Neuroscience: CNS, Reflexes, and Sensory Disturbances

1 JANA ******************************************************************************** C. Intensity discrimination D. Two point discrimination 2. Which of the following receptors is correctly paired with the type of stimulus to A. Pacinian corpuscle and motion. 1-INTRODUCTION B. Meissner’s corpuscle and deep pressure. C. Merkel cells and warmth. 1-Which of the following statements about D. Ruffini corpuscles and sustained pressure. the central nervous system (CNS) is correct? E. Muscle spindle and tension a) White matter contains many nerve cell 3. A generator potential bodies A. always leads to an action potential. b) The myelin sheaths are formed by Schwann B. increases in amplitude as a more intense cells stimulus is applied. c) There are twelve pairs of cranial nerves C. is an all-or-none phenomenon. 2-Which of the following statements about D. is unchanged when a given stimulus is the central nervous system (CNS) are applied repeatedly over time. correct? E. all of the above. a) White matter is arranged in bundles known 4. Sensory systems code for the following as nerve trunks attributes of a stimulus: b) Microglia are scattered throughout the grey A. modality, location, intensity, and duration and white matter B. threshold, receptive field, adaptation, and c) Each oligodendrocyte forms the myelin of discrimination sheath of a number of different axons C. touch, taste, hearing, and smell 3-Which of the following statements about D. threshold, laterality, sensation, and duration (CNS) are correct? E. sensitization, discrimination, energy, and a) The capillaries of the brain are covered by Projection the end feet of oligodendrocytes 5) Generator potential: b) The extracellular fluid surrounding nerve A. obey all or non low cells is insulated from changes in the B. has ARP composition of the plasma. C. propagated c) The cerebrospinal fluid (csf) is an D. all of the above. ultrafiltrate of plasma E. none of the above. d) The csf is secreted by the choroid plexuses 6) Slowly adapting receptors differ from of the cerebral ventricles rapidly adapting receptors in: 4-Which of the following statements about A. stopping to discharge after a relatively the nervous system are true? shorter period of constant stimulation a) Each cerebral hemisphere is divided into two B. generating receptor potentials as long as lobes. stimulus is applied. b) Each spinal segment gives rise to four spinal C. detecting the dynamic properties of stimuli nerves. D. detecting velocity of stimuli c) The dorsal root ganglia contain the cell 7) Gluco-receptors are: bodies of the primary sensory neurons A. Interoceptors d) The white and grey matter of the spinal cord B. Hypothalamic receptors is arranged in the same way as that of the C. Slowly adapting receptors cerebral hemispheres. D. Chemical receptors e) Grey matter contains the cell bodies and E. All of the above dendrites of neurons. 8)Receptors detect stimulus intensity by: A. lowering the threshold for receptor stimulation 2-Properties of receptors B. generating receptor potentials having higher 1) Weber – Fechner law is related to: magnitudes A. Modality discrimination C. generating nerve impulses transmitted along B. Unit receptor field sensory fibers at higher velocities REVISION CNS: ---------------------------------------------------------------------------------- 2 JANA ******************************************************************************** D. enhancing the central effects of sensory 14-Pacinian corpuscles are Impulses (A) a type of temperature receptor (B) usually innervated by Aδ nerve fibers 9) The ability to localize the site of stimuli (C) rapidly adapting touch receptors depends upon: A. the type of the stimulated receptor (D) slowly adapting touch receptors B. connections between receptor and cortex (E) pain receptors C. rate of adaptation of stimulated receptors 15-Adaptation to a sensory stimulus produces D. the nature of the stimulus (A) a diminished sensation when other types of sensory stimuli are withdrawn 10) A 40-year-old man loses his right hand in (B) a more intense sensation when a given a farm accident. Four years later, he stimulus is applied repeatedly has episodes of severe pain in the missing (C) a sensation localized to the hand when the hand (phantom limb pain). scan study of his nerves of the brachial plexus are stimulated cerebral cortex might be expected to show A. expansion of the right hand area in his right (D) a diminished sensation when a given primary somatosensory cortex. stimulus is applied repeatedly over time B. expansion of the right-hand area in his left (E) a decreased firing rate in the sensory nerve primary somatosensory cortex. from the receptor when one’s attention is C. a metabolically inactive spot where his hand directed to another matter area in his left primary somatosensory 16. Which of the following sensations is not cortex would normally be. generated by impulses initiated in naked D. projection of fibers from neighboring nerve endings? sensory areas into the right-hand area of his (A) Touch right primary somatosensory cortex. (B) Pain E. projection of fibers from neighboring (C) Cold sensory areas into the right-hand area of his left (D) Tickle primary somatosensory cortex. (E) Proprioception 11)Thermoreceptors are: 17-In which of the following is the frequency A. rapidly adapting receptors of stimulation not linearly related to the B. biphasic receptors strength of the sensation felt? C. slowly adapting receptors (A) Sensory area of the cerebral cortex D. none of the above (B) Specific projection nuclei of the thalamus (C) Lateral spirithalamic tract 12)Which of the following receptors is (D) Dorsal horn responsible for measuring the intensity of a (E) Cutaneous receptors steady pressure on the skin surface a. Krause ending 18. Which of the following receptors and b. Meissner corpuscle sense organs are incorrectly paired? c. Merkel disk (A) Rods and cones : eye d. Ruffini ending (B) Receptors sensitive to sodium : taste buds (C) Hair cells : olfactory mucous membranes 13)In sensory receptors: A. Stimulus energy is converted into a local (D) Receptors sensitive to stretch : carotid sinus depolarization. (E) Glomus cells : carotid body B. The generator potential is graded and self19. Which of the following sensations is most propagating. subject to facilitation and inhibition in the C. A generator potential can be produced by central nervous system? only one form of energy. (A) Touch D. The frequency of action potentials generated (B) Warmth doubles when the strength of the stimulus (C) Pain doubles. (D) Hearing E. Serving touch sensation, constant (E) Taste suprathreshold stimulation causes action 20. Which of the following does not contain potentials to cation channels that are activated by be generated at a constant rate. REVISION ---------------------------------------------------------------------------------- 3 JANA ******************************************************************************** D. resembles “fast pain” produced by noxious mechanical distortion,producing stimulation of the skin. depolarization? (A) Olfactory neurons 7. A ventrolateral cordotomy is performed (B) Pacinian corpuscles that produces relief of pain in the right (C) Hair cells in cochlea leg. It is effective because it interrupts the (D) Hair cells in semicircular canals A. left dorsal column. (E) Hair cells in utricle B. left ventrolateral spinothalamic tract. C. right ventrolateral spinothalamic tract. 3-Pain D. right medial lemniscal pathway. 1) In patient having intermittent E. a direct projection to the primary claudications, they will suffer from: somatosensory cortex. A. Visceral pain 8. Which of the following CNS regions is not B. Deep pain correctly paired with a neurotransmitter or C. Cutaneous pain a chemical involved in pain modulation? D. Colicky pain A. Periaqueductal gray matter and morphine 2) The neuro transmitter released from B. Nucleus raphe magnus and norepinephrine middle raphe nuclei is: C. Spinal dorsal horn and enkephalin A. Enkephalin D. Dorsal root ganglion and opioids B. Serotonin E. Spinal dorsal horn and serotonin C. Substance P 9.Pain is: D. Glycine A. Can be elicited from lung parenchyma. 3. Nociceptors B. Pre-potent stimulus. A. are activated by strong pressure, severe cold, C. Detected by Pacinian corpuscle. severe heat, and chemicals. D. Carried by A beta myelinated fibers. B. are absent in visceral organs. E. All of the above. C. are specialized structures located in the skin 10.Inhibition of pain signals by tactile and joints. stimulation of a skin surface involves inhibition D. are innervated by group II afferents. of which of the following selections? E. are involved in acute but not chronic pain. A. Type B fibers in peripheral nerves 4. Endogenous opioids B. Type C fibers in peripheral nerves A. bind to both ionotropic receptors and GPCR. C. Type A alpha fibers in peripheral nerves B. include morphine, endorphins, , dynorphins. D. Type A beta fibers in peripheral nerves C. show the following order of affinity for δ 11.Referred pain can be elicited by: receptors: dynorphins > endorphins. A. Renal stone sensory disturbances B. Ureteric stone D. show the following order of affinity for μ C. Billiary stone receptors: dynorphins > endorphins. D. All of the above E. show the following order of affinity for κ 12.Intermittent claudications is an example for: receptors: endorphins > > enkephalins. A. visceral pain. 5. Which of the following are correctly B. deep pain. paired? C. primary hyperalgesia. A. Neuropathic pain and withdrawal reflex D. secondary hyperalgesia B. First pain and dull, intense, diffuse, and 13. All are reaction to pain, except: unpleasant feeling A. changes in heart rate or respiratory rate C. Physiological pain and allodynia B. stoppage of the response of nociceptors D. Second pain and C fibers C. depression or crying E. Nociceptive pain and nerve damage D. skeletal muscle contraction 6. Visceral pain 14.Pain sensation: A. shows relatively rapid adaptation. A. produces reactions that block transmission B. is mediated by B fibers in the dorsal roots of of pain impulses the spinal nerves. B. is evoked by strong stimulation of specific C. is poorly localized. receptors REVISION ---------------------------------------------------------------------------------- 4 JANA ******************************************************************************** C. arises from small encapsulated receptors b. Endorphins D. occurs when the stimulus causes damage of c. Serotonin the sensory receptors d. Somatostatin e. Substance P 15.Pain receptors: A. are phasic receptors B. become more sensitive with prolonged stimulation 22.Severe pain may lead to all except C. are more numerous in viscera than other A. A fall in blood pressure due to a fall in tissues vascular resistance in skeletal muscle. D. include different morphological types B. A fall in heart rate due to an increase in E. all of the above. cardiac vagal tone. C. Vomiting through a reflex centre in the 16. Visceral pain: A. is more common than other types of pain brainstem. B. evokes depressor autonomic reactions D. Profuse sweating due to activation of C. arises only from wall of the visceral organs sympathetic nerves. D. is often well localized E. Suppression of cortisol secretion. E. all of the above. 23-Loss of pain sensation leads to all except A. in Feet may lead to skin ulceration. 17.Enkephalin blocks pain transmission by: A. blocking the response of pain receptors to B. in Knee may lead to joint damage. painful stimuli C. in Ears and fingers usually precedes frostbite. B. blocking Ca++ channels in the central D. in Leg follows surgical division of the terminals of pain sensory fibers spinocerebellar tracts in the spinal cord. C. slowing down transmission of pain E. in Face follows surgical division of the impulses through synapses in the pain facial nerve. pathway 24-Pain receptors are D. inhibiting the response of the cerebral A. Similar in structure to Pacinian corpuscles. cortical somatic sensory area to pain signals B. Stimulated by a rise in the local K_ concentration. 18. Transmitters in pain control system C. Quick to adapt to a constant stimulus. include all the following, except: A. serotonin D. More easily stimulated in injured tissue. B. acetylcholine E. Stimulated in the wall of the gut by agents C. enkephalin which damage the tissues. D. dopamine 25-Visceral pain A. Is poorly localized compared with pain 19-the neurotransmitter released from arising in skin.  middle raphe: A-enkephalin. B. Is often felt in the mid line.  B-serotonin C. May cause reflex contraction of overlying C-substance P skeletal muscle.  D-glycine. D. May cause reflex vomiting.  E. May cause reflex changes in arterial blood 20.Ischemic pain is associated with which of pressure.  the following? 26-Pain receptors in the gut and urinary a. A beta (Aβ) sensory fibers tract may be stimulated by all true except b. Afferent pathway in the neospinothalamic tract A. Cutting through their wall with a sharp c. Overstimulation of somatic touch receptors scalpel. d. Rapidly adapting receptors B. Distention. e. Sensory fibers terminating within the C. Inflammation of the wall. substantia gelatinosa of the dorsal horn of the D. Acid fluid. spinal cord 21-Synaptic transmission between pain fibers fromE. Vigorous rhythmic contractions behind an the pelvis and spinal cord neurons is mediated by obstruction. which of the following? a. Acetylcholine REVISION ---------------------------------------------------------------------------------- 5 JANA ******************************************************************************** A. Lateral lemniscus 3-Sensations B. Medial lemniscus 1- Superficial sensations include all of the C. Gracile tract following, except: D. Cuneate tract A. Crude touch. 3) Second order neuron for fine touch from B. Stereognosis. lower limb is: C. Cold temperature. A. Lateral lemniscus D. Fast pain. B. Medial lemniscus 2- About stereognosis: C. Gracile tract A. It is tested with open eyes D. Cuneate tract B. The tested object is familiar to patient 4) Medial lemniscus terminates in: C. It is a type of superficial fine sensation A. Postro medial ventral nucleus of thalamus D. All of the above B. Postro lateral ventral nucleus of thalamus E. None of the above C. Reticular formation 3-Proprioceptive sensations include all the D. Inferior colliculi following, except: 5) Lateral lemniscus terminates in: A. position sense A. Postro lateral ventral nucleus of thalamus B. equilibrium sense B. Postro medial ventral nucleus of thalamus C. movement sense C. Reticular formation D. kinesthetic sense D. Inferior colliculi 4-Proprioceptive sensations are transmitted 6) Somatic sensory area in cortex receives by all the following pathways, except: impulses from all the following, except: A. gracile tract A. Medial lemniscus B. spinothalamic tracts B. Lateral lemniscus C. spinocerebellar tract C. Trigeminal lemniscus D. spino olivary tract D. Spinal lemniscus 5-The distance by which two touch stimuli 6-Pain from upper limb is carried by: must be separated to be perceived as two A. Ventral spinothalamic tract separate stimuli is greatest on B. Lateral spinothalamic tract (A) the lips C. Gracile tract (B) the palm of the hand D. Cuneate tract (C) the back of the scapula 7- Pain from lower limb is carried by: (D) the dorsum of the hand A. Ventral spinothalamic tract (E) the tips of the fingers B. Lateral spinothalamic tract 6-Stimulation of which of the following C. Gracile tract might be expected to produce itching? D. Cuneate tract (A) Dorsal root C fibers 8-Impulses serving pain sensation in the left (B) B fibers in peripheral nerves foot are relayed (C) Dorsal columns of the spinal cord A. Across synapses in the left posterior root (D) Touch receptors ganglion. (E) Motor fibers in the ventral roots of the B. By fibres in the left spinothalamic tract. spinal nerves C. By the same spinal cord tract which serves heat and cold sensation. 4-Tracts D. To the thalamus on the right side. 1) If there is loss in the vibration sense in the E. To the cerebral cortex before entering face, the lemniscus affected is: consciousness. A. Spinal 9-Neurones serving conscious muscle B. Medial proprioception all are true except C. Trigeminal A. Conduct impulses at a similar rate to D. Lateral somatic motor neurones. 2) Second order neuron for proprioceptive B. Have their cell bodies in the ipsilateral from upper limb is: posterior horn of the spinal cord. REVISION ---------------------------------------------------------------------------------- 6 JANA ******************************************************************************** C. Use a different pathway from the primary the lumbar region. neurones serving unconscious proprioception. B. transecting the left half of the spinal cord in D. Synapse with secondary neurones whose the upper thoracic region. axons project up the ipsilateral posterior C. transecting sensory and motor pathways on (dorsal) columns of the spinal cord. the right side of the pons. E. Synapse with neurones which cross the D. transecting the right half of the spinal cord midline of the body in the brainstem. in the upper thoracic region. E. transecting the dorsal half of the spinal cord 5-Sensory disturbance in the upper thoracic region. 1) Astereognosis could be resulted from the 6-In patient with tabes dorsalis, there is: lesions in the following areas Except: A. motor ataxia A. Dorsal root fibers central to the ganglia B. sensory ataxia B. Gracile and cuneate tract C. mixed ataxia C. Syringomyelia D. none of the above D. Area 5 and 7 in cerebral cortex 7-In patient with thalamic syndrome, there is: 2) Neurosphyilis is associated with: A. motor ataxia A. Sensory ataxia B. sensory ataxia B. Motor ataxia C. mixed ataxia C. Mixed ataxia D. none of the above D. None of the above 8-In thalamic syndrome: 3) In left side Brown-Sequard syndrome, all A. All sensory lemnisci are seriously affected the following are correct, Except: on same side A. Loss of pain sensation in left side below B. Loss of all kinesthetic sensations from lesion opposite half of the body B. Loss of rough touch in right side below C. Exaggerated tendon knee jerk is present on lesion opposite side of the body C. Secondary hyperalgesia in the left side D. All of the above above level of the lesion E. None of the above D. Loss of proprioceptive in left side below 9) Which of the followings is a manifestation of lesion Brown-Sequard syndrome? 4. A 50-year-old woman undergoes a A. Loss of fine touch below level on opposite side neurological exam that indicates loss of B. Loss of pain at level on same side pain and temperature sensitivity, vibratory C. Loss of temperature below level on same side sense, and proprioception in the left D. All of the above leg. These symptoms could be explained by E. None of the above A. a tumor on the right medial lemniscal 10-Asteriognosis result from the lesion in all pathway in the sacral spinal cord. the following areas except: B. a peripheral neuropathy. A-dorsal root fibers central to ganglia. C. a tumor on the left medial lemniscal B-gracile and cuneate tract. pathway in the sacral spinal cord. C-syringomyelia D. a tumor affecting the right posterior D-area 5, 7 in cerebral cortex. paracentral gyrus. 11-Cutaneous pain E. a large tumor in the right lumbar A. Can be caused by overstimulation of touch ventrolateral spinal cord. receptors. 5. After falling down a flight of stairs, a B. Can be caused by excitation of receptors by young woman is found to have partial chemicals released in injured tissue. loss of voluntary movement on the right side C. Can be elicited more readily if the tissue has of her body and loss of pain and been injured recently. temperature sensation on the left side below D. Receptors adapt to stimulation more quickly the midthoracic region. It is probable than touch receptors. that she has a lesion A. transecting the left half of the spinal cord in REVISION ---------------------------------------------------------------------------------- 7 JANA ******************************************************************************** E. Transmission at spinal cord level is B. Greater loss of motor power in the right leg facilitated by opening of potassium channels in than in the left leg. the C. Greater loss of conscious proprioception in post-synaptic membrane. the right than in the left leg. D. Respiratory failure 12-Posterior column damage in the spinal E. Loss of the micturition reflex. cord may impair all true except A. Vibration sense. 17-A 10-year-old girl with type I diabetes B. Pain sensation. develops a neuropathy of sensory neurons C. The flexor plantar response to stimulation of with free nerve endings. As a result, the sole. quantitative sensory testing will reveal D. Touch sensation. higher-than-normal thresholds for detection E. The ability to stand steadily with the eyes of which of the following stimuli? closed. a. Fine touch b. Muscle length 13-Sensory disturbance consisting of A. Pain, sensory loss and paraesthesiae in one c. Pressure leg suggests a spinal cord lesion. d. Temperature B. Loss of pain, temperature but not touch e. Vibration sensation in the arms suggests a spinal cord 6-Synapse lesion. 1. Which of the following events is correctly C. Loss of two-point discrimination but not paired with the change in ionic currents touch sensation suggests a lesion in the causing the event? thalamus. A. Fast inhibitory postsynaptic potentials D. Loss of all sensations on the left side (IPSPs) and closing of Cl − channels. suggests a right internal capsule lesion. B. Fast excitatory postsynaptic potentials E. Loss of all sensations in a skin region (EPSPs) and an increase in Ca 2+ conductance. suggests a peripheral nerve or posterior root C. End plate potential and ↑in Na+ conductance. lesion. D. Presynaptic inhibition and closure of 14-Long-term consequences of transection of voltage-gated K + channels. the spinal cord in the lower E. Slow EPSPs and↑in K+ conductance. cervical region include all true except 2. Which of the following statements about A. Loss of thermoregulatory sweat production neurotransmitters is true? in the legs. A. All neurotransmitters are derived from B. Severe flexor spasms when the skin of the amino acid precursors. legs is stimulated. B. Small molecule neurotransmitters include C. Paralysis of bladder muscle. dopamine, histamine, ATP, glycine, D. Inability to regulate sympathetic tone in leg enkephalin, and norepinephrine. blood vessels in response to baroreceptor C. Large molecule transmitters include ATP, stimulation. cannabinoids, substance P, and vasopressin. E. Inability to erect the penis and ejaculate D. Norepinephrine act as a neurotransmitter in semen. the periphery and a neuromodulator in the 15-Headache can be produced by all except CNS. A. Dilatation of intracranial blood vessels. E. NO is a neurotransmitter in the CNS. B. Constriction of extracranial blood vessels. 3. Which of the following receptors is C. Meningeal irritation. correctly identified as an ionotropic or a G D. Blood in the cerebrospinal fluid. Protein-coupled receptor (GPCR)? E. Loss of cerebrospinal fluid following lumbar A. Neurokinin receptor: ionotropic puncture. B. Nicotinic receptor: GPCR 16-Hemisection of the spinal cord at C7 on C. GABA A receptor: ionotropic the right side would cause D. NMDA receptor: GPCR A. Greater loss of pain sensation in the right E. Glycine: GPCR foot than in the left foot. REVISION ---------------------------------------------------------------------------------- 8 JANA ******************************************************************************** A. Electrical transmission : gap junction 4-An inhibitory post-synaptic potential all B. Negative feedback inhibition : Renshaw cell are true except: A. May be recorded in a post-ganglionic C. Synaptic vesicle docking and fusion: sympathetic neurone. presynaptic nerve terminal B. May be recorded in an anterior horn motor D. Endplate potential : muscarinic cholinergic neurone. receptor C. Does not exceed one millivolt in amplitude. E. Action potential generation : initial segment D. Moves membrane potential towards the 9.A 27-year-old man was brought to the emergency equilibrium potential for potassium. department with symptoms of opioid intoxication. E. May summate in space and time with other He was given an intravenous dose of naloxone. excitatory and inhibitory potentials in the Endogenous opioids same neurone. A. bind to both ionotropic receptors and GPCR. B. include morphine, endorphins, and dynorphins. 5-A volley of impulses travelling in a preC. show the following order of affinity for δ synaptic neurone causes all are true except A. An identical volley in the post-synaptic receptors: dynorphins > > endorphins. neurone. D. show the following order of affinity for μ B. An increase in the permeability of the prereceptors: dynorphins > endorphins. synaptic nerve terminals to calcium. E. show the following order of affinity for κ C. Vesicles in the nerve endings to fuse with receptors: endorphins > > enkephalins. the cell membrane and release their contents. 7-Types of spinal reflexes, D. The generation of at least one action potential in the post-synaptic neurone. classification of reflexes E. Neurotransmitter to travel down the nerve 1) The exception of reciprocal innervation is: axon. A. +ve Romberg's sign 6-An excitatory post-synaptic potential B. +ve Babeneski's sign A. Is the depolarization of a post-synaptic C. +ve supporting reflex nerve cell membrane that occurs when a D. All of the above presynaptic neurone is stimulated. B. Involves reversal of polarity across the post2) Reflex tetanus is characterized by: synaptic nerve cell membrane. A. Short latent period C. May be recorded from a posterior root B. Sudden rise of contraction ganglion cell. C. Fatigue D. Is propagated at the same rate as an action D. No after discharge potential. Motor tetanus & reflex tetanus, properties of E. Is caused by the electrical field induced by reflex action activity in the pre-synaptic nerve terminals. 3. Withdrawal reflexes are not 7. Which of the following electrophysiologic A. initiated by nociceptive stimuli. events is correctly paired with the change in B. prepotent. ionic currents causing the event? C. prolonged if the stimulus is strong. A. Fast inhibitory postsynaptic potentials D. an example of a flexor reflex. (IPSPs) and closing of Cl– channels E. accompanied by the same response on both B. Fast excitatory postsynaptic potentials sides of the body. (EPSPs) and an increase in Ca2+ conductance C. Endplate potential and an increase in Na+ 4. Which of the following is not conductance characteristic of a reflex? D. Presynaptic inhibition and closure of A. Reflexes can be modified by impulses from voltage-gated K+ channels various parts of the CNS. E. Slow EPSPs and an increase in K+ B. Reflexes may involve simultaneous conductance contraction of some muscles and relaxation of 8. Which of the following physiologic others. processes is not correctly paired with a C. Reflexes are chronically suppressed after structure? spinal cord transection. REVISION ---------------------------------------------------------------------------------- 9 JANA ******************************************************************************** D. Reflexes involve transmission across at least one synapse. E. Reflexes oft en occur without conscious perception. 5-Regarding reflexes a) A monosynaptic reflex arc involves one or more interneurons b) The knee jerk reflex is an example of a stretch reflex. c) Interneurons are the final common path for all reflexes. d) Withdrawal reflexes are lost following cervical section of the spinal cord. REVISION 6-A reflex action all true except: A. Is initiated at a sensory receptor organ. B. May result in endocrine secretion. C. Involves transmission across at least two central nervous synapses in series. D. May be excitatory or inhibitory. E. Is independent of higher centres in the brain. 7-In the spinal cord all false except A. Pain impulse traffic may be modulated in the posterior horn. B. Autonomic motor neurones arise in the lateral horn. C. Gamma-aminobutyric acid may act as an excitatory neurotransmitter. D. Reflex centres are normally inhibited by descending impulses from supra-spinal centres. E. Post-synaptic excitation may be mediated by amino acid derivatives acting as neurotransmitters. ----------------------------------------------------------------------------------