Homeostasis

Question 1

Homeostasis

Answer 1

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

Question 2

Homeostatic Control Mechanisms

Answer 2

Involve continuous monitoring and regulation of many factors (variables)

Question 3

Nervous and endocrine systems accomplish the communication via

Answer 3

nerve impulses and hormones

Question 4

Components of a Control Mechanism

Answer 4

1. Receptor
2. Control center
3. Effector

Question 5

Receptor

Answer 5

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

Question 6

Control center

Answer 6

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

Question 7

Effector

Answer 7

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

Question 8

Negative Feedback

Answer 8

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)

Question 9

Negative Feedback: Regulation of Blood Volume by ADH

Answer 9

• 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

Question 10

Thermoregulation

Answer 10

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

Question 11

Endotherms

Answer 11

animals that primarily produces its own heat

Question 12

Ectotherms

Answer 12

animals that primarily gains heat through the environment

Question 13

Homeotherms

Answer 13

animals that have a constant body temperature

Question 14

Poikilotherms

Answer 14

animals whose body temperature varies depending on the environment

Question 15

Organisms exchange heat by four physical processes

Answer 15

radiation, evaporation, convection, and conduction

Question 16

the integumentary system

Answer 16

skin, hair, and nails; heat regulation in mammals

Question 17

Five adaptations help animals thermoregulate

Answer 17

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

Question 18

Insulation

Answer 18

a major thermoregulatory adaptation in mammals and birds

Question 19

Circulatory Adaptations

Answer 19

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

Question 20

vasodilation

Answer 20

blood flow in the skin increases, facilitating heat loss

Question 21

vasoconstriction

Answer 21

blood flow in the skin decreases, lowering heat loss

Question 22

countercurrent exchange

Answer 22

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

Question 23

Countercurrent heat exchangers transfer heat between

Answer 23

fluids flowing in opposite directions and thereby reduce heat loss

Question 24

Thermogenesis

Answer 24

the adjustment of metabolic heat production to maintain body temperature

Question 25

Thermogenesis is increased by

Answer 25

muscle activity such as moving or shivering

Question 26

Nonshivering thermogenesis takes place when

Answer 26

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

Question 27

hypothalamus

Answer 27

region of the brain where thermoregulation in mammals is controlled

Question 28

Positive Feedback

Answer 28

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

Question 29

Usually controls infrequent events e.g.:

Answer 29

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

Question 30

Alterations in Homeostasis

Answer 30

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

Question 31

Disturbance of homeostasis

Answer 31

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

Question 32

Circadian rhythm

Answer 32

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

Question 33

Acclimatization

Answer 33

Homeostasis can adjust to long term changes in external environment

Question 34

The Endocrine System

Answer 34

- 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

Question 35

What do hormones regulate?

Answer 35

- 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

Question 36

Hormone Receptors

Answer 36

Hormones only affect target cells with specific membrane proteins called receptors

Question 37

Secreted molecules diffuse into bloodstream, trigger response in

Answer 37

target cells anywhere in body

Question 38

Secreted molecules diffuse locally and trigger response in

Answer 38

neighboring cells

Question 39

Secreted molecules diffuse locally and trigger response in

Answer 39

cells that secrete them

Question 40

Lipid-soluble Hormones

Answer 40

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

Question 41

Water-soluble Hormones

Answer 41

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

Question 42

Hormonal Interactions

Answer 42

Permissive effect Synergistic effect Antagonistic effects