Class Exam 4

what is endothermy

due to cellular respiration, maintaining a stable internal temperature between Tb (body temp) and Ta (ambient temp)

what is homeothermy

maintaining a relativley stable Tb

what are the costs to endothermy

high energetic costs

what are the benefits to endothermy

increased activity levels, broader envionment range, more niche explotation, increased chemcial reaction efficency

what is newtons law of cooling in reference to endothermy

heat loss varies directly proportional to gradient difference between Tb and Ta (ex. mouse needs 20-30x more energy than same sized lizard)

what is the basal rate of metabilism

measure of min. cost to maintain normal Tb during rest

what is field metabolism (FMR)

resting metabolism and energy used for all other activities

what is required metabolism rate (RMR)

the energy required for normal bodily functions at rest, including basic physiological processes like breathing and circulation.

what is the ratio for brain demands

1:1

what is it about the brain and mammals and energy

for some mammals, all of metaolbic rate goes to the brain, for most its 5-25%, this is why mammals sleep a lot

why do we sleep

restores glycogen, brain development (when younger), memory consolidation, conserve energy

what is the relationship between heat loss and disparity between Ta and Tb

positivley correlated, as Tb increases relative to Ta, heat loss increases.

what is the thermoneutral zone

zone over which basal rate of metabolism is independent of Ta. At this range of temps, Tb is indepdenent

what animals have a narrow thermoneutral zone

small mammals

what animals have a large thermalneutral zone

large mammals

what happens when Ta is higher than the mammals thermoneutral zone

msut lose heat via evaporative cooling (ie sweating, panting)

what must a mammal so when Ta is lower than the thermoneutral zone

must increase basal metabolic rate

what is a piloerection

involuntary elevation or flattening of fur in response to temperature (ie goosebumps)

what is vasodilation

constriction of blood vessels resulting in reduced convective movment of heat to body surface

what is vasodilation

dilation of blood vessels resulting in increased convective heat movement to body surface

what are heat windows

regions of the body with thin fur allowing better heat radiation

what is behavioral thermoregulation

using behaviors such as curling up or streching out to retain or release heat

what is the dehrel effect

seasonal shrinking and regrowing of the brain allowing them to conserve energy in the winter (ex. shrews)

what are the main factors impacting heat or cold insulation

piloerection, vasoconstriction, vasodilation, heat windows, behavioral thermoregulation

how does body size impact heat

smaller body means increase surface area which means the body heats and cools faster (and vice versa for large body)

what are the three main ways to increase heat production

shivering, non-shivering thermogenesis, and increasing activity

what is non-shivering thermogenesis (NST)

metabolic process in which the body generates heat without muscle contractions, primarily through brown adipose tissue

how does NST work

increase ion pumping by Na-K active transport pump in cell membranes. Allows oxidation of food reserves with immediate release of heat

why is brown adipose tissue so important for NST

large number of mitochondria, large number of blood vessels, hibernating gland misnomer

most mammals energy requirments depends on body size. what two animals are exceptions to this

marine mammals (need more than expected), sloths (need less than expected)

what is regional heterothermy

happens to all mammals in their appendages - poorly insulated, shunts heat to prevent heat loss

what does a high required metabolism rate (RMR) mean

rapid development and population growth. Costs include high energy requriments, depletion of reserves, reproductive costs

what does a low required metabolism rate (RMR) mean

better survival and parental care. Costs include reduced mobility, long development times, and lower reproductive rates.

what is countercurrent heat exchange

heat is exchanged between arteries and veins, minimizing heat loss in extremities.

what is rete mirabile (wonderful net)

complex network of veins and arteries that increase efficency in thermoregulation (ex. arms of sloths, brains of African antelopes)

what is daily torpor

Tb is lowered for part of the day, reduces food intake demands, lowers heat loss. Happens in many bats and rodents, “primitive” trait

what is estivation

a state of dormancy during hot or dry periods, conserves energy and water, common in small desert mammals

what is hibernation?

seasonal lowering of Tb in relation to cold temps and/or low food avalability. Two types - shallow and deep

what is shallow hibernation?

periods of sleep with moderate Tb reduction (ex. skunks, bears)

what is deep hibernation?

Tb drops within 2-3 degrees of Ta, some bats, ground squirrels, woodchuck

what are the main responses to high heat loads

behavioral thermoregulation, alter insulation, cyclic Tb, hyperthermia, evaporative cooling

what is hyperthermia (in mammology)

controlled increase in body temperature

what is hypothermia (in mammology)

controlled decrease in Tb

what does the vertebrae kidney do

excretes waste, aids in fluid balance. urine is excreted as hypertonic relative to blood

what is the loop of henle

concentrates urine, longer loop means more water retention (desert animals), small means less (beavers)

what is the passive countercurrent multiplying model of the mammilian kidney

In loop of henle - diffusion of NaCl out of ascending limb of LOP, flow of filterate is opposite in descending and ascending LOH, multiplier in increasing NaCl in inner medulla of kidney relative to outer medulla

what is the antiduretic hormone (ADH)

key hormone regulating kidney functino. ADH increases permability at end of distual tibule and collecting duct of LOH. this increase urine concentration (water is retained in body)

What is the relationship between ADH and hydration

as ADH decreases the distal tube and collecting duct permability is lowered causing urine to become unconcetrated (water expelled)

how do species in arid envionments conserve water

consume wet food, hyperthermia (ie reduce evaporation, fewer sweat glands, reduce respiration rate), drink water, water independence (metabolic water reduces need to drink (ex. kangaroo rats)

how does lactation impact water retention

huge seasonal loss, must recycle as much h2o as possible, drink frequently

what is the overall mammalian reproductive strategy

relativley few young, nourish young with milk, young remain with mother until weaned (sometimes even past that)

what is the first thing the ovarian cycle is influenced by

follicle stimulating hormone (FSH) and luteinizing hormone (LH) secreated by pituitary. Follicle growth triggers ovary to secrete estrogen

what is the second thing the ovarian cycle is influenced by

estrogen secretion feeds back to hypothalamus - pituitary, more LH and less FSH - ovulation and corpus luteum formation which secretes progesterone for uterine wall preperation

what is the third thing the ovarian cucle is influenced by

no fertilization causes the corpus luteum to recede to corpus albicans, progesterone and estrogen levels drop, ovi cycle begins again

what happens if fertilization occurs

corpus luteum continues to produce progesterone to maintain pregnancy, placenta soon assumes estrogen and progesterone secretion

what is the yolk sac

part of the primitive intestine lying external to embryo. forms endotherm (vestigal - no nutritional value)

what is the amnion

forms ectoderm and mesoderm, fills with serous fluid to prevent dessication/shock

what is the allantois

out-pocket from hindgut of embryo, movment of nutrients and oxygen , forms blood vessels of placenta

what is the chorion

outer embryonic layer, envelops entine assembalge-villi, contact with uterine wall

what makes up the placenta

includes embryonic membranes and lining of uterine wall

what are the four parts of the embryonic membrance

yolk sac, amnion, allantois, chorion

what are the four types of placentas based on villi on chorion

diffuse, polycotyledonary, zonary, discoidal

what is the diffuse placenta

villi scattered over entire surface of chorion, increases surface area

what is the polycotyledonary placenta

islands of villi scattered over chorion

what is a zonary placenta

band of villi encircle center of blastocyst, lacks villi elsewhere

what is the discoidal placenta

regional restriction of villi (most mammals)

what are the two types of placenta based on villi and endometrium

nondeciduate and deciduate

what is the nondeciduate placenta

loose fitting of villi with endometrium → villi pull free without disrupting endometrium

whatis the deciduate placenta

close fitting of villi-endometrium, villi pull free and cause erosion of endometrium,