9.9 Osmoregulation Flashcards
How many kidneys do we have?
Two
Where are the kidneys found?
Rear of the abdomen
Either side of the aorta
Explain the structure of a kidney
Outer layer is the cortex Inner is medulla Inside medulla is the pelvis Ureter leading off Renal artery and vein
What is the main function of the structures in the cortex?
Filtering toxins such as urea
What is the main function of the structures in the medulla?
Osmoregulation - regulating water potential
What is osmoregulation?
The regulation of the water potential of the body within narrow limits by controlling the concentration of water and salt
What are the main organs involved in osmoregulation?
Kidneys and liver
Where are amino acids deaminated?
In the liver
Explain how amino acids are deaminated?
Amino group removed
Converted to ammonia
Converted to urea
Why does ammonia need to be converted to urea?
Urea is non-toxic, ammonia is toxic
What are the two main functions of the kidney?
Waste filtration
Osmoregulation
What is the function of the ureter?
Carrying urine to the bladder
Where does ultrafiltration take place?
Glomerulus
in the cortex
What are the three layers which the filtrate goes through during ultrafiltration?
Endothelium
Basement membranes
Podocytes
Explain the process of ultrafiltration
High blood pressure in glomerulus
Forces blood through three stage filtration mechanism:
Fenestrations in the endothelium –> basement membrane –> gaps in the podocytes
Proteins and blood cells can’t pass through bc too big
What causes the high blood pressure in the glomerulus?
Afferent arteriole is wider than the efferent arteriole
What substances are found in the glomerular filtrate?
Glucose
Urea
Water
Where does selective reabsorption take place?
Proximal convoluted tubule
Where does the filtrate from the glomerulus go?
To the Bowman’s capsule
Name some of the adaptations of the PCT?
Brush border of microvilli - increases surface area for reabsorption
Mitochondria - ATP for active transport
PCT is one cell thick - short diffusion distance
Close to capillaries - conc gradient and short diffusion distance
Explain the process of selective reabsorption in the PCT
Na+ actively pumped out of PCT wall into the blood using ATP
Na+ and glucose co-transported into the PCT wall from PCT lumen by facilitated diffusion down conc gradient with protein carrier
Na+ and glucose levels build up - move into blood by diffusion
Increases water potential of the PCT wall - water leaves
What is reabsorbed by the body during selective reabsorption?
All of the glucose and amino acids
Some water
Explain how the loop of Henle works
Ascending and descending limb
Asc. impermeable to water
Na+ and Cl- actively removed from ascending
Lowers water potential in the medullary region
Longer loop of Henle - lower water potential
Water moves out of descending limb by osmosis
Some Na+ diffuses into descending limb
Vasa recta acts as a counter current multiplier
What does a counter current multiplier do?
Maintains the low water potential in the medullary region
Allows water to be reabsorbed
Stops water being lost through urine
What is the advantage of a long loop of Henle?
Long loop of Henle means larger osmotic gradient. More ions actively transported out of ascending limb
Water potential of medullary region more negative
More water leaves descending limb by osmosis
What is ADH?
Anti-diuretic hormone
What does ADH do?
Makes the collecting duct more permeable to water
More water reabsorbed
Urine is more concentrated
Where is ADH produced and stored?
Produced in hypothalamus
Stored in the PPG
Explain the mechanism of ADH
ADH binds to membrane receptors
Triggers cAMP
Series of reaction
Vesicles of aquaporins fuse with membrane
Aquaporins inserted - membrane more permeable
What is diabetes insipidus?
ADH isn’t produced
Urine v dilute - water isn’t reabsorbed
Person feels v thirsty
What areas of the kidney does ADH affect?
The distal convoluted tubule
Collecting duct
What is the role of the distal convoluted tubule?
Controls blood pH
Controls levels of sodium and potassium ions
Controls water levels - ADH
What is the role of the collecting duct?
Most osmoregulation takes place here
Transports urine to pelvis of the kidney
How do desert animals like kangaroo rats get the water they need?
Water from cellular respiration
Condensation reactions which take place in the body
Water in food
How is low water potential detected by the body?
Osmoreceptors in the hypothalamus
How does the body respond to low water potential of the blood?
Osmoreceptors in the hypothalamus detect change
ADH secreted by PPG
ADH makes DCT and collecting duct more permeable
More water reabsorbed
How is diabetes insipidus treated?
Drugs given to replace ADH
Drugs given to make kidney produce more concentrated urine
Why is thermoregulation important?
Enzyme controlled reactions in the body only happen in a narrow region of temperatures
Which organisms don’t need to control body temperature?
Proctotista
Organisms living in the sea - stable temperature bc high specific heat capacity of water
What is an endotherm?
An organism which relies on its own metabolic processes for heat. Has a temperature higher than ambient temperature
What is an ectotherm?
An organism which relies on the environmental temperature for heat
What is an advantage of endotherms?
They can survive in a wide number of environements with different temperatures
How do ectotherms regulate body temperature?
Behavioural and anatomical adaptations
What is the largest organ involved in thermoregulation?
The skin
Explain the ways in which endotherms can stay cool
Arteriovenous shunt - vasodilation increases heat loss by radiation
Erector pilli are relaxed - hairs lie flat
Sweat production increases - increased evaporation
Little subcuntaneous fat - less insulation so more heat loss
How is the arteriovenous shunt used in thermoregulation?
Closes when organisms gets hot - more blood flow through capillaries near the surface so more heat loss via vasodilation
Opens when organisms get cool - blood doesnt flow through capillaries so less heat loss
How do endotherms stay warm?
Arteriovenous shunt opens - vasoconstriction
Little sweat produced
Erector pilli contract - hairs stand up so air gets trapped
Metabolic rate of body speeds up
Thick layers of fat produced
Explain the role of superficial blood vessels in keeping an animal warm
Vasodilation
Muscles around arterioles to superficial capillaries relax - allow for more blood flow to surface
Less blood to deeper shunt vessels
More cooling by conduction and radiation
Explain the role of superficial blood vessels in keeping an animal warm
Vasoconstriction
Shunt opens - less blood to capillaries at the surface
Arterioles contract - less blood flow to capillaries and more too deeper vessels
Less heat loss by conduction and radiation bc smaller temp gradient
What are the two receptors involved in thermoregulation?
Receptors in the brain
Receptors near the surface of the skin
What do thermoregulatory receptors in the brain detect?
Changes in the temperature of the blood
What do thermoregulatory receptors in the skin detect?
Temperature of the environment
Where do thermoregulatory receptors send impulses?
To the thermoregulatory centre in the hypothalamus
Explain how thermoregulation in an endotherm works (briefly)
Change in temperature Detected by receptors Signals sent to thermoregulatory centre in hypothalamus Effectors do their thang Return to norm
What are physical characteristics of animals which prevent heat loss?
Small surface area to volume ratio
Small extremities - such as ears
Counter current echange systems
Fat
How does hibernation help survival of animals?
Eat more than usual to store fat - energy store and insulation
Metabolic rate slows right down
Core body temp lowered
Why do animals go into hibernation?
Short day length
Low temperatures
What are behaviours that animals can use to regulate temperature?
Basking in the sun - warms them up
Sheltering - cools down
Evaporation - panting or wallowing in water
Moving in or out of the sun
