Processes Related to Homeostasis

I. Acclimatization is an improved ability to respond to an environmental stress.

a. The improvement is induced by prolonged exposure to the stress with no change in genetic endowment.

b. If acclimatization occurs early in life, it may be irreversible and is known as a developmental acclimatization.

II. Biological rhythms provide a feedforward component to homeostatic control systems.

a. The rhythms are internally driven by brain pacemakers, but are entrained by environmental cues, such as light, which also serve to phase-shift (reset) the rhythms when necessary.

b. In the absence of cues, rhythms free-run.

III. Apoptosis, regulated cell death, plays an important role in homeostasis by helping to regulate cell numbers and eliminating undesirable cells.

IV. Aging is associated with a decrease in the number of cells in the body and with a disordered functioning of many of the cells that remain.

a. It is a process distinct from the diseases associated with aging.

b. Its physiological manifestations are a deterioration in organ-system function and in the capacity to respond homeostatically to environmental stresses.

V. The balance of substances in the body is achieved by a matching of inputs and outputs. Total body balance of a substance may be negative, positive, or stable.

SECTION A KEY TERMS

homeostasis

eicosanoid

homeostatic control

arachidonic acid

system

cyclic endoperoxide

steady state

prostaglandin

set point

thromboxane

negative feedback

leukotriene

positive feedback

phospholipase A2

error signal

cyclooxygenase (COX)

feedforward

lipoxygenase

reflex

adaptation

learned reflex

acclimatization

acquired reflex

critical period

reflex arc

developmental

stimulus

acclimatization

receptor (in reflex)

circadian rhythm

afferent pathway

entrainment

integrating center

free-running rhythm

effector

phase-shift

efferent pathway

pacemaker

hormone

pineal gland

endocrine gland

melatonin

local homeostatic

apoptosis

response

pool

target cell

negative balance

neurotransmitter

positive balance

paracrine agent

stable balance

autocrine agent

SECTION A REVIEW QUESTIONS

1. Describe five important generalizations about homeostatic control systems.

2. Contrast negative-feedback systems and positivefeedback systems.

3. Contrast feedforward and negative feedback.

4. How do error signals develop, and why are they essential for maintaining homeostasis?

5. List the components of a reflex arc.

6. What is the basic difference between a local homeostatic response and a reflex?

7. List the general categories of intercellular messengers.

8. Describe two types of intercellular communication that do not depend on extracellular chemical messengers.

9. Draw a figure illustrating the various pathways for eicosanoid synthesis.

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

Homeostatic Mechanisms and Cellular Communication CHAPTER SEVEN

10. Describe the conditions under which acclimatization occurs. In what period of life might an acclimatization be irreversible? Are acclimatizations passed on to a person's offspring?

11. Under what conditions do circadian rhythms become free-running?

12. How do phase shifts occur?

13. What are the important environmental cues for entrainment of body rhythms?

14. What are the physiological manifestations of aging?

15. Draw a figure illustrating the balance concept in homeostasis.

16. What are the three possible states of total-body balance of any chemical?

SECTION B

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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Responses

  • Lukas
    Are acclimatization passed on to a person's offspring?
    8 years ago
  • Emilia
    How biological rhythms provide a feed forward component to homeostasis control?
    2 years ago

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