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