zygote: fertilized cell (egg + sperm) >200 types of human cells embryonic stem cells – created...
TRANSCRIPT
• Zygote: fertilized cell (egg + 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
Stem cell programmed to become a muscle cell
Stem cell programmed to become a nerve cell
ON ON ON
ON ON ON
Genes (switches) exist in both cells, but are activated in one type and deactivated in the other.
Differentiation
• Differentiation– Cells acquire the
structures & functions of a specialized cell– Specific genes
activated
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
• Muscle: contracting cells– Skeletal, cardiac cells
• Connective Tissue: Support the body– Bone, fat, tendons
• Epithelial: protection sheet of cells– skin, stomach lining
• Nerve Tissue: Transmit electric signals– Brain & Spinal Cord
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
• Ex: Thermoregulation
Negative Feedback Loop
Control system forces exhale and inhale
O2 / CO2 level returns to normal
Holding breath, CO2 levels rise
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)
– Ex:– Torn vessel stimulates release of clotting factors
– growth hormones stimulate cell division
platelets
fibrin
white blood cellred blood cell
blood vessel
clot
Positive Feedback Loop
Homeostasis disruption
• Sensors fail• Wrong messages sent• Message doesn’t reach
target• Serious injury• Microorganism infection• Short Term– Temporary discomfort
(usually)– Ex: cold or flu
Long Term: Diabetes• Normal
– Insulin controls glucose level– High: cells intake more
glucose– Low: pancreas creates more
glucose• Type 1
– Immune system destroys cells to produce insulin
– Pancreas fails– Blood pH decreases (more
acidic)• Type 2
– Insulin production decreases– Glucose level in blood rises– Cells starve