Topic 2- Responses to a changing environment Flashcards
To revise the key terms in B1 Topic 2.
Homeostasis
The maintenance of a stable internal environment in an organism.
Negative feedback system
If something in the body changes beyond a certain limit, then the change is detected and the body automatically responds to balance things up again.
Thermoregulation
The maintaining of a steady body temperature (e.g. for us approx. 37.5 degrees C).
Vasoconstriction (Higher)
Blood vessels at the surface of the skin become narrower to restrict blood flow and heat loss through radiation.
Vasodilation (Higher)
Blood vessels at the surface of the skin become wider to increase blood flow and heat loss through radiation.
Hypothalamus
Region of the brain that is responsible for controlling body temperature.
Erector muscles
Control the hairs on the surface of the skin, these stand up when the erector muscles contract.
Hypothermia
Very low temperatures resulting in great heat loss the body can lead to hypothermia and finally death. If body respiration can’t replace the heat loss, then your body gradually cools, it begins to malfunction and eventually ceases to function at all.
Hyperthermia
Very high temperatures make you feel extremely uncomfortable as your body struggles to cope with the situation and you suffer from ‘heat exhaustion’ and then heatstroke - which can be fatal.
Hormones
Chemical messengers in the blood that coordinate and control many body responses. Slower than nerves and act in a more general area.
Gland
Hormones are secreted by glands e.g. the endocrine gland, and are usually transported to their target organs by the bloodstream which determines their speed of distribution.
Target organ
The specific site at which a hormone acts.
Nerve
Electrical messengers. Much faster than hormones and act on a very precise area.
Shivering
Muscles contracting and relaxing very quickly to generate heat.
Sweating
Sweat released from sweat glands evaporates off the surface of the skin to remove heat and cool the body down.
Glucose
The simple type of sugar that travels in the blood stream.
Glycogen
When excess glucose is removed from the blood it is stored as glycogen in the liver.
Insulin
The hormone that acts to reduce blood glucose levels by converting glucose into glycogen at the liver.
Glucagon
The hormone that acts to increase blood glucose levels by converting glycogen at the liver into glucose.
Pancreas
The organ that produces and releases insulin and glucagon.
Type 1 diabetes
Type 1 diabetes occurs when the pancreas produces much too little of the hormone insulin and in some cases, no insulin at all. This causes the blood glucose level to rise to potentially lethal levels.
Type 2 diabetes
The type 2 diabetes condition is when the pancreas doesn’t make enough insulin or the person has become resistant to insulin so the body doesn’t even respond appropriately to any insulin present, and both will cause the blood sugar level to rise. Linked to obesity.
BMI
Body Mass Index (BMI) = (body mass in kg) / (height in m)2
Phototropism
A plants response to light.
Geotropism (or gravitropism)
A plants response to gravity.
Hydrotropism
A plants response to water.
Positive tropism
The plant grows towards the stimulus.
Negative tropism
The plant grows away from the stimulus.
Neurone
Elongated cells that carry electrical signals or impulses all around the body.
Relay neurone
Connects a sensory neurone to a motor neurone.
Sensory neurone
Receives the stimulus and sends it to the CNS.
Motor neurone
Sends the message from the CNS to the effector to carry out a response.
CNS
Central nervous system- the brain and spinal cord.
PNS
Peripheral nervous system- the nerves that lead from the spinal cord to the rest of the body.
Auxin
A plant hormone that controls the growth of the tips of shoots and roots.
Selective weedkillers (Higher)
Selective plant growth hormone based weed-killers have been developed that affect the growth development of broad-leafed weeds and eventually kill them, BUT, do not affect the grasses and cereals with narrow leaves.
Fruit ripening hormones (Higher)
The ripening can be controlled while the fruit are still on the tree/bush or during transport to the warehouses/shops. You can therefore pick fruit before it is ripe and still quite firm - which means its less easily damaged in transport. You can then choose the time when the ripening hormone is added so the fruit is as fresh as it can be for you the consumer via the wholesaler, market vendor, small shop or giant supermarket!
Seedless fruit hormones (Higher)
By applying growth hormones to the unpollinated flowers of some fruit plants, the fruits grow BUT not the seeds! Sometimes the plant hormones are applied after pollination, but still prevent the seeds developing. A very handy way of producing common varieties of seedless fruits like watermelons, grapes, bananas and many seedless citrus fruits, such as oranges, lemons and limes.
Rooting powder (Higher)
Some plant cuttings won’t always readily grow in soil or compost, but by adding a rooting powder to the compost containing a plant hormone like auxin, the growth of roots and subsequent shoots are greatly encouraged. It then enables a flower grower or market gardener to rapidly produce lots of clones of a particular plant - ideally, of the best quality plants.
Gibberellins (Higher)
Gibberellin is another plant growth hormone used to stimulate seed germination, stem growth (taller) and flowering.
Stimulus
Any change in your surroundings e.g. temperature, visual, sound etc. is potentially a detectable stimulus to one of you sensory organs e.g. skin, eyes, ears etc. The stimulus might be chemical, light, pain, position, pressure, sound, temperature, touch etc.
Reflex arc
The response by-passes the brain, goes through a relay neurone to directly connect the sensory and motor neurone through the following pathway: stimulus ==> receptor cell ==> sensory neurone ==synapse==> relay neurone in central nervous system =synapse==> motor neurone ==> effector ==> response.
Receptor cells
Detect the stimulus. In the receptor cells the stimulus input is converted into an electrical signal - an electrical impulse which is sent to the brain.
Synapse
A connection between two neurones eg the junction between a sensory neurone and a relay neurone, it enables the electrical impulse signal to reach the spinal cord and brain (ie the central nervous system). Between the end of one neurone, and the start of another, chemicals (neurotransmitters) are released in the gap that rapidly diffuse across the gap in the synapse, transferring the electrical signal from one neurone to another.
Neurotransmitter
Chemicals produced that transmit the electrical signal across a synapse gap between one neurone cell and another.
Myelin sheath
A fatty electrically insulating tissue layer around the axon connections between neurones - the axon in the neurone cells carries the electrical signal - if there was no myelin insulation, the signal will be lost.
Effectors
The muscles or glands that respond in a variety of ways to the electrical signal from the brain.
Dendrons
Neurone cells have lots of branched endings called dendrons which connect with lots of other neurones.
Axons
The electrical impulses of the nervous system are carried by thin ‘fibres’ called axons which are surrounded by an insulating myelin sheath.
Liver
The target organ for the hormones insulin and glucagon.
