Chapter 40: Homeostasis

Question 1

What does homeostasis depend on?

Answer 1

function of organs and organ systems

Question 2

What does homeostasis do?

Answer 2

regulates body temperature and maintains a “constant” environment, functional range of intracellular milieu, and dynamic control (thermostat)

Question 3

What are the two types of organisms homeostasis regulates?

Answer 3

ectotherms and endotherms

Question 4

What is the vertebrate thermostat?

Answer 4

the neutral control of body temperature

Question 5

What are 4 characteristics of homeostasis?

Answer 5

1. maintaining various aspects of internal environment of an organism at a steady level
2. needs of cells are exhibited by whole organism
3. cells are surrounded by extracellular fluids, interacts w/ circulatory system
4. depends on functions of organs/organ systems of the body

Question 6

What is the compartmentalization component of homeostasis?

Answer 6

• skin separates the internal and external environments.
• circulatory system moves materials to and from all parts of internal environment
• fluids of internal environment bathe all cells of organism and differ in composition
• cells of organs exchange materials via internal environment
• some organs exchange materials between internal/external environment

Question 7

when is compartmentalization useless?

Answer 7

if activity isn’t coordinated

Question 8

What is the composition of fluids in the body?

Answer 8

1/3 ECF: 20% Plasma/80% Interstitial Fluid

2/3 Intracellular Fluid (ICF)

Question 9

What is the pathway for regulatory control?

Answer 9

Receptor (Sensor percieves magnitude of parameter)–>Control Center (Integrator compares sensor input with set point then instructs effectors)–>Effector (changes parameter to return it to set point)

Question 10

Negative Feedback

Answer 10

detect direction of change and reverse it

Question 11

Examples of negative feedback (2)

Answer 11

temperature and insulin

Question 12

Positive Feedback

Answer 12

detect direction of change and enhance it (once begun, quickly complete)

Question 13

Feed-forward

Answer 13

internal circadian clock; behavior change to avoid challenging event

Question 14

Example of feed-forward

Answer 14

temperature regulation

Question 15

Negative Feedback Regulation Pathway

Answer 15

1. Receptors obtain info about internal environment
2. Receptors send info to central neural processing center where info about current internal state is compared to that of the desired state (set point)
3. Neural processing center stimulates effectors which generate an adaptive response that changes the internal state to the desired state
4. The establishment of desired state is detected by receptors and info (by neg FB) is directed to the processing center which turns off adaptive response

Question 16

What are organs made up of?

Answer 16

Tissues (cells with similar structures and function)

Question 17

What are the 4 types of tissues?

Answer 17

1. epithelial tissues (tightly connected)
2. connective (embedded in ECM)
3. Muscle (can contract)
4. nervous (neurons, process/convey info)

Question 18

What temperatures damage cells?

Answer 18

below 0 degrees C and above 45 degrees C

Question 19

What do rates of biological reaction depend on?

Answer 19

temperature

Question 20

What is the Q10 for biological systems?

Answer 20

between 2 and 3

reaction rate increases 2-3 times as the temperature increases by 10 degrees C

Question 21

What season is the metabolic rate higher in ?

Answer 21

summer

Question 22

What is the actual rates of the seasons?

Answer 22

the same

Question 23

Acclimization is reached by…

Answer 23

metabolic compensation

Question 24

What is metabolic compensation?

Answer 24

expressing similar enzyme with different temperature optimum

Question 25

Homeotherm

Answer 25

maintains relatively constant body temperature with changes in environmental temp

Question 26

Poikilotherm

Answer 26

changes body temp with changes in environmental temp

Question 27

Heterotherm

Answer 27

regulates body temp at constant level some of the time

Question 28

Endotherms - how do they generate heat

Answer 28

generate heat internally by metabolic processes; use metabolic active mechanisms for heat loss (birds/mammals)

Question 29

Ectotherms - how do they generate heat

Answer 29

depend largely on external source of heat (fish, frog, lizard)

Question 30

Endotherms - how do they respond to outside temp

Answer 30

metabolic rate raises when temperature falls below or above set point of body temperature

Question 31

Ectotherms - how do they respond to outside temp

Answer 31

metabolic rate increases with a temperature increase

Question 32

How do ectotherms regulate their body temperature?

Answer 32

with their behavior; control blood flow to skin, produce metabolic heat during active muscle use, countercurrent exchange

Question 33

Countercurrent exchange

Answer 33

helps keep body heat in core of some ectotherms

Question 34

Countercurrent flow

Answer 34

small gradients are maintained

Question 35

Concurrent flow

Answer 35

large gradients disappear quickly

Question 36

How do Endotherms regulate body temperature?

Answer 36

1. Behavior 2. Control of blood flow to skin 3. Pilomotor control regulates insulation of fur and feathers 4. countercurrent heat exchanger

Question 37

What is the relation between metabolic rate and body mass?

Answer 37

As body mass increases, metabolic rate increases.

Question 38

What is the relation between body size and metabolic rate?

Answer 38

As body size increases, metabolic rate decreases.

Question 39

Basal metabolic rate of endotherm v. ectotherm

Answer 39

endotherm: 6 times greater than ectotherm at rest/same temp | endotherm generates more internal heat

Question 40

Neutral zone endotherm

Answer 40

regulate body temp without changing metabolic rate and can maintain metabolism at basal metabolic rate

Question 41

What happens below a critical temperature?

Answer 41

endotherm metabolic rate increases as environmental temp decreases since animal must produce more internal heat to maintain constant body temp as heat loss to environment increases

Question 42

Do endotherms also use countercurrent heat exchange?

Answer 42

yes

Question 43

Shivering Thermogenesis

Answer 43

muscle contraction with little movement

Question 44

Nonshivering Thermogenesis

Answer 44

mostly occurs in brown fat cells & thermogenin uncouples oxidative phosphorylation, leak across inner mitochondrial membrane

Question 45

Thermogenin

Answer 45

uncouples oxidative phosphorylation

Question 46

How does evaporative water loss happen?

Answer 46

-sweating or -panting (dissipate heat from body @ environmental temp above upper critical temp.)

Question 47

What adaptations to hot and cold climates are there?

Answer 47

- increase in thermal insulation (fur, feathers, fat) | - change in volume/surface ratio

Question 48

Hypothalamus

Answer 48

structure that controls body temp

Question 49

How does the hypothalamus control body temp?

Answer 49

contains temp sensing receptor cell-->establishes temp set point-->sends signals to turn on or off the adaptive response

Question 50

Fever

Answer 50

pyrogens/viruses cause increase to the set point which leads to increased body temp

Question 51

Shallow torpor

Answer 51

animals drop body temp on a daily basis at times when they are not usually active

Question 52

Hibernation

Answer 52

certain animals lower their set point and body temp for weeks; conserves energy

Question 53

Sleep

Answer 53

set points are lower than during wakefulness