1. The Human Body: An Orientation: Part A
Chapter 1
The Human Body:
An Orientation:
Part A

2. 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)

3. Overview of Anatomy and Physiology
Essential tools for the study of anatomy:
Anatomical terminology
Observation
Palpation
Auscultation

4. Overview of Anatomy and Physiology
Physiology: The study of function of the body at many levels
Subdivisions are based on organ systems (e.g., renal, digestive, cardiovascular physiology)

5. 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

6. Principle of Complementarity
Anatomy and physiology are inseparable.
Function always reflects structure
What a structure can do depends on its specific form

7. 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 tissues
Organ system: organs that work closely together
Organismal: all organ systems

8. Cellular level Cells are made up of molecules. 1
Organelle
Atoms
Molecule
Smooth muscle cell 2
Cellular level Cells are made up of molecules. 1
Chemical level Atoms combine to form molecules.
Smooth muscle tissue
Cardiovascular system 3
Tissue level Tissues consist of similar types of cells.
Heart
Blood vessels
Blood vessel (organ)
Smooth muscle tissue
Connective tissue
Epithelial tissue 4
Organ level Organs are made up of different types of tissues.
Organismal level The human organism is made up of many organ systems. 6 5
Organ system level Organ systems consist of different organs that work together closely.
Figure 1.1, step 6

9. Overview of Organ Systems
Major organs and functions of the 11 organ systems

10. Digestive system
Nervous system
Respiratory system
Cardiovascular system
Lymphatic system
Urinary system Organ Systems
Muscular system
Skeletal system
Integumentary system
Endocrine system
Reproductive system

11. Organ Systems Interrelationships
All cells depend on organ systems to meet their survival needs
Organ systems work cooperatively to perform necessary life functions

12. Necessary Life Functions
Boundary: Maintaining boundaries between internal and external environments
Plasma membranes
Skin
Movement: (contractility)
Of body parts (skeletal muscle)
Of substances (cardiac and smooth muscle)

13. Necessary Life Functions
Responsiveness: The ability to sense and respond to stimuli
Withdrawal reflex
Control of breathing rate
Digestion:
Breakdown of ingested foodstuffs
Absorption of simple molecules into blood

14. Necessary Life Functions
Metabolism: All chemical reactions that occur in body cells
Catabolism and anabolism
Excretion: The removal of wastes from metabolism and digestion
Urea, carbon dioxide, feces

15. Necessary Life Functions
Reproduction:
Cellular division for growth or repair
Production of offspring
Growth: Increase in size of a body part or of organism

16. Survival Needs
Nutrients:
Chemicals for energy and cell building
Carbohydrates, fats, proteins, minerals, vitamins
Oxygen:
Essential for energy release (ATP production)

17. Survival Needs
Water:
Most abundant chemical in the body
Site of chemical reactions
Body temperature:
Affects rate of chemical reactions
Atmospheric pressure:
For adequate breathing and gas exchange in the lungs

18. A dynamic state of equilibrium
Homeostasis
It is the maintenance of a relatively stable internal environment despite continuous changes both inside and out
A dynamic state of equilibrium

19. Homeostatic Control Mechanisms
Involve continuous monitoring and regulation of many factors (variables)
Nervous and endocrine systems accomplish the communication via nerve impulses and hormones

20. Components of a Control Mechanism
Receptor (sensor)
Monitors the environment
Responds to stimuli (changes in controlled variables)
Control center
Determines the set point at which the variable is maintained
Receives input from receptor
Determines appropriate response

21. Components of a Control Mechanism
Effector
Receives output from control center
Provides the means to respond
Response acts to reduce or enhance the stimulus (feedback)

22. Output: Information sent along efferent pathway to effector. 4 3
Input: Information sent along afferent pathway to control center.
Control Center
Afferent pathway
Efferent pathway 2
Receptor
Effector 5
Receptor detects change.
Response of effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level. 1
IMBALANCE
Stimulus produces change in variable.
BALANCE
IMBALANCE
Figure 1.4, step 5

23. Negative Feedback
The 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)

24. Temperature-sensitive Temperature-sensitive
Control Center
(thermoregulatory
center in brain)
Information sent
along the afferent
pathway to control
center
Information sent
along the efferent
pathway to
effectors
Afferent
pathway
Efferent
pathway
Receptors
Temperature-sensitive
cells in skin and brain
Effectors
Sweat glands
Sweat glands activated
Response
Evaporation of sweat
Body temperature falls;
stimulus ends
Stimulus
Body temperature
rises
BALANCE
Stimulus
Body temperature falls
Response
Body temperature rises;
stimulus ends
Receptors
Temperature-sensitive
cells in skin and brain
Effectors
Skeletal muscles
Efferent
pathway
Afferent
pathway
Shivering
begins
Information sent
along the efferent
pathway to effectors
Information sent
along the afferent
pathway to control
center
Control Center
(thermoregulatory
center in brain)
Figure 1.5

25. Negative Feedback: Regulation of Blood Volume by ADH
Receptors 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

26. Positive Feedback
The response enhances or exaggerates the original stimulus
Enhancement of labor contractions by oxytocin (Chapter 28)
Platelet plug formation and blood clotting

27. 1 3 2 4 Break or tear occurs in blood vessel wall.
Positive feedback cycle is initiated. 3
Released chemicals attract more platelets.
Platelets adhere to site and release chemicals. 2
Positive feedback loop
Feedback cycle ends when plug is formed. 4
Platelet plug forms.
Figure 1.6, step 4

28. 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)