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

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 terminology Observation Palpation Auscultation

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)

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 Complementarity Anatomy 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 tissues Organ system: organs that work closely together Organismal: all organ systems

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

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

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

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

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

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

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

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

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

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 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

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)

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

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)

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

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

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

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

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)