Biology Topic 5

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What is homeostasis?
Homeostasis is the regulation of internal conditions in the body.
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Why does body temperature need to be kept constant?
Normal bodily temperatute (37 degrees) needs to be kept constant for optimum enzyme action and other cell functions.
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Which two body systems are responsible for homeostasis?
The nervous and endocrine systems
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What are the steps of control systems?
RECEPTOR-detects change in the environment, COORDINATION CENTRE-one coordination centre recieves and processes information, EFFECTOR-a muscle or a gland brings about a response
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How are changes detected by the body?
A receptor detects chnages in the environment
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What is the function of the nervous system?
It enables us to detect our surroundings and coordinate our behaviour
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What are the two parts of the nervous system?
The central nervous system (brain and spinal cord) and the peripheral nervous system (nerves leading to and from the brain and spinal cord)
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What is the scientific name for a nerve cell?
A neurone
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What are the steps in the pathway of a nerve impule beginning with the stimulus and ending with the response?
Stimulus, receptor, coordinator, effector, response
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What is a reflex action?
A rapid, automatic response to a stimulus
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Why are reflex actions important?
They are important because they prevent us from getting hurt
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Name the nervous pathway that a nerve impulse takes during a reflex action
The reflex arc
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What is the gap between neurones called?
A synapse
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How does a nerve impulse travel from one nerve to the next?
They diffuse across the synapse with the help of chemical transmitter molecules
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Which region forms the largest part of the brain?
The cerebral cortex
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What does the cerebral cortex do?
It is concerned with: consciousness, intelligence, memory and language
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What does the cerebellum do?
It is concerned with coordination of muscular activity
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What does the medulla do?
It controls unconscious activities e.g heartbeat and breathing
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Why are MRI scanners used?
They are used to produce very detailed images of parts of the human body. They are also very safe and don't use ionising radiation.
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Which part of the eye has receptor cells that are sensitive to light?
The retina
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Give one function of the iris
Controls the size of the pupil
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Give one function of the ciliary muscles and suspensory ligaments
They change the shape of the lens to focus light rays on the retina
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There are some receptor cells in the retina that percieves colour. What are they called?
Cones
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How is the iris adapted to low-intensity light vision?
When there is a low light intensity, radial muscles contract and the pupil becomes larger.
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Explain why rods enable us to see in low-intensity light.
Rods are around 1000 times more sensitive to light than cones and therefore they allows us to see in low-intensity light.
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What is refraction?
The bending of light rays as they travel from one medium to another
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What parts of the eye help to refract light?
The cornea and lens
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How does the shape of the lens change when focusing light rays from a near object?
Then lens becomes thicker
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What is the name of the process that changes the shape of the lens?
Accomodation
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List the causes of short-sightedness
They eyeball is too long or the cornea is too sharply curved
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List the causes of long-sightedness
The lens is too weak (not thick enough) or the eyeball is too short or the cornea is not curved enough
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Explain the principle of laser surgery
It is used to change the shape of the cornea
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Where is body temperature monitored and controlled?
In the thermoregulatory centre in the brain
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Give two actions that the body takes when body temperature increases
Blood vessels become wider or dilate (vasodilation) and sweating increases
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What is vasoconstriction?
When blood vessels in the skin become norrower, or constrict
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Give one mechanism that the body uses to increase its temperature
Skeletal muscles contract and the body shivers
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What is the function of the endocrine system?
The endocrine system is made up of many different glands around the body which secrete hormones. These hormones work on effectors and the effects of hormones take minutes or hours to occur.
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Which organ secretes hormones and also digestive enzymes?
The pancreas
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Which endocrine glands are found in the female only?
Ovaries
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Explain why the pituitary gland is known as the master gland.
The oituitary gland is known as the master gland because it regulates the secretion of other hormones from other endocrine glands as well as having a direct effect on some organs.
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Name a hormone that controls blood glucose
Insulin
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What effect does insulin have on our body's cells?
It causes glucose in the blood to move into our body's cells
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Describe how a person's blood glucose concentration changes after a meal.
As you eat food and it is digested, the blood clucose level rises, which causes a surge in insulin.
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What is normal concentration of blood glucose?
Normal concentration of blood glucose is between 4.5-7.5 mmol per dm^3 of blood.
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What is the cause of Type 1 diabetes?
The pancreas not producing enough, or any, insulin.
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What is the cause of Type 2 diabetes?
The main cause is when the body's cells lose their sensitivity to the insulin being produced
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What is the correlation between obesity and Type 2 diabetes?
Obesity increases the risks of Type 2 diabetes
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How can Type 1 diabetics control the condition?
By injecting insulin
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What effect does too little water have on our body's cells?
Too little water means that our cells will not function efficiently
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What effect does too much water have on our body's cells?
Too much water would burst cells
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What is the role of the kidneys?
They are used for maintaining water balance in the body
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What happens when the concentration of water in the blood falls?
When water concentration falls, larger amounts od ADH are released which means that the body will reabsorb more water
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What is negative feedback?
Reversing changes to the body when they have happened
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What is dialysis?
Blood being removed from a patient's arm and being removed of waste by passing through a dialysis machine
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Why would a person recieve dialysis?
If their kidneys were not functioning efficiently (correctly)
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Which kidney donors are most appropriate?
Somebody closely related to you as they are more likely to be of the same blood group
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How is the risk of rejection of a transplant be reduced?
By the patient taking immunosuppressant drugs which tone down the patients immune system
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Give one complication arising from dialysis
It reduces life expectancy due to complications
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Why aren't transplants suitable for everyone?
Because some people may be too weak for the operation or maybe have another condition which stops them from being able to
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What is the main reproductive hormone in males?
Testosterone
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What is the main reproductive hormone in females?
Oestrogen
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What does oestrogen do?
Maintains the lining of the uterus
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What does testosterone do?
It stimulates sperm production
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Which four hormones control the menstrual cycle?
FSH (follicle stimulating hormone), LH (lutenising hormone), oestrogen and progesterone
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Which hormones maintain the lining of the uterus?
Oestrogen and progesterone
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Explain why FSH and LH are given as fertility treatments
This is beacuse FSH causes an egg to mature in the ovaries and LH triggers ovulation (the release of the egg)
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What is in-vitro fertilisation?
When a mothers egg is fertilised outside the body with the fathers sperm
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Which hormone is released when we become frightened?
Adrenaline
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How can contraceptives be divided into broad categories?
Methods that use hormones and barrier methods
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Give two examples of barrier methods of contraception
Condom and Diaphragm
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What is a plant growth movement called?
A tropism
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How do plants respond to light?
Usually they will show positive phototropism which means that the ywill grow towards the light
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How do plant shoots respond to gravity?
If the shoot grows upwards it is negatively gravitropic however if it grows down it is positively gravitropic
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What are auxins?
Plant hormones
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How do auxins cause plants to bend towards light?
Beacause the auxins would move to the side not being shone on by light. On this side the plant will grow more as there are more auxins and therefore it will bend
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Where are stem cells found in plants?
In the meristems (near the top of the shoot)
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How is tissue culture of plant cells used?
To produce clones of plants quickly
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Why can auxins be used as weedkillers?
This is because they disrupt cell motabolism and kill plants
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What are gibberellins?
Plant hormones that speed up seed germination
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What is a use of ethene in plant development?
It regulates cell division and ripens fruits faster
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Other cards in this set

Card 2

Front

Why does body temperature need to be kept constant?

Back

Normal bodily temperatute (37 degrees) needs to be kept constant for optimum enzyme action and other cell functions.

Card 3

Front

Which two body systems are responsible for homeostasis?

Back

Preview of the front of card 3

Card 4

Front

What are the steps of control systems?

Back

Preview of the front of card 4

Card 5

Front

How are changes detected by the body?

Back

Preview of the front of card 5
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