Module: Homeostasis and the kidney:
Q: What is homeostasis?
The maintenance of a constant environment.
Q: State some common mechanisms in the human body that involves homeostasis:
1. Core body temperature
2. Glucose levels
3. Solute potential
Q: What is negative feedback?
A change in a system produces a second change, which reverses the first change.
Q: Describe the general mechanism for negative feedback:
The set point is for a factor is the norm at which the system operates.
The receptor detects the level of the factor and its deviations/change from a set
pointy.
The receptor sends instructions to a co-ordinator, if a change does occur.
The co-ordinator communicates with one or more effectors which make responses
that are corrective procedures.
The factor returns back to normal, monitored by the receptor sand information is fed
back to the effector to stop making the correction.
Q: Describe two examples of negative feedback:
1. Glucose concentration in the plasma. If glucose increases above the set point, insulin
is secreted, reducing the glucose concentration by converting it to glycogen and
increasing the rate at which it is respired. If the levels falls below the set point,
glucagon is secreted, which results in glycogen being converted to glucose.
2. If the body’s core temperature falls below the set point (37 degrees Celsius),
increased respiration generates heat, and constriction of superficial blood vessels
allows the body to retain it. If the temperature rises above the set point, superficial
blood vessels dilate, and heat radiates from the body, reducing its temperature.
Q: Describe two examples of positive feedback:
1. Oxytocin stimulates the contraction of the uterus at the end of a pregnancy. The
contractions stimulate the production of more oxytocin, which increases the
stimulus.
2. When the skin is cut, blood platelets adhere to the cut surface. They secrete
signalling molecules, which attract more platelets.
Q: What is excretion?
The removal of wastes made by the body.
The mammalian body excretes several compounds, using four excretory organs.
Q: What are the two main functions of the kidney:
1. Excretion = the removal of nitrogenous metabolic waste from the body.
, 2. Osmoregulation = the control of the water potential of the body’s fluids (plasma,
tissue fluid and lymph) by regulating the water content, and therefore the solute
concentration.
Q: What compounds are excreted?
Carbon dioxide via the lungs.
Water from the kidney
Urea from the kidney
Creatinine from the kidneys
Uric acid from the skin
Bile pigments from the liver.
Q: How is Urea produced?
Dietary production is digested into amino acids, which are transported to the liver
and then around the body, where they are assimilated into proteins.
Excess amino acids are deaminated in the liver and the amino group is converted to
urea.
Q: Describe the structure of the kidney?
Humans have two kidneys, one either side of the vertebral column.
A tough renal capsule covers each kidney.
Each receives blood from a renal artery and returns blood to the general circulation
in a renal vein.
The blood from the renal artery is filtered in the outer layer, the cortex, at the
bowman’s capsule.
The medulla contains the loops of Henle and the collecting ducts that carry urine to
the pelvis.
The pelvis empties urine into the ureter and a ureter from each kidney carries urine
to the bladder.
Q: Why does blood entering the capillaries of glomerulus from the afferent arteriole have a
high blood pressure?
1. The hearts contraction increases the pressure of the arterial blood.
2. The afferent arteriole has a wider diameter than the efferent diameter.
Q: What three layers separate the blood entering the glomerulus the space inside the
Bowman’s capsule?
1. The wall of the capillary is a single layer of endothelium cells with pores called
fenestrae.
2. The basement membrane which is an extra-cellular layer of proteins, mainly collagen
and glycoproteins. It is a molecular filter and is the selective barrier, acting like a
sieve, between the blood and the nephron.
3. The wall of the bowman’s capsule is made of squamous epithelial cells called
podocytes. Processes from each podocyte, called pedicels, wrap around a capillary,
pulling it closer to the basement membrane. The gaps between the pedicels are
called filtration slits.
Q: What is homeostasis?
The maintenance of a constant environment.
Q: State some common mechanisms in the human body that involves homeostasis:
1. Core body temperature
2. Glucose levels
3. Solute potential
Q: What is negative feedback?
A change in a system produces a second change, which reverses the first change.
Q: Describe the general mechanism for negative feedback:
The set point is for a factor is the norm at which the system operates.
The receptor detects the level of the factor and its deviations/change from a set
pointy.
The receptor sends instructions to a co-ordinator, if a change does occur.
The co-ordinator communicates with one or more effectors which make responses
that are corrective procedures.
The factor returns back to normal, monitored by the receptor sand information is fed
back to the effector to stop making the correction.
Q: Describe two examples of negative feedback:
1. Glucose concentration in the plasma. If glucose increases above the set point, insulin
is secreted, reducing the glucose concentration by converting it to glycogen and
increasing the rate at which it is respired. If the levels falls below the set point,
glucagon is secreted, which results in glycogen being converted to glucose.
2. If the body’s core temperature falls below the set point (37 degrees Celsius),
increased respiration generates heat, and constriction of superficial blood vessels
allows the body to retain it. If the temperature rises above the set point, superficial
blood vessels dilate, and heat radiates from the body, reducing its temperature.
Q: Describe two examples of positive feedback:
1. Oxytocin stimulates the contraction of the uterus at the end of a pregnancy. The
contractions stimulate the production of more oxytocin, which increases the
stimulus.
2. When the skin is cut, blood platelets adhere to the cut surface. They secrete
signalling molecules, which attract more platelets.
Q: What is excretion?
The removal of wastes made by the body.
The mammalian body excretes several compounds, using four excretory organs.
Q: What are the two main functions of the kidney:
1. Excretion = the removal of nitrogenous metabolic waste from the body.
, 2. Osmoregulation = the control of the water potential of the body’s fluids (plasma,
tissue fluid and lymph) by regulating the water content, and therefore the solute
concentration.
Q: What compounds are excreted?
Carbon dioxide via the lungs.
Water from the kidney
Urea from the kidney
Creatinine from the kidneys
Uric acid from the skin
Bile pigments from the liver.
Q: How is Urea produced?
Dietary production is digested into amino acids, which are transported to the liver
and then around the body, where they are assimilated into proteins.
Excess amino acids are deaminated in the liver and the amino group is converted to
urea.
Q: Describe the structure of the kidney?
Humans have two kidneys, one either side of the vertebral column.
A tough renal capsule covers each kidney.
Each receives blood from a renal artery and returns blood to the general circulation
in a renal vein.
The blood from the renal artery is filtered in the outer layer, the cortex, at the
bowman’s capsule.
The medulla contains the loops of Henle and the collecting ducts that carry urine to
the pelvis.
The pelvis empties urine into the ureter and a ureter from each kidney carries urine
to the bladder.
Q: Why does blood entering the capillaries of glomerulus from the afferent arteriole have a
high blood pressure?
1. The hearts contraction increases the pressure of the arterial blood.
2. The afferent arteriole has a wider diameter than the efferent diameter.
Q: What three layers separate the blood entering the glomerulus the space inside the
Bowman’s capsule?
1. The wall of the capillary is a single layer of endothelium cells with pores called
fenestrae.
2. The basement membrane which is an extra-cellular layer of proteins, mainly collagen
and glycoproteins. It is a molecular filter and is the selective barrier, acting like a
sieve, between the blood and the nephron.
3. The wall of the bowman’s capsule is made of squamous epithelial cells called
podocytes. Processes from each podocyte, called pedicels, wrap around a capillary,
pulling it closer to the basement membrane. The gaps between the pedicels are
called filtration slits.
