B5- Homeostasis Flashcards
What is homeostasis
The regulation of conditions inside the body to maintain a stable internal environment, in response to both internal and external conditions
What 3 internal factors are maintained by homeostasis
- Body temperature
- Blood glucose
- water content
Why is a constant internal environment important
Your cells need the right conditions in order to function properly, including the right conditions for enzyme action
What 2 automatic control systems are involved in homeostasis
Nervous and hormonal systems
What is the order of components in control systems
- Receptor detects a stimulus - level is too high/low
- The coordination centre receives and processes the information, then organises a response
- Effector produces a response, which counteracts the change and restores the optimum level- the level decreases/increases
What are receptors
Cells that detect changes in the internal and external environment.
What do coordination centres do
Areas that receive and process the information from the reports. They send out signal and coordinate the responses of the body
State 3 coordination centres in your body
- Brain
- Spinal cord
- Pancreas
What are the 2 types of effectors
- Muscle
- Gland
What does homeostasis maintain optimum
conditions for?
Enzyme action, cell structure and chemical reactions.
State what the two types of effectors do to bring
about a response.
- Muscle will contract
2. Gland secretes enzymes/hormones
What is a negative feedback loop?
A continuous cycle of events that responds when
conditions change away from the set point and
causes it to return conditions to this set point.
Reactions to remove your body from danger
Enables humans to react to their surroundings and to coordinate their behaviour
What is the CNS
The central nervous system, includes the brain and spinal cord.
To summarise the order of how the human nervous system works, fill in the missing words: a -> b -> c -> d -> e
a) Stimulus
b) Receptor
c) Coordinator
d) Effector
e) Respons
Name the three types of neurone.
Sensory
Relay
Motor
What is a synapse
The gap between two neurones, where a signal passes from one neurone to the next.
Summarise in five steps how a synapse works.
- Impulse arrives at the end of one neurone,
- Neurotransmitter is released into the synaptic gap,
- Neurotransmitter diffuses across the synaptic gap,
- Neurotransmitter binds to receptors on a second neurone,
- A new electrical impulse is generated in the second neurone.
Why are reflex actions rapid
They do not involve the brain, therefore no conscious thought.
What do you use reflex actions for
Reactions to remove your body from danger
Name the hormone which controls the “fight or flight” reaction in humans
Adrenaline
Explain two effects adrenaline has on the body
Increased heart rate
Therefore increases delivery of oxygen and glucose to the brain and muscles
Where is thyroxine made
Thyroid gland
What does thyroxine do in the body
Increase the basal (base) metabolic rate, therefore increasing growth and development
Define negative feedback
The mechanism used by the body to bring its internal environment back to normal when the level of something gets too high or too low
State examples of internal conditions controlled by negative feedback
Thyroxine levels, temperature, water levels, blood sugar
Define Glucose
is a simple sugar which is a monomer.
It is soluble and can travel in the blood.
Define glycogen
Is a polymer of glucose and is a storage molecule found in an animal. It is insoluble
Define “homeostasis”.
The regulation of the internal conditions of a cell or organism
to maintain optimum conditions for function in response to
internal and external changes.
What is the endocrine system composed of?
Glands which secrete chemicals called hormones.
How is a chemical “message” transported to
the target organ in animals?
Via the bloodstream.
What is monitored for changes in glucose
concentration?
The blood.
What controls the response to changes in blood
glucose concentration?
The pancreas.
What is produced if the blood glucose
concentration is too high?
Insulin, a hormone.
State two ways insulin helps to lower blood
glucose concentration.
Causes glucose to move from the blood to the cells AND
triggers the conversion of glucose into glycogen.
What is produced if the blood glucose
concentration is too low?
Glucagon, a hormone.
State how glucagon helps to increases blood
glucose concentration.
Triggers the breakdown of glycogen into glucose, which is
released into the blood.
Name two places in the body glycogen is
stored.
Muscle cells and the liver.
What is the process called which responds to a
change from the normal levels in the body by
restoring them back to the normal levels?
Negative feedback.
Define “homeostasis”.
The regulation of the internal conditions of a cell or organism
to maintain optimum conditions for function in response to
internal and external changes.
What is the endocrine system composed of?
Glands which secrete chemicals called hormones.
How is a chemical “message” transported to the
target organ in animals?
Via the bloodstream.
Compare the speed and duration of hormonal
control to nervous control.
(Hormonal) Slower but act for longer.
What is monitored for changes in glucose
concentration?
The blood.
What controls the response to changes in blood
glucose concentration?
The pancreas.
What is produced if the blood glucose
concentration is too high?
Insulin, a hormone.
State two ways insulin helps to lower blood
glucose concentration.
Causes glucose to move from the blood to the cells AND
triggers the conversion of glucose into glycogen.
What is produced if the blood glucose
concentration is too low?
Glucagon, a hormone.
State how glucagon helps to increases blood
glucose concentration
Triggers the breakdown of glycogen into glucose, which is
released into the blood.
Name two places in the body glycogen is stored
Muscle cells and the liver.
What is the process called which responds to a
change from the normal levels in the body by
restoring them back to the normal levels?
Negative feedback.
Type 1 diabetes is caused by…..
An inability to make insulin in the pancreas.
Type 2 diabetes is caused by….
A lack of response by cells to insulin.
State 3 secondary sexual
characteristics that occur during
puberty for males?
Hair growth on face, hair growth on
pubic area and under arms, voice
deepens, growth spurt, sperm
production
State 3 secondary sexual
characteristics that occur during
puberty for females?
Breasts develop, hips widen, hair
growth in pubic region and under arms,
growth spurt, menstrual cycle
Name the main female hormone
involved in development and
reproduction.
Oestrogen
Name the main male hormone
involved in development and
reproduction.
Testosterone
Name the gland which produces
testosterone.
Testes
Name the gland which produces
hormones such as oestrogen?
Ovary
What does testosterone cause to
happen in men?
Stimulates sperm production.
What does oestrogen cause to
happen in women?
Menstrual cycle
Approximately how often is an egg released from the ovaries in a female and what is this process called
Every 28 days, ovulation
What does the release of FSH cause
Maturation of an egg in the ovaries
The release of which hormone stimulates the release of an egg from the ovaries
Luteinising hormone (LH)
Which hormones are involved in the maintenance of the uterus lining
Oestrogen and progesterone
How do oral contraceptives containing hormones prevent pregnancy
Inhibits FSH production do no egg matures
How does an injection,implant or skin patch containing slow-release progesterone prevent pregnancy
Inhibits the maturation of eggs
How do barrier methods, such as condoms and diaphragms, prevent pregnancy
Prevent the sperm reaching the egg
How do intrauterine devices prevent pregnancy
Prevent the implantation of an embryo AND/OR release hormones
How do spermicidal agents prevent pregnancy
Kills or disable
How does abstaining from sexual intercourse prevent pregnancy
Reduces the chance of sperm meeting an egg in the oviduct
How does surgical sterilisation prevent pregnancy
Prevents the sperm or egg being released by the male or female
What is the Sclera
The tough supporting wall of the eye
What is the Cornea
Transparent outer layer found at the front of the eye. It refracts (bends) light into the eye
What is the Iris
The Iris contains contains muscles that allow it to control the diameter of the pupil (the hole in the middle of the eye) and therefore how much light enters the eye
What does the lense do
It focuses on the light onto the RETINA (which contains receptor cells sensitive to light intensity and colour)
What is shape of the lens controlled by
Ciliary muscles and suspensory ligaments
What is the optic nerve
It carries impulses from the receptors on the retina to the brain
What can very bright light damage
The retina
What does being longsited mean
You are unable to focus on near objects
What is wrong with the person’s eye who is long-sighted
The lense is the wrong shape and doesn’t refract (bend) the light enough or the eyeball is too short
What is meant by the term “short-sighted”
You are unable to focus on distant objects
What is wrong with the person’s eye who is short-sighted
The occurs when the lense is the wrong shape refracts the light too much or the eyeball is too long
What do the kidneys do
Acts as filters to “clean the blood”
How to kidneys work
They make urine by taking waste products out of your blood. Substances are filtered out of the blood as it passes through the kidneys
What happens when your kidneys fails
Kidneys remove waste products from the blood this means that if they fail waste substances would build up in the blood and you lose your ability to control the levels of ions and water in your body. You would eventually die
What is the machine called that can filter your blood
A dialysis machine
Can you get a kidney transaplant
Yes
What is the only cure for kidney failure
Kidney transport
What is the biggest issue with kidney transplants
They can be rejected
What two hormones are often prescribed to women to increase fertility
FSH and LH
What are pros to giving women FSH and LH
It helps a lot women to get pregnant when previously they couldn’t
What are cons to giving women FSH and LH
- It doesn’t always work -some women may have to do it many times, which can be expensive
- Too many eggs could be simulated, resulting in unexpected multiple pregnancies
What might be used if the women can’t get pregnant
IVF
What is IVF
- Collecting the egg from a women and sperm from the man and putting them in a lab
- It involves using a treatment called Intra Cytoplasmic Sperm injection (ICSI) where the sperm is injected into the egg
- The fertilised eggs are then grown into embryos in a lab incubator
- Once the embryos are tiny balls of cells, one or two of them are transferred to the women’s uterus to improve the chance of pregnancy
- FSH and LH are given before egg collection to stimulate several eggs to mature (so more that one egg can be collected)
What are cons of IVF
- Multiple births which can increase the chances of miscarriage and stillbirth
- The success rate of IVF is low
Why are some people against IVF
- Can result in unused embryos
- Designer babies
What is Auxin
A plant growth hormone
What do shoots grow towards
The sun
What are commercial uses for auxins
- Killing weeds
- Growing from cutting with rooting powder
- Growing cells in tissue culture
What does gibberellin do
Stimulates plant stems to grow
What is gibberellin
A type of plant growth hormone
What does Ethene do
Can stimulate ripening fruit
How is Ethene produced
A gas produced by aging parts of a plant
What does the acronym Dairy Milk Ice Cream stand for
Dependent
Measured
Independent
Change
What does the acronym SPLAT stand for (to do with graphs)
Scale- go up in equal amounts Plot Line of best fit Axis- variable & units Title
What does the menges control (it’s part of the brain)
Membrane that surrounds the brain. Provides protection against infection
What does the cerebral cortex control (it’s part of the brain)
Highly folded nerves tissues with large surface area for connections to be made
What does the cerebellum control (it’s part of the brain)
“mini brain” that receives information from eyes and ear and it’s responsible for balance, coordination and fine motor skills
What does the medulla oblogla control (it’s part of the brain)
Top of spinal cord responsible for involuntary motion such as breathing
What does the hypothalamus control (it’s part of the brain)
Involved in homeostasis
What does the frontal lobe control (it’s part of the brain)
Concerned with reasoning, planning, parts of speech and movement (motor conext) emotions and problem solving
What does the temporal lobe control (it’s part of the brain)
Concerned with perception and recognition of auditory stimuli (chewing) and memory
What does the parietal lobe control (it’s part of the brain)
Concerned with perception of stimuli such as touch, pressure, temperature and pain
What does the optical lobe control (it’s part of the brain)
Concerned with many aspects of vision
List all the different glands
Pituitary Thyroid Adrenal Pancreas Testes Ovaries Pituitary
Where is the Pituitary gland located
Brain
Where is the Thyroid gland located
Throat
Where is the Adrenal gland located
Above kidneys
Where is the Pancreas gland located
Behind kidneys
What is the pituitary gland
Master that causes other glands to release their hormones
What is the thyroid gland
Produces thyroxine to control the rate of metabolism
What does the pancreas do (regarding homeostasis)
Produces blood glucose levels
What is glucoregulation
The regulating glucose levels
What is homeostasis
Homeostasis is the maintenance of a
constant internal environment in order to
maintain optimum conditions for enzyme
and cellular function
Give examples of conditions maintained by
homeostasis in the body
● Blood glucose concentration
● Body temperature
● Water levels
What two types of responses are used in body
control systems
Nervous and chemical
What three components do all control systems
have
● Receptors
● Coordination centres
● Effectors
What is the function of a receptor
Receptors detect changes in the
environment (stimuli).
What is the function of a coordination centre
Coordination centres obtain and process
information from receptors
What is the function of an effector
Effectors (muscles or glands) bring about
responses to stimuli.
What is the function of the nervous system?
The nervous system allows the body to
react to its surroundings and coordinate an
appropriate response
How does a stimulus lead to a response being carried
out by the body?
● Stimulus is converted into an electrical impulse by the
receptors.
● The electrical impulse passes along sensory neurones to
the central nervous system (CNS).
● The CNS coordinates an appropriate response and an
electrical impulse is sent along motor neurones to the
effector, which carries out the response.
What sequence of events describes how the
nervous system works
Stimulus → receptor → coordinator →
effector → response
What is a reflex action
A reflex action is an automatic and rapid
response which does not involve any
conscious input from the brain
Why are reflex actions important
Reflex actions aid survival by preventing
harm to the body
Describe how a reflex action occurs via a reflex arc
● The stimulus is detected by a receptor.
● An electrical impulse passes along a sensory neurone to the spinal cord
(part of the CNS).
● At a synapse between a sensory neurone and a relay neurone, a
chemical diffuses across the gap and stimulates a new impulse which
passes along the relay neurone.
● The same process occurs at a synapse between a relay neurone and a
motor neurone.
● At the effector, an appropriate response is carried out.
What is the difference between a reflex pathway
and a conscious pathway
Within a reflex pathway, the coordination centre
is a relay neurone found in the spinal
cord/unconscious parts of the brain. In a
conscious pathway, the coordination centre is in
the conscious part of the brain
What is the function of the cerebral cortex?
controls consciousness,
intelligence, memory and
language.
What is the function of the cerebellum?
controls muscular coordination
What is the function of the medulla
controls unconscious activities eg.breathing, heart rate
Why is the investigation and treatment of the
brain difficult
● The brain is a complex and delicate organ.
● The brain is easily damaged and destroyed.
● Certain membranes prevent drugs from reaching
the brain.
● The exact function of each part of the brain is not
known.
What methods are used by scientists to determine
brain function
● Studying patients with brain damage
● Electrical stimulation of the brain
● MRI scans
What stimuli are the receptors of the eye
sensitive to
Light intensity and colour
What are the two main functions of structures
found within the eye
● Focusing on near or distant objects -
accommodation.
● Adaptation to dim light.
Describe the structure and function of the
retina
F - The retina is a light-sensitive layer found at the back of the eye. Light stimulates the retinal cells, resulting in impulses being sent to the brain
Describe the structure and function of the optic
nerve
The optic nerve connects the eye and the brain.
It carries impulses to the brain so that an image can
be visualised
Describe the structure and function of the sclera
The sclera is the tough outer layer of the eye
which protects its internal structures
Describe the structure and function of
the cornea
The cornea is the curved transparent layer at the front
of the eye. It lets light into the eye and allows light to be focused onto the retina.
Describe the structure and function of
the iris
The iris is a muscle which controls the size of
the pupil by contracting or relaxing. This allows the
eye to adjust to bright and dim lighting
Describe the structure and function of the ciliary muscles and suspensory ligaments
The ciliary muscles (C) and suspensory
ligaments (E) hold the lens in place and control
its shape.
Describe how the iris alters the size of the pupil in both
bright and dim light
● Bright light: circular muscles contract and radial
muscles relax - makes pupil smaller to avoid retinal
damage.
● Dim light: circular muscles relax and radial muscles
contract - makes pupil larger so more light can
enter the eye
What is accommodation?
Accommodation is the alteration of the
lens’ shape in order to focus on near or
distant objects
How does the eye focus on a nearby object?
● Ciliary muscles contract.
● Suspensory ligaments loosen.
● Lens becomes thicker and more curved -
light rays are refracted strongly.
How does the eye focus on a far away object
● Ciliary muscles relax
● Suspensory ligaments tighten
● Lens becomes thinner - light rays are
refracted weakly
What is myopia
Myopia (short-sightedness) usually occurs
when the lens of the eye is too curved. As a
result, light is focused in front of the retina so
images appear blurry
How can myopia be treated
Myopia can be treated using glasses with a
concave lense, which spreads out light rays
so they can be focused on the retina.
What is hyperopia?
Hyperopia (long-sightedness) usually occurs
when the lens of the eye is too flat. As a
result, light is focused behind the retina so
images appear out of focus
How can hyperopia be treated?
Hyperopia can be treated using glasses with
a convex lense, which brings the light rays
together so they can be focused on the
retina
What are the two types of contact lenses
Contact lenses are lenses that are placed on the eye.
There are two types:
● Hard - rigid material, last a long time, must be kept
sterile.
● Soft - flexible material, last for a shorter time, more
comfortable
What is laser eye surgery
Laser eye surgery is the use of lasers to fix visual
defects in adults. To treat myopia, lasers reduce the
thickness of the cornea so light is refracted less
strongly. To treat hyperopia, lasers alter the
curvature of the cornea so that light is refracted
correctly
How can replacement lenses be used to treat
visual defects
A replacement lens can either implanted into the
eye (along with the natural lens) or it may replace
the natural lens altogether. Risks of lens
replacement include retinal damage, cataracts
and infections
What are the risks of lens replacement
Risks of lens replacement include retinal
damage, cataracts and infections
Where is body temperature controlled in the body
Body temperature is controlled by the
thermoregulatory centre in the hypothalamus
of the brain
How is temperature monitored by the body
● Thermoregulatory centre has receptors sensitive to blood temperature. ● Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory centre
What physiological changes occur when the body
temperature is too high
● Vasodilation - blood vessels near the surface
of the skin dilate - more heat is radiated away.
● Sweating - evaporation of water takes away
heat energy from the surface of the skin
What physiological changes occur when the body
temperature is too low
● Vasoconstriction - blood vessels near the surface
of the skin constrict - less heat radiated away.
● Shivering - respiration allows muscles to contract.
It is an exothermic process, so heat energy is
released.
● Sweating stops
Give the name of the body’s coordination system
which involves hormones
The endocrine system
What is a hormone
A hormone is a chemical messenger
secreted by a gland. It travels in the blood to
a target organ, where it causes a response
What type of organ secretes hormones?
Glands
Which gland controls many other glands in the
body
The pituitary gland
Why is the pituitary gland considered a ‘master
gland’
It secretes a wide range of hormones,
some of which may stimulate other
endocrine glands
What is the role of the pituitary gland in the endocrine
system
● Secretes human growth hormone - controls human
growth.
● Stimulates the thyroid gland.
● Stimulates ovulation and the production of oestrogen in
the ovaries.
● Stimulates the production of sperm and testosterone in
the testes
What is the role of the thyroid gland in the
endocrine system
Secretes the hormone thyroxine - controls
metabolism, heart rate and body
temperature
What is the role of the pancreas in the
endocrine system
Secretes the hormone insulin - controls
blood glucose levels
What is the role of the adrenal gland in the
endocrine system
Secretes adrenaline - controls the body’s
‘fight or flight’ response
What is the role of the ovaries in the endocrine
system
Secrete oestrogen, which coordinates the
menstrual cycle and the development of
female secondary sexual characteristics
What is the role of the testes in the endocrine
system?
Secrete testosterone, which coordinates the
production of sperm and the development of
male secondary sexual characteristics
Which organ monitors and controls blood glucose
concentration
The pancreas
How does the pancreas respond when blood
glucose levels are too high
The pancreas secretes the hormone insulin.
Insulin binds to receptors on the liver and
muscles, causing excess glucose to be
converted into glycogen and stored
How does the pancreas respond when blood
glucose levels are too low?
The pancreas secretes the hormone
glucagon. Glucagon binds to liver cells,
causing glycogen to be converted into
glucose and released into the blood
How is blood glucose concentration controlled using
a negative feedback loop
● When the blood glucose concentration rises or falls
below the optimum, a hormone is secreted by the
pancreas.
● The action of either hormone (insulin or glucagon)
helps bring back the concentration to the correct
level.
What is Type 1 diabetes?
Type 1 diabetes is an autoimmune disorder in
which the pancreas does not produce sufficient
insulin to control the blood glucose concentration.
As a result, blood glucose levels are often very
high, leading to excessive urination, tiredness and
weight loss
How can Type 1 diabetes be treated
● Insulin injections before meals - allows
glucose to be converted into glycogen.
● Limiting carbohydrate intake.
● Attempts using pancreas and pancreatic cell
transplants; investigations into genetic
engineering of pancreatic cells
What is Type 2 diabetes?
Type 2 diabetes is a disorder in which the body’s cells stop responding to insulin, leading to an uncontrolled blood glucose concentration. Its onset is linked with increasing age and obesity
How can Type 2 diabetes be treated
● Following a carefully-controlled diet ● Doing regular exercise ● Losing weight ● Use of drugs which increase insulin production and effectiveness
What is osmosis?
Osmosis is the movement of water from a
dilute solution to a concentrated solution
through a partially permeable membrane
In what ways is water lost from the body
● During exhalation via the lungs
● Sweating
● Urine (some reabsorbed in the kidney)
In what ways are ions lost from the body
● Sweating
● Urine (some reabsorbed in the kidney)
How are excess amino acids excreted from the
body
● Excess amino acids are deaminated in the liver to
form ammonia.
● Ammonia is toxic, therefore it is converted into urea
● Urea is excreted from the body via sweat and urine
How do the kidneys maintain the balance of water
and other substances in the body
● Filter blood in order to remove waste
products eg. urea.
● Selectively reabsorb useful molecules eg.
glucose, water, ions
What is the full name of the hormone ADH?
Anti-diuretic hormone
Where is ADH secreted in the body
The pituitary gland of the brain
How does ADH affect the reabsorption of water in
the kidneys
● When the blood is too concentrated, the pituitary
gland secretes more ADH.
● ADH travels in the bloodstream to the kidney and
increases the permeability of kidney tubules to water.
● More water is reabsorbed in the kidneys, resulting in
a smaller volume of more concentrated urine
Why is kidney failure dangerous
When the kidneys are damaged, they may be unable
to filter the blood properly. This may lead to:
● A build-up of toxic molecules (eg. urea) in the
body.
● An uncontrolled ion and water balance and cells
being damaged as a result of osmosis
What are the two main ways of treating kidney
failure
● Dialysis
● Transplant
What is kidney dialysis?
Kidney dialysis is the use of a specialist machine
to carry out the function of kidneys. Dialysis fluid
contains the same concentration of glucose and
ions as healthy blood. As a result, only excess
and waste molecules are lost from the blood, and
glucose and ions remain.
What is the function of reproductive hormones
during puberty?
● Males: cause the development of secondary sexual characteristics. ● Females: cause the development of secondary sexual characteristics and the maturation of eggs
What is the main male reproductive hormone?
The main male reproductive hormone is
testosterone, which is produced by the
testes and controls sperm production
What is the main female reproductive hormone
The main female reproductive hormone is
oestrogen, which is produced by the ovaries
and is involved in the menstrual cycle
What is the menstrual cycle
The menstrual cycle is the monthly cycle of
physiological changes that occur in females,
involving the shedding of the uterus lining
(menstruation) and ovulation
Describe the events of the menstrual cycle
● Uterus lining thickens and eggs begin to mature in the
ovaries.
● An egg is released from one of the ovaries (ovulation)
- uterus lining remains thick.
● If the egg is fertilised, pregnancy may occur. If not,
both the egg and the uterus lining are shed during
menstruation
What is ovulation?
Ovulation is the release of a mature egg from
the ovaries, which occurs approximately every
28 days
Name the four main hormones involved in the
menstrual cycle
● Oestrogen
● Progesterone
● Follicle stimulating hormone (FSH)
● Luteinising hormone (LH)
What is the role of FSH in the menstrual cycle?
FSH is secreted by the pituitary gland. It
controls the maturation of eggs within the
ovaries (inside a follicle) and triggers the
production of oestrogen by the ovaries
What is the role of oestrogen in the menstrual
cycle
Oestrogen is produced by the ovaries and
released due to the action of FSH - it causes
the regrowth of the uterus lining.
It triggers the production of LH and restricts the
release of more FSH
What is the role of LH in the menstrual cycle?
LH is produced in the pituitary gland as a
result of oestrogen. Its release triggers
ovulation
What is the role of progesterone in the menstrual
cycle
Progesterone is secreted from the follicle of
the ovary. It sustains the uterus lining and
inhibits FSH and LH
What is contraception
Contraception refers to any method of
preventing pregnancy
What are the two types of oral contraceptives
● Combined contraceptive pill (contains
oestrogen and progesterone).
● Mini pill (contains only progesterone)
How does the contraceptive pill prevent
pregnancy
● Inhibits FSH - eggs do not mature.
● Prevents the development of the uterus lining -
eggs cannot implant.
● Increases the thickness of cervical mucus -
immobilises sperm cells.
What is the contraceptive patch?What is the contraceptive patch?
● Contains both oestrogen and
progesterone.
● It is a patch that is placed onto the skin
for 7 days at a time
What is the contraceptive implant
A small rod inserted under the skin which
continuously releases the hormone
progesterone - lasts for 3 years
What is the contraceptive injection
An injection containing the hormone
progesterone - lasts for approximately 3
months
What is the IUS?
The IUS (intrauterine system) is a small plastic device that is inserted into the uterus. It releases progesterone which thickens cervical mucus and prevents the build-up of the uterine lining
What is the IUD
The IUD (intrauterine device) is a small
copper-containing device inserted into the
uterus, which prevents the implantation of
embryos
What is a spermicide
A spermicide is a chemical that kills or
immobilises sperm cells - however, they
are not very effective, and work better
when combined with barrier methods.
What is a barrier method of contraception
A barrier method of contraception involves a physical
separation between the sperm and the egg. They
include:
● Condoms - thin sheath worn on the penis or inside
the vagina - protects against STIs but may tear/break.
● Diaphragms - a thin cap placed over the cervix -
prevent entry of sperm.
What surgical methods of contraception are
available?
Sterilisation - in males, the sperm ducts
are tied (vasectomy) and in females, the
oviducts are tied.
What is abstinence
Abstinence is the practice of not having sex, which also avoids pregnancy. Some people abstain from sex around the time of ovulation - this is known as the rhythm method, but it is quite unreliable
What are the advantages of fertility treatment
● Allows infertile couples to have children
● Can store a woman’s eggs for later
What are the disadvantages of fertility treatment
● It can be a very expensive process.
● It has a low success rate - especially for older
couples.
● Increases chance of multiple pregnancies -
dangerous for mother and babies.
● Side effects of fertility drugs
What is negative feedback
Negative feedback is a type of control where
the body responds to an increase or
decrease in a factor by returning it to the
optimum level
What is thyroxine
Thyroxine is a hormone released by the
thyroid gland. Its release is triggered by the
thyroid stimulating hormone (TSH). Thyroxine
controls the body’s metabolic rate, growth and
development
How is the release of thyroxine controlled by negative
feedback
● Levels of blood thyroxine falls - detected by
receptors in the brain.
● Pituitary gland releases more TSH.
● More thyroxine produced and released by the
thyroid gland.
● Blood thyroxine level returns to normal.
What is adrenaline?
Adrenaline is a hormone secreted by the
adrenal gland in times of stress. It is
responsible for the ‘fight or flight response’.
What are the effects of adrenaline?
● Increase in heart and breathing rate - delivers oxygen
and glucose to the body.
● Stored glycogen converted to glucose.
● Dilation of pupils.
● Increased mental awareness.
● Blood diverted away from digestive system to
muscles
What is a tropism
A tropism is the response of a plant to a
specific stimulus
What is phototropism
Phototropism is the response of a plant’s
shoot or root to light
What is gravitropism
Gravitropism is the response of a plant’s
shoot or root to gravity
What is auxin
Auxin is a hormone which controls the
growth of a plant’s shoots and roots. When
auxin is unevenly distributed in a growing
plant, the rate of growth will also be unequal
How do plant shoots show positive phototropism
● One side of the shoot is in the light, causing auxin
to move to the shaded side.
● At the shaded side, the cells are stimulated to
grow - the shoot bends towards the light.
● As a result, photosynthesis can occur at a faster
rate.
How do plant shoots show negative gravitropism
● In a horizontal shoot, auxin accumulates in the
lower side due to gravity.
● Cells on the lower side of shoot grow more, causing
the shoot to bend away from the direction of gravity.
● As a result, more light is usually available for
photosynthesi
How do plant roots show positive gravitropism
● In a horizontal root, auxin accumulates in the
lower side, causing cells to grow less.
● The root bends in the direction of gravity
● As a result, more water and nutrients are
available to the plant roots
What are gibberellins
Gibberellins are a type of plant hormone
involved in seed germination
What is ethene
Ethene is a type of plant hormone
involved in cell division and ripening
What are the uses of auxins
● Weedkillers - auxin causes cells to grow at a
rapid rate, causing plant death.
● Rooting powder - auxin causes new plant to
grow very quickly.
● Tissue culture - auxin promotes growth of
roots and shoots.
What are the uses of ethene?
● Control of food ripening in the food industry -
allows fruit to be ripened just before they are
sold.
What are the uses of gibberellins
● Termination of seed dormancy
● Promotion of flowering
● Increase of fruit size
What is the function of the retina
Light is focused here. Contains photoreceptive cells which detect colour and light intensity
What is the function of the optic nerve
Carries impulses from the retina to the brain
What is the function of the sclera
The tough, supporting wall of the eye
What is the function of the cornea
Transparent region of the sclera at the front of the eye. Refreacts light-bends it as if it enters the eye
What is the function of the iris
Has sets of muscles that control the size of the pupil and regulate the light reaching the retina
What are the function of the ciliary muscles and suspensory ligament
Muscles connected to the lens by suspensory ligaments. Control the shape of the lense. Connected the ciliary muscles to the lens and hold the lens and hold the lens in place. Control the shape of the lens
What happens to the size of the pupil when it is dim
Dilated
What happens to the size of the pupil when it is bright
Contracts
What do the circular muscles do with dim light
Relax
What do the circular muscles do with bright light
Contract
Do the radial muscles contract or relax in dim light
Contract
Do the radial muscles contract or relax in bright light
Relax
Define accommodation
This process of changing the shape of the lense o focus on near or distant objects
