The Human Body:

An Orientation: Part A

Chapter 1

Overview of Anatomy and Physiology

Anatomy: The study of structure of the body

Subdivisions:Gross or macroscopic (e.g., regional, surface, and systemic anatomy)

Microscopic (e.g., cytology and histology)

Developmental (e.g., embryology)

Overview of Anatomy and Physiology

Essential tools for the study of anatomy:Anatomical terminologyObservationPalpation Auscultation

Overview of Anatomy and Physiology

Physiology: The study of function of the body at many levelsSubdivisions are based on organ systems (e.g., renal, digestive, cardiovascular physiology)

Overview of Anatomy and Physiology

Essential tools for the study of physiology:Ability to focus at many levels (from systemic to cellular and molecular)

Basic physical principles (e.g., electrical currents, pressure, and movement)

Basic chemical principles

Principle of ComplementarityAnatomy and physiology are inseparable.Function always reflects structure

What a structure can do depends on its specific form

Levels of Structural Organization

Chemical: atoms and molecules (Chapter 2)

Cellular: cells and their organelles (Chapter 3)

Tissue: groups of similar cells (Chapter 4)Organ: contains two or more types of

tissuesOrgan system: organs that work closely

togetherOrganismal: all organ systems

Cardiovascularsystem

OrganelleMoleculeAtoms

Chemical levelAtoms combine to form molecules.

Cellular levelCells are made up ofmolecules.

Tissue levelTissues consist of similartypes of cells.

Organ levelOrgans are made up of different typesof tissues.

Organ system levelOrgan systems consist of differentorgans that work together closely.

Organismal levelThe human organism is made upof many organ systems.

Smooth muscle cell

Smooth muscle tissue

Connective tissue

Blood vessel (organ)

HeartBloodvessels

Epithelialtissue

Smooth muscle tissue

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Figure 1.1, step 6

Overview of Organ Systems

Major organs and functions of the 11 organ systems

Digestive systemNervous systemRespiratory systemCardiovascular systemLymphatic systemUrinary system Organ

SystemsMuscular systemSkeletal systemIntegumentary systemEndocrine systemReproductive system

Organ Systems Interrelationships

All cells depend on organ systems to meet their survival needs

Organ systems work cooperatively to perform necessary life functions

Necessary Life Functions1. Boundary: Maintaining

boundaries between internal and external environments

Plasma membranes Skin

2. Movement: (contractility) Of body parts (skeletal muscle) Of substances (cardiac and

smooth muscle)

Necessary Life Functions3. Responsiveness: The ability to

sense and respond to stimuli Withdrawal reflex Control of breathing rate

4. Digestion: Breakdown of ingested

foodstuffs Absorption of simple molecules

into blood

Necessary Life Functions5.Metabolism: All chemical

reactions that occur in body cells

Catabolism and anabolism6.Excretion: The removal of

wastes from metabolism and digestion

Urea, carbon dioxide, feces

Necessary Life Functions

7.Reproduction: Cellular division for

growth or repairProduction of offspring

8.Growth: Increase in size of a body part or of organism

Survival Needs1. Nutrients:

Chemicals for energy and cell building

Carbohydrates, fats, proteins, minerals, vitamins

2. Oxygen: Essential for energy release

(ATP production)

Survival Needs3. Water:

Most abundant chemical in the body

Site of chemical reactions4. Body temperature:

Affects rate of chemical reactions 5. Atmospheric pressure:

For adequate breathing and gas exchange in the lungs

HomeostasisIt is the maintenance of a relatively stable internal environment despite continuous changes both inside and out

A dynamic state of equilibrium

Homeostatic Control Mechanisms

Involve continuous monitoring and regulation of many factors (variables)

Nervous and endocrine systems accomplish the communication via nerve impulses and hormones

Components of a Control Mechanism

1. Receptor (sensor) Monitors the environment Responds to stimuli (changes in

controlled variables)2. Control center

Determines the set point at which the variable is maintained

Receives input from receptor Determines appropriate response

Components of a Control Mechanism

3.EffectorReceives output from control

centerProvides the means to

respond Response acts to reduce or

enhance the stimulus (feedback)

Stimulusproduceschange invariable.

Receptordetectschange.

Input: Informationsent along afferentpathway to controlcenter.

Output:Information sent alongefferent pathway toeffector.

Responseof effectorfeeds backto reducethe effect ofstimulusand returnsvariable tohomeostaticlevel.

Receptor Effector

ControlCenter

BALANCE

Afferentpathway

Efferentpathway

IMBALANCE

IMBALANCE

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5

Figure 1.4, step 5

Negative FeedbackThe response reduces or shuts off the original stimulus

Examples:Regulation of body temperature (a nervous mechanism)

Regulation of blood volume by ADH (an endocrine mechanism)

Figure 1.5

Sweat glands activated

Shiveringbegins

StimulusBody temperaturerises BALANCE

Information sentalong the afferentpathway to controlcenter

Information sentalong the afferentpathway to controlcenter

Afferentpathway

Afferentpathway

Efferentpathway

Efferentpathway

Information sentalong the efferentpathway toeffectors

Information sentalong the efferentpathway to effectors

StimulusBody temperature falls

ReceptorsTemperature-sensitivecells in skin and brain

ReceptorsTemperature-sensitivecells in skin and brain

EffectorsSweat glands

EffectorsSkeletal muscles

Control Center(thermoregulatory

center in brain)

Control Center(thermoregulatory

center in brain)

ResponseEvaporation of sweatBody temperature falls;stimulus ends

ResponseBody temperature rises;stimulus ends

Negative Feedback: Regulation of Blood Volume

by ADHReceptors sense decreased blood volume

Control center in hypothalamus stimulates pituitary gland to release antidiuretic hormone (ADH)

ADH causes the kidneys (effectors) to return more water to the blood

Positive FeedbackThe response enhances or exaggerates the original stimulus

May exhibit a cascade or amplifying effect

Usually controls infrequent events e.g.:Enhancement of labor contractions by oxytocin (Chapter 28)

Platelet plug formation and blood clotting

Feedback cycle endswhen plug is formed.

Positive feedbackcycle is initiated.

Positivefeedbackloop

Break or tearoccurs in bloodvessel wall.

Plateletsadhere to siteand releasechemicals.

Releasedchemicalsattract moreplatelets.

Platelet plugforms.

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Figure 1.6, step 4

Homeostatic Imbalance Disturbance of homeostasis Increases risk of disease Contributes to changes associated with aging

May allow destructive positive feedback mechanisms to take over (e.g., heart failure)