The Human Body: An Orientation - bloodhounds Incorporated

The Human Body: An Orientation - bloodhounds Incorporated

The Human Body: An Orientation Chapter 1 Overview of Anatomy and Physiology Anatomy Study of structure Subdivisions: Gross or macroscopic (e.g., regional, systemic, and surface anatomy) Microscopic (e.g., cytology and histology) Developmental (e.g., embryology) 2013 Pearson Education, Inc. Overview of Anatomy and Physiology

Physiology Study of the function of the body Subdivisions based on organ systems (e.g., renal or cardiovascular physiology) Often focuses on cellular and molecular level Body's abilities depend on chemical reactions in individual cells 2013 Pearson Education, Inc. Principle of Complementarity Anatomy and physiology are inseparable Function always reflects structure

What a structure can do depends on its specific form 2013 Pearson Education, Inc. Figure 1.2 Examples of interrelationships among body organ systems. Digestive system Takes in nutrients, breaks them down, and eliminates unabsorbed matter (feces) Respiratory system Takes in oxygen and eliminates carbon dioxide O2 Food CO2 Cardiovascular system Via the blood, distributes oxygen and nutrients to all body cells and delivers wastes and carbon dioxide to disposal organs Blood

Nutrients CO2 O2 Hear t Interstitial fluid Urinary system Eliminates nitrogenous wastes and excess ions Nutrients and wastes pass between blood and cells via the interstitial fluid Feces Integumentary system Protects the body as a whole from the external environment

Urine 2013 Pearson Education, Inc. Hierarchy of Structural Organization Chemical Cellular Tissue Organ Organ System Organism Homeostasis The ability of the body to maintain relatively stable internal conditions even though there is continuous change in the outside world A state of dynamic equilibrium The body functions within relatively narrow limits

All body systems contribute to its maintenance Control Mechanisms Regardless of the factor or event (variable) being regulated, all homeostatic control mechanisms have at least three interdependent components Receptor (stimuli of change is detected) Control center (determines response) Effector (bodily response to the stimulus) Control Mechanisms Regulation of homeostasis is accomplished through the nervous and

endocrine systems Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions. 3 Input: Information sent along afferent pathway to control center. 2 Receptor detects change. 1 Stimulus produces change in variable. Receptor IM BA L AN

Control Center Afferent pathway Slide 1 4Output: Information sent along efferent pathway to effector. Efferent pathway Effector 5 Response of effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level. CE

BALANCE IM BA L AN CE 2013 Pearson Education, Inc. Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions. IM 1 Stimulus produces change in variable. BA L AN

Slide 2 CE BALANCE IM BA L AN CE 2013 Pearson Education, Inc. Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions. 2 Receptor detects change. 1 Stimulus produces change in variable.

Slide 3 Receptor IM BA L AN CE BALANCE IM BA L AN CE 2013 Pearson Education, Inc. Figure 1.4 Interactions among the elements of a homeostatic control system maintain

stable internal conditions. 3 Input: Information sent along afferent pathway to control center. 2 Receptor detects change. 1 Stimulus produces change in variable. BA L AN Control Center Afferent pathway Receptor

IM Slide 4 CE BALANCE IM BA L AN CE 2013 Pearson Education, Inc. Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions. 3 Input: Information sent along afferent pathway to control center. 2 Receptor

detects change. 1 Stimulus produces change in variable. Afferent pathway Receptor IM BA L AN Control Center Slide 5 4Output: Information sent along efferent pathway to effector.

Efferent pathway Effector CE BALANCE IM BA L AN CE 2013 Pearson Education, Inc. Figure 1.4 Interactions among the elements of a homeostatic control system maintain stable internal conditions. 3 Input: Information sent along afferent pathway to control center.

2 Receptor detects change. 1 Stimulus produces change in variable. Afferent pathway Receptor IM BA L AN Control Center Slide 6 4Output: Information sent along efferent pathway to effector.

Efferent pathway Effector 5 Response of effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level. CE BALANCE IM BA L AN CE

2013 Pearson Education, Inc. Negative Feedback Most feedback mechanisms in body Response reduces or shuts off original stimulus Variable changes in opposite direction of initial change Examples Regulation of body temperature (a nervous system mechanism) Regulation of blood volume by ADH (an endocrine system mechanism) 2013 Pearson Education, Inc. Figure 1.5 Body temperature is regulated by a negative feedback mechanism. Control Center (thermoregulatory center in brain) Afferent

pathway Efferent pathway Receptors Effectors Sweet glands Temperature-sensitive cells in skin and brain) Sweat glands activated Body temperature rises IM B AL AN C Response Evaporation of sweat Body temperature falls;

stimulus ends E BALANCE Stimulus: Heat Stimulus: Cold Response IM B Body temperature rises; stimulus ends Receptors Temperature-sensitive cells in skin and brain Effectors Skeletal muscles Shivering begins Body temperature

AL falls AN CE Efferent pathway Afferent pathway Control Center (thermoregulatory center in brain) 2013 Pearson Education, Inc. 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 kidneys (effectors) to return more water to the blood

2013 Pearson Education, Inc. Positive Feedback Response enhances or exaggerates original stimulus May exhibit a cascade or amplifying effect Usually controls infrequent events that do not require continuous adjustment Enhancement of labor contractions by oxytocin (chapter 28) Platelet plug formation and blood clotting 2013 Pearson Education, Inc. Control Mechanisms A chain of events . . . Stimulus produces a change in a variable

Change is detected by a sensory receptor Sensory input information is sent along an afferent pathway to control center Control center determines the response Output information sent along efferent pathway to activate response Monitoring of feedback to determine if additional response is required Negative Feedback Mechanisms Most control mechanisms are negative feedback mechanisms A negative feedback mechanism decreases the intensity of the stimulus or eliminates it

The negative feedback mechanism causes the system to change in the opposite direction from the stimulus Example: home heating thermostat Positive Feedback Mechanisms A positive feedback mechanism enhances or exaggerates the original stimulus so that activity is accelerated It is considered positive because it results in change occurring in the same direction as the original stimulus Positive feedback mechanisms usually control infrequent events such as blood clotting or childbirth Positive Feedback Response enhances or exaggerates original stimulus May exhibit a cascade or amplifying effect Usually controls infrequent events that do not require continuous adjustment

Enhancement of labor contractions by oxytocin (chapter 28) Platelet plug formation and blood clotting 2013 Pearson Education, Inc. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug. Slide 1 1 Break or tear occurs in blood vessel wall. Positive feedback cycle is initiated. 3 Released chemicals attract more platelets. Positive feedback loop

2 Platelets adhere to site and release chemicals. Feedback cycle ends when plug is formed. 4 Platelet plug is fully formed. 2013 Pearson Education, Inc. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug. Slide 2 1 Break or tear occurs in blood vessel wall. Positive feedback cycle is initiated. 2013 Pearson Education, Inc. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug. Slide 3 1 Break or tear

occurs in blood vessel wall. Positive feedback cycle is initiated. 2 Platelets adhere to site and release chemicals. 2013 Pearson Education, Inc. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug. Slide 4 1 Break or tear occurs in blood vessel wall. Positive feedback cycle is initiated. 3 Released chemicals attract more platelets.

Positive feedback loop 2 Platelets adhere to site and release chemicals. 2013 Pearson Education, Inc. Figure 1.6 A positive feedback mechanism regulates formation of a platelet plug. Slide 5 1 Break or tear occurs in blood vessel wall. Positive feedback cycle is initiated. 3 Released chemicals attract more platelets. Positive feedback loop

2 Platelets adhere to site and release chemicals. Feedback cycle ends when plug is formed. 4 Platelet plug is fully formed. 2013 Pearson Education, Inc. Homeostatic Imbalance Disturbance of homeostasis Increases risk of disease Contributes to changes associated with aging Control systems less efficient

If negative feedback mechanisms overwhelmed Destructive positive feedback mechanisms may take over (e.g., heart failure) 2013 Pearson Education, Inc. Homeostatic Imbalances Most diseases cause homeostatic imbalances (chills, fevers, elevated white blood counts etc.) Aging reduces our ability to maintain homeostasis Heat stress

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