cell and control

Concepts

• we can use it to make large quantities of an identical copy of the plant in a short period by cutting it and putting it in rooting powder which would speed up the developing of root

The cell cycle

• the first stage in preparing mitosis called interphase

• interphase → The DNA will be replicable, subcellular structures will divide, the cell will grows

• the first stage of mitois is called prophase

• prophase → chomosomes condesnes, cell membrane will break, so the chromomes are free

• the second sstage of mitosis is metaphase

• metaphase → the chromosomes centrally aline

• the third stage of mitosis Is anaphase

• anaphase  →the cell fibres will pull each chromosones equal to each side

• the fourth stage of mitosis called telophase

• telophase → the chromosones decondense and nucleur mebrane reforms 

• the final stage of mitosis is cytokinesis

• cytokinesis →the cytoplasm and nucleur mebrane divides to form two genetically identical daughtersstem cells from plats

Mitosis and the cell cycle 

• cell division is  when a parent cell divides from two or more daughter cells

• There are 23 chromosomes of each cell of the body but in total 46, from your mother and father 

• Gametes have 23 chromosomes in total 

• A diploid number of chromosomes is the amount found in body cells 

• A haploid number of chromosomes is half the number of chromosomes in a body cell 

• The cell cycle is a serious of steps that the cell has to undergo in order to divicde 

• Mitosis is a type of cell divison

• asexual reproduction ocurs by mitosis in plants and simple anima;s

• the overall process of growth and division is known s the cell cycle

• a parent cell any cell that can carry out divison

• a daughter cell is something that comes out of a parent cell(product)

• there are two types of cell divsion:  mitosis and meiosis

• mitosis used is  for growth and repair

• Mitosis is a vital part of asexaul reproduction, as this type of reproduction only involves one organisms so to produce offspring it simply replicates its own cells 

• The set of chromosomes in the daughter cell’s nucleus are the same as the parent cell nucleus, mitosis producers 2 genetically identical diploid daughter cells 

• meiosis is used for making of gametes(the male sex cell)

• the rate at which a cell divides by mitosis is controlled by its genetic information

• a mutation might alter a gene controlling cell  division allowing cells to start dividig uncontrollably

• this can result in the formattion of a tumour

• two diploid daughter cells are produced each withidentical sets of chromosomes in the nucleus to each other and the origin parent cell

• mitosis is  a typpe of cell divsion which produces two genetically identical daughters

• chromosomes are long strands of dna

• subcellur structures  are  mitochondria ribosomesthe longest  step in cell divion is interphase

• xx is female

• xy is male

Stem Cells

• stem cells are undiffrented cells that can become other cell types

• undiffrentiated means not yet specialised/ not develop certain subcellular structures to function

• there are two types of stem cells in animals : embryonic and aduly

• an embryonic stem cells are stem cells found in embyo's and can develop all cell types - once the embryonic stem cell has changed

• adult stem cells are stem cells found in bone marrow, brain, small intestine and liver and can only develop into a few types of cells

• embryonic stem cells are potent becayse they can become all cell types

• Embryonic stem cells form when an egg and sperm cell fuse to form a zygote 

• adult stem cells are multipotent which is only some cells

• adult stem cells from bone marrow only come from red blood cells

• stemcells in plants are found within the merestem which is in the tip of the root and shoot

• unlike stemcells in animals, plant cekks will continue to diffrentiate throughout the lie of the plant

• red blood cells transportnoxygen around the body

• white blood cells defend illness can change its shape

whe stem cells divide they can make a new specalised cell

Theraputic cloning

• theraputic cloning could produce stem cells with the same genetic makeup as the patinet

• the technique involves the transfer of the nucleus from a cell of a patient to an egg celll whose nucleus has been removeda body cell has 46 chromosones

• Steps of theraputic cloniing :

• take the body cell first

• remove the nucleus from the egg cells

• put the nucleus from the egg cell in the bin

• remove nucleus from body cellls

• put it inside the empty egg cells

• give it an electric shock

• the cell will divide by mitosis to form an embryo

Embryonic stem cells

Adult stem cells

Diffrentiation

• diffrentiation means it has become specialised

• when a cells is speaciakised it means the cell has developed certain subcellular structures which allows it to carry out its job

• growth in height is continous and driven by elongation

• in animal cells, all growth occurs to mitosis, followed by diffrentiation into specialised cells

• this occurs when young and at full size

• further growth is for repair and replacement

• most types of animal cells differentiate in the early stage of devlopment

• most types of plant cells can differentiate throughout their life cycle

Nervous system

• the nervous system is a body communicating network

• it is made up of all the nerves, brain and spinal cord working together to carry electrical impulse around te body

• the effects aree muscles that contract and glands that produce hormoenes

• for the nervous system to react there must be a stimulus

• a stimulus is a change in the enviroment

• some thing must detert the change in the envioment, these are called receprots

• receptors are specialised cells that detect stimulus

• The nervous system is divided into two :

• perpheral nervous system which is made out of neurons

• CNS which is made of brain or spinal chord, central nervous system

• Some nerves are surrounded by a myelin sheath 

• The advantage of having nerves surrounded by myelin is that it allows the nerve transmission to travel faster 

• Myelin is produced by cells called schwann cells 

Three types of neurons

• the sensory neurone carries electroical impulses from the receptor to the CNS

• relay neurones carrys electrical impulses from the sensory to the motor neurone

• the motor neurone carrys electrical impulses from the CNS to the effectors

• Receptors are found in the five sensosry organs:

• the ear contains recpetors that detect sound

• eyes cotain receptors that detect light and colour

• the nose contains receptors that detect smell

• the tongue cotains receptors that detect chemicals in food

• the skin contains receptors that detect pressure and temperature

There are two types of action:

• concious action which requires the use of the brain because it is voluntary response

• reflex action is an automatic response which doesn't require the use of the brain. it is important because it saves you from danger

Examples of reflex action

• blinking

• knee jerve

• saliva

touching action

The gap between neurone (synaps)

• the electrical impulses change into near transmitters to go acrooss the synapse, they diffuse across and chage into an electrical impulse

• there is a stimulus which is a candle.

• it will be detected by the skin receotirs

• the sensory neurons will carry electrical impulses from the receptors to the CNS

• the relay neurone carrys electrical impulses from the snsory to motor neurine

• the motor neurone carrys electrical impulse from the CNS to the effectors which will contract to move the hand

The brain

• the brain is an organ made of billions of inter conected neurons

• it is responsible for complex behaviour

• The CNS is responsible for controlling consciousness,movement thoughts and emotions among other things 

• the brain is protected by the skull

• on between the brain and the skull you have a membrine called menninges

• the frontal lobe controls personality, emotion and self conrol

• the cerebral cortex controls problem solving, thinking

• the cerebellum os resposnible for muslce acitivity and balance

• the spinal cord is the top, and recives and processes

• the medulla is resposnible for uncnicous heart beat and breathing

• the pituitary gland is a master gland and produces lots of hormones

• hypothalamus helps to regulate body temperautre

• CT scan direct x-ray beams in a cicrular motion around the head and dreaof high density

• for example tumours will absorb more x raays and show up at white so CT scans are usful in diagnosing structural features

• A PET scan detects the brain actitity

• the docotr will give a patient a form of radioacitve glusocsethat emits radiation

• the gamma rays will come out and will be detected while the patient is doing activity, you can see a red glow. if it doesn't glow then it is damaged

• CT stands from computerished tomography 

• PET stands for positron emission tomography 

• CT scans are useful for examining bleeding within the sjulls and da,age to brain struccutees 

• CT scans are not recommended for pregnant women and children, as it exposes the patient to higher doses of radiation than a normal x ray 

• PET scans are useful for identifying cancerous tumour as these use more blood than normal tissue 

• PET scans themselves are sensitive to tracers, so areas where the racer builds up which will also be areas with greater boood flow will be highlighted more brightly on the resulting scan 

• Investigating brain function and treating brain damage is difficult because the brain is complex, it is easily damfed, drugs given to treat diseases cannot always reach the brain becaise of the membranes that surround it and it is not fully understood which part of the brain does what 

• Tumours can push against other structures and blood vessels in the brain, restricting their function 

• Tumours can be buried deep in the brain or spinasl cord, making them especially difficult to remove 

The Cancer

• there are two types of tumours : benign and malignant

• a beningn tumours is not cancerous because it doesn't invde other cells and tissues

• the malignant tumour can spread through the blood and invade other tissues and other organnelles, this is cancerous

• these tumours can recruit their own blood supply, they are cells and need oxygen and glucose

• benign tumours can become malignant if it tries to inade other cells

• the growth percentile shows the avergae where a child should be

• outside of these lines is a cause for concern

• odd growth atterns will need further investigation

• uncontolled cell division and growth results in the formation of a tumour, these can be benign or malignant, not all tumours are cancerous

• a tumour is a mass of cells

Benign tumours :

• growths of abrnomal cells

• contained in one area

• usually within a membrane surrounding the cells

• they do not invade other parrts of the body

Malignant tumour :

• growths of abnormal cells

• therse are cancerous

• invade neighbouring tissues and spread to diffrent parts of the body in the blood where they form secondary tumours

• can be caused by lifestyles or genes

Growth

• Growth occurs via cell division and differentiation 

• Growth is defined as an  increase in size  or mass

• Growth occurs in young animals by rapid cell division all over the body.

• As animals get older most cell division is simply to replace or repair damaged cells.

• Growth in plants occurs by cell division at the root and shoot tips

• . Cells increase in size or height by cell elongation.

• This happens throughout the plants life.

• Cell differentiation occurs as organisms develop and the cell changes to become 

• specialised

• As the cell  differentiates,  it forms different sub-cellular structures, e.g. the tail on a sperm cell or the hairs on a root hair cell.

• Most types of ANIMAL cells differentiate in the early stage of development.

• Most types of PLANT cells can  differentiate throughout their life cycle.

• elongation is when the cell grows in length or height

• in animals stem cells will become specialised and are in specfoc places to do specific things

• in plantsm stem cells diffrentiate throughout the life of a plant and are always found in the tip of the root and the shoots

• growth in height is continouse and is driven by cell elongation (in plants )

• all growth occurs due to mitosis, followed by diffrentiation into specialised cells ( in animals)

• genes control cell division and these genes can sometimes mutate and cause the cell to divide uncontrollablly leading to the formation of a tumour

• Plant cells can grow longer in a specific direction by absorbing water into their vaculoes and this is controlled by substances called auxins 

• A tumour is a group of cells that result from this uncontrolled division 

• Plants only differentiate when they reach their finail position in the plant, but they can still rediffrentiate when it is moved to another position 

Growth percentile charts 

• Percentile charts tell us the rate at which an organism of interest is growing 

• The growth of babies can be measured using mass length or head circumference 

• A baby born at the 50th percentile for mmass is heavier than 50% of babies 

• A baby born in 25th percentile for mass is heavier than 75% of babies 

• A baby born at the 75th percentile for mass is heavier than 25% of babies 

• Being in a high percentile can indicate a health problem 

The eye

• the eye is an organ that contains receptors that detect changes in light and the colour of light

• how the eye detects light

• light rays pass though the transparent front of the eye, this is called the cornea

• the job of the cornea is to focus on the light rays

• the light rays then pass through the pupil in the centre of the iris

• the iris is the coloured part of the eye

• the light rays now pass through the lens

• the role of the lens is to focus the light onto the back of the eye

• the lens can change its shape which allows us to focus on near or distant objects. this is called acoomodation

• the light rays are now focused onto the back of the eye, this is called the retina

• the retina contains receptor cells for light

• these receptor cells allow us to detect light intesnity and lihgt colour

• the receptor cells in the retina send electric impulses down the optic nerve to the brain

• parts of the eye

• The  retina contains rod cells and cone cells, each of which convert light to nerve impulses destined for the brain 

• Rod cels are more sensitive to light so they are better for seeing in low light 

• Cone cells allow colour vision 

• the white part of the eye is called the sclerea. this tough outer structure protects the eye

• the cicillary muscles and the suspensory ligaments work with the lens. together they allow us to focus on near and far objects

• the pupil is the space in the centre of the iris which light passes through

• the pupil allows light rays to pass thrugh it

• the role of the iris is to control the size of the pupil

• in a dark room, the amount of light entering the eye is low, the drop in light intensity is sensed by the light receptors in the retina and these send electrical impulses to the brain. the brain then sends electrical impulses to specific muscles in the iris . these muscles contract causing the pupil to become larger .this now allows more light to enter the eye. this is a reflex action because it does not involve the concious part of the brain.  The circular muscles relax and the radial muscles contract to make the pupil larger, so more light can eneter to create a better image 

• in a bright room, the reflex causes the pupil to become smaller which reduces the amount of light entering the eye and protects it from damage. The circular muscles contract and the radial muscles relax to make the pupil smaller to avoid damage to the retina 

how the eye focuses: 

• the majority of the focusing comes from the cornea, but the cornea is a fixed focus

• the rest of the focusing is carried out by the lens

• the lens allows you to focus on near and distant objects

• the shape of the lens can change

• the ability to change the shape of the lens to see near or distant objects is called accommodation

how does accomodation take place :

• the lens is surrounded by a circular muscle called a cillary muscle

• this is connected to the lens by fibers called suspensory ligaments

• by contracting or relaxinb, the cilliaary muscle can change the thickness of the lens

• when the cillary muscles contract, the suspensory muscles loosen. the lens is now thicker and the light rays refract more strongly - to focus on a near pbject

• when the cillary muscles relax, the suspensory muscles tighten, the lens is pulled thin and now slightly refract the light rays - to focus on a far object 

light from distant objects need to be focused only a relatively small amount . the cillary muscles will relax and the suspesory ligaments will tighten. the lens is now pulled thin and because the lens is thin, it only refracts light rays slightly 

 Eye defects 

• Eye defects occur when light cannot focus on the retina 

• Myopia is short signtness 

• Myopia is when the lens is too curved so distant object appear blurry 

• Hyperopia is long sightness 

• Hyperopia is when the lenbs is too flat, so it cannot refract light enoug 

• Other defects include cataracts and colour blindness 

• Caractaracts means clouding of the lens of the eye 

• This can often occur from birth but also can develop over time 

• It restricts vision and can be treated by replacing the lens of the eye in surgery 

• Colour blindness is the inability to see certain colours 

• Full ccolour blindness is rare, whereas specific colour blindness is very common 

• This usually occurs because people with the condition do not have enough con cells int their retina. This is usually genetic

• Spectacle lens are concave lenses that spread out the light ot treat myopia and convex lens to bring the rays together to treat hyperopia 

• Contact lenses  allows activities such as spirit to be carried out, hard or soft contact lenses last for different lengths of time and they work in the same way as glasses 

• Laser eye surger can reduce the thickness of the cornea, so refract the light less to treat myopia or change its curvature, so it refracts light more strongly to treat hyperopia 

• Replacement lens can treat hyperopia by adding platic on top of the natural lens or using an artificial one made of clear plastic, the risks include damage to retina or cataracts developing