B2-Topic 5- Homeostasis 2022 Flashcards
Where is body temperature controlled in the
body?
Body temperature is controlled by the thermoregulatory centre in the hypothalamus of the brain
How is temperature monitored by the body?
● Thermoregulatory centre has receptors sensitive to blood temperature.
● Skin has receptors sensitive to skin temperature - sends impulses to
thermoregulatory centre.
What physiological changes occur when the body temperature is too high? 2
● Vasodilation - blood vessels near the surface
of the skin dilate - more heat is radiated away.
● Sweating - evaporation of water takes away heat energy from the surface of the skin.
What physiological changes occur when the body temperature is too low? 3
● Vasoconstriction - blood vessels near the surface
of the skin constrict - less heat radiated away.
● Shivering - respiration allows muscles to contract.
It is an exothermic process, so heat energy is
released.
● Sweating stops
What type of reactions are vasoconstriction and vasodilation
transfer energy from the skin to the environment = exothermic
Give the name of the body’s coordination
system which involves hormones
The endocrine system
What is a hormone?2
chemical messenger
secreted by a gland
. It travels in the blood to
a target organ, where it causes a response.
Why is the pituitary gland considered a
‘master gland’?2
It secretes a wide range of hormones,
some of which may stimulate other endocrine glands
What is the role of the pituitary gland in
the endocrine system?4
● Secretes human growth hormone - controls human
growth.
● Stimulates the thyroid gland.
● Stimulates ovulation and the production of oestrogen in the ovaries.
● Stimulates the production of sperm and testosterone in the testes
What is the role of the thyroid gland in
the endocrine system?
Secretes the hormone thyroxine - controls
metabolism, heart rate and body temperature
What is the role of the pancreas in the
endocrine system?
Secretes the hormone insulin - controls
blood glucose levels
What is the role of the adrenal gland in the
endocrine system?
Secretes adrenaline - controls the body’s
‘fight or flight’ response
What is the role of the ovaries in the endocrine
system?
Secrete oestrogen, which coordinates the
menstrual cycle and the development of female secondary sexual characteristics
What is the role of the testes in the endocrine system?
Secrete testosterone, which coordinates the production of sperm and the development of male secondary sexual characteristics
Which organ monitors and controls blood
glucose concentration?
the pancreas
explain how insulin controls blood glucose (sugar) levels in the body if it is too high.3
pancreas produces the hormone insulin
causes glucose to move from the blood into the cells.
In liver and muscle cells excess glucose is converted to glycogen for storage.by receptors on liver
How does the pancreas respond when blood glucose levels are too low 3
The pancreas secretes the hormone
glucagon.
Glucagon binds to liver cells,
causing glycogen to be converted into
glucose and released into the blood
How is blood glucose concentration controlled using a negative feedback loop? (higher only) 2
When blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas.
● The action of either hormone (insulin or glucagon) helps bring back the concentration to the correct
level.
What is Type 1 diabetes?
an autoimmune disorder
the pancreas does not produce sufficient
insulin to control the blood glucose concentration.
so blood glucose levels are often very
high, leading to excessive urination, tiredness and weight loss
How can Type 1 diabetes be treated?2
Insulin injections before meals - allows
glucose to be converted into glycogen.
● Limiting carbohydrate intake.
● Attempts using pancreas and pancreatic cell transplants; investigations into genetic
engineering of pancreatic cells.
What is Type 2 diabetes?2
the body cells no longer respond to insulin produced by the pancreas.
linked with increasing age and obesity
How can Type 2 diabetes be treated? 4
Following a carefully-controlled diet ● Doing regular exercise ● Losing weight ● Use of drugs which increase insulin production and effectiveness
What is osmosis?
movement of water from a
dilute solution to a concentrated solution
through a partially permeable membrane
ways water is lost from the body?3
● During exhalation via the lungs
● Sweating
● Urine (some reabsorbed in the kidney)
In what ways are ions lost from the body?
2
Sweating
● Urine (some reabsorbed in the kidney)
How are excess amino acids excreted from the body?4
The liver converts excess amino acids into ammonia.
Excess amino acids are deaminated in the liver to form ammonia.
Ammonia is toxic, so converted into urea
Urea is excreted from the body via sweat and urine
How do the kidneys maintain the balance of water and other substances in the body? 2
● Filter blood in order to remove waste
products eg. urea.
● Selectively reabsorb useful molecules eg.glucose, water, ions.
What is the full name of the hormone ADH?
Anti-diuretic hormone
Where is ADH secreted in the body?
The pituitary gland of the brain
How does ADH affect the reabsorption of water in the kidneys?3
● When the blood is too concentrated, the pituitary gland secretes more ADH.
● ADH travels in the bloodstream to the kidney and increases the permeability of kidney tubules to water.
● More water is reabsorbed in the kidneys so a smaller volume of more concentrated urine.
Why is kidney failure dangerous? (biology only) 3
kidneys may be unable to filter the blood properly
leading to:
● A build-up of toxic molecules (eg. urea) in the body.
● An uncontrolled ion and water balance and cells being damaged as a result of osmosis.
What are the two main ways of treating kidney failure?
● Dialysis
● Transplant
What is kidney dialysis? 3
use of a specialist machine to carry out the function of kidneys
Dialysis fluid contains the same concentration of glucose and
ions as healthy blood.
As a result, only excess and waste molecules are lost from the blood, and
glucose and ions remain acroos a partially permeable membrane
Advantages and disadvantages of kidney dialysis 3
+no shortage of diialysis machines
- requires frequent treatments and a controlled diet
- expensive in the long run
Advantages and disadvantages of kidney transplants 4
+allow paitentss to live a normal life
+only expensive initially
- shortage of kidney donars
- paitents have to take anti-rejection drugs for rest of life
What is negative feedback? 2
type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level.
What is phototropism and gravitropism 3
p-growth in response to light
g- growth in response to gravity (geotrophism)
all done by shoot or root
What is auxin? 3
plant hormone
controls the growth of a plant’s shoots and roots
can increase or decrease the growth rates of roots and shoots.
How do plant shoots show positive phototropism? 4
.When a shoot grows, auxin builds up on the shaded side of the shoot.
● the shaded side grows faster
the shoot bends towards the light.
photosynthesis can occur at a faster rate
How do plant shoots show negative gravitropism?4
horizontal shoot, auxin gathers on the lower side due to gravity.
● Cells on the lower side of shoot grow more
shoot bends away from the direction of gravity.
● more light available for photosynthesis
How do plant roots show positive gravitropism?4
horizontal root, auxin builds up on the lower side
causing cells to grow less.
root bends in the direction of gravity
more water and nutrients are available to the plant roots
What are gibberellins?
Gibberellins are a type of plant hormone
involved in seed germination.
What is ethene?
Ethene is a type of plant hormone
involved in cell division and ripening.
What are the uses of auxins?3
● Weedkillers - auxin causes cells to grow at a rapid rate, causing plant death.
● Rooting powder - auxin causes new plant to grow very quickly.
● Tissue culture - auxin promotes growth of roots and shoots..
What are the uses of ethene?
to control ripening of fruit during
storage and transport.
What are the uses of gibberellins?
● Termination of seed dormancy
● Promotion of flowering
● Increase of fruit size
