Biopsyc test 3

homeostasis

tendency to maintain a variable such as temperature, within a fixed range

set point

a value that the body works to maintain

negative feedback

homeostatic processes that reduce discrepancies from the set point

allostasis

the adaptive way in which the body changes its set point depending on the situation

how does allostasis differ from homeostasis?

Homeostasis keeps certain body variables within a fixed range by reacting to changes. Allostasis acts in advance to prevent or minimize changes

basal metabolism

energy used to maintain a constant body temperature while at rest

ectothermic (poikilothermic)

controlling temperature by relying on external sources of heat or cooling

endothermic (homeothermic)

controlling temperature by the body’s physiological mechanisms

What is the primary advantage of maintaining a constant high body temperature?

A constant high body temperature keeps an animal ready for rapid, prolonged muscle activity even in cold weather.

Why did mammals evolve a temperature of 37°C (98°F) instead of some other temperature?

Animals gain an advantage in being as warm as possible and therefore as fast as possible. However, proteins lose stability at still higher temperatures.

preoptic anterior hypothalamus (POA)

controls the autonomic responses such as shivering, sweating, changes in heart rate and metabolism, and changes in blood flow to the skin

What are the sources of input to the POA/AH?

receives input from temperatures in the skin and organs, and many cells sense their own temperature.

If you had damage to your POA/AH, what would happen to your body temperature?

you would be much less able to shiver, sweat, or control other physiological mechanisms that control body temperature. However, you could still try to find a place in the environment that keeps you close to your normal temperature.

What evidence indicates that fever is an adaptation to fight illness?

During a fever, the body will shiver or sweat to maintain its elevated temperature at a nearly constant level. a moderate fever inhibits bacterial growth and increases the probability of surviving a bacterial infection.

What is the primary advantage of maintaining a constant high body temperature?

It keeps the muscles ready for rapid, prolonged activity even in cold weather.

Cells in the POA/AH regulate body temperature by monitoring what?

Skin temperature and the temperature of the POA/AH itself

vasopressin

hormone released by the posterior pituitary that raises blood pressure by constricting blood vessels

antidiuretic hormone (ADH)

enables the kidneys to reabsorb water from urine; also known as vasopressin

Osmotic thirst

caused by eating salty foods. Triggered by certain neurons that detect the loss of their own water

hypovolemic thirst

caused by the loss of fluid by bleeding or sweating

osmotic pressure

tendency of water to flow across a semipremeable membrane from the area of low solute concetration to the area of high solute concentration

subfornical organ (SFO)

brain structure adjoining the third ventricle of the brain, where its cells monitor osmotic pressure and sodium concertation

lateral preoptic area

part of the hypothalamus that controls drinking

supraoptic nucleus

part of the hypothalamus that controls the release rate of vasopressin

paraventricular nucleus (PVN)

part of the hypothalamus in which activity tends to limit meal size and damage leads to excessively large meals

Why are you likely to feel thirst just before bedtime? Would you feel just as thirsty if you went to sleep at an unusual time?

your body secretes vasopressin, which helps conserve water and also stimulates thirst. Both responses help you get through the night while you cannot drink. Your circadian rhythm triggers the increased vasopressin, so you would not feel as thirsty before sleep at an unusual time.

angiotensin II

hormone that constricts the blood vessels compensating for the drop in blood pressure; triggers thirst

aldosterone

adrenal hormone that causes the body to retain salt

hypovolemic thirst

caused by low blood volume and relived by water containing solutes.

which of these happens after you eat something salty?

water flows out of the cells

what would happen as a result of adding salt to the body’s extracellular fluids?

Increased osmotic thirst

what does aldosterone do?

it helps the kidneys and other glands retain salt

sham-feeding

procedure in which everything that an animal swallows leaks out a tube connected to the esophagus or stomach

what evidence showed that taste is not sufficient for satiety?

animals that sham-feed do not become satiated, regardless of how much they taste