Flashcards in Cells and Control Deck (50):
What is mitosis?
-Mitosis is the stage of the cell cycle when the cell divides
-Mitosis is a type of cell division.
-Mitosis occurs wherever more cells are needed.
-It produces two new diploid cells that are identical to each other, and to the parent cell.
Importance of mitosis
-Repair damaged cells
Cell prepares for mitosis by increasing amount of sub cellular structures and duplicating its dna
-Spindle fibres form and the nuclear membrane starts to break down
Chromosomes line up at the middle of the cell , attached to spindle fibres
The chromatids are pulled apart by cell fibres and move to opposite ends of the cell
Nuclear membrane form around each set of chromosomes; these have become the nuclei of the 2 new cells
Cytoplasm and cell membrane divide to form 2 separate cells
What is cancer
Cancer is a result of uncontrolled mitosis; cancerous cells divide repeatedly and a tumor develops which is an irregular mass of cells
-Used in growth by both animals and plants
-The process by which cells become specialised to complete different tasks.
-There is one type of cell that can be used to make any cell.
-Used in growth by both animals and plants
-cells need to divide in order to grow and repair themselves
-This is where a plant expands, making it bigger and so making it grow.
-ONLY in plants
Growth in animals
All growth in animals happens by division. They tend to grow whilst young, reach full growth and then stop, from then on most cell division is for repair.
Growth in plants
In plants, growth in height is mainly due to elongation. Cell division happens at the tips of roots and shoots. Plants grow continuously. Therefore plants continue to differentiate.
Importance of differentiation
Differentiation allows specialised cells to distinguish between each other, to perform specific functions and in turn, creates variation among and between species.
-They are used to define an overall pattern in development and to highlight potential problems
'Percentile'- eg. a baby is in the 75th percentile of average mass this means that 75% of babies are lighter and 25% are heavier
-investigations may occur if results are above/below the top/bottom percentile line, or if it -increases/decreases over more than 2 percentiles, or if there is a general inconsistent pattern.
Stem cells are undifferentiated cells.
Embryonic stem cells
-Found in an early embryo
-Can differentiate into every type of cell in your body
-Important for growth
Adult stem cells
-Found in the body eg. bone marrow
-They aren't as versatile as embryonic cells as they can only produce several types of specialised cell
-Used to replace damaged cells
Benefits of stem cells in medicine
-Scientists would be able to test millions of potential drugs without the use of humans or animals
-Provides great potential for discovering treatment/cures for a variety of diseases
-Benefits the study of development that can not be directly studied in a human embryo, therefore allowing prevention and treatment of abnormal human dvelopment
Risks of stem cells in medicine
-Rejection - if transplanted cells aren't grown using the patient's own stem cells, the patients body may recognise the cells as foreign and trigger an immune response. Although drugs can be taken to supress this response, it makes the patient suspectable to disease and illness
-Tumour development - stem cells divide quickly, if the scientists are unable to control the rate of division, a tumour may develop
-Disease transmission - viruses are inside cells, if they go undetected and stem cells are then transplanted, the virus may be passed on, making the recipient even sicker.
-only cell in plants that divide by mitosis.
-found in the parts of a plant that are growing (eg. tip of roots and shoots).
-produce unspecialized cells that are able to divide and form any cell type.
-can divide and differentiate for as long as the plant lives.
-unspecialised cells --------> specialised tissues
-is a long column of neurons that run from the base of the brain down the spine.
-In several places, they branch off and connect with other parts of the body.
-It relays information between the brain and the rest of the body.
- The largest part of the brain which is divided into two halves called the cerebral hemispheres (left side controls right muscles etc...).
-Responsible for different things including movement, intelligence, memory, language and vision
- Responsible for muscle coordination and balance
- controls unconscious activities such as heart rate and breathing.
-Uses x-rays to produce an image
-shows the main structures but not the functions
-if the scans shows a diseased or damaged brain structure and the patient has lost some function, the function of that part of the brain can be worked out.
-Uses radioactive chemicals to show which parts of the brain are active
-They are very detailed and can be used to investigate both structure and function of the brain in real time
-It can show if the areas of the brain are unusually active or inactive, so they are useful for studying disorders that change the brain's activity (eg. alzheimer's)
Difficulties with treating damage and disease in the CNS
-It's hard to repair damage - neurons in the CNS don't readily repair themselves and scientists have not found way to repair nervous tissue in the CNS
-If a problem occurs in a part of the nervous system that isn't easy to access it can be hard to treat.
-Treatment may lead to permanent damage
Function of Dendrons + dendrites
- carry nerve impulses towards the cell body
Function of axons
carry impulses away from the cell body
Function of myelin sheath
some axons are surrounded by a myelin sheath, it acts as an electrical insulator, speeding up the electrical impulse
Structure of sensory neuron
-one long dendron carries nerve impulses from receptor cells to the cell body, which is located in the middle of the neurone
-one short axon carries nerve impulses from the cell body to the CNS
Structure of motor neurone
-Many short dendrites carry nerve impulses from the CNS to the cell body
-One long axon carries nerve impulses from the cell body to the effector cells
The longer the neurone
the quicker the impulse
-It is the connection between two neurones.
-The nerve signal is transferred by chemicals called neurotransmitters, which diffuse across the gap
-The neurotransmitters then set off a new electrical signal in the next neurone.
-Transmission is very fast but it is slowed down at the synapse because the diffusion of neurotransmitters takes time.
Impulses are sent from receptors in his hand along a sensory neurone to the CNS. The impulse is transferred via a synapse to a relay neurone, via the release of neurotransmitters. It is then transferred across another synapse to motor neurone and travels along the motor neurone to the effector in his arm. (the muscle in his arm)
Refracts light into the eye
controls how much light enters the pupil
are more sensitive in dim light, but can't sense colour
are sensitive to different colours but are not so good in dim light
when cones do not work properly in the retina
due to a cloudy patch on the lens, light is not able to enter the eye normally. People with a cataract commonly have blurred vision, struggle to see in bright light and colours look less vivid.
when people are unable to focus on near objects, because the lens is the wrong shape and either doesn't refract light enough or the eyeball is too short. Light from near objects is brought into focus behind the retina
when people are unable to focus on distant objects, because the lens is the wrong shape and either refracts light too much or the eyeball is too long. Light from distant objects is brought into focus before the retina.
Treatment for catarcts
cured by replacing the faulty lens with an artificial one.
Treatment for long sightedness
cured by wearing glasses or contacts with a convex lens
Treatment for short sightedness
cured by wearing glasses or contacts with a concave lens
How eye focuses on distant objects
-Light from distant objects needs to be focused only a relatively small amount
-Ciliary muscles relaxes and the suspensory ligaments are pulled tight: the lens is now pulled thin
-Because the lens is in, the light rays are only slightly refracted
-The light rays are now focused onto a point on the retina