chapter 43 hw bio 112 sp 17

Match each brain structure to its function.

1. Memory; emotion Hippocampus 2. Motor control Basal ganglia 3. Coordination of movements; balance Cerebellum 4. Reflexes involving eyes and ears Midbrain 5. Sensory nuclei Medulla oblongata 6. Relay station for ascending and descending motor tracts Thalamus 7. Neuroendocrine control Hypothalamus 8. Connects and relays information between the two hemispheres Corpus callosum 9. Cognitive functions; interprets sensory input and organizes motor output Cerebral cortex

Put the steps required for production of an action potential in the correct order

1.stimulus moves voltage above threshold 2.voltage-gated sodium channels open 3. sodium enters the cell 4. cell depolarizes 5. voltage-gated sodium channels close and voltage-gated potassium channels open 6. potassium leaves the cell 7.cell hyperpolarizes 8. voltage-gated potassium channels close 9. sodium-potassium pump restores resting potential

In vertebrates, the ______ nervous system is composed of the brain and the spinal cord.

central

You are watching your neighbor's chihuahua puppy. Your cat walks into the room and suddenly freezes. His fur stands on end, his tail puffs out, and he hisses and bares his teeth. What division of the nervous system is responsible for his reaction?

sympathetic nervous system

The initial charge outside the axon is positive.

true

How does the resting potential of a typical neuron compare to that of a 1.5V AA alkaline battery?

A typical neuron has a resting potential of -70mV, or about 5% the voltage of the battery.

What else might her coworker add?

"How can you possibly see ions through a dissecting microscope?"

The scientist on your favorite sci-fi show peers into a microscope at a dissected alien brain. "Good grief!" she cries, "The alien's Na+/K+ pump is exchanging three sodium ions for two potassium ions!" How would her coworker reply?

"Well, that sounds pretty typical of human neurons. Maybe it's not an alien after all?"

Which figure correctly illustrates the mechanism of action of the sodium-potassium pump?

C

Which region of the CNS listed below is NOT correctly paired with its function?

Cerebellum—relay station for ascending and descending tracts

Why does repolarization occur?

K+ ions continue to diffuse out of the cell after the inactivation gates of voltage-gated Na+ ion channels close.

Why does depolarization occur?

More sodium ions diffuse into the cell than potassium ions diffuse out of it.

One of your patients has an autoimmune disease that seems to specifically attack the dorsal root ganglia. What symptom do you tell her to expect?

She will lose sensory perception, and may have difficulty walking due to lack of position feedback from the limbs.

When the membrane of an axon is at resting potential, which of the following is true?

The exterior of the cell has a net positive charge and the interior has a net negative charge.

When an action potential begins and sodium channels open, why does sodium rush into the cell? (Check all that apply.)

The inside of the cell is negatively charged. The diffusion gradient drives sodium into the cell.

Which area of the cerebral cortex is important for the formulation of thoughts into speech?

Wernicke's area

Which division of the nervous system regulates the activity of smooth muscle, cardiac muscle, and glands?

autonomic nervous system

Action potentials can travel in both directions on the axon.

false

What do the two sets of neurons damaged in Charcot-Marie-Tooth neuropathy comprise?

peripheral nervous system

Which of the following targets is NOT regulated by the autonomic nervous system?

skeletal muscles

True or false: If the post-synaptic membrane potential reaches a threshold level, an action potential will be produced.

true

Match the following definition or description with the correct type of cell.

1. A support cell of the CNS that produces the myelin sheath. Oligodendrocytes 2. Association neurons that enable complex reflexes and higher functions such as learning and memory. Interneurons 3. Afferent neurons that carry impulses from sensory receptors to the central nervous system. Sensory neurons 4. Efferent neurons that carry impulses from the central nervous system to muscles and glands. Motor neurons 5. A support cell of the peripheral nervous system that produces the myelin sheath. Schwann cells

Indicate whether the following statements regarding sensory and somatic neurons are true or false.

1. Somatic motor neurons stimulate skeletal muscles to contract. True 2. Motor axons from the dorsal surface of the spinal cord form the dorsal root. False 3. Motor axons from the ventral surface of the spinal cord form the ventral root. True 4. Sensory axon cell bodies are found in the dorsal root ganglia. True 5. Motor axon cell bodies are not found in the spinal cord. False

Match each neuroscience term to the appropriate definition.

1. This structure has fine branches that allow a neuron to receive inputs from multiple sources. Dendrite = Greek, "of a tree" 2. This refers to transmission of an action potential in a myelinated axon from each node of Ranvier to the next. Saltatory = Latin, "jumping" 3. This brain structure is black because it is laden with dopaminergic neurons, which have high levels of the black pigment melanin, a product of intermediates of dopamine synthesis. Damage to this structure causes the symptoms of Parkinson disease. Substantia nigra = Latin, "black substance" 4. This brain structure is curled up like the tail of a seahorse. It plays critical roles in memory formation. Hippocampus = Latin, "sea horse" 5. The brain's native versions of opiate drugs, which are known for their positive effects on mood, giving a sense of well-being. Endorphin = "endogenous morphine" 6. This small, round structure under the cortex plays important roles in motor control. Cerebellum = Latin, "little brain" 7. This structure wraps and protects the brain and spinal cord. Meninges = Latin, "membrane" 8. This division of the nervous system regulates body functions that are carried out without conscious thought. Autonomic = Greek and Latin, "having one's own laws"

If you wanted to use neuronal resting potential to power a device that requires one 1.5V AA battery, how many neurons would you need?

21

Identify the type of synapse found at the neuromuscular junction and the characteristics that define this type of synapse

Chemical synapse: synaptic vesicles, neurotransmitters, voltage-gated calcium channels.

Which diagnostic test(s) would you recommend for a patient that you suspect is showing signs of early stage Charcot-Marie-Tooth disease? (Check all that apply.)

EMG to test muscle responses Genetic testing for mutations in the PMP22 and MFN2 genes Nerve biopsy to look for signs of demyelination Nerve conduction study to test the rate of impulse conduction

Not every action potential is successfully transmitted to a postsynaptic neuron. Which of the following would increase the probability of the action potential transfer?

Frequent pre-synaptic action potentials resulting in greater calcium influx and neurotransmitter release.

Fictional detective Hercule Poirot liked to say "It is the brain, the little grey cells on which one must rely. One must seek the truth within - not without." Choose the TWO statements that explain the problems with this statement.

Grey matter contains neuronal cell bodies, but white matter contains the myelinated axons crucial for signaling between cells. Understanding the world requires conducting experiments and collecting data, not simply thinking about a problem.

What is the likely impact of this toxin on the resting potential of a neuron?

It will destroy the ion gradients necessary for the resting potential.

Nicotine binds to acetylcholine receptors at the synaptic cleft. Which is a likely effect of nicotine?

It will enable Na+ flux into the postsynaptic neuron in the absence of a presynaptic action potential.

Choose the two primary factors that contribute to the resting membrane potential of a neuron.

K+ leak channels make the cell membrane more permeable to K+. The sodium-potassium pump exports 3 Na+ from the cell for every 2 K+ it imports

Subsequent to motor neuron degeneration in Charcot-Marie-Tooth disease, muscles begin to weaken and degenerate as well. What is the likely cause?

Muscles will atrophy if they don't receive regular stimulation from motor neurons.

You are conducting an experiment to test the role of ATP in Na+/K+ pump function. What do you predict will happen when ATP is removed from the system?

Na+ ions will bind to the pump but its conformation will not change, and movement of Na+ and K+ ions against their concentration gradient will stop.

Upregulation of the same sodium channel is associated with disorders that cause severe pain. What can you conclude from this information?

Nav1.7 regulates the activity of pain-sensing neurons, and thus the perception of pain.

Tetrodotoxin, a toxin from pufferfish, blocks voltage-gated sodium channels. What happens to someone poisoned by tetrodotoxin?

Neurons cannot fire action potentials.

Which statement regarding the possible effects of addictive drugs on the nervous system is FALSE?

Nicotine binds directly to receptors on the presynaptic membrane.

Your roommate takes up smoking, and you hate it. Use what you know about nicotine to convince her to quit. (Check all statements that are true.)

Nicotine binds to a receptor in the brain that normally receives acetylcholine. The brain adapts to smoking by changing the levels of this receptor. Over time, more drug is required to get the same effect. Nicotine evolved to protect the tobacco plant by killing insects.

Damage to the substantia nigra, a specific region of the basal ganglia, can produce the resting muscle tremors characteristic of what disease?

Parkinson disease

A 2005 functional MRI (fMRI) study found that patients can be trained to reduce activity in the rostral anterior cingulate cortex (rACC), and diminish their perception of pain as a result. What does this finding illustrate?

Perception of pain requires both the peripheral nervous system and central nervous system.

The sodium-potassium pump moves ions across a cellular membrane. What conditions need to be met for a single cycle of Na+/K+ pump activity to occur?

Potassium outside the cell, sodium inside the cell, and ATP.

When the voltage gated ion channels open, both sodium and potassium ions cross the membrane but in opposite directions. What is the ultimate cause of this occurance?

Prior to the channels opening, a concentration gradient was established and now the ions move from high to low concentration.

Mutation of the peripheral myelin protein 22 (PMP22) gene, which causes demyelination of peripheral neurons, is a more common cause of Charcot-Marie-Tooth disease. In which cells is the PMP22 gene important for normal function?

Schwann cells

What other cells should you examine for effects from this mutant gene?

Schwann cells

Botulinum toxin, or "botox", has become popular for cosmetic surgery. The toxin prevents neurosecretory vesicles from docking at the plasma membrane and releasing neurotransmitter. How would this toxin affect the neuromuscular junction?

Since ACh is not released, the muscles are not activated to contract and remain relaxed.

How do somatic neurons and autonomic neurons differ? (Check all that apply.)

Somatic neurons control skeletal muscle, while autonomic neurons control smooth and cardiac muscle. Somatic neurons control their effectors directly, while autonomic neurons use a series of neurons. Somatic neurons are always excitatory, while autonomic neurons may be either excitatory or inhibitory.

"Synapses are connections between the axon of one neuron and the dendrite of another neuron, where neurotransmitters transmit a chemical signal." How would you modify this statement to make it more complete? (Check all that apply.)

Synapses can also form between an axon and a cell soma. Neuromuscular synapses form between the axon of a neuron and a muscle. Synapses can be electrical as well as chemical.

If K+ can exit the cell through leak channels, why don't they flow out until there are equal concentrations on both sides of the membrane?

The negative electrical potential inside the cell creates a force that holds the K+ ions in.

What conditions exist across a cell membrane due to action of the Na+/K+ pump?

There is a concentration gradient with more K+ in the intracellular space and more Na+ in the extracellular space.

Why are mammalian reflexes so fast? (Check all that apply.)

They complete the sensory input-to-motor output circuit in only 2-3 neurons. Incorrect They do not send signals to the brain and back There was a selective advantage to evolve rapid responses to certain types of stimuli.

In theory, gene replacement therapy could be developed to help treat victims of congenital pain insensitivity. Why are doctors reluctant to attempt such a therapy?

Unless they get the expression level exactly right, they could cause a severe pain disorder.

Where might Nav1.7 be expressed?

Where might Nav1.7 be expressed?

In the book Phantoms in the Brain, V. S. Ramachandran describes how he could "touch" the phantom limb of a patient by touching their face. He explained that neurons from the missing limb had crossed over into neighboring regions of the brain. Based on the somatosensory map above, do you predict that the patient had a phantom arm or leg?

arm

In motor neurons, action potentials would result from neural signals received by the ___________, which would travel down __________ in order to stimulate ___________.

dendrites, axons, muscle cells

Choose the correct terms to complete the following paragraph. A nerve separates into sensory and motor components at the spinal cord. Sensory axons enter the dorsal spinal cord to form the _______ of the spinal nerve, whereas motor axons exit from the ventral spinal cord to form the _______. Outside the spinal cord, the cell bodies of sensory neurons group together to form the _______.

dorsal root/ventral root/dorsal root ganglia

The action of the sodium-potassium pump is an example of passive transport.

false

What region of the brain integrates visceral activities, body temperature, and heartbeat?

hypothalamus

Choose the answer that correctly identifies the typical strategy used by invertebrates and vertebrates for rapid nerve conduction.

invertebrate = giant axons; vertebrate = myelination

Which of the following is an example of a monosynaptic reflex arc?

knee-jerk reflex

The hippocampus, amygdala, and hypothalamus are the major components of the ______ system

limbic

In a cartoon posted on your instructor's door, a Schwann cell says to a motor neuron, "You take me for granted! You only want me for my ____________________."

membranes

Nerve impulses are electrical signals measured across which structure?

plasma membrane of neuron

A cheetah is chasing a gazelle. What division of the vertebrate nervous system is regulating the stress response in both animals?

sympathetic nervous system

Choose the answer that lists the steps involved in the depolarization of a neuron during an action potential in the correct order. 1. Action potential stimulus. 2. Active transport of sodium and potassium ions. 3. Inactivation gates close. 4. Movement of potassium ions out of the cell. 5. Movement of sodium ions into the cell. 6. Opening of potassium channels. 7. Opening of sodium activation gates.

1, 7, 5

If a pump converts 8 ATP molecules to ADP and Pi, how many Na+ and K+ ions are transported across the membrane?

24 Na+ and 16 K+

Use the terms below to complete each statement describing the events involved in an action potential. Then place the statements in the correct orde

At resting potential, voltage-gated ion channels are closed, but there is some diffusion of K+. In response to a stimulus, the cell begins to depolarize. When the threshold voltage is reached, an action potential is produced. Rapid depolarization occurs because voltage-gated Na+ channel activation gates open, allowing the ion to diffuse into the axon. At the top of the spike, Na+inactivation gates close, and voltage-gated potassium channels begin to open. With K+ channels open, repolarization occurs. As K+ diffuses out of the axon, an undershoot occurs before the resting potential is restored.

During an action potential, the relative charge across the membrane of an axon is reversed. Which ion makes the largest contribution to this change in potential, and in what direction does the ion move?

Na+ moves into the cell, causing the intracellular space to become positive and the extracellular space to become negative.

As maximum depolarization approaches, the sodium ion channels close. If you could experimentally prevent the ion channels from closing, what would be an expected response?

The resting membrane potential would not be reestablished.

If sympathetic and parasympathetic neurons both release acetylcholine (ACh), how can they have antagonistic effects? (Check all that apply.)

The target cells of each set of neurons respond differently to the same signal. Sympathetic neurons activate the adrenal gland, causing secretion of epinephrine.

At myelinated areas of the axon (i.e. between nodes of Ranvier), which of the following statements is true?

There is increased resistance across the membrane.

You are studying a gene which, when mutant, causes oligodendrocytes to enwrap shorter sections of axon, so that nodes of Ranvier are more closely spaced. What is the likely effect on nerve impulses?

They will travel slower.

What is the likely impact of this toxin on action potentials?

Without ion gradients, action potentials are not possible.

A neuron that engages in spatial summation acquires a mutation that causes dendrite overgrowth and promiscuous synapsing. What is the likely outcome?

abnormally high frequency of action potentials

Which of the following structures is NOT a component of the hindbrain?

ascending tracts

Genetic studies have found that Charcot-Marie-Tooth may be caused by a mutation in the gene Mitofusin-2 (MFN2), which causes mitochondria to form large clumps. In what area of a neuron are these clumps most likely to cause a problem?

axon

What is the elongated extension of a neuron that nerve impulses travel along?

axon

Where do correlation, association, and learning occur in the brain?

cerebrum

What changes will the sympathetic nervous system of a rabbit initiate when the rabbit is being chased by a coyote? Check all that apply.

decrease motility in intestine dilate bronchioles in lungs dilate pupils secrete epinephrine speed up heartbeat

Which of the following are examples of biogenic amines?

epinephrine, norepinephrine, dopamine, and serotonin

In contrast to these toxins, strychnine acts postsynaptically, to block glycine from binding to receptors on motor neurons. Would you expect the symptoms of strychnine poisoning to be more similar to those of botulinum or tetanus toxin?

etanus toxin

When acetylcholine stimulates the opening of ligand-gated ion channels on a postsynaptic cell, what is this event called?

excitatory postsynaptic potential (EPSP)

Acetylcholine is actively transported from the pre-synaptic membrane to the post-synaptic membrane.

false

The doctor informs you that your grandmother's stroke has caused damage to Wernicke's area. Which activity is likely to become more difficult for her?

having a conversation

In early vertebrates, which component of the brain was devoted largely to coordinating motor reflexes?

hindbrain

You are an EMT on duty for the marathon. It is an extremely hot day. You say to your partner, "This weather is likely to _____________ the risk of hyponatremia, because ______________ will cause the athletes to lose ______________."

increase, sweating, sodium

What diffuses across the narrow synaptic cleft between the presynaptic axon and the postsynaptic cell to transmit a nerve impulse?

neurotransmitter

A cheetah has succeeded in catching a gazelle and has just finished feeding on the carcass. What division of the nervous system has increased in activity?

parasympathetic nervous system

You placate your cat with a bowl of his favorite treats, and he is now relaxing in a quiet room. What division of his nervous system has become more active?

parasympathetic nervous system

If you were to compare the resting potential of a neuron to a battery, which way is the battery oriented?

positive terminal outside of the cell, and negative terminal inside

Action potentials do not travel backwards because of the _________________ caused by __________________.

refractory period; voltage-gated sodium channel inactivation

You accidentally consume botulinum toxin by eating a contaminated can of sausages. What do you predict will be the most harmful physiological effect?

respiratory failure due to flaccid paralysis (relaxed muscles)

When neurons are not producing electrical signals, there is still a voltage difference across their membranes. What is this voltage called?

resting potential

What is the process in which impulses jump from node to node?

saltatory conduction

Marathon runners are encouraged to stop at water stations along the course to stay hydrated. However, occasionally a runner drinks too much water and suffers from hyponatremia, or "water intoxication". While water itself is not toxic, drinking too much can upset ion balance in the extracellular space. Based on what you know about ions and nerve signaling, the levels of which important ion are most likely to be disrupted in hyponatremia?

sodium

A Hawaiian legend tells of a village that angered a shark god. In revenge, a "seaweed" began to grow in the tidepools that killed anyone who touched it. In fact, this "limu-make-o-Hana" -- a zoanthid cnidarian -- contains a palytoxin that locks the sodium-potassium pump open, allowing free flow of ions. If a villager suffers palytoxin poisoning, which way will the ions in his neurons flow?

sodium in, potassium out

Another toxin that also blocks neurotransmitter release is tetanus toxin; however, it primarily affects inhibitory interneurons of the spinal cord that negatively regulate motor neurons. Which would be symptoms of tetanus toxin poisoning?

spastic paralysis

How can mutations in different genes, functioning in different cells, lead to the same disease? From the following, choose the best responses to complete the sentences: "Physiological function requires that multiple cells work together. Various defects in different cells can impair function, leading to ___________ that are indistinguishable at the level of the whole organism. In Charcot-Marie-Tooth disease, motor nerve function can be impaired either by a problem within _______________ , or a problem in __________________ causing _______________."

symptoms; motor neurons; Schwann cells; demyelination

If a patient had lost the lower part of their arm, where might you be able to touch them to activate sensory processing for the phantom lower arm?

upper arm

as a house-warming gift, you receive a robot vacuum cleaner with four unique features: 1) a gadget to detect stair edges and other obstacles, 2) a motor to move it around the house, 3) a controller to allow you to program its responses, and 4) a "hunger" sensor to send it back to its charger when its battery is low. Your friends tease you for treating it like a pet. In your defense, you point out that it is surprisingly lifelike. What animal features are the robot's features analogous to?

1) sensory pathways, 2) somatic nervous system and muscles, 3) brain, and 4) hypothalamus

Choose the neurotransmitter that best fits each definition or description.

1. Crosses the synapse between a motor neuron and a muscle fiber to produce a muscle contraction. Acetylcholine (ACh) 2. Biogenic amine responsible for the "flight or fight" response of the sympathetic nervous system. Norepinephrine 3. Major inhibitory amino acid neurotransmitter that causes ligand-gated Cl- channels to open. GABA 4. Neurotransmitter involved in control of some body movement; excess levels are linked to schizophrenia. Dopamine 5. Neurotransmitter involved in regulation of sleep and implicated in various emotional states. Serotonin 6. Major excitatory neurotransmitter in the vertebrate nervous system. Glutamate

What is the basis of the typical -70mV resting potential in neurons? Rank the factors in order from most important to least important.

1.Ca+2 equilibrium potential 2.K+ equilibrium potential 4.Na+ equilibrium potential

Indicate whether the following statements regarding ions involved in nerve impulse transmission are true or false.

1.Sodium ion (Na+) concentration in the extracellular fluid is greater than in the intracellular fluid. True 2. Potassium ion (K+) concentration in the extracellular fluid is greater than in the intracellular fluid. False 3. Chloride (Cl-) concentration in the extracellular fluid is greater than in the intracellular fluid. True

Put the steps required for a simple reflex arc in the correct order.

1.stimulus 2.stretch receptor activated 3.sensory neuron fires 4.motor neuron activated 5.muscle contracts 6.limb moves