Coordination and Response Flashcards
What is a stimulus?
Any change in the internal or external environment
What are receptors?
- Detect Stimuli
- The sense organs (eyes, ears, mouth, nose, skin)
What are effectors?
- Cells that bring about a response to a stimuli
- Muscle cells contract and cells in glands secrete hormones
How do receptors communicate with effectors?
Via the nervous system or hormonal system, or sometimes both
What does the CNS consist of?
Central Nervous System
Brain and spinal chord only
What are synapses?
The connection between two neurones
Nerve signal is transferred by chemicals which diffuse across the gap, setting off a new electrical signal in the next neurone
What are reflexes?
Automatic responses to certain stimuli; usually to prevent injury
What are reflex arcs?
The route taken by the information in the reflex (receptor to effector)
What is the simplest explanation of a reflex arc ?
Stimulus
Receptor
Sensory Neurone
CNS
Motor Neurone
Effector
Response
Describe your body’s reaction when a finger touches a flame
- The candle (stimulus) burns the finger (receptor)
- Stimulation of pain sends an electrical impulse down the sensory neurone to the CNS
- At the CNS, the sensory neurone passes the impulse onto a relay neurone
- The impulses travel along onto a motor neurone
- When the impulses reach the muscles, they contract
Describe your eye’s reaction to a sudden change in light, from dim to bright
- The bright light (stimulus) are detected by the light receptors in the eye
- Impulses are sent down the sensory neurone to the CNS
- Impulses go from the CNS to the relay neurone
- Impulses go through the motor neurone, via synapses and cause the circular muscles to contract
- The pupil gets smaller
What is the sclera?
A tough outer layer that protects the eye
What is the cornea?
Refracts light into the eye
Transparent with no blood vessels; oxygen diffuses from the surface
What is the iris?
Controls the diameter of the pupil, and how much light enters the eye.
Made of circular muscles and radial muscles
What is the pupil?
The hole in the middle of the eye
What is the lens?
Focuses light on the retina
What is the retina?
The light sensitive part of the eye. Covered in rods and cones
When are rods more sensitive?
Dim light, but can’t sense colour
What are cones more sensitive to?
Colour, but not good in dim light
What is the optic nerve?
Carries impulses from the receptors to the brain
What happens to the iris in bright light?
The circular muscles contract and the radial muscles relax, making the pupil smaller
What happens to the iris in dim light?
The radial muscles contract and the circular muscles relax, making the pupil bigger
How does the shape of the lens change when looking at distant objects?
The ciliary muscles relax and the suspensory ligaments contact
This stretches the lens, making it long and thin (able to attract all the scattered light rays)
Refracts the light by a smaller amount
How does the shape of the lens change when looking at near objects?
The ciliary muscles contract and the suspensory ligaments relax
This shortens the lens, making it fat and short
Refracts the the light by a larger amount
What are short-sighted people unable to focus on? (Hyperopia)
Distant objects
Cornea or lens bend the light too much, causing the image to be brought into focus in front of the retina
What are long-sighted people unable to focus on? (Myopia)
Near objects
Cornea or lens don’t bend the light enough, causing the image to be brought into focus behind the retina
What are hormones?
Chemical messengers carried in the blood plasma to other parts of the body
Where are hormones produced?
Glands
Where is adrenaline made?
The adrenal glands (on top of the kidneys)
What is the role of adrenaline?
Readies the body for a ‘fight or flight’ response
What are the effects of adrenaline?
Heart rate increases, pupils dilate, blood flows to muscles and blood sugar increases
Where is insulin made?
Pancreas
What is the role of insulin?
Control the body’s sugar levels
What are the effects of insulin?
Stimulates the liver to turn glucose into glycogen for storage
Where is testosterone made?
Testes
What are the effects of testosterone?
Promotes male secondary sexual characteristics
What is the role of testosterone?
Main male sex hormone
What is the role of progesterone?
Supports pregnancy
Where is progesterone made?
Ovaries
What are the effects of progesterone?
Maintains the lining of the uterus
Where is oestrogen made?
Ovaries
What is the role of oestrogen?
Main female sex hormone
What are the effects of oestrogen?
Controls the menstrual cycle
Promotes secondary female sexual characteristics
What does ADH stand for?
Anti-Diuretic Hormone
Where is ADH made?
Pituitary glands
What is the role of ADH?
Control water content in the body
What are the effects of ADH?
Increases the permeability of the water tubules
What does FSH stand for?
Follicle Stimulating Hormone
What does LH stand for?
Luteinising Hormone
Where is FSH made?
Pituitary gland
Where is LH made?
Pituitary gland
What is the role of FSH?
Female sex hormone
What is the role of LH?
Female sex hormone
What are the effects of FSH?
Causes an egg to mature in the ovary
Stimulates the ovary to produce oestrogen
What are the effects of LH?
Stimulates the release of an egg from an ovary
What are the characteristics of a nervous message?
- Very fast message
- Act for a very short time
- Act on a very precise area
What are the characteristics of a hormonal message?
- Slower message
- Act for a long time
- Act in a more general way
What is homeostasis?
The maintenance of a constant internal environment
Why do conditions in the body need to be kept steady?
So that cells can function properly. Involves balancing inputs and outputs
How is water taken into the body?
Food and drink
How is water lost from the body?
- Through the skin as sweat
- Through the lungs in breath
- Through the kidneys as urine
How much will you sweat on a hot day or when you’re exercising?
Sweat a lot
How much will you sweat on a cold day or when you’re not exercising?
Don’t sweat much
What will your urine be like on a hot day?
- Less urine produced
- More concentrated (deeper colour) urine
What will your urine be like on a cold day?
- More urine produced
- Less concentrated and pale (Waste carried in urine is more diluted)
What is the body’s optimum temperature?
37C
Why does the body maintain its temperature at 37C?
All enzymes work best at a certain optimum temperature. Most enzymes in the body work best at this temperature
What is vasodilation?
Blood vessels close to the surface widen to cool you down
This allows more blood to flow near the surface and transfer heat energy into the surroundings
What is vasoconstriction?
Blood vessels close to the surface narrow (constrict) to cool you down
This allows less blood to flow near the surface and less heat energy is transferred into the surroundings
What does your body do when it’s too hot?
- Lots of sweat is produced
- Vasodilation
- Hairs lie flat
What does your body do when it’s too cold?
- Very little sweat produced
- Vasoconstriction
- Shiver
- Hairs stand on end
Why does sweating cool you down?
When the sweat evaporates, it transfers energy from your skin to the environment, cooling you down
Why does shivering warm you up?
By shivering, you increase your rate of respiration
This transfers more energy to warm the body
Why does your hair stand on end when your cold?
They trap an insulating layer of air, which helps keep you warm
Why do smaller organisms cool down quicker?
Bigger SA:V
Can gain lose (or gain) heat faster because there is more area for the heat to transfer across
Why is it helpful to have a bigger SA:V in a hot climate?
Smaller organisms can lose heat more easily in hot climates, reducing the chance of them overheating
Why is it unhelpful to have a bigger SA:V in a cold climate?
Lose their body heat easily to the climate
What are auxins?
Plant growth hormones that control the growth at the tips of roots and shoots
What tropic responses does a shoot have?
Positive phototropism (grow towards light)
Negative geotropism (grow away from gravity)
What tropic responses do roots have?
Positive geotropism (grow towards gravity)
Negative phototropism (grow away from light)
What happens when a shoot is exposed to light? (positive phototropism)
- It accumulates more auxin in the side that’s in the shade than the side in the light
- Makes the cell elongate faster on the shaded side
- The shoot bends towards the light
What happens when a shoot is growing sideways? (negative geotropism)
- Gravity produces an unequal distribution of auxin at the tip, with more on the lower side
- Causes the lower side to grow faster, bending the shoot upwards
What happens when a root is exposed to light? (negative phototropism)
- More auxin accumulates on the shaded side
- The auxin inhibits cell elongation on the shaded side
- The root bends downwards into the ground
What happens when a root is growing sideways? (positive geotropism)
- Gravity produces an unequal distribution of auxin at the tip, with more on the lower side
- This extra auxin inhibits its growth
- The cells on top elongate faster and the root bends downwards
