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AP Biology Chapter 48 Guided Reading Assignment

1. What is a nerve net? A nerve net is a webbed system of nuerons.

2. Compare and contrast the central and peripheral nervous systems. Peripheral - the nerves and ganglia outside of the brain and spinal cord

Central - brain and spinal cord

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 Hydras just have a large nerve net. Insects have a brain, ventral nerve cord, and sedmental ganglia. Insects are more complex. b. Hydra and flatworm Hydras, again, have a large nerve net. Flatworms have an eyespot, brain, nerve cord, and transverse nerus. c. Leech and salamander Leeches have a brain, ventral nerve cord, and sedmental ganglia. Salamanders have a brain, spinal cord, and sensory ganglion.

4. What are the functions of the following: a. __#|Sensory neurons__

b. Interneurons

c. Motor neurons

d. Effector cells

5. Why is it advantageous for the reflex response to circumvent instructions from the brain? Why might it be disadvantageous? ==== Reflex responses are quicker. Our actions are performed without using our brain. the reaction would take longer if the reflex response was absent. the response can also be disadvantageous if the person does not want to intentionally do something and may require some thought into the persons actions. ====



6. Describe the path of a nerve signal below.

An electrical impulse is generated by the cell body in the neuron. It travels down the axon and into the axon terminal. The impulse releases neurotransmitters from vesicles into the synapse and continues the impulse. Dendrites from another neuron accept the impulse and relays the message.



7. Why are glial cells important?

Glial cells are important for the structural integrity of the nervous system. They give neurons support and insulation. Astrocytes provide nutrients, support, and insulation for neurons of the CNS. Radial glia are a pivotal cell type in the developing central nervous system involved in key developmental processes. Oligodendroctes are a type of support cell in the brain that produces myelin, the fatty sheath that surrounds and insulates axons.Schwann cells are nerve cells in the peripheral nervous system that wrap around nerve fibers with myelin.



8. What are astrocytes? They are star-shaped glial cells that hold neurons in place, get nutrients to them, and digest parts of dead neurons. They have no action potential.

9. What is the blood brain barrier and why is it important? The development astrocytes induce the formation of tight junctions between cells and that lines the capillaries in the brain and spinal cord which creates the blood brain barrier. This is important because it restricts the passage of most substances into the CNS allowing the extracellular chemical environment of the CNS to be tightly controlled.

10. Explain why myelin is important in nerve conduction? It allows for a faster nerve impulses by allowing the impulses to jump from one myelin covering to another.

11. Define the following terms: a. Membrane potential is the difference in electrical potential between the interior and the exterior of a biological cell. The membrane potential arises primarily from the interaction between the membrane and the actions of two types of transmembrane proteins embedded in the plasma membrane

b. Resting potential the potential difference between the two sides of the membrane of a nerve cell when the cell is not conducting an impulse

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

ion channels which open their pores in response to mechanical deformation of a neuron's plasma membrane. Opening of the ion channels depolarizes the afferent neuron producing an action potential with sufficient depolarization

b. Ligand

c. Voltage

13. Define the following terms: a. Hyperpolarization Electrical state when inside of the cell is more negative relative to the outside than at the resting membrane potential. It is the opposite of depolarization. It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold.

b. Depolarization Electrical state in an excitable cell whereby the inside of the cell is made less negative. As stated above, depolarization is the opposite of hyperpolarization. In neurons and some other cells, a large enough depolarization may result in an action potential.

c.Graded potential- Local voltage change in a neuron membrane induced by stimulation of a neuron with a strength proportional to it.

d. Threshold Depolarization gradient measured in voltage e. Action potential - Stimulus enters that is strong enough to reach the threshold and start depolarization, signals then carry our information over axons flipping the charges of the membrane potential with Na+ and then balancing with Potassium.

14. Use the diagram to describe the generation of an action potential. 1-Resting state- The activation gates on the Na+ and K+ are closed, and the membrane's resting potential is maintained

2-Depolarization- A stimulus opens the activation gates on some Na+ channels. Na+ influx through those channels depolarizes the membrane

3-Rising phase of the action potential-Depolarization opens the activation gates on most Na+ channels while K+ channels activation remains closed. Na+ influx makes the inside of the membrane positive with respect to the outside

4-Falling phase of the action potential- The inactivation on most Na+ channels close, blocking Na+ influx. The activation gates on most K+ channels open, permitting K+ influx which again makes the inside of the cell negative

5-Undershoot- Both gates of the Na+ channels are closed, but the activation gates on some K+ channels are still open. As these gates close on most K+  channels, and the inactivation gates open on Na+ channels, the membrane returns to its resting state

15. How do the various factors affect the speed of an action potential? a. Larger axon- The larger (wider) the axon’s diameter, the faster the conduction. This is because resistance to the flow of electrical current is inversely proportional to the cross-sectional area of a conductor (such as a wire or an axon).

b. Myelination and salutatory conduction The rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of ranvier to another, skips the myelin-sheathed regions of membrane, this causes the the action potential to speed up.

16. Use the diagram below to describe the conduction of the action potential. The depolarization-repolarization process is repeated in the next region of the membrane. In this way, local currents of ions across the plasma membrane cause the action potential to be propagated along the length of the axon.

17. What happens at the synaptic cleft? The synaptic cleft is the area between an presynaptic neuron and a postsynaptic neuron. The distance is small and is measured in nanometers. It essentially allows a signal to travel from one neuron to another. At the synaptic cleft, the electrical signal is turned into a chemical signal. This chemical signal diffuses across the synaptic cleft until it reaches the other neuron. The other neuron turns the chemical signal back into an electrical one and the signal continues onto the next neuron. In greater detail: the action potential at the presynaptic neuron is an electrical message that travels to the axon terminal, where it there stimulates the release of stored neurotransmitters into the synaptic cleft. The neurotransmitters then bind to the receptor sites on the postsynaptic neuron.

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18. Contrast excitatory and inhibitory postsynaptic potentials. __excitatory (EPSP):__ an electrical change (depolarization) in the membrane of a postsynaptic neuron caused by the binding of an excitatory neurotransmitter from the presynaptic cell to a postsynaptic receptor making it more likely for a postsynaptic neuron to generate an action potential. __inhibitory (IPSP):__ an electrical charge (hyperpolarization) in the membrane of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from a presynaptic cell to a postsynaptic receptor makes it more difficult for a postsynaptic neuron to generate an action potential.

19. Contrast temporal and spatial summation. __temporal:__ a phenomenon of neural integration in which the membrane potential of the postsynamptic cell in a chemical synapse is determined by the combined effect of EPSPs or IPSPs produced in rapid succession __spatial:__ a phenomenon of neural integration in which the membrane potential of the postsynamptic cell is determined by the combined effect of EPSPs or IPSPs produced nearly simultaneously by different synapses

20. What happens when indirect synaptic transmission takes place? In an indirect synaptic transmission, a neurotransmitter binds to a receptor that is not part of an ion channel. This activates a signal transduction pathway involving a second messenger in the postsynaptic cell. The effects of indirect synaptic transmission have slower onsets but last longer (up to several minutes.)

21. Discuss the neurotransmitters listed below: a. __Acetylcholine:__ binds to receptors on ligang-gated channels in muscle cells, producing an EPSP via synaptic transmission b. __Biogenic amines:__ i. neurotransmitters produced from amino acids tyrosine, function as hormones ii. dopamine: excitatory, released in many parts of brain affect sleep, mood, attention, and learning

i. Epinephrine and norepinephrine ii. Dopamine iii. Serotonin c. GABA- produces IPSP's by increasing the permeability of postsynaptic membranes to Cl- d. Endorphins- natural analgesics, decreases pain perception e. Nitrous oxide- local regulator, also a neurotransmitter

22. What is the difference between gray matter and white matter? Contains dendrites and also has unmyelinated axons and neuron cell bodies



23. Define the following terms: a. Central nervous system- in invertebrate animals, the brain and spinal cord

b. Peripheral nervous system- Sensory and motor neurons that connect to CNS



c. Somatic nervous system- Carries signals to skeletal muscles in response to external stimuli

d. Autonomic nervous system- Regulates internal environment and consists of the sympathetic, parasympathetic and enteric divisions ​

24. Contrast the core functions of the parasympathetic and sympathetic nervous system. Parasympathetic division: constricts pupil of eye, stimulates salivary gland secretion, constricts bronchi in lungs, slows heart, stimulates activity of stomach and intestines, stimulates activity of pancreas, stimulates gallbladder, promotes emptying of bladder, and promotes erection of genitalia

Sympathetic division: Dilates pupil of eye, inhibits salivary gland secretion, relaxes bronchi in lungs, accelerates heart, inhibits activity of stomach and intestines, inhibits activity of pancreas, stimulates glucose release from liver, inhibits gallbladder, stimulates adrenal medulla, inhibits emptying of bladder, and promotes ejac ulation and vaginal contractions



 25. What are the three brain region during embryonic development? Forebrain, midbrain, and hindbrain

26. What are the parts of the brainstem and what are its functions? **Midbrain:** sensory integrating and relay centers that send sensory information to the cerebrum **Pons**: regulates breathing centers in Medulla **Medulla Oblongata**: contains centers that control several visceral functions such as breathing, heart and blood vessel activity, swallowing, vomiting, and digestion



27. What is the reticular formation? network of neurons containing over 90 separate clusters of cell bodies is present in the brainstem. It filters sensory input blocking familiar and repetitive information that constantly enters the nervous system. It sends the filtered input to the cerebral cortex.

28. What are the core functions of the cerebellum
 * coordination
 * error checking during motor, perceptual & cognitive functions
 * hand-eye coordination



29. What are the parts of the diencephalons and what are its functions?

**Epithalamus:** pineal gland and capillaries that produce cerebrospinal fluid from blood.

**Thalmus:** main input for sensory into going to cerebellum and output info from cerebellum

**Hypothalmus:** Homeostatic regulation, body's thermostat, centers of hunger, thirst, sexual and mating behaviors, "fight or flight", and pleasure

30. What are circadian rhythms? physiological cycle of about 24 hours that is present in all eukaryotic organisms & that persist even in the absence of external ones



31. Describe the cerebral hemispheres. corpus callosum connects the left & right hemispheres. The cortex; gray matter, covers each hemisphere. Each hemisphere also consists of internal white matter & basal nuclei, which is groups of neurons located deep within the white matter.



32. What is the corpus callosum? thick band of nerve fibers that connect the right & left cerebral hemispheres in placental mammals, enabling the hemispheres to process information together.

33. What is the limbic system and what is its function? Group of nuclei (clusters of nerve cell bodies) in the lower part of the mammalian forebrain that interacts with the cerebral cortex in determining emotions, includes the hippocampus and the amygdala.



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

34. Explain how the nervous system produces graded contractions of whole muscles. Muscle fibers contain 1 motor neuron each, and together they work as a network to synapse with multiple muscle fibers. The force of muscle contraction can be graded by changing the frequency of discharge in active motor units by changing the # of active motor units, resulting in forces graded between the tension of a twitch in the smallest motor unit to the tension of a fused tetanus in all motor units of the muscle.

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