B5 - homeostasis Flashcards
homeostasis
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external stimuli
3 things regulated by homeostasis
- regulation of blood glucose concentration
- regulation of body temperature
- regulation of water levels
automatic control systems
the process by which the body maintains conditions of the internal environment
order of automatic control system
- receptors - detect stimuli and send information to cc
- coordination center - process information and organise response
- effectors - produce response to return condition to optimum (either chemical or nervous)
receptors
detect stimuli and send information to coordination centers
coordination centers
- located in brain spinal chord and pancreas
- process information and coordinate a response
effecters
- produce response to return conditions to optimum
- either a chemical response ( hormones secreted from glands) or nervous response (electrical impulses causing muscle contraction)
what does thyroxine do
thyroxine is a hormone that uses negative feedback to regulate metabolism
what does adrenaline cause and does it use negative feedback
Adrenaline is a hormone that triggers a ‘fight or flight‘ response and is not controlled by negative feedback.
how do negative feedback cycles work
They work by detecting and counteracting changes in bodily conditions
what causes the negative feedback CYCLE
Effectors continue producing responses as long as they are stimulated by coordination centres which means it is common for the level to be increased/decreased too much. In these cases, negative feedback begins again in the opposite direction.
3 things
what does thyroxine do
- it controls metabolism.
- regulates the speed of chemical reactions when at rest (basal metabolic rate)
- controls growth and development by stimulating protein synthesis.
where is TSH released
Thyroid stimulating hormone (TSH) is released from the pituitary gland
what does TSH do
stimulates the thyroid gland to release thyroxine.
how are thyroxine levels regulated
(in terms of hormones)
When thyroxine levels are too high, the secretion of TSH is restricted reducing the amount of thyroxine released from the thyroid gland.
When thyroxine levels become too low, the secretion of TSH is increased, increasing the amount of thyroxine released from the thyroid gland.
how is adrenaline secreted
Fear and stress are detected by the brain which sends nervous impulses to the adrenal glands which start secreting adrenaline.
what happens after adrenaline is secreted (what does ot cause)
Adrenaline triggers systems that will increase the delivery of oxygen and glucose to the brain and muscles, e.g. increasing heart rate, increasing breathing rate, This prepares the body so it is able to respond quickly in dangerous situations.
purpose of homeostasis
Homeostasis maintains optimal conditions for enzyme action and all cell functions
how is body temperature monitored and controlled
Body temperature is monitored and controlled by the thermoregulatory centre in the brain.
inthe thermoregulatory center
how is body temperature monitored and controlled
The thermoregulatory centre contains receptors sensitive to the temperature of the blood.
how does the skin monitor body temperature
The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre
2
how does the skin react when body temperature is too high
- blood vessels dilate (vasodilation)
- sweat is produced from the sweat glands.
- Both these mechanisms cause a transfer of energy from the skin to the environment.
3
how does the skin react when the body temperature is too low
If the body temperature is too low,
* blood vessels constrict (vasoconstriction),
* sweating stops
* skeletal muscles contract (shiver).
what is vasoconstriction
when blood vessels constrict due to low body temperature
what is vasodilation
when blood vessels dilate due to high body temperatures
what is the endocrine system
The endocrine system is composed of glands which secrete hormones directly into the bloodstream.
how do hormones travel to organs around the body
The blood carries the hormone to a target organ where it produces an effect.
compared to the nervous system how fast is the endocrine system and how long does it last
Compared to the nervous system the effects are slower but act for longer.
compared to the endocrine system how fast is the nervous system and how long does it last
the effects are faster but dont last as long
what is the pituitary gland
The pituitary gland in the brain is a ‘master gland’ which secretes several hormones into the blood in response to body conditions.
what do hormones released from the pituitary glands do
These hormones act on other glands to stimulate other hormones to be released to bring about effects.
where are the coordination centers located
located in brain ,spinal chord and pancreas
what is a chemical effector response
hormones secreted from glands
what is a nervous effector response
electrical impulses causing muscle contraction
where is thyroxine secreted
thyroid gland
purpose of the nervous system
The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
Where is information passed in the nervous system? and how does it get there?
Information from receptors passes along cells (neurones) as electrical impulsesto the central nervous system (CNS).
What is the central nervous system composed of?
The CNS is the brain and spinal cord.
2
what response does the central nervous system coordinate through the effectors?
The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
Recall the reflex arc.
Stimulus –> receptor –> coordinator –> effector –> response
Recall the 3 types of neurones found in the reflex arc.
Sensory neurone, Relay neurone and Motor neurone.
Describe reflex actions.
Reflex actions are automatic and rapid; they do not involve the conscious part of the brain.
three
Describe the function of the brain.
The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.
What have neuroscientists so far achieved? And how?
Neuroscientists have been able tomap the regions of the brain to particular functions by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques.
Why is the brain difficult to study?
The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult.
Describe the function of the eye.
The eye is a sense organ containing receptors sensitive to light intensity and colour.
Define Accommodation
Accommodation is the process of changing the shape of the lens to focus on near or distant objects.
four points
Describe the actions of the eye when it focuses on a near object.
To focus on a near object:
* the ciliary muscles contract
* the suspensory ligaments loosen
* the lens is then thicker and refracts light rays strongly.
Describe the actions of the eye when it focuses on a distant object.
To focus on a distant object:
* * theciliary muscles relax
* the suspensory ligaments are pulled tight
* the lens is then pulled thin and only slightly refracts light rays.
Explain the 2 common defects of the eye.
Two common defects of the eyes are
myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina.
How are defects of the eye treated usually
Generally these defects are treated with spectacle lenses which refract the light rays so that they dofocus on the retina.
three
How are defects of the eye treated using new technology?
New technologies now include
* hard and soft contact lenses,
* laser surgery to change the shape of the cornea and
* a replacement lens in the eye.
Recall where body temperature is monitored and controlled?
Body temperature is monitored and controlled by the thermoregulatory centre in the brain.
Explain how body temperature is monitored and controlled?
The thermoregulatory centre contains receptors sensitive to the temperature of the blood.
Describe the endocrine system.
The endocrine system is composed of glands which secretechemicals called hormones directly into the bloodstream.
How is blood glucose monitored and controlled?
Blood glucose concentration is monitored and controlled by the pancreas.
How does the pancreas react to high glucose concentrations in the blood?
If the blood glucose concentration is too high, the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells.
what does insulin do
- secreated from the pancreas
- causes glucose to move from blood into cells
Recall what happens to excess blood glucose.
pancreas secretes insulin which binds to receptor on liver and muscle cells causing excess glucose to be converted to glycogen for storage.
Describe type 1 diabetes.
Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections.
Describe type 2 diabetes.
In Type 2 diabetes the body** cells no longer respond to insulin produced by the pancreas**. A carbohydrate controlled diet and an exercise regime are common treatments. Obesity is a risk factor for Type 2 diabetes.
How does the pancreas react to low glucose concentrations in the blood?
If the blood glucose concentration is too low, the pancreas produces the hormone glucagon that binds to liver cells and causes glycogen to be converted into glucose and released into the blood.
what is glucagon
a hormone produced in the pancreas if there is insufficient glucose - it converts glycogen into glucose
How does water leave the body via the lungs?
Water leaves the body via the lungs during exhalation.
Which substances are lost in sweat?
Water, ions and urea are lost from the skin in sweat.
State the level of control in the loss of substances.
There is no control over water, ion or urea loss by the lungs or skin.
How are excess substances removed from the body?
Excess water, ions and urea are removed via the kidneys in the urine.
Describe what happens to body cells if there is an inbalance of water.
If body cells lose or gain too much water by osmosis they do not function efficiently.
What is the result of the digestion of proteins?
The digestion of proteins from the diet results in excess amino acids which need to be excreted safely.
Describe how amino acids are removed in the body.
In the liver these amino acids are deaminated to form ammonia.
Describe how ammonia is removed in the body.
Ammonia is toxic and so it is immediately converted to urea for safe excretion.
Describe the function of the kidneys.
The kidneys produce urine by filtration of the blood and selective reabsorption of useful substances such as glucose, some ions and water.
How are water levels controlled in the body?
The water level in the body is controlled by the hormone ADH which acts on the kidney tubules.
Explain the action of ADH in the body.
ADH is released by the pituitary gland when the blood is too concentrated and it causes more water to be reabsorbed back into the blood from the kidney tubules. This is controlled by negative feedback.
Why do doctors use kidney dialysis?
People who suffer from kidney failure may be treated by organ transplant or by using kidney dialysis.
Recall the function of reproductive hormones.
During puberty reproductive hormones cause secondary sex characteristics to develop
Describe Oestrogen.
Oestrogen is the main female reproductive hormone produced in the ovary.
Describe Ovulation.
At puberty eggs begin to mature and one is released approximately every 28 days. This is called ovulation.
Describe Testosterone.
Testosterone is the main male reproductive hormone produced by the testes and it stimulates sperm production.
Describe Follicle Stimulating Hormone.
Follicle stimulating hormone (FSH) causes maturation of an egg in the ovary.
Describe Luteinising Hormone.
Luteinising hormone (LH) stimulates the release of the egg.
Describe the functions of oestrogen and progesterone.
Oestrogen and progesterone are involved in maintaining the uterus lining.
How can fertility be controlled?
(Two types of contraceptive)
Fertility can be controlled by a variety of hormonal and non-hormonal methods of contraception.
Describe oral contraceptives.
Oral contraceptives contain hormones to inhibit FSH production so that no eggs mature.
Describe injection, and implants contraceptives
Injection, implant or skin patch of slow release progesterone to inhibit the maturation and release of eggs for a number of months or years
Describe barrier methods of contraception
Barrier methods such as condoms and diaphragms which prevent the sperm reaching an egg
Describe Intrauterine devices.
Intrauterine devices which prevent the implantation of an embryo or release a hormone
Describe Spermicidal agents.
Spermicidal agents kill or disable sperm.
Describe traditional forms of contraception.
- Abstaining from intercourse when an egg may be in the oviduct.
- Surgical methods of male and female sterilisation.
4 stages
Explain IVF.
In Vitro Fertilisation (IVF) treatment.
- IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs.
- The eggs are collected from the mother and fertilised by sperm from the father in the laboratory.
- The fertilised eggs develop into embryos.
- At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus(womb).
Recall the disadvantages of IVF.
Although fertility treatment gives a woman the chance to have a baby of her own:
- it is very emotionally and physically stressful
- the success rates are not high
- it can lead to multiple births which are a risk to both the babies and the mother.
Describe Adrenaline.
EQ-3
Adrenaline is produced by the adrenal glands in times of fear or stress.It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’.
Describe Thyroxine.
EQ-3
Thyroxine from the thyroid gland stimulates the basal metabolic rate. It plays an important role in growth and development. Thyroxine levels are controlled by negative feedback.
Why do plants produce hormones?
Plants produce hormones to coordinate and control growth and responses to light (phototropism) and gravity (gravitropism or geotropism).
State a disadvantage of unequal distribution of auxin.
Unequal distributions of auxin cause unequal growth rates in plant roots and shoots.
Describe the importance of Gibberellins.
Gibberellins are important in initiating seed germination.
Describe the importance of Ethene.
Ethene controls cell division and ripening of fruits.
what is a tropism
a response of a plant to a specific stimulus
phototropism
the response of a plants shoot or root to light
gravitropism
a response of a plants shoot or root to gravity
auxin
- the hormone that controls the growth of a plants 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 light causing auxin to move to the other side
- at the shaded side the cells are stimulated to grow so the shoot bends towards the light
- as a result photosynthesis can occur at a faster rate
how do plant shoot s show negative gravitropism
- in a horizontal shoot auxin accumulates in the lower side due to gravity
- cells on the lower side of the shoot grow more causing the shoot to bend away from the direction of gravity
- as a result more light is usually availible for photosynthesis
how do plant roots show positive gravitropism
- in a horizontal root auxin accumulates on the lower side causing cells to grow less
- the root bends in the direction of gravity
- as a result more water and nutrients are availible for the plant roots
difference between positive and negative gravitropism
- negative gravitropism causes shoots to bend away from direction of gravity
- positive gravitropism causes roots to bend in the direction of gravity
3
uses of auxins
- weedkillers - causes cells to grow at a rapid rate causing plant death
- rooting powder - causes new plants to grow very quickly
- tissue culture - promotes growth of roots and shoots
1
uses of ethene
control of food ripening in food industry - allows fruits to be ripened right before they are sold
3
uses of giberellins
- termination of seed dormancy
- promotion of flowering
- increase of fruit size
role of pituitory gland in endocrine system
- secretes human growth hormone - controls growth
- stimulates thyroid gland
- stimulates ovulation and production of eogestrogen in ovaries
- stimulates production of sperm and testosterone in testes
role of thyroid gland in endocrine system
secretes thyroxin which controls metabolism heart rate and body temperature
what is the role of ovaries in the endocrine system
secretes eostrogen which coordinates menstraul cycle and the development of female secondary sexual characteristics
role of testes in endocrine system
secretes testosterone which coordinates production of sperm and secondary sexual characteristics for males
