Chapter 1 Homeostasis • Recall the concept and components of homeostatic systems, describing how cells, tissues, organs and organ systems maintain important physiological set points. This will be measured by quiz and exam scores.
Dec 27, 2015
Chapter 1Homeostasis
• Recall the concept and components of homeostatic systems, describing how cells, tissues, organs and organ systems maintain important physiological set points. This will be measured by quiz and exam scores.
Outline
• Physiology• Levels of organization• Basic Cell function• Tissues• Body systems• Homeostasis
Physiology• Study of body functions
• Two processes explain body functions– Teleological
• Explanations are in terms of meeting a bodily need
– Mechanistic• Explanations are in terms of cause and effect
sequences– Body is viewed as a machine
Physiology is the study of body functions
•Physiologists explain body function in terms of cause-and-effect sequences
Two approaches are used to explain events that occur in the body: – The purpose of a body process – The underlying mechanism
•Anatomy is the study of structure
•Physiology and anatomy are interrelated because functions depend on structure
Structure-Function relationships of the body Examples:•Heart receiving and pumping blood•Teeth tearing and grinding food
Basic Cell Functions• Obtain nutrients and oxygen from surrounding environment• Perform chemical reactions that provide energy for the cell• Eliminate carbon dioxide and other wastes to surrounding
environment• Synthesize needed cellular components• Control exchange of materials between cell and its
surrounding environment• Sensing and responding to changes in surrounding
environment• Reproduction
– Exception• Nerve cells and muscle cells lose their ability to
reproduce during their early development
Tissues• Groups of cells with similar structure and
specialized function
• Four primary types of tissues– Muscle tissue
– Nervous tissue
– Epithelial tissue
– Connective tissue
Tissues• Muscle tissue
– Specialized for contracting and generating force
– Three types of muscle tissue• Skeletal muscle
– Moves the skeleton
• Cardiac muscle– Pumps blood out of the heart
• Smooth muscle– Encloses and controls movement of contents through hollow
tubes and organs
• Connective tissue– Cells dispersed in a matrix
– Connects, supports, anchors tissue
Tissues• Nervous tissue
– Consists of cells specialized for initiating and transmitting electrical impulses
– Found in brain, spinal cord, and nerves
• Epithelial tissue– Consists of cells specialized for exchanging
materials between the cell and its environment
– Organized into two general types of structures• Epithelial sheets
• Secretory glands
Microscopic technique series - Cheek cells. Phase view. LM X75.
Credit: © David Phillips/Visuals Unlimited 308777
Stratified squamous epithelium from mouth mucosa. H&E stain. LM X100.
Credit: © G.W. Willis, MD/Visuals Unlimited
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Human pseudostratified columnar epithelium lining the bronchus of the lung. H&E stain. X180.
Credit: © G.W. Willis, MD/Visuals Unlimited
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Human unilocular (white) fat and adipose (adult fat). H&E stain. LM X100.
Credit: © G.W. Willis, MD/Visuals Unlimited
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Bone section showing osteocytes in lacunae arranged in concentric circles surrounding Haversian canals. LM X75.
Credit: © Carolina Biological/Visuals Unlimited
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Organs• Consist of two or more types of primary
tissues that function together to perform a particular function or functions
• Example– Stomach
• Inside of stomach lined with epithelial tissue
• Wall of stomach contains smooth muscle
• Nervous tissue in stomach controls muscle contraction and gland secretion
• Connective tissue binds all the above tissues together
Levels of Organization-Organs
• Organs are combinations of two or more types of tissues that function together
An example is the stomach: – Lined with epithelial tissue
– Wall contains smooth muscle and nervous tissues
– Connective tissue binds various 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
Body Systems
• Circulatory System• Digestive System• Respiratory System• Urinary System• Skeletal System• Muscular System
• Integumentary System
• Immune System• Nervous System• Endocrine System• Reproductive System
Information from the external environment relayed through thenervous system
O2
CO2
Urine containingwastes and excess water and electrolytes
Nutrients, water,electrolytes
Feces containingundigested foodresidue
Sperm leave maleSperm enter female
EXTERNALENVIRONMENT
BODY SYSTEMS
RESPIRATORY SYSTEM
NERVOUS SYSTEM
URINARY SYSTEM
DIGESTIVE SYSTEM
REPRODUCTIVE SYSTEM
Exchanges with all other systems
CIRCULATORY SYSTEM
Exchanges with all other systems
MUSCULAR AND SKELETAL
SYSTEM
IMMUNE SYSTEM
INTEGUMENTARY SYSTEM
ENDOCRINE SYSTEM
Body systemsmaintainhomeostasis
Keeps internalfluids in
Keeps foreignmaterials out
HOMEOSTASIS
Homeostasisessential forcell survival
CELLS
Cells makeup bodysystem
Enables thebody to interactwith the externalenvironment
Protects againstforeign invaders
Regulate
What contribution does each system make to whole body homeostasis?
Homeostasis vs. Allostasis
• Homeostasis– ideal set point through local regulatory mechanism
• Claude Bernard 1865 and Walter Cannon 1926
– ex. Kidneys figure this out and decrease fluid output
• Allostasis:– The brain coordinating body-wide changes often including
changes in behavior.
– “remaining stable by being variable” – Sterling and Eyer 1988.
Sterling, P.; Eyer, J. (1988). "Allostasis: A new paradigm to explain arousal pathology". In Fisher, S.; Reason, J. T. Handbook of life stress, cognition, and health. Chicester, NY: Wiley.
Concept of Homeostasis
• Homeostasis defined as maintenance of a relatively stable internal environment
– Does not mean that composition, temperature, and other characteristics are absolutely unchanging
• Homeostasis is essential for the survival of each cell
• Each cell helps maintain the internal
• environment shared by all cells
• Factors maintained homeostatically:– concentration of nutrients
– concentration of O2 and CO2
– concentration of waste products
– pH
– concentrations of water, salt, and other electrolytes
– volume and pressure
– temperature
Fluid Compartments
• The fluid inside the cell is intracellular fluid (ICF)
• The fluid outside the cells is extracellular fluid (ECF)– ECF is the body’s internal
environment
• Consists of the plasma and interstitial fluid Most body cells are not in direct contact with the external environment
• Cell survival depends on maintaining a relatively stable internal fluid environment
Homeostatic Control Systems
• In order to maintain homeostasis, control system must be able to– Detect deviations from normal in the internal
environment that need to be held within narrow limits
– Integrate this information with other relevant information
– Make appropriate adjustments in order to restore factor to its desired value
Homeostatic Control Systems
• Control systems are grouped into two classes– Intrinsic controls
• Local controls that are inherent in an organ
– Extrinsic controls• Regulatory mechanisms initiated outside an organ
• Accomplished by nervous and endocrine systems
Homeostatic Control Systems
• Feedforward – Term used for responses made in anticipation of
a change
• Feedback – Refers to responses made after change has been
detected
– Types of feedback systems• Negative
• Positive
Homeostatic Control Systems
• Negative feedback system– Primary type of homeostatic control
– Opposes initial change
– Components• Sensor
– Monitors magnitude of a controlled variable
• Control center– Compares sensor’s input with a set point
• Effector – Makes a response to produce a desired effect
Homeostatic Control Systems
• Positive feedback system– Amplifies an initial change– Do not occur as often as negative feedback system– Example
• Uterine contractions become increasingly stronger until the birth of the baby
• Pathophysiology refers to abnormal functioning of the body
associated with diseaseWhen a homeostatic disruption becomes so severe
that it is no longer compatible with survival, death results