Transcript File
Objective: I can explain the parts of the spinal and reflexes. Agenda: 1. Nervous System Quiz 2. Notes over Spinal Cord and Reflexes 3. Spinal Cord Virtual Labeling Spinal Meninges Three membranes surround all of CNS 3) Pia mater 1) Dura mater - "tough 2) Arachnoid mother", strong 2) Arachnoid meninx spidery looking, carries blood vessels, etc. Subarachnoid space 3) Pia mater - "delicate mother", adheres tightly to surface of spinal cord 1) Dura mater Sectional anatomy of the spinal cord White matter is myelinated and unmyelinated axons Gray matter is cell bodies, unmyelinated axons and neuroglia Projections of gray matter toward outer surface of cord are horns The Sectional Organization of the Spinal Cord Organization of Cord Cross Section Gray matter - interior horns posterior - somatic and visceral sensory nuclei anterior (and lateral) gray horns – somatic and visceral motor control gray commissures - axons carrying information from side to side White matter - tracts or columns posterior white column anterior white column lateral white column anterior white commissure functions ascending tracts - sensory toward brain descending tracts - motor from brain Fig 14-5 Horns of spinal cord Posterior gray horn contains somatic and visceral sensory nuclei Anterior gray horns deal with somatic motor control Lateral gray horns contain visceral motor neurons Gray commissures contain axons that cross from one side to the other Peripheral Nerves Definition: bundles of axons. AKA tracts in CNS Organization – coverings: Epineurium wraps entire nerve Perineurium wraps fascicles of tracts Endoneurium wraps individual axons 31 pairs of spinal nerves Nerves consist of: Epineurium Perineurium Endoneurium Spinal nerves White ramus (myelinated axons) Gray ramus (unmyelinated axons that innervate glands and smooth muscle) Dorsal ramus (sensory and motor innervation to the skin and muscles of the back) Ventral ramus (supplying ventrolateral body surface, body wall and limbs) Each pair of nerves monitors one dermatome Anatomy of a Peripheral nerve Function: sensory - afferent motor - efferent mixed - contains axons of both Dermatomes Sensory innervations by specific spinal nerves Each pair of spinal nerves monitors specific region of body surface. Clinical significance ? Nerve plexus Complex interwoven network of nerves Four large plexuses Cervical plexus Brachial plexus Lumbar plexus Sacral plexus Peripheral Nerves and Nerve Plexus The Brachial Plexus The Branchial Plexus The Branchial Plexus The Lumbar and Sacral Plexuses The Lumbar and Sacral Plexuses STOP Objective: I can explain the parts of the spinal and reflexes. Agenda: 1. Notes over Reflexes 2. Spinal Cord Virtual Labeling 3. Reflexes Lab 4. Exit Ticket An introduction to reflexes Reflexes are rapid automatic responses to stimuli Neural reflex involves sensory fibers to CNS and motor fibers to effectors Reflex arc Wiring of a neural reflex Five steps Arrival of stimulus and activation of receptor Activation of sensory neuron Information processing Activation of motor neuron Response by effector Components of a Reflex Arc Reflex classification According to development Site of information processing Nature of resulting motor response Complexity of neural circuit Methods of Classifying Reflexes reflex classifications Innate reflexes Result from connections that form between neurons during development Acquired reflexes Learned, and typically more complex More reflex classifications Cranial reflexes Reflexes processed in the brain Spinal reflexes Interconnections and processing events occur in the spinal cord still more reflex classifications Somatic reflexes Control skeletal muscle Visceral reflexes (autonomic reflexes) Control activities of other systems and more reflex classifications Monosynaptic reflex Sensory neuron synapses directly on a motor neuron Polysynaptic reflex At least one interneuron between sensory afferent and motor efferent Longer delay between stimulus and response Neural Organization and Simple Reflexes Spinal Reflexes Range from simple monosynaptic to complex polysynaptic and intersegmental Many segments interact to form complex response Monosynaptic Reflexes Stretch reflex automatically monitors skeletal muscle length and tone Patellar (knee jerk) reflex Sensory receptors are muscle spindles Postural reflex maintains upright position Components of the Stretch Reflex The Patellar Reflex Intrafusal Fibers Polysynaptic reflexes Produce more complicated responses Tendon reflex Withdrawal reflexes Flexor reflex Crossed extensor reflex The Flexor and Crossed Extensor Reflexes Polysynaptic reflexes Involve pools of interneurons Are intersegmental in distribution Involve reciprocal inhibition Have reverberating circuits to prolong the motor response Several reflexes may cooperate to produce a coordinated response Reinforcement and inhibition Reinforcement = facilitation that enhances spinal reflexes Spinal reflexes can also be inhibited Babinski reflex replaced by planter reflex The Babinski Reflexes