B10 Flashcards
What is the eye?
The eye is a sense organ containing receptors sensitive to light intensity and colour.
What is the sclera? And what does it do ?
It is the tough outer layer of the eye and it protects and holds the eye in place.
What is the retina?
It is the back of the eye and is made up of light-sensetive receptor cells. It contains rod and cone cells.
What is the optic nerve?
It carries impulses from the retina to the brain
What is the cornea?
It is the transparent region of the sclera at the front of the eye that refracts light - bends it as it enters the eye.
What is the iris?
It has sets of muscles that control the size of the pupil and regulate the light reaching the retina
What do the Cilary muscles and suspensory ligaments do?
They change the shape of the lens to focus light rays on the retina
When reacting to light what does muscular iris do?
It controls the size of the pupil
What happens when your eye reacts to bright light?
-The circular muscles contract
-The radial muscles relax
-Pupil constricts
What is accommodation?
Accomodation is a reflex where your eye focuses on a near or distant object by changing the shape of the lens to focus the light onto the retina
What happens when your short sighted?
When your short sighted, your cant focus on distant objects because either your lens is too fat (thickned) so it refracts the light too much and the light focuses in front of the retina or your eyeball is too long
What is short sightedness caused by? (Myopia)
It is caused by the lens being too thick or by the eyeball being too long
What happens when your long sighted? (Hyperopia)
It is when light rays focus behind their retina - they cant refract enough
What is long sightedness caused by?
It is caused by the lens being too thin and the eyeball being too short
How to fix long/short sightedness?
By wearing glasses or contacts to help focus light onto the retina. Or by getting eye surgery to change the shape of the cornea with a laser to help the eye focus the light correctly onto the retina. Or by getting replacment lens surgery - natural lense of eye is removed and an artificial lens is replaced - made of clear plastic
What is homeostasis?
Homeostasis is all about the regulation of the conditions inside your body to maintain a stable internal environment in response to internal/external conditions
What are the 2 types of automatic control systems inside your body that regulate your internal environment?
Nervous and hormonal communication systems
What are your control systems made out of?
All your automatic control systems are made up of 3 main components which work together to maintain a steady condition (homeostasis) - cells called receptors, coordinations centres and effectors
What is a negative feedback loop?
When the level of something gets too low or too high your body uses a negative feedback loop to bring it back to normal
Explain a negative feedback loop
- Receptors detect a stimulus - level is too high
- The coordination centre recieves and processes the information, then organises a response
- Effector produces a response which counteracts the change and restores the optimum level - the level then decreases
This is also the same the other way around so when a level of something is too low your body counteracts it to make it come back to normal
Effectors will carry on producing the responses for as long as they’re stimulated by the coordination center.
This process happens automatically
What is a stimulus?
It is a change in environment
What is your nervous system made out of?
- CNS - consists of brain and spinal cord only, in mammals the CNS is connected to the body by sensory neurones and motor neurones
- Sensory Neurones - the neurones that carry information as electrical impulses from the receptors to the CNS
- Motor neurones - The neurones that carry electrical impulses from the CNS to effectors
- Effectors - All your muscles and glands which respond to the impulses
What are the receptors and effectors?
Receptors are the cells that detect stimuli
Effectors respond to nervous impulses and bring about a change ( muscles and glands ). Muscles contract in response and glands secrete hormones in response
What do relay neurones do?
They connect motor neurones and sensory neurones
What are synapses and how do they work?
The connection between 2 neurones is called a synapse
The nerve signal is transferred by chemicals which diffuse across the gap
These chemical reactions then set off a new electrical signal in the next neurone
What do reflexes do and what are they?
Reflexes are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain - they can reduce the chances of you getting injured
Explain a reflex arc / action
Your receptors pick up a stimulus and send a electrical signal along a sensory neurone to a relay neurone in the CNS, then when the impulses reach a synapse between a sensory neurone and a relay neurone, they trigger chemicals to be released and these chemicals cause impulses to be sent along the relay neurone, then when the impulse reach another synapse, the same thing happens but this time the impulses are sent across a synapse to the motor neurone. Then the impulse travels along the motor neurone to the effector ( muscle or gland ) and this then causes the muscle to contract ( triggers a response )
How can you measure reaction times? (Practical)
use the ruler drop test to see your reaction to a visual stimulus
What is the celebral cortex?
This is the outer wrinkly bit. It’s responsible for things like consciousness, intelligence, memory and language.
What is the medulla?
Controls unconscious activities (things you don’t have to think about doing) like breathing and your heartbeat.
What is the Cerebellum?
Responsible for muscle coordination.
Explain all the ways that you can study the brain
Studying patients with brain damage - If a small part of the brain has been damaged, the effect this has on the patient can tell you a lot about what the damaged part of the brain does.
Electrically stimulating the brain - The brain can be stimulated electrically by pushing a tiny electrode into the tissue and giving it a small zap of electricity. By observing what stimulating different parts of the brain does, it’s possible to get an idea of what those parts do.
MRI scans - A magnetic resonance imaging (MRI) scanner is a big fancy tube-like machine that can produce a very detailed picture of the brain’s structures. Scientists use it to find out what areas of the brain are active when people are doing things like listening to music or trying to recall a memory.
What are the consequences of studying the brain?
1) Knowledge of how the brain works has led to the development of treatments for disorders of the nervous system. For example, electrical stimulation of the brain can help reduce muscle tremors caused by nervous system disorders such as Parkinson’s disease.
2) However, the brain is incredibly complex and delicate - the investigation of brain function and any treatment of brain damage or disease is difficult. It also carries risks, such as physical damage to the brain or increased problems with brain function
What happens to your eyes in dim light?
Radial muscles contract and the circular muscles relax, which makes the pupil wider
What do automatic control systems do ?
They regulate your internal environment
Why is treating the brain very difficult ?
-the brain is encased in a skull so its hard to get to
-many things can go wrong when operating on a brain - physical damage, infection etc.
-because its so complex - it’s hard to target with medication
What is the hypothalamus responsible for ?
It’s responsible for regulating our body temperature
Where is the medulla found ?
In the brain stem
What is the pupil ?
It is the gap through which light passes through to get to the lens
What are the two types of receptor cells in the retina ? And what do they do ?
Rod and cone cells
Rod cells detect the presence of light or the absence of light
Cone cells detect Colour
What is the fovea ?
It is the place where light focuses on the retina - it contains the highest concentration if cone cells and gives the sharpest image
Whats the iris reflex used for ?
To ensure that the optimum amount of light enters the eye and to prevent the eye from getting injured from lots of BRIGHT light entering the eye as bright light can damage the retina
