Download Vertebrate Form and Function Homeostasis: The Foundation of

11/7/12
Dr Áine Kelly
Dept of Physiology, School of Medicine
Email: [email protected]
http://medicine.tcd.ie/physiology/student/
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
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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 O2 and CO2
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
PO2 :160mmHg
PaO2: 100mmHg
Record temperature: -12 to 30oC.
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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
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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
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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
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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
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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
Extrinsic controls
Local controls that are
inherent in an organ
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.
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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
Control of body temperature
Sherwood 1-7
Other examples
Clotting
Propagation of action potential
in a neuron
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
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Physiology Research Focus: Disease
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