Topic 7 - Animal Coordination, Control And Homeostasis Flashcards
What is the endocrine system?
A network of glands that produce and secrete hormones into the bloodstream
What is a hormone?
A chemical signal produced by endocrine glands and released into the blood
Travels to target organ and binds to receptors on effectors initiating a respose
Compare the endocrine and nervous systems (4)
Endocrine - uses HORMONES, hormones travel in BLOODSTREAM to target organ, SLOWER response, lasts until ALL HORMONES BROKEN DOWN (long time)
Nervous system - uses NERVE IMPULSES, these travel via NEURONS to effectors, FASTER response, lasts until NERVE IMPULSE STOPS (short time)
Whats the pituitary gland?
Described as the ‘master gland’
Endocrine gland that produces hormones which control other glands (eg adrenal glands)
What are the adrenal glands?
Endocrine glands that produce adrenaline
Where are the adrenal glands located?
Above the kidneys
Whats adrenaline?
Hormone produced by adrenal glands involved in ‘fight ot flight’ respose
State 4 effects of adrenaline on body
Increased HR
Increased BP
Increased blood flow to muscles
Increased blood glucose levels
Describe how adrenaline increases HR and BP
Secreted by adrenal glands and travels in blood to heart.
Binds to specific receptors on cells in heart.
Causes heart muscle to contract more forcefully and frequently
Describe how adrenaline increases respiration at muscle tissues
Binds to specific receptors on cells in liver.
Triggers breakdown of glycogen stores + release of glucose. (Levels increase)
Increased HR causes greater blood flow to muscles so they receive more oxygen and glucose for respiration
What is negative feedback?
Corrective mechanism allowing only small shifts from set point.
Reverses a change in conditions
What is the thyroid gland?
Endocrine gland that produces thyroxine
Where is the thyroid gland located?
In the neck
What is thyroxine
A hormone secreted by the thyroid gland that controls metabolic rate, HR and temp
What is metabolic rate?
Rate at which biochemical reactions occur in cells
Describe how thyroxine is released
Hypothalamus secretes TRH
TRH stimulates secretion of TSH from pituitary gland
TSH stimulates the release of thyroxine from the thyroid gland
What does TRH stand for?
Thyrotropin releasing hormone
What does TSH stand for
Thyroid stimulating hormone
Describe how a negative feedback system controls blood thyroxine levels
If increase, TRH + TSH secretion is inhibited. Less thyroxine produced by thyroid gland. Levels return to normal
If decrease, TRH + TSH secretion increased. More thyroxine produced by thyroid gland. Levels return to normal
How do the ovaries act as an endocrine gland?
Secrete oestrogen into bloodstream
How do testes act as an endocrine gland?
Secrete testosterone into bloodstream
What is the menstrual cycle
Cycle in women (typically 28 days) involving:
Describe the stages of the menstrual cycle:
1-4: if fertilisation + implantation dont occur, uterus lining sheds and egg expelled with it
4-14: uterus lining thickens and blood vessels grow in prep for implantation of egg
14: egg released from follicle into oviduct
14-28: uterus lining maintained so implantatiom can occur
Name the hormones that control the menstrual cycle (4)
Follicle stimulating hormone (FSH)
Oestrogen
Luteinising hormone (LH)
Progesterone
Describe the role of FSH in the menstrual cycle
Secreted by pituitary gland
Transported in bloodstream to ovaries
Triggers development of follicle in ovaries which releases oestrogen
Describe the role of oestrogen in the menstrual cycle
Secreted by ovaries
Repairs and thickens uterus lining
Inhibits secretion of FSH from pituitary gland
Stimulates secretion of LH from pituitary gland
Describe the role of LH in the menstrual cycle
Surge in LH triggers ovulation
Stimulates folice remains to develop into corpus leteum which then secretes progesterone
Whats a corpus luteum?
Temporary endocrine structure
Mass of cells that releases progesterone
Degenerates after a few days
Describe the role of progesterone in the menstrual cycle
Secreted by corpus luteum
Stimlates growth of blood vessels in uterus lining
Inhibits release of FSH + LH
If no implantation - progesterone kevels decrease and uterus lining sheds. FSH increases and cycle restarts
What happens to progesterone levels if fertilisation and implantation occur?
Placenta produces progesterone so levels remain high. Prevents further ovulation and maintains uterus lining.
What are contraceptives?
Method or device utilised to prevent pregnancy
Which hormones can be taken to prevent pregnancy?
Progesterone on its own
Progesterone combined w oestrogen
How does progesterone prevent pregnancy?
Harder for sperm to enter uterus (cervical mucus thicker)
Thins uterine lining (less chance of egg implantation)
Prevents ovulation in some women
How does oestrogen prevent pregnancy?
Inhibits FSH, preventing ovulation
Outline how progesterone can be administered as a contraceptive (2)
Mini pill taken daily
Injection
Outline how progesterone and oestrogen can be administered as a contraceptive (2)
Combined pill (taken continuously for 21 days then paused for 7 days) Skin patch (worn continuously for 3 weeks then without for 1 week)
What are the benefits of hormonal contraceptive methods (3)
99% effective when used properly
Generally last longer than non hormonal methods
Used to treat other conditions eg painful/heavy periods
What are the risks of hormonal contraceptive methods? (4)
Side effects eg acne/bloating
Dont protect against STIs
May involve uncomfortable medical procedures
Not effective if used incorrectly
Describe the barrier methods of contraception
Prevent sperm and egg meeting
2 examples of barrier methods of contraception
Condoms Diaphragms (fit over cervix)
Benefits of barrier methods of contraception? (3)
Condoms simple and quick
Condoms prevent spread of STIs
No side effects
What is the main risk of barrier methods of contraception?
Less effective than hormonal methods
Eg condom may split while in use
What 2 methods (involving hormones) are used to treat infertility?
Clomifene therapy
IVF
Describe the role of hormones in IVF
FSH + LH given to woman to stimulate egg production and ovulatiom
Eggs retrieved from womans ovaries and fertilised in vitro
Resultant embryo transferred to womans uterus
Outline clomifene therapy
Prescription of clomifene drug to women who dont ovulate regularly
Stimulates secretion of more FSH + LH which triggers egg production and ovulation
What is homeostasis?
Maintenance of stable internal environment in the body despite changes in internal + external conditions
Why is homeostasis important?
To ensure optimum conditions for enzymes and cellular processes in the body
State 3 conditions in the body that must be controlled by homeostasis
Temperature
Blood glucose concentration
Water levels
That is thermoregulation?
Maintenance of core body temperature
Why must body temperature be controlled?
Enzymes work best at their optimum temp. Deviations from this optimum temp decrease rate of enzyme controlled reactions.
What is the optimum temp for enzymes in the human body?
37°C
What does the maintenance of an ideal body temp depend on?
A negative feedback system involving:
Receptors
Hypothalamus
Effectors eg sweat glands
Where are temperature sensitive receptors located?
Skin - epidermis (outer layer) and dermis (under)
Hypothalamus
What is the fuction of receptors in the skin and hypothalamus?
Detect changes in blood temp and send info to hypothalamus
What is the function of the hypothalamus
It coordinates info from the receptors and sends instructions to effectors
What is the function of the effectors?
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 temp above 37°C (3)
Vasodilation
Sweating
Efector muscles relax - hairs lie flat
What structure produces sweat
Sweat glands found in the dermis
How is sweat released from the skin?
Pores in epidermis release sweat onto skin surface - evaporates
How does sweating help reduce body temp?
Heat energy is ised to evaporate sweat
Increased heat transfer from skin to environment decreases body temp
What is vasodilation?
Dilation of blood vessels near skin surface
Blood flows closer to skin surface
Greater heat loss to surroundings
Outline the responses of the body to a ecrease in temp below 37°C (4)
Vasoconstriction
Shivering
Hair erector muscles contract
Little sweat is produced
How does shivering help increase body temp?
Involuntary muscle contractions generates heat energy from respiration
How does the contraction of hair erector muscles help increase body temp?
Hairs stand on end creating pockets of air between hairs and a layer of insulation
What is vasoconstriction?
Constriction of blood vessels near skin surface
Less blood flows close to skin surface
Less heat loss to surroundings
Which organ is responsible for the maintenance of blood glucose concentrations?
Pancreas
How are blood glucose concentrations controlled?
Controlled by hormones insulin and glucagon - secreted by pancreas
Insulin and glucagon are antagonistic hormones. What does this mean?
They have opposite effects which counteract one another
Describe the role of insuli 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
Causes breakdown of glycogen to glucose in liver
Glucose released into blood
What is the control of blood glucose concentration an example of?
Negative feedback
Describe what happens when blood glucose concentrations become too high
Blood glucose concentration increases above set pt.
Pancreas secretes insulin + stops producing glucagon.
Liver and muscle cells increase uptake of glucose.
Glucose converted to glygogen and stored.
Some may be stored as lipid in tissues.
Concentration decreases, returning to normal level.
Describe what happens when blood glucose concentrations become too low
Concentration decreases below set pt.
Pancreas secretes glucagon + stops producing insulin.
Liver cells convert glycogen into glucose - released into blood.
Concentration increases, returning to normal level
What is diabetes?
Condition where homeostatic control of blood glucose levels stops working
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 doesnt produce enough insulin (often due to obesity)
How is type 2 diabetes treated? (3)
Balanced diet (eating less simple sugars + more complex carbs)
Exercise
Medication or insulin injections (less effective)
How does exercise help control diabetes?
Increases respiration in muscle cells
Excess glucose removed from blood to produce emergy in form ATP
Why are type 2 diabetics advised to replace simple carbs with more complex carbs?
Simple carbs = broken down quickly so can raise blood glucose levels rapidly
Complex carbs = broken down slower so have reduced effet on blood glucose levels
What is the BMI?
Body Mass Index = value based on height and mass used to categorise a person as underweight, normal weight, overweight or obese
How is BMI calculated?
BMI = mass (kg) / height² (m)
What BMI values indicate obesity and an increased risk of type 2 diabetes?
> 30
How is an individuals waist-to-hip ratio calculated?
waist circumference / 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
Maintenance of constant water levels in the body fluids of an organism
Why is osmoregulation important?
Prevents cells bursting or shrinking when water enters or leaves by osmosis
Describe what happens to an animal cell if its placed into a solution with a higher water concentration
Water molecules move down their water concentration gradient into the cell from solution by osmosis
Pressure inside cell increases + cell bursts (lysis)
Describe what happens to an animal cell if its placed into a solution with a lower water concentration
Water mo,ecules move down their water concentration gradient out of cell into solution by osmosis
Pressure inside cell decreases, cell shrinks (crenation)
Describe what happens to an animal cell if its placed into a solution with an equal water concentration
No net movement of water molecules into or out of the cell
Describe the function of the kidneys
Removes toxic waste substances from body
Alters blood water levels
Alters blood ions levels
What is urine?
Waste product of the kidney that contains urea, excess water and excess ions
How is urea produced?
In the liver, from breakdown of excess amino acids
What are the 6 structures of the urinary system?
Kidney Renal vein Renal artery Ureter Urethra Bladder
What is the function of the renal artery?
Supplies blood to kidneys
Whats the function of the renal vein?
Drains blood from kidneys
Whats the function of the ureter?
Takes urine to bladder from kidneys
Whats the function of the urethra?
Releases urine from bladder out of body
What is a nephron?
Functional unit of kidney where filtration and selective reabsorption takes place
Describe filtration in kidneys
Blood flows through glomerulus under high pressure.
Small molecules eg urea/glucose water and ions are filtered out of blood and into Bowmans capsule of nephron
Why do large molecules eg red blood cells remain in the blood?
They are too large to fit through the pores in the capillary walls
Which substances are selectively reabsorbed from the nephron tube?
All sugars
Some water
Some ions
What happens to the molecules not selectively reabsorbed?
Travel down kidney tubule as urine and are transported to bladder via ureter. They are stored and eventually excreted.
How is the concentration and volume of urine controlled?
Controlled by the secretion of anti-diuretic hormone (ADH)
What produces ADH
Pituitary gland
Describe how ADH affects the reabsorption of water from the kidney tubules
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?
A negative feedback system involving:
- receptors in the hypothalamus
- hypothalamus
- effector ie pituitary gland
Describe the negative feedback loop which occurs when low blood water concentration is detected
Receptors detect low blood water content + send info to hypothalamus - this coordinates the info and sends instructions to the pituitary gland - increases ADH secretion - increases collecting duct permeability - more water reabsorbed.
Blood water content increases + more concebtrated urine is produced
How can kidney failure be treated?
Kidney dialysis
Kidney transplant
What is kidney dialysis
A machine artificially filters a patients blood
How does kidney dialysis work?
Selectively permeable barrier separates pateints blood from dialysis fluid.
Materials are exchanged across the barrier eg urea, excess ions and water move out of blood and into dialysis fluid.
Large cells and proteins remain in blood
Describe the composition of dialysis fluid
Same concentration of glucose and ions as in normal blood plasma
No urea
What does a kidney transplant involve?
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?
Risk of the body rejecting the transplanted kidney
What precautions are taken to minimise the risk of rejection?
Tissue typing ensures that the transplanted organ is compatible with the recipient.
Immunosuppressant drugs help prevent the immune system from rejecting the organ
