coordination and response Flashcards
how do animals increase their chance in survival
by responding to changes in their external enviroment, eg by avoiding places that are too hot or too cold
what do animals also respond to
their internal enviroment to make sure that the conditions are always right for their matabolism
how do plants also increase the changes of surviving
by responding to any changes in their enviroment
what is a stimulus
any change in the internal or external enviroment
what do receptors do
detect stimuli and effectors produce a response
how do receptors detect stimuli
receptors in the sense organs ( the eyes, ears, nose, tongue, and skin) are groups of cells that detect external stimuli (eg rod and cone cells in the eyes that detect changes in light)
what are effector cells
they are cells that bring about a response to the stimuli. they include muscle cells and cells found in glands (eg the pancreas) Effectors respond in different ways - muscle cells contract, whereas glands secrete hormones
how do receptors communicate with effectors
via the nervous system, the hormonal system, or sometimes both
what does the CNS do
co-ordinates information
what is the nervous system madw up of
made up of all the neurones (nerve cells) in your body.
what are the 3 main types of neurone
- sensory neurone
- relay neurone
- motor neurone
what does the CNS only consist of
brain and spinal cord
what happens when receptors in s sense organ detect a stimulus
- they send electrical impulses along sensory neurones to the CNS.
- the CNS then sends electrical impulses to an effector along a motor neurone. The effector then responds accordingly
what is the job of the CNS
to co ordinate the response. Co- ordinated responses always need a stimulus, a receptor, and an effector
state –> because neurones transmit information using high speed electrical impulses, the nervous system is able to bring up very rapid responses.
what is a synapse
the connection between two neurones is called a synapse
what is the nerve signal transferred by
- by chemicals called neurotransmitters which diffuse across the gap
- these chemicals then set off a new electrical signal in the next neurone
state –> reflexes help prevent injury
where does the reflex arc go through
the central nervous system
what is a reflex arc
the route taken by the information in a reflex (from receptor to effector)
what is reflexes
reflexes are automatic responses to certain stimuli - they can reduce the chances of being injured.
what do the neurones in the reflex arc go through
go through the spinal cord or through an unconscious part of the brain
what happens when a stimulus is detected by receptors
- an impulse is sent along a sensory neurone to the CNS
- in the CNS the sensory neurone passes on the message to another type of neurone - a relay neurone
- relay neurones relay the impulse to a motor neurone
- the impulse then travels along the motor neurone to the effector
- the muscle then contracts and moves your hand away from the hot object
- because you dont have to think about this response , it is quicker than normal responses
block diagram to represent a reflex arc
stimulus –> receptor –> sensory neurone –> CNS –> motor neurone –> effector –> response
what does the conjunctiva do
lubricates and protects the surface of the eye
what does the sclera do
it is the tough outer layer that protects the eye
what does the iris do
controls the diameter of the pupil (the hole in the middle) and therefore how much light enters the eye
what does the cornea do
refracts light into the eye. the cornea is transparent and has no blood vessels to supply it with oxygen, so oxygen diffuses in from the outer surface
what are the differences between cone and rod cells
- rod cells are more sensitive in dim light but cant sense colour.
- cones are sensitive to colours but arent so good in dim light. cones are found all over the retina. but there are loads of them at the fovea
state–> the optic nerve carries impulses from the receptors to the brain
state –> very bright light can damage the retina - so you have a reflex to protect it
state –> very bright light triggers a reflex that makes pupil smaller, allowing less light in
what happens to the pupils when there is bright light
light receptors detect the bright light and send a message along a sensory neurone to the brain. the message then travels along a relay neurone to a motor neurone which tells circular muscles in the iris to contract, making the pupil smaller
state –> the opposite process happens in dim light. the brain tells the radial muscles to contract, making the pupil bigger
bright light
pupil becomes smaller, circular muscles contract
dim light
radial muscles contract, pupil becomes bigger
to look at distant objects
- the ciliary muscles relaxes which allows the suspensory ligements to pull tight
- this makes the lens go thin
- so it refracts light by a smaller amount
to look at near objects
- the ciliary muscles contracts which slackens the suspensory ligements
- the lens becomes fat
- this increases the amount by which it refracts light
long and short sightedness can be corrected
- short sighted people are unable to focus on distant objects, this occurs when the cornea or lens bends the light too much or the eyeball is too long. the images of distant objects are brought into focus in front of the retina
- long sighted people are unable to focus on near objects. This occurs when the cornea or lens does not bend the light enough or the eyeball is too short. the images of near objects are brought into focus behind the retina.
what are hormones
hormones are chemicals released directly into the blood. theyre carried in the blood plasma to other parts of the body, but only affect particular cells (called target cells) in particular places, hormones control things in organs and cells that need constant adjustment
where are hormones produced
in glands. they travel quite slowly and tend to have relatively long lasting effects
state –> each different hormones in the body has its own job
adreneline
source - adrenal glands
role - readies the body for a fight of flight response
effects - increases heart rate, blood flow to muscles, and blood sugar level
insulin
source - pancreas
role - helps control the blood sugar level
effects - stimulates the liver to turn glucose into glycogen for storage
testosterone
source - testes
role - main male sex hormone
effects - promotes male secondary characteristics (eg facial hair)
progesterone
source - ovaries
role - supports pregnancies
effects - maintains the lining of the uterus
oestrogen
source - ovaries
role - main female sex organ
effects - controls the menstrual cycle and promotes female secondary sexual characteristics (eg widening of the hips)
ADH
source - pituitary gland
role - controls water content
effects - increases the permeability of the kidney tubules to water
FSH
source - pituitary gland
role - female sex hormone
effects - causes an egg to mature in an ovary and stimulates the ovaries to produce oestrogen
LH
source - pituitary gland
role - female sex hormone
effects - stimulates the release of an egg from an ovary
the differences between nerves and hormones
nerves - very fast message, act for a very short time, act on a very precise area
hormones - slower message, act for a long time, act in a more general way
if the response is very quick its probably…
nervous
if a response lasts for a long time its probably
hormones
what is homeostasis
is the maintenance of a constant internal environment
homeostasis
conditions in your body need to be kept steady so that cells can function. this involves balancing inputs
balancing inputs with outputs
water content - you need to keep a balance between the water you gain and the water you lose
body temperature - you need to get rid of excess body heat when you’re hot, but retain heat when the environment is cold
state –> water is taken into the body and lost from the body
what are the various ways that water is lost from the body
- through the skin as sweat
- via the lungs in sweat
- via the kidneys as urine
hot day - urination
- on a hot day, or when you are exercising you sweat a lot
- you will produce less urine, but this will be more concentrated (deeper colour)
- you will also lose more water when you exercise because you breathe faster
cold day - urination
- on a cold day or when you are not exercising , you do not sweat as much
- you will produce more urine, which will be more pale (since the waste carried in the urine is more diluted)
why does the body try to maintain at a body temperature of 37 degrees
all enzymes work best at a certain optimum temp
why does a part of the brain act as your own personal thermostat
- it is sensitive to the blood temperature in the brain, and it receives messages from temperature receptors in the skin that provide information about the skin temperature
- based on the signals from these receptors, your CNS can activate the necessary effectors to make sure your body temperature stays just right.
what happens when you are too hot
- lots of sweat is produced - when it evaporates it transfers energy from your skin to the environment, cooling you down
- blood vessels close to the surface of the skin widen - this is called vasodilation. It allows more blood to flow near the surface so it can transfer more energy into the surroundings, which cools you down
- hairs lie flat
what happens when you are too cold
- very little sweat is produces
- blood vessels near the surface of the skin constrict (vasoconstriction) This means less blood flows near the surface, so less energy is transferred to the surroundings
- you shiver, which increases your rate of respiration, which transfers more energy to warm the body, exercise does the same
- hairs stand on end to trap an insulating layer of air, which helps to keep you warm
state –> smaller organisms can cool down quicker
smaller organisms have a bigger…
surface area to volume ratio
why can organisms with bigger surface area to volume ratio gain or lose heat faster
- because there is more area for the heat to transfer across.
- this allows small organisms to lose body heat more easily in hot climates and reduces the chance of them overheating. it also means that they are very vulnerable in cold enviroments
why do organisms with small surface area to volume ratios gain or lose heat more slowly
- because there is less area for the heat to transfer across
- this is why animals living in cold conditions have a compact shape to keep their surface area to a minimum, reducing heat loss.
how do plants increase their chances of survival
by responding to changes in their environment. for example:
- they can sense the direction of light and grow towards it to maximise light absorption for photosynthesis.
- they can sense gravity, so their roots and shoots grown in the right direction
- climbing plants have a sense of touch, so they can find things to climb and reach the sunlight
how are plants more likely to survive from predators
if they respond to the presence of predators to avoid being eaten
how are plants also more likely to survive
if they respond to abiotic stress
what are auxins
auxins are plant hormones which control growth at the tips of shoots and roots
how do auxins move
through the plant in solution (dissolved in water)
where are auxins produces and how are they diffused and why
they are produced in the tips and diffuses backwards to stimulate the cell elongation process which occurs in the cells just behind the tips
state –> auxins promotes growth in the shoot, but actually inhibits growth in the root
state –> auxins are involved in the growth responses of plants to light (phototropism) and gravity (geotropism)
state –> auxins change the direction of root and shoot growth
shoots are positively phototrophic
( grow towards light)
- when a shoot tip is exposed to light, it accumulates more auxin on the side that’s in the shade than the side that is in the light
- this makes the cell grow (elongate) faster on the shaded side so the shoot bends towards the light
roots are negatively geotropic
(grow away from gravity)
- when a shoot is growing sideways, gravity produces un-unequal distribution of auxin in the tip, with more auxin on the lower side
- this causes the lower side to grow faster, bending the shoot upwards
roots are positively geotropic
(grow towards gravity)
- a root growing sideways will also have more auxin on its lower side
- but in a root the extra auxin inhibits growth. this means that the cells on top elongate faster, and the root bends downwards
roots are negatively phototropic
(grow away from light)
- if a root starts being exposed to some light, more auxin accumulates on the more shaded side
- the auxin inhibits cell elongation on the shaded side, so the root bends downwards, back into the ground.
state –> roots that are underground are not exposed to light. they grow downwards due to positive gravitropism
