Introduction to the Human BodyIntroduction to the Human Body A. Anatomy and physiology defined. Anatomy and physiology defined B. Levels of structural organizationB. Levels of structural organization C. Life processesC. Life processes D. Anatomical positionD. Anatomical position E. Directional termsE. Directional terms F. Planes and sectionsF. Planes and sections G. Body cavitiesG. Body cavities H. HomeostasisH. Homeostasis 1. Body fluids and exchange1. Body fluids and exchange 2. Regulation by nervous and endocrine2. Regulation by nervous and endocrine mechanismsmechanisms 3. Feedback systems3. Feedback systems

Anatomy (Greek “anatome” =to cut up or Anatomy (Greek “anatome” =to cut up or dissectdissect

Physiology (Greek “physis” =naturePhysiology (Greek “physis” =nature

Levels of Structural Levels of Structural OrganizationOrganization

Life ProcessesLife Processes

Metabolism= catabolism + anabolismMetabolism= catabolism + anabolism

ResponsivenessResponsiveness

MovementMovement

GrowthGrowth

DifferentiationDifferentiation

ReproductionReproduction

Anatomical PositionAnatomical Position

Directional TermsDirectional Terms

Superior vs. InferiorSuperior vs. Inferior

Anterior vs. PosteriorAnterior vs. Posterior

Medial vs. LateralMedial vs. Lateral

Proximal vs. DistalProximal vs. Distal

Superficial vs. DeepSuperficial vs. Deep

Anterior Posterior

superior

inferior

Medial Lateral

Proximal

Distal

Planes and SectionsPlanes and Sections

1.Sagittala. midsagittalb. parasagittal

2. Frontal (coronal)

3.Transverse (cross)

4.ObliquePlanes of the Body

Sections Through the BodySections Through the Body

Body CavitiesBody CavitiesBody Cavities (also

material In Atlas A (A. 12-A.22)

andHandout 1-Body Regions

1. Dorsala. cranialb. vertebral (spinal

2. Ventrala. thoracic(1) pleural-2(2) mediastinum (a) anterior (b)middle(pericardial) (c) posteriorb. abdominopelvic

HomeostasisHomeostasis

(Greek “homoi” =same (Greek “homoi” =same “stasis” =standing still)“stasis” =standing still)

Body Fluids and ExchangeBody Fluids and Exchange

1.Extracellular fluid (ECF)a. interstitial fluidb. plasma

2. Intracellular fluid

The homeostatic responses of the The homeostatic responses of the body are regulated by the combined body are regulated by the combined effects of the effects of the nervous systemnervous system and and the the endocrine systemendocrine system..

REGULATION OF HOMEOSTASIS

Nervous system = electrical messages control events on a millisecond basis; short-term and very specific effects

Endocrine system = chemical messages control events on a minute, hour, daily, monthly, etc. basis; longer-term and more widespread effects

Operation of a Feedback Operation of a Feedback SystemSystem

ConditionCondition

ReceptorReceptor

Control CenterControl Center

Effectors Effectors

ResponseResponse

ConditionCondition- A stimulus or stress disrupts homeostasis in a - A stimulus or stress disrupts homeostasis in a controlled condition which is monitored by a receptor.controlled condition which is monitored by a receptor.

ReceptorReceptor- responds to specific changes in the controlled - responds to specific changes in the controlled condition and sends input to control center.condition and sends input to control center.

Control Center-Control Center- Receives input from receptors, integrates the Receives input from receptors, integrates the information and provides output to specific effectors.information and provides output to specific effectors.

EffectorsEffectors-respond to output from the control center by -respond to output from the control center by bringing about some type of change in the body that bringing about some type of change in the body that counteracts the disruption in homeostasis.counteracts the disruption in homeostasis.

ResponseResponse-the activity of the effectors brings the controlled -the activity of the effectors brings the controlled condition back into normal homeostasis and the negative condition back into normal homeostasis and the negative feedback system is shut down.feedback system is shut down.

Feedback System: Main Players

WHAT IS A FEEDBACK SYSTEM?

CONTROLLED CONDITION

RECEPTOR

RETURN TO HOMEOSTASIS

EFFECTORS

CONTROL CENTER

some physiologic state

senses a change in the condition

integrates incoming information

structure that restores homeostasis

WHAT IS A NEGATIVE FEEDBACK SYSTEM?

A feedback loop in which the body senses a change and activates mechanisms that reverse the change

CONTROL CENTER

medulla of brain

nervous output

RETURN TO HOMEOSTASIS

blood pressure risesturns off

CONTROLLED CONDITION

blood pressure

decreased

RECEPTOR

baroreceptors in blood vessels

decreased activity

EFFECTORS

heart and arterial smooth muscle

increased heart rate and vasoconstriction

end

Positive FeedbackPositive Feedback

WHAT IS A POSITIVE FEEDBACK SYSTEM?

A feedback loop in which the response reinforces the stimulus, triggering a cycle of ever-increasing response

EFFECTORS

uterine smooth muscle contraction

CONTROL CENTER

hypothalamic neurons of brain

oxytocin secretion

RETURN TO HOMEOSTASIS

labor forces baby’s head further into cervix

reinforcing effectsCONTROLLED CONDITION

level of uterine stretch

increased

RECEPTOR

stretch receptors in cervix

increased activity