B5-Homeostasis and response Flashcards
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 does homeostasis in the human body control?
- Blood glucose concentration
- Body temperatures
- Water levels
What are the 3 features in a control system?
- Receptors
- Coordination centres
- Affectors
What are receptors?
Cells that detect changes in the internal or external environment known as stimuli
What is the function of coordination centres?
To recieve and process information from receptors around the body
What do effectors do?
Muscles or glands that bring about responses, which restore optimum levels
What 2 type of responses may occur during homeostasis?
- Nervous responses-nervous system
- Chemical responses-endocrine system
What does the central nervous system (CNS) consist of?
The brain and spinal cord
What is the part of nervous system that isn’t the CNS called?
The peripheral nervous system
Describe the way the nervous system works (5)
- Sensory receptor detects a stimuli
- Sensory neurons carry the electrical impulse to the CNS
- The electrical impulse is carried through the CNS through relay neurons
- The electrical impulse is carried by motor neurons after it leaves the CNS
- The electrical impulse reaches the effector
Give the sense organ for the following:
* Touch, temperature and pain
* Chemicals (in food and drink)
* Chemicals (in air)
* Light
* Sound and position of head
- Skin
- Tongue
- Nose
- Eye
- Ear
What are 2 specialised features of a neuron (nerve cell) and explain them?
- Axon-a long fibre which is insulated by a fatty myelin sheath-long so they can carry electrical messages up and down the body
- Dendron-Tiny branches which branch further as dendrites at each end-these recieve incoming impulses from other neurones
What are reflex actions?
Actions that are automatic and rapid and don’t involve the brain
Why are reflex actions necessary?
- By providing an automatic and rapid response to a stimulus this minimises any damage to the body from potentially harmful conditions.
- They also are reflexes that take care of your basic body functions such as breathing and digesting food
What does a reflex action not involve?
The conscious part of the brain
What are the stages of a reflex arc?
1) A receptor in the skin detects a stimulus
2) Sensory neurone sends electrical impulses to relay neurone, which are located in the spinal cord
3) Motor neurone sends electrial impulses to an effector
4) Effector produces a response
This whole pathway is a reflex arc
What are gaps between neurones called?
Synapses
What are synapses?
Gaps between nerves in which chemical messangers (neurotransmitters) diffuse across the synapse and bind with the receptor molecules on the membrane of the second neurone-this causes a second electrical imulse to be produced.
Fill in the gaps:
The receptor molecule on the second neurone bind only to the …………… neurotransmitters.
Specific
True of False:
An impulse also travels up the spinal cord to the concious areas of the brain
True-this happens so that you know about the reflex action
How do you carry out an investigation into the effect of a factor in human reaction times?
1)Person A holds their hands with a gap between their thumb and first finger
2)Person B holds the ruler with the sero at the top of person A’s thumb
3)Person B drops the ruler without telling person A who must catch it
4)The number lebel with the top of person A’s thumb is recorded in a suitable table
5)This experiment can be repeated with external factors such as noise
What are the 4 main areas of the brain?
- The cerebrum (outer layer called cerebral cortex)
- The cerebellum
- The medulla (oblongata)
- The hypothalamus
What does the cerebrum (cerebral cortex do)?
It controls intelligence, counsciosness, personality, memory and language
What does the cerebellum do?
It coordinates muscular activity, movement and balance
What does the medulla oblongata do?
It controls unconscious activities such as heart rate and breathing rate and gut movements
What does the hypothalamus do?
It is the regulating centre for temperature and water balance within the body
What is tough, white outer area of the eye called?
The sclera
What is the transparent region at the front of the sclera?
The cornea
What does the iris do?
It controls the size of the pupil and the amount of light entering the light
What do the ciliary muscles do?
They change the shape of the lens to focus light onto the retina
What carries impulses from the eyes to the brain?
The optic nerve
What is accommodation?
The process of changing the shape of the lens to focus on near or distant objects
How do we focus on close up objects?
By contracting the ciliary muscles loosening the suspensory ligaments
How do we focus on a far away objects?
By relaxing the ciliary muscles so the suspensory ligaments are pulled tight.
What is Myopia?
Short sightedness-seeing close objects in clear focus
What is Hyperopia?
Seing far away objects in clear focus
How can we treat myopia and hyperopia?
- Contact lenses
- Glasses
- Laser eye surgery
- Replacement lenses
What is the endocrine system?
A system composed of glands that secrete hormones directly into the blood stream-the blood carries the hormone to a target organ where it produces an affect.
What gland is know as the ‘master gland’
The pituitary gland
What are some key endocrine glands and what are their roles?
- Pituitary-controls growth in children, stimulates the thyroid gland to make thyroxine to control the rate of metabolism. Stimulates the adrenal glands to produce adrenaline. Stimulates the ovaries to produce and release eggs and make the female sex hormone oestrogen. Stimulates the testes to make sperm and the male sex hormone testosterone.
- Thyroid-Controls the metabolic rate of the body
- Pancreas-Controls the level of glucose in the body
- Adrenal-Prepares the body for stressful situations ‘fight or flight’ response.
- Ovaries-Controls the development of the female secondary sexual characteristics and is involved in the menstrual cycle
- Testes-controls the development of the male secondary sexual characteristics and is involved in the production of sperm
What hormones does the pancreas create?
- Insulin
- Glucagon
What is a storage carbohydrate found in the liver and muscles called?
Glycogen
What does insulin do?
It allows glucose to move from the blood into the cells to be stored as glycogen in the liver and muscles
What does glucagon do?
It makes the liver break down glycogen, converting it back into glucose
What is a negative feedback cycle?
It involves switching between 2 hormones to keep the body at equilibrium.
What is type 1 diabetes?
It is when your pancreas doesn’t make enough insulin so blood glucose concentrations aren’t controlled.
What is type 2 diabetes?
It is when your body cells stop responding to the insulin you make
How do you treat type 1 diabetes?
- By injecting insulin to replace the hormone that isn’t made in the body
- By being careful about the amount of carbohydrates you eat
How to you cure type 1 diabetes?
- By transplanting pancreases-however this is difficult to perform and risky as well as there being not enough pancreas doners.
- By transplanting the pancreatic cells that make insulin.
How can you treat type 2 diabetes?
- By eating a balanced diet and controlling the amount of carbohydrates
- By losing weight
- By doing regular exercise
- By taking drugs that improve the efficacy of insulin, that helps your pancreas make more insulin and reduce the amount of glucose you absorb from your gut
Does adrenaline involve a negative feedback loop?
No
What is the opposite hormone to thyroxine?
TSH
What does thyroxine play an important role in?
Growth and development
What are the effects of adrenaline?
- Heart and breathing rate increases
- Stored glycogen in the liver to be converted to glucose for respiration
- Pupils of your eyes to dilate to let in more light
- Mental awateness to increase
- Blood to be diverted away from you digestive system to skeletal muscles
What develops during puberty?
Secondaty sexual characteristics
What are the hormones involved with the menstrule cycle?
FSH, LH, Oestrogen, Progesterone
What is the full name of FSH and what does it do?
Follicle stimulating hormone-it causes the eggs in the ovary to mature
What is the full name of LH and what does it do?
Luteinizing hormone-it stimulates the release of the egg at ovulation
What does oestrogen and progesterone do?
Stimulate the build-up and the maintenance of the uterus lining
Describe the role of hormones in the menstrual cycle
1)FSH is secreted by the pituitary gland, starting egg maturation in the ovaries, stimulating the ovaries to produce oestrogen
2)Oestogen is made and stimulates the lining of the uterus to grow again after menstruation in preperation for pregnancy. High levels of oestrogen inhibit the production of more FSH and stimulate the release of LH
3)LH stimulates the release of a mature egg from the ovary-once ovulation happens LH levels fall again
4)Progesterone is secreted by the empty egg follicle after ovulation-helps to maintain a pregnancy if the egg is fertilised. It also inhibits both FSH and LH and maintains the lining og the uterus
5) If it is clear that the egg is not fertilised the levels of all the hormones drop and the lining of the uterus pulls away and is lost from the body
What are the different methods of contraception?
- Hormone-based contraception containing low doses of oestrogen along with progesterone to inhibit the production and release of FSH
- Hormone-based contraceptive pills contain only progesterone (less side effects), however they have to be taken very regularly.
- A contraceptive implant that releases progesterone is inserted under the skin
- A contraceptive patch containing a mixture of oestrogen and progesterone
- Spermicides to kill or disable sperm
- Barrier methods such as condoms or diaphragms
- Intrauterine devices-last for 3-5 years however they can be removed at any time-some contain copper or progesterone
- Abstinence
- Surgical methods such as a vasectomy or oviducts being tied
How is a lack of ovulation fixed?
By using artificial FSH and LH to stimulate and ovulate
How does IVF (in vitro fertilisation) work?
- Give the mother synthetic FSH to stimulate the maturation of a number of eggs, followed by LH
- They collect the eggs from the ovary of the mother and fertilise them with sperm from the father
- The fertilised eggs are kept in special solutions in a warm environment to develop into tiny embryos
- When the embryos divide up into a ball of cells, one or two of the embryos are inserted back into the uterus of the mother
What is the main advantage of IVF?
The mature eggs produced by a woman using fertility drugs may be collected and stored until she wants to get pregnant after.
What are the disadvantages of IVF?
- IVF is very expensive for society and individuals
- It is not always successful
- The use of fertility drugs can have some health risks for the mother and the process of IVF is very emotionally and physically stressful
- IVF increases the chance of multiple pregnancies which can lead to more likely defects
What is Phototropism?
A mechanism by which plants respond to light
What are plants sensitive to and what is this called?
- Light and gravity
- Positive Phototropism and Positive Geotropism
What hormone influences plant growth?
Auxin
Fill in the gaps:
The roots grow on the side with the ________ auxin
The shoots grow on the side with the ________ auxin
- Least
- Most
Where do shoots grow?
Towards the light, against the force of gravity
What are auxin used for in agriculture?
As weed killers, rooting powders and growth in tissue culture
What is ethene used for in agriculture?
To slow down fruit ripening
What are gibberellings used for in agriculture?
Used to increase fruit size, end seed dormancy and promote flowering
What is the optimum human body temperature?
37°C
What controls your core body temperature?
The thermoregulatory system in the hypothalamus
How do humans keep their temperature low?
- By dilating blood vessels that supply your surface skin-vasodilation enabled transfers of energy via radiation
- By sweating from sweat glands which cools as water evaporates from your skin
- By having hairs lie flat to not trap any heat
How to humans keep a high internal temperature?
- By constricting blood vessels near the surface of the skin-vasoconstriction
- By stopping sweat production
- By having skeletal muscles contract and relax rapidly causing shivering
- By having hair stand up (caused by goosebumps-trapping a layer of insulating air)
What are the 2 main poisonous waste products?
Carbon dioxide and urea
What is carbon dioxide produced by?
Body cells during respiration-removed by breathing out
What is urea produced by?
The nitrogenous waste produced by the breakdown of excess amino acids in your liver-removed by the kidneys
What is the process in which the liver removes the amino groups from amino acids?
Deameniation-this forms ammonia
How does dialysis work?
Blood leaves the arm, is passed around a machine in which removes urea and other mineral ions via dialysis fluid across a semi permeable membrane-there is no net movement of other particles due to the fluid being the same concentration as the blood.
How is the rejection problem catered for in kidney transplants?
By using similar tissue types (between the doner and recipient) as well as by taking immonosuppressant drugs.
