Chapter 1 The Human Body An Orientation Part

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: 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)

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

Atoms Organelle Smooth muscle cell Molecule 1 Chemical level Atoms combine to form molecules. Cardiovascular system Heart Blood vessels 2 Cellular level Cells are made up of molecules. Smooth muscle tissue 3 Tissue level Tissues consist of similar types of cells. Blood vessel (organ) Smooth muscle tissue Connective tissue Epithelial tissue 4 Organ level Organs are made up of different types of tissues. 6 Organismal level The human organism is made up of many organ systems. 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 Systems Muscular system Skeletal system Integumentary system Endocrine system Reproductive system Organ

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 1. 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 Functions 3. 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

Necessary Life Functions 5. Metabolism: All chemical reactions that occur in body cells Catabolism and anabolism 6. Excretion: The removal of wastes from metabolism and digestion

Necessary Life Functions 7. Reproduction: Cellular division for growth or repair Production of offspring 8. Growth: Increase in size of a body part or of organism

Survival Needs 1. Nutrients: Chemicals for energy and cell building Carbohydrates, fats, proteins, minerals, vitamins 2. Oxygen: Essential for energy release (ATP production)

Survival Needs 3. Water: Most abundant chemical in the body Site of chemical reactions 4. Body temperature: Affects rate of chemical reactions 5. Atmospheric pressure: For adequate breathing and gas

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 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. Effector Receives output from control center Provides the means to respond Response acts to reduce or enhance the stimulus

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

Control Center (thermoregulatory center in brain) Information sent along the afferent pathway to control center Afferent pathway Information sent along the efferent pathway to effectors Efferent pathway Receptors Temperature-sensitive cells in skin and brain Effectors Sweat glands activated Response Evaporation of sweat Body temperature falls; stimulus ends Stimulus Body temperature rises BALANCE Stimulus Response Body temperature rises; stimulus ends Body temperature falls Receptors Temperature-sensitive cells in skin and brain Effectors Skeletal muscles Shivering begins Information sent along the efferent pathway to effectors Efferent pathway Afferent pathway Control Center (thermoregulatory center in brain) Information sent along the afferent pathway to control center 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 Break or tear occurs in blood vessel wall. Positive feedback cycle is initiated. 3 Released chemicals attract more platelets. 2 Platelets Positive feedback loop adhere to site and release chemicals. 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)