Notes 10-28-09

Regulation of the Cell Cycle-A molecular control system drives the cell cycle-Cell-Cycle Checkpoints

G1 – some cells never get past this point, divide at this point.-stimulus [ex. cut, cell division fills gap]

-neurons grow during embryo stage, once born, neurons stop dividing

-Nerve damage cannot be fixed because of this

G2 – prevents cell from moving into mitosis before its readyMitosis follow G2 checkpoint.Checkpoint needed so that cell does not divide until cytokinesis occurs

Cancer

Tumor =>abnormal mass of cellsBenign tumor => mass of [rapidly dividing] cells – cells remain at original

site in the bodyMalignant tumor => a cancerous growth – can spread to other surrounding

tissues or parts of the bodyMetastasis – cancer cells that can move to other parts of the body

[unsticky cells break off and tumour can become malignant]Carcinomas – external or internal coverings ex. skin, lining of digestive

tract. Epithelial.Sarcomas – support tissues ex. bone, musclesLeukemia and Lymphoma – in the blood forming tissues such as bone

marrow, spleen, lymph nodesLeukemia – high white blood cell count, bone marrow cells producing blood cells produces too many white blood cellsLymphoma – cells originate in bone marrow, travel through bloodstream—tumour in lymph nodes or spleen. Cells originate in blood system.

Characteristics of an Abnormal Cancer Cell-DNA has been damaged/mutated [caused by mutogens]-Divide out of control-Divide indefinitely “immortal”-Do not need to be anchored to divide-Changes in appearance – “Dysplasia”

-large nuclei, atypical shape, increased DNA

-Cancer cells look like embryo cells, divide rapidly as embryo cells do-Dysplasia is what is looked for in biopsies

Progression of a tumor’s growth-Initial tumor cell-Small mass of rapidly dividing cells-Carcinoma in situ [in place] –any tumor, anywhere reffered to -Invasive carcinoma – growth factors produces blood vessel growth into tumor

-blood vessels grow into body of carcinoma-energy originally provided by diffusion-often, tumor cannot get enough energy and dies off-blood vessel forms, providing energy for growth-blood vessels can transport cells around the body

-metastasis

-term cancer comes from zodiac “crab” shape that tumors can take on

How does cancer kill?-By interfering with the ability of body cells to function normally-cancer cells are greedy-tumors may block blood vessels, air passages or press on vitalnerve pathways in the brain.