What is 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 changes
What for homeostasis do?
Maintains optimum conditions for enzyme action and all cell functions
What is controlled by homeostasis in the human body?
Blood glucose concentration
Body temperature
Water levels
What could automatic systems involve?
Nervous responses
Chemical responses
What do all control systems include?
Stimulus Cells called receptors Coordination centres Effectors Response
Why must the water content of the body be controlled?
High water concentration in the body leads to high blood pressure
We need water for transport between cells and within cells
Too little water means solutions will be too concentrated
How is the water content of the body controlled?
Kidneys filter excess water, and you store in the bladder and then you excrete it, through urine
Why must the ion content of the body be controlled?
Ions such as Na+, K+ and Cl- are in the blood
Too many ions make high blood pressure due to water in the blood through osmosis
How is the ion content of the body controlled?
Kidneys filter excess ions through urine
Why must the temperature of the body be controlled?
Enzymes in the human body only work well when at optimum temperature, 37 degrees
How is temperature controlled?
If you are too cold you shiver and also vasoconstriction occurs which keeps blood in core so you go pale
If you are too hot vasodilation occurs which lets blood into skin layers and you go red also you sweat
Why must blood sugar levels be controlled?
Affects osmotic relations of cells
When there is too little sugar, more water will enter cells via osmosis
When there is too much sugar more water will leave cells via osmosis
How are blood sugar levels controlled?
Insulin
Why must carbon dioxide concentration of the blood?
When CO2 is added to water it makes weak carbonic acid
pH will drop and enzymes work best at optimum pH
How is carbon dioxide concentration of the blood controlled?
Increase breathing rate and depth to get all the co2 out of the lungs.
What does the nervous system allow humans to do
React to their surroundings and to coordinate their behaviour
What wakes up the CNS
The brain
Spinal chord
What does the CNS do?
Coordinates the response of effectors which may be muscles contracting or glands secreting hormones
Complete this flow chart
Stimulus —>______—>_______—> ______ —> _____—>response
Stimulus Receptor Coordination centre Effector Response
What happens to the effector in the case of negative feedback?
In negative feedback the effector opposes the change and pushes the variable back to set point value
What does the peripheral nervous include?
All other nerves that radiate from the brain and spinal chord.
What are nerve fibres?
A bundle of nerve cells called neurones
How are nerve cells adapted?
Axon is long, allows electrical impulses to pass through the body
Dendrites allow them to connect with other nerve cells
Myelin sheath insulates cells. It’s made of fatty material so is a good insulator
What is a reflex action?
Quick automatic responses to stimuli, often designed to protect the body from harm
Name the three types of neurone in the reflex arc
Sensory
Motor
Relay
What does the sensory neurone do?
Transmits impulses from the receptor to the coordinator
What does the relay neurone do?
Found in CNS it transmits impulses from the sensory to the motor neurone
What does the motor neurone do?
Transmits impulses from the relay to the effector
What does the thermoregulatory centre in the brain do?
Monitors and controls body temperature
Has receptors that monitor the temperature of the blood flowing through the brain
Received information from temperature receptors inn the skin
What happens if the body temperature is too high?
Blood vessels widen, directing more blood to the surface of the skin this is called vasodilation
More sweat is produced from the sweat glands and evaporates
Both these machinists cause a transfer of energy form the skin to the environment
What happens if the body temperature is too low?
Blood vessels narrow, directing blood away from the surface of the skin this is called vasoconstriction
Sweating stops
Skeletal muscles uncontrollably contract and relax quickly causing you to shiver, which transfers more heat to the blood
What does the brain control?
Complex behaviour
What does the brain include?
Cerebral cortex, cerebellum and medulla
It is made up of billions of interconnected neurone and has different regions that carry out different functions
How have neuroscientists been able to map the regions of the brain to particular functions?
Studying patients with brain damage
Electrically stimulation get different parts of the brain
Using MRI scanning techniques
Why is studying the brain so hard?
Complexity and delicacy of the brain
What is the eye?
Sense organ
What is the retina?
Contains receptor cells that are sensitive to the brightness and colour of light
What is the optic nerve?
Carries impulses from the retina to the brain
What is the sclera?
forms a tough outer layer, with a transparent region at he front called the cornea
What is the iris?
Controls the size of the pupil and the amount of light reaching the retina
What are the ciliary muscles and suspension ligaments?
Change the shape of the lens to focus light onto retina
What is accommodation?
The process of changing the shape of the lens to focus on near or distant objects
What is myopia?
Short sightedness
What is hyperopia?
Long sightedness
How are eye defects treated?
Spectacle lenses which refract the light rays so that they focus on the retina
Name new technologies that treat eye defects
Contact lenses
Laser surgery to change shape of cornea
Replacement eye lenses
What is the endocrine system made up of?
Glands that secrete hormones directly into the bloodstream
What are hormones?
Chemical messengers that are carried in the blood to target organ where they produce an effect
What is the pituitary gland?
In the brain is a ‘master gland’
What does the pituitary gland do?
Secrets several hormones in response to body conditions
What is adrenaline?
Produced by the adrenal glands in times of fear or stress
Increase the heart rate, boosting the delivery of oxygen and glucose to the brain and muscles
Prepares the body for ‘flight or fight’
What is thyroxine?
Produced by the thyroid gland
Increase metabolic rate
Controls growth and development in young animals
Is controlled by negative feedback
What controls and monitors blood glucose concentration?
Pancreas
What happens if blood glucose is too high?
The pancreas releases more of the hormone insulin
Insulin causes glucose to move from the blood into cells
In liver and muscle cells, excess glucose is converted to glycogen for storage
What happens if blood glucose concentration is too low?
The pancreas releases glucagon
Glucagon stimulates glycogen to be converted into glucose and released into the blood
What is type 1 diabetes?
Caused by the pancreas failing to produce sufficient insulin
Results in uncontrolled high blood glucose levels
Normally treated with insulin injection
What is type 2 diabetes?
Caused by the body cells no longer responding to insulin
Has obesity as a risk factor
Treated with a carbohydrate controlled diet and regular exercise
How does water leave the body?
From the lungs during breathing, from the skin in sweat and in urine
What happens if the concentration of he blood changes?
Body cells will lose or gain too much water by osmosis
What regulates balance of water and ions in the body?
The kidneys
What is urea?
A waste product that is produced by the liver from the breakdown of proteins and contains nitrogen
What did the kidneys excrete?
Urea
What does the digestion of proteins from food result in?
Excess amino acids
What does the liver convert amino acids into?
Ammonia
What is the process called in which excess amino acids are converted into ammonia?
Deamination
Why is ammonia immediately converted to urea and sent to the kidneys for safe excretion?
It is toxic
How do the kidneys produce urine?
Filter the blood
Selective reabsorption of useful substances, such as glucose, some ions and water
This leaves unread and excess water and ions to form urine
Where does the process of selective reabsorption take place?
Millions of small tubes in the kidneys called tubules
What hormone controls the water level in the body?
ADH
When is ADH released by the pituitary gland?
When the blood is too concentrated
What does ADH do to the body?
It passes,in the blood, to the kidney tubules where it causes more water to be reabsorbed back into the blood
How can people with kidney failure be treated?
Organ transplant or dialysis
What is dialysis?
A dialysis machine gage over the role of the kidneys, it is used to remove waste products from the blood, three times a week
Where is the thyroid gland?
In the neck
Where is insulin made?
In the pancreas
What is urea?
A ware product from the breakdown of proteins containing nitrogen
If a person drinks a litre of water what effect will this have in ADH release?
It will reduce the release of ADH
What is the female sex hormone?
Oestrogen from the ovaries
What is ovulation?
When eggs begin to mature and be released
What is the main male sex hormone?
Testosterone
Where is testosterone produced?
Testes
What does testosterone do?
Stimulates sperm production
What does FSH stand for?
Follicle stimulating hormone
What is FSH secreted by?
Pituitary gland
What is the function of FSH in the menstrual cycle?
Causes eggs to mature in the ovaries
Stimulates ovaries to produce oestrogen
What is oestrogen secreted by?
Ovaries
What is the function of oestrogen in the menstrual cycle?
Inhibits FSH release
Stimulates LH release
Make lining of uterus grow again after menstruation
What does LH?
Luteinising hormone
What is LH secreted by?
Pituitary gland
What is the function of LH in the menstrual cycle?
Stimulates the release of the egg from the ovary (ovulation)
What is progesterone secreted by?
Empty follicle in the ovaries
What is the function of progesterone in the menstrual cycle
Maintains lining of uterus during second half of cycle
Inhibits both FSH and LH release
How can fertility be reduced?
Contraception
LH is does the combined pull reduce fertility?
Contains oestrogen and progesterone which inhibit FSH so no eggs are released
How does an injection, implant or skin patch reduce fertility?
Slow release of progesterone to stop release of eggs
How do condoms and diaphragms (barrier methods) reduce fertility?
Prevent spent from reaching the egg
How do intrauterine devices reduce fertility?
Prevent embryos form implanting in the uterus
What do spermicidal creams do to sperm?
Kill or disable sperm
What surgical methods are available to reduce fertility?
Cutting sperm ducts or tying Fallopian tubes
What can doctors give to a woman if her own level of FSH is too low?
FSH and LH in a fertility drug
What does In vitro fertilisation involve?
- giving a woman FSH and LH to stimulate the growth of many eggs
- collecting the eggs from the woman
- fertilising the eggs with sperm from the father in the laboratory
- inserting one or two embryos into the woman’s uterus
What are the disadvantages of fertility treatment?
- It is 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
What is a tropism?
When part of a plant responds by growing in a particular direction
How do shoots react to the stimulus gravity?
Away= negatively geotropic/ gravitropic
How do roots respond to the stimulus gravity?
Towards = positively gravitropic/ geotropic
How do shoots respond to the stimulus light?
Towards= positively phototropic
How does the growth of roots respond to the stimulus light?
Away = negatively phototropic
What are tropisms controlled by?
A group of plant hormones called auxins
Describe a plants response to light compared to roots through auxins
More light reaches one side of the shoot
More auxin is sent down the shaded side of the shoot
This results in cells on the shaded side elongating more
The shoot therefore, grows towards the light
In roots auxin moves to the bottom of the root and causes less elongation so the roots grow downwards
What are gibberellins?
A group of plant hormones and are important in initiating seed germination
What is ethane in plants?
A plant hormone. It controls cell division and ripening of fruits
How are auxins used by farmers and gardeners?
As weed killers , auxins make the weeds grow so rapidly that they use up their food reserves and die
As rooting powders
Promoting growth in tissue culture
How is ethene used in industry?
Control the ripening of fruits
How are gibberellins used by farmers and gardeners?
End seed dormancy and make seeds germinate
Promote flowering, so that plants flower when there is most demand e.g. Mother’s Day
Increase fruit size
