whole-body integrative physiologyto understand the function of living things 1

2 Homeostasis: What is the internal environment? Extracellular fluid (ECF) Fluid environment in which the cells live Plasma; interstitial fluid Intracellular fluid (ICF) Fluid contained within all body cells Also termed cytosol Homeostasis: normal living Factors homeostatically regulated include: Concentration of nutrient molecules Concentration of O 2 and CO 2 Concentration of waste products ph Concentration of water, salt, and other electrolytes Volume and pressure Temperature Homeostasis: What is the external environment? Dublin Height above sea level:0m Atmospheric pressure:760mmhg PO 2 :160mmHg PaO 2 : 100mmHg Record temperature: -12 to 30 o C. 2

3 11/7/12 Homeostasis: What is the external environment? Everest: 29,029ft (8,848m) above sea level PaO2: 25mmHg Dallol, Ethiopia (now a ghost town) 1960 s: average annual temp: 34oC La Rinconada, Peru: 16,732ft (5,100m) Oykmayon, Russia. January 1926: -71.2oC Recorded annual temp difference of 100oC Homeostasis: What is the external environment? Extreme environments can be exploited for research purposes Drought Lack of water: 3-5 day survival Famine Lack of food: weeks/months survival, depending on fat stores Hypoxia/anoxia World free diving record:125m World breath holding record: 22.22min 3

4 11/7/12 Physiology Research Focus: Exercise & Sports Science Study of how the body responds to exercise acutely and chronically Understanding Physiology is vital to improving performance of elite athletes Exercise prescription is used as a clinical tool Functional Organization of the Body Hierarchical: integration of function is key to Physiology 4

5 Cells Exchange materials (eg. nutrients, oxygen, carbon dioxide, wastes) with surrounding environment Perform chemical reactions that provide energy for the cell Synthesize needed cellular components Sense and respond to changes in surrounding environment (receptors) Reproduce (divide) Cell physiology, biochemistry and molecular biology allows us to further assess function of subcellular organelles, proteins etc. Cells are structurally specialised for function Humans are very different from single-celled or simple multicellular organisms! Neuron Cardiac muscle cell Gamete 5

6 Physiology Research Focus: Stem Cells Undifferentiated cells that can give rise to specialised cells Can we use these cells to treat disease? Spinal cord injury, parkinson s disease, diabetes mellitis, cancer Engineer replacement body parts? Hip replacement, burns, bladder Embryonic stem cells: pluripotent (can give rise to many different cell types) Ethical considerations - embryos are destroyed during this process Adult stem cells. Tissue-specific Bone marrow, brain, muscle Tissues Groups of cells with similar structure and specialized function Four primary types Muscle tissue (excitable) Nervous tissue (excitable) Epithelial tissue (exchange) Connective tissue (connection and support): includes blood, bone Organs Consist of two or more types of primary tissues working together to perform particular function(s) eg. Stomach: Inside lined with epithelial tissue Wall contains smooth muscle Nervous tissue controls muscle contraction & gland secretion Connective tissue binds all the above tissues together Body Systems Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body Do not act in isolation from one another Human body has 11 systems 6

7 Homeostatic Control Systems In order to maintain homeostasis, control system must be able to Detect deviations from normal in the internal environment (receptors) Integrate this information with other relevant information (CNS) Make appropriate adjustments in order to restore factor to its desired value Intrinsic controls Local controls that are inherent in an organ Extrinsic controls Regulatory mechanisms initiated outside an organ Accomplished by nervous and endocrine systems (note special role of hypothalamus) Homeostatic Control Systems (1): Feedforward Term used for responses made in anticipation of a change eg. during digestion (before absorption occurs) presence of food causes insulin release - insulin promotes uptake of nutrients into cells after their absorption from gut into bloodstream. 7

8 Homeostatic Control Systems (2): Feedback Responses made after change has been detected Positive feedback: reinforces change Negative feedback: opposes change Integrator compares sensor s input with a set point Contraction of the uterus at birth Oxytocin > contraction of uterine smooth muscle > moves baby lower > pressure on cervix > oxytocin release Other examples Clotting Propagation of action potential in a neuron Sherwood 1-7 Control of body temperature Other examples: almost every other aspect of Physiology! Disruptions in Homeostasis: pathophysiology Abnormal functioning of the body associated with disease or injury Haemorrhage - blood loss Body compensates to maintain blood pressure and circulation. If wound is not closed, death will occur (circulatory shock) Cholera - caused by toxins of bacterium vibrio cholera Fluid loss through diarrhoea, disturbance of ph of body fluids If oral rehydration therapy is not administered, death will occur Physiology research focus: Alzheimer s Disease: irreversible, incurable, terminal brain disease Amyloidβ plaques outside cells and neurofibrillary tangles inside cells compromise cell function Cell death Memory loss 8

9 11/7/12 Physiology Research Focus: Disease 9