Topic 5 - Homeostasis And Response Flashcards
What is the brain responsible for?
Complex behaviours
Whoa is the Brian made up of?
Billions on interconnected neurones and has different regions that carry out different functions
What is the cerebral cortex?
Outer wrinkly bit - responsible for consciousness, intelligence, memory and language
What is the medulla?
Attached to spinal cord - controls unconscious activities (like breathing and your heartbeat)
What is the cerebellum?
At the back of your brain at the bottom - responsible for muscle coordination
How do scientists study the brain and work out which bits do what?
Studying patients with brain damage
Electrically stimulating the brain
MRI scans
What makes investigating the brain difficult?
It is complex and delicate
What is 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 does homeostasis do?
Maintains optimal conditions for enzyme action all functions
What does homoeostasis control in the human?
Blood glucose concentration
Body temperature
Water levels
Give two examples of automatic control systems?
Nervous responses chemical responses
What do all control systems include?
Receptors
Coordination centres
Effectors
What is a receptor?
Cells which detect stimuli (changes in environment)
What are coordination centres?
They receive and process information from the receptors
Give examples of coordination centres?
Brain
Spinal cord
Pancreas
What is an effector?
Muscles or glands which bring about responses which restore optimum levels
How do automatic control systems keep your internal environment stable?
Using a mechanism called negative feedback
What does the nervous system enable humans to do?
React to their surroundings and coordinate their behaviour
Give examples of receptors
Taste receptors on tongue
Sound receptors in ears
How do muscles and glands respond to information?
Muscles contract
Glands secrete hormones
What happens to information from receptors?
It passes along cells called neurones as electrical impulses
Where are the electrical impulses from receptors sent?
The central nervous system
What is the central nervous system?
- In vertebrates this consists of the brain and spinal cord
- In mammals it is connected to the body by sensory and motor neurons
What does the central nervous system do?
Coordinates the response of effectors
What is the order in which a nervous impulse travels?
1) stimulus
2) receptor
3) coordinator
4) effector
5) response
What are reflex actions?
Automatic and rapid actions that do not involve the conscious part of the brain
What is a synapse?
The connection between two neurons
How is the nerve signals transferred through the synapse?
It is transferred by chemicals which diffuse (move) across the gap and the chemicals set off a new electrical signal in the next neurone
What is stage one of the reflex arc?
A stimulus (a bees sting) is detected by receptors
What is stage two of the reflex arc?
Impulses are sent along a sensory neurone
What is stage three of the reflex arc?
The impulses reach a synapse between the sensory neurone and the relay neurone and trigger chemicals to be released
What is stage four of the reflex arc?
The impulses pass along the relay neurone in the CNS
What is stage five of the reflex arc?
The impulse reaches a synapse between the relay neurone and a motor neurone and chemicals are released
What is stage six of the reflex arc?
The impulses travel along the motor neurone to the effector which contracts as a response
Why is the reflex arc quicker than normal responses?
You don’t have to think about the response
how can you measure reaction time?
Ruler drop test
Computer
How do you test reaction time using a computer?
The person being tested has to click the mouse as soon as they see a stimulus on the screen
What are the benefits of using computers to test reaction time
- Give more precise readings as they remove the possibility of human error
- Record time in milliseconds so it is more accurate
What is the Sclera?
Tough supporting wall
What is the cornea
Transparent outer layer found it front of eye that refracts light
What is the iris?
Contains muscles that allow it to control diameter of the pupil and therefore how much light enters the eye
(Cover edges of lens just in-front)
What is the pupil?
The hole in the middle
What is the lens?
Focuses light onto the retina
Behind the pupil
What is the retina?
Contains receptors cells sensitive to light intensity and colour
(At back of eye)
What do the ciliary muscles and suspensory ligaments do?
Control the shape of the lens
Top (suspensory) and bottom (ciliary) of lens
What is the optic nerve?
Carries impulses from the receptors on the retina to the brain
(Back and bottom of eye ball)
What is the eye?
Sense organ containing receptors sensitive to light intensity and colour
What are the functions of the eye the relate to it’s structure?
Accommodation to focus on near or distant objects
Adaptation to dim light
What is accommodation in the eye?
The process of changing the shape of the lens to focus on near or distant objects
How does the eye focus on a near object?
- The ciliary muscles contract
- The suspensory ligament loosen
- The lens is then thicker and refracts light rays strongly
How does the eye focus on a distant object?
- The ciliary muscles relax
- The suspensory ligament are pulled tight
- The lens is then pulled thin and only slightly refracts light rays
What are two common defects of eyes?
Myopia (short sightedness)
Hyperopia (long sightedness)
Why do the defects of eyes happen?
Rays of light do not focus on the retina
How are the defects of eyes treated?
Spectacle lenses which refract the light rays so that they focus on the retina
What are the new technologies to treat eye defects?
- Hard and soft contact lenses
- Laser surgery to change the shape of the cornea
- Replacement lens in the eye
What is the iris reflex?
Adjusting the eye for bright light
How does the iris reflex work in bright light?
A reflex is triggered that makes the pupil smaller
The circular muscles in the iris contract and the radial muscles relax to reduce the amount of light that can enter the eye
How does the iris reflex work in dim light?
The radial muscles contract and the circular muscles relax making the pupil wider
When does long sightedness occur?
When the lens is the wrong shape and doesn’t refract the light enough or when the eyeball is too short
What happens to the light rays in long sighted eyes?
The images of new objects are brought into focus behind the retina
How can you correct long sightedness?
Using glasses with a convex lens
When does short sightedness occur?
When the lens is the wrong shape and refracts light too much or when the eyeball is too long
What happens to the light rays in short sighted eyes?
The images of distant objects are brought into focus in front of the retina
How can you correct shortsightedness?
Using glasses with a concave lens
What are the advantages of contact lenses?
Convenient, light weight and almost invisible
What are the two types of contact lenses and which is better?
Hard lenses and soft lenses
Soft lenses are more comfortable but carry a higher risk of eyes infections
What is laser eye surgery?
Laser is used to vaporise tissue, changing the shape of the cornea - slimming it down makes it less powerful and can improve short sight
What are the advantages of laser eye surgery?
The surgeon can precisely control how much tissue the laser takes off
What are the disadvantages of laser eye surgery?
There is a risk of complications such as infection or the eye reacting to make your vision worse than before
What is replacement lens surgery?
The natural lens of the eye is removed and an artificial lens, made of clear plastic, is inserted in its place
What are the disadvantages of replacement lens surgery?
Carries higher risk than laser eye surgery as it involves work inside the eye including possible damage to the retina and blindness
How is body temperature monitored and controlled?
By the thermoregulatory centre in the brain
What does the thermoregulatory centre contain?
Receptors sensitive to temperature of the blood
How does the thermoregulatory centre receive information?
The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre
What happens if the body temperature is too high?
Blood vessels dilate (vasodilation) and sweat is produced from the sweat glands - transferring energy from the skin to the environment
What happens if the body temperature is too low?
Blood vessels constrict (Vasoconstriction),sweating stops, hairs snags up to trap an insulating layer of air and skeletal muscles contract (shiver)
What is the endocrine system?
Composed of glands which secrete chemicals called hormones directly into the bloodstream
What are hormones?
Chemical molecules released directly into the blood
How are hormones transported around the body?
The blood carries the hormone to the target organ where it produces an effect
What do hormones do?
Control things in organs and cells that need constant adjustment
Where are hormones produced?
Various glands called endocrine glands
Compare hormones and nerves?
- Nerves are very fast but act for a short time in a precise area
- hormones have slower actions but act for a long time in a more general way
What is the pituitary gland?
The master gland in the brain which secretes several hormones that regulate body conditions, these hormones act on other glands and direct them to release hormones that bring about change
Where is the pancreas and what does it do?
- Produces insulin which is used to regulate the blood glucose level
- in front of kidneys
Where is the thyroid and what does it do?
- In the throat
- produces thyroxine which is involved in regulating things like the rate of metabolism, heart rate and temperature
Where is the adrenal gland and what does it do?
- Above/on top of the kidneys
- produces adrenaline which is used by the body for flight or fight response
Where are the ovaries and what do they do?
- in the lower abdomen connected to the uterus
- produce oestrogen, which is involved in menstrual cycle
Where are the testes and what do they do?
- The male ball sack
- produce testosterone which controls puberty and sperm production
What does the pancreas monitor and control?
Blood glucose concentration
How does the pancreas react 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
How do the liver and muscles aid the pancreas for blood glucose concentration?
Excess glucose is converted to glycogen storage
How does glucose get into the blood?
Eating food containing carbohydrates puts glucose into the blood from the gut
How can you remove glucose from the blood?
Normal metabolism of cells and vigourous exercise
What is the negative feedback cycle if the blood glucose level is too high?
The pancreas secretes insulin so did you close it moves from blood into the liver and muscle cells so blood glucose is reduced
What is the negative feedback cycle if the blood glucose level is too low?
The pancreas secrete glucagon so glucose is released into the blood by liver (as glucagon enters liver) and blood glucose is increased
What does insulin in the liver do?
Turns glucose into glycogen
What does glucagon in the liver do?
Turns glycogen into glucose
What is type one diabetes?
A disorder in which the pancreas fails to produce sufficient insulin and uncontrolled high blood glucose
How can type one diabetes normally be treated ?
Insulin injections to make sure glucose is removed from blood quickly once food has been digested
- very effective
- amount depends on diet and activity levels
How can someone with type 1 diabetes help to prevent high blood glucose?
Limiting the intake of food which in simple carbohydrates and taking regular exercise
What is Type II diabetes?
When the body cells no longer respond the insulin produced by the pancreas
How can you treat Type II diabetes?
A carbohydrate controlled diet and exercise regime
What is a risk factor for Type II diabetes?
Obesity
How does water leave the body?
Via the lungs during exhalation
What is lost from the skin through sweat?
Water, ions and urea
Can you control water, ion or urea loss by the lungs or skin?
No
How are excess water, ions and urea removed?
Via the kidneys in urine
What happens if body cells lose or gain too much water by osmosis?
They do not function efficiently
What does the digestions of proteins from the diet result in?
Excess amino acid‘s which need to be extracted safely
What happens to amino acid in the liver?
They are deaminated to form ammonia which is toxic and is immediately converted to urea for safe excretion
What is deamination?
A process used to break down amino acid for energy
What do the kidneys do?
Produces urine by filtration of the blood and selective reabsorption of useful substances such as glucose, some ions and water
What is water level in the body controlled by?
The hormone ADH which acts on the kidney tubules
When is ADH released?
The pituitary gland releases it when the blood is too concentrated
What does ADH do?
It causes more water to be reabsorbed back into the blood from the kidney tubules controlled by negative feedback
How are people who suffer from kidney failure treated?
By organ transplant or using kidney dialysis
How does dialysis work?
In a dialysis machine The person’s blood flows between partially permeable membranes (for ions and waste substances e.g. small molecules) surrounded by dialysis fluid
How does the dialysis fluid work?
It has the same concentration of dissolved ions and glucose as healthy blood which means that useful dissolved ions and glucose won’t be lost only waste substances diffuse across the barrier
What are the advantages of dialysis?
Don’t have to wait for a donor
What are the disadvantages of dialysis?
- Regular unpleasant sessions which are 3 to 4 hours long
- expensive
- May cause blood clot or infections
What are the advantages of kidney transplants?
Cheaper and easier in the long run than dialysis
What are the disadvantages of kidney transplants?
- Can be rejected
- long waiting list‘s
During puberty what do reproductive hormones cause?
Secondary sex characteristics to develop
What is oestrogen?
The main female reproductive hormones produced in the ovaries
What is ovulation?
At puberty eggs begin to mature and one is released approximately every 28 days
What is testosterone?
The main male reproductive hormones produced by the testes
What does testosterone do?
Stimulate sperm production
Which hormones are involved in the menstrual cycle or a woman?
FSH
LH
oestrogen
Progesterone
What is FSH?
Follicle stimulating hormone that causes maturation of an egg in the ovary and stimulates ovaries to produce oestrogen
Produced in pituitary gland
What is LH?
Luteinising hormone that stimulates the release of the egg at day 14
Produced in pituitary gland
What do oestrogen and progesterone do in the menstrual cycle?
Maintain the uterus lining (when the level of progesterone falls, the lining breaks down)
Produced in ovaries
How do you oestrogen and progesterone effect the release of LH and FSH?
Oestrogen stimulates release of LH and inhibits release of FSH
progesterone inhibits release of LH and FSH
What is stage one of the menstrual cycle?
Menstruation starts and the uterus lining breaks down for about four days
What is stage two of the menstrual cycle?
uterus lining build up again from day 4 to14 into a thick spongy layer full of blood vessels ready to receive a fertilised egg
What is stage three of the mental cycle?
And egg develops and is released from the ovary at day 14 (ovulation)
What is stage four of the menstrual cycle?
The wall is then maintained for about 14 days until day 28, if no fertilised egg has landed on the uterus wall the spongy lining starts to break down
How can fertility be controlled?
A variety of hormonal and nonhormonal methods of contraception
What are the hormonal methods of contraception?
- Oral contraceptives that contain hormones
- injection, implant or skin patch
- intrauterine devices
What are the nonhormonal methods of contraception?
- Barrier methods
- spermicidal agents
- abstaining from intercourse
- surgical methods of sterilisation
What are oral contraceptives?
Contain hormones to inhibit FSH production so that no eggs mature
What is injection, implant or skin patch of progesterone?
Slow release progesterone to inhibit the maturation and release of eggs for a number of months or years
What are barrier methods?
Prevent the sperm reaching an egg such as condoms and diaphragms
What are intrauterine devices?
Prevent the implantation of an embryo or release of a hormone
What do spermicidal agents do?
Kill or disable sperm
When do you abstain from intercourse?
When an egg may be in the oviduct
What is sterilisation?
Cutting or tying the fallopian tube’s in a female or cutting or tying the sperm duct in a male
How do you do use of hormones in modern reproductive technologies treat infertility?
Giving FSH and LH in a fertility drug to a woman so that she can then become pregnant in the normal way
What is IVF?
In vitro fertilisation treatment involves giving a mother FSH and LH to stimulate the maturation of several eggs
What happens once the eggs have matured in IVF?
They are collected from the mother and fertilised by sperm from the father in the lottery so that the fertilised egg is developed into embryos
At what stage are the embryos inserted into the mothers uterus?
At the stage when they are tiny balls of cells, one or two embryos are inserted
What are the disadvantages of IVF?
- Very emotionally and physically stressful
- success rate are not high
- can lead to multiple births
When is adrenaline produced?
Produced in the adrenal grams in times of fear or stress
What does adrenaline do?
Increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles preparing the body for flight or fight
What is thyroxine?
A hormone produced in the thyroid gland that stimulates the basal metabolic rate and plays an important role in growth and development
How are thyroxine levels controlled?
By negative feedback
Why do plants produce hormones?
To coordinate and control growth and responses to light and gravity
What is phototropism?
Coordinating and controlling growth and responses to light
What is gravitropism/geotropism?
Coordinating and controlling responses to gravity
What causes unequal growth rates in plant roots and shoots?
Unequal distribution of auxin
What does ethene control?
Cell division and ripening of fruit
What do gibberellians do?
They are important in initiating seed germination
Where are plant growth hormones used?
Agriculture and horticulture
What are auxins used for?
- as weed killers
- as rooting powders
- promoting growth in tissue culture
How do auxins work as weed killers?
They disrupt their normal growth patterns which soon kills them whilst leaving the grass and crops untouched
How do auxins work as rooting powder?
Adding rooting powder to cuttings will produce roots rapidly and start growing as new plants enabling clones to grow very quickly
How do auxins work in tissue culture?
Adding them to growth mediums to stimulate the cells to divide and form both roots and shoots
How is ethene used in the food industry?
To control ripening of fruit during storage and transport
What can gibberellins be used for?
- to end seed dormancy
- to promote flowering
- to increase fruit size
How do gibberellins end seed dormancy?
They alter the conditions to allow seeds to germinate at times of year that they wouldn’t normally and helps all seeds in one batch to germinate at the same time
How do gibberellins induce flowering?
Allows plants to flower without any change in their environment and can be used to grow bigger flowers
