Biology 2331

Anatomy and Physiology I

"If you want something you've never had, then you've got to do something you've never done."

Learn and Understand

• A new language

• At this stage, science drives the discipline

• Human A&P is focused but draws upon knowledge of other disciplines

• Structural and functional hierarchy – the whole is the sum of its parts

• Systems of the organism attempt to maintain internal conditions that sustain life while allowing for temporary deviations

What is Biology?

• bios = “life”• -ology = “study of”

• Greek and Latin important languages in biology and science in general

• Etymology• Pronunciation key in glossary (G-1)• Roots, suffixes and prefixes on last pages of book

• How is science different from other disciplines?

What is Anatomy and Physiology?• A subset of the larger field of biology

• Anatomy: scientific discipline that investigates the body’s structure and relationships between its parts– Readily observable

• Physiology: scientific investigation of the processes or functions of living things– At times, not easily observed – based on tested hypotheses which

are subject to change when new information comes to light

• Anatomy and physiology are inseparable– Function always reflects structure– What a structure can do depends on its specific form

What is Anatomy and Physiology?

Like all biology, directly influenced by the fields of

• General chemistry

• General physics

• Biochemistry

• Other fields of biology

Topics of Anatomy

• Gross or macroscopic: structures examined without a microscope– Regional: studied area by area

– Systemic: studied system by system

– Surface: external form and relation to deeper structures

• Microscopic: structures seen with the microscope– Examples:

• Cytology: cells

• Histology: tissues

Topics of Physiology

• Reveals dynamic nature of living things

• Often focuses on cellular and molecular processes. Examples:

–Cell physiology: examines processes in cells

–Neurophysiology: examines nervous tissue biochemistry and physics

–Cardiovascular physiology: heart and blood vessel tissue biochemistry and physics

Subjects That Encompass Both Anatomy and Physiology

• Pathology: structural and functional changes caused by disease

• Exercise Physiology: changes in structure and function caused by exercise–Example: bone density and training

Figure 1.2 Levels of structural organization.

Figure 1.4a The body’s organ systems and their major functions.

Figure 1.4b The body’s organ systems and their major functions.

Interdependence of Body Cells

• Humans are multicellular– To function, must keep individual cells alive

– Most cells depend on organ systems to meet their survival needs

• All body functions spread among different organ systems

• Organ systems cooperate to maintain life

• Some redundancy will be observed

• Note also, symbiosis with microbes

Figure 1.2 Examples of interrelationships among body organ systems.

Digestive systemTakes in nutrients, breaks them

down, and eliminates unabsorbed

matter (feces)

Food O2 CO2

Respiratory system

Takes in oxygen and

eliminates carbon dioxide

Cardiovascular system

Via the blood, distributes oxygen

and nutrients to all body cells and

delivers wastes and carbon

dioxide to disposal organs

BloodCO2

O2

Heart

Nutrients

Interstitial fluid

Integumentary system

Protects the body as a whole from

the external environment

Nutrients and wastes pass

between blood and cells

via the interstitial fluid

Feces Urine

Urinary system

Eliminates

nitrogenous

wastes and

excess ions

Why Do Human Bodies Work the Way They Do?

Humans, like all living things on this planet:

• Are subject to universal laws of chemistry and physics

• Have evolved complex cellular chemistry in order to thrive within an environment – to function best within a complex environment maximizing survivability and reproduction– ‘optimized’ for a particular environment

• Have catalogued their complexities as traits present in the genetic material inherited from parents

• In the natural world, both evolution and environmental change occur very slowly…over tens of thousands of years

• What are the characteristics of the environment humans are ‘adapted’ to?

Homeostasis• Values of variables

fluctuate around the set point - establish a “normal range”

• Set point: the ideal normal value of a variable– essentially an average– But changeable for

temporary circumstances

• What is the set point for body temperature?

There are too many body variables to list here

Controlling Body Parameters: Feedback Systems

• Components– Receptor: monitors the value of some variable;

responds to change

– Control center: establishes the set point; evaluates change; coordinates appropriate response

– Effector: can change the value of the variable; changes feedback on the stimulus

• Stimulus: deviation from the set point; detected by the receptor

• Response: produced by the effector

• Two examples: negative and positive

Figure 1.4 Interactions among the elements of a homeostatic control system maintainstable internal conditions.

Output: Information sentalong efferent pathway toeffector.

Input: Informationsent along afferentpathway to controlcenter.

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Receptordetectschange.

2

Stimulusproduceschange invariable.

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Responseof effectorfeeds back toreduce theeffect ofstimulus andreturnsvariableto homeostatic level.

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ControlCenter

Afferent

pathway

Efferent

pathway

Receptor Effector

BALANCE

Negative Feedback

• Any deviation from the set point is made smaller (resisted)

• Response reduces or shuts off original stimulus– Variable changes in opposite direction of initial change

• Most feedback mechanisms in body are NF

• Examples– Regulation of body temperature

– Regulation of blood glucose by insulin

– Regulation of blood pressure

Figure 1.5 Body temperature is regulated by a negative feedback mechanism.Control Center(thermoregulatory

center in brain)

Afferentpathway

Efferentpathway

ReceptorsTemperature-sensitivecells in skin and brain)

EffectorsSweet glands

Sweat glands activated

ResponseEvaporation of sweatBody temperature falls;stimulus ends

Body temperaturerises

Stimulus: Heat

ResponseBody temperature rises;stimulus ends

EffectorsSkeletal muscles

EfferentpathwayShivering begins

BALANCE

Afferentpathway

Control Center(thermoregulatory

center in brain)

ReceptorsTemperature-sensitivecells in skin and brain

Stimulus: Cold

Body temperature

falls

Positive Feedback

• When a deviation occurs, the response is to make the deviation greater - response enhances or exaggerates original stimulus

• Not as common as negative feedback, purposefully leads away from homeostasis

• Usually controls infrequent events that do not require continuous adjustment

Positive FeedbackExamples of positive feedback:

• Labor and delivery• cervical pressure, oxytocin, and uterine contraction

• Blood pressure changes during hemorrhage• Peripheral blood pressure drops are not resisted in order to

maintain core blood pressure and heart-lung-brain connection

• If blood loss continues - heart’s ability to pump blood decreases

• Heart and brain starved, death

• Platelet plug formation • the response to platelet adhesion is more platelet adhesion• obviously must be carefully controlled

Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug.

Releasedchemicalsattract moreplatelets.

Positivefeedbackloop

Plateletsadhere to site andrelease chemicals.

Feedback cycle endswhen plug is formed.

Platelet plugis fully formed.

Break or tearoccurs in bloodvessel wall.

Positive feedback cycle is initiated.

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