Chapter 13 The Peripheral Nervous System Flashcards
1
Q
1) Which division detects stimuli of the general senses and special senses?
A) visceral motor division (autonomic nervous system)
B) somatic sensory division
C) visceral sensory division
D) somatic motor division
A
B) somatic sensory division
2
Q
2) You feel a mosquito land on your arm. This stimulus is carried to the central nervous system (CNS) by the:
A) somatic sensory division.
B) visceral sensory division.
C) visceral motor division (autonomic nervous system).
D) somatic motor division.
A
A) somatic sensory division.
3
Q
3) The sympathetic nervous system and parasympathetic nervous system are divisions of the:
A) somatic sensory division.
B) somatic motor division.
C) visceral sensory division.
D) visceral motor division (or autonomic nervous system, ANS).
A
D) visceral motor division (or autonomic nervous system, ANS).
4
Q
4) Which division of the peripheral nervous system (PNS) detects stimuli and carries them to the central nervous system (CNS)? A) sensory B) motor C) autonomic D) sympathetic
A
A) sensory
5
Q
5) What is the outermost connective tissue covering of a nerve? A) endoneurium B) perineurium C) epimysium D) epineurium
A
D) epineurium
6
Q
6) Mixed nerves house: A) sensory neurons only. B) motor neurons only. C) somatic neurons only. D) both sensory and motor neurons.
A
D) both sensory and motor neurons.
7
Q
7) Which of the following houses motor neurons? A) central canal of the spinal cord B) posterior root of spinal nerve C) posterior root ganglion D) anterior root of spinal nerve
A
D) anterior root of spinal nerve
8
Q
8) What connective tissue sheath wraps the axon of a neuron? A) endoneurium B) fascicle C) epineurium D) perineurium
A
A) endoneurium
9
Q
9) Bundles of axons within a nerve are known as: A) dendrites. B) fascicles. C) the endoneurium. D) the perineurium.
A
B) fascicles.
10
Q
10) Where is the motor response initiated?
A) cranial nerves
B) spinal nerves
C) lower motor neurons of the peripheral nervous system (PNS)
D) motor areas of the brain
A
D) motor areas of the brain
11
Q
11) What is the name of cranial nerve VIII? A) trigeminal nerve B) facial nerve C) glossopharyngeal nerve D) vestibulocochlear nerve
A
D) vestibulocochlear nerve
12
Q
12) The vagus nerve is represented by Roman numeral: A) I. B) X. C) V. D) XII.
A
B) X.
13
Q
13) Which cranial nerve is generally thought of as a mixed nerve? A) hypoglossal nerve (XII) B) vestibulocochlear nerve (VIII) C) accessory nerve (XI) D) glossopharyngeal nerve (IX)
A
D) glossopharyngeal nerve (IX)
14
Q
14) Which cranial nerve is NOT involved in eye movement? A) oculomotor nerve (III) B) abducens nerve (VI) C) vestibulocochlear nerve (VIII) D) trochlear nerve (IV)
A
C) vestibulocochlear nerve (VIII)
15
Q
15) The cranial nerves that have neural connections with the tongue include all of the following EXCEPT: A) trochlear nerve (IV). B) trigeminal nerve (V). C) facial nerve (VII). D) glossopharyngeal nerve (IX).
A
A) trochlear nerve (IV).
16
Q
16) Which cranial nerve detects smell? A) optic nerve (II) B) olfactory nerve (I) C) oculomotor nerve (III) D) trochlear nerve (IV)
A
B) olfactory nerve (I)
17
Q
17) An inability to swallow indicates a problem with the:
A) accessory nerve (XI) or hypoglossal nerve (XII).
B) olfactory nerve (I).
C) trochlear nerve (IV) or abducens nerve (VI).
D) trigeminal nerve (V) or glossopharyngeal nerve (IX).
A
D) trigeminal nerve (V) or glossopharyngeal nerve (IX).
18
Q
18) Ms. Parker has damage to the sensory root of the facial nerve (VII). Which of the following symptoms matches this information? A) inability to elevate the mandible B) inability to swallow C) inability to taste D) inability to smell
A
C) inability to taste
19
Q
19) Loss of balance and equilibrium can indicate damage to the: A) hypoglossal nerve (XII). B) accessory nerve (XI). C) vestibulocochlear nerve (VIII). D) trochlear nerve (IV).
A
C) vestibulocochlear nerve (VIII).
20
Q
20) The geniculate ganglion is one of several ganglia that house cell bodies of the sensory root of the: A) facial nerve (VII). B) vagus nerve (X). C) trigeminal nerve (V). D) glossopharyngeal nerve (IX).
A
A) facial nerve (VII).
21
Q
21) What specific spinal nerve branch controls the movement of rectus abdominis, a skeletal muscle on the anterior surface of the body? A) posterior ramus B) posterior (dorsal) root ganglion C) posterior root D) anterior ramus
A
D) anterior ramus
22
Q
22) Which of the following is INCORRECT about the numbers of spinal nerves? A) 5 pairs of sacral spinal nerves B) 5 pairs of lumbar spinal nerves C) 7 pairs of cervical spinal nerves D) 12 pairs of thoracic spinal nerves
A
C) 7 pairs of cervical spinal nerves
23
Q
23) Which of the following parts of a spinal nerve carries sensory information only? A) posterior (dorsal) root B) anterior root C) posterior ramus D) anterior ramus
A
A) posterior (dorsal) root
24
Q
24) The anterior root and posterior root fuse to form a(n): A) anterior horn. B) posterior (dorsal) root ganglion. C) spinal nerve. D) posterior horn.
A
C) spinal nerve.
25
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25) A network of nerves is known as a:
A) ramus.
B) plexus.
C) root.
D) horn.
```
B) plexus.
26
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26) During a boxing match, Sammy was hit on the side of the neck. He stopped breathing temporarily due to damage to the:
A) cervical plexus.
B) sacral plexus.
C) brachial plexus.
D) lumbar plexus.
```
A) cervical plexus.
27
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27) Which plexus provides motor and sensory innervation to the upper limb?
A) brachial plexus
B) cranial plexus
C) sacral plexus
D) lumbar plexus
```
A) brachial plexus
28
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28) The phrenic nerve is a member of the:
A) cervical plexus.
B) brachial plexus.
C) sacral plexus.
D) lumbar plexus.
```
A) cervical plexus.
29
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29) Which of the following does NOT belong to the brachial plexus?
A) musculocutaneous nerve
B) median nerve
C) phrenic nerve
D) ulnar nerve
```
C) phrenic nerve
30
30) Striking the "funny" bone is actually stimulation (or injury) to the: A) axillary nerve.
B) radial nerve.
C) ulnar nerve.
D) median nerve.
C) ulnar nerve.
31
```
31) Which muscle or muscle group is served by the femoral nerve?
A) gluteus maximus
B) quadriceps femoris group
C) gastrocnemius
D) hamstring group
```
B) quadriceps femoris group
32
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32) The longest and largest nerve in the body belongs to the sacral plexus and is known as the:
A) femoral nerve.
B) common fibular nerve.
C) axillary nerve.
D) sciatic nerve.
```
D) sciatic nerve.
33
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33) Olfactory receptors depolarize in response to an odorant, turning a stimulus into an electrical signal. This conversion is known as:
A) sensory transduction.
B) repolarization.
C) propagation.
D) adaptation.
```
A) sensory transduction.
34
34) Sensory transduction occurs in: A) upper motor neurons.
B) PNS sensory neurons.
C) CNS interneurons.
D) lower motor neurons.
B) PNS sensory neurons.
35
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35) Sensory receptors that adapt to stimuli after a certain period of time are:
A) thermoreceptors.
B) rapidly adapting receptors.
C) nociceptors.
D) slowly adapting receptors.
```
B) rapidly adapting receptors.
36
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36) The stretch of a full urinary bladder is detected by a(n):
A) exteroceptor.
B) photoreceptor.
C) interoceptor.
D) thermoreceptor.
```
C) interoceptor.
37
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37) Potentially damaging stimuli that result in pain are selectively detected by:
A) nociceptors.
B) photoreceptors.
C) chemoreceptors.
D) proprioceptors.
```
A) nociceptors.
38
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38) Photoreceptors are found only in the:
A) nose.
B) ear.
C) eye.
D) mouth.
```
C) eye.
39
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39) Your wrap your hands around a warm cup of hot chocolate. This sensation is detected by a:
A) hair follicle receptor.
B) chemoreceptor.
C) thermoreceptor.
D) photoreceptor.
```
C) thermoreceptor.
40
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40) Which mechanoreceptor detects deep pressure?
A) Merkel cell fiber
B) lamellated corpuscle
C) Ruffini ending
D) tactile corpuscle
```
B) lamellated corpuscle
41
```
41) Mechanoreceptors might detect which of the following sensations?
A) smell
B) pressure
C) temperature
D) light
```
B) pressure
42
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42) The speed of nerve impulse transmission through the axon of a sensory neuron will be quickest in:
A) axons that adapt to stimuli.
B) a large-diameter, myelinated axon.
C) axons with a greater receptive field.
D) a small-diameter, unmyelinated axon.
```
B) a large-diameter, myelinated axon.
43
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43) A typical somatic sensory neuron is classified as a:
A) first-order neuron.
B) second-order neuron.
C) third-order neuron.
D) lower neuron.
```
A) first-order neuron.
44
44) A test known as two-point discrimination threshold measures: A) the type of mechanoreceptor being stimulated.
B) the amount of pressure we can sustain before feeling pain.
C) the type of sensory neuron serving a region of skin.
D) the relative size of receptive fields.
D) the relative size of receptive fields.
45
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45) Regions of skin supplied by a spinal nerve for somatic sensation are known as:
A) lines of cleavage.
B) the rule of nines.
C) dermatomes.
D) the ABCDE rule.
```
C) dermatomes.
46
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46) Ms. Carroll went to her doctor's office with pain in her right shoulder blade and learned she was having a gallbladder attack. You're not surprised to hear about the unusual location of her pain since it is known as:
A) the receptive field.
B) phantom limb pain.
C) referred pain.
D) chronic pain.
```
C) referred pain.
47
```
47) Visceral pain may be perceived as cutaneous pain, a phenomenon known as:
A) phantom limb pain.
B) slowly adapting reception.
C) referred pain.
D) the receptive field.
```
C) referred pain.
48
48) What part of the nervous system integrates and interprets information from PNS sensory neurons?
A) sensory (afferent) division
B) visceral motor division, or autonomic nervous system (ANS)
C) central nervous system (CNS)
D) somatic nervous system (SNS)
C) central nervous system (CNS)
49
```
49) What connects the upper motor neurons to lower motor neurons?
A) primary afferent neuron
B) sensory neurons
C) interneurons
D) muscle fibers
```
C) interneurons
50
```
50) What type of neuron contacts a muscle fiber and initiates a muscle contraction?
A) sensory neuron
B) upper motor neuron
C) interneuron
D) lower motor neuron
```
D) lower motor neuron
51
```
51) What type of motor neuron stimulates skeletal muscle fibers to contract by the excitation- contraction mechanism?
A) upper motor neuron
B) α-motor neuron
C) interneuron
D) γ-motor neuron
```
B) α-motor neuron
52
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52) Motor neuron pools consist of:
A) upper motor neurons.
B) primary afferent neurons.
C) secondary afferent neurons.
D) lower motor neurons.
```
D) lower motor neurons.
53
53) Place the following steps in order for motor control.
1. Upper motor neurons stimulate lower motor neurons.
2. Sensory information is relayed back to the cerebellum so movement can be modified if needed.
3. Upper motor neurons in the premotor cortex select a motor program.
4. Lower motor neurons stimulate a skeletal muscle to contract.
5. The basal nuclei enable the thalamus to stimulate upper motor neurons of the primary cortex.
A) 3, 5, 1, 2, 4
B) 2, 5, 3, 1, 4
C) 3, 5, 1, 4, 2
D) 5, 3, 1, 4, 2
C) 3, 5, 1, 4, 2
54
54) Which of the following does NOT characterize a reflex?
A) A reflex is an automatic response to a stimulus.
B) Neural integration of a reflex usually occurs in the PNS.
C) Reflexes require a stimulus to initiate a motor response.
D) The motor response to a stimulus is rapid.
B) Neural integration of a reflex usually occurs in the PNS.
55
55) Which of the following must occur first in a reflex arc?
A) delivery of motor response to effector
B) detection by receptor and delivery of stimulus
C) integration in the central nervous system (CNS)
D) transmission from the primary motor cortex
B) detection by receptor and delivery of stimulus
56
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56) What type of sensory receptors are muscle spindles and Golgi tendon organs?
A) nociceptor
B) thermoreceptor
C) mechanoreceptor
D) chemoreceptors
```
C) mechanoreceptor
57
57) What is NOT true of muscle spindles?
A) Muscle spindles are embedded within extrafusal muscle fibers.
B) The contractile poles of intrafusal fibers within muscle spindles are innervated by γ-motor neurons.
C) Muscle spindles are receptors for the stretch reflex.
D) Muscle spindles are found within tendons.
D) Muscle spindles are found within tendons.
58
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58) A simple reflex with only a single synapse between the sensory and motor neurons is known as a:
A) somatic reflex.
B) visceral reflex.
C) polysynaptic reflex.
D) monosynaptic reflex.
```
D) monosynaptic reflex.
59
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59) Determine the polysynaptic reflex from this list of examples.
A) jaw-jerk reflex
B) patellar (knee-jerk) reflex
C) flexion (withdrawal) reflex
D) simple stretch reflex
```
C) flexion (withdrawal) reflex
60
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60) What reflex causes muscle relaxation?
A) crossed-extension reflex
B) Golgi tendon reflex
C) stretch reflex
D) flexion (withdrawal) reflex
```
B) Golgi tendon reflex
61
61) The inability to produce a gag reflex could indicate a problem with the:
A) facial nerve (VII) or trigeminal nerve (V).
B) glossopharyngeal nerve (IX) or vagus nerve (X).
C) abducens nerve (VI) or trochlear nerve (IV).
D) hypoglossal nerve (XII) or vestibulocochlear nerve (VIII).
B) glossopharyngeal nerve (IX) or vagus nerve (X).
62
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62) Which of the following complements the flexion (withdrawal) reflex?
A) Golgi tendon reflex
B) gag reflex
C) crossed-extension reflex
D) stretch reflex
```
C) crossed-extension reflex
63
63) In the crossed-extension reflex, if the right leg flexes, then the left leg: A) extends.
B) abducts.
C) flexes.
D) adducts.
A) extends.
64
64) What cranial nerves are involved in the sensory and the motor roles for the corneal blink reflex?
A) trigeminal nerve (V) as sensory; facial nerve (VII) as motor
B) optic nerve (II) as sensory, oculomotor nerve (III) as motor
C) trochlear nerve (IV) as sensory, abducens nerve (VI) as motor
D) glossopharyngeal nerve (IX) as sensory, oculomotor nerve (III) as motor
A) trigeminal nerve (V) as sensory; facial nerve (VII) as motor
65
65) The central nervous system (CNS) processes sensory input and transmits the impulses through the peripheral nervous system (PNS) to effectors for motor output.
TRUE
66
66) Cranial nerves and spinal nerves are the two types of nerves found in the peripheral nervous system (PNS).
TRUE
67
67) The visceral motor division (autonomic nervous system, or ANS) controls the body's voluntary motor functions.
FALSE
68
68) All cranial nerves are considered mixed nerves.
FALSE
69
69) The first pair of cranial nerves is the optic nerve (I).
FALSE
70
70) The trigeminal nerve (V) has three nerve branches: optic nerve, maxillary nerve, and oculomotor nerve.
FALSE
71
71) The posterior (dorsal) root of a spinal nerve and the posterior ramus are considered mixed nerves since they both carry sensory and motor information.
FALSE
72
72) The lumbar nerve plexuses arise from the anterior rami of L1 - L4 and innervate structures of the pelvis and lower limb.
TRUE
73
73) Proprioceptors are located in the musculoskeletal system where they detect the movement and position of a joint or body part.
TRUE
74
74) Interoceptors detect stimuli from the inside of the body, such as blood pressure, stretch of a full urinary bladder, and the body's temperature.
TRUE
75
75) Receptive field maps show the regions of skin and the spinal nerve that supplies somatic sensation to them.
FALSE
76
76) Motor control is initiated by lower motor neurons and transmitted to upper motor neurons by interneurons situated within the CNS.
FALSE
77
77) Upper motor neurons directly contact and stimulate skeletal muscle fibers to contract.
FALSE
78
78) Polysynaptic reflexes involve multiple synapses while monosynaptic reflexes only involve a single synapse.
TRUE
79
79) The simple stretch reflex employs mechanoreceptors known as Golgi tendon organs to detect the degree of stretch experienced by a muscle.
FALSE
80
80) Cervical plexus
A
81
81) Lumbar plexus
C
82
82) Sacral plexus
D
83
83) Brachial plexus
B
84
84) Nerve plexus that includes the phrenic nerve
A
85
85) Nerve plexus that includes the sciatic nerve
D
86
86) Olfactory bulb (synapses with Cranial nerve I)
A
87
87) Abducens nerve
D
88
88) Oculomotor nerve
B
89
89) Cranial nerve IV
C
90
90) Cranial nerve XII
E
91
91) Discuss the functions of the two main divisions of the peripheral nervous system (PNS).
The two main divisions of the peripheral nervous system (PNS) are the sensory (afferent) division and the motor (efferent) division. The sensory division consists of sensory (afferent) neurons that detect stimuli and bring them to the central nervous system (CNS). The motor division consists of motor (efferent) neurons that carry out the motor functions of the nervous system. Both the sensory and motor divisions can be further classified.
92
92) List and describe the connective tissue sheaths that make up a nerve.
The epineurium holds together the structures that make up a nerve. Within the nerve, axons are bundled into fascicles held together and supported by a connective tissue sheath known as the perineurium. Each axon within the fascicle is surrounded by its own connective tissue sheath known as the endoneurium.
93
93) List the 12 pairs of cranial nerves, in numerical order, with their corresponding Roman numerals.
The 12 pairs of cranial nerves are olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglossal (XII).
94
94) List the cranial nerves and their corresponding Roman numerals that are generally considered sensory nerves.
The cranial nerves that generally considered sensory are the olfactory (I), optic (II), and vestibulocochlear (VIII) nerves.
95
95) Identify and name the cranial nerves responsible for eye movement. Indicate the function of each cranial nerve identified.
The oculomotor nerve (III), trochlear nerve (IV), and abducens nerve (VI) are the three pairs of cranial nerves that control eye movement. The oculomotor nerve innervates the medial rectus, superior rectus, inferior rectus, and inferior oblique muscles. These muscles are responsible for moving the eye superiorly, medially, inferiorly, and superolaterally. The trochlear nerve innervates the superior oblique muscle of each eye which allows for medial and inferior eye movement. The abducens nerve innervates the lateral rectus muscle. This muscle abducts the gaze when it turns the eye laterally.
96
96) Explain the difference between a ramus and a plexus.
A ramus is either an anterior or a posterior branch of a spinal nerve. Both anterior and posterior rami are mixed nerves. The anterior rami of the cervical, lumbar, and sacral spinal nerves come together and merge to form complicated networks of nerves called nerve plexuses. The axons of each spinal nerve cross over one another to enter different nerve plexuses.
97
97) Describe the structure of a nerve plexus and explain the advantage of this structure to its function.
The anterior rami of the cervical, lumbar, and sacral spinal nerves come together and merge to form complicated networks of nerves called nerve plexuses. The axons of each spinal nerve cross over one another to enter different nerve plexuses. For this reason, the muscles supplied by a single branch of a nerve plexus are often served by two or more different spinal nerves. This works to our advantage, as it means that injury to one spinal nerve does not completely cut off motor or sensory innervation to that body part.
98
98) List the five major nerves of the brachial plexuses.
The five major nerves of the brachial plexuses are the axillary nerves, radial nerves, musculocutaneous nerves, median nerves, and the ulnar nerves.
99
99) Discuss the spinal nerves that contribute to the sacral plexuses and the body region(s) served.
The sacral plexuses stem from the anterior rami of spinal nerves L4 - S4 and innervate structures of the pelvis, the gluteal region, and the lower limb. The sciatic nerve, the largest and longest nerve of the body, is a member of this plexus.
100
100) Describe the steps of sensory transduction when a touch receptor in the skin is activated.
The steps of sensory transduction are as follows: 1) Before a stimulus arrives, the ion channels in the axolemma of the PNS sensory neuron are closed. 2) When a stimulus arrives, mechanically gated sodium ion channels open. Sodium ions enter the axoplasm, causing a temporary depolarization referred to as receptor potential. 3) If enough sodium ions enter that the membrane potential reaches threshold, voltage-gated sodium ion channels open. An action potential is triggered and it is propagated along the axon to the CNS.
101
101) Define adaptation as it relates to sensory function. What types of mechanoreceptors adapt?
Some sensory receptors, known as rapidly adapting receptors, respond rapidly with high intensity to a stimulus. While these receptors are important for the initial detection of stimuli, they ignore ongoing stimuli. Thus, they will cease to create action potentials even with a continued stimulus. This concept is known as adaptation as it relates to sensory receptors. Tactile corpuscles and lamellated corpuscles are rapidly adapting receptors.
102
102) What can a dermatome map tell us about the location of a virus, such as the shingles?
The skin can be divided into different segments called dermatomes based on the spinal nerve that supplies the region with somatic sensation. Dermatomes can be combined and assembled into a dermatome map that represents all the spinal nerves (except the first cervical spinal nerve). The virus that causes the shingles can cause a painful skin rash with blisters. The virus can present unilaterally (along one side) along dermatomes. We can determine which spinal nerves are infected with the virus by the affected skin region(s).
103
103) How does the two-point discrimination threshold demonstrate the size of receptor fields in the skin?
In the two-point discrimination threshold test, two stimuli (such as calipers or application sticks) are placed close together on the skin. The calipers are moved increasingly apart until the subject can feel two distinct points. Different regions of the skin contain neurons with receptive fields of varying size. The more neurons that populate an area of skin, the smaller the receptive field will be. Thus, the smaller the receptive field, the smaller the distance between the two points that a subject can detect using the two-point discrimination threshold test.
104
104) Generalize the role of the lower motor neuron in motor control.
Upper motor neurons, located in the primary motor cortex of the cerebrum, stimulate lower motor neurons. Lower motor neurons innervate skeletal muscle fibers within a single skeletal muscle. Lower motor neurons initiate a muscle contraction. Groups of lower motor neurons that innervate the same muscle are called motor neuron pools.
105
105) Outline the three-step sequence of a reflex arc.
The reflex arc begins with 1) the detection of a stimulus by a sensory receptor in the PNS. 2) The stimulus is delivered to the CNS where integration occurs. 3) The rapid motor response is delivered to the effector.
106
106) Explain the difference between a monosynaptic reflex and a polysynaptic reflex.
A monosynaptic reflex involves only a single synapse within the spinal cord between the sensory and motor neurons. A polysynaptic reflex involves multiple synapses.
107
107) Outline the steps to a simple stretch reflex.
The steps of a simple stretch reflex are as follows: 1) The simple stretch reflex is initiated when an external force stretches the muscle. 2) Muscle spindles detect the stretch, and primary and secondary afferents transmit an action potential to the spinal cord. 3) In the spinal cord, the sensory afferents synapse on an alpha motor neuron and trigger an action potential. 4) The alpha motor neuron stimulates the muscle to shorten, and it returns to its optimal length.
108
108) Which of the following would be most devastating to damage: motor nerve, sensory nerve, or mixed nerve? Explain.
A mixed nerve would be the most devastating to damage as it contains both sensory and motor neurons. A damaged mixed nerve could potentially impair both sensation and movement to some degree. Sensory nerves contain only sensory neurons while motor nerves contain mostly motor neurons (with a small population of sensory neurons). Damage to a sensory nerve would only affect sensation while damage to a motor nerve would primarily affect movement of specific muscles.
109
109) People suspected of having a stroke can be asked to stick their tongues straight out. A slanted or somewhat bent tongue may be just one indicator of stroke. Determine the cranial nerve affected if the tongue is bent or slanted and identify the nerve as sensory, motor, or mixed. Describe the function of this nerve.
The affected nerve if the tongue is bent or slanted during a stroke is the hypoglossal nerve (XII). The hypoglossal nerve is a motor nerve responsible for moving the tongue. It innervates most of the intrinsic and extrinsic muscles of the tongue.
110
110) Dan injured the spinal nerves emerging from the lower lumbar and sacral region of the spinal cord during a horse-riding accident. After his injury, he reported numbness in his feet. Explain the connection between the loss of sensation he has described and the plexus responsible for serving this area.
The sacral plexus forms from the anterior rami of spinal nerves L4 - S4. Rami are mixed nerves, housing both sensory and motor neurons. The sciatic nerve is the largest nerve of this plexus. It splits into two main branches, the tibial nerve and the common fibular nerve. The tibial nerve divides into its terminal branches which serve the muscles and skin of the foot at the level of the medial malleolus of the tibia. Since Dan reported loss of sensation in his feet, the sensory neurons of the sciatic nerve must have sustained injury after his accident.
111
111) Which nerve of the brachial plexus becomes inflamed, resulting in carpal tunnel syndrome? Explain what regions are served by this inflamed nerve.
Inflammation of the median nerve results in carpal tunnel syndrome. The median nerve runs down the middle of the arm and forearm. It serves the wrist and digital flexor muscles. In the hand, this nerve supplies some of the intrinsic hand muscles and skin over the anterior thumb, the second and third digits, and the lateral half of the fourth digit.
112
112) A patient sustained an injury to the lower motor neurons when a board fell on his back at a construction site. The upper motor neurons are intact and undamaged. Determine the effect, if any, on motor control.
The upper motor neurons stimulate the lower motor neurons. Since they sustained damage, the lower motor neurons will be unable to stimulate affected skeletal muscles to contract. This patient will experience weakness or paralysis of the affected muscles and loss of reflexes since the lower motor neurons are damaged.
113
113) Predict the impact on the gag reflex when a person has a damaged vagus nerve (X).
Somatic motor neurons of the vagus nerve (X) are responsible for triggering contractions of the muscles of the pharynx to produce the "gag" during the gag reflex. Thus, a person would not be able to elicit a gag reflex if the vagus nerve is damaged.
