Topic 7 - Animal Coordination, Control and Homeostasis Flashcards
7.1 - What are hormones?
It is part of the response system called the hormonal system, which uses chemical messenger called hormones.
These hormones are carried through the blood, so take time to reach body parts.
Hormones are released by endocrine glands such as the pituitary and the thyroid gland.
7.1 - Where are different hormones produced?
The pituitary gland releases hormones such as FSH, LH, ACTH and growth hormone.
The thyroid gland produces thyroxine.
Pancreas have cells that produce insulin and some that produce glucagon.
The ovaries produce the sex hormones oestrogen and progestrone.
The adrenal glands release adrenalin.
The testes release the sex hormone testosterone.
7.1 - What are target organs?
An organ affected by a specific hormone is a target organ.
Different organs can be a target organ of the same hormone.
Hormones change what the target organ does. ( Growth hormone stimulates cells to divide )
Some endocrine glands are target organs for other hormones.
For example, oestrogen released by the the ovaries can stimulate the pituitary gland to produce growth hormone.
As there is an increase in sex hormones during puberty, growth increases. This is why puberty increases growth rate.
7.2 - What is adrenalin and its target organs?
Adrenalin is a hormone released from the adrenal glands.
In frightening or exciting situations, there are more impulses from neurones in the spinal cord to the adrenal glands, which releases large amounts of adrenalin.
Adrenalin has many target organs, this includes the liver, where glycogen ( storage of glucose in polymers ) is broken down into glucose which is released into blood to provide additional glucose for respiration.
Together, all the effects prepare the body for the fight or flight response.
7.2 - What are the effects of adrenalin on its target organs?
Heart muscle cells contract more rapidly, which increases heart rate and leads to higher blood pressure.
Diameter of blood vessels leading to muscles widen, increasing blood flow to muscles.
Diameter of blood vessels leading to other organs narrow, reducing blood flow to those organs and increasing blood pressure.
Liver cells convert glycogen to glucose and it is released into the blood, increasing blood sugar concentration.
This prepares the body for the fight or fight response.
7.3 - What is metabolic rate and resting metabolic rate and what affects it?
Metabolic rate is the rate at which energy in food is transferred through chemical reactions to keep the body alive.
Resting metabolic rate is measured with a person at rest, in a warm room and long after the person has eaten.
Thyroxine affects metabolic rate, released from the thyroid gland.
This is because when absorbed by cells, it causes heart cells to contract more rapidly and increase the rate of breakdown of proteins and carbohydrates in cells.
7.3 - What is negative feedback?
The amount of thyroxine produced by the thyroid gland is controlled by the hypothalamus that releases TRH and the pituitary gland which releases TSH.
A decrease in thyroxine concentration causes the hypothalamus to send signals to the pituitary gland to release TSH into the bloodstream.
TSH signals the thyroid gland to release more thyroxine into the blood.
The increase in thyroxine is detected by the hypothalamus, preventing the release of TSH from the pituitary gland.
An increase in thyroxine concentration causes the hypothalamus to release TRH into the bloodstream.
TRH signals the thyroid gland to release less thyroxine into the blood.
The decrease in thyroxine is detected by the hypothalamus, which then triggers TSH again to increase the thyroxine concentration in blood.
This is the negative feedback cycle.
7.4 - What is the menstrual cycle?
The menstrual cycle is a cycle of changes in a woman’s reproductive system, lasting 28 days.
The cycle prepares the woman’s body for the fertilisation of an egg cell and continues from puberty at 12 to menopause at 50.
7.4 - What are the stages of the menstrual cycle?
Days 1-5 - Menstruation happens, this is when the uterus lining breaks down and is lost with an unfertilised egg cell.
Days 6-12 - Menstruation ends and the uterus lining starts to thicken again.
Days 13-15 - Ovulation happens, this is when the ovary releases the egg.
Days 16-28 - Fertilisation and pregnancy is more likely as the uterus lining continues to thicken and the egg travels along the oviduct to the uterus.
The cycle starts again.
7.4 - What are the roles of the hormones oestrogen and progestrone in the menstrual cycle?
As the concentration of oestrogen in the blood increases the uterus wall thins.
As the concentration of progesterone in the blood increases the uterus wall thickens.
Oestrogen concentration is highest between days 10 to 22, causing the uterus lining to grow again.
Progesterone concentration is highest between 16-28, maintaining the lining of the uterus and supports a pregnancy if egg is fertilized.
7.5 - Explain the interactions of oestrogen, progesterone, FSH and LH
FSH ( follicle-stimulating hormone ) and LH ( lutenising hormone ) are released from the pituitary gland.
FSH stimulates growth and maturation of egg follicle, these maturing follicles stimulate oestrogen production.
LH surge triggers ovulation, when the egg follicle becomes the corpus luteum, which releases progesterone.
When oestrogen and progesterone fall at the cycle’s end this triggers menstruation.
Low levels of progesterone allow FSH to be released.
High levels of oestrogen release more LH
7.6 - How does hormonal contraception influence the menstrual cycle and prevent pregnancy?
Contraception is the prevention of fertilisation.
Hormonal contraception uses a progesterone-like hormone to inhibit FSH and LH from being produced.
This prevents the fall of hormone concentration at the end of the cycle.
7.7 - Evaluate hormonal and barrier methods of contraception
Male condom - placed over penis and prevents sperm entering vagina.
Diaphragm - placed over cervix to prevent sperm entering the uterus.
Hormone pill - Releases hormones to prevent ovulation and thickens mucus at cervix, making sperm hard to pass through.
Abstaining from intercourse can ensure the egg isn’t fertilised.
Condoms and diaphragms can tear and let sperm through.
Hormone pill can lead to mood swings and depression.
7.8 - Explain the use hormones in ART including IVF and clomifene therapy
Problems with conception can be overcome using ART ( Assisted Reproductive Technology ) , which uses hormones and other techniques to increase likelihood of pregnancy.
Clomifene therapy is used in women who rarely or never release egg cells during their menstrual cycles. Clomifene is a drug used to help increase concentration of FSH and LH in the blood.
Another ART technique is IVF ( in vitro fertilisation ). This can overcome problems like blocked oviducts or if the make produces few healthy sperm cells.
7.8 - Explain how IVF is carried out
Egg follicle maturation stimulated by hormones.
Egg cells released and taken from the ovary.
This is combined with sperm cells from the man on petri dishes.
One or two healthy embryos are placed in the uterus.
7.9 - What is homestasis?
Maintaining a constant internal environment in response to internal and external change.
Examples of homeostasis in the body include temperature control and control of water content.
7.10B - Explain the importance of homeostasis via thermoregulation and osmoregulation
Thermoregulation is the control of the body temperature, keeping the temperature of major organs at 37°C.
A temperature above 38°C is a fever.
A temperature below 36°C causes hypothermia.
Both of these affect how well enzyme work in the body to catalyse reactions.
Osmoregulation is the control of the balance of water and mineral salts in the body.
If this balance is wrong then cells may take in or lose too much water by osmosis.
This imbalance can damage cells as water is needed for molecules to move for reactions and to maintain the cell shape.
7.11B - How does thermoregulation take place when the body is hot?
The hypothalamus is a small part of the brain that constantly monitors temperature.
It can detect temperature changes in the brain and blood by receiving information from temperature receptors in the dermis of the skin.
If the body temperature exceeds 37°C, the hypothalamus detects this and the sweat gland secretes sweat.
Sweat spreads out as a thin layer over the epidermis, it then evaporates, transferring energy from the skin to the surroundings, cooling the skin.
The hypothalamus also increases blood flow near to the skin surface transferring the energy from blood to the surroundings, cooling the skin.
Erector muscles are relaxed so hair is flat.
7.11B - How does thermoregulation take place when the body is cold?
If the hypothalamus detect blood or brain temperatures below 37°C it causes changes in the body. Temperature receptors on the epidermis gives these signals to the hypothalamus that cause the changes in the body.
Shivering happens, where muscles contract and relax rapidly, some of the energy from cell respiration of muscles are used as heat energy for the body.
Contraction of erector muscles in the dermis of the skin lead to body hairs standing upright. This is less effective in humans but in mammals, it traps air next to the skin for insulation.
There is also a reduction in the blood flow near the skin, keeping the warm blood deeper in the body. This reduces energy transfer of heat to the air.
7.11B - How does thermoregulation happen via the changes in blood flow near the skin?
When it is cold, the hypothalamus sends nerve impulses to blood vessels deep in the skin, making them narrow, this is vasoconstriction.
This reduces blood flow near the skins surface and energy transfers to the air.
When it is hot, the hypothalamus causes blood vessels to widen, this is vasodilation.
This increases blood flow through blood vessels, bringing warm blood nearer to the skins surface and increases energy transfers to the surrounding, cooling the body.
7.13 - How does insulin control blood glucose concentration?
When food is digested, glucose is released from carbohydrates.
This is absorbed from the small intestine into the blood and then into cells where it is used during respiration.
Cells take time to take in glucose released by digestion meaning there is a risk that glucose can reach high concentration in blood.
High blood glucose levels can lead to damaged organs, however, this doesn’t happen in most people as the blood glucose levels are controlled.
As blood glucose rises, it stimulates cells in the pancreas to release insulin.
Insulin causes cells in the liver and other organs to take in glucose and store it as glycogen, decreasing its concentration back to normal levels.
7.14 - Explain how blood glucose concentration is regulated by glucagon
If blood glucose concentration falls too low, glucagon is released from other pancreatic cells.
Glucagon causes liver cells to convert glycogen back into glucose, which is released into the blood.
As blood glucose concentration increases, the amount of glucagon released from the pancreas falls.
7.15 - Explain the cause of type 1 diabetes and how it is controlled
Type 1 diabetes is when pancreatic cells that should produce insulin do not.
This is due to the body’s immune system destroying these cells, this means they cannot control their blood glucose levels.
When blood glucose concentration is high, glucose is detected urine, this is the first test for type 1 diabetes.
7.16 - Explain the cause of type 2 diabetes and how it is controlled
Type 2 diabetes is caused by insulin-releasing cells not producing enough insulin or by target organs not responding properly to the hormone.
People with type 2 diabetes may have some response to insulin so are treated differently to those with type 1 diabetes.
For some people, eating healthily and keeping sugar low controls their glucose.
For severe conditions, they are given medicine to reduce the amount of glucose the liver releases into the blood and to increase sensitivity of target organs responding to insulin.
