Take Home Exam: Nervous System

Answers must be typed and handed in on 5/31 in class. If you do not bring it in, you will take the exam in class.

I. Multiple Choice (1 pt)

1. From superficial to deep, the meninges occur in the ordera. dura mater, pia mater, arachnoid

b. dura mater, arachnoid, pia materc. pia mater, dura mater, arachnoidd. pia mater, arachnoid, dura matere. arachnoid, pia mater, dura mater

2. The representational hemisphere of the cerebrum would most likely control a. taking this testb. diagnosing a patient's disease

c. painting a pictured. giving a speeche. balancing your checkbook

3. The neural tube is formed by fusion of the neurala. mesodermb. crestsc. grooves

d. foldse. plates

4. The right and left cerebral hemispheres are joined mainly bya. the corpus callosum

b. the thalamusc. the ponsd. the corpora quadrigeminae. the corticopinal tracts

5. The brain center most concerned with emotion isa. the limbic system

b. the cerebrumc. the cerebellumd. the ponse. the midbrain

6. The ________ contains nuclei that regulate body temperature, food intake, and sexual responsea. thalamus

b. hypothalamusc. midbraind. ponse. medulla oblongata

7. The _______ contains nuclei that control coughing, sneezing, swallowing, and vomitinga. thalamusb. hypothalamusc. midbraind. pons

e. medulla oblongata

8. The cerebral cortex concerned with hearing is ina. the insulab. the occipital lobe

c. the temporal lobed. the parietal lobee. the frontal lobe

9. A bipolar neuron hasa. two axons arising from the soma

b. one axon and one dendrite arising from the somac. two axons and multiple dendrites arising from the somad. two dendrites arising from the somae. two somas

10, Nissl bodies are located in the ________ of a neuron.a. soma

b. dendritec. axon hillockd. synaptic knob

11. Sensory areas responsible for vision are in a. the insula

b. the occipital lobec. the temporal lobed. the parietal lobee. the frontal lobe

12. The area of the brain that is needed to understand the meaning of words isa. Broca's area

b. Wernicke's areac. premotor cortexd. primary motor cortex

13. An example of a neural tube defect isa. aphasia

b. anencephalyc. microencephalyd. agnosia

14, The ________ coordinates body movements and aids in learning motor skillsa. cerebrumb. cerebral cortex

c. cerebellumd. midbrain

15. The ________ filters and relays sensory informationa. hypothalamus

b. thalamusc. midbraind. pons

16. The myelin sheatha. transmits impulses from one neuron to anotherb. nourishes the neuronsc. insulates the synapses

d. insulates the axon

17. In a neuron, neurotransmitters are stored ina. the cell bodyb. vesicles within dendritesc. the cytoplasm of the nucleus

d. vesicles within axon terminals

18. The minimum level of local potential that produces a response is called a. decrementalb. graded

c. a thresholdd. a reflex

19. A football player exhibited the following symptoms after a third-quarter play in which he was injured:1. uncontrolled rhythmic contraction of skeletal muscles2. abnormally great tension in muscles

The injury probably involved what area of the brain?a. medulla oblongatab. basal gangliac. cerebral cortex

d. cerebellume. hypothalamus

20. The blood-brain barrier is formed bya. blood capillariesb. neurons

c. astrocytesd. oligodendritese. microglia

21. Cerebrospinal fluid is secreted bya. neuronsb. astrocytes

c. ependymal cellsd. oligodendrocytese. microglia

22. Phineas Gage severely injured what part of his brain?a. parietal lobeb. temporal lobe

c. frontal lobed. occipital lobe

23. The glial cells that destroy microorganisms in the CNS area. microglia

b. satellite cellsc. ependymal cellsd. oligodendrocytese. astrocytes

24.The part of the brain affected in Parkinson’s Disease isa. amygdalab. hippocampus

c. substantia nigrad. hypothalamus

Multiple Choice

1b 7e 13b 19d2c 8c 14c 20c3d 9b 15a 21c4a 10a 16d 22c5a 11b 17d 23a6b 12b 18c 24c

II. Short Answer (3 pts): Answer 2/3 or all 3 for extra credit

25. A 77-year-old woman was cooking in the kitchen when she collapsed onto the floor. Her daughter called an ambulance and the woman was taken to the emergency room. She had suffered a stroke, and slowly regained consciousness over the next two days. However, when she woke up, she had the following signs and symptoms:

- paralysis of the right face and arm- loss of sensation to touch on the skin of the right face and arm - inability to answer questions but ability to understand what was said to her - ability to write down her thoughts more easily than to speak them

A. Why was she paralyzed in the right face and arm? B. What is the name of her language disorder, and what area of the brain was affected?C. Compare the two types of strokes and their treatments.

The stroke deprived oxygenated blood from several areas of her brain. Paralysis of right face and arm, and the loss of sensation to touch on her right arm and side of face, suggests damage to certain motor centers of her left frontal cerebrum (nerve pathways from left side of brain pass to right side of body) or thalamus, since nerve pathways for sensation and movement pass from the cerebrum through the thalamus to the respective areas of the body. Inability to answer questions yet the ability to understand speech points to a problem in formulating speech, and this nonfluent aphasia is a dysfunction of Broca’s area. Her ability to write down her thoughts (a function of Wernicke’s area) more easily than her ability to speak them is a further indication of damage to Broca’s area, rather than other language centers.

The woman could have suffered one of two types of strokes – ischemic stroke, which is caused by a blockage in an artery in the brain, and hemorrhagic stroke, which is caused by a ruptured blood vessel that increases cerebrospinal fluid pressure in the brain, impinging surround brain matter and causing problems appropriate to the trauma that is being suffered. The hemorrhage should fill up the nearby ventricle (third ventricle, judging from affected area) and cause radiating damage that increases over time as more blood flows in. Probability-wise, the woman most likely suffered an ischemic stroke, which accounts for 88 percent of all strokes, and she would then have been treated with blood thinners like warfarin and antiplatelet medication like aspirin to dislodge the blockage that caused the stroke. If she did suffer a hemorrhagic stroke, the type of medication for ischemic stroke would act against the clotting that is necessary to stop bleeding; these strokes can be treated by repairing the rupture site, but often the body

does this itself and the patient is usually just monitored and treated for complications resulting from the stroke (such as brain inflammation).

26. Explain the biochemical/physiological basis of addiction. Include in your answer an explanation of the reward mechanism, neuroadaptation, and withdrawal. Be specific in describing the important neurotransmitters and parts of the brain involved.

The phenomenon of physiological addiction is due to increasing tolerance for a drug that is due to a combination of neuroadaptation and a modified reward process that makes a user abuse the chemical in order to still enjoy it. The brain has a reward system comprised of structures, such as the ventral tegmental area, extended amygdala and the nucleus accumbens, that affects how a person perceives the use of a chemical as pleasurable or undesirable. A modified reward process is one where the negative effects of a drug like alcohol (“hangovers, loss of memory, fights, violence and arrests”) are depreciated and the positive effects justify a naïve conception such as, “the more I drink, the better I feel.” Susceptibility to this kind of reward perception modification differs among people, and there is some evidence that tendency towards alcoholism is an inherited trait. Neuroadaptation forces the addict to abuse their drug since their brain chemistry adapts to the addict’s habit in order to bring back normal functioning. So, if a drug like alcohol enhances the effect of GABA (causing the depressant effect) and inhibits glutamate activity by occupying its receptors, more glutamate is released by the brain (it’s tricked into thinking that there isn’t enough glutamate to fill receptors) and GABA activity is decreased to weaken its depressant effect. When GABA is lessened, so is its inhibitory effect on dopamine. High dopamine levels (which have to be lessened too) causes pleasure, which is a nice “reward.” So, the person drinks more, both for the reward and to compensate for less GABA and higher glutamate, and tolerance builds while brain chemistry keeps adapting. Breaking this vicious cycle by quitting leads to withdrawal symptoms as the brain has to readapt to the condition before the addict was an addict. As GABA goes back to normal (fighting the effects of glutamate meanwhile), dopamine levels are less than normal, and the former addict experiences depression, tremors, nausea, sluggishness, even seizures. These are certain unrewarding states, and the person’s body wants to go back to its “normal” addicted state, which adds another level of power to addiction.

27. Describe how synaptic inputs are integrated by neurons. Include in your answer descriptions of the postsynaptic potentials, the types of summation, and the types of neural circuits

Neural synapses are the connections between neurons in a neural circuit. There are three types of synapses – axodendritic (axon to dendrite), axosomatic (axon to soma), and axoaxonic (axon to axon). Neurons communicate with neurons by neurotransmitters, released from vesicles on the transmitting axon terminal, which are collected on receptor sites of the receiving neuron to generate a postsynaptic electric potential i.e. a voltage. This action potential can activate voltage-gated calcium channels which will cause synaptic vesicles to transport neurotransmitters to the axon terminal for a repeat of the transmission process; however, different neurotransmitters have different electrical properties so they may have either an excitatory or inhibitory effect on neuronal activity. There are three types of synaptic neurotransmitter activities – excitatory cholinergic

(ACh), inhibitory GABA-ergic, and excitatory adrenergic. Excitatory cholinergic synapses release ACh which bind to receptors that trigger a release of sodium ions that create a negative electric potential at the synapse that at reaching -55mV (from normal-70mV, relative to environment) forces an action potential for target neuron; ACh can have an inhibitory effect on action potential for some neurons. An inhibitory GABA-ergic synapse releases GABA which opens chlorine ion channels instead and these hyperpolarize (further “negative-ize”) the synapses so that depolarization becomes more difficult and no action potential is created. An excitatory adrenergic synapse releases norepinephrine which binds to a G protein which binds to adenylate cyclase that converts ATP to cAMP. cAMP has multiple effects, which vary depending on cell, including the opening of ligand-regulated sodium ion gates that will generate an action potential, and activation or synthesis of enzymes to effect changes in metabolism. In the view of a computation, these three synaptic activities are different operations, and “the more synapses a neuron has the greater its information-processing capabilities.” Other neurotransmitters that create excitatory postsynaptic potentials are glutamate and aspartate, and inhibitory PSPs are generated by glycine in addition to GABA.

Synaptic summation refers to aggregation of PSPs, and a typical neuron requires 30 EPSPs to depolarize or fire (form an action potential). Since the typical EPSP is .5mV and lasts 20ms, summation can occur by temporal accumulation of EPSPs by a synapse from an axon within a determinedly short period of time, or by spatial accumulation of EPSPs by a synapse from multiple axon terminals. Spatial summation is essentially distributed computing, involving the input of relatively less hard-working axons to achieve the same effect as one very hard-working axon trying to generate an action potential.

There are several types of neural circuits. Diverging circuits involve an action potential of one neuron traveling across a successively greater and greater number of neurons. Converging circuits is the vice-versa, with several neuronal action potentials intersecting at one neuron. Reverberating circuits are made of two linear circuits, one traveling in one direction across neurons and another traveling the other way from one neuron at the end of the first circuit to the beginning of the first circuit so that the first circuit is replicated due to the influence of the second circuit. Parallel after-discharge circuits are like diverging circuits that turn into converging circuits i.e. the action potential diverges across several neurons then converges upon a neuron. The usefulness of parallel after-discharge circuits is that the action potential can exist even without the originating neuron firing, as the in-between neurons between divergence and convergence can continue the action potential. An example with a simple parallel after-discharge circuit made of four neurons (so 2 in-between) that fire at the same time will maintain the action potential for twice the amount of time as if the in-betweens didn’t exist.