Biology (GCSE)- Autumn Term (Yr.11)

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define homeostasis
the maintenance of a stable internal environment response to changes in internal and external conditions
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define stimulus
a change in your environment that you might need to respond to
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what are the stimuli your body might have to respond to ?
touch, pain, temperature, light, chemicals, pressure, sound, possition
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why do animals need self regulating mechanisms ?
to maintain their internal environment, this is achieved by negative feedback
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how does negative feedback work ?
by initaiting correct mechanisms whenever the internal environment deviates from its normal level
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what does the body do when its too hot ?
thermoreceptors in skin detect the increase in temp and send signals to the hypthalamus, hypothalamus recieves signal and then sends signals back to the skin, sweat glands warm sweat and takes heat away when evaporates off skin
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what is vasodialation ?
when your body gets too hot and the shunt vessels contract and the blood vessels closer to the skin dialate to heat the sweat on the skin and help to cool the body down quicker
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what is vasoconstriction ?
when the shunt vessels dialtate and the blood vessels closer to the skin contract to keep the heat in the body more
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what does the body do when its too cold ?
the thermoreceptors sense drop in temp and send message to brain, hypthalamus sends signal back to the skin to the hair erector muscles to contract which causes hair to stand up and trap a layer of air around the skin to insulate the body and vasocon
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what is thermoregulation ?
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different
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define reflex
rapid automatic response of the nervous system that doesnt need thought
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how does the nervous system react to a stimulus ?
a receptor notices the change and sends an impulse by the sensory neurone to the CNS then the CNS sends a signal back to the effector using the motor neurone
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what is the effector ?
either a muscle or gland
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what is a relay neurone ?
the neurone in the brain that connects the sensory neurone and the motor neurone
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what are voluntary reactions ?
they involve thought and pass through the brain, they happen slowly and this is the loop that we use to do most things in the body
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what are reflex reactions used for ?
they are used for self protection and do not pass the brain and involves the relay neurone and happens quickly
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what are the similarites between voluntary and reflex loops ?
they both use receptors and effectors and they use sensory and motor neurones. they also involve impulses
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define reflex
a biological control system that links a stimulus to a response
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what is a neurone ?
a specialised cell that conducts electrical impulses between the body and brain
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define synapse
a gap between two neurones and signals cross this gap using chemicals
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what are neurotransmitters ?
chemicals which allow the signal to cross from the sensory or motor neurone to the relay neurone
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what is a synaptic vessel ?
something which releases neurotransmitters
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what is the synaptic cleft ?
that gap between the motor or sensory neurone and the relay neurone
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what receives the signal in the motor or relay neurone ?
a receptor on the recieving neurone
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define reaction time
the time it takes to respond to a stimulus
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what are the three parts of the brain ?
cerebal cortex, medulla, cerebellum
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what does the cerebellum do ?
responsible for muscle contraction
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what does the cerebal cortex do ?
for things such as consciousness, intellengence, memory and language
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what does the medulla do ?
controls unconscious activities, things you dont have to think about, breathing, heart beat
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what are the two ways you can study the brain ?
study patients with brain damage, look at what part of the brain is damaged and see how to patient is affected, by electrically stimulating the brain by using electrodes and impulses to stimulate different parts of the brain.
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how does an mri scan work ?
by detecting where the most iron is in the brain (ie blood), its tube like machine that produces a detailed picture of the brain
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what are the benefits of studying the brain ?
leads to the development of treatments for disorders of the nervous system
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what are the risks of studying of studying the brain ?
physical damage to the brain, increased problems with brain function
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what does the retina in your eye do ?
its the receptor as its made up of light sensitive cells which are rod and cone cells
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what does the sclera in your eye do ?
its the tough outer layer of the eye and protects/ holds the eye in place
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what does the cornea in your eye do ?
transparent region of the sclera at the front of the eye, refracts light as it enters
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what do the suspensory ligaments and ciliary muscle in your eye do ?
change the shape of your lens to focus light rays on the retina
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what does the lens in your eye do ?
focuses light rays onto the retina
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what does the iris in your eye do ?
it contracts or relaxes to control how big the pupil is and therefore how much light is allowed in
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what does the pupil in your eye do ?
the hole in the centre of your eye to allow light to enter
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what happens to your eye in dim light ?
the cirular muscles relax and radical muscles contract so that the pupil becomes larger to allow most light in
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what happens to your eye in bright light ?
cicular muscles contract and radial muscles relax to make the pupil small to allow only small light in
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define accommodation
changing the shape of the lens to focus light onto the retina
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what muscles contract when the object is near for the lens ?
near= ciliary muscle contracts and suspensory ligament relaxes so the lens becomes thicker+ light rays diverge
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what muscles contract when the object is distant for the lens ?
ciliary muscle relaxes and suspensory ligament contracts so the lens becomes flatter
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where is the image formed for mytopia (short sighted) and hyperopia (long sighted) ?
before the retina............. after the retina
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why do some people have mytopia ?
because the eyeball is too long for the strength of the lens, cornea is too sharply curved so you need a concave lens
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why do some people have hyperopia ?
lens is too weak/ not thick enough, eyeball is too short, cornea not curved enough so you need a convex lens
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define hormone
chemical messengers which travel in the blood to activate target cells
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wheres the pituitary gland ?
the master gland in the brain, produces many hormones
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what does the pancreas do in the endocrine system ?
produces insullin, regulates blood glucose levels
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what does the thyroid do in the endocrine system ?
regulates rate of metabolism, heart rate and temperature, in the throat
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what does the adrenal gland do in the endocrine system ?
produces adernaline, used for flight or fight response, by the kidney
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what does the ovaries do in the endocrine system ?
produces oestrogen in menstrual cycle
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what does the testes do in the endocrine system ?
produces testosterone, controls pubity and sperm
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how does the body react to a rise in glucose ?
a meal is eaten, detected by pancreas, insulin secreted into blood, that causes body cells to use up more glucose, liver+ muscles cells convert glucose into glycogen, blood glucose levels fall
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what is glycogen ?
a storage molecule from glucose
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how does the body react to a decrease in glucose ?
detected by pancreas, pancreas produces glucagon and secretes into blood, glycogen which is stored converted back into glucose to be entered into the blood, glucose levels rise
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what does it mean if you have type 1 diabetes ?
the pancreas produces little or no insulin
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what does it mean if you have type 2 diabetes ?
person becomes resistant to their own insulin
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Other cards in this set

Card 2

Front

define stimulus

Back

a change in your environment that you might need to respond to

Card 3

Front

what are the stimuli your body might have to respond to ?

Back

Preview of the front of card 3

Card 4

Front

why do animals need self regulating mechanisms ?

Back

Preview of the front of card 4

Card 5

Front

how does negative feedback work ?

Back

Preview of the front of card 5
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