M5, C15 Homeostasis Flashcards
define thermoregulation
the maintenance of a relatively constant internal temperature
why is thermoregulation important
if it’s too hot - proteins and enzymes will denature
if it’s too cold - proteins function very slowly
define ectotherms
give examples
animals that use their surroundings to warm their bodies
eg. reptiles, fish, amphibians
define endotherms
give examples
animals that rely on their metabolic processes to warm their bodies
eg. mammals and birds
what are the 2 responses ectotherms do to regulate their temperature
behavioral (body position, borrowing, body shape)
physiological (internal changes and changes to chemical reactions)
what behavioral responses can ectotherms do in order to maintain their body temperatures
These responses increase or reduce the radiation the animals absorb from the sun.
To warm up: basking in the sun and orientating their bodies to maximise surface area exposed to the sun and can extend areas of the body. Conduction - pressing their bodies against warm surfaces. Contracting muscles and vibrating to increase cellular metabolism.
To cool down: sheltering from sun in shade or in cracks of rocks or burrows. Pressing bodies against cool surfaces, water or mud. Orientating body so minimum SA exposed to the sun. Minimise movement to reduce metabolic heat generated.
what physiological responses can ectotherms do in order to maintain their body temperature
Changing colour - darker colours absorb more radiation from sun in order to warm up
Altering heart rate to increase or decrease the metabolic rate to affect warming or cooling across body surfaces
in endotherms, when there’s a change in temperature what happens between the detection and the response
1) Change in skin temperature monitored by peripheral thermoreceptors in skin.
2) Impulse sent to hypothalamus via sensory neurone.
3) Change in blood temperature detected by thermoreceptors in the hypothalamus.
4) Heat loss or heat gain centre of hypothalamus activated.
5) Impulse sent along motor neurone to effectors
how do endotherms respond when they become too hot
- Hypothalamus detects the change from thermoreceptors and sends impulse along motor neurone
- VASODILATION - Arterioles near surface of skin dilate and the shunt vessels constrict. Forces more blood through the capillary networks close to surface of skin which increases radiation of heat from skin.
- Sweat glands secrete more sweat. This spreads out across the surface of the skin. As sweat evaporates, heat is lost, cooling the blood below the surface.
- Erector pili muscles in the skin relax so hairs/feathers on the skin lie flat. There’s less insulation as air isn’t trapped
How do endotherms respond when they become too cold
- Hypothalamus detects the change from thermoreceptors and sends impulse along motor neurone.
- Arterioles near surface of skin constrict and shunt vessels dilate so little blood flows through capillary networks close to skin surface. Skin looks pale, little radiation takes place.
- Sweat glands secrete less sweat. Reducing the cooling effect the evaporation of sweat has.
- Erector pili muscles contract pulling hair/feathers upwards. More air is trapped to form insulating layer.
- Body shivers - rapid, involuntary contracting and relaxing of muscles in body. The metabolic heat from exothermic reactions warm up the body instead of moving it.
what is homeostasis
the body maintains a dynamic equilibrium with small fluctuations over a narrow range of conditions
what are the main metabolic waste products in mammals and where are they excreted
- carbon dioxide (excreted from lungs)
- bile pigments (formed from breakdown of haemoglobin from RBC in liver. excreted in bile from liver to small intestine via gall bladder and bile duct)
- nitrogenous waste products (breakdown of excess amino acids in liver)
where does the liver get its blood supply
-oxygenated blood is supplied to the liver by the hepatic artery and removed and returned to the heart in the hepatic vein
-the hepatic portal vein also carries blood to the liver loaded with products of digestion straight from intestines.
Mixed in sinusoids increasing the oxygen content of the blood from the hepatic portal vein
what is the structure of the liver
- liver cells (hepatocytes) have large nuclei, prominent Golgi apparatus and lots of mitochondria
- spaces called sinusoids supply the blood which increases oxygen content
- Kupffer cells contain phagocytes which ingest foreign particles to protect against disease
- spaces called canaliculi where bile is secreted into to drain into the gall bladder
Name 4 main functions of the liver
1) carb metabolism
2) deaminqtion of excess amino acids
3) detoxification
one of the liver’s functions is deamination of excess amino acids
what is this
removal of an amine group from a molecule
it’s released by the ornithine cycle as a nitrogenous waste product
the remainder of the amino acid is fed into cellular respiration or converted into lipids
one of the liver’s functions is detoxification
what does this involve
substances are detoxified and made harmless
eg. ethanol in alcohols which are converted to fatty acids or used in respiration
eg. hydrogen peroxide converted to oxygen and water by catalase
define excretion
the removal of metabolic waste from the body
metabolic waste is a combination of substances produced by chemical reactions of the cell which are toxic
Fill in the gaps for the ornithine cycle (producing urea)
Ornithine + Ammonia + 1 -> _2__ + citrulline
Citrulline + __3__ -> water + arginine
Arginine + __4__ -> ___5__ + ornithine
1) carbon dioxide
2) water
3) ammonia
4) water
5) urea
how could you differentiate between the hepatic vein, hepatic artery and hepatic portal vein by what they look like on a diagram
hepatic vein - vessel that takes blood away
hepatic artery - narrow vessel which blood enters liver through
hepatic portal vein - branched vessels where blood enters liver from gut
what are the 2 main functions of the kidney
Excretion of urea in the form of urine
Osmoregulation - maintains the correct water potential of the blood
what are the 3 layers of the kidney
outer = cortex middle = medulla inner = renal vein / renal artery and ureter
name all the parts the blood passes through when travelling through the kidney
renal artery afferent arteriole glomerular capillary bowman's capsule proximial convoluted tubule loop of Henle peritubular capillaries distal convoluted tubule collecting duct
define ultrafiltration
the removal of small molecules from the blood into the lumen of the Bowman’s capsule
- Efferent abs afferent arteriole
- filtration basement memebrane
what are nephrons
the long tubules in kidneys along with the bundle of capillaries where the blood is filtered
(they’re where all the 4 stages of urine production happen)
why does ultrafiltration happen? (pressure)
Blood is taken into the Bowman’s capsule by the afferent arteriole and this is wider than the efferent arteriole which takes the blood away.
So this causes a high hydrostatic pressure inside the glomerulus which forces liquid and small molecules into the Bowman’s capsule from the capillary.
What layers do the small molecules pass through in ultrafiltration?
endothelium of the capillary - small molecules pass through the gaps/pores of this
basement membrane (mesh of collagen and protein fibres)
epithelium of Bowman’s capsule - molecules have to get through the podocytes
where does the selective reabsorption happen in the kidneys
proximial convoluted tubule
loop of Henle
distal convoluted tubule
