Topic 7 – Animal Coordination, Control and HomeostasisTopic 7 – Animal Coordination, Control and Homeostasis-Homeostastis Flashcards
What is homeostasis?
The maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions.
Why is homeostasis important?
To ensure optimum conditions for enzymes and cellular processes in the body
State three conditions within the body that must be controlled by homeostasis
● Temperature
● Blood glucose concentration
● Water levels
What is thermoregulation? (biology only)
The maintenance of core body temperature
Why must body temperature be controlled? (biology only)
Enzymes work best at their optimum temperature. Deviations from this optimum temperature decrease the rate of enzyme-controlled reactions.
What is the optimum temperature for enzymes in the human body? (biology only)
37°C
What does the maintenance of an ideal body temperature depend on? (biology only)
A negative feedback system involving:
● Receptors
● Hypothalamus
● Effectors e.g. sweat glands, hair erector muscles
Where are temperature-sensitive receptors located? (biology only)
● Skin - epidermis (outer layer) and dermis (below epidermis)
● Hypothalamus
What is the function of receptors in the skin and in the hypothalamus? (biology only)
They detect changes in blood
temperature and send information to the hypothalamus.
What is the function of the hypothalamus? (biology only)
It coordinates information from the receptors and sends instructions to the effectors.
What is the function of the effectors? (biology only)
They produce a response to counteract the change in blood temperature and return it to the set point.
Outline the responses of the body to an increase in temperature above 37°C (3) (biology only)
● Vasodilation
● Sweating
● Erector muscles relax, hairs lie flat
What structure produces sweat? (biology only)
Sweat glands found in the dermis
How is sweat released from the skin? (biology only)
Pores in the epidermis release sweat onto the skin’s surface which then evaporates.
How does sweating help to reduce body temperature? (biology only)
Heat energy is used to evaporate sweat. Increased heat transfer from the skin to the environment decreases body temperature.
What is vasodilation? (biology only/higher)
● Dilation of blood vessels near the skin surface
● Blood flows closer to the skin surface
● Greater heat loss to the surroundings
Outline the responses of the body to a decrease in temperature below 37°C (4) (biology only)
● Vasoconstriction
● Shivering
● Hair erector muscles contract
● Little sweat is produced
How does shivering help to increase body temperature? (biology only)
Involuntary contraction of muscles generates heat energy from respiration
How does the contraction of hair erector muscles help to increase body temperature? (biology only)
Hairs stand on end creating pockets of air between hairs and a layer of insulation.
What is vasoconstriction? (biology only/higher)
● Constriction of blood vessels near skin surface
● Less blood flows close to the skin surface
● Less heat loss to the surroundings
Which organ is responsible for the maintenance of blood glucose concentrations?
Pancreas
How are blood glucose concentrations controlled?
Controlled by the hormones insulin and glucagon which are secreted by the pancreas
Insulin and glucagon are antagonistic hormones. What does this mean?
They have opposite effects which counteract one another.
Describe the role of insulin in the regulation of blood sugar levels
● Causes liver and muscle cells to increase their uptake of glucose from the blood
● Glucose is converted into glycogen, a storage molecule
Describe the role of glucagon in the regulation of blood sugar levels (higher)
● Causes the breakdown of glycogen to glucose in the liver
● Glucose is released into the blood
What is the control of blood glucose concentration an example of?
Negative feedback
Describe what happens when blood glucose concentrations become too high (higher)
● Blood glucose concentration increases above a set point
● Pancreas secretes insulin and stops producing glucagon
● Liver and muscle cells increase uptake of glucose
● Glucose is converted to glycogen and stored
● Some glucose may be stored as lipid in tissues
● Blood glucose concentration decreases, returning to normal level
Describe what happens when blood glucose concentrations become too low (higher)
● Blood glucose concentration decreases below a set point
● Pancreas secretes glucagon and stops producing insulin
● Liver cells convert glycogen into glucose which is released into blood
● Blood glucose concentration increases, returning to normal level
What is diabetes?
A condition where the homeostatic control of blood glucose levels stops
What is the cause of type 1 diabetes?
Pancreas does not produce enough insulin
How is type 1 diabetes treated? (3)
● Daily insulin injections at meal times
● Limiting intake of refined sugars
● Regular exercise
What is the cause of type 2 diabetes?
Person develops insulin resistance or doesn’t produce enough insulin (often due to obesity)
How is type 2 diabetes treated? (3)
● Balanced diet
(eating fewer simple sugars and replacing them with more complex carbohydrates)
● Exercise
● Medication or insulin injections (however, these are less effective)
How does exercise help to control diabetes?
Exercise increases respiration in muscle cells. Excess glucose is removed from the blood to produce energy in the form of ATP.
Why are type 2 diabetics advised to replace simple carbohydrates with more complex carbohydrates?
● Simple carbohydrates are broken down quickly so can raise blood glucose levels rapidly.
● Complex carbohydrates take longer to break down so have a reduced effect on blood glucose levels.
What is the Body Mass Index (BMI)?
A value based on height and mass used to categorise an individual as underweight, normal weight, overweight or obese.
How is BMI calculated?
BMI=Mass(kg)/Height(m)(squared)
What BMI values indicate obesity and an increased risk of type 2 diabetes?
BMI value larger than 30
How is an individual’s waist-to-hip ratio calculated
waist-to-hip ratio =waist circumference cm/hip circumference cm
What does a waist-to-hip ratio higher than 1.0 in males or 0.85 in females indicate?
● Abdominal obesity
● Increased risk of developing type 2 diabetes
What is osmoregulation?
The maintenance of constant water
levels in the body fluids of an organism
Why is osmoregulation important? (biology only)
Prevents cells bursting or shrinking when
water enters or leaves by osmosis
Describe what happens to an animal cell if it is
placed into a solution with a higher water
concentration (biology only)
● Higher concentration of water in surrounding solution
● Water molecules move down their water concentration
gradient into the cell by osmosis
● Pressure inside the cell increases, cell bursts (lysis)
Describe what happens to an animal cell if it is
placed into a solution with a lower water
concentration (biology only)
● Lower concentration of water in surrounding solution
● Water molecules move down their water concentration
gradient out of the cell by osmosis
● Pressure inside the cell decreases, cell shrinks (crenation)
Describe what happens to an animal cell if it is
placed into a solution with an equal water
concentration (biology only)
No net movement of water molecules
into or out of the cell
Describe the function of the kidneys (biology only)
● Removes toxic waste substances from the body
● Alters blood water levels
● Alters blood ion levels
What is urine? (biology only)
Waste product of the kidney that
contains urea, excess water and excess
ions
How is urea produced? (biology only)
In the liver, urea is produced from the
breakdown of excess amino acids.
What is the function of the renal artery?
biology only
Supplies blood to the kidneys
What is the function of the renal vein? (biology only)
Drains blood from the kidneys
What is the function of the ureter? (biology only)
Takes urine to the bladder from the
kidneys
What is the function of the urethra? (biology only)
Releases urine from the bladder, out of
the body
What is a nephron? (biology only)
Functional unit of the kidney where
filtration and selective reabsorption takes
place
Describe filtration in the kidneys (biology only)
● Blood flows through the glomerulus under high
pressure
● Small molecules (e.g. urea, glucose), water and
ions are filtered out of the blood and into the
Bowman’s capsule of the nephron
Why do large molecules (e.g. red blood cells,
proteins) remain in the blood? (biology only)
They are too large to fit through the
pores in the capillary walls.
Which substances are selectively reabsorbed from
the nephron tubule? (biology only)
● All sugars
● Some water
● Some ions
What happens to the molecules not selectively
reabsorbed? (biology only)
They travel down the kidney tubule as
urine and are transported to the bladder
via the ureter. Here they are stored and
eventually excreted.
How is the concentration and volume of urine
controlled? (biology only/higher)
controlled by the secretion of
anti-diuretic hormone (ADH)
What produces ADH? (biology only/higher)
Pituitary gland
Describe how ADH affects the reabsorption of water
from the kidney tubules (biology only/higher)
ADH increases the permeability of the
collecting ducts, enabling more water to
be reabsorbed into the blood.
What is required to maintain the ideal water content
of blood? (biology only/higher)
A negative feedback system involving:
● Receptors in the hypothalamus
● Hypothalamus
● Effector i.e. pituitary gland
Describe the negative feedback loop which occurs
when low blood water concentration is detected
(biology only/higher)
.
● Receptors detect low blood water content and send information to the
hypothalamus. This coordinates the information and sends instructions to the
pituitary gland.
● Pituitary gland increases ADH secretion. ADH increases collecting duct
permeability so more water is reabsorbed.
● Blood water content increases. More concentrated urine is produced
Describe the negative feedback loop which occurs
when high blood water concentration is detected
(biology only/higher)
● Receptors detect high blood water content and send information to the
hypothalamus. This coordinates the information and sends instructions to the
pituitary gland.
● Pituitary gland secretes less ADH. Collecting duct becomes less permeable
so less water is reabsorbed.
● Blood water content decreases. More dilute urine is produced.
How can kidney failure be treated? (biology only)
● Kidney dialysis
● Kidney transplant
What is kidney dialysis? (biology only)
A machine artificially filters a patient’s blood.
How does kidney dialysis work? (biology only)
● Selectively permeable barrier separates patient’s blood from
dialysis fluid
● Materials are exchanged across the barrier e.g. urea, excess
ions and water move out of the blood and into the dialysis fluid
● Large cells and proteins remain in the blood
Describe the composition of dialysis fluid
biology only
● Same concentration of glucose and ions as in
normal blood plasma
● No urea
What does a kidney transplant involve? (biology
only)
Taking a kidney from a living donor or
someone recently deceased and
implanting it into the patient.
What is the risk associated with kidney transplants?
biology only
Risk of the body rejecting the
transplanted kidney
What precautions are taken to minimise the risk of
rejection? (biology only)
● Tissue typing ensures that the transplanted
organ is ‘compatible’ with the recipient
● Immunosuppressant drugs help prevent the
immune system from rejecting the organ
