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 binds to
receptors on effectors initiating a response
Compare the endocrine and nervous systems (4)
Endocrine system Nervous system
Compare the endocrine and nervous systems (4)
Endocrine system Nervous system
Uses hormones
Uses nerve impulses
Hormones travel in the bloodstream to
the target organ
Nerve impulses travel via neurones to
the effectors
hormones have a Slower response
Nerves have a Faster response
Lasts until all hormones have broken
down which takes a long amount of time
Lasts until the nerve impulse stops which
takes a short amount of time
What is the pituitary gland?
Described as the ‘master gland’
Endocrine gland that produces hormones which
control other glands (e.g. adrenal 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 (where the body prepares to
confront danger or flee from it)
State the effects of adrenaline on the body (4)
● Increases heart rate
● Increases blood pressure
● Increases blood flow to muscles
● Increases blood glucose levels
Describe how adrenaline increases heart rate and
blood pressure
● Secreted 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
∴ blood glucose levels increase
● Increased heart rate causes greater blood flow to muscles
● ∴ 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 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 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 set 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 an 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 implantation 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 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
● Stimulates follicle remains to develop into a corpus luteum
which then secretes 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 vessels 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 progesterone 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 taken on its own
● Progesterone combined with oestrogen
How does progesterone prevent pregnancy? (3)
● 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?
Oestrogen 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 longer lasting than non-hormonal methods
● Used to treat other conditions e.g. painful/heavy periods
What are the risks of hormonal contraceptive
methods? (4)
● Side effects e.g. mood changes, acne, bloating
● 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
e.g. condoms, diaphragms (fit over cervix)
What are the benefits of barrier methods of
contraception? (3)
● Condoms are simple and quick to use
● Condoms prevent the spread of STIs
● No side effects
What is the main risk of barrier methods of
contraception?
Less effective than hormonal methods
e.g. condom may split whilst in use.
What two methods (involving hormones) are used to
treat infertility?
● Clomifene therapy
● IVF
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 clomifene drug to women who do not
ovulate regularly
● 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 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
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
● 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
● 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
● 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
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
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
● 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?
Mass
(height) 2
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?
Hip circumference
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
