Transcript A12-Cell Specialization

Cell Specialization
Unicellular organism – consists of only one
cell
– That one cell carries out all functions required
to maintain the life of the organism
Multicellular organism – consists of more
than one cell
– Cells are specialized to perform certain
functions (cell specialization/differentiation)
Examples of Cell Specialization
1. Neuron (nerve cell):
– Sends info. from one part of the body to
another
– Very long and thin
Examples of Cell Specialization
2. Red blood cells:
– Carry oxygen throughout body
– Flattened disks so that they can easily flow
through blood vessels
Close-up: Blood cells in capillary
Examples of Cell Specialization
3. Sperm cell:
– Fertilizes egg
– Strong tail for quick swimming, distinct head
for entering egg cell
* Cell differentiation is a
result of different
gene expression.
Cell Communication
• Cells communicate with one another by
secreting and receiving chemicals
Cell Communication
• Chemicals released by one cell can
influence the activity of another cell.
– Ex: sensory cells to nerve cells to muscle cells
Cell Communication
Hormones = communication
chemicals that
travel through the
blood
– Secreted by endocrine
glands
– Acts much slower than
nerve impulses but effects
last much longer
– Only influence the action of
target cells that have
specific receptors
– Two mechanisms:
• Negative feedback
– The end product stops the production of a hormone
initially secreted
• Positive feedback
– The last step triggers more release of the hormone
initially secreted
Birth process triggered by
low levels of progesterone
↓
Stimulates release of
oxytocin
↓
Uterus contracts,
stimulates more oxytocin
release
↓
More contraction
↓
Baby is born!