Topic 2- Responses to a Changing Environment Flashcards
what is homeostasis?
the maintenance of a constant internal environment
what are the three important examples of homeostasis?
- thermoregulation
- osmoregulation
- blood glucose regulation
what is osmoregulation?
keeping the correct levels of water in the body; when we have not consumed enough water, we urinate less and our urine is more concentrated (and vice versa)
what is thermoregulation?
keeping the body at a constant temperature; this is monitored by the hypothalamus in the brain, which has receptors that are sensitive to the temperature of the blood flowing through it
at what temperature do enzymes function best?
37˚C
when the core temperature is too high, what reactions does the body have?
- blood vessels in skin dilate, causing heat to be lost
- sweat glands release sweat which evaporates, removing heat from skin
- erector muscles cause hairs to lie flat and not trap heat
- in hot/dry conditions, sebaceous glands produce oily sebum that encourages sweat to spread more effectively
when the core temperature is too low, what reactions does the body have?
- blood vessels in skin constrict, reducing heat loss
- muscles start to ‘shiver’ causing heat energy to be released via respiration in cells
- erector muscles cause hairs to stand up, trapping heat
- in cool/wet conditions, sebaceous glands produce oily sebum that waterproofs the skin
what is vasodilation?
if the body is too hot, there is more blood flowing near the surface of the skin through superficial capillaries. blood vessels dilate, allowing more heat to be lost, which cools the body down.
what is vasoconstriction?
if the body is too cold, there is less blood flow through the superficial capillaries because the blood vessels constrict. this helps retain heat.
what are vasoconstriction and vasodilation examples of?
negative feedback
what does the nervous system consist of?
- the brain
- the spinal cord
- paired nerves
- receptors
what does the central nervous system (CNS) consist of?
- the brain
- the spinal cord
what are the rest of the nerves in the body collectively called?
the peripheral nervous system
what are the five senses?
- sight (eyes)
- hearing (ears)
- taste (taste buds on the tongue)
- smell (chemical receptors in the nose)
- touch (receptors in the skin)
(also balance -ears- may also be referred to as a sense)
what does the brain do?
coordinates most of the body’s actions
what is the function of the frontal lobe?
controls higher mental functions, e.g. choice and memory
what is the function of the medulla?
controls automatic actions, such as heartbeat and breathing
what is the function of the cerebellum?
coordinates movement and balance
what is the function of the cerebral hemisphere?
responsible for numerical computation, language and emotions
what is a neurone?
a neurone is a specially adapted cell that carries electrical impulses
what are the elongated parts of a neurone that carry impulses away from the body called?
axons
what are the elongated parts of a neurone that carry impulses towards the body called?
dendrons
what is the insulating layer covering the elongated part of the cell called?
the myelin sheath
what are the three types of neurone called?
- sensory neurone
- relay neurone
- motor neurone
what does the sensory neurone do?
takes nerve impulses from stimulated receptors in sense organs to the CNS
what does the relay neurone do?
in the CNS, these pass impulses on from the sensory neurone to motor neurone
what does the motor neurone do?
takes impulses from the CNS to the muscles or glands
what is a synapse?
a synapse is a small gap between neurones
what happens at a synapse?
- when an electrical impulse reaches a synapse, a chemical transmitter is released that activates receptors on the next neurone
- this causes an electrical impulse to be generated in this neurone
- the chemical transmitter is then destroyed or removed
what is a voluntary response/action?
actions over which we have complete control/ we consciously decide to act.
e.g. walking, speaking, picking something up
what is an involuntary response/action?
actions over which we have no control/ they happen automatically.
e.g. blinking or moving part of your body away from pain
what are hormones?
hormones are chemical messages, produced by endocrine glands, that coordinate and control the ways in which parts of the body function
where are hormones transported?
to their target organs/ target cells
through what are the hormones transported?
the bloodstream
which hormone do the adrenal glands produce, and where is it situated?
the adrenal glands are above the kidneys, and produce adrenaline
which hormones does the pituitary gland produce, and where is it situated?
the pituitary gland is in the brain, and it produces a growth hormone- FSH (follicle stimulating hormone), and LH (luteinising hormone)
in males, what hormone do the testes produce?
testosterone
in females, what hormones do the ovaries produce?
oestrogen and progesterone
if the blood glucose concentration is too high…
- the pancreas releases insulin
- glucose from the blood is then converted into insoluble glycogen in the liver
- and is removed from the blood
- returning levels to normal
if blood glucose concentration is too low…
- the pancreas releases glucagon
- insoluble glycogen in the liver is converted into glucose
- and is released into the blood
- returning levels to normal
what is type 1 diabetes?
when the pancreas is unable to produce insulin at all
what is type 2 diabetes?
when the person has become resistant to the insulin being produced
what are the main symptoms of diabetes?
- urinating more often than normal
- becoming more thirsty
- increased tiredness
- weight loss
- blurred vision
how can diabetics lead a healthy lifestyle?
- eating three meals a day
- including some carbohydrates but reducing fat and sugar in meals
- being physically active
what must type 1 diabetics do in order to control their blood sugar concentration?
inject insulin into the layer of subcutaneous fat
what do scientists think may lead to type 2 diabetes?
obesity
when shoots grow towards the light, they are…
positively phototrophic
when roots grow downwards, in the direction of gravity, they are…
positively geotrophic
what are two types of plant hormone?
auxins and gibberellins
what do auxins do?
promote cell elongation
what do gibberellins do?
- promote cell elongation
- encourage flowering
- breaking seed dormancy
- help seedless fruit to develop
what gravitational effect do auxins have on the shoots of plants?
they increase growth in the lower region of the shoots, which makes the shoot bend upwards
what gravitational effect do auxins have on the roots of plants?
they slow down the growth in the lower regions, which makes the root bend downwards
what effect does light have on the auxins in plant shoots?
the light causes the auxins to accumulate on the shaded part of the stem, which causes growth on that side and means that the plant grows towards the light.
what are the commercial uses of plant hormones?
- selective weedkiller
- rooting powder
- producing seedless fruit (gibberellins)
- fruit ripening (ethene)
