CB2 - Cells and Control

• Name all stages of mitosis

  Prophase, Metaphase, Anaphase, Telophase and Cytokinesis
• What is mitosis?

  A type of cell division within the cell cycle in which produces two daughter cells, which are identical diploid cells.
• Why is mitosis important in reproduction? 


  Some organisms can use mitosis to reproduce asexually, producing offsprings which are identical to them (clones). Asexual reproduction is much faster than sexual reproduction as it does not include a mate.
• How is cancer caused?

  Cancer is the result of the change in cells that lead to uncontrolled cell division, resulting in lumps or tumours, that are harmful to the body.
• What happens in prophase?

  The nucleus start to break down and spindle fibres appear.
• What happens during the metaphase?

  Chromosomes align on the spindle fibres in the middle of the cell.
• What happens during the anaphase?

  The chromosome copies are separated and moved to either end of the cell on the spindle fibres.
• What happens at the telophase?

  A membrane forms around each set of chromosomes to form nuclei.
• What happens during cytokinesis?

  A cell surface membrane forms to separate the two cells during cytokinesis, while cell walls form in plant cells.
• What is growth?

  The increase in size as a result of an increase in the number or size of cells, due to cell division by mitosis.
• How does growth occurs in animals?

  Through cell division by mitosis, and then further cell differentiation.
• What is cell differentiation?

  Process in which less specialised cells change to form specialised cells with different functions
• How does growth occurs in plants?

  Growth is a result of cell division through mitosis, elongation, where a cell increases in length, and cell differentiation
• What are meristems?

  Cells at the end of roots which allow plants to keep growing throughout their lives as they divide rapidly through mitosis.
• What are embryonic stem cells and what are their function?

  Cells of an early-stage embryo which can produce any type of specialised cells.
• What does CNS stand for?

  Central Nervous System
• What is the function of adult stem cells?

  The adult stem cells in human tissues allow the tissues to grow and replace old or damaged cells.
• What are the benefits associated with the use of stem cells in medicine?

  Stem cells offer a way of treating diseases caused by damaged cells - scientists stimulate stem cells to produce specialised cells that are needed and then inject then into the places in which they are needed within the human body.
• What are the risks of using stem cells in medicine?

  The uncontrolled division of stem cells can cause cancer and rejection can occur, when the immune system of one person kills the newly injected cells.
• What is rejection?

  When the injected stem cells are killed by the immune system of other people they are put into.
• What forms the CNS?

  The brain and spinal cord.
• What are the electrical signals which allow all parts of our body to communicate through the nervous system called?

  Impulses
• What is the function of receptor cells and where are they found?

  Found in sensory organs, receptor cells detect stimuli and create impulses, which travel to the brain, where they are processed to form a response.
• What is the function of a sensory neurone?

  It carries impulses from receptor cells towards the CNS.
• What pathway do impulses take through sensory neurones?

  A receptor cell impulse passes into a branch called the dendrite. It is then transmitted along the dendron and the axon. A series of axon terminals allow impulses to be transmitted to other neurones.
• What is the function of the myelin sheath?

  The myelin sheath electrically insulates a neurone from neighbouring neurones, stopping any loss of energy from the signal. It also allows an impulse to 'jump' from one cell to another, speeding up neurotransmissions.
• What are effectors?

  Effectors carry out actions as a response from the nervous system, usually including muscles and glands.
• What are relay neurones and what is their function?

  Relay neurones are short neurones that are found in the spinal cord, where they link motor and sensory neurones. They do not have a dendron and their dendrites are concentrated around the cell body.
• What are synapses and why are they important during neurotransmissions?

  Synapses are junctions (a tiny gap) between two neurones, which transfers impulses from one neurone to another - a neurotransmitter substance is released from one neurone and detected by another, which generates another impulse. They slow down neurotransmission, however they ensure impulses only flow in one direction and that the impulses do not lose 'strength' due to long journeys.
• What is the function of the reflex arc?

  The body reacts to harmful situations in a more automatic way.
• How does the reflex arc function?

  They use neurone pathways called reflex arcs, which bypass parts of the brain involved in processing information, resulting in quicker responses since you don't think about the action.

  Sensory neuron -> spinal cord -> motor neuron -> muscle