Principles of Animal Physiology - DPHU · Principles of Animal Physiology Homeostasis Cells can live and function only when they are bathed by ECF that is compatible with their survival

Principles of Animal PhysiologyIntroduction

▪What is LIFE?

▸LIFE♦ “Things” organized to use energy and raw materials from their environment, maintain their integrity and reproduce.


▪What is PHYSIOLOGY?

▸PHYSIOLOGY is FUNCTION!!!

▸PHYSIOLOGY is an INTEGRATIVE science♦ Uses Anatomy, Physics, Chemistry . . .

▸ SUBDISCIPLINES of Animal Physiology♦ Comparative; Environmental; Evolutionary; Development; Cell ...


▪ Why study Animal Physiology?▸ Curiosity - I just want to know.▸ Applications - I want to profit from what I know.▸ Insights - Now what do I do with what I know?

▪ Human Physiology share:-▸ The same fundamental biological processes.▸ A common set of laws of physics and chemistry.▸ The same principles and mechanisms of genetics.▸ A linked evolutionary history.

▪ August Krogh principle:▸ For a large number of physiological problems, there will be some animal on which it can be most conveniently studied.


▪ A physician and medical researcher who understands physiology - both its potential contributions and limitations -is better equipped to make intelligent and perceptive decisions about the body.


▪ Physiological processes arise through evolution▸Natural selection - process by which traits that enhance a species survival are able to produce more surviving members than others not having those characteristics♦ Mechanistic (proximate) explanation

– How does it work? Process by which events occur.– Traditional core of the physiological sciences

♦ Evolutionary explanation– How did it evolve to be the way it is?

♦ Teleological approach– Why does it work? Purpose for the event/system.– Sometimes assumes that features are always logically evolved


▪ The Hypotheticodeductive Method (Scientific Method)▸ Science is a way of thinking.▸ Science is a logical way to investigate the universe.♦ Observation

– And ask questions♦ Experimentation

♦ Hypothesis– testable and falsifiable

♦ Control

♦ Data– Analysis

♦ Replication

Principles of Animal PhysiologyUse of Animals in Research

▪ Animal Rights vs Animal Welfare▸ Animal Welfare - have changed drastically over the years▸ Physiologists accept certain moral responsibilities♦ Animals are used only for worthwhile experiments

♦ All necessary steps are taken to minimize pain and distress

♦ All possible alternatives to the use of animals are considered

▸ Institutional Animal Care and Use Committee▸ Animals rights - Animals have the same legal and moral rights as humans do

Principles of Animal PhysiologyLevels of Organization

▪ To understand how the body functions and coordinates its activities, we will first examine its components.▪ Organizational levels▪ Know and define these levels up to the organism


▪ Basic cell functions include:♦Self-organization: Using resources from the environment to create the cell

♦Self-regulation: Maintain self-integrity in the face of disturbances

♦Self-support and movement: Having structrures that give specific form to the cell and to move materials within the cell or to move the cell itself

♦Self-replication: Reproducing to carry on the species, and to repair damage


▪ Four primary tissue types:♦Muscular tissue - specialized for contraction and force generation

– Skeletal, cardiac and smooth

♦Nervous tissue - specialized for initiation and transmission of electrical impulses

♦Epithelial tissue - specialized in the exchange of materials

– Sheets and secretory glands

♦Connective tissue - have relatively few cells dispersed within an abundance of extracellualar material that they secrete

Principles of Animal PhysiologyHomeostasis

▪ Most cells are NOT in contact with the external environment▪ Most cells CANNOT function without other cells▪ Most cells are in contact with the internal environment▪ The internal environment consists of material outside the cell, but inside the body▪ Define ExtraCellular Fluid (ECF)▪ Define IntraCellular Fluid (ICF)▪ Define InterStitial Fluid (ISF)


▪ Components of the ExtraCellular Fluid (fig 1-5)


▪ Cells can live and function only when they are bathed by ECF that is compatible with their survival▪ The cell must obtain nutrients and discharge waste to the ECF▪ Claude Bernard (1813-1878)▸Le milieu interieur

▪ Walter B. Canon (1871-1945)▸Coined the term Homeostasis


▪ Homeostasis♦Maintenance of relatively stable conditions in the internal environment and in other body states


▪ Interdependent relationship of cells, body systems and homeostasis (Fig 1-6)


▪ Factors affecting Homeostasis♦Amount of energy-rich molecule - fuel

♦O2 & CO2 concentration - for chemical reactions

♦Waste products - toxcicity

♦pH - acid/base balance, enzymatic activity

♦Water, salt & electrocytes - cell size

♦Volume & pressure

♦Temperature - narrow range

♦Social parameters - social insects (termites)


▪ Feedback-Control Systems♦Conformers - animal’s internal changes parallel the external conditions

– e.g. starfish - salinity; annelid worms O2

♦Regulators - animal defend a relatively constant state

♦Avoiders - minimize internal variations by avoiding environmental disturbances

– Some fish avoid temperature changes by changing location

♦Enantiostasis (allostasis) - change in one physiological variable to conteract a change in another

– Blue crabs - change blood pH to increase O2 binding when in brachish water


▪ Comparisons of negative feedback control systems (Fig 1-8)

a -components of a basic feedback system b - control of room

temperature

c - control of mammalian body temperature


▪ Feedback effectors♦Antagonistic control: Opposes change in the variable

– Temperature falls -> effectors produce change to increase temperature (thermostatic effect)

♦Behaviors as effectors: Animal seeks out a different location (Avoiders)

– Migration of Monarch butterflies to avoid the cold north– Killifish seeks out water to keep its internal salinity about 35 to 45% that of normal seawater


▪ Enhancement & expansion of basic negative feedback systems (Fig 1-9)

Antagonistic effectors Feedforward control


▪ Flaws of Negative Feedback Systems▸ It must first suffer a disturbance before it can act▸Delayed response▸Overshoots the set point

▪ Flaws Overcome by:▸Feedforward system (Anticipation)♦ Predicts results of a disturbance

♦ Prevents overshooting of the set point– e.g. increased insuling secretion while meal is still in digestive tract

▸Acclimatization systems


▪ Adaptation, Acclimatization and Acclimation♦Adaptation - evolution by natural selection

♦Acclimatization - physiological, biochemical, or anatomical change within an individual from chronic exposure to a new environment

♦Acclimation - same as above, but induced experimentally


▪ Other Controlled Systems▸Rheostasis - non-homeostatic regulation♦ Reset system - changes the setpoint temporarily, permamently or cyclically

– Fever– Sex hormone concentrations - at puberty– Reproductive cycle - menstrual cycle

♦ Positive feedback system– Creates rapid change– Reinforces the change in the same direction– e.g. neuron action potentials, lactation, blood clotting, orgasms . . .


▪ Mechanisms for regulated change


▪ Mechanisms for regulated change, cont’d


▪ Ten Physiological Organ Systems♦Circulatory: transports gases, nutrients & wastes

♦Digestive: obtains nutrients, water & electrolytes

♦Endocrine: regulates processes for duration

♦Immune: defends against foreign invaders

♦Integumentary: proctective barrier

♦Musculoskeletal: support, protect & movement

♦Nervous: controls rapid response of body

♦Reproduction: perpetuation of the species

♦Respiratory: O2 and CO2, regulates pH

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Principles of Animal Physiology - DPHU · Principles of Animal Physiology Homeostasis Cells can live and function only when they are bathed by ECF that is compatible with their survival