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 movem...

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 movement 13.2 Autonomic reflexes ◦ 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 integration Brain Spinal cord Innate or learned? Innate Learned Number of synapses Monosynaptic Polysynaptic For polysynaptic reflexes divergence/convergence allows: Single stimulus Integration of effects multiple input from targets multiple sources Neural reflexes 3 Classification of Reflexes 4  Visceral Components 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 May be tonic control neuron Target Autonomic Number of synapses? cell ganglion Autonomic reflexes: structural components of a reflex arc 5  Visceral Components of autonomic reflexes Integration may occur in ◦ Spinal cord Sensory Stimulus Receptor ◦ Hypothalamus neuron ◦ Thalamus CNS ◦ Brainstem integrating center ◦ Limbic system Integration may lead to ◦ Excitement Preganglionic autonomic ◦ Inhibition Response neuron Postganglionic autonomic neuron Target Autonomic cell ganglion Autonomic reflexes: structural components of a reflex arc 6  Visceral Classifying autonomic reflexes Regulate ◦ Homeostasis Sensory Stimulus Receptor ◦ Heart rate neuron ◦ Blood pressure ◦ Breathing CNS integrating ◦ Water balance center ◦ Body temperature ◦ Salivating ◦ Swallowing Preganglionic ◦ Gagging Response autonomic neuron ◦ Coughing Postganglionic autonomic ◦ Sneezing Target neuron Autonomic cell ◦ 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 Stimulus ◦ Ruffinian corpuscles (slow changes) 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 Skeletal muscle reflexes 8  Components of a somatic (skeletal muscle) reflex Cerebellum is primary site for integration of sensory info from joints Interneurons Spinal ◦ Excitatory Stimulus Receptor Sensory neuron cord integrating ◦ Inhibitory Synapse 1 center Interneuron Synapse 2 Somatic alpha motor neuron ◦ Tonic output yields tone Target Efferent Response cell neuron Extrafusal muscle fiber ◦ Excited or not excited Skeletal 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 Skeletal 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 Skeletal 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 cord alpha motor neurons sensory neuron decreases. Negative feedback Skeletal 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 of Integrating center: Sensory neuron pathways controlling a joint synapses in Muscle spindle spinal cord. § Includes Stimulus ◦ Synergists ◦ Antagonists Classify the… Somatic alpha motor neuron onto ◦ 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 Skeletal 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 ◦ Withdrawal of ipsilateral limb Sensory neuron Ascending pathways to brain 3a 3b ◦ Extension of contralateral limb – – ◦ Crossed extensor 3c Nociceptor 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. Skeletal 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 Integrated 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) ◦ Decision making & planning ◦ Initiating movement Ascending tract Integrated 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? Integrated 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 movement Red = upper motor ◦ Dopaminergic neurons begin in basal neuron nuclei White = lower motor neuron ◦ Basal nuclei including substantia nigra (midbrain) commonly impacted in Parkinson’s disease MIDBRAIN ◦ Three major motor symptoms Cranial nerves to selected Motor nuclei ◦ Tremors skeletal muscles of cranial nerves ◦ Slow movements (freezing) MEDULLA OBLONGATA ◦ Rigidity Most corticospinal pathways decussate Pyramids Lateral corticospinal tract Anterior corticospinal tract Somatic motor neurons to SPINAL CORD Integrated 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 Control of visceral muscle movement 22