cellular adaptations Flashcards
what regulates normal cell proliferation
proto-oncogenes and tumour suppressor cells
what happen when checkpoint is activated on cell cycle
p53 protein is activated
suspends cell cycle and triggers DNA repair mechanism
if DNA cant be repaired apoptosis will occur
how is the cell cycle controlled
by cyclins (proteins) and associated enzymes called cyclin dependent kinases
CDK become active by binding to cyclin
active CDK drives cell cycle by phosphorylating proteins
what is the role of retinoblastoma protein
prevents DNA replication
inactivated by phosphorylation with CDK4 complex
how is activity of cyclin-CDK complex regulated and what is the affect of growth factors on all of this
regulated by CDK inhibitors
some GF work by shutting off the production of CDK inhibitors or stimulating production of cyclins
what is cell adaptation
state between normal unstressed cell and an overstressed injured cell
what is hyperplasia
cells increase in number due to increased functional demand or external stimulation
occurs in labile (continuously dividng cells e.g skin, mucosa,BM) / stable( resting cells e.g kidney, smooth muscle cells) cells
neoplasia is when it becomes an abnormal and excessive amount
what is hypertrophy
Cells increase in size
occurs in labile/stable cells
seen especially in permanent cell populations as these cells have little/no replicative potential.response to high functional demand/hormonal stimulation
skeletal muscle hypertrophy in body builders
smooth muscle hypertrophy in pregnancy
what is atrophy
cells become smaller
redyced supply of GF or nutrients can lead to this
cells have fewer structural components and reduced function.
what is metaplasia
cells are replaced by cells of a different type
reversible
adaptive reponse
most common in epithelial cells where columnar epithelium (fragile) becomes squamous(more resilient)
physiological hyperplasia is due to….
hormones when the result is an increase in functional capacity
compensatory when there is an increase in tissue mass after tissue damage
e.g hormones oxytocin, prolactin lead to physiological hyperplasia of breast tissue enabling lactation.
why would there be pathological hypertrophy to the heart
hypertension
valvular heart disease
benign prostatic hyperplasia
hypertrophied detrusor muscle
obstructed urinary flow
detrusor muscle has to work harder to voice urine through narrowed urethra
is atrophy reversible
yes to a point
not after parenchymal cells are replaced by connective tissue.
causes of pathological atrophy
reduced work load loss of innervation decreased blood supply inadequate nutrition loss of endocrine stimulation persistent injury aging pressure occlusion of secretary duct toxic agents x ray s immunological disease
