Section 6 - Coordination and Response P1 Flashcards
What changes do animals respond to?
And why?
-changes in their external environment
-changes in their internal environment(to make sure conditions are always right)
To increase their chance of survival
What changes do plants respond to?
They increase their chance of survival by responding to changes in their environment
What’s a stimulus?
Any change in the internal or external environment is called a stimulus.
What do receptors do?
Receptors detect stimuli.
Receptors in the sense organs are groups of cells that detect external stimulus.
What are the sense organs?
Eyes, ears, nose, tongue, skin
What do effectors do?
And what’re examples of effectors?
Effectors are cells that bring about a response to stimuli.
E.g.
Muscle cells contract
Glands secrete hormones
How do receptors communicate with effectors?
They communicate via the nervous system or the hormonal system or both
What’s the nervous system made up of?
Neurones (nerve cells)
What are the three main types of neurones?
- sensory neurone
- relay neurone
- motor neurone
What’s the CNS made up of?
And what’s its function?
CNS- Central Nervous System
-consists of the brain and spinal cord only
Function- to coordinate the response, coordinated responses always need a stimulus, receptor and an effector
What detects a stimulus, and what happens once a stimulus is detected?
receptors 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
Why is the nervous system able to bring about very rapid responses?
Because neurones transmit information using high speed electrical impulses
What’s a synapse?
The connection between two neurones is a synapse
How do synapses work?
- the nerve signal is transmitted by chemicals called neurotransmitters which diffuse across the gap
- these chemicals then set off a new electrical signal in the next neurone
What’re reflexes?
Reflexes are automatic responses to certain stimuli
-they can reduce the chances of being injured
What’s a reflex arc?
A reflex action follows this general sequence and does not involve the conscious part of the brain, which makes it much quicker.
What’s the sequence of a reflex arc?
Stimulus Receptor Sensory neurone Motor neurone / CNS Motor neurone Effector Response
What coordinates the response in a reflex?
The spinal cord or an unconscious part of the brain
What’s the process that goes on in a reflex action?
- a stimulus is detected by receptors and an impulse is sent along a sensory neurone to the CNS
- the CNS then passes on the message to a relay neurone
- the relay neurones relay the impulse to a motor neurone
- the impulse then travels along the motor neurone to the effector
- then the response happens
What is the conjunctiva in the eye?
The conjunctiva lubricates and protects the surface of the eye
What is the sclera in the eye?
The sclera is the tough outer layer that protects the eye
What is the cornea in the eye?
The cornea refracts light into the eye.
-it’s transparent and has no blood vessels to supply it with oxygen, so oxygen diffuses in from the outer surface
What is the iris in the eye?
The iris controls the diameter of the pupil and therefore how much light enters the eye
What is the lens in the eye?
The lens focuses the light onto the retina
What is the retina in the eye?
The light-sensitive part, it’s covered in light receptors called rods and cones
- cones are sensitive to colours, not dim light
- rods can’t sense colours, sensitive in dim light
Where are the most cones found in the eye?
Cones are found all over the retina, but there are loads of them at the fovea
What is the optic nerve in the eye?
The optic nerve carries impulses from the receptors to the brain
What can very bright light do to your eye?
Very bright light can damage your retina
-so you have a reflex to protect it
What is the reflex that happens in your eye when it is in bright light?
Your pupil becomes smaller letting less light in, by the circular muscle contracting
What is the reflex that happens in your eye when it is in dim light?
The brain tells the radial muscle to contract, which makes the pupil bigger
What is the eye focusing light on the retina by changing the shape of the lens called?
And what is the eye focusing on near and distant objects called?
- accommodation
- a reflex
What happens in the eye for it to see objects in the distance?
- the ciliary muscles relaxes which allows the suspensory ligaments to pull tight
- makes the lens go thin (less curved)
- so it refracts light by a smaller amount
What happens in the eye for it to see objects close up?
- the ciliary muscles contract which slackens the suspensory ligaments
- lens becomes fat (more curved)
- increases the amount by which it refracts light
What generally happens to you eyes when you get older?
Your eye’s lens loses flexibility
- so it can’t spring back to a round shape
- so light can’t be focused well for near viewing (so reading glasses are required)
What does it mean to be short sighted?
To be unable to focus on distant objects
- 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
What does it mean to be long sighted?
To be unable to focus on near objects
- occurs when the cornea or lens doesn’t 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?
Chemicals which are released directly into the blood
- carried by blood plasma
- only affects target cells
- travel slowly and have relatively long-lasting effects
What do hormones control?
Hormones control things in organs and cells that need constant adjustment
Where are hormones produced?
in glands
What is the source, role and effects of adrenaline?
Source: Adrenal glands
Role: Readies the body for a ‘fight or flight’ response
Effects: Increases heart rate, blood flow to muscles and blood sugar level
What is the source, role and effects of insulin?
Source: Pancreas
Role: Helps control blood sugar level
Effects: Stimulates the liver to turn glucose into glycogen for storage
What is the source, role and effects of testosterone?
Source: Testes
Role: Main male sex hormone
Effects: Promotes male secondary sexual characteristics
What is the source, role and effects of progesterone?
Source: Ovaries
Role: Supports pregnancy
Effects: Maintains the lining of the uterus
What is the source, role and effects of oestrogen?
Source: Ovaries
Role: Main female sex hormone
Effects: Controls the menstrual cycle and promotes female secondary sexual characteristics
What’s the difference between nerve and hormonal responses?
Nerves
-fast message, act for a very short time, on a very precise area
Hormones
-slower message, for a long time, act in a more general way
Define homeostasis:
Homeostasis is the maintenance of a constant internal environment
What’re two examples of homeostasis?
Body water content
Body temperature
How is body water content an example of homeostasis?
You need to keep a balance between the water you lose and the water you gain
(you lose water by: sweating, breathing, urine)
How is body temperature an example of homeostasis?
You need to get rid of excess body heat when you’re hot, but retain heat when the environment is cold
(all enzymes work best at the a certain optimum temperature)
What does your body do if you are too hot?
- sweats (when it evaporates it cools you down)
- blood vessels close to the surface of the skin widen (vasodilation), so more energy can be transferred to the surroundings
- hair lie flat
What does your body do if you are too cold?
- very little sweat is produced
- blood vessels near the surface of the skin constrict (vasoconstriction), less energy transferred to surroundings
- shivering, increasing the rate of respiration (exercise does the same)
- hairs stand on end to trap an insulating layer of air, to keep you warm
Why do smaller organisms cool down quicker than larger ones?
smaller organisms have bigger surface area to volume ratios
-so they can gain or loose heat quicker than bigger ones
What do plants do to increase the chances of their survival?
- sense the direction of light and grow towards it
- sense gravity, so their shoots and roots grow in the right direction
- climbing plants have the sense of touch so they can climb things and reach sunlight
What is an example of how plants respond to the presence of predators?
white clover
-produces substances that are toxic to cattle to deter them
What is an example of how plants can respond to abiotic stress?
carrots
-produce antifreeze proteins at low temperatures, to prevent freezing
What are auxins?
Plant hormones which control the growth at the tips of shoots and roots
-they move through the plant in solution
What do auxins cause in plants?
- produced at the tips and diffuse back, to stimulate cell elongation process (which occurs just behind the tip)
- promotes growth in shoot and inhibit it in the roots
- involved in phototropism and geotropism responses
What is the phototropic response in a plant shoot?
SHOOTS ARE POSITIVELY PHOTOTROPHIC
- when a shoot tip is exposed to light, it accumulates more auxin on the side that is in the shade
- makes the cells elongate in the shade, causing the shoot to bend towards the light
What is the geotropic response in a plant shoot?
SHOOTS ARE NEGATIVELY GEOTROPIC
- when a shoot is growing sideways, auxin is forced towards gravity
- causing the cells to elongate, so the shoot bends up
What is the phototropic response in a plant root?
ROOTS ARE NEGATIVELY PHOTOTROPHIC
- if a root is exposed to light, more auxin accumulates on the shaded side
- auxin inhibits growth on the shaded side, so the root bends back downwards
What is the geotropic response in a plant root?
ROOTS ARE POSITIVELY GEOTROPIC
- a root growing sideways will have more auxin on its lower side
- extra auxin inhibits growth, so the root bends down
What is the structure of a neurone?
A long fibre (axon) which is insulated by a fatty (myelin) sheath. They are long so they can carry messages up and down the body. Tiny branches (dendrons) which branch further as dendrites at each end. These receive incoming impulses from other neurones. (the end with the nucleus)
What is Etiolation?
When a plant is grown in the dark it grows very tall and thin as it puts all of its energy into growing towards the light and away from gravity so that it can photosynthesise
