1. Examples

2. 1

3. 2

4. 3

5. 4

6. 5

7. 6

8. Thinkables: Complete sentences.
Obviously the way a cell looks is different depending on the function. Do you think a cell will have differences in organelles depending on the function of that cell? Explain your answer. What organelle(s) would muscle cells need a lot of?
All cells have a phospholipid bilayer as a cell membrane. Thinking about the variety of shapes and sizes of cells what can you conclude about the cell membrane?
True/False: The nucleus of a cell contains different types of DNA depending on the structure and function of the cell for that organism. Explain your answer.
How/Where do you get the different cells in your body?

9. Practice Questions
1. Muscle cells found in the heart contain many more mitochondria than cells that store fat in adult humans. Which explanation best explains why that is true?
a. Heart muscle cells are larger than fat cells.
b. Heart muscle cells require a lot of energy.
c. Cells that compose fatty tissue are not living.
d. Cells that compose fat tissue do not make proteins.

10. 2. If most of an organism’s cells have the same DNA, why is it true that all cells do not make the same proteins?
because of chromosome pairing
because of DNA mutation
c. because of differentiated ribosomes
d. because of gene (DNA) regulation

11. 3. Each body cell in a human contains the same DNA, but heart cells and liver cells have different functions. Why is this true?
a. Heart tissue develops before liver tissue.
b. Liver tissue develops before heart tissue.
c. When heart cells divide, mutations occur.
Heart cells express different genes than liver
cells.

12. #4 Stem Cell Video & Questions

13. Are sperm and egg stem cells
Are sperm and egg stem cells? Circle the cells that are undifferentiated stem cells.

15. Part 2: Neurons
Drawing, Video and Questions

16. Dendrites Cell body Axon Information flow through neurons
Figure 45-3
Information flow through neurons
Neurons form networks for information flow
Nucleus
Dendrites
Collect
electrical
signals
Cell body
Integrates incoming signals
and generates outgoing
signal to axon
Axon
Passes electrical signals
to dendrites of another
cell or to an effector cell

17. Impulse Transmission
Chemical changes across the membranes of neurons transmit the impulse.
An unstimulated neuron is polarized. Pumps in the membrane maintain this gradient.
Overall, the inside of the cell is negative b/c of a large number of very negatively charged molecules and ions inside the cell.
RESTING POTENTIAL/REST PHASE

18. Instrument records voltage across membrane Outside of cell
Figure 45-4
Instrument
records voltage
across membrane
Outside of cell
Microelectrode
0 mV
K channel
– 65 mV
Inside of cell

19. The Impulse
In response to a stimulus, gated ion channels open and allow Na+ to rush into the cell, meaning that the cell depolarizes. REQUIRES NO ENERGY!!!
If the impulse is strong enough more ion channels open.
Other channels open to allow K+ outside of the cell to repolarize the cell (turn off the signal).
An impulse moves along the neuron by opening and closing channels.

20. PROPAGATION OF ACTION POTENTIAL
Figure 45-11
PROPAGATION OF ACTION POTENTIAL
Axon
Neuron
Action potential spreads as a wave of depolarization.
Electrode A
Electrode B
Electrode C
1. Na+ enters axon.
Neuron A B
2. Charge spreads;
membrane
“downstream”
depolarizes. C
Depolarization at
next ion channel
3. Voltage-gated
channel opens in
response to
depolarization.

21. 1. As charge spreads down 2. Charge spreads 3. In this way, electrical
Figure 45-12b
WHY ACTION POTENTIALS JUMP DOWN MYELINATED AXONS
Schwann cell
1. As charge spreads down
an axon, myelination (via
Schwann cells) prevents
ions from leaking out across
the plasma membrane.
Node of
Ranvier
2. Charge spreads
unimpeded until it reaches
an unmyelinated section of
the axon, called the node
of Ranvier, which is packed
with Na+ channels.
3. In this way, electrical
signals continue to jump
down the axon much faster
than they can move down
an unmyelinated cell.

22. Myelinzation
Some neurons are myelinized (covered with a sheath of Schwann cells), which insulate the nerve’s impulse
Breaks in this sheath are called nodes of Ranvier.

23. Refractory Period
The neuron cannot now respond to a new stimulus b/c K+ and Na+ are on the wrong sides of the membrane
Sodium/Potassium pumps must now reestablish resting potential so that the neuron can react to a new stimulus
REQUIRES ATP!

24. 3. Hyperpolarization phase
Figure 45-6
1. Depolarization
phase
2. Repolarization
phase
Threshold potential
Resting potential
3. Hyperpolarization phase

25. At the Synapse (electrical changes to chemical):
Figure 45-15
At the Synapse (electrical changes to chemical):
ACTION POTENTIAL TRIGGERS RELEASE OF NEUROTRANSMITTER
Na+ and K+
channels
1. Action potential arrives;
triggers entry of Ca2+.
Action
potentials
Presynaptic
neuron
Presynaptic
membrane
(axon)
2. In response to Ca2+, synaptic
vesicles fuse with presynaptic
membrane, then release
neurotransmitter.
3. Ion channels open when
neurotransmitter binds; ion
flows cause change in
postsynaptic cell potential.
Postsynaptic
membrane
(dendrite or
cell body)
Postsynaptic
neuron
4. Ion channels will close as
neurotransmitter is broken
down or taken back up by
presynaptic cell (not shown).
Synaptic
cleft