B3.1 - The Eye, Brain, Nervous System, Reflex Arc Flashcards
What is the cornea
A transparent layer at the front of the eye
What is the iris
The coloured part of the eye. It opens and closes the pupil
What is the pupil
A hole that lets light into the eye
What does the lens do
Focuses the light onto the retina
What does the retina do
Changes light into electrical signals. It’s split into rods and cones
What does the optic nerve do
Sends the signals to the brain
What does the ciliary body and suspensory ligaments do
Control the shape of the lens
The ciliary body produces a liquid called
Aqueous humor
What does the cornea do
Works with the lens to focus the light
What is short sightedness
A defect where people cannot focus on objects far away. The image focuses in front of the retina
How is short sightedness corrected
By using glasses with diverging or concave lenses
What is long sightedness
A defect where people cannot focus on objects close up. The image is focused behind the retina
How is long sightedness corrected
By using glasses with converging or convex lenses
What can be used to treat short and long sightedness
Laser surgery
What is colour blindness and how is it caused
It is a deficiency in the way colour is seen. It’s more common in men and is caused by a genetic defect on the X chromosome
What is the most common form of colour blindness and can it be treated for inherited colour blindness
The most common form is red - green blindness
There is currently no treatment for inherited colour blindness to
What is red - green colour blindness
Someone who may confuse a purple and blue pencil because they cannot see the red element of the purple pencil
Rods are..
More sensitive in dim light but can’t sense colour
Cones are…
Sensitive to different colour but are not so good in dim light
The lens is elastic, which means..
The eye can focus light by changing the shape of the lens
What happens when you look at distant objects
The ciliary muscle relaxes, which allows the suspensory ligaments to pull tight. This pulls the lens into a less rounded shape so light is refracted less
What happened when you look at close objects
The ciliary muscle contracts, which slackens the suspensory ligaments. The lens becomes a more rounded shape so light is refracted more
What is the brain and what is it made up of
The brain is made up of billions of interconnected neurones. It controls and coordinates everything you do
What is the cerebrum and what does it do
It is the outer wrinkly bit that is composed of the two cerebral hemispheres that are divided into lobes. It’s responsible for things like consciousness, intelligence, memory and language.
What is the hypothalamus and what does it do
Involved in maintaining body temperature at the normal level. Also produces hormones that control the pituitary gland
What is the pituitary
A gland that produces many important hormones such as some of those involved in the menstrual cycle
What does the medulla do
Controls unconscious activities like breathing and your heart rate
What does the cerebellum do
Responsible for muscle coordination
What is the nervous system
a network of nerve cells (neurons) that transmit nerve impulses (messages) between parts of the body
What is the nervous system made up of
The nervous system is made up of neurones (nerve cells) which go to all parts of the body
What do sensory receptors do
Detect a change in your environment (a stimulus). Different sensory receptors detect different stimuli
What happens when a stimulus is detected by receptors
The information is sent as nervous (electrical) impulses along sensory neurones to the central nervous system (CNS)
What does the CNS do and what is it made if
The CNS consists of the brain and spinal cord. It coordinates the response and sends information to an effector (muscle or gland) along a motor neurone
What does the effector do and the CNS sends information to it
It responds accordingly
What is the process of the nervous system (words)
Stimulus ➡️ receptor ➡️ sensory
neurone ➡️ CNS ➡️ motor
neurone ➡️ effector ➡️ response
What do sensory neurones do
Carry impulses from receptors to the central nervous system
What do relay neurones do
Pass the impulse to a motor neurone
What do motor neurones do
Send the impulse to an effector which is a muscle of gland that produces a response
What is a synapse
The connection between two neurones
What are passed along the axon of a neurone
Electrical impulses are passed along the axon of a neurone
Neurones have branched endings (dendrites) which means…
So they can connect with lots of other neurones
Some axons are surrounded by a fatty (myelin) sheath which means
It acts as an electrical insulator, speeding up the electrical impulse
Neurones are long which means…
It speeds up the impulse
What slows the impulse down and is only long neurone quicker than lots of short ones joined together?
Connecting with another neurone slows the impulse down and one long neurone is much quicker
A synapse is…
The connection between two neurones
What does the electrical impulse do in a synapse
It triggers the release of transmitter chemicals which diffuse across the gap
What do the chemicals do that the electrical impulse releases
They bind to the receptor molecules in the membrane of the next neurone. This sets off a new electrical impulse
Why are reflex actions important?
They stop you from injuring yourself and they are automatic so are done without thinking
The sensory neurone connects to a relay neurone in the spinal cord or in the unconscious part of the brain which means
Also is the conscious brain involved in a reflex arc
There is not time wasted about the right response and it links directly to the right motor neurone
No!!
What happens in the first part of the reflex arc?
STIMULUS
Touch a pan, bee stings finger
What happens in the second part of the reflex arc
RECEPTOR
Stimulation of the pain receptor
What happens in the third part of the reflex arc
SENSORY NEURONE
Message travels along the sensory neurone
What happens in the fourth part of the reflex arc
RELAY NEURONE
Message is passed along a relay neurone
What happens in the fifth part of the reflex arc
MOTOR NEURONE
Message travels along a motor neurone
What happens in the sixth part of the reflex arc
EFFECTOR CELLS
Response by effector muscle is to move hand away
Why might scientists study the brain
It allows scientists to work out more about what each part of the brain does which is really useful when trying to treat people with brain damage or disease
What happens when scientists use case studies to learn about the brain
They carry out detailed studies of individuals who have abnormal brain function
Why might scientists use case studies
If 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
Why might scientists use fMRI scanners (big tube line machines)
They show which parts of the brain are activated when performing certain tasks inside the scanner
Also scientists can learn a lot by examining the brains of people who have died
If a person is severely brain damaged, why might it be tricky to investigate brain function
It may be unethical to study them as they might not be able to give informed consent
Why is it tricky to investigate brain function on dead people
Studying the brains of people who have died relies on people donating their brains for research
Why is it hard to repair damage to to the nervous system?
Neurones in the CNS don’t readily repair themselves and scientists haven’t developed a way to repair nervous tissue in the CNS
Why is it a problem if a problem occurs in a part of they nervous system that’s not easy to access
It can be hard to treat as it’s not easy to access e.g it’s not possible to surgically remove tumours growing in certain parts of the brain
Treatment for problems in the nervous system is bad because
It may lead to permanent damage e.g surgery to remove a brain tumour may lead surrounding parts of the brain permanently damaged
