Homeostasis And Hormones

Question 1

Release of a second messenger what type

Answer 1

Non steroid hormones
- adrenaline
Insulin
Glucagon
ADH

Hydrophilic so cannot pass through the lipid bilayer

Question 2

Release of a second messenger process

Answer 2

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

Question 3

Role of adrenaline (second messenger model)

If blood glucose is too Low the adrenal gland will also secrete adrenaline

Answer 3

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

Question 4

Hormones enter the cell what substance can pass

Answer 4

Lipid soluble can pass through the lipid bilayer

Oestrogen and testosterone

Question 5

Hormones enter the cell process

Answer 5

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

Question 6

What does liver break down

Answer 6

Excess amino acid

Question 7

Deamination

Answer 7

Amino acid —> keto acid + ammonia

Removing NH3, -2

Question 8

.

Question 9

.

Question 10

What are the 3 Main function of the kidney

Answer 10

Ultrafiltration
Selective reabsorption
Tubular secretion

Question 11

What is the malpighian body

Answer 11

Glomerulus and the bowman capsule

Question 12

What occurs during the ultrafiltration

Answer 12

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

Question 13

Define selective reabsorption

Answer 13

The process by which substance needed by the body are reabsorbed from the kidney tubules back into the blood

Question 14

What adaptation does microvilli provide in selective reabsorption

Answer 14

Provide a large surface area for reabsorption

Question 15

What adaptation does mitochondria provide in selective reabsorption

Answer 15

Produce ATP for active transport

Question 16

What makes up glomerulus filtrate

Answer 16

Glucose urea and salt and water, amino acid and inorganic ions

Question 17

Selective reabsorption process

Answer 17

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

Question 18

Loop of henle role

Answer 18

Sodium ion gradient to enable reabsorption of water is maintained in the medulla

Question 19

Loop of henle process

Answer 19

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

Question 20

Loop of henle descending limb

Answer 20

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

Question 21

Loop of Henley - ascending limb

Answer 21

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

Question 22

The distal convoluted tubule role

Answer 22

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

Question 23

More ADH

Answer 23

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

Question 24

Explain the role of the loop of henle in the absorption of water from the filtrate

Answer 24

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

Question 25

Role of Osmoreceptor

Answer 25

In hypothalamus monitor the blood water potential

Question 26

Too much water

Answer 26

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)

Question 27

Too little water

Answer 27

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)

Question 28

Describes how ADH increases permeability of the distal tubules and the collecting duct to water

Answer 28

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.

Question 29

When the ADH falls

Answer 29

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

Question 30

Explain how ADH control the volume and conc of increase in blood plasma

Answer 30

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.

Question 31

Explain how ADH control the volume and conc of decrease in blood plasma

Answer 31

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.

Question 32

How ADH control of volume

Answer 32

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.

Question 33

How does the body know if we are too hot or too cold

Answer 33

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

Question 34

Define homeostasis

Answer 34

Maintenance of the body in a state of dynamic equilibrium despite changes the internal or external conditions

Question 35

What happens when the environment is hot to the skin

Answer 35

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

Question 36

How does cooling mechanism on sweating

Answer 36

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

Question 37

What happens to the flattening of the hair

Answer 37

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

Question 38

What is the heating mechanism (cold) on the skin

Answer 38

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

Question 39

What does shivering do

Answer 39

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

Question 40

What does the erection of hairs in warming mechanism (cold)

Answer 40

Forms an insulating layer over the skin surface by trapping air between the hairs and stops the heat from being lost by radiation

Question 41

How does an increase the temperature of the blood effect the core blood temperature

Answer 41

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

Question 42

What is the affect of an increase the temperature blood

Answer 42

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

Question 43

What does the decrease in temperature cause in the core blood temperature

Answer 43

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

Question 44

What is the drop of

Answer 44

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

Question 45

Mechanism of ADH

Answer 45

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)

Question 46

How does ADH relate to cAMP

Answer 46

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

Question 47

How ADH mechanism

Answer 47

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

Question 48

Cooling mechanism

Answer 48

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

Question 49

Cooling mechanism sweating

Answer 49

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

Question 50

Cooling mechanism flattening of hairs

Answer 50

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

Question 51

Warming mechanism

Answer 51

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

Question 52

Warming mechanism

Answer 52

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

Question 53

Warming mechanism Shivering

Answer 53

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

Question 54

Warming mechanism erection of hairs

Answer 54

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

Question 55

Warming mechanism less sweating

Answer 55

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

Question 56

Define positive feedback system

Answer 56

System in which effectors work to increase an effect that has triggered a response

Question 57

Define negative feedback system

Answer 57

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

Question 58

How does positive feed back work

Answer 58

A deviation from normal condition is amplified leading to a further deviation

Question 59

Positive feedback example

Answer 59

Childbirth the release of the hormone oxytocin stimulates uterine contractions. The contraction trigger a positive feedback reaction. More oxytocin is released initiating more contraction