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AP Biology Chapter 48 Guided Reading Assignment

1. What is a nerve net?

This is a characteristic of radially symmetrical animals; for example, hydra.


2. Compare and contrast the central and peripheral nervous systems. CNS- the brain and spinal cord; longitudinal nerve cords.

. CNS PNS
3. How does the organization of the nervous system of a _ compare with the organization of the nervous system of a ?

a. Hydra and insect

Insect: Has a brain and ventral nerve cords with segmentally arranged clusters of neurons.
HYDRA INSECT

b. Hydra and flatworm

Flatworm: Has a small brain with longitudinal nerve cords.
HYDRA FLATWORM

c. Leech and salamande

Salamander: Has a brain and spinal cord, and nerves and ganglia which are part of the peripheral nervous system.
LEECH SALAMANDER

4. What are the functions of the following:

d. Effector cells- A muscle or gland cell that responds to signals from the brain or other processing centers of the nervous system.


5. Why is it advantageous for the reflex response to circumvent instructions from the brain? Why might it be disadvantageous? ==== It is advantageous because it is quicker, we can move immediately without thinking or using our brain. If we didn't have this response, the reaction would take longer, and more harm would be done to your body. However, this can also be disadvantageous because you may have a response to something you don't want to, or something that is not harmful. Also, this could be a disadvantage because in some cause, processing from the brain may be necessary to prevent harm, according to the situation. ====

6. Describe the path of a nerve signal below.

7. Why are glial cells important?

8. What are astrocytes?

9. What is the blood brain barrier and why is it important?

10. Explain why myelin is important in nerve conduction?

11. Define the following terms: a. Membrane pot

ential

b. Resting potential

12. Discuss the three types of gated ion channels below: a. Stretch

b. Ligand

c. Voltage

13. Define the following terms: a. Hyperpolarization - increase in magnitude of membrane potential where the inside of the cell becomes more negative. This happens because the potassium channels open, the potential should approach -92 mV at 37 degrees C.

b. Depolarization - decrease in membrane potential where the inside of the cell becomes less negative because sodium channels open. The potential should approach +62 mV.

c. Graded potential- magnitude of hyperpolarization and depolarization varies with the strength of the stimulus. The increase in stimulus will cause an increase in the change of potential.

d. Threshold - certain membrane voltage which is the max for depolarization.

e. Action potential - when a stimulus is strong enough to produce a depolarization which reaches the threshold to produce an action potential. Once triggered, the response is "all or none" and the magnitude is independent of the strength of the stimulus. These are signals that carry information across axons, usually very brief and high frequency.

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14. Use the diagram to describe the generation of an action potential. 1. activation gates on Sodium & Potassium channels are closed & resting potential is maintained 2. Stimulus opens activation gates on Sodium channel --> increase of sodium conc within the cell --> depolarizes --> can trigger action potential if it passes the threshold 3. depolarization occurs while the potassium channels remain closed--> makes the cell more positive than outside of cell 4. inactivation gates on the sodium channel to close --> decreasing sodium concentration; potassium gates open, allowing potassium to enter the cell--> the inside of the cell becomes more negative 5. Sodium gate closed, potassium gate still open--> eventually potassium gates close and the sodium channels open and the cell returns to its resting state.

15. How do the various factors affect the speed of an action potential? a. Larger axon The wider in diameter the axon is, the faster the conduction will occur. This is because of the resistance to the flow of the electrical current is inversely proportional to the cross-sectional area of a conductor so in other words, it would provide less resistance to the depolarizing current. b. Myelination and salutatory conduction It would speed up the action potential since the extracellular fluid is in contact with the axon membrane only at the nodes causing the action potential to "jump" along the axon from node to node. media type="youtube" key="OzcNLSpOG5A" height="360" width="640"

16. Use the diagram below to describe the conduction of the action potential.

17. What happens at the synaptic cleft?

=
Action potential depolarizes the plasma membrane of the synaptic terminal. It then opens voltage-gated Ca^2+ channels in the membrane, triggering an influx of Ca^2+. The elevated Ca^2+concentration in the terminal causes synaptic vesicles to fuse with the presynaptic membrane. The vesicles release neurotransmitter in the synaptic cleft. The neurotransmitter binds to the receptor portion of ligand-gated ion channels in the postsynaptic membrane, opening the channels. The neurotransmitter releases from the receptors, and the channels close. Synaptic transmission ends when the neurotransmitter diffuses out of the synaptic cleft, is taken up by the synaptic terminal or another cell, or is degraded by an enzyme. =====

[[image:http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Synapse.gif]] [[image:http://click4biology.info/c4b/6/images/6.5/synapse.gif]] media type="custom" key="21843456"
18. Contrast excitatory and inhibitory postsynaptic potentials.

EPSPs - neurotransmitter binds to channel which sodium and potassium can diffuse from so postsynaptic membrane depolarizes and reaches threshold, producing action potential. IPSPs - neurotransmitter binds to open only potassium-selective channels to hyperpolarize the cell, so the membrane potential moves further from the threshold.



19. Contrast temporal and spatial summation.

temporal - 2 EPSPs happen in rapid succession at one synapse. The membrane potential cannot return to rest, so the effects of the EPSPs add together Spatial - EPSPs are effected nearly simultaneously by different synapses on same postsynaptic neuron and so add together --- also applies to IPSPs --- temporal and spatial together can create an action potential

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20. What happens when indirect synaptic transmission takes place? A neurotrasmitter binds to a receptor that isn't part of an ion channel which then activates a signal tranduction pathway that involves a second messenger.

21. Discuss the neurotransmitters listed below: ==== a. Acetylcholine: One of the most common neurotransmitters in both invertebrates and vertebrates; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane. It is released by motor neurons. It binds to receptors on ligand-gated channels in the muscle cell, producing an EPSP via direct synaptic transmission. ==== b. **Biogenic amines:** are neurotransmitters derived from amino acids. i. **Epinephrine and norepinephrine:** A catecholamie hormone secreted from the adrenal medulla that mediates "fight-or-flight" responses to short-term stress; also functions as a neurotransmitter. / Norepinephrine: a hormone that is chemically and functionally similar to epinephrine. ii. **Dopamine**: A biogenic amine closely related to epinephrine and norepinephrine. Released at many sites in the brain and affect sleep, mood, attention, and learning. iii. **Serotonin**: A biogenic amine synthesized from the amino acid tryptophan. It is also released at many sites in the brain and affect sleep, mood, attention, and learning. c. **GABA:** inhibitory, acts in CNS, increases the postsynaptic membrane's permeability to chlorine. d. ** Endorphins: ** natural analgesics (decrease pain perception), have emotional effects e. ** Nitrous oxide **

22. What is the difference between gray matter and white matter?

23. Define the following terms: a. Central nervous system

b. Peripheral nervous system

c. Somatic nervous system

d. Autonomic nervous system ​

24. Contrast the core functions of the parasympathetic and sympathetic nervous system.



25. What are the three brain region during embryonic development?

The three brain regions are the forebrain, midbrain, and the hindbrain.

26. What are the parts of the brainstem and what are its functions? The parts of the brainstem are the medulla oblangata in charge of visceral functions such as breathing, it is also made up of Pons which are in charge of regulating breathing in the medulla.



27. What is the reticular formation? The reticular formation is in charge of sleep and arousal, as well as a sensory filter.

28. What are the core functions of the cerebellum The functions of the cerebellum are coordination, learning and remembering motor skill, error checking motions, and balance.

29. What are the parts of the diencephalons and what are its functions? The parts of the diencephalons are the epithalmas which includes the pineal gland and it produce cerebrospinal fluid, it also has the thalmus which is in charge of sensory info. It also has the hypothalmus which is in charge of a lot of hemeostatic processes such as hunger.

30. What are circadian rhythms? Circadian rhythms are daily routines or a biological clock such as sleeping. media type="youtube" key="aF24ZmPwzb0" height="315" width="420"

31. Describe the cerebral hemispheres.

An outer covering of gray matter, the cerebral cortex, internal white matter, and a group of neurons called basal nuclei, which are important in planning and learning movement sequences.

32. What is the corpus callosum? A thick band of axons that allows communication between the two cerebral hemispheres.

33. What is the limbic system and what is its function? A ring of structures around the brain stem, which include the amygdala, the hyppocampus, and the olfactory bulb. It controls primary emotions such as aggression, sexuality, and feeding. It controls emotional bonding.


 * Skim ahead to Ch 49 and try to answer these: **

34. Explain how the nervous system produces graded contractions of whole muscles.

35. Labeling the diagram below, explain how a muscle contraction is controlled.