Topic 2 - Cells And Control Flashcards
What is a chromosome?
-contains coils of DNA
What is a gene?
- short section of DNA that codes for a protein
What is a gamete?
- sex cell e.g. egg & sperm
- has 23 chromosomes ( half) each
What is a diploid cell?
- full amount of chromosomes ( 46)
What is mitosis?
- cell reproduces by splitting to form two genetically identical daughter/ diploid cells
Beginning Phase of mitosis
Interphase
- The DNA in chromosomes copies itself ready for mitosis.
1st phase of mitosis
Prophase
- chromosomes condense (shorter & fatter) - nucleus membrane breaks down and spindle appearrs
3rd phase of mitosis
- Anaphase
- spindle pulls chromosomes to polar parts of cell & spindle fibres get short while pulling away
4th phase of mitosis
Telophase
- nucleus membrane reforms and chromosomes less condense and less visible and spindle disappears
last (sort of) phase of mitosis
Cytokenesis
- cell divides into two – mitosis now complete
How does cancer occur?
- small change in cells that leads to uncontrolled cell division
What is a stem cell?
-undifferentiated cell which can undergo division to produce more similar cells
What is therapeutic cloning?
- embryo produced with same genes as patient.
Types of stem cells
- embryonic stem cells
- adult stem cells (found in bone marrow)
- meristems in plants
Benefits of stem cells
- used to replace damaged or diseased body parts
- use unwanted stem cells that may have been thrown away
- further research into differentiation
Disadvantages of stem cells
- hard to control stem cells to form desired cell
- people have religious & ethical objections
- expensive and time consuming
What is the CNS?
- central nervous system – brain along w/ spinal cord
- controls conscience, movements, thoughts & emotions etc.
What is the cerebral hemisphere?
- perform variety of functions, including consciousness, memory, intelligence & visual and sensory processing
What is the cerebellum?
- structure found at bottom of brain, on rear side.
- responsible for muscle co-ordination, so can move in complex ways e.g. catching a ball
What is the medulla oblongata?
- small ‘elongated’ structure found at base of the brain.
- responsible for basic autonomic (automatic) bodily functions e.g. breathing, digestion, swallowing and sneezing.
What is a CT scan?
- fire X-Ray radiation at brain from different angles to generate 3D image of the brain
- used to examine bleeding within skull & damage to brain structure
- not recommended for pregnant woman or children- higher dose of radiation than X- ray
What is a PET scan?
- radioactive ‘tracer’ injected into blood before scan.
- areas with greater blood flow, will be highlighted & tracer will build up
- used for identifying cancerous tumours, because use more blood than normal tissue
What is the nervous system?
- allows us to react to surroundings & coordinate actions in response to stimuli.
How does the nervous system work?
- Receptor cells convert stimulus into electrical impulse.
- electrical impulse travels along cells called sensory neurons to CNS
- information processed and appropriate response is coordinated
- then electrical impulse is sent along motor neurons to effectors.
- effectors carry out the response e.g. muscles contracting
- impulses travel from sensory, to relay and then motor neuron
What is a reflex ?
- Automatic responses that take place before you have time to think
- they don’t travel through the brain
Describe how a reflex works?
- stimulus is detected by receptors.
- Impulses sent along a sensory neuron– impulse passes to a relay neuron – then a motor neuron.
- motor neuron passes impulse to an effector and effector stimulates a response
e. g. moving hand away from hot surface
What is a synapse?
- gap between two neurons
What is neurotransmitter?
- When impulse reaches end of first neuron, a chemical is released into the synapse.
How does a neurotransmitter work?
- chemical released into the synapse.
-neurotransmitter diffuses across the synapse. - When neurotransmitter reaches second neuron it triggers impulse to begin again in next neuron.
– Different neurotransmitters have different effects on
the frequency and speed of the impulse in the second neuron.
What is the myelin sheath?
- surrounds core of a nerve fiber or axon
What is a retina?
- Layer of light sensitive cells found at back of eye.
When light hits cells are stimulated impulses sent to brain
-interprets info to create image.
What are rod and cone cells ?
- found in retina
Rod cells - sensitive to light – better for seeing in low light
Cone cells - allow to interpret different colours (colour vision)
What is the cornea?
- see-through layer at front of eye.
- allows light through and curved surface bends (refracts) and focuses light onto retina
What is the iris?
- muscles that surround pupil
- contract or relax to alter size of pupil
What are ciliary muscles and suspensory ligaments?
- hold lens in place
- controls its shape & allows us to focus on objects nearer or further away
What is the lens ( eye) ?
- Transparent, curved surface on front of eye.
- like cornea, reflects light onto retina.
What is short sightedness?
- called myopia.
- lens is too curved, distant objects appear blurry
- need concave lens
What is long sightedness?
- called hyperopia.
- lens is too flat, so it cannot refract light enough
- need convex lens
How to focus on a near object
- ciliary muscles contract & suspensory ligaments loosen
- lens becomes thicker and more curved- this refracts light more
How to focus on a distant object
- ciliary muscles relax & suspensory ligaments tighten
- lens becomes thinner - light is refracted less.
What is a cataract ?
- clouding of the lens of the eye
How to treat short and long sightedness?
- concave lenses to spread out the light to treat myopia ( short sightedness)
- convex lenses to bring the rays together to treat
hyperopia ( long sightedness)
How does laser eye surgery work?
- used to reduce the thickness of the
cornea -so it refracts light less- to treat short sightedness - used to change its curvature-so it refracts light more strongly- to treat long sightedness
Examples of treatment for eyes?
- laser eye surgery
- wearing glasses or contact lenses
- replacement lenses
Explain cancer
- it is as the result of changes in cells that lead to
uncontrolled cell division
2nd phase of mitosis
- Metaphase
chromosomes line up at the equator of the cell
Function of the myelin sheath
- insulates impulse from surrounding tissue
- speeds up transmission
How is a red blood cell specialised
- no nucleus - so can increase its oxygen carrying capacity
- contains haemoglobin –to bind to oxygen
- flexible and small – to get through capillaries
