The Nervous System and Mitosis - TOPIC 2 Flashcards
what is mitosis
when a cell reproduces itself by splitting in two to form two genetically identical offspring
what is the product at the end of mitosis
two new genetically identical diploid daughter cells
what are the 5 stages of mitosis
interphase
prophase
metaphase
anaphase
telophase
what happens in interphase
the cell grows and increases the amount of sub cellular structures it has and also duplicates its DNA
what happens in prophase
chromosomes condense and the membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm
what happens in metaphase
chromosomes line up in the middle of the cell
what happens in anaphase
spindle fibres pull the chromosomes apart and the 2 arms of the chromosomes are pulled to opposite end of the cell
what happens in telophase
membranes re-form around each of the sets of chromosomes and they become the nuclei of the two new cells
what is cytokinesis
before telophase ends, cytoplasm and cell membrane divide to form 2 separate cells
what are the uses of mitosis
it is used by multicellular organisms to grow and replace cells which have been damaged AND by some organisms to reproduce by asexual reproduction
number of cells =
2^number of divisions by mitosis
how do animals grow
By cell division when animals are young but when they are old, cell division is only used to replace old or damaged cells and cell differentiation is lost early
how do plants grow
by cell elongation, but unlike animals, they continue to differentiate
where does cell division take place in plants
in the tips of roots and shoots (meristems)
what is a tumour
a mass of abnormal cells
what is cancer
the result of changes in cells that leads to uncontrolled cell division
what are stem cells
undifferentiated cells
what can stem cells do
divide to produce lots more undifferentiated cells which can then develop in to different types of cells
where are stem cells found
in early human embryos or in bone marrow
what are embryonic stem cells used for
growth and development of organisms and replace damaged cells
what are stem cells used for in adults
they are used to replace damaged cells
how are stem cells used in medicine
they are used to cure diseases such as sickle cell anaemia
what are the potential risks of using stem cells in medical treatments
tumour development
disease transmission
rejection
ethical issues
what are meristems used for in plants
they produce unspecialised cells which can form any cell type in the plant so they go on to form specialised tissues like xylem and phloem
what is a stimuli
changes in the environment
what does the CNS consists of
the brain and spinal cord only
what are effectors
muscles or glands which respond to nervous impulses and bring about a response to a stimulus
how do muscles respond to nervous impulses
by contracting