9.9 Flashcards
what is an endotherm?
an organism - can use internal sources of heat to maintain body temp - independent of external temp
how do endotherms control body temp?
- they can generate heat internally - control their body temp within fairly narrow limps
how do ectotherms control body temp?
- metabolism cant be increased to raise body temp - rely on external heat sources to raise temp - so activity and body temp varies w external temp
why do ectotherms have an adv compared to endotherms
- for eco: more energy for growth as its not diverted into heat generation
- for ends: burning carbs + lipids to raise body temp and keep it constant = less available for growth
to maintain constant core body temp, endotherms must balance..
energy gains (inputs) + loss (output)
how is energy gained
- endothermic/heat producing reactions like respiration
- aspiration of radiation from warmer bodues
- adsborotin by condution
how is energy lost?
- radiation + condition to cooler surroundings
- convection + evaporation
if core temp is high, response is to… by…
increase heat loss
hairs flat = insulating Layer of air not trapped, vasodilation = blood close to surface so heat easily lost by radiation, sweating, panting = evaporative cooling from resp system
- seek shade, move less (generate less internal heat)
if core temp is low, response is to… by…
reduce heat loss
pili-erection, vasoconstriction (blood not close to surface - less heat loss), less sweat , increase heat production: involuntary muscle contraction (generate more internal heat), liver more active (increased metabolism), shivering
how is body temp controlled In humans
hypothalamus - thermoregulatory centre (TRC)
- monitors core + peripheral temp
- thermoreceptors in hypothalamus monitor temp of blood in brain
- thermoreceptors in skin = monitor peripheral body temp - give early warning of change
how do ectotherms manage their body temp> what are most ectotherms
- all animals except mammals + birds r ectotherms
- dont produce large amounts of heat energy internally - must obtain most from environment - so less active when cold (early/late in day)
how do ectotherms gain heat + lose heat
gain:
- radiation from sub/warm objects like rocks
- conduction from warm surfaces like rocks warmed by sun
- convection eg warm winds
loss
- radiation from warm body -> cooler suuroundings
- convection of cool winds
- conduction to ground that is cooler than body temp
what do ectotherms do in high temp
physiological:
increased breathing movements - increased evaporative cooling
increased mucus secretion from skin- increased evaporative cooling
behavioural:
- shaded areas
- dive into warm water
ectotherms in low temp..
physiological:
- contract flight muscles before take off - heat generation warms muscles up
- direct blood away from skin - prevents unnecessary cooling
behavioural
- expose body to sun/warm surfaces
why do ectotherms put on more growth than endotherms when given same amount of food?
- less food used to generate heat to maintain body temp so more available for growth
structure of kidney
check diagram.
renal vein + artery at top going into both kidneys, two kidneys on side, ureter -> bldder, sphincter/ring muscles, urethra which removes urine from bladder
renal vein function
returns filtered blood to circulation - vena cava
renal artery function
takes blood to kidney for filtration; branches off aorta
ureter function
takes urine to bladder for temporary storage
bladder function
urine is stored until convenient
sphincter/ring muscles
relaxes during urination
gross structure of kidney
- kidney tissue = deep dark red
- covered in CAPSULE, made up of THREE main areas:
1. an outer cortex = blood filtered in renal capsule, sugars, AA, useful nutrient reabsorbed in convoluted tubules
2. inner medulla (paler) = concentrates salt to create water potential gradient needed to reabsorb water
3. pelvis = connect to ureter
function of kidney nephron
- 10000s of them
- blood is filtered (Wastes removed), useful substances reabsorbed, conc of blood controlled
- capillaries made of squamous endothelium
transamination?
transfer of an amine group from an amino acid to a keto acid (amino acid without an amine group)
Keto acids and/or carbon skeletons are what remains after an amino acids have had their nitrogen group removed by deamination or transamination. Transamination is used to synthesize nonessential amino acids.
functions of liver
- regulation of blood sugar
- production of + regulation of lipid
- transamination to produce non-essential AAs
- deamination
- detoxification of alc + drugs
- breakdown of hormones
what is urea
excretory product formed from the breakdown of excess amino acids (from excess protein)
Excess amino acids cannot be stored in the body
– have about the same energy as carbohydrates
– extremely wasteful if they were excreted
what happens to excess AAs instead of excretion/storage
they are deaminated by the liver
– amino group is removed to produce ammonia -> changed to urea then excreted
– The rest of the amino acid forms a keto acid which can be respired to release energy or converted to fat to be stored
why is ammonia converted to urea
- Ammonia is very soluble and very toxic, so it cannot be allowed to remain in the body
- Urea is less toxic and much less soluble
- Urea is released into the blood, and dissolves in the
plasma - Urea is removed from the blood in the kidneys
what is the ornithine cycle
The process in which ammonia is converted to urea
* It occurs partly in the cytosol and partly in the mitochondria , as ATP is used
- Aquatic organisms such as fish do not convert the ammonia produced by deamination into urea, but simply excrete it as ammonia into their environment
a) Explain why it is possible for them to do this, whereas terrestrial animals cannot
b) Suggest the advantages to aquatic animals of excreting ammonia rather than urea
a/ ammonia will quickly dissolve in large volumes of water around them and be so diluted that it won’t harm the fish
b) turning ammonia -> urea requires energy in form of ATP, so by excreting ammonia rather than urea energy is saved
where does ultrafiltration happen
- renal capsule
how is blood in glomelura capillaries separated from lumen of renal capsule
- by endothelium cells of blood capillary - many small pores so plasma can diffuse out
- basement membrane
- layer of cells = podocytes - make up lining of renal capsule
structure of podocytes
= many projecting fingers - wrap themselves closely around capillary loops of glomerulus
- tiny slits left bw interlocking podocyte fingers
process of ultrafiltration
- The diameter of the afferent arteriole that brings blood to the glomerulus is greater than the diameter of the efferent arteriole
- This results in a build up of hydrostatic pressure inside the glomerular capillaries
- The pressure is higher in the glomerulus than in the Bowman’s capsule
- As a result, blood plasma (water and relatively small molecules of the blood, including useful ions, glucose, amino acids) is forced out through the pores in the capillaries, through the basement membrane and then through slits between the podocytes. The fluid that seeps through is known as glomerular filtrate
what is filtered in ultrafiltration, do we want to remove it or keep it?
- water KEEP
- glucose KEEP
- inorganic ions (k+, cl-, Na+) KEEP
- amino acids KEEP
- urea LEAVE
what is selective reabsorption, and how is it adapted to achieve reabsorption
The filtrate contains many substances that the body should keep – glucose, amino acids, salts, water - Selective reabsorption takes these wanted substances back into the blood
* Blood capillaries lie very closely against the outer surface of the tubule – the blood in these has come directly from the glomerulus, so it has much less plasma in it than usual
* The cuboidal cells lining the PCT are specialised to achieve reabsorption:
1. Cell surface membrane (basal membrane) in contact with the tubule fluid is
highly folded to form microvilli; ↑ surface area (also called a brush border)
2. Membranes contain co-transporter proteins that transport glucose or amino acids, in association with sodium ions, from the tubule into the cell (facilitated diffusion)
3. The opposite membrane is also folded (↑ surface area). It also contains sodium-potassium pumps that actively pump Na+ ions out of the cell into the blood and potassium ions into the cell
4. Cells have many mitochondria – production of ATP for active transport
where does selective reabsorption happen
proximal convoluted tubule,
selective reabsorption process
Membranes contain co-transporter proteins that transport glucose or
amino acids, in association with sodium ions, from the tubule into the cell
(facilitated diffusion)
The opposite membrane (nearest the capillary) is also folded (↑ surface
area)
It also contains sodium-potassium pumps that actively pump Na+ ions out
of the cell into the blood and potassium ions into the cell. This…
Lowers the concentration of Na+ ions in the cell
Sets up a concentration gradient
Na+ ions then move from the filtrate into the tubule cells
Na+ ions move down their concentration gradient
Use carriers that also co-transport other molecules (glucose and amino acids)
As the glucose and amino acid concentrations rise inside the cell, these
substances are able to diffuse out of the cell into the tissue fluid, then diffuse
into the blood where they are carried away
Whilst the movement of Na+ ions and glucose from the nephron lumen
into the cell does not use energy directly, it only happens because energy
was used to pump Na+ ions out of the cell initially
Consequently, transport of glucose and the other substances from the
lumen of the nephron is an example of secondary active transport
how are larger molecules like small proteins reabsorbed
endocytosis
