SB7 Animal Coordination, Control and Homeostasis Flashcards
Define hormone
A chemical substance produced by a gland and carried in the bloodstream, which alters the activity of specific target organs
What system makes use of hormones?
The Endocrine System
What is the pituitary gland?
The master gland, which secrets several hormones in response to the body’s conditions, such as water levels
What hormones are produced in the pituitary gland?
- growth hormone
- follicle-stimulating hormone (FSH)
- LH
What hormone is produced in the thyroid?
Thyroxine
What hormones are produced in the pancreas?
- insulin
- glucagon
What hormones are produced in the ovaries?
- oestrogen
- progesterone
What hormone is produced in the testes?
Testosterone
What hormone is produced in the adrenal gland?
Adrenaline
What are the effects of the growth hormone?
- makes muscle and bone cells divide
- increases ca2+ absorption from the digestive system
- increases protein production
What are the effects of FSH?
Allows egg to mature in the menstrual cycle
What are the effects of LH?
Allows egg to be released in the menstrual cycle
What are the effects of thyroxine?
- increases heart activity
- regulates metabolic rate
- increases fat, protein and carbs breakdown
What are the effects of oestrogen?
- stops FSH release, so that the egg isn’t matured
What are the effects of progesterone?
- thickens the mucus of the cervix
- stops LH release
What are the effects of insulin and glucagon?
- insulin: reduces blood glucose levels
- glucagon: increases blood glucose levels
What are the effects of adrenaline?
- increases blood flow to muscles
- makes the heart work harder
- conversion of glycogen to glucose in liver cells which increases glucose production
- this causes more energy to be released by the muscles in respiration
- and more glucose supplied to the muscles
What are the effects of testosterone?
- increases muscle and bone mass
- makes voice deeper
What is the metabolic rate and how is it measured?
The rate are which chemical reactions occur in the body. It is measured:
- at rest
- in a warm room
- after a long meal
Define homeostasis
The maintenance of constant internal conditions in an organism
Explain what negative feedback is
Responds when conditions change from the ideal or set point and returns conditions to this set point
What are the differences between the nervous system and the endocrine system?
- Nervous system is controlled by electric signals whereas the endocrine is controlled by chemicals
- N is transported by the nerve cells whereas hormones are transported through the bloodstream
- N stimulates a much faster response as compared to E
- The duration of hormones last much longer than that of the nerve impulses
What is the role of the hypothalamus?
It is the part of the brain which controls the water balance, temperature, and secretion of hormones by the pituitary gland
Explain the effect of the negative feedback system when the thyroxine levels in the blood are low
- stimulate the hypothalamus to release TRH
- which causes the release TSH by the pituitary gland
- this hormone triggers the release of thyroxine by the thyroid
- causing the blood levels to return to normal
Explain the effect of negative feedback when the thyroxine levels in the blood are high
- hypothalamus inhibits the production of TRH
- stopping production of TSH
- stopping the thyroxine from being released
- so blood levels can return to normal
When is adrenaline produced and what does it do?
- produced during times of fear and stress
- targets vital organs
- increases heart rate
- boosts oxygen delivery to brain and muscles
What is the menstrual cycle?
The process that the body undergoes every month to prepare for a potential pregnancy
What hormones are involved in the menstrual cycle?
- FSH: maturation of the egg in the ovary
- LH: stimulates the release of an egg cell
- oestrogen: repairing and thickening the uterus lining + inhibiting FSH
- progesterone: maintains uterus lining
Explain the interaction between all the hormones in the menstrual cycle
- the pituitary gland produces FSH which causes the development of a follicle in an ovary
- whilst developing, the follicle produces the hormone oestrogen
- this stops the production of FSH and thickens the uterus lining
- when the oestrogen rises high enough, the pituitary gland releases LH, which causes ovulation, wherein an egg is released from the follicle
- the follicle becomes a corpus luteum which triggers the production of oestrogen and progesterone inhibiting FSH + LH
- if the egg hasn’t been fertilised, the corpus luteum dies and uterus sheds its lining which is menstruation
What is a corpus luteum?
The remains of the follicle in the ovary after it has released an egg
Define contraception
The prevention of fertilisation
State and explain some contraceptive methods
- condom: placed over erect penis, prevents sperm from entering the vagina. 98% success rate
- diaphragm or cap: placed over the cervix, prevents sperm in the vagina from entering the uterus. 92 - 96% success rate
- hormone pill or implant placed under skin: releases hormones to prevent ovulation + thickens cervical mucus, making it difficult for sperm to pass through
Why do some women have difficulties in pregnancy?
- low FSH levels
- very high levels of oestrogen
- poor egg quality
- problems with fallopian tube
- male partner with few healthy sperm
State two methods of fertilisation therapy
- clomiphene therapy
- IVF
Explain Clomiphene therapy
- useful for women who rarely/ never release an egg
- clomifene is a drug that increases blood FSH + LH levels
Explain In Vitro Fertilisation
- useful for people with oviducts and sperm problems
- egg follicle maturation stimulated by hormones
- when egg is released, it is taken from ovary + sperm cells taken from man
- egg and sperms combined to allow fertilisation
- one or two healthy embryos placed in the uterus
Define glycogen
What excess glucose is converted into in liver and muscle cells
What is diabetes
A condition wherein blood glucose levels can’t be controlled by the body
What is the difference between type one and type two diabetes?
- type one: cannot control rising blood glucose concentration because the cells in the pancreas are destroyed by the immune system, so the kidneys end up excreting excess glucose. This is a condition that a person inherits from birth
- type two: the person’s body cells no longer respond to the insulin produced by the pancreas. This is a condition that a person inherits through their lifestyle
How can type one diabetes be controlled?
- injecting insulin
- monitoring diet and levels of physical activity
How can type two diabetes be controlled?
By a regulated carbohydrate-based diet and frequent exercise
What does insulin cause?
- glucose to move from the blood to muscle cells for respiration
- excess glucose to be converted into glycogen which is then stored in the liver
What is a risk factor for acquiring type two diabetes?
- obesity
- as body mass increases, the risk of developing type two diabetes increases significantly
Define thermoregulation and why is it important?
The act of keeping our internal temperature constant, important because if a body temperature of 37 degrees is increased, our enzymes will denature
What happens to our body when we get too cold?
- Skeletal muscles contract rapidly and we shiver
- contractions require energy from respiration which sometimes releases heat
- nerve impulses are set to the hair erector muscles in the dermis which contract
- raises the skin hairs and traps a layer of insulating air to the skin
- reduction of blood flow near the skin which keeps warm blood deeper inside your body, reducing the rate of thermal energy transfer
What happens when we get too hot?
- sweat glands in the dermis release more sweat onto the surface of the epidermis
- sweat evaporates transferring heat energy from the skin to the environment
What is the difference between vasoconstriction and vasodilation and what do they both do?
Control the amount of blood flowing through capillaries
- vasoconstriction: narrowing of arterioles supplying the skin’s blood capillaries, causing less blood to flow
- vasodilation: increase in diameter of the skin’s arterioles to increase blood flow and heat loss by radiation
What is osmoregulation?
The control of water and mineral ions in the blood
What will happen if blood becomes too dilute?
Water will move into cells through osmosis, causing them to eventually swell and burst under pressure
What happens if the blood becomes too concentrated?
Water will move out of cells and they will shrink
What is the role of the urinary system?
Removes impurities and waste products from our blood, which are excreted in urine
What is the route that the blood takes to become purified?
- blood is transported to the kidney through the renal artery
- blood is filtered at a high pressure and the kidney selectively reabsorbs any useful materials, eg: glucose, mineral ions and water. Any excess is sent to the ureter for excretion and eventually the bladder
- the purified blood eventually returns to circulation via the renal vein
What is the role of the kidney?
To regulate the levels of salt, ions and urea in the blood
What is the role of the ureters?
Tubes that carry urine from kidneys to bladder
What is the role of the urethra?
Tube that carries urine out of the body
What is urea and when is it produced?
- produced in the liver when excess amino acids are broken down
- main waste product removed in urine
- as it is not reabsorbed by the kidney
What occurs during kidney failure?
When both kidneys stop working, causing a build-up of waste substances
What are the two treatments available for kidney failure?
- kidney dialysis
- organ transplant
How does dialysis work?
- unfiltered blood is taken from a blood vessel in the arm, mixed with blood thinners / an anti-coagulant to prevent clotting and pumped through the dialysis machine
- inside the machine, blood and the dialysis fluid are separated by a partially permeable membrane
- the blood flows in the opposite direction as compared to the dialysis fluid, allowing for the creation of a concentration gradient for the exchange of substances occur
What is dialysis?
Patients are connected to a dialysis machine which acts as an artificial kidney to remove most of the urea and restore/ maintain the water and ion balance of blood
What does dialysis fluid contain?
- a similar glucose concentration to a normal level of blood
- a concentration of mineral ions similar to that found in normal blood plasma
- no urea
What are the advantages of a dialysis machine?
- allows a person with kidney failure to maintain their health
- blood leaving the machine and going to the patient’s arm will be clean
- greatly reduced levels of urea
- no overall change in blood glucose levels
- correct mineral ions and water balance maintained/ balanced
What are the disadvantages of the dialysis machine?
- requires highly specialised + expensive machinery
- time-consuming (4-6 hours, 2-3 times a week)
- restrictive, mainly occurs in a hospital
- must monitor diet carefully
- will only work for a limited amount of time until a transplant s required
What occurs in a transplant?
Wherein the kidney is replaced altogether
What are the two precautions that must be taken before a transplant?
- tissue typing: they match the antigens on the donor kidney to the host kidney (not a perfect match, but close)
–> takes a long time - immunosuppressant drugs: suppress the immune system
–> must be taken for the rest of the patient’s life
–> makes them more susceptible to pathogen attacks
What are the advantages of a kidney transplant?
- cheaper for the NHS
- Patient’s can lead a normal life
What are the disadvantages of a kidney transplant?
- must take immunosuppressant drugs which decrease the risk of rejection
- shortage of donors
- kidney only lasts for 8-9 years
- any operation carries risks
What are nephrons?
Small units that make up the kidney
What are the stages the kidney works in?
- filtration
- selective reabsorption
- formation of urine
Describe what happens in filtration
- occurs in the glomerulus
- blood passes into the kidney’s many capillaries
- blood under high pressure at the start of the nephron, which helps the ultrafiltration of the blood
- small molecules are squeezed out and pass into the nephron tubule called the Bowman’s Capsule
–> Small molecules: urea, water, ions, and glucose - large molecules too big to fit through the wall and will remain in the blood
Describe what happens in selective reabsorption
- occurs in the proximal convoluted tubule
- kidneys must reabsorb the useful molecules that just got filtered out
- allows those that are not needed to pass out and form urine
- reabsorption of water and ions occur in the loop of Henle and collecting areas of the tubule
What molecules are reabsorbed by the kidney during reabsorption?
- all of the glucose initially filtered out
- as much water as the body requires to maintain a constant water level in the blood plasma
- as many ions as the body needs to maintain a constant balance of mineral ions in the blood plasma
Describe what happens during the formation of urine
- molecules that aren’t reabsorbed continue along the nephron tubule as urine
- this eventually passes down the bladder
- urine exits in the ureter
What are the adaptations of a nephron?
- large surface area of contact between nephron and capillaries
- cell membrane of first convoluted tube has folds (microvilli) increasing the surface area
- cells that use active transport have lots of mitochondria
- cells of bowman’s capsule and glomerulus capillaries have spaces making them leaky
What does ADH affect?
- affects the water potential of the collecting duct of the kidney
What does ADH do if the water potential is too high?
- less ADH is released from the pituitary gland
- making the collecting duct less permeable to water
- leads to more water being released in urination
What does ADH do if the water potential is too low?
- more ADH is released from the pituitary gland
- making the collecting duct more permeable to water
- less water remains in the tubule + more entering blood surrounding the tubule
- less water is released in urination
