Pathophysiology ch 34
The nurse witnesses a client go into cardiac arrest. If the nurse delays intervention, when will the death of brain cells begin?
4-6 minutes Explanation: Unconsciousness occurs almost simultaneously with cardiac arrest, and the death of brain cells begins within 4 to 6 minutes. Interruption of blood flow also leads to the accumulation of metabolic byproducts that are toxic to neural tissue. Page 825
A client has just begun to experience an ischemic stroke. The blood supply from the middle cerebral artery is being blocked by a large blood clot. How long before brain cells begin to die due to lack of ATP?
4 to 6 minutes Explanation: Without oxygen, brain cells continue to function for approximately 10 seconds, and the death of brain cells begins within 4 to 6 minutes. Twenty minutes is the time of cardiac cell death, and 3 hours is the window of time that thrombolytic medications can be safely used. Testing is done at each segmental level, or dermatome, moving upward along the body and neck from coccygeal segments through the high cervical levels to test the functional integrity of all the spinal nerves. Page 825
Which of the following are the main neurotransmitters of the autonomic nervous system (ANS)? Select all that apply.
Acetylcholine Epinephrine Norepinephrine Explanation: The main neurotransmitters of the ANS are acetylcholine and the catecholamines epinephrine and norepinephrine. Monoamine oxidase is found in the nerve endings to degrade catecholamines. Tyrosine is an amino acid that is a precursor to catecholamines. Page 827
A nurse educator is explaining basic neuroanatomy to a class of prospective nursing students. Which statement best conveys an aspect of the role of cerebrospinal fluid (CSF)?
CSF cushions the brain and provides a near-water medium for diffusion of nutrients. Explanation: In addition to providing a cushion for the CNS, CSF provides a medium that is 99% water in which nutrients, electrolytes, and wastes can be diffused. It is not centrally involved in the distribution of oxygen, plasma proteins, or blood cells. Page 844
A client has developed shock and the physician has instructed the nurse to begin the administration of intravenous dopamine. The nurse anticipates that the medication will:
Cause vasodilatation of the coronary blood vessels Explanation: Dopamine, which is an intermediate compound in the synthesis of norepinephrine, also acts as a neurotransmitter. It is the principal inhibitory transmitter of interconnecting neurons in the sympathetic ganglia. It also has vasodilator effects on renal, splanchnic, and coronary blood vessels when given intravenously and is sometimes used in the treatment of shock. Level of consciousness is not affected. Page 852
The cerebellum, separated from the cerebral hemispheres by the tentorium cerebelli, lies in the posterior fossa of the cranium. What is one of the functions of the cerebellum?
Coordinates smooth and accurate movements of the body Explanation: The cerebellum compares what is actually happening with what is intended to happen. It then transmits the appropriate corrective signals back to the motor system, instructing it to increase or decrease the activity of the participating muscle groups so that smooth and accurate movements can be performed. Answer B describes the trigeminal nerve, which exits the brain stem. Answer C describes the pons. Answer D describes the midbrain. Page 840
The thalamus is located in which of the following parts of the brain?
Diencephalon Explanation: The dorsal horn of the diencephalon consists of the thalamus and the subthalamus. Page 840
Which one of the following meninges provides the major protection for the brain and spinal cord?
Dura mater Explanation: All surfaces of the spinal cord, brain, and segmental nerves are covered with a delicate connective tissue layer called the pia mater. A second, very delicate, nonvascular, and waterproof layer, called the arachnoid, encloses the entire central nervous system. Immediately outside the arachnoid is a continuous sheath of strong connective tissue, the dura mater, which provides the major protection for the brain and spinal cord. The tentorium cerebelli is the inner layer of the dura that anchors the brain to the skull. Page 844
A client has sustained damage to cranial nerve VIII. The nurse recognizes that the client may experience difficulty with:
Hearing Explanation: Cranial nerve VIII (vestibulocochlear nerve) is associated with hearing. The other options involve different nerves. Page 834
Maintenance of blood gas concentrations, water balance, and food consumption are controlled by which of the following parts of the brain?
Hypothalamus Explanation: The hypothalamus is the area of master level integration of homeostatic control of the body's internal environment. Maintenance of blood gas concentrations, water balance, food consumption, and major aspects of endocrine and autonomic nervous system control require hypothalamic function. Page 842
A 9 year-old girl has a diffuse collection of symptoms that are indicative of deficits in endocrine and autonomic nervous system control. She also suffers from persistent fluid and electrolyte imbalances. The nurse knows which of the following aspects of the nervous system listed below would her healthcare providers focus their diagnostic efforts?
Impaired function of her hypothalamus Explanation: The hypothalamus plays a central role in the maintenance of fluid and electrolyte balance and in the maintenance of endocrine control. Various cranial nerves, the hindbrain and the cerebellum would be less likely to be implicated. Page 850
Neurotransmitters are small molecules that exert their actions through specific proteins, called receptors, embedded in the postsynaptic membrane. Where are neurotransmitters synthesized?
In the axon terminal Explanation: Neurotransmitters are synthesized in the cytoplasm of the axon terminal. The other answers are incorrect. Page 826
The nurse is aware that the primary function of the sympathetic nervous system is:
Maintenance of vital functions and responding when there is a critical threat to the integrity of the individual Explanation: The sympathetic division maintains vital functions and responds when there is a critical threat to the integrity of the individual—the "fight-or-flight" response. The parasympathetic nervous system is concerned with conservation of energy, resource replenishment, and maintenance of organ function during periods of minimal activity. Page 848
A client with a diagnosis of depression has been prescribed a medication that ultimately increases the levels of the neurotransmitter serotonin between neurons. Which of the following processes will accompany the actions of the neurotransmitter in a chemical synapse?
More neurotransmitters will cross the synaptic cleft and bond with postsynaptic receptors. Explanation: In chemical synapses, neurotransmitters cross the synaptic cleft and bond with postsynaptic receptors to facilitate communication between neurons. This communication is one-way, not two-way, and each neuron has synaptic connections with thousands of other neurons. Gap junctions are associated with electrical synapses, not chemical synapses. Page 826
The nurse is providing care for a medical client who has a complex regimen of care. Normal function of the client's blood--brain barrier will have what implication for the client's health status?
Most of the drugs that are administered to the client will not reach the nervous tissue of the client's brain. Explanation: The blood-brain barrier prevents many drugs from entering the brain. Neuronal pathways do not exist between the blood and brain, and blood vessels do not carry nerves of the afferent and efferent pathways. The blood--brain barrier does not confer immunity from the consequences of fluid volume deficit. Page 845
The nursing student is caring for a client with a pheochomocytoma and is aware that the release of catecholamines induces the hypertensive state. Which catecholamines are responsible for this high blood pressure? Select all that apply.
Norepinephrine Epinephrine Dopamine Explanation: The catecholamines, which include norepinephrine, epinephrine, and dopamine, are synthesized in the axoplasm of sympathetic nerve terminal endings from the amino acid tyrosine. Epinephrine accounts for approximately 80% of the catecholamine released from the adrenal gland. Acetylcholine is excitatory to most muscarinic receptors. Serotonin is an important chemical neurotransmitter in the human body. It is commonly regarded as a chemical that is responsible for maintaining mood balance. Page 852
Spinal nerves that form complex nerve networks are called which of the following?
Plexuses Explanation: Spinal nerves do not go directly to skin and muscle fibers; instead, they form complicated nerve networks called plexuses. A plexus is a site of intermixing nerve branches. After emerging from the vertebral column, the spinal nerve divides into two branches, or rami. The choroid plexus produces cerebrospinal fluit in the lateral, third and fourth ventricles. Reticular formation is the location of many important reflex circuits of the spinal cord and brain stem. Page 839
When educating a patient about to undergo a pacemaker insertion, the nurse explains the normal phases of cardiac muscle tissue. During the repolarization phase, the nurse will stress that membranes must be repolarized before they can be re-excited. Within the cell, the nurse understands that:
Potassium channels open and while sodium channels close causing repolarization to the resting state. Explanation: Repolarization is the phase during which the polarity of the resting membrane potential is re-established. This occurs with the closure of the sodium channels and opening of the potassium channels. Page 826
There are two types of nervous tissue cells. One type is neurons, and the other type is the supporting cells. What is the function of the supporting cells?
Protect the nervous system and provide metabolic support for the neurons Explanation: The supporting cells, such as Schwann cells in the PNS and the neuroglial cells in the CNS, protect the nervous system and provide metabolic support for the neurons. The other answers are incorrect. Page 822
Which types of cells are supporting cells of the peripheral nervous system?
Schwann cells Explanation: The Schwann cells play an important role in supporting the peripheral nervous system. The other cells support the central nervous system. Page 823
Following a spinal cord injury suffered in a motor vehicle accident, a 22 year-old male has lost fine motor function of his finger and thumb, but is still able to perform gross motor movements of his hand and arm. Which of the following components of his white matter has most likely been damaged?
The outer layer (neolayer) Explanation: Fine manipulation skills are the domain of the outer, or neolayer, of the tract systems. The inner and middle layers and the reticular formation are not noted to be responsible for these functions. Page 836
A client comes to the emergency department stating she is having severe pain on the left side of her face. The client states that the pain started after being outdoors in the cold. The nurse observes lacrimation of the right eye. Which nerve does the nurse recognize is affected?
Trigeminal Explanation: The trigeminal nerve (CN V), which has both sensory and motor subdivisions, exits the brain stem laterally on the forward surface of the pons. The trigeminal is the main sensory nerve conveying the modalities of pain, temperature, touch, and proprioception to the superficial and deep regions of the face. Regions innervated include the skin of the anterior scalp and face, the conjunctiva and orbit, the meninges, the paranasal sinuses, and the mouth, including the teeth and the anterior two thirds of the tongue. Page 833
A client has experienced the α1-receptor stimulation. The nurse would assess the client for:
Vasoconstriction Explanation: The α1 receptors are primarily found in postsynaptic effector sites; they mediate responses in vascular smooth muscle. It causes vasoconstriction in many blood vessels, including those of the skin, gastrointestinal tract, kidney, and brain. Page 852
The student nurse has to evaluate the function of cranial nerve XII. Which techniques would indicate that the student nurse needs further practice in correctly assessing cranial nerve XII function? Select all that apply.
-Evaluate the client's ability to say "fa-la-la" 3 to 4 times quickly. -Observe for symmetry when the patient opens her mouth and says "ahhh." -Evaluate the patient ability to hear sound equally in both right and left ears. Explanation: Having the patient stick out her tongue and noting any deviation to one side or the other are the best assessment techniques to observe CN XII. The tongue will deviate towards the damaged or weakened side. The other assessments are not relevant to CN XII function. Page 834
What percentage of the body's oxygen does the brain consume?
20% Explanation: The brain receives 15% of the body's resting cardiac output and consumes 20% of its oxygen. Page 825
Neuromodulators can produce slower and longer-lasting changes in membrane excitability by acting on postsynaptic receptors. What do neuromodulators do?
Alter the release of or response to neurotransmitters Explanation: Neuromodulator molecules react with presynaptic or postsynaptic receptors to alter the release of or response to neurotransmitters. The other answers are incorrect. Page 829
Which are functions of the frontal lobe? Select all that apply.
Anticipation of consequences of behavior Prediction of consequences of behavior Explanation: The occipital lobe is associated with being able to experience color, motion, and depth perception. Behavior is anticipated by the frontal lobe. Page 842
The parasympathetic nervous system is part of which of the following systems?
Autonomic nervous system Explanation: The efferent outflow from the autonomic nervous system has two divisons: the sympathetic nervous system and the parasympathetic nervous system Page 847
Select the function of the occipital lobe.
Color, motion, and depth perception Explanation: The occipital lobe is associated with the ability to experience color, depth, and motion perception. The temporal lobe is responsible for behavior, and the parietal lobe helps us to determine objects through the sense of feel. Page 843
Cerebrospinal fluid (CSF) is produced by which of the following structures?
Choroid plexus Explanation: The CSF is produced by tiny reddish masses of specialized ependymal cells and capillaries, called the choroid plexus, which projects into the ventricles. The other options do not produce CSF. Page 844
The thick area of myelinated axons that connects the two sides of the cerebral cortex is known as which of the following components?
Corpus callosum Explanation: The thick area of myelinated axons that connects the two sides of the cerebral cortex is known as the corpus callosum. The remaining options are all components of the basal ganglia. Page 842
Which of the following types of synapse allows the quickest transmission from one neuron to another?
Electrical Explanation: Electrical synapses premit the passage of current-carrying ions through small openings called gap junctions. The gap junctions allow an action potential to pass directly and quickly from one neuron to another. Chemical synapses are the slowest component in progressive communication through a sequence of neurons. Chemical synapses are divided into two types: excitatory and inhibitory. Page 826
The adrenal medulla is innervated by parasympathetic nerve fibers.
False Explanation: The adrenal medulla is a modified prevertebral sympathetic ganglion. Page 850
A client is having an upper endoscopy to determine the presence of a gastric ulcer. After the procedure is performed, the nurse instructs the client that he cannot have anything to eat or drink until the return of the gag reflex. Which nerve is the nurse testing for return of function?
Glossopharyngeal Explanation: The glossopharyngeal nerve innervates the stylophargeus muscle, posterior external ear, taste buds of posterior half of tongue, oral pharynx, parotid gland, pharyngeal muscles, and the stylopharyngeus muscle. It affects the function of proprioception, somesthesia, taste, gag reflex, salivary reflex, and assists in swallowing. Page 834
Nutrition students are studying the nervous system, which has a high rate of metabolism. Which of the following is its major fuel source?
Glucose Explanation: Glucose is the major fuel source for the nervous system, but neurons have no provision for storing glucose. Ketones can provide for limited, temporary energy requirements; however, these resources are rapidly depleted. Page 825
The nurse measures a blood glucose level of 40 mg/dL for a client with diabetes type I. Why would it be important for the nurse to institute an intervention to elevate the glucose level in this client?
Glucose is not stored in the brain and is a major fuel source for brain function. Explanation: Glucose is the major fuel source for the nervous system but neurons have no provision for storing glucose. Ketones can provide for limited temporary energy requirements. However, these sources are rapidly depleted. Page 825
A client arrives in the clinic after having a tongue piercing performed and is unable to control the movement of the tongue. The nurse is aware that which nerve may have been damaged from the piercing?
Hypoglossal Explanation: The general somatic efferent LMNs of the lower segments of the medulla supply the extrinsic and intrinsic muscles of the tongue by means of the hypoglossal nerve (CN XII). Damage to the hypoglossal nerve results in weakness or paralysis of tongue muscles. When the tongue is protruded, it deviates toward the damaged and therefore weaker side because of the greater protrusion strength on the normal side. Page 834
When reviewing the purpose/action of neurotransmitters as they interact with different receptors, the nursing instructor gives an example using acetylcholine. When acetylcholine is released at the sinoatrial node in the right atrium of the heart, it is:
Inhibitory. Explanation: The action of a transmitter is determined by the type of receptor to which it binds. Acetylcholine is excitatory when it is released at a myoneural junction, and it is inhibitory when it is released at the sinoatrial node in the heart. Page 827
Neurons that connect sensory and motor neurons are known as which of the following?
Interneurons Explanation: Afferent (sensory) neurons transmit information to the central nervous system (CNS), whereas efferent (motor) neurons carry information away from the CNS. Interspersed between the afferent and efferent neurons is a network of interconnecting neurons (also called interneurons or internuncial neurons) that modulate and control the body's response to sensory input from the internal and external environments. Page 822
While assessing a critically ill patient in the emergency department, the nurse notes on the cardiac monitor an R-on-T premature ventricular beat which develops into ventricular tachycardia (VT). Immediately, the patient became unresponsive. The nurse knows that based on pathophysiologic principles, the most likely cause of the unresponsiveness is:
Interruption of the blood/oxygen supply to the brain. Explanation: The brain receives 15-20% of the total resting cardiac output and consumes 20% of its oxygen. The brain cannot store oxygen or engage in anaerobic metabolism. An interruption of blood supply or oxygen to the brain rapidly leads to clinically observable signs/symptoms. Unconsciousness occurs almost simultaneously with cardiac arrest. Metabolic acidosis will occur later in the cardiac arrest but not immediately and is not responsible for the patients unresponsiveness. CVAs can be caused by thrombosis formation or plaque occlusions, but is not the primary reason for unconsciousness in VT. Page 825
The health care provider is performing a spinal tap on a client with suspected infection. The provider would perform the procedure at:
L3 or L4 Explanation: A pocket of CSF, the dural cisterna spinalis, extends from approximately L2 to S2. Because this area contains an abundant supply of CSF and the spinal cord does not extend this far, the area often is used for sampling the CSF. A procedure called a spinal tap, or puncture, can be done by inserting a special needle into the dural sac at L3 or L4. The spinal roots, which are covered with pia mater, are in little danger of trauma from the needle used for this purpose. Page 838
Feelings of dread, high anxiety, or exquisite pleasure can be elicited by stimulation of areas in which of the following structures?
Limbic system Explanation: Stimulation of specific areas of the limbic system can lead to feelings of dread, high anxiety, or exquisite pleasure. The temporal lobe is involved with auditory functions, the cerebellum with proprioception, and the occipital lobe with visual function. Page 843
Which of the following is the primary component of white matter?
Myelinated fibers Explanation: Myelin has a high lipid content, which gives it a whitish color, and the name "white matter" is given to the masses of myelinated fibers in the spinal cord and brain. The other options are not myelinated. Page 835
During embryonic development, which of the following structures develops into the central nervous system (CNS)?
Neural tube Explanation: During embryonic development, the neural tube develops into the CNS, whereas the notochord becomes the foundation around which the vertebral column ultimately develops. As the neural tube closes, ectoderm cells called neural crest cells, migrate away from the dorsal surface of the neural tube to become progenitors of the neurons and supporting cells of the parasympathetic nervous system. The surface ectoderm separates from the neural tube and fuses over the top to become the outer layer of skin. Page 830
Neurotransmitters exert their actions through specific proteins that are known as:
Receptors Explanation: Neurotransmitters exert their actions through specific proteins that are known as called receptors, embedded in the postsynaptic membrane. Page 827
A 45 year old diabetic male is experiencing erectile dysfunction. If his erectile dysfunction is caused by the nervous system, then the nurse can educate the patient that the venous blood supply to the penis is controlled by:
Sacral parasympathetic fibers. Explanation: The pelvic nerves leave the sacral plexus on each side of the cord and distribute their peripheral fibers to the bladder, uterus, urethra, prostate, distal portion of the transverse colon, descending colon, and rectum. Sacral parasympathetic fibers also supply the venous outflow from the external genitalia to facilitate erectile function. The hypothalamus, vagus nerve, and postganglionic sympathetic neurons do not control erectile function. Page 850
A child is experiencing difficulty with chewing and swallowing. The nurse knows that which of the following cells may be innervating specialized gut-related receptors that provide taste and smell?
Special visceral afferent cells. Explanation: Special visceral afferent cells innervate specialized gut-related receptors. Their central processes communicate with special VIA column neurons that project to reflex circuits producing salivation, chewing, swallowing, and other responses. Special somatic afferent fibers are concerned with joint and tendon sensation. General somatic afferents respond to stimuli that produce pressure or pain. General visceral afferent neurons innervate visceral structures such as GI tract, urinary bladder, and the heart and great vessels. Page 833
Through what specific component do neurotransmitters exert their action?
Specific proteins Explanation: Neurotransmitters exert their actions through specific proteins, called receptors, embedded in the postsynaptic membrane. Water, carbon dioxide, and oxygen enter the brain with relative ease. Page 827
Neurons communicate with each other through which structure?
Synapses Explanation: Neurons communicate with each other through structures known as synapses. Cell bodies and dendrites are covered in synapses. Neural crest cells migrate aways from the forming neural tube and are progenitors to the parasympathetic nervous system. Page 826
Which of the following is the lobe of the brain with functions of perception, long-term memory, and recognition of auditory stimuli?
Temporal lobe Explanation: The temporal lobe is important in discrimination of sounds entering opposite ears. The superior temporal gyrus involves the auditory association or perception area. The remaining portions of the temporal cortex are apparently important in long-term memory recall. This is particularly true with respect to perception and memory of complex sensory patterns. The parietal lobe is necessary for somesthetic perception; the occipital is involved with the meaningfulness of visual experiences; and the frontal lobe is thought to be involved in anticipation and predictions of consequences of behavior. Page 842
A client asks the nurse if the brain is always receiving oxygen. The best response would be:
The brain receives 15% of the body's resting cardiac output and consumes 20% of its oxygen Page 825
During a clinical assessment of a 68 year-old client who has suffered a head injury, a neurologist suspects that a client has a sustained damage to her vagus (CN X). Which of the following assessment findings is most likely to lead the physician to this conclusion?
The client has difficulty swallowing and has had recent constipation and hypoactive bowel sounds. Explanation: Dysphagia and impaired GI motility are associated with damage to the vagus nerve. Lateral movement of the head is mediated by CN XI. Facial droop and dry eyes are associated with CN VII, the facial nerve, while abnormal tongue movement is a result of damage to CN XII., the hypoglossal nerve. Page 850
The nurse is performing a test to determine a client's neurological function related to a suspected lesion in the parietal lobe. What would the nurse determine is a normal finding after assessment?
The client is able to determine correctly that the item placed in his hand is a paper clip. Explanation: Localized lesions of the parietal lobe can result in the inability to recognize the meaningfulness of an object (a condition called agnosia). With the person's eyes closed, a screwdriver can be felt and described as to shape and texture. Nevertheless, the person cannot integrate the sensory information required to identify it as a screwdriver. Page 842
A client is being treated for the ingestion of a neurotoxin that interferes with the depolarization phase of action potentials. What physiologic process will be disrupted?
The inflow of sodium ions Explanation: Sodium ions rapidly exit the neuron during the depolarization phase of the action potential. Potassium ions do not leave the cell during this phase. Resting potential and the establishment of the refractory period do not occur during the depolarization phase. Page 826
The sympathetic and the parasympathetic nervous systems are continuously at work in our bodies. This continual action gives a basal activity to all parts of the body. What is this basal activity referred to as?
Tone Explanation: The sympathetic and parasympathetic nervous systems are continually active. The effect of this continual or basal (baseline) activity is referred to as tone. Page 847
The nurse teaches a client about a new diagnosis of astrocytoma. Which statement indicates an accurate understanding?
Treatment is hard since glial cells support neurons and blood vessels in the brain. Explanation: Astrocytes are the most common of four types of neuroglial cells. Astrocytes support neurons, wrap around blood vessels and form a sealed barrier to protect the central nervous system (CNS). Due to these characteristics, tumors of the glial cells are difficult to kill without profound impact on the client's CNS. Page 823
The vertebral column provides protection for the spinal cord, spinal nerves, and supporting structures.
True Page 838
The arachnoid membrane is the middle layer of the three meninges.
True Page 844
Ion channels in nervous system cells generate action potentials in the cells. What are the ion channels guarded by?
Voltage-dependent gates Explanation: These membrane channels are guarded by voltage-dependent gates that open and close with changes in the membrane potential. The other answers are incorrect. Page 825
A client asks the nurse when during embryonic growth the nervous system develops. The best response would be:
Week 3 Explanation: The nervous system appears very early in week 3 of embryonic development. The nervous system appears very early in embryonic development (22 to 23 days). This early development is essential because it influences the development and organization of many other body systems, including the axial skeleton, skeletal muscles, and sensory organs such as the eyes and ears. Page 830
Which of the following types of reflex is stimulated by a nociceptive stimulus?
Withdrawal reflex Explanation: The withdrawal reflex is stimulated by a damaging (nociceptive) stimulus. The myotatic, or stretch reflex, controls muscle tone and helps maintain posture. The carotid sinus baroreflex assists adjustment of the cardiovascular system at the level of the brain stem. Page 840
