BIO 305 Chapter 13 Reflexes Student Copy PDF

Control of Body Movement CHAPTER 13 1 Body movement overview 13.1 Neural reflexes 13.4 Integrated control ◦ Classification ◦ Reflexes ◦ Definition: the integration of ◦ Voluntary movement sensory information into an ◦ Rhythmic movement i...

Control of Body Movement CHAPTER 13 1 Body movement overview 13.1 Neural reflexes 13.4 Integrated control ◦ Classification ◦ Reflexes ◦ Definition: the integration of ◦ Voluntary movement sensory information into an ◦ Rhythmic movement involuntary response 13.5 Visceral muscle 13.2 Autonomic reflexes movement ◦ Differences 13.3 Skeletal muscle reflexes ◦ Proprioceptors ◦ Subsets of ◦ Motor neurons ◦ Muscle fibers 2  Classifying neural reflexes Classification Options Efferent division Somatic Autonomic Location of Brain Spinal cord integration Innate or learned? Innate Learned Number of Monosynaptic Polysynaptic synapses For polysynaptic reflexes divergence/convergence allows: Single Integration of stimulus input from effects multiple multiple sources targets Neural reflexes 3 Classification of Reflexes 4  Components Visceral of autonomic reflexes Many types of receptors: Osmoreceptors Sensory Stimulus Receptor neuron Chemoreceptors Baroreceptors CNS integrating Touch receptors center Thermoreceptors Special senses Preganglionic autonomic Response neuron Postganglionic autonomic neuron May be tonic control Target cell Autonomic ganglion Number of synapses? Autonomic reflexes: structural components of a reflex arc 5  Components Visceral of autonomic reflexes Integration may occur in ◦ Spinal cord Sensory Stimulus ◦ Hypothalamus Receptor neuron ◦ Thalamus CNS ◦ Brainstem integrating center ◦ Limbic system Integration may lead to ◦ Excitement Preganglionic autonomic ◦ Inhibition Response neuron Postganglionic autonomic neuron Target cell Autonomic ganglion Autonomic reflexes: structural components of a reflex arc 6  Classifying Visceral autonomic reflexes Regulate ◦ Homeostasis Sensory Stimulus Receptor ◦ Heart rate neuron ◦ Blood pressure ◦ Breathing CNS integrating ◦ Water balance center ◦ Body temperature ◦ Salivating ◦ Swallowing Preganglionic ◦ Gagging autonomic neuron Response ◦ Coughing Postganglionic autonomic ◦ Sneezing Target neuron cell Autonomic ◦ Vomiting ganglion Autonomic reflexes 7  Components of a somatic (skeletal muscle) reflex Receptors are Proprioceptors ◦ Joint receptors ◦ Stimulated by mechanical distortion ◦ Pacinian corpuscles (fast changes) Spinal Receptor Sensory cord ◦ Ruffinian corpuscles (slow changes) Stimulus neuron integrating center ◦ Golgi tendon organs Synapse 1 Interneuron ◦ Stimulated by muscle tension Synapse 2 ◦ Muscle spindles Target Efferent ◦ Stimulated by stretch (stretch receptors) Response cell neuron keletal muscle reflexes 8  Components of a somatic (skeletal muscle) reflex Cerebellum is primary site for integration of sensory info from joints Interneurons Stimulus Receptor Sensory neuron Spinal cord integrating ◦ Excitatory Synapse 1 center ◦ Inhibitory Interneuron Synapse 2 Somatic alpha motor neuron Target Efferent ◦ Tonic output yields tone Response cell neuron Extrafusal muscle fiber ◦ Excited or not excited keletal muscle reflexes 9  The Golgi tendon organ Free nerve endings stimulated by tension ◦ Squeezed during contractions ◦ Provide feedback ◦ Maintain posture ◦ Know where body is during movement Extrafusal muscle fibers Capsule Sensory neuron Extrafusal muscle fibers Collagen Golgi tendon organ fiber Tendon Tendon keletal muscle reflexes 10  Muscle spindles Extrafusal muscle fibers stimulated by alpha motor neurons Modified intrafusal muscle fibers: ◦ Sensory receptors that are stimulated by stretch ◦ Stimulated by gamma motor neurons Gamma motor neurons To CNS Tonically active sensory neurons Alpha motor neuron Central region Gamma motor neurons Extrafusal muscle fibers Muscle spindle Intrafusal fibers Tendon Extrafusal fiber keletal muscle reflexes 11  Muscle spindles during stretch Sensory neuron Spinal Spindle cord Motor neuron Muscle Add load 2 3 Protects from Muscle Increased afferent signals Spinal Increased efferent output through Muscle Firing rate of afferent contracts overstretching stretch to spinal cord sensory alpha motor cord neuron neurons decreases. Negative feedback keletal muscle reflexes 12  A stretch reflex = patellar reflex Monosynaptic- little delay between sensory input and motor output 13  Controlling movement at joints Sensory neuron Myotactic unit is the collection Integrating center: Sensory neuron of pathways controlling a joint synapses in Muscle spindle spinal cord.  Includes Stimulus ◦ Synergists ◦ Antagonists Classify the… Somatic alpha onto motor neuron ◦ Stretch reflex ◦ Reciprocal inhibition reflex Effector 1: Quadriceps muscle Interneuron inhibiting somatic alpha motor neuron Response: Stretch reflex Effector 2: Hamstring muscle Response: Reciprocal inhibition keletal muscle reflexes 14  Flexion (withdrawal) Reflex Withdrawal reflex (flexor) = Move affected parts of the body away from a stimulus 15  Flexion (Withdrawal) Reflex Gray matter Spinal cord Divergence allows Spinal cord White matter 2 ◦ Contraction versus relaxation Sensory neuron Ascending pathways ◦ Withdrawal of ipsilateral to brain limb 3b 3a – – ◦ Extension of contralateral 3c limb Nociceptor ◦ Crossed extensor Alpha motor Painful neurons stimulus 1 Extensors inhibited. Extensors contract as Flexors contract, weight shifts to left leg. moving foot away from painful stimulus. Flexors inhibited. keletal muscle reflexes 16 Crossed Extensor Reflex  Postural reflex that helps maintain balance when one foot is lifted from the ground  Lifting left foot requires extension of right leg to maintain one’s balance  If step on tack, signals cross to opposite spinal cord  Contralateral extensor muscles are stimulated by interneurons to hold up the body weight 17  Levels of motor control Spinal cord ◦ Central pattern generators ◦ Interneurons that maintain repetitive activity ◦ Quiet breathing ◦ Walking/Running ◦ Reflexes ◦ Least complex are integrated in spinal cord ◦ May be modulated by input from higher brain centers tegrated control of body movement 18  Levels of motor control Voluntary movements require coordination between the cerebral cortex, cerebellum and basal nuclei Cerebellum ◦ Postural reflexes/balance ◦ Hand and eye movements Cerebral cortex + basal nuclei (ganglia) Ascending ◦ Decision making & planning tract ◦ Initiating movement tegrated control of body movement 19  Where exactly are the basal nuclei? Corpus callosum Lateral ventricle Septum pellucidum Basal nuclei Lateral sulcus Insula Anterior commissure Tip of inferior horn of lateral Amygdaloid body ventricle Why is basal “ganglia” inaccurate? tegrated control of body movement 20  Voluntary movements utilize the corticospinal tract Primary motor cortex of left cerebral hemisphere Extra-pyramidal tracts (neurons of the basal nuclei) also influence Red = upper motor movement neuron ◦ Dopaminergic neurons begin in White = lower motor basal nuclei neuron ◦ Basal nuclei including substantia nigra (midbrain) commonly impacted in Parkinson’s disease MIDBRAIN Cranial nerves to selected Motor nuclei ◦ Three major motor symptoms skeletal muscles of cranial nerves ◦ Tremors MEDULLA OBLONGATA ◦ Slow movements (freezing) Most corticospinal ◦ Rigidity pathways decussate Pyramids Lateral corticospinal tract Anterior corticospinal tract Somatic motor neurons to SPINAL CORD tegrated control of body movement skeletal muscles 21  Differences in control of visceral muscles Cardiac and smooth muscle are not connected to bones ◦ Broader range of movements Typically contract to move lumenal contents May be controlled by ◦ Internal pacemaker ◦ Intrinsic gap junctions ◦ ANS ◦ Hormones ntrol of visceral muscle movement 22