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 cell signalling molecule produced by endocrine glands and released into the blood
Travels to a target organ and bi do to receptors on effectors initiating a response
Compare the endocrine and nervous systems
Endocrine uses hormones, nervous uses nerve impulses
Hormones travel in the blood stream to target organ
Nerve impulse travel via neurones to the effectors
Endocrine is a slower response
Endocrine lasts until all hormones have broken down which takes a long amount of time whereas nerve lasts until the nerve impulse stops which takes a short amount of time
What is the pituitary gland?
Described as the ‘master gland’
It is an Ed doctrine gland that produces hormones which control other glands
What are the adrenal glands?
Endocrine glands that produce adrenaline
Where are the adrenal glands located?
Above the kidneys
What is adrenaline?
A hormone produced by the adrenal glands that is involved in the ‘fight or flight’ response
State the effects of adrenaline on the body
Increases heart rate
Increases blood pressure
Increases blood flow to muscles
Increases blood glucose levels
Describe how adrenaline increases heart rate and blood pressure
Segregated by the adrenal glands, travels in the blood to the heart
Binds to specific receptors on cells in the heart
Causes heart muscle to contract more forcefully and frequently
Heart rate increases, blood pressure increases
Describe how adrenaline increases respiration at muscle tissues
Adrenaline binds to specific receptors on cells in the liver
Triggers breakdown of glycogen stores and release of glucose so blood glucose levels increase
Increased heart rate causes greater blood flow to muscles
So muscle cells receive more oxygen and glucose for respiration
What is negative feedback?
A corrective mechanism that allows only small shifts from a set point
It reverses a change in conditions e.g if the concentration of a hormone increases, negative feedback systems work to reduce the concentration back to normal level
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, heart rate and temperature
What is metabolic rate?
The rate at which biochemical redactions 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 blood thyroxine levels increase above a set point, TRH and TSH secretion is inhibited. Less thyroxine is produced by the thyroid gland. Thyroxine levels return to normal
If blood thyroxine levels decrease below a certain point, TRH and TSH secretion is increased. More thyroxine is produced by the thyroid gland. Thyroxine levels return to normal
How do the ovaries act as an endocrine gland?
They secrete oestrogen into the bloodstream
How do the testes act as an endocrine gland?
They secrete testosterone into the bloodstream
What is the menstrual cycle?
The cycle in women (typically lasting 28 days) that involves:
Shedding of uterus lining (menstruation)
Repair of uterus lining
Release of egg (ovulation)
Maintenance of uterus lining
Describe the stages of the menstrual cycle
Days 1-4: if fertilisation and implantation do not occur the uterus lining sheds and the egg is expelled with it (menstruation)
Days 4-14: uterus lining thickens and blood vessels grow in preparation for the implantation of an egg
Day 14: egg released from a follicle into the oviduct (ovulation)
Days 14-28: uterus lining maintained so implants can occur
Name the hormones that control the menstrual cycle
Follicle stimulating hormone (FSH)
Oestrogen
Luteinising hormone (LH)
Progesterone
Describe the role of FSHin the mentrual cycle
Secreted by the pituitary gland
Transported in the bloodstream to the ovaries
Triggers the development of a follicle in the ovaries which releases oestrogen
Describe the role oestrogen plays in the menstrual cycle
Secreted by the ovaries
Repairs and thickens the uterus lining
Inhibits secretion of FSH from the pituitary gland
Stimulates secretion of LH from the pituitary gland
Describe the role of LH in the menstrual cycle
Secreted by the pituitary gland
Transported in the bloodstream to the ovaries
Surge in LH triggers ovulation
Stimulated follicle remains to develop into a corpus outermost which secreted progesterone
What is 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 the corpus luteum
Stimulates the growth of blood cell Eli’s in the uterus lining (in preparation for implantation)
Inhibits the release of FSH and LH
If no implantation occurs, progesterone levels decrease and the uterus lining sheds. FSH increases and the cycle starts again
What happens to protest levels if fertilisation and implantation occur?
The placenta produces progesterone so levels remain high
This prevents further ovulation and maintains the uterus lining
What are contraceptives?
A method or device utilised to prevent pregnancy
Which hormones can be taken to prevent pregnancy?
Progesterone on its own
Progesterone with oestrogen
How does progesterone prevent pregnancy?
Sperm find it more difficult to enter the uterus as the cervical mucus is thickened
Thins the uterine lining, reducing the likelihood of egg implantation
Prevents ovulation in some women (but not all)
How does oestrogen prevent pregnancy?
It inhibits FSH, preventing ovulation
How can progesterone be administered as a contraceptive?
Injection
Mini pill taken daily
How can progesterone and oestrogen be administered as a contraceptive?
Skin patch
Combined pill
What are the benefits of hormonal contraceptive methods?
99% effective when used properly
Generally longer lasting than non-hormonal methods
Used to treat other conditions
What are the risks of hormonal contraceptive methods?
Side effects
Do not protect against STIs
May involve uncomfortable medical procedures
Not effective if used incorrectly
Describe the barrier methods of contraception
Prevent the sperm and egg meeting
What are the benefits of barrier methods of contraception?
No side effects
Condoms prevent the spread of stis
Condoms are simple and quick to use
What is the main risk of barrier methods of contraception?
Less effective than hormonal methods
What two methods are used to treat infertility?
IVF
Clomifene therapy
Describe the role of hormones in IVF
FSH and LH given to a woman to stimulate egg production and ovulation
Eggs retrieved from the woman’s ovaries and fertilised in vitro
Resultant embryo transferred to the woman’s uterus
Outline clomifene therapy
Prescription of drug which stimulates secretion of more FSH and LH which triggers egg production and ovulation
What is homeostasis?
The maintenance of a stable internal environment in the body
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
Water levels
Blood glucose concentration
What is thermoregulation?
The maintenance of core body temperature
Why must body temperature be controlled?
Enzymes work best at their optimum temperature. Deviations cause a decrease in the rate of enzyme-controlled reactions
What is the optimum temperature for enzymes in the human body?
37°C
What does the maintenance of an ideal body temperature depend on?
A negative feedback system involving:
Receptors
Hypothalamus
Effectors
Where are the temperature sensitive receptors located?
Hypothalamus
Skin
What is the function of receptors in the skin and in the hypothalamus?
They detect changes in blood temperature and send information to the hypothalamus
What is the function of the hypothalamus?
It coordinates information from the receptors and sends instructions to the effectors
What is the function of the effectors?
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 about 37°C
Vasodilation
Sweating
Erector muscles relax, hairs lie flat
What structure produces sweat?
Sweat glands found in the dermis
How is sweat released from the skin?
Pores in the epidermis release sweat onto the skin’s surface which then evaporates
How does sweating help to reduce body temperature?
Heat energy is used to evaporate sweat.
Increased heat transfer from The skin to the environment decreases body temperature
What is vasodilation?
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
Vasoconstriction
Shivering
Hair erector muscles contract
Little sweat is produced
How does shivering help to increase body temperature?
Involuntary contraction of muscles generates heat energy from respiration
How does the contraction of hair erector muscles help to increase body temperature?
Hairs stand on end creating pockets of air between hairs and a layer of insulation
What is vasoconstriction?
Construction 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?
By the hormones insulin and glucagon which are secreted by the pancreas
Insulin and glucagon and 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
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?
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
Pancreas secreted 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 stop working
What is the cause of type 1 diabetes?
Pancreas does not produce enough insulin
How is type 1 diabetes treated?
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?
Balanced up diet
Exercise
Medication
How does exercise help to control diabetes?
It increases respiration in muscles 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 sugar levels rapidly
Complex carbohydrates take longer to break down so have a reduced effect on blood glucose levels
What is the body mass index?
A value based on height and mass used to categorise an individual as underweight, normal weight, overweight, or obese
How is BMI calculated?
Mass/height^2
What BMI values indicate obesity and an increased risk of type 2 diabetes?
A BMI larger than 30
How is an individual’s waist to hip ratio calculated?
Waist circumference/hip circumference
What does a waist to hip ratio higher than 1.0 in males or 0.85 in females indicate?
Abdominal obesity
Increased rick 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?
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
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
The water molecules move down their water concentration gradient out of the cell by osmosis
Pressure inside the cell decreases, cell shrinks (crenation)
What is the function of the kidneys?
Removes toxic waste substances from the body
Alters blood water levels
Alters blood ion levels
What is urine?
Waste product of the kidney that contains urea, excess water and excess ions
How is urea produced?
From the breakdown of excess amino acids
What are the structures of the urinary system?
Kidney Renal vein Renal artery Ureter Urethra Bladder
What is the function of the renal artery?
Supplies blood to the kidneys
What is the function of the renal vein?
Drains blood from the kidneys
What is the function of the ureter?
Takes urine to the bladder from the kidneys
What is the function of the urethra?
Releases urine from the bladder, out of the body
What is a nephron?
Functional unit of the kidney where filtration and selective reabsorption takes place
Describe filtration in the kidneys
Blood flows through the glomerulis 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?
They are too big to fit through the pores in the capillary walls
Which substances are selectively reabsorbed from the nephron tubule?
All sugars
Some water
Some ions
What happens to the molecules not selectively reabsorbed?
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?
By the secretion of anti-diuretic hormone (ADH)
What produces ADH?
Pituitary gland
Describe how ADH affects the reabsorbtion of water from the kidney tubules
It increases the permeability of the collecting ducts, enabling more water to be reabsorbed into the blood
What is required o maintain the ideal water content of blood?
A negative feedback system involving:
Receptors I. The hypothalamus
hypothalamus
Effectors
Describe the negative feedback loop which occurs when low blood water concentration is detected
Receptors detect low blood water content and send information to the hypothalamus. This coordinated the information and sends instructions to the pituitary gland
This 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
Receptors detect high blood water content and send information to the hypothalamus. This coordinated the information and sends instructions to the pituitary gland
This 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?
Transplant
Dialysis
What is kidney dialysis?
A machine artificially filters a patient’s blood
How does kidney dialysis work?
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
No urea
Same concentration of glucose and ions as in normal blood plasma
What does a kidney transplant involve?
Taking a kidney from a living donor or someone recently deceased and implanting it into the patient
What aid the risk associated with kidney transplants?
Risk of the body rejecting the transplanted kidney
What precautions are takes 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
