B5 Flashcards
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme action and cell function
What are the conditions controlled in the human 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 our control systems have?
Receptors
Coordination centres
Effectors
What is the function of a receptor?
Receptors detect changes in the environment this is called stimuli
What is the function of the coordination centre?
Coordination centres obtain and process information from receptors
What is the function of an effector?
Bring about responses to stimuli which restore optimum levels
What are effectors?
Muscles and glands
What is the function of the nervous system?
The nervous system allows a body to react to surroundings and coordinate an appropriate response
How is a stimulus response carried out by the body?
Stimulus is converted into an electrical impulses by the receptor
The electrical impulses passed along a sensory neurons to the central nervous system
The central nervous system coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector which carries out the response
What is the central nervous system?
The brain and the spinal cord
What sequence of events describes how the nervous system works?
Stimulus— receptor— coordinator—effector—response
What is a reflex action?
An automatic and rapid response, which does not involve any conscious input from the brain
Why are reflex actions important?
They protect the body from harm
How does the reflex arc work?
The stimulus is detected by a receptor
An electrical impulse is passed along a sensory neurone to the spinal cord
At the synapse between the sensory neurone and the relay neurone a new impulse is stimulated which is passed along
The same process happens at the synapse between a relay neurone and a motor neurone
At the effector a response is carried out
What happens at the synapse?
Chemical messengers are diffused through the synapse
What is the function of the cerebral cortex?
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 e.g. heart rate and breathing
Why is the investigation and treatment of the brain difficult?
It is a complex and delicate organ meaning it is easily damaged and destroyed
Membranes prevent drugs from reaching the brain
Exact function of each part of the brain is not known
What methods are used by scientist to determine brain function?
Studying patients with brain damage
Electrical stimulation of the brain
MRI scans
What stimuli are receptors of the eye sensitive to?
Light intensity and colour
What are the two main functions of the structures found within the eye?
Accommodation to focus on near or distance objects
Adaptation to dim/bright light
What is the function of the retina?
Sends impulses to the brain as the light stimulates the retinal cells
What is the structure of the retina?
A light sensitive layer found at the back of the eye
What is the function of the optic nerve?
It carries impulses to the brain so that an image can visualised
What is the structure of the optic nerve?
It connects the eye and the brain
What is the function of the sclera?
Protects the internal structure of the eye
What is the structure of the sclera?
A tough outer layer of the eye
What is the function of the cornea?
Let’s light into the eye and allows light to be focused onto the retina
What is the structure of the cornea?
It is a curved transparent layer at the front of the eye
What is the function of the iris?
To control the size of the pupil by contracting or relaxing to allow the eye to adjust to bright and dim light
What is the structure of the iris?
The iris is a muscle so that it can contract or relax
What is the function of ciliary muscles and the suspensory ligaments?
They hold the lens in place and control the shape
How does the Iris alter the pupil to adjust to bright light?
Circular muscles contract and radial muscles relax and makes the pupil smaller to avoid retinal damage
How does the Iris alter the pupil to adjust to dim light?
Circular muscles relax and radial muscles contract to make the pupil larger so more light can enter the eye
How does the eye focus on a nearby object?
Ciliary muscles contract
Suspensory ligaments loosen
Lens becomes thicker and more curved to refract light rays strongly
How does the eye focus on far away objects?
Ciliary muscles relax
suspensory ligaments pulled tight
lens pulled thin and only slightly refracts light rays
what are the two common defects of the eye?
myopia and hyperopia
what is myopia?
short sightedness: when the lens of the eye is too curved
how can myopia be treated?
using glasses with a concave lens which spreads out light rays so can be focused on the retina
what is hyperopia?
long sightedness: when the lens of the eye is too flat
how can hyperopia be treated?
using glasses with a convex lens which brings the light rays together so they can be focused on the retina
what are two types of contact lenses?
hard and soft
hard: rigid material, last a long time, must be kept sterile
soft: flexible material, last for a short time, more comfortable
what is laser eye surgery?
the use of lasers to fix visual defects in adults
how can replacement lenses be used to treat visual defects?
a replacement lens that can be implanted into the eye or that can replace the natural lens
what are the risks of lens replacement?
damage to the retinal, cataracts and infections
how is body temperature monitored?
by the thermoregulatory centre in the brain
how does the thermoregulatory centre control the body temperature?
it has receptors sensitive to blood temperature and skin has receptors sensitive to skin temperature which sends impulses to the thermoregulatory centre
what physical changes occur when body temperature is high?
vasodilation: blood vessels near the surface of the skin dilate
sweating: evaporation of water
what do both the physical responses to high temperature cause?
a transfer of energy from the skin to the environment
what physical changes occur when the body temperature is low?
vasoconstriction: blood vessels constrict near surface of the of the skin
skeletal muscles contract: shivering
sweating stops
how does shivering increase body temperature?
respiration that allows muscles to contract is an exothermic reaction so heat energy is released
what is the name of the body’s coordination system that involves hormones?
the endocrine system
what is the endocrine system?
it is composed of gland which secrete chemicals called hormones directly into the bloodstream and the blood carries the hormone to the target organ.
what gland controls many other glands in the body?
the pituitary gland
what is meant by the pituitary gland controlling many other glands?
it secretes a wide range of hormones some that stimulate other endocrine glands
what hormones does the pituitary gland produce?
FSH and LH
what is FSH?
a hormone that stimulates the ovaries to produce oestrogen
what is LH?
a hormone that stimulates ovulation
where is the pituitary gland?
in the brain
what hormone does the gland thyroid produce?
thyroxine
what is thyroxine?
a hormone that controls metabolism, heart rate and body temperature
where is the thyroid gland?
in the throat
what hormone does the adrenal gland produce?
adrenaline
what is adrenaline?
a hormone which prepares the body for a flight or fight response
where is the adrenal gland?
in the centre of the body around the kidneys
what hormones does the pancreas produce?
insulin
what is insulin?
a hormone which is used to regulate blood glucose level
where is the pancreas?
in the same region as the adrenal gland however it is further forward than the kidneys
what hormones does the ovaries produce?
oestrogen
what is oestrogen?
a hormone which is involved in the menstrual cycle: it stimulates the release of LH and inhibits release of FSH
where are the ovaries?
the lower region of the torso above the vagina
what hormone does the testes produce?
testosterone
what is testosterone?
a hormone which controls puberty and production
where are the testes?
the lower region of the torso above the penis
which organ monitors and controls blood glucose concentration?
the pancreas
how does the pancreas response to a high level of blood glucose?
it produces the hormone insulin
insulin causes glucose to move from the blood into the cells
in the liver and muscle cells excess glucose is convert to glycogen for storage
how does the pancreas respond when blood glucose levels are low?
pancreas produces the hormone glucagon
glucagon causes glycogen to be converted into glucose
the glucose is then released into the blood
how does glucagon interact with insulin in a negative feedback cycle?
when blood glucose concentration rises/falls past the optimum, a hormone is produced by the pancreas (glucagon or insulin)
the action of the hormone brings back the concentration to the correct level
what is type 1 diabetes?
a disorder in which the pancreas fails to produce sufficient insulin which leads to uncontrolled high blood glucose levels
what is the result of high blood glucose levels in a type 1 diabetes patient?
excessive urination, tiredness and weight loss
how can type 1 diabetes be treated?
insulin injections
limiting carbohydrates intake
pancreas and pancreatic cell transplants
how is insulin injection a treatment for type 1 diabetes?
it allows the glucose to be converted into glycogen to lower the blood glucose concentration
what is type 2 diabetes?
a disorder where the body cells no longer respond to insulin produced by the pancreas
what are the treatments for type 2 diabetes?
a carbohydrate controlled diet and an exercise regime
why is obesity a risk factor for type 2 diabetes?
being overweight stems from a diet high in sugar and the body being resistant to insulin results in a high blood sugar level
what ways is water lost from the body?
during exhalation (through the lungs)
sweating
urine
what else is lost from the skin through sweating?
as well as water; ions and urea
what happens is cells lose or gain too much water by osmosis?
they cannot function efficiently
how is excess water, ions and urea removed?
through the kidneys in the urine
how do the kidneys make urine?
taking the waste products out of your blood, by filtering them out as it passes through the kidneys
this process is called filtration
what happens to the useful products within the blood?
the kidneys reabsorbs them back into the blood
this is called selective reabsorption
how is excess amino acids in the body excreted from the body?
they are deaminated in the liver to form ammonia
ammonia is toxic so it is immediately converted into urea for safe excretion
the urea is removed from the body by sweat and urine
what products are absorbed by the kidneys?
glucose, specific ions and the correct amount of water
what hormone controls the water level?
ADH: anti-diuretic hormone
where is the hormone ADH produced?
by the pituitary gland of the brain
when is ADH released from the pituitary gland?
when the blood is too concentrated
how does ADH cause reabsorption of water in the kidneys?
ADH travels in the bloodstream to the kidney and increases permeability of the kidney tubes to water
more water is reabsorbed in the kidneys resulting in a smaller volume of more concentrated urine
what is the process of reabsorbing water controlled by?
negative feedback
why is kidney failure dangerous?
they cannot filter the blood properly so may lead to a build up of toxic molecules in the body, cells will be damaged and there will be uncontrolled ion and water balance
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
only excess and waste molecules are lost from the blood and the glucose ions remain
what are the disadvantages of dialysis?
usually done 3 times a week for 3-4hrs
can cause blood clots and infection
expensive for the nhs to run
what are the advantages of dialysis?
can keep the patient alive while being on the waiting list for a donor
does the job of the kidneys that they can no longer do
what is a kidney transplant?
a surgery where the kidney/kidneys of which do not work correctly are replaced with different kidneys from the organ donor
what are the disadvantages of a kidney transplant?
can be rejected
long waiting list
surgery
what are the advantages of a kidney transplant?
the only cure for kidney failure
cheaper for the nhs
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 maturation of eggs
what is the main male reproductive hormone?
testosterone which is produced by the testes, it also controls sperm production
what is the main female reproductive hormone?
oestrogen which is produced in the ovaries, it is involved the menstrual cycle
what is the menstrual cycle?
a monthly cycle of changes that occur in females
what are the events of the menstrual cycle?
day 1) uterus lining breaks down for around 4 days
day 4-14) uterus lining builds up again
day 14) an egg develops and released (ovulation)
day 14-28) wall is maintained and cycle begins again unless the egg is fertilised
what is ovulation?
the release of a mature egg from the ovaries which occurs at day 14 (approximately)
what are the hormones involved in the menstrual cycle?
oestrogen
progesterone
follicle stimulating hormone FSH
luteinising hormone LH
what is the role of oestrogen in the menstrual cycle?
produced by the ovaries and released due to the action of FSH: causes regrowth of uterus lining
stimulates the production of LH and restricts the release of more FSH
what is the role of FSH in the menstrual cycle?
produced by pituitary gland: it controls the maturation of eggs within the ovaries
triggers the production of oestrogen by the ovaries
what is the role of LH in the menstrual cycle?
produced in the pituitary gland as a result of oestrogen
triggers ovulation
what is the role of progesterone in the menstrual cycle?
produced from the follicle of the ovary: it sustains the uterus lining
inhibits FSH and LH
what is contraception?
any method that prevents pregnancy
how does the contraceptive pill prevent pregnancy?
inhibits FSH production so no eggs mature
prevents development of uterus lining
increases thickness of cervical mucus: immobilises sperm cells
how does the injection, implant and patch prevent pregnancy?
they have a slow release of progesterone to inhibit the maturation and release of eggs for a number of months or years
how do barrier methods prevent pregnancy?
condoms and diaphragms prevent the sperm from reaching the egg
what is the IUD?
a small copper containing device which is inserted into the uterus which prevents the implantation of embryos
what is spermicide?
a chemical that kills or immobilises sperm cells which is usually paired with barrier methods as they aren’t very effective
what are the surgical methods of contraception?
sterilisation
in males: sperm ducts are tied (vasectomy)
in females: oviducts are tied
what is abstinence?
the practice of not having sex
how do fertility drugs increase the chance of pregnancy?
drugs that contain FSH to stimulate oestrogen production and the maturation of eggs within the ovary
they also contain LH which triggers ovulation
what is IVF?
mother is given FSH and LH to stimulate maturation of eggs and ovulation
eggs are fertilised using sperm in a lab
these develop into embryos
1 or 2 embryos are inserted into mothers womb
what are the advantages of fertility treatment?
allows infertile couples to have children
can store women’s eggs for later
what are the disadvantages of fertility treatment?
very expensive process
low success rate
increase change of multiple pregnancies (dangerous)
side effects
what is negative feedback?
a type of control where the body responds to increase/decrease in a factor by returning it back to optimum level
how is the release of thyroxine controlled by negative feedback?
receptors in the brain detect levels of blood thyroxine falling
pituitary gland releases more TSH
more thyroxine produced and released by thyroid gland
blood thyroxine levels return to normal
what are the effects of adrenaline?
increase in heart and breathing rate: delivers oxygen and glucose to the body
glycogen converted into glucose
dilation of pupils
increased mental awareness
blood diverted away from digestive system to muscle
why do plants produce hormones?
to coordinate and control growth and responses to light
what does unequal distribution of auxins?
unequal growth rates in plant roots and shoots
why are gibberellins important?
initiating seed germination
what does ethene control?
cell division and ripening of fruits
where are plant growth hormones used?
agriculture and horticulture
what are auxins used for?
weed killers
rooting powders
promoting growth in tissue to control
where is ethene used?
in the food industry to control ripening of fruit during storage and transport
what are gibberellins used for?
end seed dormancy
promote flowering
increase fruit size
what is gravitropism?
response of plants shoot or root to gravity
what is an auxin?
a hormone which controls the growth of plants shoots and roots
when auxin is unevenly distributed in a growing plant the rate of growth will be unequal
