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The Human Body: An Orientation Part B

Learn about vital life functions, homeostasis, and anatomical position in the human body. Explore the mechanisms that maintain equilibrium and control feedback responses for survival.

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The Human Body: An Orientation Part B

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  1. The Human Body: An Orientation Part B 1

  2. Today! We will learn about……. • Life functions and survival needs • Homeostasis and Feedback mechanisms • Anatomical position and directional terms

  3. Necessary Life Functions • Maintaining boundaries – the internal environment remains distinct from the external • Cellular level – accomplished by plasma membranes • Organismal level – accomplished by the skin

  4. Necessary Life Functions • Movement – locomotion, propulsion (peristalsis), and contractility • Responsiveness – ability to sense changes in the environment and respond to them • Digestion – breakdown of ingested foodstuffs

  5. Necessary Life Functions • Metabolism – all the chemical reactions that occur in the body • Excretion – removal of wastes from the body

  6. Necessary Life Functions • Reproduction – cellular and organismal levels • Cellular – an original cell divides and produces two identical daughter cells • Organismal – sperm and egg unite to make a whole new person • Growth – increase in size of a body part or of the organism

  7. Survival Needs • Nutrients – chemical substances used for energy and cell building • Oxygen – needed for metabolic reactions • Water – provides the necessary environment for chemical reactions

  8. Survival Needs • Maintaining normal body temperature – necessary for chemical reactions to occur at life-sustaining rates • Atmospheric pressure – required for proper breathing and gas exchange in the lungs

  9. Homeostasis • Homeostasis is the ability to maintain a relatively stable internal environment in an ever-changing outside world • The internal environment of the body is in a dynamic state of equilibrium • Chemical, thermal, and neural factors interact to maintain homeostasis

  10. Homeostatic Control Mechanisms • The variable produces a change in the body • The three interdependent components of control mechanisms are: • Receptor – monitors the environments and responds to changes (stimuli) • Control center – determines the set point at which the variable is maintained • Effector – provides the means to respond to the stimulus

  11. Homeostatic Control Mechanisms Controlcenter Input:Informationsent alongafferentpathway to 3 Output:Information sentalong efferentpathway to 4 Effector Receptor (sensor) Changedetectedby receptor 2 Response ofeffector feedsback to influencemagnitude of stimulus andreturnsvariable tohomeostasis 5 Stimulus:Produceschangein variable 1 Imbalance Variable (in homeostasis) Imbalance Figure 1.4

  12. Negative Feedback • In negative feedback systems, the output shuts off the original stimulus • Example: Regulation of blood glucose levels

  13. Negative Feedback Figure 1.5

  14. Positive Feedback • In positive feedback systems, the output enhances or exaggerates the original stimulus • Example: Regulation of blood clotting Figure 1.6

  15. Homeostatic Imbalance • Disturbance of homeostasis or the body’s normal equilibrium • Overwhelming of negative feedback mechanisms allowing destructive positive feedback mechanisms to take over

  16. Anatomical Position • Body erect, feet slightly apart, palms facing forward, thumbs point away from body Figure 1.7a

  17. Directional Terms • Superior– toward the head • Inferior –away from the head

  18. Directional Terms • Anterior– toward the front of the body • Posterior – toward the back of the body

  19. Directional Terms • Medial– toward the midline • Lateral - away from the midline • Intermediate –between a more medial and lateral structure

  20. Directional Terms • Proximal – closer to the origin of the body • Distal – farther from the origin of the body

  21. Directional Terms • Superficial – toward the body surface • Deep –away from the body surface

  22. Directional Terms Table 1.1

  23. Directional Terms Table 1.1

  24. Regional Terms: Anterior View • Axial – head, neck, and trunk • Appendicular – appendages or limbs • Specific regional terminology Figure 1.7a

  25. Regional Terms: Posterior View Figure 1.7b

  26. Anatomical Variability • Humans vary slightly in both external and internal anatomy • Over 90% of all anatomical structures match textbook descriptions, but: • Nerves or blood vessels may be somewhat out of place • Small muscles may be missing • Extreme anatomical variations are seldom seen

  27. Quiz next time over the material in this lecture!

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