Topic 2 - Cells and control Flashcards
What does mitosis produce
Two genetically identical cells
What do organisms use mitosis for?
Growth and repair
What happens during interphase
The cell grows and the subcellular structures increase
The DNA is duplicated and formed X shaped chromosomes
What happens during prophase?
The chromosomes condense and the nuclear membrane breaks
What happens during metaphase?
The chromosomes line up at the centre of the cell
What happens during anaphase?
Spindle fibres pull the chromosomes apart and pull the chromotids to opposite ends of the cell
What happens during telophase?
Membranes form around the chromosomes
What happens during cytokinesis?
The cytoplasm and cell membrane divides to form separate cells
How do you calculate the number of cells made?
2^n
What is cell differentiation?
The process by which a cell changes to become specialised for its job
How do plants grow that animals cant?
Cell elongation
What is cell elongation?
Where a PLANT CELL expands, making the cell bigger and so making the plant grow
For adult animals, what is mitosis mostly used for?
Repair and replacement
What is cancer?
Uncontrolled mass cell division
Where is the rate at which cells divide located?
The genes
What is a tumour?
A mass of abnormal cells
How do you read a percentile chart?
Plot a line to the data and read the percentages
Name a process thats used for growth in plants but not in animals?
Cell elongation
How does a plant grow through cell elongation?
Elongation allows a cell to expand so the cells get bigger and the plant grows
What can stem cells do?
Differenetiate into different types of cells
What are undifferentiated cells called?
Stem cells
How do stem cells divide?
Mitosis
What can embryonic stem cells produce?
Any type of cell
What are adult stem cells used for?
Replacement of damaged cells
Where are stem cells found in plants?
Meristems
Where are meristems found?
Areas of a plant that are growing (roots and shoots)
What are the risks of using stem cells?
Disease transmission
Rejection
Tumour development
Why is tumour development a risk for stem cells?
Because stem cells divide very quickly therefore if left uncontrolled a tumour may develop
Why is virus transmission a risk with stem cells?
As viruses live in cells, if donor cells are infected the virus can be passed on
Why is rejection a risk with stem cells?
If the cells aren’t recognised by the body and are percieved as foreign an immune response may be triggered
What are the benefits of stem cells in medicine?
Can be used to replace tissues damaged by disease or injury
If the tip is cut off plant shoot, the tip can be used to grow a whole new plant
Explain why?
The shoot contains meristem which when planted will mass divide and differentiate into specialised cells that are required for growth
What is the spinal cord?
A long column of neurones that run from the base of the brain down the spine
What is the cerebrum in charge of?
Movement, vision, language, memory and intelligence
What is the cerebellum in charge of?
Balance and muscle coordination
What is the medulla oblongata in charge of?
Unconscious activities (eg. Breathing and heart rate)
How do CT scans work?
X-rays are used to produce an image of the brain
What do CT scans show?
The main strucutres in the brain
How can a CT scan be used to show a fuction?
If an area of the brain is damaged and a fuction is lacking the function can be tied to that area
How do PET scans work?
Radioactive chemicals are used to show which parts of the brain are active
What do PEt scans show
Real time video of the structure and function of the brain
Explain how the difficulties of accessing brain tissue
inside the skull can be overcome by using CT scanning
and PET scanning to investigate brain function
Instead of having to ‘go in and look’ you can instead use technology to visualise the inside
Why is treating problems in the CNS hard?
It is hard to repair
It can be hard to access
Treatment can lead to permanent damage
Why is it hard to repair damage in the CNS?
The CNS doesn’t readily repair themselves and scientists haven’t developed a way to repair it
What is the stages to a nervous response?
Stimulus -> Receptor -> Sensory Neurone -> CNS -> Motor Neurone -> Effector -> Response
What is the reaction time?
The time it takes you to respond to a stimulus
What do all neurones have?
A cell body with a nucleus and cytoplasm
What do dendrites and dendrons do?
Carry nerve impulses towards the cell body
What do axons do?
Cary never impulses away from the cell body
What are some axons surrounded by?
Myelin sheath
What is the function of a myelin sheath?
An electrical insulator which speeds up the electrical impulse
Why are longer neurones fastest?
There is less time wasted in synapses
State the three types of neurones?
Sensory
Motor
Relay
Describe a sensory neurone?
One long dendron from receptor cells
One short axon
Describe a motor neurone?
Many short dendrites from the CNS
One long axon to effector cells
Describe a motor neurone?
Many short dendrites
Describe a relay neurone?
Short dendrites from sensory neurones to the cell body
Axon that carries impulses to motor neurones
Describe the structure and function of a sensory neurone?
A sensory neurone has one long dendron and one short axon with a cell body in the middle
The function is to carry impulses from receptor cells to the CNS
What do synapses do?
Connect neurones
How is the nerve signal transferrred between synapses?
Neurotransmitters
How do neutrotransmitters work?
They diffuse across the gap
Why do synapses slow down reaction times?
Because it takes time for the neurotransmitters to diffuse across the gap
What are reflexes?
Automatic, rapid responses to stimuli
What is a reflex arc?
The passage of information in a reflex
What do the neurones in a reflex arc go through?
The spinal cord or an unconscious part of the brain
Describe the path of a reflex arc?
Stimuli -> Sensory neurone -> Relay Neurone -> Motor Neurone -> Effector
Why are reflex arcs faster than a normal response?
There is no time spent thinking about the response
A chef touches a hot tray. A reflex reaction causes him to immediately move his hand away
Describe the pathway of the reflex arc from receptors to effector
Receptors -> Sensory Neurone -> Relay Neurone -> Motor Neurone -> Effector
What does the cornea do?
It refracts the light into the eye
What does the iris do?
Controls how much light enters the pupil
What does the lens do?
Refracts light focusing it on the retian
What does the retina do?
Detects light by being covered in receptor cells
What are the receptor cells?
Rods and cones
What do rods do?
Sense light but no colour
What do cones do?
Sense colours but not light
Where does the information from the eye go to?
The brain along the optic nerve
What happens when the eye looks at distant objects?
The ciliary muscle relaxes, which allows the suspensory ligaments to pull tight
The lens are pulled into a less rounded shape so light is reflected less
What happens when the eye looks at close objects?
The ciliary muscle contracts, which allows the suspensory ligaments to slacken
The lens are becomes into a more rounded shape so light is reflected more
What is long-sightedness?
When people are unable to focus on near objects
When does long-sightedness occur?
When the lens doesnt bend the light enough or the eyeball is too short
What lens fixes long-sightedness?
Convex
What is short-sightedness?
When people are unable to focus on distant objects
When does short-sightedness occur?
When the lens bends the light too much or the eyeball is too long
What lens fixes short-sightedness?
Diverging
What causes colour blindness?
Malfunctional cones
Why is there no cure for colour blindness?
Cone cells cant be replaced
What is a cataracts?
A cloudy patch on the lens
Explain how a structural problem with the eye may cause a person to be long-sighted?
The lens could be the wrong shape so it doesn’t bend the light enough so an image is formed behind the retina or, the eyeball is too short so the image is formed behind the retina
Describe how animals grow?
Through cell differentiation and divison
Describe the role of neurotransmitters in the transmission of nervous impulses?
They are the molecules used by the nervous system to transmit messages between neurons
Which part of the eye controls how much light is entering the pupil?
The iris
