Chapter 14: Nervous System Martin Caon Examination Questions and Answers in Basic Anatomy and Physiology Third Edition

Martin Caon Examination Questions and Answers in Basic Anatomy and Physiology Third Edition Chapter 14: Nervous System 14.1 Cells and Action Potential 1. Which word correctly completes the statement: “All motor neurons are…”? a. Interneurons b. Multipolar c. Bipolar d. Unipolar Answer is B: Motor neurones (that innervate muscles) are multipolar. 2. In the peripheral nervous system, which cells form the myelin sheath? a. Ependymal cells b. Schwann cells c. Astrocytes d. Oligodendrocytes Answer is B: Schwann cells surround the axon to form the myelin sheath in peripheral neurones. Oligodendrocytes perform a similar function for neurones in the CNS. 3. A difference in the amount and type of ions between the two sides of a plasma membrane or a charge difference that occurs when ions move along a membrane is called an “electrical potential”. What does the term “action potential” refer to? a. The distribution of ions that results in the inside of the cell being at about −70 mV compared to outside the cell b. A movement of sodium ions into the cell following a stimulus and the ions spreading out along the inside of the cell membrane c. The rapid movement of sodium ions into the cell followed by potassium ions moving out of the cell, with the movement being repeated along the length of the neuron d. Sodium ions being pumped out of the cell, while potassium ions are moved into the cell Answer is C: The influx of sodium ions followed by the efflux of potassium ions describes the action potential. Choice A describes the “resting potential”. 4. What is the gap between the plasma membranes of a neuron that conducts an incoming signal and the cell that is going to receive the signal called? a. Neuromuscular junction b. Intercellular cleft c. Synaptic cleft d. Intercalated disc Answer is C: The gap between cells at a synapse is called a synaptic cleft. A neuromuscular junction is one type of synapse. 5. Which of the following substances CANNOT pass through the “blood–brain barrier”? a. Steroid hormones b. O2 molecules c. Alcohol d. Potassium ions Answer is D: Fat-soluble molecules can pass the BBB, but most charged particles cannot. 6. What name is given to the cells in the nervous system that produce nerve impulses? a. Neurotransmitters b. Nerves c. Neurons d. Neuroglia Answer is C: Neurons produce nerve impulses, nerves are bundles of neurones. Neuroglia are cells that support and protect neurones. 7. Which structure carries incoming impulses towards the nerve cell body? a. Axon hillock b. Axon c. Dendrite d. Synaptic knobs Answer is C: Dendrites receive stimuli for nerve cells and transmit them towards the cell body. An axon transmits a nerve impulse away from the neurone cell body. 8. Which neurons are unipolar? a. Neurons in the central nervous system b. Neurons in the retina c. Sensory neurons d. Motor neurons Answer is C: Most sensory neurones are unipolar, that is the axon and dendrites are not separated by the cell body but are the one strand (are fused), with the cell body attached to it by a single process. 9. Which glial cells are responsible for forming the myelin sheath around peripheral nerve cells? a. Astrocytes b. Schwann cells c. Satellite cells d. Oligodendrocytes Answer is B: The oligodendrocytes perform a similar function for neurones within the CNS. 10. Inactive muscle and nerve cells maintain a resting membrane potential. This potential results in: a. The outside of the cell being negative b. The inside of the cell being positive c. The inside and outside of the cell having the same charge d. The inside of the cell being negative Answer is D: The resting potential has the inside of the cell at about −70 mV compared to the outside. 11. When an action potential arrives at a synapse, what happens first? a. A neurotransmitter is released into the synaptic cleft. b. Extracellular Na+ crosses the postsynaptic membrane. c. Choline in the synaptic cleft enters the nerve cell and is converted to acetyl choline. d. Extracellular Ca++ enters the nerve cell. Answer is D: As the axon terminal depolarises when the action potential arrives, calcium channels open and extracellular calcium enters the axon terminal. This stimulates the release of a neurotransmitter (e.g. ACh) into the synaptic cleft. 12. What is the last part of a nerve cell that is involved when a nerve impulse passes to another cell? a. Synaptic knob b. Axon hillock c. Dendrite d. Axon Answer is A: Synaptic knobs are at the distal end of an axon. The axon hillock is at the proximal end. 13. Which of the following statements is true of neuroglia? a. They are the cells that link motor neurons to sensory neurons. b. It is the non-cellular material that lies between neurons. c. They have only one dendrite and one axon. d. They produce the myelin sheath. Answer is D: Neuroglia refers to several types of cells of the nervous system that are not neurones. Some of them form the myelin sheath. 14. What can correctly be said about somatic motor neurons? a. They are unipolar neurons. b. Their cell bodies are in the dorsal root ganglia. c. Their cell bodies are located in the central nervous system. d. They are bipolar neurons. Answer is C: Somatic motor neurons are multipolar. Their cell bodies are located in the CNS—within the spinal cord. 15. What is the effect of the movement of Na+ into a nerve cell followed very soon by the movement of K+ out of the nerve cell? a. This establishes the resting membrane potential. b. These movements are known as depolarisation and repolarisation. c. These movements repolarise the cell. d. It changes the membrane potential from about −70 mV to about −50 mV. Answer is B: When Na+ moves into a nerve cell, the cell depolarises (from −70 mV to about +30 mV); when soon afterwards K+ moves out of the nerve cell, it repolarises (from +30 mV back to −70 mV). 16. There is a space between a neuron and the cell it stimulates, that is crossed by a neurotransmitter. What is it called? a. Synaptic cleft b. Voltage-gated channel c. Synapse d. Postsynaptic membrane Answer is A: The synaptic cleft lies between the presynaptic membrane of the neuron and the postsynaptic membrane of the cell about to be stimulated. 17. Which of the following CAN cross the blood–brain barrier to enter the brain? a. K+ b. O2 c. Proteins d. Most pharmaceuticals Answer is B: All cells require oxygen, so of course it can cross the BBB most pharmaceuticals cannot. 18. What name is used for a nerve cell? a. Neuron b. Neuroglia c. Ganglion d. Astrocyte Answer is A: Neurons (or neurones) are nerve cells. Neuroglia are cells in the nervous system, but they do not produce nerve impulses. 19. What is the name of the nerve cell structure that carries incoming impulses towards the cell? a. Dendrite b. Axon c. Cell body d. Ganglion Answer is A: Dendrites receive incoming (efferent or stimulating) impulses. 20. Which is the major type of nerve cell in the CNS? a. Anaxonic b. Unipolar c. Bipolar d. Multipolar Answer is D: Multipolar are most common in the CNS. Motor neurons, whose cell bodies lie within the spinal cord, are multipolar. 21. What is the purpose of the myelin sheath around an axon? a. To control the chemical environment around the nerve cell b. To phagocytose microbes c. To prevent movement of ions through the nerve cell membrane d. To form the blood–brain barrier Answer is C: The myelin sheath insulates the axon. That is, it prevents ions from crossing the plasma membrane except at the nodes of Ranvier, where the sheath is absent.