Download Cell

• Zygote: fertilized cell
created by the union of
the egg and sperm
• >200 types of human
cells
• Embryonic stem cells
– Created during
earliest divisions
– Potential to become
any type of cell
Determination
• Determination
– Stem cells
commit to a
specific type
– Few weeks into
development
– Irreversible
Differentiation
• Differentiation
– Cells acquire the
structures &
functions of a
specialized cell
– Specific genes
activated
Quick Questions
• Do your muscle cells have the same DNA as your skin
cells?
Yes
• Do your skin cells have the same DNA as your brain cells?
Yes
• Do your brain cells have the same DNA as your liver cells?
Yes
• So if all your cells have the same DNA, how do they know
to do different jobs?
Stay tuned for the answer
Stem cell programmed to become a muscle cell
Gene A
Gene B
Gene C
Gene D
Gene E
Gene F
Gene G
How
the the
top same
cell know
to become
a muscle
cell…and
If theywill
have
genes…how
does
one become
a the
bottom
become
a nerve
cell if they have identical genes?
muscle to
and
the other
a nerve?
Stem cell programmed to become a nerve cell
Gene A
Gene B
Gene C
Gene D
Gene E
Gene F
Gene G
Stem cell programmed to become a muscle cell
Gene A
ON
ON
Gene B
Gene C
ON
Gene D
Gene E
Gene F
Gene G
Remember that genes tell cells to create proteins. Muscle
During
“differentiation”,
genes
are on the
cells create
different proteins certain
from nerve
cells based
activated
in some
genes that are
active. cells, but deactivated in others.
Stem cell programmed to become a nerve cell
ON
ON
Gene A
Gene B
Gene C
ON
Gene D
Gene E
Gene F
Gene G
Programmed
cell death
(apoptosis)
between the
fingers
Webbed Toes
• Cell: Basic unit
• Tissue: Group of cells
– 4 types
• Organ: Groups of
tissue
– Ex: lung contains
each tissue
• Organ System: Group
of organs working
together
– Digestive System
• Organism: all organ
systems working
together
Epithelial
Tissue
Nerve
Tissue
Muscle
Connective
TissueTissue
•Transmit
protection
sheetsignals
of cells
•
electric
• Contracting
• Support the
cells
body
•Brain
skin, &
stomach
lining
•
Spinal
Cord
• Skeletal,
• Bone, fat,
cardiac
tendons
cells
Homeostasis
• Process where the
body maintains a
constant internal
environment
• Reactions &
enzymes work best
in specific
conditions
• Control systems
adjust to
internal/external
changes
– pH, temp, fluids
Control Systems
• Sensors (aka: receptors)
– Gather information about the body
and environment
– Ex: skin senses pressure
• Communication Center
– Messages sent throughout the
body to respond
– Ex: Impulse travel through your
nerves
• Control Center
– Receives information from the
sensors
– Ex: Brain interprets the impulse
• Targets
– Body part that changes its activity
– Ex: Muscles in foot stretch/contract
abruptly
!*%!?%&#
Negative Feedback Loops
• Regulates most
of the body
• Counters
changes in the
body that move
conditions away
from a set point
– Reverses the
change
• Keeps internal
environment
stable
Positive Feedback Loop
• Increases the
changes away from
set points
• Important when rapid
changes needed
• Ex: Oxytocin
released
– When uterus
contractions begin,
oxytocin released
to speed up the
contractions (not
stop them)
Working Together
• Thermoregulation: Maintenance of body temperature
– Skin: sensors provide feedback to brain
– Nervous & Endocrine system: send messages to/from brain
– Muscles: Start to shiver
Homeostasis
disruption
• Sensors fail
• Wrong messages sent
• Message doesn’t reach
target
• Serious injury
• Microorganism infection
• Short Term
– Temporary discomfort
(usually)
Long Term:
Diabetes
• Normally
– Glucose in blood rises after
meals
– Pancreas releases insulin
– Cells absorb the excess
glucose
• Type 1
– Glucose rises after meals
– Pancreas unable to make
insulin
– Blood pH decreases as
glucose builds up
• Type 2
– Glucose rises after meals
– Pancreas does not make
enough insulin
– Blood pH decreases as
glucose builds up