B10 - The Human Nervous System Flashcards
What is the central nervous system?
The Central Nervous System (CNS) is the part of the nervous system where information is processed. It is made up of the brain and spinal cord
What is the cerebral cortex?
The region of the brain associated with consciousness, intelligence, memory, and language
What is the cerebellum?
The region of the brain concerned with coordinating muscular activity and balance
What are ciliary muscles?
Muscles that contract and relax to change the shape of the lens of the eye
What are coordination centres?
Areas that receive and process information from receptors. They send out signals and coordinate the response of the body
What are effectors?
Areas (usually muscles or glands) that bring about responses to the stimulus that has been received. These responses restore conditions in the body to the optimum level
What is homeostasis?
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes
What is the medulla?
The region of the brain concerned with unconscious activites such as controlling the heart, controlling of the gut, and breathing rate
What are motor neurones?
Motor neurones carry impulses from the central nervous system to the effector organs
What is a nerve?
A bundle of hundreds or even thousands of neurones
What are neurones?
Basic cells of the nervous system that carry minute electrical impulses around the body
What are receptors?
Cells that detect stimuli - changes in the internal or external environment
What is a reflex arc?
Brings about a reflex action. They involve the sense organ, sensory neurone, relay neurone, and motor neurone
What are reflexes?
Rapid automatic responses of the nervous system that do not involve conscious thought
What is a sensory neurone?
Neurone that carries impulses from the sensory organs to the central nervous system
What is stimuli?
Changes in the external or internal environment that can be detected by receptors
What are suspensory ligaments?
The ligaments that connect the lens of the eye to the ciliary muscles
What is the brain?
The brain processes information from sensory receptors all over your body and then sends out impulses along motor neurones that coordinate your responses to all the different situations you meet. The brain is made up of billions of interconnected neurones that form different regions. It controls complex behaviours
What are the different regions of the brain?
°Cerebral Cortex °Hypothalamus °Pituitary gland °Medulla °Cerebellum
What is the hypothalamus?
The area of the brain involved with monitoring and controlling body temperature
What is the pituitary gland?
He pituitary gland produces many different hormones which play a large part in controlling and coordinating body systems
How is the brain protected?
The brain is protected inside the bones of your skull, and is encased in protective membranes called the meninges
Why is it difficult to find out about the brain?
Because it is encased in the skull
How have scientists been able to find out about the brain?
°Studying people with brain damage
°Electrically stimulating brain areas
°MRI Scans
How has studying people with brain damage allowed scientists to find out about the brain?
It has been possible to discover the role of different areas of the brain when people suffer brain damage. Scientists matched changes in behaviour or memory with damaged areas of the brain to map the functions of some areas of the brain.
How has electrically stimulating brain areas allowed scientists to find out about the brain?
Scientists can remove the top of the skull to expose the brain and electrically stimulate areas to see what effect this has. As there are no sensory nerve endings in the brain, brain surgery can be done on conscious patients. People may experience hunger, anger, fear, or thirst simply due to the relevant part of the brain being stimulated
How have MRI scans allowed scientists to find out about the brain?
In recent years, scientists have developed a much better understanding of how the brain works as a result of new ways of taking images of the brain in living people. For example, if someone develops a brain tumour or has a stroke, this will effect their behaviour. A magnetic Resonance Imaging (MRI) scan will show exactly which areas of the brain have been effected. This enables scientists to link the loss of a certain function, such as speech or control of movement on a side of the body, with damage to a particular area of the brain. MRI scans can also take images of the brain as someone carries out a simple task such as reading or writing
Explain some problems with the brain
The brain is very complex and delicate. Many of the processes that take place involve many neurones in different areas. There is also a range of different chemicals released in the synapses in the brain. It is easily damaged and destroyed. As a result, it is very difficult to treat them. Drugs do not always reach the brain through the membrane which surrounds it. Surgery is difficult because it is not fully understood what each area of the brain actually does. It is easy to cause unintended damage.
Name some example conditions controlled by homeostasis:
°Internal body temperature (must be 37°C)
°Blood PH (must stay within 7.2 and 7.4)
°Osmotic balance
°Blood glucose concentration
What is the nervous system pathway?
Stimulis -> Receptor -> Processor -> Effector -> Response
What is the method for measuring reaction times?
1) Collect all necessary equipment and a partner to work with
2) Person A holds out their hand with a gap between their thumb and first finger
3) Person B holds the ruler vertically with the 0cm mark being at the top of person A’s thumb
4) Person B drops the ruler without warning
5) Person A must catch the ruler by closing their thumb and first finger
6) Record the number at the top of person A’s thumb in a suitable table
7) Repeat steps 2-6 4 more times and calculate a mean average
8) Calculate the reaction time of person A by using the equations “V^2 - U^2 = 2as” and “a = (v-u)/t”
9) Repeat steps 2-8 with different stimulants/distractions such as a caffeine drink or loud noises and record how this effects person A’s reaction time
What is an interneurone?
An interneurone (relay neurone) transfers an electrical impulse between the sensory neurone and motor neurone through the CNS
What is the iris?
The iris controls how much light enters the pupil. The iris is made of muscles that contract or relax to change the size of the pupil and so the amount of light reaching the retina. In a dim light the pupil is enlarged so as much light as possible enters the eye. In a bright light, the iris makes the pupil very small. This reduces the amount of light that goes into the eye, so that too much bright light does no damage the delicate, light-sensitive cells.
What is the cornea?
the clear area at the front of the sclera, as it is curved the cornea refracts light to help and try and focus it
What is the pupil?
the opening within the iris through which light passes before reaching the lens and being focused onto the retina
What is the lens?
The lens further refracts light to focus it onto the retina
What is the optic nerve?
The optic nerve carries impulses between the eye and the brain
What is the sclera?
The sclera is the white outer layer of the eye, it is tough and strong to prevent the eyeball being damaged
What is the retina?
The retina contains the light receptors
What is the blind spot?
Where the optic nerve leaves the retina so lacks receptor cells.
What is accomodation?
The process of changing the shape of your lens to focus on near or distant objects
How does your eye accommodate to focus on a distant object?
To focus on a distant object - the ciliary muscles relax 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 does your eye accommodate for near objects?
To focus on a near object - the ciliary muscles contract so the suspensory ligaments loosen. The lens is then thicker and more curved. It refracts light rays strongly so that they are focused onto the lens
What are metabolic reaction
Any reaction that happens with an organism
Explain how the nervous system works:
Once sensory neurones detect a stimulus, the information is sent as an electrical impulse that passes along neurones. The impulse travels along the sensory neurone until it reaches the central nervous system (which is made up of the brain and the spinal cord). Your brain then coordinates a response to the situation and sends impulses along motor neurones. The motor neurones carry the impulse to the effector. The effector may be a muscle or a gland that brings about change to the stimuli to restore optimum conditions.
How do muscles respond to an impulse from a motor neurone?
They contract
How do glands respond to an impulse from a motor neurone?
they secrete chemicals
Why are reflex actions important?
Reflexes help you to avoid danger or harm because they happen so quickly. They are automatic and rapid - they do not involve the conscious part of your brain.
How do reflexes work?
An electrical impulse passes from the receptor along the sensory neurone to the CNS. It then passes along a relay neurone (usually in the spinal cord) and straight back to a motor neurone. From there, the impulse arrives at the effector organ. The effector organ will be a muscle or a gland. We call this pathway a reflex arc. The key point to a reflex arc is that it bypasses the conscious areas of your brain. The result is that the time between the stimulus and the reflex action is as short as possible.
What is a synapse?
The synapse is the junction where 2 or more nerve cells meet
How do synapses work?
Your neurones are not joined up directly to each other. There are junctions between them called synapses which form physical gaps between the neurones. The electrical impulses travelling along your neurones have to cross these synapses. They cannot leap the gap. The diffusion of the chemical across the synapse is slower than the electrical impulse in the neurones, but it makes it possible for the impulse to cross the gap between them
Explain the reflex arc in detail:
- When you touch the object, a receptor in your skin is stimulated. An electrical impulse from a receptor passes along a sensory neurone to the CNS
- When an impulse from the sensory neurone arrives at the synapse with a relay neurone, a chemical is released. The chemical diffuses across the synapse to the relay neurone where it sets off a new electrical impulse that travels along the relay neurone
- When the impulse reaches the synapse between the relay neurone and a motor neurone returning to the arm, another chemical is released. Again, the chemical diffuses across the synapse and starts a new electrical impulse travelling down the motor neuron to the effector
- When the impulse reaches the effector organ, it is stimulated to respond.
Explain how a reflex pathway differs from a normal conscious action:
In a reflex action, the coordinator is the relay neuron either in the spinal cord or in the unconscious area of the brain. An impulse also travels up the spinal cord to the conscious part of the brain so that you know that it has happened, however this is only after it has happened.
What is the flowchart of a reflex pathway?
Stimuli -> Receptor -> Sensory Neurone -> Relay Neurone -> Motor Neurone -> Effector -> Response
What is a reflex arc?
The sequence from the receptor to the effector in a reflex action
Explain how an eye focuses light
The light that enters the eyes has to be focused onto the light-sensitive cells of the retina so that you can see clearly. If the light is focused in front or behind the retina the image will be blurred. The cornea always refracts the light the same amount. However, the shape of the lens can be changed by the contraction or relaxation of the ciliary muscles. This changes the amount the lens refracts the light. The image is formed upside down on the retina but our brains interpret the images as the right way up
What is short sightedness called?
Myopia
What is long sightedness called?
hyperopia
What is myopia?
short sightedness. If you have myopia you can see close objects in clear focus but distant objects look blurred. The light is focused in front of the retina, so the images that land on the retina are out of focus and blurry. This may be a result of a lens that is too curved or a particularly long eyeball
How do you treat myopia?
The most common way of treating myopia is to wear spectacles with a concave lens that spread out the light from distant objects before it reaches the eye. This means the thicker lens can bring it into perfect focus on the retina
What is hyperopia?
Long sightedness. With hyperopia you can focus clearly on distant objects but close objects appear blurred. This may be the result of a lens that is too flat and thin, or of a particularly short eyeball. As a result the lens cannot refract the rays of light strongly enough. The light is focused behind the retina, so the image that lands on the retina is out of focus.
How do you treat hyperopia?
The most widely used method of correcting this is spectacles with a convex lens. They bring the light rays together more before they reach the eye itself. Now the thinner lens can bring the rays of light into perfect focus on the retina
What are 3 new technologies that can be used to treat hyperopia and myopia?
- Contact lenses
- Laser Eye surgery
- Replacement lenses
Explain how contact lenses can be used to treat hyperopia and myopia:
Contact lenses are lenses that are placed on the surface of the eye. They do the same job as conventional spectacles, but they cannot be seen and can make life much easier for playing sport and general activities. Hard contact lenses are made of relatively rigid material and last a long time. They have to be removed overnight and kept sterile to prevent eye infections. Most modern contact lenses are soft lenses. These are made of more flexible materials that are more comfortable to wear but they do not last as long. Some soft contact lenses can be worn for a month - and like hard contact lenses have to be kept in sterile solution overnight . Others are disposable - worn for a day then thrown away.
Explain how laser eye surgery can be used to treat hyperopia and myopia:
Laser eye surgery is only available to adults once their eyes have stopped growing and their vision has become stable. lasers are used to treat myopia by reducing the thickness of the cornea so it refracts the light less strongly. This means that the lens now focuses distant light on the retina instead of in front of it. TO treat hyperopia, lasers are used to change the curve of the cornea so it refracts light from close objects more effectively
Explain how replacement lenses can be used to treat hyperopia and myopia:
One of the most recent treatments is to add another lens inside the eye itself to correct the visual defect permanently. There are 2 main techniques. In one a permanent contact lens is implanted into the eye and the natural lens is left in place. In the other, the faulty lens is replaced by an artificial lens. The risks of lens replacement are damage to the retina, cataracts developing is the natural lens remains in place, and infections.
What is a functional MRI scanner?
a functional MRI scanner allows a person to move whilst the scanner makes images of the persons brain activity
Suggest how a functional MRI scanner could help to find out more about the brain damage a person has:
A functional MRI scanner allows the person to complete tasks such as reading or writing whilst their brain is being scanned. This could help to find out more about brain damage someone has received as their brain scan can be used to see which areas of the brain are active / inactive whilst completing these tasks. The doctor could then compare the brain scan with someone who has not experienced brain damage to see if certain areas are not being actively used (when they should be being used). This allows the doctor to see exactly where the damage is. A traditional MRI scanner cannot be used if the person can’t stay still (i.e. a young child or those with Parkinson’s disease)
