BIO230H1 Lecture Notes - Lecture 6: Tectorial Membrane, Basilar Membrane, Epithelium
BIO230
Lecture 6
!
Stem cells - undifferentiated biological cells that can differentiate into specialized cells and
can divide (through mitosis) to produce more stem cells. They are found in
multicellular organisms.
Stem cell is
- not teminally differentiated (told what kind of cell to become);
- can divide without limit;
- its daughters can remain a stem cell or differentiate;
!
Cell!turnover!–!the$replacement$of$old$cells$with$newly$generated$ones.$$
$
Ex#1$$
Auditory$hair$cells$in$the$organ&of&Corti.&
$
Organ!of!Corti$–$a$receptor$organ$for$hearing$and$is$located$in$the$mammalian$cochlea.$$
$
Tectorial!membrane$and$basilar!membrane$are$two$acellular$gels$in$the$inner$ear.$$
$
Hair cells perceive sound waves and send signals via the nerve.
They contain stereocilia - the mechanosensing organelles of hair cells, which respond to fluid
motion in numerous types of animals for various functions, including hearing and balance.
Stereocilia ae connected via cadherin, which is connected to ion channel.
Stereocilia are filled and supported by actin. Threadmilling of actin occurs à there is a constant
flux of actin through stereocilia.
Permanent hearing loss – caused by loss of hair cells from disease, toxins or extreme noise. In
mammals, hair cells do not re-grow.
Ex#2
Photoreceptor cells in the retina
$
Pulse-chase experiment is a method for examining a cellular process occurring over time by
successively exposing the cells to a labeled compound (pulse) and then to the same compound in
an unlabeled form (chase).
Cells are exposed to radiolabeled leucine, labeled amino acid is incororated into newly
synthesized proteins fr a short period of time. The molecule is stained and its pathway is
followed. The epithelial cell the photoreceptor is attached to is 'eating' the photoreceptor
molecular composition. Therefore, the detectted molecule will go up, until it reached the
epithelial cell.
Molecular!turnover$–$the$replacement$of$old$molecules$with$newly$generated$ones.$
Examples of molecular turnover:
- Photoreceptors
- Bone (bone is constantly made and destroyed)
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Document Summary
Stem cells - undifferentiated biological cells that can differentiate into specialized cells and can divide (through mitosis) to produce more stem cells. Not teminally differentiated (told what kind of cell to become); can divide without limit; its daughters can remain a stem cell or differentiate; Cell turnover the replacement of old cells with newly generated ones. Auditory hair cells in the organ of corti. Organ of corti a receptor organ for hearing and is located in the mammalian cochlea. Tectorial membrane and basilar membrane are two acellular gels in the inner ear. Hair cells perceive sound waves and send signals via the nerve. They contain stereocilia - the mechanosensing organelles of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance. Stereocilia ae connected via cadherin, which is connected to ion channel. Threadmilling of actin occurs there is a constant flux of actin through stereocilia.
