Homeostasis Flashcards

1
Q

Homeostasis

A
  • Maintenance of a relatively stable internal environment despite continuous outside changes
  • A dynamic state of equilibrium
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2
Q

Homeostatic Control Mechanisms

A

Involve continuous monitoring and regulation of many factors (variables)

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3
Q

Nervous and endocrine systems accomplish the communication via

A

nerve impulses and hormones

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4
Q

Components of a Control Mechanism

A
  1. Receptor
  2. Control center
  3. Effector
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5
Q

Receptor

A

(sensor)
Monitors the environment
Responds to stimuli (changes in controlled variables)

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6
Q

Control center

A

Determines the set point at which the variable is maintained
Receives input from receptor
Determines appropriate response

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7
Q

Effector

A

Receives output from control center
Provides the means to respond
Response acts to reduce or enhance the stimulus (feedback)

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8
Q

Negative Feedback

A

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)

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9
Q

Negative Feedback: Regulation of Blood Volume by ADH

A
  • 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
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10
Q

Thermoregulation

A

the process by which animals maintain an internal temperature within a tolerable range

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11
Q

Endotherms

A

animals that primarily produces its own heat

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12
Q

Ectotherms

A

animals that primarily gains heat through the environment

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13
Q

Homeotherms

A

animals that have a constant body temperature

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14
Q

Poikilotherms

A

animals whose body temperature varies depending on the environment

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15
Q

Organisms exchange heat by four physical processes

A

radiation, evaporation, convection, and conduction

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16
Q

the integumentary system

A

skin, hair, and nails; heat regulation in mammals

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17
Q

Five adaptations help animals thermoregulate

A

Insulation
Circulatory adaptations
Cooling by evaporative heat loss
Behavioral responses
Adjusting metabolic heat production

18
Q

Insulation

A

a major thermoregulatory adaptation in mammals and birds

19
Q

Circulatory Adaptations

A

Regulation of blood flow near the body surface significantly affects thermoregulation
Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin

20
Q

vasodilation

A

blood flow in the skin increases, facilitating heat loss

21
Q

vasoconstriction

A

blood flow in the skin decreases, lowering heat loss

22
Q

countercurrent exchange

A

The arrangement of blood vessels in many marine mammals and birds allows for it

23
Q

Countercurrent heat exchangers transfer heat between

A

fluids flowing in opposite directions and thereby reduce heat loss

24
Q

Thermogenesis

A

the adjustment of metabolic heat production to maintain body temperature

25
Q

Thermogenesis is increased by

A

muscle activity such as moving or shivering

26
Q

Nonshivering thermogenesis takes place when

A

hormones cause mitochondria to increase their metabolic activity (brown fat)

27
Q

hypothalamus

A

region of the brain where thermoregulation in mammals is controlled

28
Q

Positive Feedback

A

The response enhances or exaggerates the original stimulus
May exhibit a cascade or amplifying effect

29
Q

Usually controls infrequent events e.g.:

A

Enhancement of labor contractions by oxytocin
Platelet plug formation and blood clotting

30
Q

Alterations in Homeostasis

A

Set points and normal ranges can change with age or show cyclic variation

31
Q

Disturbance of homeostasis

A
  • Increases risk of disease
  • Contributes to changes associated with aging
  • May allow destructive positive feedback mechanisms to take over (e.g., heart failure)
32
Q

Circadian rhythm

A

governs physiological changes that occur roughly every 24 hours in animals and plants

33
Q

Acclimatization

A

Homeostasis can adjust to long term changes in external environment

34
Q

The Endocrine System

A
  • Homeostasis & internal communication
  • Endocrine and nervous systems work together
  • hormones released into the bloodstream travel
    throughout the body
  • certain parts release hormones into blood
  • rest releases neurotransmitters excite or inhibit nerve, muscle & gland cells
35
Q

What do hormones regulate?

A
  • Homeostasis
  • Blood pressure
  • Blood volume
  • Energy metabolism and allocation
  • Solute concentrations
  • Mediate responses to environmental stimuli
  • Regulate growth and development
  • Trigger changes underlying sexual maturity/reproduction
36
Q

Hormone Receptors

A

Hormones only affect target cells with specific membrane proteins called receptors

37
Q

Secreted molecules diffuse into bloodstream, trigger response in

A

target cells anywhere in body

38
Q

Secreted molecules diffuse locally and trigger response in

A

neighboring cells

39
Q

Secreted molecules diffuse locally and trigger response in

A

cells that secrete them

40
Q

Lipid-soluble Hormones

A

Needs transport protein in blood (mostly water), but Can easily diffuse through cell membrane (lipid)

41
Q

Water-soluble Hormones

A

Soluble in blood (mostly water), but needs to bind to a receptor to send signal into the cell

42
Q

Hormonal Interactions

A

Permissive effect
Synergistic effect
Antagonistic effects