Pre Class 13 Control of Movement Sp22 PDF

Muscle & Movement PHSL 3051 Dr. Barnett Control of Movement Pre Class 13 Learning Objectives Class 13: The Somatic Nervous System: Control of Movement | Smooth Muscle Derrickson (1st edition: p. 356-359, 412-428, 396-404,2nd edition: p. 425-437, 411-419) 1. Compare and contrast t...

Muscle & Movement PHSL 3051 Dr. Barnett Control of Movement Pre Class 13 Learning Objectives Class 13: The Somatic Nervous System: Control of Movement | Smooth Muscle Derrickson (1st edition: p. 356-359, 412-428, 396-404,2nd edition: p. 425-437, 411-419) 1. Compare and contrast the organization of the somatic nervous system versus the autonomic nervous system. 2. Compare and contrast the structure, anatomical location, and function of muscle spindles and Golgi tendon organs. 3. Describe the series of events initiated by striking the patellar tendon with a percussion hammer that leads to extension of the lower leg (i.e. the knee jerk reflex) 4. Describe the properties of the withdrawal reflex initiated by stepping on a sharp object. 5. List the regions of the brain involved in middle level of motor control and describe the main function that these structures serve. 6. Describe the function of higher centers in motor control. 7. Compare how smooth muscle activation and relaxation differs from the activation and relaxation of skeletal muscle. 8. List the potential sources of calcium that may contribute to smooth muscle activation 2  TABLE 10.5 Comparison of the Autonomic and Somatic Nervous Systems Autonomic Nervous System Somatic Nervous System Effectors Smooth muscle, cardiac muscle, and glands. Skeletal muscle. Motor neuron pathway Usually a two-neuron pathway: (1) a preganglionic neuron One-neuron pathway: a single that extends from CNS to an autonomic ganglion and (2) a somatic motor neuron extends from postganglionic neuron that extends from the autonomic the CNS to synapse directly with the ganglion to the effector. Alternatively, a preganglionic neuron effector. may extend from CNS to synapse with chromaffin cells of the adrenal medulla. Neurotransmitters Most autonomic motor neurons release either acetylcholine All somatic motor neurons release (ACh) or norepinephrine (NE). Chromaffin of the adrenal ACh. medulla releases epinephrine and NE into bloodstream as hormones. Receptor type on effector Usually cholinergic or adrenergic. Cholinergic organ Action of neurotransmitter May be excitatory (causes contraction of smooth muscle, Always excitatory (causes on effector increases rate and force of contraction of cardiac muscle, or contraction of skeletal muscle). increases secretions of glands) or inhibitory (causes relaxation of smooth muscle, decreases rate and force of contraction of cardiac muscle, or decreases secretions of glands). Control of motor output Involuntary control from hypothalamus, brain stem, and spinal Voluntary control from cerebral cord. cortex, with contributions from the basal nuclei, cerebellum, brain stem, and spinal cord. COPYRIGHT © 2019 BY JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 4 Four Sources Of Input To Lower Motor Neurons Somatic motor neurons are also referred to as lower motor neurons Axons of lower motor neurons extend from cranial nerves to innervate skeletal muscles of the face and head and from spinal nerves to innervate skeletal muscles of the limbs and trunk Highest Level of Control Sensory, motor and 2 Upper motor neurons from Intention to move, etc. association cortex cerebral cortex Integration of sensory feedback 3 Basal nuclei Thalamus Middle Level of Control Motor programs to coordinate 4 Cerebellum movements based on intention, sensory feedback, etc. Motor centers Upper motor in brain stem 2 neurons from brain stem Lowest Level of Control 1 Local circuit neurons in Input from sensory neurons, local brain stem and spinal interneurons, etc. cord Lower motor neurons (final common Because lower motor α-motor neurons pathway) neurons provide all output Neural circuits that regulate lower motor neurons. to skeletal muscles, they cell bodies are in the Lower motor neurons receive inputs directly from 1 local circuit brain stem and are called the final common pathway. neurons (purple arrow) and 2 upper motor neurons in the spinal cord Skeletal muscles cerebral cortex and brain stem (green arrows). Neurons in the basal nuclei 3 and cerebellum 4 regulate activity of upper motor neurons (red arrows). Based on Derrickson Fig.12.1 5 Local Level of Motor Control: Somatic Reflex Arcs Sensory Neuron  Peripheral Receptor Interneuron  Relays sensory information Somatic Motor Neuron  Integrating center and effector control Effector  Skeletal Muscle Communication pathways from peripheral sensors that provide direct inputs to the local motor control centers as well as the higher centers of motor control Includes responses to pain (nociceptors), length changes of muscle (muscle spindles), and excessive muscle tension (tendon organs) Facilitates a faster response to changes in the environment May result in either excitation or inhibition of α motor neurons 6 Wu’s Rule A Reflex Arc has 7 Elements 1. A Stimulus 2. A Receptor or Sensor Stimulus 1 3. An Afferent Signaling Pathway 4 3 2 4. An Integrating Center (Integrator) 5 7 5. An Efferent Signaling Response 6 Pathway 6. An Effector 7. A Response 7 Examples of Sensory receptors that trigger skeletal muscle reflex responses Muscle Spindles (intrafusal muscle fibers) Small specialized muscle cells that have a central non- contractile region flanked by contractile end regions. There are two sub-types: nuclear chain fibers nuclear bag fibers Spindles are embedded in muscle groups in the body and experience length changes based on the activity of the stretches and contractions of the muscle groups they inhabit. The spindles are wrapped by the nerve endings of sensory afferents which change their firing pattern based on these changes in muscle length. The contractile end domains of each spindle are innervated by gamma motor neurons. Golgi Tendon Organs Connective tissue capsules that associate with the tendons that anchor skeletal muscles in the body. The capsules contain the sensory nerve endings and intertwine with collagen fibers of the tendon. The signaling pattern of the sensory afferents depends on the tension experienced by the tendon due to muscle contraction or external loads. 8 Sensory receptors in skeletal muscle α-γ Continued Stretched Contraction Coactivation Contraction Muscle Spindle Sensory Neuron α-Motor Neuron Signaling to extrafusal muscle fibers γ-Motor Neuron Signaling to intrafusal muscle fibers 9 Local Level of Motor Control: Knee Jerk Reflex Muscle Spindle Stretch Reflex Causes contraction of a muscle in response to the muscle stretching – controls muscle length. Monosynaptic reflex arc Can be elicited by tapping on tendons attached to muscles at elbow, wrist, knee, and Contraction of the opposing ankle joints (patellar (knee muscle is inhibited through a jerk) reflex) polysynaptic reflex arc - This is termed reciprocal innervation Sensory input enters the spinal cord on the same side from which motor output leaves (ipsilateral reflex). 10 Muscle Spindle Reflex Arc Reflex Arc Muscle Spindle Elements Reflex Elements 3 4 1. Stimulus 1. Muscle Stretch 6 2. Receptor/ Sensor 5 2. Muscle Spindles 3. Afferent 3. Muscle Spindle Afferents 2 1 4. Integrating Center 4. Spinal Cord (Integrator) 5. Somatic Motor Neurons 5. Efferent 6. Skeletal Muscles 6. Effector 7. Muscle Contraction 7 7. Response 11 Local Level of Motor Control: Excess Tension Reflex Golgi Tendon Organ Reflex Causes muscle relaxation in response to too much tension – regulates muscle tension Monosynaptic reflex arc As tension on the tendon organ increases, the frequency of inhibitory action potentials increases Ipsilateral reflex arc Protects the tendon and muscle from damage due to excessive tension The opposing muscle is activated (contracts) through a polysynaptic reflex 12 Excess Tension Reflex Arc Golgi Tendon Organ Reflex Reflex Arc Muscle Spindle Elements Reflex Elements 1. Stimulus 1. __________________ 2. Receptor/ Sensor 2. __________________ 3. Afferent 3. __________________ 4. Integrating Center 4. __________________ (Integrator) 5. __________________ 5. Efferent 6. __________________ 6. Effector 7. __________________ 7. Response 13 Local Level of Motor Control: Withdrawal Reflex (Flexor Reflex) Involves Pain Receptors Causes flexion (bending) of a limb to withdraw from a painful stimulus Ipsilateral reflex arc Polysynaptic reflex arc – to move a limb requires contraction of more than one muscle group Action Potentials from a single sensory neuron ascend and descend in the spinal cord and activate interneurons in several spinal cord segments – intersegmental reflex 14 Local Level of Motor Control: Withdrawal Reflex (Crossed Extensor Reflex) Causes an extension of the opposite limb Crossed Extensor Reflex during a flexor reflex Withdrawal Reflex to help maintain balance Causes contraction in the unstimulated limb Polysynaptic reflex arc Contralateral reflex arc – sensory inputs enter one side of the spinal cord and motor outputs exit on the opposite side of the spinal cord