TEAS Version 7 Science Section

A patient sustains damage to a nerve that controls involuntary intestinal movement. Which nervous-system classification correctly identifies the damaged structure? A. Somatic division of the central nervous system B. Autonomic division of the peripheral nervous system C. Sensory division of the central nervous system D. Cerebral division of the peripheral nervous system Correct Answer: B. Autonomic division of the peripheral nervous system Rationale: The autonomic nervous system is a division of the peripheral nervous system that regulates involuntary functions, including digestion, heart rate, and glandular activity. The somatic division primarily controls voluntary skeletal muscle. The brain and spinal cord form the central nervous system, whereas cerebral and sensory divisions are not classified as presented in the distractors. Question 2: A diagnostic scan reveals lesions affecting both the brain and spinal cord. Which major division of the nervous system is involved? A. Peripheral nervous system B. Somatic nervous system C. Central nervous system D. Autonomic nervous system Correct Answer: C. Central nervous system Rationale: The central nervous system consists of the brain and spinal cord. The peripheral nervous system includes nerves and ganglia outside these structures. The somatic and autonomic systems are subdivisions of the peripheral nervous system and transmit information between the central nervous system and the rest of the body. Question 3: A student is asked to identify the two principal functional divisions of the peripheral nervous system. Which response is correct? A. Brain and spinal cord B. Sensory and cerebral C. Somatic and autonomic D. Sympathetic and central Correct Answer: C. Somatic and autonomic Rationale: The peripheral nervous system is divided into the somatic nervous system, which primarily controls voluntary skeletal muscle, and the autonomic nervous system, which regulates involuntary functions. The brain and spinal cord comprise the central nervous system. Sympathetic activity is only one subdivision of the autonomic nervous system. Question 4: A patient touches a hot surface and sensory impulses travel toward the spinal cord before a motor response activates the arm muscles. Which pairing is correct? A. Sensory neurons are efferent, and motor neurons are afferent B. Sensory neurons are afferent, and motor neurons are efferent C. Both sensory and motor neurons are afferent D. Both sensory and motor neurons are efferent Correct Answer: B. Sensory neurons are afferent, and motor neurons are efferent Rationale: Afferent sensory neurons carry information toward the brain and spinal cord. Efferent motor neurons transmit commands away from the central nervous system to muscles or glands. Reversing these terms would incorrectly describe the direction of information flow during reflexes and other nervous-system responses. Question 5: A neurological disorder damages the myelin surrounding peripheral axons. Which functional change is most likely? A. Faster synthesis of neurotransmitters B. Slower or disrupted action-potential conduction C. Increased production of neuronal organelles D. Permanent opening of calcium channels Correct Answer: B. Slower or disrupted action-potential conduction Rationale: Myelin electrically insulates axons and permits rapid saltatory conduction between nodes of Ranvier. Damage to myelin slows or interrupts action-potential propagation. Myelin does not produce neurotransmitters, manufacture organelles, or permanently regulate calcium channels. Those functions involve neuronal cell bodies, synapses, and membrane proteins. Question 6: Why do impulses normally travel faster through a myelinated axon than through an unmyelinated axon? A. Neurotransmitters move directly through the myelin B. Action potentials jump between nodes of Ranvier C. The entire axon depolarizes simultaneously D. Myelin increases the diameter of the cell body Correct Answer: B. Action potentials jump between nodes of Ranvier Rationale: Saltatory conduction allows action potentials to appear to jump from one node of Ranvier to the next, greatly increasing conduction speed. Unmyelinated axons use continuous conduction along the entire membrane. Neurotransmitters act at synapses, and the increased speed is not caused by changes in cell-body diameter. Question 7: A presynaptic neuron releases several impulses in rapid succession. The resulting graded potentials combine and trigger an action potential in the postsynaptic neuron. What process occurred? A. Spatial summation B. Temporal summation C. Saltatory conduction D. Continuous conduction Correct Answer: B. Temporal summation Rationale: Temporal summation occurs when repeated signals from one presynaptic source arrive rapidly enough for their effects to accumulate. Spatial summation involves signals arriving from several different sources at approximately the same time. Saltatory and continuous conduction describe action-potential movement along axons rather than integration at the postsynaptic membrane. Question 8: Several presynaptic neurons simultaneously release neurotransmitters onto one postsynaptic neuron, and their combined effects trigger an action potential. Which mechanism is responsible? A. Spatial summation B. Temporal summation C. Repolarization D. Saltatory conduction Correct Answer: A. Spatial summation Rationale: Spatial summation combines graded potentials generated by multiple presynaptic neurons at different locations on the postsynaptic cell. Temporal summation results from rapid repeated stimulation by one source. Repolarization restores membrane potential after depolarization, while saltatory conduction occurs along myelinated axons. Question 9: A neurotoxin selectively prevents the terminal end of an axon from functioning. Which process would be most directly impaired? A. Reception of most incoming neuronal signals B. Release of neurotransmitters into the synapse C. Performance of cellular metabolic activities D. Formation of the neuron’s nucleus Correct Answer: B. Release of neurotransmitters into the synapse Rationale: Axon terminals contain vesicles that release neurotransmitters into synaptic spaces. Dendrites primarily receive incoming signals, while the cell body contains the nucleus and organelles responsible for metabolism. Damage to the axon terminal therefore most directly interferes with communication to the next cell. Question 10: A patient can generate normal muscle strength but has an unsteady gait, poor balance, and difficulty coordinating intentional movements. Which brain region is most likely affected? A. Cerebellum B. Occipital lobe C. Temporal lobe D. Hypothalamus Correct Answer: A. Cerebellum Rationale: The cerebellum coordinates movement, posture, muscle tone, and balance. Cerebellar injury commonly causes ataxia and impaired coordination despite preserved muscle strength. The occipital lobe processes vision, the temporal lobe contributes to hearing and memory, and the hypothalamus regulates homeostasis and endocrine activity.