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B1 Edexcel Topic 2

Questions about B1 Biology Edexcel topic 2

QuestionAnswer
Define homeostasis. Maintenance of a stable internal environment.
Define thermoregulation. Maintenance of a stable temperature (37 decrees celcius) inside the body.
Define osmoregulation. Maintenance of suitable water concentrations within the body.
Why is it necessary to maintina a body temperature of 36 degrees celcius inside the body? Enzymes are denatured above this temperature. Chemical reactions happen too slowly below this temperature.
List the mechanisms used by the body to cool us down. Sweating, vasodilation, panting, erector muscles relax so hairs lie flat.
List the mechanisms used by the body to warm us up. Vasoconstriction, erector muscles contratc so hair stands on end.
Which part of the brain is involved in homeostasis? Hypothalamus.
What does the term 'negative feedback' mean? When our body responds to a change with an oposite response (e.g. our body responds to an increase in our body temperature by decreasing our body temperature).
What is the role of the sebaceous glands in thermoregulation? It secretes a waxy substance onto the skin. This distributes the sweat more evenly.
What is the role of vasodilation in homeostasis? Vasodilation is the dilation (opening) of blood vessels near the skin. This allows more heat energy to be lost from the blood to the surroundings by radiation, cooling the body.
What is the role of vasoconstriction in homeostasis? Vasoconstriction is the constriction (narrowing) of blood vessels near the skin. This reduces the amount of heat energy lost from the blood to the surroundings by radiation, and so keeps the body warm.
How does sweating act to cool the body? Heat energy is transferred, by radiation, from the body to the sweat. The sweat evaporates, cooling the body.
Why does out body warm up during exercise? Increased respiration is required to provide energy for our working muscles. Respiration releases heat energy.
What is the role of the erector muscles in homeostasis? Erector muscles contract causing hairs to stand on end. Air is trapped between the hairs. Air is a good insulator so reduces the amount of heat energy lost by radiation to the surrounding.
What are endocrine glands? They release hormones into the blood.
What are hormones? They are chemicals that are released from glands and travel in the blood to their target organs.
Which 2 hormones are involved in blood glucose regulation? Insulin and glucagon.
How does our body reduce blood glucose levels after a meal? Insulin is released by the pancreas. Insulin binds to liver, causing liver to take in glucose. Glucose is turned into glycogen.
How does our body increase blood glucose levels after heavy exercise? Glucagon is released by the pancreas. Glucagon binds to liver, causing the liver to break down glycogen into glucose. This glucose is then released intot the blood stream.
What is type 1 diabetes and how can it be controlled? Type 1 diabetics cannot produce insulin. They must inject insulin or exercise to reduce blood glucose concentrations, and limit the amount of sugary foods that they eat.
What is type 2 diabetes and how can it be controlled? Type 2 diabetics have become resistant to insulin. They must exercise to reduce blood glucose concentrations, and limit the amount of sugary foods that they eat.
Why might we be seeing an increase in the number of cases of type 2 diabetes? Due to increased number of individuals who are overweight, exercising too little, and eating too many sugary foods.
Which plant hormone is invloved in the phototropic and gravitropic responses of plants? Auxin.
How does auxin bring about positive phototropism in shoots? Auxin causes cell elongation. Auxin is produce in shoot tip and broken down by sunlight. Sunny side = no auxin. Shaded side = auxin. Auxin causes cell elongation on shaded side.
How does auxin bring about positive gravitropism in roots? Auxin inhibits cell elongation. Auxin falls downwards due to gravity. Top of root = no auxin. Bottom of root = auxin. Auxin prevents cell elongation on the bottom of the root.
What are 4 commercial uses of plant hormones? • selective weedkillers • rooting powder • seedless fruit • fruit ripening
The central nervous system consists of... Brain and spinal cord.
What are dendrons? The branced terminals that come off the cell bpody of a neuron and receive the signal from the previous neuron.
What are axons? The long, thin part of a neuron.
What is the role of the myelin sheath? To insulate the axon, and to speed up the electrical impulse.
How is a signal passed from one neuron to the next? Chemical neurotransmitters diffuse across the synapse.
Describe the route of a typical stimuli-response pathway. (Stimuli detected by) receptor -> sensory neuron -> brain -> motor neuron -> effector (carries out response).
Describe the route of a reflex arc. (Stimuli detected by) receptor -> sensory neuron -> relay neuron in the spinal cord -> motor neuron -> effector (carries out response).
What is the purpose of a reflex arc? To protect us from injury as it is a more rapid reponse.
How do selective weedkillers work? Auxins or giberellins are used. They cause broad-leaved plants (weeds) to grow uncontrollably and die. Narrower-leaved plants (crops) are left unaffected.
How does rooting powder work? Auxins are applied to the end of a cutting. Roots develop rapidly. No need to wait for plants to grow from seed. Large number of plants produces from the same plant (same genetics).
How can supermarkets use plant hormones to ripen fruit? Ethene (also called ethylene) can be applied to fruits and it causes them to ripen.
How can plant hormones be used to produce seedless fruit? Giberellins used. Cause plants to grow without the need for fertilisation. This means thaht seeds don't develop.
Created by: StHilds2013
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