Exam 2 Flashcards
Mammalian endothermy results from
High metabolic heat production, insulation
Body size role
As body mass increases, total metabolic rate increases. As body mass increases, mass specific metabolic rate decreases.
BMR
Basal Metabolic Rate, energy used as body preforms basic metabolic functions. Measured as oxygen use over time. Also known as resting metabolic rate.
MSMR
Mass Specific Metabolic Rate, amount of energy used for basic metabolic function per each gram of tissue, BMR/ body weight
Why does MSMR show a negative slope as body mass increases?
All about surface area to volume ratio. Small mammals have a large SA:V and large mammals have a small SA:V. Large mammals have ‘thermal inertia’ due to small SA:V. Small mammals see rapid heat loss to the environment due to a large SA:V.
Role temperature has on metabolic rate
Each mammalian taxa has a range of Tb where no additional energy is expended on temp regulation the TNZ (Thermal Neutral Zone). Mammals can vary their thermal conductance (C) in an energetically inexpensive way to maintain Tb within TNZ.
How do mammals vary C?
Fluffing fur, posture shifts, timing of activity
Interpreting Scholander Diagrams
Range of TNZ, contrast the position of LCT and UCT, interpret the slope of the line below and above the TNZ.
Body size (Maintaining)
A large body size favors heat conservation and a small body size favors heat dissipation.
Bergman’s Rule
Colder climates should support large mammals and warmer climates should support smaller mammals. “Races” from colder climates tend to be larger than “races” of the same species living in a warmer climate.
Allen’s Rule
Mammals in colder climates will have smaller external appendages to reduce surface area and in turn reduce heat loss.
Insulation
Lowers thermal conductance (C) by reducing heat loss from body surface. Thickness, color and density of fur all play a role.
Blubber
In cetacea and pinnipods, up to 50% of animal body mass may be in the form of blubber. Does not compress under pressure, allows for a smooth surface.
Behavioral Thermoregulation
Energetically inexpensive ways of expending the TNZ and manipulating C. Curling up, nest building, group thermoregulation, finding favorable microclimate.
Regional heterothermy
RH = allowing certain parts of the body to become much cooler, particularly the extremities where SA:V ratio is high.
Mechanisms for regional heterothermy
- Vasoconstriction (blood shunt), a transverse blood vessel detours blood from entering close to the skin, heat is conserved rather than lost to the environment. 2. Counter current exchange, arterial blood is warm and venous blood is substantially cooler. Arterial blood passes next to venous blood returning from extremities, arterial blood gives up heat to venous blood.
Consequences of counter current exchange
arterial blood is pre-cooled and venous blood is pre-warmed therefore reducing the potential for heat loss and regulation.
Increasing metabolic heat production
- Elevating metabolic capacity of skeletal muscles, shivering and locomotion, requires energy investment. 2. metabolize brown fat
Brown fat vs white fat
Numerous small fat vacuoles, glycogen present in cell to fuel mitochondria, eutheria only, production of heat 10x skeletal contractions. LOTS of mitochondria.
Adaptive hyperthermia
A continuum of responses that allows energy to be saved by temporarily abandoning homeothermy on a circadian or seasonal basis.
Shallow hyperthermia
period of inactivity, Tb drops but is regulated within 10 degrees (c) of normal, sometimes called “daily torpor”
Profound hyperthermia
Torpor or hibernation, Tb approaches Ta, oxygen consumption is reduced and aprea occurs
Torpor
Stimuli: variable on species, may be lack of resources or temp but typically is photoperiod. Preparation: increase feeding and energy storage, particularly in terms of fat intake. Entrance: decrease in heart rate, metabolic, oxygen uptake and body temp. Other: periodic arousal, bouts increase in duration and length then decrease as spring apporaoches.
Strategies to get water
Periodic drinker: drink large amounts of water when available. Dietary moisture: obtaining water via food. Metabolic water: water formed as a byproduct of the oxidation of energy containing substances in food.
Strategies to conserve water
Concentration of feces and urine: increases water retention via long loop of Henle. Concentration of milk: production of highly concentrated milk, reclamation of water lost in lactation by consuming urine and feces of young.
Strategies for maintaining a thermodynamic equilibrium in a xeric environment
- Behavioral thermoregulation: avoid extreme heat and finding a suitable microhabitat and adhering to defined periods of activity. 2. Evaporative cooling: the major mechanism employed by mammals to decrease Tb, panting and sweating. 3. Adaptive hyperthermia: tolerating high Tb to as a way to conserve energy and water. 4. Dormancy: passing through unfavorably warm periods by becoming dormant, torpor- dormancy in the cold, estivation- dormancy during hot or dry (rare in mammals, dwarf lemur, east African hedgehog)
Sweating vs panting
Sweating: convection may be limited in certain situations, results in loss of electrolytes, passive. Panting: Animal provides own airflow, minimal loss of salt, active muscle contraction.
Hyperthermia
Advantage: water saving strategy. Disadvantage: mammalian brain fries at temps 4-5 C above resting temp. To survive desert mammals have evolved circulatory systems to cool the brain (counter current exchange).
Reproduction is…
Characterized by a series of cyclic events controlled by the endocrine system, maintained by environmental and social cues that affect the endocrine system and its secretions.
Nervous system
Wired system, neurotransmitters travel short distances across nerves, response is rapid and brief, coordinates rapid and precise responses.
Endocrine system
wireless system, hormones released into blood, travel long distances to target cells, response may be rapid, but is typically slow and long lasting, controls activities of long duration.
Endocrine system 2
The chemical communication system that controls physiological processes. Controlled by the hypothalmus. Chemical communicators (hormones) are secreted into the blood and act on a distant tissue, causing a change in the body. Endocrine tissue communicate with each other by secreting hormones in a series called an axis.
Ovarian cycle
Cycle of growth of the follicle within the ovary and the release of the egg.
Uterine cycle
cyclic changes to the condition of the uterus in preparation for fertilization and placenta formation.
Female reproductive anatomy
Ovaries- produce eggs and female reproductive hormones (estrogen and progesterone), uterine tubes- carry eggs to uterus, site of fertilization. Uterus- Thick muscular organ, incredible expandability, receives blastocysts, houses developing offspring and the placenta.
Layers of the uterus
- Perimetrium- outer layer, forms a broad ligament that attaches to the pelvis. 2. Myometrium- inner muscular layer, forms most of the uterus, capable of strong contractions and incredible expandability. 3. Endometrium- specialized mucus membrane that is highly vascularized for implementation of fertilized eggs.
Production and transport of the egg
The ovaries are filled with tiny vesicles called follicles, they are always present at various stages of development. Follicles serve two purposes (site of egg production, serve as endocrine tissue secreting estrogen and progesterone).
Primordial Follicles
Not yet growing, contain an immature egg called a primary oocyte
Primary Follicles
Growing follicle containing a developed egg called a secondary oocyte
Secondary follicle
Mature, ready to release egg (graafian follicle is next one on deck)
Follicles cont.
After ovulation the follicles becomes the corpus luteum and serves as temporary endocrine tissue, continuing to secrete estrogen and progesterone. When the endocrine role is complete the follicle shrivels up and becomes the corpus albicans. The egg is unable to move on its own, carried by peristaltic contraction and cilia. Fertilization occurs in upper part of the tube.
Hormonal control of female reproductive system
Development of the egg is controlled by cyclic production of hormones, starting at the hypothalamus. GnRH act on the anterior pituitary gland at the base of the brain. In response the pituitary gland secretes two hormones.
FSH
follicle stimulating hormone- stimulates the follicle to mature and produce an egg. As the follicle develops it becomes endocrine tissue and produces estrogen and progesterone.
Estrogen and progesterone stimulate
Development of secondary sex characteristics, development of endometrium layer in the uterus
LH
luteinizing hormone, causes rupture of the follicle and ovulation, stimulates development development of the corpus luteum. Corpus luteum continues to produce estrogen and progesterone, high levels of estrogen and progesterone maintain the endometrium layer. Inhibit the addition secretion of FSH and LH (Negative feedback loop)
Estrus Cycle 1-5
- Hypothalamus secretes GnRH, stimulating the anterior pituitary gland to secrete FSH. 2. FSH stimulates maturation of the follicle. 3. Follicular cells produce and secrete estrogen, which maintains secondary sex characteristics and stimulates the endometrium layer to thicken. 4. Elevated estrogen levels trigger the anterior pituitary gland to secrete a large pulse of LH which stimulates ovulation (positive feedback loop). 5. Follicular cells now become corpus luteum which continues to secrete estrogen and now also progesterone.
Estrus Cycle 6-10
- If egg is not fertilized, corpus luteum denatures, causing a decline in estrogen and progesterone. 7. Blood vesicles in the endometrium constrict and denature without the signal to stay in place. 8. Uterine lining sloughs off, producing menstural flow. 9. A pause ensues in the cycle, the duration of which is species dependent. 10. Anterior pituitary gland no longer inhibited by high levels of estrogen and progesterone secretes FSH and cycle is repeated.
Monoestrus vs polyestrus
Mono- estrus cycle occurs once a year. Poly- estrus cycle occurs on a regular schedule throughout the year.
Hormonal regulation of pregnancy
the endocrine system has prepared uterus for a developing embryo
Blastocysts
Outer wall- Trophoblast, Inner wall- Stem cells. Blastocyst makes contact with endometrium, triggering a round of trophoblastic cell proliferation. Trophoblast cells secrete enzymes to erode a hole in endometrium. Blastocyst implants into endometrium. A new series of physiological events is now set into motion following implantation. Trophoblast secretes the HCG (Human Chronic Gonadotropin) . HCG stops the corpus luteum from breaking down.
Reproductive hormones are produced…
Progressively by the placenta and less by the corpus luteum of the ovary. Placenta becomes the sole source of estrogen after 3rd month in human females, corpus luteum production declines, placental production commences. Placenta becomes independent endocrine gland. Placental lactogen- induces mammary gland. Relaxin- relaxation of pelvic ligaments and pubis symphysis.
Variation in reproductive anatomy
Prototheria- reproductive tract similar to reptiles, large ovaries, oocytes visible to naked eye, as fertilized egg moves down fallopian tube, layers of keratin are secreted forming a shell, eggs empty into cloaca. Metatheria- didelphis condition, two vaginas and two separate uteri.
Eutheria
One vagina, uterus is highly variable in architecture across eutherian taxa.
Uterine types in eutheria
- Duplex- 2 uteri, each with their own cervix (rodents and lagomorphs). 2. Biparite- 2 uteri, 1 cervix (whales and most carnivores). 3. Bicornate- 1 uterus separate medially forming horns, fused distally forming a common chamber (most common in ungulates, most primates, insectivores). 4. Simplex- all separation between uterine horns is lacking single uterus single cervix (higher primates)
The placenta
A complex of embryonic and maternal tissue that preforms several essential functions. 1. physically anchors fetus to uterus. 2. transports nutrients from the circulation of the mother to the circulation of the developing offspring. 3. Provides respiratory function, developing offspring can’t breathe while bathed in amniotic fluid.4. Exercises metabolites and waste from circulation of offspring to circulation of mother. 5. serves an endocrine function by producing hormones that regulate the organs in both mother and offspring.
Two types of placental connections
- Choriovitelline placenta- “yolk sac” placenta, formed by the fusion of the chorion and the yolk sac, yolk sac is primary source of nourishment, blastocyst does not sink deeply into endometrium, only shallow depression, connection is weak and short lived (25% of gestation), receives limited nourishment from the uterine lining in the form of uterine milk, embryo stores its own waste, metatherian placenta. 2. Chorioallantois placenta - true placenta, allantois is involved in placenta, not yolk sac, blastocyst sinks deeply into endometrium, high level of connectivity due to rapid growth of chorionic villi, increased surface area for exchange, uterus highly vascularized at point of villi penetration.
Eutherian Placenta
Unique vascular organ that contains two separate circulatory systems, maternal contributions- uteroplacental circulation, fetal contributions- fetoplacental circulation, maternal arteries and veins feed into the intervillous space, umbilical artery and veins penetrate and form a tree-like structure called cotyledon in the intervillous space, maternal and fetal blood do not mix, come into close contact across the placental membrane, diffusion across the membrane, including gasses, glucose, amino acids, nutrients, excretory metabolites, antibodies, etc…
Placenta +
Is endocrine tissue secreting the following, HCG- acts on the corpus luteum, estrogen and progesterone various estrogen type hormones to expand uterus, produce enlarged mammary glands, inhibit FSH.
Male reproduction is…
characterized by: rapid production of inexpensive sperm, maintained by: environmental and social cues that affect the endocrine system and its secretions.
Two important components of male reproductive biology are
spermatogenesis- the production of male gametes in the testis. Sperm delivery- the act of delivering gametes from the male reproductive organs to the female’s reproductive organs.
Male reproductive anatomy
Testis- center of male reproductive anatomy, produces sperm and male reproductive testosterone, numerous other gland and tubes that work together to deliver sperm to the female.
Lobules- tightly coiled packages of seminiferous tubules, lobules are essentially sperm factories, each testis contains 250 lobules.
Seminiferous tubules- the factory floor of sperm production.
Epididymis- the testis collection point for sperm produced in each lobule, long, tightly coiled, sperm mature and are stored here.
Vas Deferens- transport mature sperm from the epididymis to the ejaculatory ducts in preparation for ejaculation.
Sperm Production
Sertoli cells- large cells that nourish developing sperm, similar to the way the follicle cells support the egg.
Leydig cells- secrete testosterone, similar to the way corpus luteum secretes estrogen.
Spermatogonium- source cells for sperm, similar to “mother cells” or stem cells.
LH in males
Stimulates leydig cells to produce testosterone, stimulates production of sperm in high concentration, stimulates development of secondary sex characteristics (muscle and skeletal growth, aggression, increased sex drive, deeper voice, facial hair)
FSH in males
Stimulates spermatogenesis, act on the sertoli cells to begin facilitate sperm production, although the mechanism is not well understood.
Sertoli cells
produce androgen binding proteins (ABP), testosterone will bind with ABP to create high concentrations of testosterone in the tubules.
Creates…
“Testosterone bombs” target of the bombs are the outer cells of the seminiferous tubules- the spermatogonia.
Spermatogonium
Diploid mother cells (2n) that produce haploid daughter cells (sperm). First divide through mitosis (duplicate themselves)
one copy (Type A) stays put, ensuring always spermatogonium
other copy (Type B) goes through meiosis, producing two haploid gametes (spermatocytes) those gametes go through a second meiotic division, resulting in production of four gametes from one spermatogonium.
Seminal Vesicle
70% of sperm, an alkaline solution that helps to counteract the slightly acidic environment of the female reproductive organ, provides nourishment for sperm (fructose), secretes prostaglandins (chemicals that decrease the viscosity of the cervical fluid and trigger reverse peristalsis of the uterine tube)
Prostate Gland
Circles urethra below bladder, during ejaculation it contracts and adds an enzyme cocktail to the semen to keep it fluid (PSA- prostate specific antigen), adds an antioxidant called spermine that produces DNA
Bulbo
Urethral gland, secretes a clear mucus just before ejaculation, clears urethra of urine, may provide lubrication in some species, also known as “pre-ejaculatory fluid”, does not contain sperm
Male reproductive anatomy
Many mammals achieve erection through a bony structure: baculon.
Advantages:
-increased duration of intercourse
-allows for “shoe horning” in species with delayed fertilization
…
I give up
