Chapter 40: Homeostasis Flashcards
What does homeostasis depend on?
function of organs and organ systems
What does homeostasis do?
regulates body temperature and maintains a “constant” environment, functional range of intracellular milieu, and dynamic control (thermostat)
What are the two types of organisms homeostasis regulates?
ectotherms and endotherms
What is the vertebrate thermostat?
the neutral control of body temperature
What are 4 characteristics of homeostasis?
- maintaining various aspects of internal environment of an organism at a steady level
- needs of cells are exhibited by whole organism
- cells are surrounded by extracellular fluids, interacts w/ circulatory system
- depends on functions of organs/organ systems of the body
What is the compartmentalization component of homeostasis?
- 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
when is compartmentalization useless?
if activity isn’t coordinated
What is the composition of fluids in the body?
1/3 ECF: 20% Plasma/80% Interstitial Fluid
2/3 Intracellular Fluid (ICF)
What is the pathway for regulatory control?
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)
Negative Feedback
detect direction of change and reverse it
Examples of negative feedback (2)
temperature and insulin
Positive Feedback
detect direction of change and enhance it (once begun, quickly complete)
Feed-forward
internal circadian clock; behavior change to avoid challenging event
Example of feed-forward
temperature regulation
Negative Feedback Regulation Pathway
- Receptors obtain info about internal environment
- Receptors send info to central neural processing center where info about current internal state is compared to that of the desired state (set point)
- Neural processing center stimulates effectors which generate an adaptive response that changes the internal state to the desired state
- 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
What are organs made up of?
Tissues (cells with similar structures and function)
What are the 4 types of tissues?
- epithelial tissues (tightly connected)
- connective (embedded in ECM)
- Muscle (can contract)
- nervous (neurons, process/convey info)
What temperatures damage cells?
below 0 degrees C and above 45 degrees C
What do rates of biological reaction depend on?
temperature
What is the Q10 for biological systems?
between 2 and 3
reaction rate increases 2-3 times as the temperature increases by 10 degrees C
What season is the metabolic rate higher in ?
summer
What is the actual rates of the seasons?
the same
Acclimization is reached by…
metabolic compensation
What is metabolic compensation?
expressing similar enzyme with different temperature optimum
Homeotherm
maintains relatively constant body temperature with changes in environmental temp
Poikilotherm
changes body temp with changes in environmental temp
Heterotherm
regulates body temp at constant level some of the time
Endotherms - how do they generate heat
generate heat internally by metabolic processes; use metabolic active mechanisms for heat loss (birds/mammals)
Ectotherms - how do they generate heat
depend largely on external source of heat (fish, frog, lizard)
Endotherms - how do they respond to outside temp
metabolic rate raises when temperature falls below or above set point of body temperature
Ectotherms - how do they respond to outside temp
metabolic rate increases with a temperature increase
How do ectotherms regulate their body temperature?
with their behavior; control blood flow to skin, produce metabolic heat during active muscle use, countercurrent exchange
Countercurrent exchange
helps keep body heat in core of some ectotherms
Countercurrent flow
small gradients are maintained
Concurrent flow
large gradients disappear quickly
How do Endotherms regulate body temperature?
- Behavior
- Control of blood flow to skin
- Pilomotor control regulates insulation of fur and feathers
- countercurrent heat exchanger
What is the relation between metabolic rate and body mass?
As body mass increases, metabolic rate increases.
What is the relation between body size and metabolic rate?
As body size increases, metabolic rate decreases.
Basal metabolic rate of endotherm v. ectotherm
endotherm: 6 times greater than ectotherm at rest/same temp
endotherm generates more internal heat
Neutral zone endotherm
regulate body temp without changing metabolic rate and can maintain metabolism at basal metabolic rate
What happens below a critical temperature?
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
Do endotherms also use countercurrent heat exchange?
yes
Shivering Thermogenesis
muscle contraction with little movement
Nonshivering Thermogenesis
mostly occurs in brown fat cells & thermogenin uncouples oxidative phosphorylation, leak across inner mitochondrial membrane
Thermogenin
uncouples oxidative phosphorylation
How does evaporative water loss happen?
-sweating or -panting (dissipate heat from body @ environmental temp above upper critical temp.)
What adaptations to hot and cold climates are there?
- increase in thermal insulation (fur, feathers, fat)
- change in volume/surface ratio
Hypothalamus
structure that controls body temp
How does the hypothalamus control body temp?
contains temp sensing receptor cell–>establishes temp set point–>sends signals to turn on or off the adaptive response
Fever
pyrogens/viruses cause increase to the set point which leads to increased body temp
Shallow torpor
animals drop body temp on a daily basis at times when they are not usually active
Hibernation
certain animals lower their set point and body temp for weeks; conserves energy
Sleep
set points are lower than during wakefulness
