Topic 2 - Responding To Change Flashcards
What is Homeostasis?
It is maintaining a stable internal environment
What is osmoregulation?
Is the control of the amount of water in the body. An example of homeostasis.
How is body temperature controlled?
By the hypothalamus
Osmoregulation : If there is too much water in your body what happens?
- Sweat is produced by sweat glands
- The kidneys produce more urine
Osmoregulation: If there is not enough water in your body what happens?
- Your brain makes you feel thirsy
- The kidensy produce less urine
What is thermoregulation?
- Is the control of the temperature of the body
- An example of homeostasis
- Hypothalamus in the brain monitors ksin temp. from receptor cells
Why is it important to maintain body temperature?
Enzymes work best at 37 degrees celsius. If the body temperature is dramatically above or below that then enzymes will not work and you die.
What is the hypothalamus?
It is the part of the brain that regulate body temperature
What happens when temperature receptors detect your too cold?
- Shiver muscles generate heat when they make energy
- Erector muscles contract pulling hair up, trapping a layer if air
- Very little sweat produced from glands
- Blood vessels near the surface of the skin constrict (vasoconstriction)
- Less blood less heat
What happens when we receptor cells detect you’re too hot ?
- Erector muscles relax, hairs lie flat
- Lots of sweat cools down
- Blood vessels close to the surface dialate to allow more blood to flow (vasodilation)
- Skin looks redder
What is negative feedback?
When there is a change to the conditions in your body negative feedback changes these back to normal and keeps them steady.
If the environment chnages too much then it might not be possible to counteract it.
What is a hormone?
- Chemical messengers sent in the blood to activate traget cells
- Long lasting effects
- traget cells in target organ
What is a neurone?
- Transmit information as electrical impulses around the body
- Dendrons which connect with other neurones
- electrical impulse passed along the axon
- myelin sheath prtecting the axon
- synapse whcih is the gasp between two neurones.
What are effectors ?
Muscles and glands and known as effective- they respond in different ways Muscles contract in response to a nervous impulse whereas glands secrete substances for example hormones
What are neurones and what do they do?
Neurones transmit information around the body as Electrical impulses
What is myelin sheath?
- Surrounds the axon
- a fatty layer that insulates the neurone from surrounding tissue
- allows impulses to travel faster and not get lost
What is a synapse?
- A gap between two neurones
- make sure the impulses only travel in one direction
- impulses cause neurotransmitters (chemicals) to be released at the axon endings
- neurotransmitters diffuse across the synapse
- they fit into the receptors on the next nuerone
- this triggers an impulse to start in the next synapse
What are the differences between nerves and hormones?
Nerves
- Very fast message
- act for a short time
- act on a precise area
- electrical message
Hormones
- Slower message
- act for a long time
- act in a general way
- chemical message
What is a stimulus and how is it detected?
- A change in your environment that you need to react to
- Sense organs detect stimuli
What are the three types of neurones?
- sensory neurone
- relay neurone
- motor neurone
What is a Motor neurone ?
- Recieve impulses from relay neurones and carry impulses to effectors (muslce/glands)
- causes a response e.g. muscle contracting
- No dendron but has dendrites on the cell body
What is a sensory neurone?
- Long Dendrons
- Short axons carrying nerve impulses from the receptors in the sense organs to the central nervous system
- Receptors detect changes in the environment (stimuli)
What is a relay neurone?
- short neurones which link sensory and motor neurones
- many dendrites to allow nerve impulses to pass from other neurones
What is a reflex arc?
- caused by quick reactions to pull us away from a dangerous stimuli
- They just go to the spinal cord not the brain
- Receptor cells detect stimulus
- They trigger an impulse to travel down a sensory neurone to the spinal cord
- The impulse crosses a synapse to a relay neurone
- The message travels along a motor neurone
- The message reaches the effector e.g. muscle
- This causes a response e.g. muscle contracts
What is the CNS?
- The central nervous system coordinates a response when a stimulus id detected by recpetors in a sense organ
What two hormones control blood sugar level?
- Insulin
- Glycagon
What happens if blood glucose levels are too high?
- Insulin is added
- The insulin comes from the liver where it is secreted
- controlled by negative feedback
What happens if blood glucose levels are too low
- Glucagon is added by the pancreas, it is secreted
- The glucagon is removed by the liver and replaced by glucose, glucagon makes the liver turns glycogen into glucose
- controlled by negative feedback
What is type one diabetes?
- The pancreas produces little or no insulin whic then can’t reduce blood sugar levels and could rise and kill them
What is type two diabetes?
- The pancreas doesn’t produce enough insulin or when a person becomes resistant to insulin
- blood sugar levels rise
How can you control type one diabetes?
- Avoiding foods high in simple carbohydrates for example sugars
- Injecting insulin into the blood at mealtimes this will help the liver remove the glucose as soon as it enters the blood when food is digested
- The amount of insulin that needs to be injected depends on the persons diet and how active they are e.g. Eating a healthy diet and doing regular excercise reduces the amount
How can you control type 2 diabetes?
- Eating a healthy diet
- Getting a regular exercise plan and Lose weight
- Medical or insulin injections
What is a BMI and how is it calculated?
- Body mass index
- BMI equals body mass divided by height squared = KG/M2
- Obese equals over 30
Plants respond to stimuli in 2 ways, what are they?
- Phototropism
- Gravitropism (Geotropism)
What is a tropism?
Growth of the plant in response to a stimulus
What is geotropism?
- A response to gravity
- Roots are positively gravitropic - they grow downwards
What is phototropism?
- The growth of a plant in response to light
- Shoots are positively phototropic - they grow towards the light
What are the two hormones that allow plants to grow in response to a stimuli?
- Gibberellin
- Auxin
What does auxin do?
- Stimulates plant tips to grow
- produced in the tips and diffuses backwards to stimulate the cells to elongate
What does Gibberellin do?
- Stimulates plant stems to grow
- seed germination
- stem growth
- flowering
What happens if plant shoots are positively phototropic?
- The shoot tip is exposed to ligh so more auxing accumulates on the shaded side
- This makes the cells grow faster on the shaded side, so the shoto bends towards the light
- Plants can then absorb mor eligfht for phototsynthesis which then provides sugar whcihc then provides energy for growth
What happens if roots are positively gravitropic (Geotropic)
- A root growing sideways menas that ravity causes an unequal distribution of auxin in the tip
- more auxin in the lower side
- cells on the top elongate faster and the root bends downwards
- this means plants can extend there roots far into the soil to absorb more water and minerals
What are the 4 commercial uses of plant hormones?
- Selective weed killers
- Growing from cuttings with root powder
- Controlling the ripening of fruit
- Producing seedless fruit
What hormone is used to increase size of fruit
Gibberellins
How are selective weedkillers used from plant hormones?
- Affect broad leave plants e.g. weeds growing in crops or in a lawn
- They disrupt their normal growth patterns to kill them leaving the grass and crops untouched
How are cuttings grown using plant hormones?
- Cutting = part of a plant with some leaves on
- By adding rooting powder to the cutting in soil it will grow
- This enables farmers to grow lots of clones of a really good plant very quickly
How is the ripening of fruits controlled by plant hormones?
- Can happen during transport or at the plant.
- Fruits can be picked still unripe so less easily damaged
- Ripening hormone is added to then make the fruit ready to buy
How are seedless fruits produced using plant hormones?
- Fruit that has been grown on plants which has been pollinated by insects. If the fruit hasnt been pollinated the fruits seeds don’t grow
- Growth hormones are applied to the unpollinated flowers so that the fruit will grow and seeds won’t
