Major Themes of Anatomy and physiology

Expected Learning Outcomes

• Define the terms anatomy and physiology.

• Give specific examples to show the interrelationship between anatomy and physiology.

• Describe, in order from simplest to most complex, the major levels of organization in the human organism.

• Give an example of each level of organization.

• Define homeostasis

• List the components of a feedback loop and explain the function of each.

• Compare and contrast positive and negative feedback in terms of the relationship between stimulus and response.

• Explain why negative feedback is the most commonly used mechanism to maintain homeostasis in the body.

• Provide an example of a negative feedback loop that utilizes the nervous system to relay information. Describe the specific organs, structures, cells or molecules (receptors, neurons, CNS structures, effectors, neurotransmitters) included in the feedback loop.

• Provide an example of a negative feedback loop that utilizes the endocrine system to relay information. Describe the specific cells or molecules (production cells, hormones, target cells) included in the feedback loop.

• Provide an example of a positive feedback loop in the body. Describe the specific structures (organs, cells or molecules) included in the feedback loop.

• Provide specific examples to demonstrate how organ systems respond to maintain homeostasis

• Explain how different organ systems relate to one another to maintain homeostasis

• Predict factors or situations affecting various organ systems that could disrupt homeostasis.

• Predict the types of problems that would occur in the body if various organ systems could not maintain homeostasis and allowed regulated variables (body conditions) to move away from normal.

Anatomy—The Study of Form • Examining structure of the human body

• Inspection • Palpation – feeling with fingertips • Auscultation – listening to normal body sounds • Percussion – tapping and then listening to resulting sounds

• Cadaver dissection • Cutting and separating human body tissues to reveal tissue relationships

• Comparative anatomy • Study of multiple species to learn about form and evolution

• Exploratory surgery

• Medical imaging • Viewing the inside of the body without surgery • Radiology—branch of medicine concerned with imaging

• Gross anatomy • Study of structures that can be seen with the naked eye

• Histology • Examination of tissues with microscope

• Histopathology • Microscopic examination of tissues for signs of disease

• Cytology • Study of structure and function of cells

Anatomical Variation

• Anatomy books show most common organization of structures

• Some individuals lack certain muscles

• Some individuals have an atypical number of vertebrae

• Some individuals have an atypical number of certain organs (for example, kidneys)

• Some individuals (1 in 8000) show situs inversus – left-right reversal of organ

• https://www.anatomyatlases.org/AnatomicVariants/AnatomyHP.shtmlnt

Physiology—The Study of Function

• Subdisciplines • Neurophysiology (physiology of nervous system)

• Endocrinology (physiology of hormones)

• Pathophysiology (mechanisms of disease)

• Comparative physiology • Study of different species to learn about body functions

• Basis for much of our understanding of human physiology and the development of new drugs and medical procedures

The Hierarchy of Complexity

• Reductionism—large, complex systems can be understood by studying their simpler components • Essential to scientific thinking

• Holism—“emergent properties” of the whole organism cannot be predicted from the properties of the separate parts • Humans are more than the sum of their parts

The Hierarchy of Complexity

• Organism composed of organ systems

• Organ systems composed of organs

• Organs composed of tissues

• Tissues composed of cells

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• Cells composed of organelles

• Organelles composed of molecules

• Molecules composed of atoms

Homeostasis and Negative Feedback

• Homeostasis—the ability to detect change, activate mechanisms that oppose it, and thereby maintain relatively stable internal conditions

• Claude Bernard (1813–78) • Noted fairly constant internal conditions despite changing external

conditions (for example, temperature)

• Walter Cannon (1871–1945) • Coined the term homeostasis

• Negative feedback allows for dynamic equilibrium within a limited range around a set point • The body senses a change and “negates” or reverses it

• Loss of homeostatic control causes illness or death

Negative Feedback in Thermoregulation

Homeostasis and Negative Feedback

• Because feedback mechanisms alter the original changes that triggered them, they are called feedback loops.

• Homeostasis in body temperature • If too warm, vessels dilate in the skin and sweating begins

(heat-losing mechanism) • If too cold, vessels in the skin constrict and shivering begins (heat-gaining

mechanism)

Homeostatic Compensation for a Postural Change in Blood Pressure

• Receptor—structure that senses change in the body (e.g., stretch receptors above heart that monitor blood pressure)

• Integrating (control) center— control center that processes the sensory information, “makes a decision,” and directs the response (e.g., cardiac center of the brain)

• Effector— cell or organ that carries out the final corrective action to restore homeostasis (e.g., the heart)

Homeostatic Compensation for Blood Calcium Levels

• Ca2+ levels need to be maintained at 9.2 – 10.4 mg/dL for proper nervous and muscle funtion

• Parathyroid hormone (PTH) secreted by parathyroid glands on posterior surface of thyroid when calcium levels low in blood

• PTH raises calcium blood level by four mechanisms

1. Stimulates osteoclast and bone resorption

2. Inhibits osteoblasts and bone deposition

3. Promotes calcium reabsorption by kidneys, so less lost in urine

4. Promotes phosphate excretions by kidneys, so less bone deposition

Figure 7.16b

7 Major Themes of Anatomy and physiology

Positive Feedback and Rapid Change

• Self-amplifying cycle • Leads to greater change in the same direction

• Feedback loop is repeated—change produces more change

• Normal way of producing rapid changes • Examples include: childbirth, blood clotting, protein digestion, and

generation of nerve signals

• Can sometimes be dangerous • Example Heat Shock

• Body temperature above 40C (104˚F) increases speed of chemical reactions, increasing heat

• Which increase the speed of reactions

• Which increase heat

• Until death at 45C (113˚F)

Positive Feedback in Childbirth

Major Themes of Anatomy and physiology