B1 Topic 2

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What does homeostasis mean?
Maintaining a stable internal environment in the body.
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What does negative feedback do?
Respond to a change in a condition to help bring conditions in the body back to a normal level.
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What is osmoregulation?
The regulation of water content. It controls how much water is lost in urine, sweat and breathing out and how much you intake in respiration, drink and food.
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What is thermoregulation?
The regulation of body temperature. It keeps the body temperature at a steady 37 degrees. It keeps retains heat when you're cold and gets rid of it when you're hot. It's important as enzymes in main organs are most active at this temperature.
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What is blood glusose regulation?
Regulating the amount of glucose in the blood stream and keeping it at a steady level.
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What does the hypothalamus do?
Controls body temperature. Has receptors that are sensitive to blood temperatures in the brain. Also receives impulses from receptors in skin which provide information on skin temperatures. When it senses a change, it causes a response in the dermis.
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What happens when temperature receptors detect you're too hot?
Erector muscles relax so hairs lie flat - Sweat is produced (sweat evaporates and transfers heat from skin to environment) - Vasodilation (blood vessels dilate so more blood flows near skin surface and transfer heat to surroundings)
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What happens when temperature receptors detect you're too cold?
Erector muscles contract so hairs stand on end to trap layer of heat next to skin - Sweat glands stop producing sweat - Vasoconstriction (blood vessels constrict so less blood flows near skin surface and less is transferred to surroundings)
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What do hormones do?
They're chemical messengers sent in the blood which carries them to other parts of the body. They only affect particular cells called target cells which have the right receptors to respond to that hormone and are in target organs.
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Definition of hormone & other facts:
-hormones are chemical messengers which travel in the blood to activate target cells-. They travel at the 'speed of blood' and have long-lasting effects.
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What do neurones do?
They transmit information as electrical impulses around the body. They are long which speeds up the impulse.
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Structure of a neurone:
Dendrons-Nucleus-Myelin Sheath-Axon-Synapse
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What is a dendron & an axon?
A dendron is the branched ending of a neurone, they have these endings to connect with other neurones. The axon is what the electrical impulse is passed along.
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What is the myelin sheath and synapse?
The myelin sheath acts as an electrical insulator which stops the impulse getting lost and also speeds up the impulse. The synapse is the connection between two neurones.
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What are neurotransmitters?
Chemicals that transmit nerve impulses and diffuse across the gap. They then set off a new electrical impulse in the next neurone.
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What are the differences between nerves and hormones?
Nerves- Fast message, act for short time on precise area, electrical message. Hormones- Slower message, act for long time in a general way, chemical message.
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What is the nervous system and what does in contain?
The nervous system lets you react to what is going on around you. It includes the central nervous system (brain and spinal cord), sense organs and nerves - which join the cns to sense organs and effector organs.
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What do sense organs do?
They detect stimuli (change in your environment). They have different receptors which are groups of cells sensitive to a stimulus (e.g. light) and change it into electrical impulses. Stimulus - light, sound, touch, pressure, chemical, temp change.
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What are the five sense organs and what receptors do they contain?
1) Eyes - light receptors 2)Ears - sound & "balance" receptors 3)Nose - smell receptors (sensitive to chemical stimuli) 4)Tongue - taste receptors (sensitive to bitter, salt, sweet, savoury, sour - chemical) 5)Skin - sensitive to touch & temp changes
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How does the CNS coordinate a response?
A stimulus is detected by receptors in a sense organ. That info is sent as electrical impulses along sensory neurones to the cns. This sends the response by sending info to an effector muscle/gland along a motor neurone, the effector then responds.
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What is an effector?
Muscles and glands. Muscles contract in response to a nervous impulse and glands secrete substances e.g. hormones.
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What are motor neurones?
Short dendrons and a long axon which carry nerve impulses from the CNS to effectors.
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What are relay neurones?
Short dendrons and axons which carry nerve impulses from sensory neurones to motor neurones.
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What are sensory neurones?
Long dendrons and short axons that carry nerve impulses from receptors in the sense organs to the CNS.
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Order of a coordinated response:
Stimulus - Receptor - Sensory Neurone -CNS - Motor Neurone - Effector - Response
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Practical to investigate external stimuli:
One person is blindfolded whilst another uses a hairpin with the points fixed apart & puts it on their skin. If the blindfolded person feels one point the distance is increased until they feel both & is recorded. Repeat on different parts of the body
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How do reflexes help prevent injury?
Reflexes are automatic responses to stimuli that can reduce chances of being injured. E.g. if someone shines a bright light in your eyes, your pupils automatically get smaller so less light gets into the eye which stops it getting damaged.
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What happens in a reflex arc?
1)Stimulus detected e.g. bee sting 2)Stimulation of pain receptor 3)Message travels along sensory neurone to CNS 4)Reaches CNS and passes along relay neurone 5)Then travels along motor neurone 6) Reaches muscle & contracts to move away
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Order of a reflex arc:
Stimulus (bee sting) - Receptor - Sensory Neurone - Relay Neurone in CNS - Motor Neurone - Effector - Response
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How is blood glucose regulated?
Eating food containing carbohydrates puts glucose into the blood from the gut. Metabolism of cells removes glucose from the blood. Exercise removes even more. To control the level of blood glucose there must be a way to add/remove it.
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What happens if blood glucose level is too high?
Insulin is released from the pancreas and the glucose is removed by the liver. The insulin then makes the liver turn the glucose into glycogen and insulin stops being secreted.
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What happens if blood glucose level is too low?
Glucagon is secreted from the pancreas and makes the liver turn glycogen into glucose so glucagon stops being secreted.
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What is Type 1 Diabetes?
Condition where the pancreas produces little or no insulin and results in the sugar level rising to a level that can kill.
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How to control Type 1 Diabetes:
Limit intake of food rich in carbohydrates - Inject insulin during mealtimes so liver removes glucose quickly as food is digested, usually injected into subcutaneous tissue, amount injected based on persons diet and activeness - better health = less
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What is Type 2 Diabetes?
Condition where the pancreas doesn't produce enough insulin or person is resistant to it so blood sugar level rises. Obese people have increased risk of getting it (obese people have a BMI of over 30)
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Formula for BMI:
BMI = body mass ÷ (height)² (mass in kg height in m)
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How is Type 2 Diabetes controlled?
Eating a healthy diet, getting regular exercise, losing weight. Some take medication or insulin injections.
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How do plants respond to stimuli?
They respond by growing which is called tropism. A positive tropism is growing towards a stimulus.
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What is phototropism & gravitropism?
Phototropism - growth of plant in response to light. Shoots are positively phototropic & grow towards light. Gravitropism (geotropism) - growth of plant in response to gravity. Roots are positively gravitropic so grow downwards.
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What does auxin do?
Auxin is a plant hormone that controls growth at tips of shoots and roots. It's produced in tips and diffuses backwards to make cells behind tips elongate. If the tip is removed the shoot will stop growing.
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Shoots are positively phototrophic:
A shoot tip exposed to light accumulates more auxin than the part in the shade. This makes cells grow faster on the shaded side and the shoot bends towards the light. This lets plants absorb more light for photosynthesis which makes energy for growth
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Roots are positively gravitropic:
A root grows sideways so gravity is making more auxin on the lower side of the tip. In a root the extra auxin stunts growth so cells on top grow faster and the root bends down. It lets plants extend roots deep into the soil so they absorb more water.
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What does gibberellin do?
It is another plant hormone which stimulates seed germination, stem growth and flowering. Stem elongation makes stems of plants grow which helps plants be tall. It often treats dwarf plants. It works with auxin to have a big effect on growth.
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What practical investigates plant growth responses?
Put 10 cress seeds in each of three petri dishes lined with moist filter paper. Shine a light from above on one dish and different angles on the other two. Leave them for one week and observe their responses - they will grow towards the light.
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What variables need to be controlled during the practical?
Number of seeds - same amount in each dish. Seed type - all from the same packet. Temperature - thermometer makes all dishes same temp. Water - measuring cylinder to ensure same water in each dish. Light intensity - same distance between bulb & dish
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How are plant hormones used as selective weedkillers?
Plant hormones are developed to only affect broad-leaved plants (weeds) amongst a field of crops. When the weedkiller affects them their growth pattern is totally disrupted which soon kills them, leaving the crops and grass untouched.
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How does rooting powder help growing from cuttings?
A cutting is a part of a plant that has been cut off, normally if you plant them in the soil they won't grow but if you add rooting powder (containing a plant hormone) they will produce roots and grow as new plants. This lets growers produce clones.
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How do plant hormones ripen fruit?
Fruit ripening can be controlled both while they're still on the plant & in transport. This lets the fruit be picked whilst it's unripe (firmer and less easily damaged). Ripening hormone is then added so it's perfectly ripe when it reaches the store.
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How can plant hormones produce seedless fruit?
Fruit grows on plants that have been pollinated by insects. If the plant isn't pollinated, fruit won't grow. If growth hormones are put on unpollinated flowers on some plants, fruit will grow but the seeds won't e.g. seedless citrus fruits & grapes.
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Other cards in this set

Card 2

Front

What does negative feedback do?

Back

Respond to a change in a condition to help bring conditions in the body back to a normal level.

Card 3

Front

What is osmoregulation?

Back

Preview of the front of card 3

Card 4

Front

What is thermoregulation?

Back

Preview of the front of card 4

Card 5

Front

What is blood glusose regulation?

Back

Preview of the front of card 5
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