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NEURO TEST YEP!

neuro test

QuestionAnswer
What is the largest and best studied mechanoreceptor of the skin? -Pacinian corpuscle: lies deep within the dermis; it can be as long as 2 mm and almost 1 mm in diameter- big enough to be seen with your naked eye.
Who developed a method to map the receptive field of a single mechanoreceptor? Ake Vallbo (Swedish neuroscientist )
How does the receptive field of Meissner’s corpuscles compare to that of Ruffini’s endings and Pacianian corpuscles? Ruffini’s endings, found in both hairy and glabrous skin, are slightly smaller than Pacinian corpuscles.
How does the receptive field of Meissner’s corpuscles compare to that of Ruffini’s endings and Pacianian corpuscles? Meissner’s corpuscles are about one tenth the size of Pacinian corpuscles & are located in the ridges of glabrous skin (the raised parts of your fingerprints
.How does the receptive field of Meissner’s corpuscles compare to that of Ruffini’s endings and Pacianian corpuscles? Meissner’s corpuscles and Merkel’s disk have small receptive field size, Pacinian corpuscles and Ruffini’s ending have large receptive field size.
What is meant by “rapidly adapting” and “slow adapting” receptors? Rapidly adapting mechanoreceptors respond quickly at first but then stop firing even though the stimulus continues. Slowly adapting mechanoreceptors generate a more sustained response.
rapid firing, Meissner’s corpuscle and Pacinian corpuscle
slow firing. Merkel’s disk and Ruffini’s ending
What is meant by “two-point discrimination”? Give an example. he ability to distinguish between two points of stimuli varies at least 20 fold across the body.
Fingertips have the highest resolution because: is a higher density of mechanoreceptors. There is an enrichment of receptor types with small receptive fields. There is more brain tissue devoted to fingertip sensation. There may be special neural mechanisms devoted to high-resolution discrimination.
How are the afferent axons grouped and identified? Axons have different diameters which correspond to the types of sensory receptors to which they are attached.
axons from skin receptors are named Aa, AB, A8, and C;
axons of similar size from muscles are designated I, II, III, and IV-From largest to smallest.
The smallest group of axons are group ___ or ____ are ___ Group C or IV are unmyelinated. (Recall that unmyelinated, smaller in diameter axons are slower.)
Subcutaneous mechanoreceptors use larger ___ axons and conduct much _____ AB axons and conduct much faster.
.What are the segments of the spinal cord (FIGURE 12.10)? cervical, thoracic, lumbar, and sacral divisions. Cervical (C) 1-8, thoracic (T) 1-12, lumbar (L) 1-5, and sacral (S) 1-5.
.What are the three ascending touch pathways? (FIGURES 12.14, 12.15) Know the pathways. The Dorsal Column-Medial Lemniscal Pathway The Trigeminal Touch Pathway
What are the somatosensory regions of the cortex (FIGURE 12.16) occurs in the post central gyrus of the parietal lobe, which includes Brodmann’s area 3b (S1). Areas 5 and 7 in the posterior parietal cortex also process information, but area 3b is the primary somatic sensory cortex
Area 3a is concerned with sense ___. Areas 1 and 2 receive inputs from ___. Area __receives texture information and area __ receives size and shape information. Area 3a is concerned with sense of body position. Areas 1 and 2 receive inputs from 3b. Area 1 receives texture information and area 2 receives size and shape information.
area 3b is the primary somatic sensory cortex because: 1.It receives dense inputs from the VP nucleus of the thalamus 2.Its neurons are very responsive to somatosensory stimuli 3.Lesions here impair somatic sensations 4.Electrically stimulated, it evokes sensory experiences
.What causes “phantom limb” sensations? perception of sensations coming from the missing limb when other body parts are touched. These sensations are usually evoked by stimulation of skin regions whose somatotopic areas border those of the missing limb.
Why is pain a good thing? Pain teaches us to avoid harmful situations. It elicits withdrawal reflexes from noxious stimuli. It exhorts us to rest an injured part of our body.
.What kind of receptors are involved in pain? the free, branching, unmyelinated nerve endings that signal that body tissue is being damaged or is at risk of being damaged.Nociception is the sensory process that provides the signals that trigger pain.
.What are the three types of nociceptors? 1) Polymodal nociceptors: the majority of nociceptors that respond to mechanical, thermal, and chemical stimuli. 2) Mechanical nociceptors: showing selective responses to strong pressure.
.What are the three types of nociceptors? Cont' 3) Thermal nociceptors: showing selective responses to burning heat or extreme cold 4) Chemical nociceptors: showing selective responses to histamine and other chemicals
.What is hyperalgesia? a reduced threshold for pain, an increased intensity of painful stimuli, or even spontaneous pain. Primary hyperalgesia occurs within the area of damaged tissue, but secondary hyperalgesia in surrounding tissues may also occur
Why doesn’t the brain feel pain?
What roles do bradykinin,play in pain? Is one of the chemicals that directly depolarizes nociceptors. Also, stimulates long-lasting intracellular changes that make heat-activated ion channels more sensitive
What roles do prostaglandin play in pain? are chemicals generated by the enzymatic breakdown of lipid membrane. They do not elicit overt pain, they do increase greatly the sensitivity of nociceptors to other stimuli. Aspirin inhibits prostaglandin synthesis.
What roles do substance P play in pain? It causes vasodilation (swelling of the blood capillaries) and the release of histamine from mast cells. Sensitization of other nociceptors around the site of injury by substance P is one cause of secondary hyperalgesia.
.What types of fibers are involved in the first and second pain response to noxious stimuli? (Figure 12.25) The first pain sensation registered by noxious stimulation is mediated by fast A8 axons. The second, longer-lasting pain sensation is mediated by slow C fibers.
What are the differences between the ascending pathways of touch and pain? Figure 12.30 Information about touch ascends ipsilaterally, while information about pain (and temperature) ascends contralaterally.
How is touch and pain sensation affected on each side of the body when the spinal cord is damaged? (read page 414) If half of the spinal cord is damaged, certains deficits of mechanosensitivity occur on the same side as the spinal cord damage: insensitivity to light touch, the vibrations of a tuning fork on the skin, the position of a limb.
How is touch and pain sensation affected on each side of the body when the spinal cord is damaged? (read page 414) Deficits in pain and temperature sensitivity will show up on the side of the body opposite the cord damage.
In addition to the spinothalamic pathway, what are two other ascending pain pathways? Trigeminothalamic pathways..... AND??
How does the “Gate Theory of Pain” account for ablation of pain by simultaneous excitatory and inhibitory stimuli? in notes
What brain region is especially involved pain suppression in the descending pain pathway? (Figure 12.33) The PAG can influence the raphe nuclei of the medulla, which in turn can modulate the flow of nociceptive information through the dorsal horns of the spinal cord.
What are the endogenous pain suppressor drugs called? Opiates
What substances were used to identify hot and cold thermoreceptors? The active ingredient in hot peppers was used to identify the “hot” receptor protein called Trpv1. Mint was used to identify the “cold” receptor protein. Menthol, which produces a secsation of cold, was found to stimulate a receptor called Trpm8.
Compared the temperature pathway to the pain pathway. The organization of the temperature pathway is virtually identical to that of the pain pathway. Cold receptors are coupled to A8 and C fibers, while warm receptors are coupled only to C fibers.
.What are the two major types of muscles? Smooth: digestive tract, arteries, related structures Striated: Cardiac (heart) and skeletal (bulk of body muscle mass)
Voluntary vs involuntary Skeletal- voluntary (Striated) Cardiac- involuntary (striated) Smooth- involuntary
What are the three main segments of the spinal cord (slides 2 & 4, Figure 13.4) Cervical, thoracic, Lumbar
From which horn of the spinal cord do the mixed spinal nerves derive? The motor neurons that provide fivers to one spinal nerve are said to belong to a spinal segment, named for the vertebra where the nerve originates. The segments are cervical (C) 1-8, thoracic (T) 1-12, lumbar (l) 1-5, and sacral (S) 1-5.
How does this compare to the sensory input for touch & pain? (slide 3, figure 13.3) Lower motor neuron: innervated by ventral horn of spinal cord. Upper motor neurons of the brain that supply input to the spinal cord. Only the lower motor neurons directly command muscle contraction.
.What is the difference between a motor unit and a motor neuron pool? (slide 5) Motor unit – one alpha motor neuron and its muscle fibers Motor neuron pool – collection of alpha motor neurons that innervates a single muscle
What are the two main types of control of muscle contraction? (slide 6) (1) Varying the firing rate of motor neurons (2) Recruitment of additional synergistic motor neurons
.Understand the overall physiology of the neuromuscular junction. ON VIDEO
What are the three major sources of input to the alpha motor neurons? 1. spinal interneurons – largest input – may be excitatory or inhibitory 2. sensory input from muscle spindles - provides info about muscle length 3. input from upper motor neurons in the brain
Slow Motor Units Red (dark) Copious mitochondria Aerobic metabolism Sustain contraction for long time Small diameter neurons
Fast Motor Units Pale (white) Fewer mitochondria Anaerobic metabolism Contract rapidly, but fatigue quickly Large diameter neurons
What is the neurotransmitter used at the neuromuscular junctions? Nicotinic ACh receptor
What are some of the specialized characteristics of the muscle fiber? -T tubules conduct electrical activity from the surface membrane into the depths of the muscle fiber.
What are some of the specialized characteristics of the muscle fiber? Depolarization of the T tubule membrane causes conformational changes in proteins that are linked to calcium channels in the SR, releasing stored Ca2+ into the cytosol of the muscle fiber.
KNOW THE SLIDING FILAMENT MODEL OF MUSCLE CONTRACTION (PAGE 435) Read pages 432- 437, and know the terms.
.What are the steps involved in the excitation-contraction cycle? Excitation, contraction, relaxation
Excitation 1) An action potential occurs in an alpha motor neuron axon. 2) ACh is released by the axon terminal of the alpha motor neuron at the neuromuscular junction.
-Excitation: 3) Nicotinic receptor channels in the sarcolemma open, & the postsynaptic sarcolemma depolarizes (EPSP).
-Excitation: 4) Voltage-gated sodium channels open, and an action potential is generated in the muscle fiber, which sweeps down the sarcolemma into the T tublules. 5) Depolarization of the T tubules causes Ca2+ release from the sarcoplasmic reticulum.
Contraction -Contraction: 1) Ca2+ binds to troponin. 2) Myosin binding sites on actin are exposed. 3) Myosin heads bind actin. 4) Myosin heads pivot. 5) The cycle continues as long as Ca2+ and ATP are present.
Relaxation 1) As EPSPs end, the sarcolemma and T tubules return to their resting potentials. 2) Ca2+ is sequestered by the sarcoplasmic reticulum by an ATP-driven pump. 3) Myosin binding sites on actin are covered by troponin.
What is the structure & function of muscle spindles? in notes
How are muscle spindles “wired”? (slide 4, figure 13.23) -Muscle spindle wiring: Ia axons enter the dorsal roots, branch repeatedly “collaterals”, synapse on interneurons and alpha motor neurons.
What is the ratio of Ia axons to alpha motor neurons in a muscle? (slide 5) -A single Ia axon synapses on virtually every alpha motor neuron in the motor pool of the same muscle.
Describe the activation of alpha & gamma motor neurons in the muscle spindle, & the gamma loop. (slides 7-8, figure 13.19) -Gamma Motor Neurons: The muscle spindle contains modified skeletal muscle fibers within its fibrous capsule. These muscle fibers are called intrafusal fibers, to distinguish them from the more numerous extrafusal fibers.
Describe the activation of alpha & gamma motor neurons in the muscle spindle, & the gamma loop. (slides 7-8, figure 13.19) -Intrafusal Fibers in the muscle spindle are innervated by gamma motor neurons at both ends of the muscle spindle. -Extrafusal Fibers contract in response to alpha motor neurons.
Describe the activation of alpha & gamma motor neurons in the muscle spindle, & the gamma loop. (slides 7-8, figure 13.19) -Activation of gamma motor neurons causes contraction at both ends of the muscle spindle, so that the Ia axons don’t go slack. -The Gamma Loop: Gamma motor neuron-intrafusal fiber-Ia afferent axon-alpha motor neuron-extrafusal fibers.
Describe the myotatic reflex. (slide 9, figure 13.17) When a muscle is pulled, it tends to pull back (contract). Sometimes called the stretch reflex, it involves sensory feedback from the muscle. As a muscle is stretched, Ia sensory axons discharge rate goes up. As a muscle is shortened, the rate goes dow
What is meant by the “monosynaptic myotatic reflex arc”? (slide 10, figure 13.17) -The Ia axon and the alpha motor neurons on which it synapses constitute the monosynaptic myotatic reflex arc-“monosynaptic” because only one synapse separates the primary sensory input from the motor neuron output.
What is meant by the “monosynaptic myotatic reflex arc”? (slide 10, figure 13.17) When the muscle lengthens, the stretching of the equatorial region of the spindle depolarizes the Ia axon endings due to opening of the mechanosensitive ion channels. The Ia axon signals the alpha motor neurons, causing the muscle to contract.
What is the structure & function of the Golgi tendon organ? (slides 11-13, figure 13.21) -Ib input from Golgi tendon organs on alpha motor neurons is polysnaptic-mediated by intervening spinal interneurons. Most input to the alpha motor neurons comes from the interneurons.
What is the structure & function of the Golgi tendon organ? (slides 11-13, figure 13.21) Spinal interneurons receive synaptic input from: primary sensory neurons, descending axons from the brain, collaterals of lower motor neurons, and other unterneurons.
.What is the “reverse myotatic reflex”, some of these interneurons form inhibitory connections with the alpha motor neurons innervating the same muscle. In extreme cases, protects the muscle from being overloaded. Normal function is to regulate muscle tension within optimal range.
.what is its usual functionwhat types of motor skills does “reverse myotatic reflex”, mediate? As muscle tension increases, inhibition of the alpha motor neuron slows muscle contraction. As muscle tension falls, inhibition of the alpha motor neuron is reduced and muscle contraction increases.
What is the trigger for proprioceptors located in joints? (slide 15) in notes
What are the properties of spinal interneurons? (slide 16) -Ib input from Golgi tendon organs on alpha motor neurons is polysnaptic-mediated by intervening spinal interneurons.
What are the properties of spinal interneurons? (slide 16) Most input to the alpha motor neurons comes from the interneurons. Spinal interneurons receive synaptic input from: primary sensory neurons, descending axons from the brain, collaterals of lower motor neurons, and other unterneurons.
What are the differences between the myotatic reflex and the flexor reflex? -Flexor Reflex: complex reflex arc used to withdraw limb from aversive stimulus. Slower than the myotatcic reflex, indicating interneuron involvement. Pain axons branch profusely and synapse on numerous interneurons.
How does reciprocal inhibition occur & what are some examples? Contraction of one set of muscles accompanied by the relaxation of the antagonistic muscles. It occurs because collaterals of the Ia axons synapse on inhibitory spinal interneurons that contact the alpha motor neurons of the antagonistic muscles.
.what are some examples of reciprocal inhibition? (slide 18-19, figure 13.23) Lifting an object, myotatic reflex- to override the myotatic reflex, descending pathways synapse on inhibitory interneurons to the antagonistic muscles,
.what are some examples of reciprocal inhibition? (slide 18-19, figure 13.23) lifting on leg- activation of inhibitory interneurons that decussate to the other side of the spinal cord-called crossed extensor reflex.
What is the crossed-extensor reflex the activation of extensor muscles and the inhibition of flexors on the opposite side. used to compensate for the extra load imposed by limb withdrawal on the antigravity extensor muscles of the opposite leg.
what component is lacking from the crossed-extensor reflex compared to the motor program for walking? The only element that is lacking in the crossed-extensor reflex is coordination of timing.
Describe the cycle of central pattern generators. Circuits that give rise to rhythmic motor activity. The simplest are individual neurons whose membrane properties confer pacemaker qualities. Stimulation of NMDA receptors on spinal motor neurons is sufficient to generate this locomotor activity.
Describe the cycle of central pattern generators. (Recall that NMDA receptors are voltage-gated receptors that have Mg2+ bound to the ion channel, depolarization of the membrane is required before NMDA receptors are activated, and NMDA receptors admit both Na+ and Ca2+ ions.
Describe the cycle of central pattern generators. Spinal interneurons also possess calcium activated potassium channels.
Created by: katie.nelson8