Term
| 2 types of lower motor neurons |
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Definition
1. alpha motoneurons (innervating the extrafusal muscle fibers)
2. gamma motoneurons (supplying the muscles spindles) |
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Term
| How are the motoneurons arranged in the spinal cord? |
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Definition
| columns (each column supplies one or a few muscles with synergetic actions) |
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Term
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Definition
| an alpha motoneurons & all the muscle fibers it innervates |
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Term
| 2 types of muscle fibers (according to ATPase activity) |
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Definition
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Term
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Definition
| an involuntary response to a stimulus (mediated by the nervous system) |
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Term
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Definition
1. receptors that capture the stimulus
2. sensory neurons conducting signals to the CNS
3. a reflex centrum
4. an effector |
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Term
| 2 main kinds of stretch reflexes |
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Definition
1. monosynaptic stretch reflex
2. polysynaptic, long-latency stretch reflex |
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Term
| Can peripheral nerves regenerate after severance? |
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Definition
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Term
| peripheral motor neurons (lower motor neurons) |
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Definition
| nerve cells that send their axons to skeletal muscles |
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Term
| What is the path of the axons of the motoneurons when they leave the spinal cord? |
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Definition
| they leave through the ventral roots & continue into the ventral & dorsal branches of the spinal nerves to innervate skeletal muscles of the trunk & the extremities |
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Term
| cranial nerve motor nuclei |
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Definition
| cells that have axons that supply the muscles of the tongue, pharynx, palate, larynx, & face (also the extraocular muscles) |
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Term
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Definition
| formed by the ventral branches of the spinal nerves so that the motor axons from one spinal segment are distributed to several peripheral nerves |
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Term
| What makes up the final common path for all signals from the CNS to skeletal muscles? |
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Definition
| the peripheral motor neurons |
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Term
| What neurotransmitter is used by motoneurons? |
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Definition
| ACh (also have the synthesizing enzyme "choline acetyltransferase") |
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Term
| What neuropeptide is used by motoneurons? |
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Definition
| calcitonin gene-related peptide (CGRP) |
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Term
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Definition
| groups of the motoneurons in the spinal cord |
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Term
| What will result from destruction of one root or spinal nerve only (ex. by disk protrusion in sciatica or by a tumor growing in the spinal cord)? |
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Definition
| a more or less pronounced paresis (not paralysis of the muscle) |
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Term
| What is the difference in location between groups of motoneurons that supply axial muscles (back, neck, abdomen, & pelvis) & groups that supply muscles of the extremities? |
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Definition
axial: located most medially within the ventral horn
extremities: more laterally |
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Term
| What is the difference in location between motoneurons supplying proximal muscles of the extremities & those that supply the distal muscles? |
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Definition
proximal: more ventral
distal: more dorsal |
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Term
| What do the smallest alpha motoneurons control? |
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Definition
| delicate movements with little force (larger motoneurons come into play only when a movement requires great force) |
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Term
| Do large or small alpha motoneurons have a higher maximal firing frequency? |
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Definition
| large (they tend to fire in brief bursts with a high frequency whereas the small alpha motoneurons tend to go on firing for a long time with low frequency) |
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Term
| What do the differences in firing pattern between large & small alpha motoneurons signify? |
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Definition
large: used for forceful, rapid movements of short duration
small: uphold a moderate muscular tension for a long time |
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Term
| Are large or small alpha motoneurons phasic? Which are tonic? |
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Definition
phasic = large
tonic = small |
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Term
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Definition
| formed where branches end on the muscle cell approximately midway between its ends; where the signal transfer from nerve to muscle takes place |
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Term
| 2 things intercalated between the presynaptic & postsynaptic membranes of the neuromuscular junction? |
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Definition
1. junctional folds
2. a thin basal lamina |
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Term
| What type of ACh receptors exist on the postsynaptic membranes of NMJs? |
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Definition
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Term
| During embryonic development (before the nerve fibers growing out from the cord have reached the muscle cells), how are the ACh receptors distributed on the muscle membrane? |
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Definition
| they are evenly distributed all over the muscle membrane |
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Term
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Definition
| a neuropeptide expressed by spinal motoneurons during development that influences the synapse formation at the motor end plate |
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Term
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Definition
| the enzyme that rapidly terminates the action of ACh by degrading it |
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Term
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Definition
| a brief contraction elicited by a single presynaptic action potential at the motor end plate of the muscle cell |
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Term
| What is the force produced by the muscle cell determined by? |
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Definition
| the firing frequency of the motoneuron |
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Term
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Definition
| the muscle response to a train of signals with the highest frequency to which the muscle cell can respond (kind of the opposite of how the twitch is the response of the muscle cell to a single nerve nuclei) |
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Term
| Do some muscles have a different color than others? |
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Definition
| yes! ("red" muscles vs "white" muscles) |
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Term
| What is the color difference in muscles due to? |
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Definition
| the content of myoglobin (red substance that transports oxygen within the muscle cell) |
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Term
| Do white & red muscle cells differ with regard to endurance (how long they can maintain tension)? |
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Definition
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Term
| Why do red & white muscle cells differ with regard to endurance? |
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Definition
| they have differing capacities to take up oxygen & to aerobic ATP production |
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Term
| Are red or white muscle fibers associated with fast twitch? Which are associated with slow twitch? |
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Definition
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Term
| What are the differences in contraction velocity & maximal force development related to in red vs white muscles? |
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Definition
| the amount & type of myosin ATPase |
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Term
| 2 types of type 2 muscle fibers |
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Definition
1. type 2A (resemble the type 1 fibers in having a relatively high oxidative capacity)
2. type 2B (the most typical white fibers with low oxidative capacity) |
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Term
| Can the CNS select muscle fibers in accordance with the requirement of the task? |
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Definition
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Term
| Would type 1 or type 2 fibers be better for athletes who engage in endurance sports? What about those who engage in sports that require explosive force? |
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Definition
endurance = type 1
explosive force = type 2 |
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Term
| Do muscle cells belonging to different motor units lie intermingled in the muscle? |
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Definition
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Term
| Are muscle cells belonging to the same motor unit all of the same fiber type? |
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Definition
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Term
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Definition
| when more & more motor units (thus muscle fibers) are called into action |
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Term
| Who demonstrated the size principle of recruitment? |
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Definition
| American neurophysiologist E. Henneman (in the 1960s) |
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Term
| What does it mean that reflexes are "inborn"? |
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Definition
| we do not need to learn them from experience |
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Term
| Can reflexes be suppressed voluntarily, despite being independent of our will? |
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Definition
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Term
| Are true reflexes the same thing as conditioned reflexes (AKA conditioned responses)? |
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Definition
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Term
| What part of the brain is important for conditioning of movements (such as the blink reflex) and also movements of skeletal muscles? |
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Definition
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Term
| 2 reflexes only present during the infant phase of development |
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Definition
1. sucking reflex
2. grasping reflex |
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Term
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Definition
| reflexes with their reflex center in the spinal cord |
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Term
| What is the difference between brain stem reflexes & cortical reflexes? |
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Definition
brain stem: have their center in the medulla, pons, or mesencephalon
cortical: have a reflex center that involves parts of the cerebral cortex |
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Term
| Can the excitability of the neurons that mediate a given reflex response be modified from higher levels of the CNS? |
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Definition
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Term
| 3 ways modulation of the excitability of the reflex center can be exerted |
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Definition
1. presynaptic inhibition of primary afferent fibers
2. postsynaptic excitatory of inhibitory action on interneurons & motoneurons
3. efferent control of the sensitivity of some kinds of receptor |
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Term
| Can the strength of a response (even when the stimulus is kept constant) vary from person to person or time to time for the same person? |
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Definition
| yes! (ex. level of anxiety can affect it) |
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Term
| What is the gain of a reflex associated with? |
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Definition
| the overall need of the organism |
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Term
| During learning of a motor task, can the strength of the monosynaptic reflex response be strengthened or weakened according to what is functionally appropriate? |
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Definition
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Term
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Definition
| when stretching a muscle leads to excitation of the alpha motoneurons innervating the muscle; happens simultaneously with the inhibition of the motoneurons of the antagonists |
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Term
| What does reciprocal inhibition prevent? |
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Definition
| unwanted oscillatory movements |
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Term
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Definition
| disturbed functioning of spinal inhibitory interneurons |
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Term
| Ia-inhibitory interneurons |
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Definition
| mediate the inhibition of the alpha motoneurons of the antagonist; excited by Ia afferents from the agonist muscles |
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Term
| What is the task of the stretch reflex? |
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Definition
| the ensure that the length of a muscle is kept constant |
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Term
| When is the stretch reflex important during slow, precise voluntary movements? |
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Definition
| when the external opposing forces change unpredictably |
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Term
| Can stimulation of low-threshold skin mechanoreceptors cause reflex muscular contraction? |
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Definition
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Term
| What mediates gain modulation of the stretch reflex? |
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Definition
| descending connections from higher levels of the CNS |
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Term
| Can presynaptic inhibition very selectively "switch off" the input from specific sets of receptors? |
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Definition
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Term
| Is the gain of the flexion reflex under supraspinal control? |
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Definition
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Term
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Definition
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Term
| What most markedly alters the muscle tone? |
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Definition
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Term
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Definition
| elastic molecules of the cytoskeleton that connect the Z discs within the myosin filaments |
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Term
| Can crossbridges between actin & myosin filaments exist in a relaxed muscle? |
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Definition
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Term
| 2 substances whose amount & composition contributes to individual differences in muscle tone |
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Definition
1. connective tissue
2. ECF |
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Term
| 3 diseases that can cause cramps |
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Definition
1. neuropathies
2. amyotrophic lateral sclerosis (ALS)
3. vascular diseases |
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Term
| What causes writer's cramp? |
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Definition
| a task-specific focal dystonia of the hand |
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Term
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Definition
| abnormally increased muscle tone; implies that the muscles continuously have an increased tone in spite of attempts to relax |
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Term
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Definition
| when all motoneurons supplying a muscle are destroyed & the muscle cannot be made to contract |
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Term
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Definition
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Term
| What is the difference between peripheral paralysis & central paralysis? |
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Definition
peripheral: muscle weakness caused by the loss of the alpha motoneurons or their axons (lower motor neurons)
central: caused by interruption of the central motor pathways |
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