B10 Flashcards
What is homeostasis?
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal or external change.
What does homeostasis control?
Body temperature, the water content in your body and the glucose concentration in your blood.
What are the receptors?
Cells that detect changes in the internal or external environment(stimuli).
What is a coordination centre?
Areas that receive and process the information from the receptors, sending signals to coordinate a response.
What are effectors?
The muscles or glands that bring about responses to the stimulus that has been received.
What is a nerve?
A bundle of neurones which are special cells that send electrical impulses.
How does the nervous system work?
The impulse from the receptor travels to the sensory neurones where it gets lots of information. It then goes to the relay neurone and the CNS. It is then passed to the motor neurone to carry information from the CNS to your body then the effectors respond.
What are reflexes?
Automatic responses that help to make basic bodily functions work.
What is a reflex arc?
It goes from the receptor, along the sensory neurones, through the relay neurone and along the motor neurone. Then it arrives at the effector organ through the reflex arc.
How do synapses work?
There is a diffusion of a chemical across the synapse which causes the next neurone to set up a new electrical impulse.
What is the cerebral cortex?
Concerned with consciousness, intelligence, memory and language. Also our senses. It is split up into left and right hemispheres, each corresponding with the opposite side of our bodies.
What is the cerebellum?
It coordinates muscular activity and balance.
What is the medulla?
Concerned with unconscious activities such as controlling the heart beat.
What is the hypothalamus?
It is responsible for regulating body temperature and sending signals to the pituitary gland.
How can scientists study brain damage?
They can use MRI scans, or electrically stimulate different areas of the brain by mapping the different functions. They also study people with brain damage.
Why is treating the brain so difficult?
As there is a wide range of things that can go wrong, it is fragile and difficult to fix with drugs and chemicals.
What is the eye?
A sense organ containing many receptors that are sensitive to light intensity and colour. The cells are arranged in the back of the eye known as the retina.
What is the sclera?
The tough white outer layer of the eye which has a transparent area at the front of the eyeball called the cornea, letting light into the eye and as it is curved it means the light will always be focused on the retina.
What does the iris do?
It is the hole where light entered and is made of muscles to contract or relax to change the size of the pupil to control the amount of light reaching the retina so the cells are not damaged.
Where is the lens held?
They are held by suspensory ligaments and the ciliary muscles which change the direction of the lens to produce a clear image.
How does the eye produce an image?
When the light hits the retina, light-sensitive cone cells are stimulated, sending impulses to the brain along sensory neurones in the optic nerve.
How would you focus on a distant image?
You would relax the ciliary muscles so the suspensory ligaments are pulled tight and the lens is pulled flat and thin. It only refracts light rays slightly so they are focused on the retina.
How would you focus on a near image?
The ciliary muscles contract so the suspensory ligaments loosen. The lens is then thicker and more curved. It refracts light rays strongly so they are focused on the retina.
What is Myopia?
It is when you can see close objects in clear focus, but distant objects look blurred called short-sightedness. The light is focused in front of the retina, as a result of a lens that is too curved or a particularly long eyeball.
What is Hyperopia?
When you can focus clearly on distant objects but close objects appear blurred. This may be a result of a lens that is too flat and thin or of a particularly short eyeball. As a result, the lens cannot refract the light strongly enough so the image forms after the retina.
What are contact lenses?
They are lenses doing the same job as glasses.
What is laser eye surgery?
It is used to treat myopia by reducing the thickness of the cornea so it refracts the light less strongly. It also treats hyperopia where it changes the curve of the cornea so it refracts light from close object more effectively.
What are replacement lenses?
Putting another lens inside the eye to correct the visual defect permanently. This can be done by implanting a contact lens into the eye and the natural lens being left or the faulty lens being replaced by an artificial lens.
What are cone cells?
They are cells in the retina that show the colour of light.
What are rod cells?
They are cells in the retina more sensitive to light, only showing black and white.
What is the fovea?
It is the spot on the retina with only cone cells, where light is focused on most of the time.
What is the cornea?
It is the transparent thing on the edge of your eyeball, which has no blood vessels. Oxygen has to diffuse in through air and it causes light to refract.
How is the size of the pupil changed?
It is made larger through the radial muscles contracting and the circular muscles relaxing and for smaller vice versa.
What is accommodation?
It is the reflex that changes the refractive power of the lens, whether it is near or distant.
What is thermoregulation?
It is the control of our internal body temperature to maintain optimum enzyme activity levels.
What is a thermoregulatory center?
It is the hypothalamus of our brain and it gets information from our receptors of which if we are too hot or cold it sends information to our effectors making a change.
What are the mechanisms to warm us up?(3)
Constricting blood vessels by vasoconstriction, erector muscles making a layer of insulation, shivering causes energy to be released.
What are the mechanisms to cool us down?(3)
Blood vessels relaxed by vasodilation, erector muscles relaxed and sweating causing heat to be taken when it evaporates.
What is a sensory neurone?
It carries information from receptors to the CNS.
What is a motor neurone?
It carries information from the CNS to effectors.
