Paper 2 Biology Flashcards
What is homeostasis
homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum
conditions for function in response to internal and external changes
Order of negative feedback
Receptors - detect a stimulus
Coordination centre - receives and processes information then organises a response
Effectors - produce a response which counteracts the change level and restore the optimum level
Effectors can be either
Muscles or glands
What is stimulus
A change in environment
Examples of coordination center
Brain
Spinal cord
Pancreas
What part of the body is the CNs
Brain and spinal cord
How is the CNS connected to the body
By sensory neurones and motor neurones
What does CNS stand for
Central nervous system
What is the sensory neurone
The neurone that carries information as electrical impulses from the receptors to the CNS
What are motor neurones
The neurones that carry electrical impulses from the CNS to effectors
What are the effectors
All your muscles and glands as they respond to nervous impulses
Why are muscles and glands known as effectors
Muscles - cuz they contract in response to a nervous impulse
Glands - cuz they secrete hormones
Example of a receptor
The retina of the eye is covered in light receptor cells
Taste receptors
Sound receptors
Reflex actions
Are automatic and rapid
Not involving the conscious part of the brain
Synapses
The connection between two neurones are called synapses
The nerve signal is transferred by chemicals which diffuse across the gap
These chemicals set off a new electrical signal in the next neurone
A reflex arc
The passage of Information in a reflex ( from receptor to effector )
What is the cerebral cortex
It is the outer wrinkly bit and it is responsible for the intelligence,memory , consciousness and language
Medulla
Controls unconscious activities like breathing and heartbeat
Cerebellum
Responsible for muscle coordination
Methods used by scientists to study the brain
MRI scan
Studying people with brain damage
Electrically stimulating the brain
Explain how to electrically stimulate the brain
By pushing an tiny electrode into the tissue and giving it small zaps of electricity
By observing what stimulating different parts of the brains does it is possible to get an idea of what those parts of the brain do
E.g when the motor area in the brain is stimulated it causes muscle contraction and movement
What does mri stand for
Magnetic resonance imaging
What is an mri scanner
It is a machine that produces detailed images of the brain structure and detects what part is being stimulated when doing certain activities like listening to music or trying to recall a memory
Studying people with brain damage
For instance if a small part of the brain is damaged and it results in vision loss we can come to the conclusion that the part of the brain that was damaged has to do with vision loss
Difficulty with investigating brain function and treating brain damage /disease
Physical damage to the brain
Increased problem with brain function eg difficulty with speech
Sclera
The tough supporting wall of the eye
What is the eye
The eye is a sense organ containing receptors sensitive to light intensity and colour
Cornea
The transparent outer layer found at the front of the eye
It refracts light into the eye
The iris
Contains muscles that allow it to control the diameter of the pupils and therefore how much light enters the eye
The lens
Focuses the light onto the retina
Retina
Contains receptor cells sensitive to light intensity and colour
What controls the shape of the lens
Ciliary muscles
Suspensory ligaments
The optic nerve
Carries impulses from the receptors on the retina to the brain
What is accommodation
The process of changing the shape of the lens to focus on near or distant objects
To focus on a near object
• the ciliary muscles contract
•the suspensory ligaments loosen
• the lens is then thicker and refracts light rays strongly.
To focus on a distant object
• the ciliary muscles relax
• the suspensory ligaments are pulled tight
• the lens is then pulled thin and only slightly refracts light rays.
Myopia
Shortsightedness
Explain the iris reflex
When the light receptors in your eyes detect a very bright light , a reflex is triggered causing the pupil to become smaller
The circular muscle in the iris contracts and the radial muscle relaxes
This reduces the amount of light that can enter the eye
And the opposing the light is too dim
Hyperopia
Longsightedness
What causes long sighted ness
When the lens is the wrong shape and doesn’t refract the light enough or the eye ball is too short
The image of near objects are brought into focus behind the retina
What type of glasses do long sighted people wear
Cortex lens glasses
( a lens which curves outwards to correct it
The lens refracts the light rays so they focus on the retina
What causes shortsightedness
This occurs when the lens is the wrong shape and refracts too much light into the light or the eye is too long
The image of distant objects is brought into focus in front of the retina
What type of glasses do short sighted people use
Concave lens glasses
A lens which curves inwards to correct it so that the light rays focus on the retina
The treatment for vision defects
Contact lenses
Laser eye surgery
Replacement lens surgery