Coordination And Control - The Nervous System Flashcards
bbc bitesize
Accomidation
def
The process of changing the shape of the lens of the eye to focus on near or distant objects
Axon
def
The long part of a nerve cell along which the electrical signal quickly moves
Cancer
def
A disease caused by normal cells changing so that they grow and divide in an uncontrolled way. The uncontrolled growth causes a lump called a tumour to form
Cell membrane
def
A selectively permeable membrane surrounding the cell and controlling the entry and exit of materials
Cerebellum
def
The part of the brain that controls balance and co-ordination
Convex lens
def
A lens that is thicker in the centre than at the edges, and which converges light
Diffuse
def
When particles spread out from a region of higher concentration to a region of lower concentration
Effector
def
The organ, tissue or cell that produces a response
Medulla
def
The part of the brain controlling breathing, heart rate and peristalsis
MRI
Magnetic Resonance Imaging - A computer that can scan the human body using magnetic fields and radio waves, used in medicine
Neurone
Nerve cells are called neurones. They are adapted to carry electrical impulses from one place to another. A bundle of neurones is called a nerve.
Neurotransmitter
de
Chemical involved in passing nerve impulses from one nerve cell to the next across a synapse
Optimum
def
The best or most appropriate - for instance, the conditions under which an enzyme works best (eg temperature and pH)
Receptors
Organs which recognise and respond to stimuli
Receptors are groups of specialised cells. They detect a change in the environment and stimulate electrical impulses in response. Sense organs contain groups of receptors that respond to specific stimuli.
Stimulus
def
Something that sets off a reaction in the nervous system, for example, light, heat, sound, gravity, smell, taste, or temperature. These changes in the environment are detected by receptors in an organism. The plural is stimuli
Synapse
def
A tiny gap at the junction between two nerve cells, which nerve signals must cross
the nervous system.
The conditions inside our body must be carefully controlled if the body is to function effectively. The conditions are controlled in two ways with chemical and nervous responses.
All control systems include:
- cells called receptors, which detect stimuli
- the coordination centre, such as the brain, spinal cord or pancreas, which receives and processes information from receptors around the body
- effectors bring about responses, which restore optimum levels, such as core body temperature and blood glucose levels
- effectors include muscles and glands, and so responses can include muscle contractions or hormone release
What are the three main type of neurone?
sensory
motor
relay
Features that all 3 main types of nuerones have in common.
- A long fibre (axon) which is insulated by a fatty (myelin) sheath. They are long so they can carry messages up and down the body.
- Tiny branches (dendrons) which branch further as dendrites at each end. These receive incoming impulses from other neurones.
Where two neurones meet there is a small gap called a synapse. Here the electrical signal must be converted into a chemical one, which is converted back to an electrical one on the other side of the synapse where the next neurone starts.
1) an electrical impulse travels along the first axon
2) this triggers the nerve-ending of a neurone to release chemical messengers called neurotransmitters
3) these chemicals diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the second neurone
4) the receptor molecules on the second neurone bind only to the specific neurotransmitters released from the first neurone
5) this stimulates the second neurone to transmit the electrical impulse.
Receptors to effectors
Receptor cells detect a change in the environment (a stimulus) and start electrical signals along neurons. These move towards the central nervous system (CNS). The CNS is the brain and spinal cord. It coordinates the responses. Messages are then sent back along different neurones to muscles which contract or relax, and glands which secrete hormones. Muscles and glands are called effectors.
Stimulus → receptor → coordinator → effector → response
Name the stimulus for each of these sense organs: Skin Tongue Nose Eye Ear
Skin - Touch, temperature
Tongue - Chemicals (in food and drink, for example)
Nose - Chemicals (in the air, for example)
Eye - light
Ear - sound
Effectors include muscles and glands. They produce a specific response to a detected stimulus. For example:
- a muscle contracting to move an arm
- muscle squeezing saliva from the salivary gland
- a gland releasing a hormone into the blood.
features of a motor neurone
- Dendrite
- Cytoplasm
- Nucleus
- Cell membrane
- Axon
- Nerve ending
reflex action
part of reflex arc
There are different types of neurones that work together in a reflex action. This is an automatic and rapid response to a stimulus, which minimises any damage to the body from potentially harmful conditions, such as touching something sharp or hot.
The pathway of a reflex action only travels through relay neurones in the spinal cord and not the brain in order to increase the speed of the reaction.
reflex arc
All reflex actions follow an overall sequence through the nervous system which is called the reflex arc. Crucially this does not involve the conscious part of the brain, which makes it much quicker. This in turn reduces damage to the body.
stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response
The steps in the reflex arc in more detail.
1) A receptor in the skin detects a stimulus (the change in temperature).
2) Sensory neurones send electrical impulses to relay neurones, which are located in the spinal cord. They connect sensory neurones to motor neurones.
3) Motor neurones send electrical impulses to an effector.
4) The effector produces a response (muscle contracts to move hand away).
The brain
The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.
Name the 4 main areas of the brain
- Cerebral hemispheres
- Cerebellum
- Medulla oblongata
- Hypothalamus
Name the function of the cerebral hemispheres.
one of the main areas of the brain
The cerebrum’s outer layer, it is split into two hemispheres and is highly folded. These two hemispheres make up the cerebral cortex. This controls most of our senses, intelligence, personality, conscious thought and high-level functions, such as language and verbal memory.
Name the function of the cerebellum
one of the main areas of the brain
Controls balance, co-ordination of movement and muscular activity.
Name the function of the medulla oblongata
one of the main areas of the brain
Controls unconscious activities such as heart rate and breathing rate.
Name the function of the Hypothalamus
one of the main areas of the brain
Regulates temperature and water balance within the body.
The nervous system
The nervous system enables humans to react to their surroundings and to coordinate their behaviour. It comprises millions of neurones, and it uses electrical impulses to communicate very quickly.
How did neuroscientists map regions of the brain?
Modern science has allowed scientists to discover how different parts of the brain function. Neuroscientists have been able to map various regions of the brain to particular functions by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques.
Electrical stimulation of the brain.
Scientists have stimulated different parts of the brain with a weak electrical current and asked patients to describe what they experienced. If the motor area is stimulated, the patient makes an involuntary movement. If the visual area is stimulated, they may see a flash of colour. EEGs (Electroencephalograms) can be created and studied, to observe the electrical activity in the brain.
What are the three modern techniques used to scan brains?
- MRI (magnetic resonance imaging)
- CT (computed tomography)
- PET (positron emission tomography)
What does an MRI scanner do?
MRI scanners use strong magnetic fields and radio waves to show details of brain structure and function. Patients are asked to perform various tasks and, by looking at the scan, scientists can see which parts of the brain are active when the task is carried out. The patient lies on a bed which moves into the machine. Some people can feel claustrophobic inside an MRI scanner.
What does a CT scanner do?
CT scanners are similar to MRIs. The patient lies on a bed which passes through a ring of equipment (not into the machine like in MRI). The ring takes a series of x-rays from different angles. These are processed by a computer to allow the doctors to see inside brains and other parts of the body.
What does a PET scanner?
PET scanners detect gamma rays that radiate from a chemical compound called a tracer. PET scans are used to detect high levels of metabolic reactions inside a person. Before going into the scanner the patient consumes the tracer. This travels to any area of the body which has unusually high levels of metabolic reactions. This is often a tumour and so PET scans are used to detect cancers.
What is brain damage?
Brain damage is any loss of cells in the brain.
What causes brain damage?
Causes include impact to the skull, strokes, consumption of excessive alcohol and brain tumours.
Brain damage is any loss of cells in the brain. This is often because of injuries such as car crashes when a person’s head hits an object with a great force. The extent of the injury depends upon many factors including:
- the force of impact
- the size or shape of the object hitting the skull
- the position the object hits the skull
- the time it takes for treatment
Effect of brain injury/brain damage
Many brain injuries are fatal. Longer-term symptoms of brain damage include speech or movement problems, reduced coordination, memory loss and personality changes.
Brain damage as a result of impact to the skull.
Often impacts to the skull result in the brain swelling as it produces excessive fluid. Brain surgery may be needed to remove a tumour or excess fluid, such as blood. All surgery carries a level of risk, but due to the complexity and delicacy of the brain, investigating and treating brain disorders can be very difficult. If surgery is undergone more damage or side-effects may be created, which could affect the patients’ quality of life. Serious considerations about the risks involved against the benefits need to be undertaken first. Physiotherapists play a very important role helping with the rehabilitation of patients with brain damage.
The eye is what kind of organ, containing what?
The eye is a sense organ containing receptors sensitive to light intensity and colour.
List parts of the structure of the human eye.
- Cornea
- Iris
- Retina
- optic nerve
- Sclera
- lens
- Suspensory ligament
- Pupil
- ciliary muscle
- Fovea
Structure of the human eye.
Describe the function of the Cornea.
Refracts light - bends it as it enters the eye
Structure of the human eye.
Describe the function of the Iris.
Controls how much light enters the pupil
Structure of the human eye.
Describe the function of the lens
Further refracts light to focus it onto the retina
Structure of the human eye.
Describe the function of the retina (basic)
Contains the light receptors
Structure of the human eye.
Describe the function of the Optic nerve.
Carries impulses between the eye and the brain
Structure of the human eye.
Describe the function of the Sclera.
Tough white outer layer of the eye - it helps protect the eye from injury
The retina (detailed)
Light passes through the eyeball to the retina. There are two main types of light receptors called rods and cones. Rods are more sensitive to light than cones so they are useful for seeing in dim light. There are three different types of cone cells which produce colour vision.
The pupil reflex (dim light)
- Radial muscles of iris contracted
- Circular muscles of iris relaxed
- Dilated pupil (more light enters eye)
The pupil reflex (bright light)
- Radial muscles of iris relaxed
- Circular muscles of iris contracted
- Contracted pupil (less light enters eye)
How the eye works.
Accommodation to focus on a near object.
he lens becomes thicker which allows the light rays to refract (bend) more strongly.
How the eye works.
Accommodation to focus on a distant object.
the lens is pulled thin which allows the light rays to refract slightly.
How the eye works.
What happen if the position of the object is near?
(in terms of structure)
Ciliary muscles - contract Suspensory ligaments - slacken/loosen Muscle tension on lens - low Lens shape - fat/thicker Refraction of light rays - Light is refracted strongly
How the eye works.
What happens if the position of the object is distant?
(in terms of structure)
The ciliary muscles relax - relax Suspensory ligaments - stretched/tighten Muscle tension on lens - high Lens shape - thin Refraction of light rays - Light is only refracted slightly
Correcting vision defects
Two common defects of the eyes are myopia (short-sightedness) and hyperopia (long-sightedness). In both cases, rays of light do not focus on the retina so a clear image is not formed.
These two defects are treated with spectacle lenses, which refract (bend) the light rays so that they do focus on the retina.
myopia
short sighted-ness
Short sight
Someone who is short-sighted can see near objects clearly, but cannot focus properly on distant objects.
Short sight is caused by one of the following:
- the eyeball being elongated - so that the distance between the lens and the retina is too great.
- the lens being too thick and curved - so that light is focused in front of the retina.
Short-sightedness can be corrected by placing a concave lens in front of the eye.
Hyperopia
Long sighted-ness
Long sight
Someone who is long-sighted can see distant objects clearly, but they cannot focus properly on near objects.
Long-sightedness is caused by one of the following:
- the eyeball being too short - so the distance between the lens and retina is too small
- a loss of elasticity in the lens - meaning it cannot become thick enough to focus (which is often age-related)
As a result, the lens focuses light behind the retina instead of onto it. Long-sightedness is corrected by putting a convex lens in front of the eye.
Alternatives to wearing spectacle lenses.
New technologies have provided alternatives to wearing spectacle lenses: hard and soft contact lenses, laser surgery to change the shape of the cornea and a replacement lens in the eye. Contact lenses work by being in ‘contact’ with your eye. They float on the surface of the cornea. They work like spectacle lenses, by focusing and refracting the light.
Also:
- Laser surgery - reshapes the cornea surgically. Common for myopia but can be used for some hyperopia conditions.
- Replacement lens - implanting artificial lenses is a recent development, and can be placed in front of the original lens, through a small cut in the cornea, to correct an eye defects.
What is a cataract and how can it be treated?
A cataract is a cloudiness in the lens, caused by a build up of protein inside the lens.
Cataracts can be treated by removing the lens and replacing with a plastic lens.
What type of cells start electrical impulses along nerves?
Receptor
What part of a nerve cell insulates the electrical signal?
Myelin sheath
What neurones carry signals to effectors?
Motor neurones
Where do electrical signals go in a reflex arc?
Spinal cord
What affect do stimulants like caffeine have on your reaction times?
Stimulants like caffeine decrease your reaction times. (Decreasing reaction times means faster reactions. Increasing reaction times means slower reactions.)
What part of the brain controls balance and coordination of movement?
Cerebellum.
