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What is mitosis?
The production of two daughter cells, each with identical sets of chromosomes in the nuclei to the parent cell. It results in the formation of two genetically identical diploid cells. It is used for growth, producing new cells, repairing old cells, and asexual reproduction
What are the stages of the cell cycle?
Interphase, prophase, metaphase, anaphase, telophase, cytokinesis
What happens in interphase?
DNA in the chromosome copies itself ready for mitosis
What happens in prophase?
DNA in chromosomes and its copies condenses to become more visible. The membrane around the nucleus disappears.
What happens in metaphase?
Chromosomes and their copies line up in the middle of the cell
What happens in anaphase?
Chromosomes and their copies are pulled to different ends of the cell
What happens in telophase?
New membranes form around the chromosomes at each end of the cell
What happens in cytokinesis?
The cell membrane pinches in and eventually divides into two daughter cells
What is cancer?
Uncontrolled cell division that can lead to the formation of tumours
What is cell differentiation?
Cells divide by mitosis to produce a multicellular organism. Cells differentiate so cells can develop features that enable them to carry out specific roles.
What is cell elongation?
Plants become longer as they grow by mitosis. It happens in their meristems, where new cells are formed.
What is the importance of specialised cells?
Without them, complex multicellular organisms would not exist
What is the function of embryonic stem cells?
They can differentiate into a wider range of cells - all cells
What is the function of adult stem cells?
They differentiate into a narrower range of cells
What is the function of meristems?
They produce all types of plant cells at any point of time during the life of the plant
Benefits of stem cells in medicine
Can treat patients with currently untreatable conditions, can be used for growing organs for transplants, can be used in medical research
Risks of stem cells in medicine
Difficulty in finding a suitable cell donor, difficult to obtain and store, cultured stem cells could be contaminated with viruses which would be transferred to the patient, no guarantee in how successful these therapies could be, mutations in cells could lead to cancer
What are the main areas of the brain?
Cerebral hemispheres, cerebellum, medulla oblongata, hypothalamus
What is the role of the cerebral hemispheres?
Two hemispheres making up the cerebral cortex, controls most senses, intelligence, personality, conscious thought and high level functions.
What is the role of the cerebellum?
Controls balance, coordination and movements, controls muscular activity
What is the role of the medulla oblongata?
Controls unconscious activities
What is the role of the hypothalamus?
Regulates temperature and water balancr
How is CT scanning used to investigate the brain?
A set of x-rays are taken of the brain from different angles, and processed by a computer to allow doctors to see inside the brain
How is PET scanning used to investigate the brain?
It detects gamma rays that radiate from tracer, used to detect high levels of metabolic reactions or to detect cancers
Limitations to treating brain damage and disease
Brain surgery is risky, due to the brain being complex and delicate. Surgery can create more damage or side effects too.
What are the main types of neurone?
Sensory, motor, relay
What is a receptor?
Cells that detect stimuli
Features of neurons
Axon: long fibre, insulated by the myelin sheath so that impulses travel faster, carry messages around the body
Dendrons: tiny branches which split to become dendrites, they receive incoming impulses from other neurons
How are electrical impulses transmitted between neurons?
At the synapse, electrical signals are converted into chemical ones, then converted again at the other end of the synapse at the next neuron. The electrical impulse travels along the axon of the presynaptic neuron, which triggers the axon terminal to release neurotransmitters. These chemical messengers diffuse across the synapse and bind to the receptor molecules of the second neuron. Receptor molecules on the postsynaptic neuron only bind to specific neurotransmitters, stimulating the postsynaptic neuron to transmit the electrical impulse.
Transport between receptors and effectors
Receptors detect change in the environment and send an electoral signal along the sensory neuron. These move towards the central nervous system, which coordinates its response through relay neurons. Messages are sent to effectors via motor neurons, which decide which muscles to contract or relax and which glands to secrete hormones - the effectors.
What is the reflex arc?
The sequence through the nervous system that all reflex actions follow
What are the steps of the reflex arc?
Receptor in skin detects stimulus, sensory neurons send electrical impulses to relay neurons in the spinal cord or brain, relay neurons connect sensory neurons to motor neurons, then the effector produces a response
What is the role of the cornea?
Refracts light entering the eye
What is the role of the lens?
Refracts light to focus on the retina
What is the role of the iris?
Controls how much light enters the pupil
What is the role of the rods?
Detect light
What is the role of the cones?
Detect colour
What is shortsightedness?
When you can see near objects clearly but cannot focus on distant objects. This can be because they eyeball is elongated causing a larger distance between the lens and the retina, but also because the lens is too thick or curved so that light is focused in front of the retina.
Treatment of shortsightedness
Placing a concave lens in front of the eye, using laser surgery, getting a replacement plastic lens to correct defects
What is longsightedness?
When you can see distant objects clearly but cannot focus on near objects. This can be because the eyeball is too short causing a smaller distance between the lens and the retina, or it could be because of a loss in elasticity in the lens, so that it cannot become thick enough to focus.
Treatment of longsightedness
Putting a convex lens in front of the eye, using laser surgery, using a plastic replacement lens to correct defects in the eye
What is a cataract?
Cloudiness in the lens caused by protein build up
Treatment for cataracts
Removing the lens and replacing it with a plastic one
