Unit 2 - Chapter 9 Reading Flashcards
What is homeostasis?
the maintenance of a relatively constant internal physiological environment
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the psychological process that induces or sustains a particular behavior
motivation
yes, and: effect can escalate as deviation worsens from minor distraction (urge to sip water) to a major distraction (raging thirst of person lost in desert)
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active process of maintaining a relative constant internal temperature through behavioral and physiological adjustments
thermoregulation
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General concepts of homeostasis:
- negative feedback
- redundancy
- behavioral compensation
- concept of allostasis
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an animal whose body temperature is regulated chiefly by internal metabolic processes
examples: mammals, birds
endotherm
make heat inside our bodies using metabolism, muscle activity
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animal whose body temperature is regulated by, and whose heat comes mainly from, the environment
examples: snakes and bees
endotherms
get heat from outside our bodies using metabolism, muscle activity
advantages endotherms have over ectotherms
- we can roam more widely, ectotherms need to stay near sources of warmth
- enhanced capacity for oxygen utilization, so muscles will work for longer periods of time in endotherms
Negative feedback allows ———————-
precise control
Name some primarily negative feedback systems.
homeostatic mechanisms that regulate temperature, body fluids and metabolism
the process whereby a system monitors its own output and reduces its activity when a set point is reached
negative feedback
What is a “set point”?
the point of reference in a feedback system
ex. temperature at which a thermostat is set
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What is a set zone?
optimal range of a variable that a negative feedback system tries to maintain
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What does redundancy ensure?
that critical needs are met
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the —————– senses and controls body tempurature
hypothalamus
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How is the hypothalamus an example of homeostatic reduncancy (i.e., two different systems for regulating the same variable)?
lesion experiments showed different hypothalamic sites control 2 separate thermoregulatory systems:
- lesions in preoptic area (POA) of rats impair physiological responses to cold, like shivering and constriction of blood vessels but did not intervere with behaviors like pressing levers to control heating lamps or cooling lamps
- lesions in lateral hypothalamus of rats abolished behavioral regulation of temp but did not affect physiological responses (e.g., they still shivered)
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Animals use behavioral compensation to adjust to ———————– ———————–.
environmental changes
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In general, both ectotherms and endotherms use 3 kinds of temp-regulating behaviors:
Behaviors that change….
1. exposure to the body surface (huddling or extending limbs)
2. external insulation (using clothes or nests)
3. behaviors that change surroundings (move into sun, shade, burrow)
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Why are behavioral methods of thermoregulation especially important to ectotherms?
Since they cannot generate much heat through metabolism, they need to rely more on behavioral methods to preserve warmth or stay cool (lizards move closer to a heat lamp)
yes, and: lizards can develop “behavioral fevers” caused by moving closer to a heat source during bacterial infection
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How could endothermics’ use of internal processes to regulate temperature have a negative effect?
when fighting an infection, we often generate a fever to boost our immune system response. However, sometimes it heats up too much and causes harm
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Name the components of the basic mammalian thermoregulatory system.
receptors in the skin, body core, and hypothalamus detect and transmit information to three neural regions:
- spinal cord
- brainstem
- hypothalamus
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Where are receptors for mammalian thermoregulatory systems?
body core, skin surface, and hypothalamus/POA
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Which neural regions are involved in the thermoregulatory system?
spinal cord, brain stem, and hypothalamus/POA
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What physiological and behavioral responses can thermoregulation cause?
Behavioral: shivering; heat-seeking or avoiding behaviors
Physiological: constriction/dilation of blood vessels; sweating; respiration; thyroid hormone secretion
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the varying behavioral and physiological adjustments that an individual makes in order to maintain optimal (rather than static) functioning of a regulated system in the face of changing environmental stressors
allostasis
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unavoidable expenditures of bodily resources that must then be regained from the external environment
obligatory losses
ex. we lose water when we pee to get ride of waste molecules
these challenge our homeostatic mechanisms
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Even minor deviation from optimal ——— and ——– balance can be lethal.
water; salt
the ———– of the extracellular fluid, resembling dilute ————-, is consistent across different species of animals.
only a few exceptions across hundreds of millions of years of evolution
saltiness; seawater
water contained within our cells is collectively referred to as the
intracellular compartment
fluid that is outside of our cells
extracellular compartment
the fluid outside of our cells (or extracellular compartment) is divided between the —————– and —————–
interstitial fluid; blood plasma
the fluid between cells
interstitial fluid
protein-rich fluid that carries red and white blood cells
blood plasma
———- is continually moving back and forth between intracellular and extracellular compartments.
water
a membrane that is permeable to some molecules but not others is referred to as ——————————
semipermeable (or selectively permeable)
—————- is the movement of water molecules that occurs so as to equalize the concentration of two solutions separated by a semipermeable membrane
osmosis
physical force that pushes or pulls water across a membrane
osmotic pressure
———- ———– occurs when the extracellular fluid becomes too salty
osmotic thirst
a desire to ingest fluids that is stimulated by high concentration of solute (like salt) in the extracellular compartment
osmotic thirst
What could cause ostmotic thirst?
- obligatory water losses (through repiration, urination, etc.) decrease the volume of extracellular fluid and increase the solute concentration of the EC fluid; bc of EC saltiness, water is pulled out of cells through osmosis
- eating a lot of salty food
a solution with a normal concentration of salt in EC fluid (approx. .9%) is called:
physiological saline (or is described as isotonic)
the extracellular fluid serves as a ————, a reservoir of isotonic fluid that provides and acceptw water molecules so cells can maintain proper internal conditions and prevent damage
buffer
neurons that specifically monitor the concentration of extracellular fluid
osmosensory neurons
Where are numerous osmosensory neurons found?
- several regions of the hypothalamus (including preoptic area, anterior hypothalamus, and supraopitc nucleus)
- organum vasculosum of the lamina terminalis (OVLT) which is one of a set of specialized brain structures monitoring fluid balance of body
any of multiple distinct sites that lie in the wall of a cerebral ventricle and monitor the composition of the cerebrospinal fluid
circumventricular organs
outputs from the circumventricular organs project to multiple cortical regions, including ———- and —————, leading to the conscious perception of thirst
insula; anterior cingulate cortex
a peptide hormone from the posterior pituitary that promotes water conservation and increases blood pressure; acts on the kidneys to slow the production of urine by increasing the reabsorption of water
vasopressin (aka arginine vasopressin or antidiuretic hormone)
the production of urine
diuresis
a mineralcorticoid hormone, secreted by adrenal cortex, that promotes the conservation of sodium by the kidneys
aldosterone
thirst is triggered not by salt balance or osmosis but by a decrease in the overall volume of the extracellular fluid
hypovolemia
literally “low volume”
the loss of body fluids and resulting decrease in extracellular volume can cause an individual to experience:
hypovolemic thirst
a decrease in fluid volume in the body does not necessarily change the ———— of the cellular fluid
concentration
a pressure receptor in the heart or a major artery that detects a change in blood pressure
baroreceptor
a word meaning “less salty than normal”
hypotonic
a cardiac hormone that regulates salt-water balance and blood pressure by promoting renal sodium and water excretion and stimulating vasodilation;
in hypovolemic thirst, the heart decreases its secretion of this hormone, which normally reduces blood pressure, inhibits drinking, and promotes excretion of water and salt at the kidnes
atrial natriuretic peptide (ANP)
a hormone produced in the blood by the action of renin and that may play a role in the control of thirst
angiotensin II (AII)
hypovolemic thirst is triggered by —-
loss of fluid volume
Cranial nerve X, which transmits informaiton between the brain and the viscera; the fagus both regulates visceral activity and transmits signals from the viscera to the brain
vagus nerve
a circumventricular organ that possesses neurons governing drinking behavior; stops drinking in anticipation of correcting the extracellular volume and/or concentration of solutes
subfornical organ
what are the two types of thirst
osmotic and hypovolemic
chemicals required for the effective functioning, growth, and maintenance of the body
nutrients