Topic 2 - cells and control Flashcards
What happens during interphase?
Before mitosis, cell grows and increases subcelullar structures. It duplicates its DNA and DNA is copied and forms X-shaped chromosomes
What happens during prophase?
chromosomes condense, getting shorter and fatter. the membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm
What happens during metaphase?
The chromosomes line up at the centre of the cell
What happens during anaphase?
Cell fibres pull the chromosomes apart. The two arms of each chromosome go to opposite ends of the cell
What happens during telophase?
Membranes form around each of the sets of chromosomes. Those become the nuclei of the 2 new cells - The nucleus has divided
What happens during cytokinesis?
Before telophase ends, the cytoplasm and cell membrane divide to form 2 separate cells
How is mitosis useful in growth and repair?
Multicellular organisms use mitosis to grow or to replace damaged cells
How is mitosis useful in asexual reproduction?
Some organisms use mitosis to reproduce e.g. strawberries
What is produced at the end of mitosis?
The cell has produced 2 new daughter cells. each daughter cell contain the same set of chromosomes in its nucleus as the other daughter cell. They’re genetically identical diploid cells. They’re also genetically identical to the parent cell
What causes cancer?
- The rate at which cells divide is controlled by an organisms genes
- if theres a change in a gene that controls cell division, the cell may start dividing uncontrollably
- This can lead to a mass of abnormal cells (tumour)
- If the tumour invades and destroys surrounding tissue, it is cancer
Describe cell division in animals
when animals are young, cells divide at a fast rate as they need to grow. When they reach adulthood, cells mostly divide to replace damaged cells. Cell differentiation is lost at an early stage
What is cell differentiation?
the process in which a cell changes to become specialised for its job. This allows multicellular organisms to work more efficiently
Describe cell elongation, cell division and cell differentiation in plants
- growth in height in plants is due to cell elongation
- cell division only happens in the roots and shoots
- plants grow continuously, so they will always differentiate to develop new parts
What is the function of embryonic stem cells?
These are cells found in early human embryos and they can divide and produce and kind of cell at all. This means they are important for the growth and development of organisms
What is the function of adult cells in animals?
These are found in bone marrow and aren’t as versatile as embryonic stem cells. They can be used to repair damaged cells.
What is the function of meristems?
Meristems are like embryonic stem cells but the cells in meristems can differentiate for as long as the plant lives.
What are the benefits of using stem cells in medicine?
- They may cure diseases e.g. sickle cell anaemia
- they can differentiate into any cell under certain conditions
- It can be used to replace cells that had been damaged due to injury
What are the risks of using stem cells in medicine?
- Tumour development - stem cells divide rapidly, this can cause a tumour if not controlled
- Disease transmission - is stem cells are infected with a virus., it could infect a patient and make them sicker
- Rejection - If foreign stem cells were used, the body may not recognise it and trigger an immune response. Drugs could be taken but this would make them more susceptible to diseases
- Ethical issues - each cell could be a potential human life (others say it is better to cure those suffering first)
What does the cerebrum do?
- the right hemisphere controls muscles on the left and vice versa
- Different parts of the cerebrum are responsible for different things i.e. movement, intelligence, language, memory and vision
What does the cerebellum do?
It is responsible for muscle coordination and balance
What does the medulla oblongata do?
It controls unconscious activities like breathing and your heart rate
What is CT scanning?
A CT scanner uses X rays to produce an image of the brain and it only shows the main structures of the brain but if a patient shows a diseases or damaged brain structure and lost some function, the function of the brain can be worked out
What is PET scanning?
These use radioactive chemicals to show which parts of the brain are active. They show both structure and functions of the brain. they can be used to study disorders e.g. alzheimers
What are the risks of treating damages in the brain and CNS?
- its hard to repair damage to the nervous system as neurones in the CNS dont readily prepare themselves
- Some parts of the CNS are hard to access (parts of the brain)
- Treatments may lead to permanent damage (paralysis)
How does the CNS coordinate a response?
1 - Stimulus 2- Receptors 3. sensory neurones (synapse) 4. CNS (relay neurones) (synapse) 5. Motor neurones 6. Effector 7. Response
What is the role of the myelin sheath?
The myelin sheath acts as an electrical insulator. This allows for the impulses to travel faster
What do all neurones have?
They all have a nucleus and a cell body
Describe the function and structure of a sensory neurone?
- 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
Describe the function and structure of a 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 effector cells
Describe the function and structure of a relay neurone ?
- Many short dendrites carry nerve impulses from sensory neurones to the cell body
- an axon carries nerve impulses from the cell body to motor neurones
What is a synapse?
a synapse is the connection between 2 neurones
What are neurotransmitters?
These are chemicals that transfer nerve signals across a synapse. They diffuse across the gap. electrical impulses are slowed down as the diffusion of neurotransmitters takes time
What is the role of the cornea?
The cornea refracts light into the eye
What is the role of the iris?
The iris controls how much light enters the pupil
What is the role of the lens?
The lens also refracts light, focussing it on the retina
What is the retina?
The light sensitive part which contain receptor cells called rods and cones
Describe rods
rods are more sensitive in dim light but cant see colour
Describe cones
Cones are sensitive to different colours but are not good in dim light
What is the information from light converted into?
The impulses from light are converted to electrical impulses and the optic nerve carries these impulses from the receptors to the brain
How does long-sightedness happen?
This happens when the lens is in the wrong shape and doesnt bend the light enough or the eyeball is too short
- Light from near objects is brought into focus behind the retina
- You can use a convex lens to correct them
How does short-sightedness happen?
This happens when the lens is in the wrong shape or the eyeball is too long
- light from far objects is brought into focus in front of the retina
- you can use concave lenses to correct it
What causes colour blindness?
It’s caused when e.g. red or green cones in the retina aren’t working properly. There’s no cure as the cone cells cannot be replaced
What are cataracts?
Cataracts are cloudy patches on the eye which dont let light enter the eye properly. It can cause blurred vision and make colours look less vivid and having difficulty seeing bright light. It can be treated by replacing a faulty lens
How does changing the shape of the lens allow us to look at distant objects?
1) the ciliary muscle relaxes, which allows the suspensory ligaments to pull tight
2) This pulls the lens into a less rounded shape
How does changing the shape of the lens allow us to look at close objects?
1) The ciliary muscle contracts, which allows the suspensory ligaments to relax
2) The lens becomes a more rounded shape, so light is refracted more
