B10 Flashcards
What is the retina
Made up of light -sensitive receptor cells
What is the optic nerve?
Carries impulses from the retina to the brain
What is the sclera?
The tough outer layer of the eye
What is the cornea?
Transparent region of the sclera at the front of the eye. Refracts light - bends it as it enters the eye
What is the iris?
Has sets of muscles thst control the size of the pupil and regulate the light reaching the retina
What does the lens do on an eye?
The lens focuses the light onto the retina ( which contains receptor cells sensitive to light intensity and colour
Very bright light can damage the retina. Explain the reflex to protect it… and dim light…
When light receptors in the eye detect very bright light, a reflex is triggered that makes the pupil smaller. The circular muscles in the iris contract the radial miscles relax. This reduces the amount ofnoight that can enter the eye.
The opposite process happens in dim light. The radial muscles contract and the circular muscles relax, which makes the pupil wider.
What is accomodation?
The eye focuses light on the retina by changing the shape of the lens
What can short-sightedness be casued by?
The lens being too thick
The eyeball being too long
What is long-sightedness caused by?
The lens being too thin
The eyeball being too short
What is short-sightedness?
People with short-sight can focus clearly on objects that are close to them, by automatic accomodation.
However, they cannot focus clearly on distant objects. The image forms in front of their retina even when the lens is as thin as possible.
What is long-sightedness?
People with long-sight can focus clearly on objects that are in distance by automatic accomodation.
However they cannot focus clearly on objects that are close to them. The image is focused behind their retina, even when the lens is as thick as possible
Ways to correct sight problems?
Wearing glasses. The extra lens in front of the eye helps to focus light onto retina.
Wearing contact lenses. These work in the same way as glasses, but are a lot smaller and sit directly on top of the eye. They are barely visisble
Eye surgery - the shape of the cornea can be changed with a laser to help the eye focus the light correctly onto the retina. This is usually carried out under local anaesthetic
Replacement LENS SURGERY: Sometimes long-sightedness may be more effactively treated by
Replacing the lens of the eye (rather than altering the shape of the corner with laser eye surgery).
In replacement lens surgery, the natural lens of the eye is removed and an artificial lens, made of clear plastic, is inserted in its place.
As it involves work inside the eye, replacing a lens carries higher risk than laser eye surgery, including possible damage to the retina (which could lead to loss of sight).
Homeostasis
Maintaining a constant internal environment
Homeostasis maintains optimal conditions for
enzyme action and all cell functions
Homeostasis is all about
regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
Your cells rely heavily on homeostasis. Why?
As they need the right conditions to function properly
In the human body, homeostasis include control of:
• blood glucose concentration
• body temperature
• water levels.
What are the three components that work together to maintain a steady condition
Receptors, coordination centres and effectors
Sensory organ
An area of the body which can detect a simulus
Automatic control systems in your body that regulate your internal environment include
Nervous and hormonal communication systems
Stimulus
A detectable change in an organisms environment
What is your nervous system
Means that humans can react to their surroundings and coordinate their behaviour.
The CNS consists of the ….. and is connected to the body by
Brain and spinal cord.
by sensory neurones and motor neurones
Sensory neurones
Carry information as electrical impulses from receptors to the CNS
Motor neurones
Neurones that carry electrical impulses from the CNS to effectors
Effectors
All your muscles and glands, which respond go nervous impulses.
Receptors
The cells that detect a stimulus
coordination centres (such as the brain, spinal cord and pancreas)
that receive and process information from receptors
The CNS Is a
Coordination centre
Bottom of page 66 for example on CNS
The connection between two neurones is
A synapse
(Synapse between two neurones) The nerve signal is transferred by
Chemicals which diffuse across the gap
Reflexes are
Rapid, automatic response to certain stimuli that don’t involve the conscious part of the brain
A reflex arc is
The passage of information in a relflex (from receptor to effector)
The two types of effectors and what they do
-Muscles contract in response
-Glands increase or decrease hormone secretion
Explain the process of a reflex arc
-Neurones go through spinal cord of through an unconscious part of the brain.
- when a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS.
- when the impulses reach a synapse between the sensory neurone and the relay neurone, it triggers chemicals to be released. These chemicals cause impulses to be sent along the relay neurone.
- when the impulses reach a synapse between the relay neurone and a motor neurone, the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone.
- the impukses then travek along motor neurone to effector.
- the muscle then contracts and move quicker than normal responses
Cerebal cortex
This is the puter wrinkly bit. It’s responsible for things like consciousness, intelligence, memory and language
Medulla
Controls unconscious activities like breathing and heartbeat
Cerebellum
Responsible for muscle coordination
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
What is the name of the chemical messenger that crosses the synapse
Neurotransmitter
What specialised cell is found in the nervous system
Nerve cells/nuerons
Examples of sensory organs-
Eyes- detect change in light intensity
Ears- detect sound waves
Nose- detects chemicals in air
Tongue- detects chemicals in food
Skin- detects pressure applied to body
What is fhe order of how information goes through from a stimulus go response
Simulus —- receptor —– coordinator —- effector —– response
Include info on CNS specific neurones
Simulus
Receptor
Sensory neurone
Relay neurone
Motor neurone
Effector
Response
Electrically stimulating the brain
The brain can be simulated 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 go get an idea of what those parts do.
MRI SCANS
a magnetic resonance imaging scanner is a big tube 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
Why is it difficult to investigate brain function and treating it
The brain is incredibly complex and delicate - the investigation of brain function and any treatment of brain damage or disease is difficult. It carries risk, physicsl damage and increased problems with brain function.
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.
Two common defects of the eyes are
myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina.
