Topic 2 - Responding To Change Flashcards
Osmoregulation is
Regulating water content.
Thermoregulation is
Regulating body temperature
What is another example of homeostasis?
Blood glucose regulation
Body temperature is controlled by
The hypothalamus
The enzymes in the human body work best at
37 C
The hypothalamus contains
Receptors that are sensitive to blood temperature in the brain
The hypothalamus is found
In the brain
The hypothalamus relieves
Impulses from receptors in the skin providing information about the skin temperatures
What happens when your body temperature is too high
- Erector muscles relax so the hairs lie flat
- Sweat is produced as when it evaporates it transfers heat from your skin to the environment
- Blood vessels close to the surface of the skin dilate.!This allows more blood to flow near the surface and transfer more heat to the surroundings
What is vasodilation?
When blood vessels near the skins surface dilate to allow more blood to flow near the surface and transfer more heat into the surroundings.
What happens when your body temperature is too cold
- The erector muscles contract to make hairs stand on end so they can trap an insulating layer of hair
- Very little sweat is produced
- Blood vessels near the surface of the skin constrict so less blood flows near the surface and less heat is transferred to the surroundings
What is vasoconstriction?
When blood vessels near the surface constrict so that less blood can flow near the surface and less heat is transferred to the surroundings
Hormone are
Chemical messengers that travel in the blood to activate target cells
Hormones are produced in
Endocrine glands
Hormones are released
Directly into the blood
Hormones travel
All over the body but they only affect particular cells
Cells that have been affected by hormones are
Target cells that have the right receptors to respond to that hormone
How fast do hormones travel
At the speed of blood
Hormones have _________ effects
Long lasting
Neurones :
Transmit information around the body as electrical impulses
Describe the structure of a neurone
- branched endings called dendrins so they can connect with lots of other neurones
- Axon - where the electrical impulse is passed along
- Myelin sheath along the axon that acts as an electrical insulator to stop impulse getting lost and speeds it up
- Long to speed up impulse as connecting with another neurone slows impulse down so one long neurone is quicker that lots of short ones joined together
The connection between two neurones is called
A synapse
Describe a synapse
- the nerve impulse is transmitted by chemicals called neurotransmitters which diffuse across the gap
- the neurotransmitters then set off a new electrical impulse in the next neurone
Describe the differences between hormones and nerves
Nerves - fast message, act for very short time, act on precise area, electrical message
Hormones A slower message, act for a long time, act in a more general way, chemical message
A stimulus is
A change in your environment that you may need to react to
Sense organs contain different
Receptors
Receptors are
Groups of cells that are sensitive to stimulus energy - they change stimulus energy into electrical impulses
Describe the central nervous systems response to a stimulus
- Stimulus is detected by receptors in a sense organ and the information is sent as electrical impulses along sensory neurones to the central nervous system
- The central nervous system consists of the brains and the spinal cord
- The CNS coordinates the response
- The CNS sends information to an effector along a motor neurone
- The effector responds
What are the effectors?
Muscles and glands
Reflexes are
Automatic responses to certain stimuli that reduce the chances of being injured
Describe a reflex arc
- The neurones in reflex arcs go through the spinal cord or through an unconscious part of the brain
- When a stimulus is detected by receptors impulses are sent along the sensory neurone to the CNS
- In the CNS the sensory neurone passes on the message to a relay neurone
- Relay neurones relay the impulses to a motor neurone
- The impulses then travel along the motor neurone to the effector
- The effector then reacts. This is quicker than normal responses as you don’t have to think about the response.
Blood glucose level too high=
Insulin is added
Homeostasis is
Maintaining a stable internal environment
Blood glucose level too low =
Glucagon is added
Insulin is secreted by
The pancreas
Glucose is removed by
The liver
Insulin makes the liver :
Turn glucose into glycogen
Glucagon is secreted by
The pancreas
Glucose is added by
The liver
Glucagon makes liver turn glycogen into
Glucose
Type 1 diabetes is a condition where
The pancreas produces little or no insulin
Type 1 diabetes is controlled by:
Limiting intake of foods rich in simple carbohydrates
Insulin Therapy - injecting insulin into the blood through subcutaneous tissue
Type 2 diabetes is a condition where
The pancreas doesn’t produce enough insulin or when a person becomes resistant to insulin
Obese people have an increased risk of developing:
Type 2 diabetes
Type 2 diabetes can be controlled by
Having a healthy diet
Some may also have insulin injections
Plants can respond to stimuli by
Regulating thier growth
A plants growth response is called
A tropism
A positive tropism is
Growing towards a stimulus
What is a phototropism ?
The growth of a plant in response to light.
Shoots are __________ photographic
Positively (they grow towards the light)
What is a gravitropism?
The growth of a plant in response to gravity
Roots are ____________ gravitropic
Positively (they grow downwards)
Auxin is:
A plant hormone that controls the growth at the tips of shoots and roots
Auxin is produced in
The tips and diffuses backward to stimulate the cells just behind the tips to elongate
If the tip of a shoot is removed :
No auxin will be available and the shoot stops growing
Auxin _________ growth in the shoot
Promotes
High concentrations of auxin in the root
Inhibit growth
Describe how shoots are phototrophic
- When a shoot tip is exposed to light more auxin accumulates in the side that’s in the shade
- This makes cells grow faster on the shaded side so the shoot bends towards the light
- This enables the plant to absorb more light for photosynthesis
Describe how roots are positively gravitropic
- When a root is growing sideways gravity produces an unequal distribution of auxin in the tip with more auxin on the lower side
- The extra auxin inhibits growth which means the cells on top elongate faster and the roots bend downwards
- This allows plants to extend their roots deep into the soil so they’re well anchored and can absorb more water and minerals which are needed for photosynthesis
Gibberellin stimulates
Seed germination, stem growth and flowering
Gibberellin stimulus the stems of plants to
Grow by stem elongation
What are examples of commercial uses if plant hormones?
Selective weed killers, rooting powders, control over ripening of fruit, seedless fruit production
How do selective weedkillers work?
Selective weedkillers makes broad leaved plants grow uncontrollably and die whilst leaving the thinner leaves plants untouched.
How are rooting powders used?
Cuttings are dipped in rooting powders which contain plant growth horn eon which makes them produce roots rapidly. This enables growers to produce lots of plant clones very quickly
How are plant hormones used to control the ripening of fruit?
Fruits are picked while still un ripe and whilst being transported to the supermarkets , a ripening hormone is added which means the fruit will ripens and be in perfect condition when it reaches the shelves.
How are plant hormones used to produce seedless fruit ?
Fruit with seeds usually only grow on plants that have been pollinated by insects. If growth hormones are applied to un pollinated flowed the fruit will grow but the seeds won’t.
