SB2 - Cells And Control Flashcards
What’s the cell cycle
A process to repair and require new cells for growth
Make new cells
How many chromosomes do human body cells have
23 pairs and 46 in total
What are cells with 2 sets of chromosomes called
Diploid
What are haploid cells
Give me an example too
When a cell contains only 1 copy of each chromosome
Gametes are haploid (sex cells)
How many phases are in the cell cycle
2
Interphase and mitosis
Tell me about the interphase
Cell makes extra sub cellular cell parts eg mitochondria. DNA replication also occurs
Copies of chromosomes are made, copies stay attached to eachother and look like X’s
Tell me about mitosis
The second stage in the cell cycle
Cell splits to form 2 daughter which are identical to parent cell
It occurs in a series of stages
Tell me about the prophase
Nucleus starts to break down and spindle fibres appear
Tell me about the metaphase
The chromosomes are lined up on the spindle fibres accross the middle of the cell
Tell me about the anaphase
The chromosome copies are separated and moved to either end of the cell on the spindle fibres
Tell me about the telophase
A membrane forms around each set of chromosomes to form nuclei
Tell me about cytokinesis
A cell surface membrane forms to separate the 2 cells during cytokinesis
Cell walls form in plant cells
What’s asexual reproduction
Some organism can reproduce with just one parent
They produce clones
Relies on mitosis
What are clones
Means their cells have the same chromosomes as parent (genetically identical)
Which is faster sexual or asexual reproduction
Asexual Becuase organisms do not need others
Though sexual produces variation
What are cancer cells
Sometimes cells turn in to cancer cells and undergo uncontrollable division
Rapid division lead to growing link or tumours that c an damage body and result in death
What is growth
An increase in size as a result of an increase in number or size of cells
Cell number increased due to division by mitosis
Can be recorded by taking measurements over time, such as length or mass
What’s a percentile
For example 25% of babies will have masses below the 25th percentile so 75% will be below the 75th percentile line
So if the 25th percentile for an 8 month baby is 8kg then 25% of 8 month old babies have a mass below this value
What’s differentiation
A process that changes less specialised cell into more specialised ones
Then adapt to a new function
How is a red blood cell adapted
It has not nucleus so there’s more space for red haemoglobin molecules which carry oxygen
Also has a large surface area which allows oxygen to diffuse in and out more quickly
How are fat cells adapted
The cytoplasm is filled with large fat droplets
The fat is stored until
The body needs more energy
How are neurones adapted
Have a long fibre that carries electrical impulses around the body and many connections to other neurones
How are muscle cells specialised
Contain special contractile proteins that can shorten the cell
What are meristems
A group of cells near the end of each shoot and root that allows the plant to continue growing throughout their lives
The cells in meristems divide rapidly by mitosis
Many of these cells increase in length (elongation) and differentiate
Tell me some examples of specialised plant cells
Root hair cells
Xylem cells
How is a xylem vessel made
What’s it like
From dead xylem cells
It has a thickened wall to withstand water pressure
Tiny pores in wall allow water and mineral salts to enter and leave the vessel
There’s no cytoplasm so vessel is empty
Loses cell walls to form a tube
How can you measure the percentage changes of growth in plants
Final value - starting value divided by the starting value X 100%
What are stem cells
Cells that divide repeatedly over a long period of time to produce cells that then differentiate
Where are stem cells found in plants
Meristems (roots and shoots)
What are plant stem cells like
Usually able to produce any kind of specialised cell throughout their life
Not like most animals especially vertebrates
What are embryonic stem cells
The cells of an early stage embryo
They can produce into any type of specialised cell
As the cells starts to divide the embryo starts to develop different areas that will become different organs
The stem cells in these areas become more limited in the types of specialised cell they can produce
What are adult stem cells
When an animal is fully developed the stem cells usually only produce one type of specialised cell that is in the tissue around them
They allow tissues to grow and replace old or damaged cells
What else can stem cells be used for
Treating diseases caused by damaged cells
Scientists studied to use adult and embryonic stem cells to treat diseases such as type 1 diabetes or to replace damaged cells
This is done by stimulating stem cell to make them produce the specialised cells that are needed them injecting them where needed
What are some of the problems with using stem cells
If stem cells continue to divide inside body after being replaced they can cause cancer
stem cells from one person are often killed by the immune system of other people that are put into - called rejection
Where is the cerebral cortext
It’s divided into 2 cerebral hemispheres at the front of the brain
Where’s the cerebellum
Under the back of the brain near the spinal cord
What’s the cerebral cortex
Makes up 80% of brain
Used for most of our senses, language, memory, behaviour and consciousness
Divided into 2 cerebral hemispheres
What does the right hemisphere do
It communicates with the left side of the body
RIGHT Hemisphere communicate with the LEFT side of body
What does the left hemisphere do
Communicates with the right side of body
Tell me about the cerebellum
The base of the brain, the area is divided into 2 halves and controls bosh and posture
Coordinates the timing and fine control of muscle activity making sure movements are smooth
What’s the medulla oblongata
Controls your heart rate and breathing rate
Responsible for reflexes such as vomiting, sneezing and swallowing
What’s the spinal cord
The neurones that comedy to the medulla oblongata connect to the spinal cord
It’s about the width of a finger and consists of many nerves to carry info between the brain and rest of body
What are neurones
Bundles of neurones
In brain surgery what can electrodes be used for
Apply electrical currents to the brain
If patients are awake they can be asked what they feel
A current may also make the patient do something or stop an action occurring
This allows the functions of the brain to be investigated
What does scanning allow us to do
Look deeper into the brain than surgery does
Allows the study of healthy individuals without risk of damaging brain
What does a CT shape show
Shows the shapes of structures in the brain
An X-ray bean moves in a circle around the head and detectors measure the absorption of the X-rays
A computer used this to build a view of inside the body as a series of “slices” differences in the shapes in the brain can be linked to the function of those parts
What’s a PET scan
Shows brain activity as the patient is injected with radioactive glucose
Most active cells take in glucose than less active ones (for respiration) the radioactive atoms cause gamma rays which the dabbed defects
The more gamma rays coming from a certain area contain more active cells
What can spinal cord damage do
Reduces the flow of information between the brain and parts of the body
Nerve damage in the lower spinal cord can cause loss of feeling and use of legs
What’s quadriplegia
Damage of the spinal cord in the neck can cause loss of use of both arms and legs
Are there any cures for spinal cord damage
No adult stem cells can differentiate into neurones in spinal cord so no new neurones cannot be made to repair damage
Wires can be used to stimulate nerves and muscles below the damage but patients do not regain full movement of feeling
Treatments using stem injections are being developed
What’s a brain tumour
When cancer cells often divide rapidly to form a tumour
What are the effects of a brain tumour
May squash parts of the brain and stop them working
How can brain tumours be treated using radiotherapy
Tumours can be cut or killed using radiotherapy (high energy X Ray beams)
Can damage body and brain
Who can chemotherapy be used to treat s brain tumour
Injecting drugs that kill actively dividing cells
Can damage body and brain
Why Might chemotherapy not work
Due to the blood- brain farrier (a natural filter that only allows certain substances to get from the blood into the brain mainly due to fells in capillary walls fitting very close together
So chemicals won’t enter to kill cells
How can scientists study how the brain works
By growing brain tissue in a lab using stem cell techniques
What’s the vertebra
24 bones form the backbone to protect spinal cord
What’s the sciatic nerve
The thickest nerve that connects to the heal of the spinal cord
What is the central nervous system
(CNS) and it’d the brain and spinal cord which controls your body
Nerves make up the rest of Your nervous system - allows the parts of your body to communicate using electrical signals called impulses
What’s a stimulus
Anything your body is sensitive to including inside your body and your surroundings
Give me some examples of sense organs
Eyes, ears, skin
What detect stimuli
Sense organs that contain receptor cells
Eg. Skin contains receptor cells that detect the stimulus of temperature change
How do receptor cells crest a response
Receptor cells crest impulses which usually travel to the brain, the brain processes this information and can send impulses to the other parts of the body to cause something to happen (a response)
What’s neurotransmission
The travelling or transmission of impulses
Happens in neurones
What’s a sensory neurone (there are different types)
How does neurotransmission happen
It’s function is to carry impulses from receptor cells towards the CNS
A receptor cells impulse passes into a tiny branch Called a DENDRITE
Then it’s transmitted along the DENDRON and AXON
A series of axon terminals allows impulses go be transmitted to other neurones
What are dendrons and axons like(how are they adapted)
Frequently long to allow fast nuerotransmission over long distances
Also have a fatty layer surrounding these parts called the myelin sheath - is electrically insulates a neurone from neighbouring neurones, stopping the signal Losing energy
May also make an impulse jump along the cell between gaps in the myelin and so speed up neurotransmission
What do dendrites do
Receive impulses from receptor cells
What do axons do
Pass impulses on to other neurones
Where in the eye does it contain receptors
The retina - the back of the eye
What are cones
Receptor cells that are sensitive to the colour of light. Some cones detect red light while others detect green or blue
They generate impulses in sensory neurones that lead into the brain through the optic nerve
The information from all the cones is processed into full colour vision in the cerebral hemispheres
What are rods
Receptor cells that detect differences in light intensity not colour
Rods work well in very dim light whereas cones only work in very bright light
What’s the iris
The coloured part of the eye, the amount of light entering the eye is controlled by muscles in the iris
Which can constrict the pupil (decrease diameter) or dilate it (make it bigger)
Bright light can damage receptor cells in the retina
What’s the cornea
Clear colourless covering over eye that focuses light,
It refracts light to bring them together
Where’s the pupil
The dark area in the middle of the eye where light enters
What are the ciliary muscles
They make the lens fatter to focus light from near objects and thinner to focus light from distant objects
What’s the lens
It fine tuned the dividing to produce a very clear image
What’s being short sighted like
Distant objects appear blurred
There are 2 reasons
The eyeball is too long
The cornea is too curved and bends the Rays more than is should
Longsighted is the opposite
How can we fix short and long sightedness
Contact lenses or glasses of a laser can be used to cut away some of the cornea and reshape it
What’s a cataract
Sometimes a protein builds up inside the lens to make it cloudy
It can be restored by replacing the clouded lens with a plastic one
How is colour blindness caused
Due to some cones not working properly - the most common is red-green colour blindness in which the cones that detect green of it are faulty so it’s difficult to tell apart
It can’t be corrected
What are the effectors
They carry out at action
When a brain coordinates a response to a stimulus impulses are sent to the effectors
They include muscles and glands
What are motor neurones
They carry impulses to effectors
No DENDRON, dendrites on the cell body
What are relay neurones
They are short neurones that are found in spinal cord, they link motor and sensory neurones
Also make up a lot of nerve tissue in brain
No DENDRON
Dendrites are on the cell body
What’s a synapse
It contains a tiny gap when an impulse reaches an axon terminal, a neurotransmitter substance is released into the gap, it’s detected by the next neurone which generates a new impulses
Synapses slow down neurotransmission by are useful becuase neurotransmitters are only released from axon terminals and so impulses flow in one direction
Also allows many fresh impulses to be generated in many neurones connected to one neurone - the originals impulse does not less to be split and lose strength
What’s a reflex
Reflex actions are responses that are automatic and extremely quick to protect the body
They use neurone pathways called reflex arcs which bypass the parts of the brain involved in processing information and so are quicker than responses that need processing
Tell me the order of a response
Stimulus Receptor Sensory neurone Relay neurone Motor neurone Response