6)Coordination and Response Flashcards
How does responding to the environment help organisms survive?
- Animals can increase their chance of survival by responding to changes in their external environment
- They can also control their internal environment
What is a change in the internal or external environment called?
A stimulus (plural stimuli)
What do receptors detect?
A receptor detects stimuli
What do receptors in the sense organs detect?
They are group of cells that detect external stimuli
What are the sense organs?
The eyes, ears, nose, tongue and skin
What are effector cells?
Bring a response to stimuli
How do receptors communicate with effectors?
Via the nervous system, the hormonal system but sometimes both
What is the CNS?
Central Nervous System
What are the main type of neurons?
- Sensory
- Relay
- Motor
What does the CNS consist of?
Brain and spinal cord
What happens when receptors in a sense organ detect a stimulus?
They send electrical impulses along the sensory neurons to the CNS. Then the CNS sends electrical impulses to an effector along a motor neuron.
What is the main job of the CNS?
Its to coordinate the response
What do coordinated responses always need?
A stimulus, a receptor and an effector
Why can the nervous system bring about very rapid responses?
Because neurons transmit information using high speed electrical impulses
What are reflexes?
Reflexes are automatic responses to certain stimuli, they can reduce the chances of being injured
What happens if someone shines a bright light in your eyes?
Your pupils automatically get smaller so that less light gets into the eye - this stops it getting damaged
What is the conjunctiva?
Lubricates and protects the surface of the eye
What is the cornea?
The cornea 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 is the iris?
Controls the diameter of the pupil and therefore how much light enters the eye
What do the lens do?
The lens focusses the light onto the retina
What does the optic nerve do?`
Carries impulses from the receptors to the brain
What is the iris reflex?
Adjusting for bright light
How do you look at distant objects?
1) The ciliary muscles relax
2) This makes the lens go thin
How can you look at near objects?
1) The ciliary muscles contract
2) The lens become more fat (more curved)
What is the difference between long sighted people and short sighted people?
- Long sighted people are unable to focus on near objects
- Short sighted people are unable to focus on distant objects
What is ADH? (Give the source, role and effect)
- Source: Pituitary gland
- Role: Controls water content
- Effects: Increases the permeability of the kidney tubes to water
What is adrenaline? (Give the source, role and effect)
- Source: Adrenal glands
- Role: Readies the body for a ‘fight or flight’ response
- Effect: Increases heart rate, blood flow to muscles and blood sugar level
What is insulin? (Give the source, role and effect)
-Source: Pancreas
-Role: Helps control blood sugar level
Effect: Stimulates the liver to turn glucose into glycogen for storage
What is testosterone? (Give the source, role and effect)
- Source:Testes
- Role: Main male sex hormone
- Effect: Promotes male secondary characteristics
What is progesterone? (Give the source, role and effect)
- Source: Ovaries
- Role: Supports pregnancy
- Maintains the lining of the uterus
What is oestrogen? (Give the source, role and effect)
- Source: Ovaries
- Role: Main female sex hormone
- Effect: Controls the menstrual cycle and promotes secondary sexual characteristics
What are the three things that nerves do?
1) Send a very fast message
2) Act for a short time
3) Act on a precise area
What are the three things that hormones do?
1) Send a slower message
2) Act for a longer time
3) Act in a more general way
What does it mean if a response is really quick?
Its nervous
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment
Give two examples of homeostasis
1) Water content
2) Body temperature
Name three ways of how water is lost through the body
1) Through the skin as sweat
2) Via the lungs in breath
3) Via the kidneys as urine
What is the optimum body temperature and why?
- 37°C
- Enzymes work best at this temperature
What does the skin do when you’re too hot?
- When sweat is produced it evaporates which transfers heat, which cools the body down
- Blood vessels close to the skin widen
- Hair lies flat
What is it called when blood vessels widen?
Vasodilation
What does the skin do when you’re too cold?
- Very little sweat is produced
- Blood vessels near the surface constrict
- You shiver, which generates heat in the muscles
- Hairs stand up on end
How does a plant increase their chances of survival?
By responding to their environment
Give twoexamples of how a plant responds to their environment
1) They sense the direction of light and grow towards it to maximize light absorption for photosynthesis
2) They sense gravity
What are auxins?
Auxins are plant hormones that control growth at the tips of shoots and roots
Where is auxin produced?
Auxin is produced in the tips and diffuses backwards to stimulate the cell elongation process, which occurs in the cells just behind the tips
What is the response to light called?
Phototropism
What is the response to gravity called?
Geotropism
What does it mean if a shoot is positively phototrophic?
It grows towards light. The shoot will bend towards the light
What does it mean if a shoot is negatively geotrophic?
It grows away from gravity
What does it mean if a root is positively geotrophic?
It grows towards gravity
