SB2 Flashcards
What are the stages of the cell cycle
Interphase, mitosis, cytokinesis
Describe what happens in interphase
DNA replication and the production of extra sub-cellular parts (eg: mitochondria)
Explain what happens in interphase
Each chromosome is copied, the copies remain in X-shapes
Ribosomes and mitochondria increase in numbers
Cell increases in size
What happens in prophase
The membrane around the nucleus disappears and spindle fibres appear
What happens in metaphase
The chromosomes line up on the spindle fibres across the middle of the cell
What happens in anaphase
The chromosome copies are separated and move to either end of the cell on the spindle fibres
What happens in telophase
New membranes form around each set of chromosomes, this forms nuclei
What happens in cytokinesis
A cell membrane forms to separate the two cells (cell walls form in plant cells)
What causes the production of cancer cells
Uncontrollable cell division
What is produced by mitosis
2 genetically identical diploid cells
Suggest three ways you can measure a baby’s growth
Weigh it to calculate its weight
Measure its length
Measure its head circumference
What is differentiation
When less specialised cells turn into more specialised ones
What are meristems
Undifferentiated group of cells near the end of each shoot and root that allows plants to continue growing throughout their lives
What do meristems do
They divide rapidly by mitosis
What happens in the zone of division
Dividing of meristem cells
What happens in the zone of elongation
Where cells produced increase in length
What happens in the zone of differentiation
Tissues/Cells become differentiated
What are stem cells
Cells that have not yet undergone cell differentiation
What are embryonic stem cells
Cells of an early stage embryo, it can turn into any type of specialised cell
What are adult stem cells
Stem cells that can only produce the type of specialised cell that is in the tissue around them
How can you use embryonic stem cells to create specialised cells
You can stimulate stem cells to make them produce specialised cells then inject them into the places they are needed
How can stem cells cause cancer
If the stem cells continue to divide inside the body after they have replaced damaged cells
How can stem cells cause problems
Stem cells from another person could be rejected by the patient
What is the brain made up of
Neurones
Where is the cerebral cortex
The front of the brain, makes up 80% of the brain
Where is the cerebellum
At the back of the brain towards the lower part
Where is the medulla oblongata
Towards the bottom of the brain
Name three functions of the cerebral cortex
Language Senses Memory Behaviour Speech
Name three functions of the cerebellum
Balance
Posture
Timing
Name three functions of the medulla oblongata
Heart rate
Breathing rate
Reflexes such as sneezing and vomiting
What does scanning do
Shows the structure of a brain without the risk of damaging the brain
How does a CT scan function
An X-ray moves in a circle around the head and detectors measure the absorption of X-rays, denser materials absorb more X-rays, causing whiter areas
How does a PET scan work
Patient is injected with radioactive glucose, more active cells will take in more glucose that less active ones. Radioactive atoms cause gamma rays which can be detected by the scanner
Why can you never regain full movement if your spinal cord is destroyed
There are no adult stem cells that can differentiate into neurones so neurones cannot repair damage
Name some disadvantages of chemotherapy
The blood-brain barrier could prevent drugs from killing tumours in the brain
They can damage the body and brain
What do PET scans do
They show brain activity
What does the myelin sheath do
It’s a fatty layer that acts as an insulator and speeds up nerve impulses
What do dendrites do
Receive impulses from receptor cells/other neurones
What do axon terminals do
They pass impulses onto other neurones
Describe the stages of picking something up
Receptor cells in the eye transmit impulses to sensory neurones in the optic nerve to the brain. The brain sends an impulse to the motor neurone (muscle) and the muscles in the hand receive the impulses and pick up the object
What are cones
Colour sensitive receptor cells in the eyes
What is the retina
The part at the back of the eye that contains receptor cells
What are rods (eyes)
Receptor cells that detect differences in light intensity
Difference between rods and cones
Rods work very well in dim light, cones work really well in bright light
Where are rods and cones
In the retina
What is the iris
The coloured part of the eye that controls the amount of light entering the eye by constricting and dilating the pupil
What does the lens do when focusing on closer or further objects
Closer- It gets fatter to bend the light rays more
Further- It gets thinner to cause less light ray bending
What does the cornea do
Allows light to enter, slightly causes bending of light
What happens to ciliary muscles when looking at a nearby object
They contract (and the suspensory ligaments slacked)
What happens to ciliary muscles when looking at a further object
They relax and the suspensory ligament stretch
What is short sightedness (myopia)
When distant objects cannot be seen properly because the rays of light are focused in front of the retina
What is long sightedness (hyperopia)
When close objects cannot be seen properly because rays of light are focused behind the retina
What is cataract
When protein builds up inside the lens, making it cloudy (can be corrected by replacing the lens)
What is colour-blindness
When cones do not work properly, causing difficulty in seeing colours
What is a synapse
A tiny gap
What are synapses used for
Generating a new impulse so the original impulse doesn’t lose its strength
What is a neurotransmitter
A substance that diffuses across a gap between two neurones
Name the steps an impulse goes through in a reflex arc
Stimulus -> Receptor cells -> Sensory neurones -> Relay neurone (spinal cord) -> Motor Neurone (in muscle or gland) -> Effector
