Homeostasis And Hormones Flashcards
Release of a second messenger what type
Non steroid hormones
- adrenaline
Insulin
Glucagon
ADH
Hydrophilic so cannot pass through the lipid bilayer
Release of a second messenger process
1) hormones molecules bind to a receptor in the cell membrane
2)once bound, it causes a change in shape to the enzyme adenyl cyclase which activate it . Hormones activate an enzyme inside the membrane
3) activated adenyl cyclase convert ATP to cyclic AMP (cAMP) -second messenger
4) cAMP catalyse/activate inactive protein kinase to active protein kinase
-cAMP binds to other chemicals which pass into the nucleus and act as DNA transcription factor —> changes on cause a no. Of response
Role of adrenaline (second messenger model)
If blood glucose is too Low the adrenal gland will also secrete adrenaline
1) adrenaline attaches to receptor on the surface of target cells. This cause a protein (G protein) to. Be activated and to convert ATP into cAMP
2) cAMP activates an enzyme that can hydrolysis glycogen into glucose
3)this is known as the second messenger model of adrenaline and glugagon action, because the process results information of cAMP, which acts as a second messenger
Hormones enter the cell what substance can pass
Lipid soluble can pass through the lipid bilayer
Oestrogen and testosterone
Hormones enter the cell process
1) steroid hormones ( oestrogen and testosterone) are lipid soluble
2)they can pass through the membrane and act as the internal messenger themselves
3) inside the cell, hormones bind to a receptor and the hormones-receptor complex passes through the pores of the nuclear membrane into the nucleus
4) the hormones attaches to the receptor act as a DNA transcription factor / regulating gene expression and switching sections of the RNA on or off
What does liver break down
Excess amino acid
Deamination
Amino acid —> keto acid + ammonia
Removing NH3, -2
.
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What are the 3 Main function of the kidney
Ultrafiltration
Selective reabsorption
Tubular secretion
What is the malpighian body
Glomerulus and the bowman capsule
What occurs during the ultrafiltration
The diameter of the afferent arteriole is bigger than the diameter of the efferent capillary
This causes high pressure forcing small molecules such as glucose, urea, amino acids, water salts from blood through the pores in the walls of the capillary
Large molecules such as blood cells and plasmas protein are large and so don’t enter the nephron
A layer called the basement membrane act as a filter —> act as a filter to prevent large molecules entering the nephron
Define selective reabsorption
The process by which substance needed by the body are reabsorbed from the kidney tubules back into the blood
What adaptation does microvilli provide in selective reabsorption
Provide a large surface area for reabsorption
What adaptation does mitochondria provide in selective reabsorption
Produce ATP for active transport
What makes up glomerulus filtrate
Glucose urea and salt and water, amino acid and inorganic ions
Selective reabsorption process
1) the concentration of sodium ion in the PCT cell is decrease as the sodium ion are actively transport out of the PCT cells into the blood in the capillaries
2) due to didnt, sodium ions diffuse down the gradient from the lumen of the PCT into the cell lining the PCT
—> co transport as the protein which transport the sodium ions in carry glucose with it
3)the glucose can then diffuse from the PCT epithelial cell into the blood stream
4) this is how all the glucose is reabsorbed
Loop of henle role
Sodium ion gradient to enable reabsorption of water is maintained in the medulla
Loop of henle process
1) mitochondria in the walls of the cells provide energy to actively transport sodium ions out of the ascending limb of the loop of henle
2) the accumulation of sodium ions in outside of the nephron in the medulla lowers the water potential
3therefore water diffuse out by osmosis into the interstitial space and then the blood capillaries (water is reababsorbed into the blood)
4) at the base of the ascending limb some sodium ions are transported about by diffusion as there is now a very dilute solution due to all water that has moved out
Loop of henle descending limb
As the fluid in the tubule descend into the medulla in the descending loop the water potential becomes love r (more negative)
1) the wall of the descending limb being permeable to water so that water leaves by osmosis into the surrounding tissue fluid
2) sodium and chloride ions diffuse into the tubule from surrounding tissue fluid
Loop of Henley - ascending limb
As the fluid in the tubule then moves through the ascending limb towards the cortex the water potential becomes higher (less negative)
- sodium and chloride ions diffusing out of the tubules into the tissue fluid at the base of the loop
-higher up the tubules, sodium and chloride ion are actively transported out into the tissue fluid
-the walls of the ascending limb are impermeable to water so it cannot leave the tubule
The distal convoluted tubule role
From the top of the ascending Limb, the tubule fluid passes through the distal convoluted tubule
The DCT is permeable to water but this varies depending on the concentration of the hormones ADH
Here active transport adjust the concentration of various salts in the tubule as sodium and chloride ions can be reabsorbed here if needed
More ADH
Cells in the wall of the collecting duct have membrane bound receptor for ADH
The ADH binds to the receptor abuses a chain enzyme controlled reaction inside the cell forming a second chemical messenger (cAMP is formed from ATP)
cAMP causes vesicles within the cells of the tube linings to move and fuse with the cell membrane
The vesicles contain water permeable channels (aquaporins) which are inserted into the cell surface membrane
This makes the walls more permeable to water
More ADH in the blood means more aquaporins are inserted allowing more water to be reabsorbed and less allowing more water to be reabsorbed and less more concentrated urine with a lower water potential
Explain the role of the loop of henle in the absorption of water from the filtrate
1) in the ascending limb sodium ions actively removed as the walls of the ascending limb are impermeable to water so it cannot leave
2)the descending limb being permeable to water so that water leaves by osmosis into the surrounding tissue fluid as the sodium and chloride ions diffuse into the tubules from the surrounding tissue fluid
3) the longer the loop/deeper the medulla
Water leaves the DCT by osmosis down the water potential gradient
Role of Osmoreceptor
In hypothalamus monitor the blood water potential
Too much water
Osmoreceptor at the hypothalamus detect high water potential in the blood and then send nerve impulses to the pituitary gland
Less ADH is secreted by pituitary gland
ADH travels through blood and reach the collecting duct
ADH travel through blood and erach the collecting duct
Less permeability of collecting duct
Less water reabsorption
More volume of urine (less conc urine)
Too little water
Osmoreceptor at the hypothalamus detect lower water potential in the blood and the impulse to the pituitary gland
More ADH is secreted by pituitary gland
ADH travel through the blood to the collecting duct
More ADH makes more permeable of the collecting duct
More water reabsorption
Less volume of urine(more conc of urine)
Describes how ADH increases permeability of the distal tubules and the collecting duct to water
ADH cannot cross the membrane of the tubule cells. It binds to specific receptors, triggering reactions that result in the formation of cAMP as the second messenger.
This triggers the vesicles containing water channels in the cells lining the tubules to move to, and fuse with, the cell membranes.
The water channels are inserted into the membrane, making it permeable to water so water can move through the channels out of the tubules and into the surrounding blood capillaries by osmosis.
When the ADH falls
The levels of cAMP drops and the water channels are taken out of the membrane and repackaged in vesicles. This makes the tubule impermeable to water again. The channels are stored in vesicle ready for reuse when they are needed again
Explain how ADH control the volume and conc of increase in blood plasma
An increasing plasma concentration is detected by osmoreceptors in the hypothalamus. They send nerve impulses to the posterior pituitary, which in turn releases stored ADH into the blood. The ADH is picked up by receptors in the cells of the kidney tubules. ADH increases the permeability of the distal tubule and the collecting duct to water. As a result, water leaves the tubules by osmosis into the surrounding capillary network. This means more water is returned from the filtrate to the blood plasma, and a small volume of concentrated urine is produced.
Explain how ADH control the volume and conc of decrease in blood plasma
If the blood plasma becomes more dilute, the change is detected by the same osmoreceptors of the hypothalamus. When the concentration of the blood plasma falls, it inhibits the release of ADH by the pituitary gland. The walls of the distal tubule and the collecting duct remain impermeable to water and so little or no reabsorption
takes place. Large amounts of very dilute urine are produced and the concentration of the blood is maintained.
How ADH control of volume
These changes are detected by the baroreceptors in the aortic and carotid arteries. A rise in blood pressure is often a sign of an increase in blood volume. It will suppress the release of ADH and so increase the volume of water lost in the urine. This, in turn, reduces the blood volume and so the blood pressure falls. A fall in blood pressure, which may indicate a loss of blood volume, causes an increase in the release of ADH from the pituitary and the conservation of water by the kidneys. Water is returned to the blood and a small amount of concentrated urine is produced.
How does the body know if we are too hot or too cold
Temperature receptor in the hypothalamus detect the temperature of the blood
If the temperature impulse are sent from the temperature receptor to the thermoregulatory centre
Define homeostasis
Maintenance of the body in a state of dynamic equilibrium despite changes the internal or external conditions
What happens when the environment is hot to the skin
1) sphincter muscle around the arterioles relax causing the arterioles near the skin to dilate and allowing more blood to slow through skin capillaries
2) as more blood flow close to the body surface, the temperature gradient between the body surface and the environment becomes greater so cooling by conduction and radiation increases
How does cooling mechanism on sweating
Sweat glands produce more sweat so cooling by evaporation takes place from skin surface
This cools the skin by evaporation which use heat energy from the body to convert liquid water into water vapour
What happens to the flattening of the hair
Hair erector muscle relax - hairs lie flat against the skin
This stops them from forming an insulating layer by trapping air and allows air to circulate over skin and heat to leave by radiation
What is the heating mechanism (cold) on the skin
1)sphincter muscle around the arterioles contract causing the arterioles near the skin to constrict and allowing less blood to flow through skin capillaries
—> so more blood flows through the deeper shunt vessel—> don’t lose heat to the environment
2)less blood flows to body surface most blood diverted further from the body surface and the environment is lower so cooling by Conduction and radiation decreases
What does shivering do
Muscle are the effectors and they contract in a rapid and regular manner
The metabolic reaction required to power this shivering generate sufficient heat to warm the blood and raise the core body temperature
What does the erection of hairs in warming mechanism (cold)
Forms an insulating layer over the skin surface by trapping air between the hairs and stops the heat from being lost by radiation
How does an increase the temperature of the blood effect the core blood temperature
1) if the temperature of the blood flowing through the hypothalamus increases
2) thermoregulatory centre in hypothalamus activated
3) send impulses along autonomic motor nerve to effectors that increase the blood flow through the skin and increase sweating
4) erector pili muscle are relaxed so that the hairs lie flat and stop shivering
The metabolic rate may be reduced to lower amount of warming in the body
What is the affect of an increase the temperature blood
Sphincter muscle of arterioles relax
Hair erector muscle relax - hair lie flat
Sweat glands produce more sweat
Muscle of diaphragm and rib cage may cause panting
What does the decrease in temperature cause in the core blood temperature
1) temperature of the blood flow through the hypothalamus drops
2) thermoregulatory centre is activated by sending impulses through the automatic nervous system to the skin
3)reduction in blood flow through the capillaries in the skin along with a reduction in the production of sweat and contraction of the erector Pillai muscle to raise the hair
4) impulse in the autonomic motor neurones from thermoregulatory centre also stimulates involuntary contractions of muscle and raise the amount of metabolic warming
What is the drop of
Sphincter muscle of arterioles contract
Hair erector muscle contract - hair stands up
Muscle shivers
Adrenal medulla glands - increased adrenaline
Cooling reduced and warming increased easing temperature
Mechanism of ADH
1)The ADH binds to specific receptor in the cell membrane
2) triggers the formation of cAMP as the second messenger
3) cAMP triggers to vesicles that contain water channel (aquaporins) move to and fuse with the membrane
4) the vesicle containing water channels (aquaporins) that inserted into the membrane make it permeable to water
5) this increases/decrease the permeability of the collecting
6)
How does ADH relate to cAMP
Amount of the ADH released controls the number of channels that inserted ( vesicles containing aquaporins)
ADH level falls, levels of cAMP also drop and water channels are taken out of the membrane and repackaged in vesicles
- makes the tubules impermeable to water again
Channels are stored in vesicles ready for reuse when they are needed again
How ADH mechanism
1)The ADH binds to specific receptor in the cell membrane
2) triggers the formation of cAMP as the second messenger
3) cAMP triggers to vesicles that contain water channel (aquaporins) move to and fuse with the membrane
4) the vesicle containing water channels (aquaporins) that inserted into the membrane make it permeable to water
5) increase permeability of collecting duct
6) more water reabsorption for filtrate to the capillaries
Cooling mechanism
One way to increase heat loss is to supply the capillaries in the skin with a greater volume of blood, which then loses heat to the environment via radiation
Arterioles have muscles in their walls that can relax or contract to allow more or less blood to flow through them
During vasodilation these muscles relax, causing the arterioles near the skin to dilate and allowing more blood to flow through skin capillaries
This is why pale-skinned people go red when they are hot
Cooling mechanism sweating
Sweat is secreted by sweat glands
This cools the skin by evaporation; heat energy from the body converts liquid water into water vapour
Sweating is less effective as a cooling mechanism in humid environments; sweat evaporates more slowly due to a reduced concentration gradient between the sweat and the surrounding air
Cooling mechanism flattening of hairs
The hair erector pili muscles in the skin relax, causing hairs to lie flat
These muscles can be described as effectors, as they respond to a change in body temperature
This stops them from forming an insulating layer of trapped air and allows air to circulate over skin; heat can therefore leave by radiation
Warming mechanism
During vasoconstriction the muscles in the arteriole walls contract, causing the arterioles near the skin to constrict and allowing less blood to flow through skin capillaries
Instead, the blood is diverted through shunt vessels, which are deeper in the skin and therefore do not lose heat to the environment
Vasoconstriction is not, strictly speaking, a ‘warming’ mechanism as it does not raise the temperature of the blood but instead reduces heat loss from the blood as it flows through the skin
Warming mechanism
Boosting metabolic rate
Most of the metabolic reactions in the body are exothermic and this provides warmth to the body
In cold environments the hormone thyroxine, released from the thyroid gland, increases the basal metabolic rate (BMR), increasing heat production in the body
Adrenaline may also be released to speed up the metabolic rate and release more heat
Warming mechanism Shivering
Shivering
This is a reflex action in response to a decrease in core body temperature
This means it is a nervous mechanism, not a hormonal one
In this case muscles are the effectors and they contract in a rapid and regular manner
The metabolic reactions required to power this shivering generate sufficient heat to warm the blood and raise the core body temperature
Warming mechanism erection of hairs
Erection of hairs
The hair erector pili muscles in the skin contract, causing hairs to stand on end
This forms an insulating layer over the skin’s surface by trapping air between the hairs and stops heat from being lost by radiation
Note that, like vasoconstriction, this is a heat retention mechanism rather than a warming mechanism
Warming mechanism less sweating
The sweat glands will secrete less sweat when it is cold
This will reduce the amount of heat lost through the evaporation of sweat
This is a heat retention mechanism rather than a warming mechanism
Define positive feedback system
System in which effectors work to increase an effect that has triggered a response
Define negative feedback system
System for maintaining a condition suchas the concentration of a substance within a narrow range: receptor detect a change in condition and as a result effector are stimulated to restore the equilibrium
How does positive feed back work
A deviation from normal condition is amplified leading to a further deviation
Positive feedback example
Childbirth the release of the hormone oxytocin stimulates uterine contractions. The contraction trigger a positive feedback reaction. More oxytocin is released initiating more contraction
