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Peripheral Nervous System General Organization Cranial Nerves Spinal Nerves Reflex Activity Autonomic Nervous System Somatic Sensory System Exit BASIM ZWAIN LECTURE NOTES Home General Organization Background Sensory Nerves Motor endings receptors Nature of stimulus detected a. Mechanoreceptors Generalized sensory receptors Types i. Touch,based vibration, pressure, stretch Location Classification on nature of information 1. b. Function a. Neuromuscular junction Thermoreceptors a. Exteroceptors a.b.Sensory (afferent) nerves Complexity Encapsulated a. Connect brain with outside world Classification based on site ofand origin i. Contact between motor neuron muscle i. Temperature changes i. Surface of skin i.i.a. Sensory information from periphery to CNS Parallel bundles of peripheral axons Simple Meisner’s corpuscles—low frequency vibration) Function i.a. CNS function is dependent on information Free dendritic endings (unencapsulated) a. Cranial nerves ii. Release ACh c. Photoreceptors Interoceptors b.ii.Motor (efferent) nerves a. Enclosed by connective tissue corpuscles—high frequency 2.Pacinian Structural components i.b. Most sensory receptors (generalized) a. Activate effectors i.i.Free Brain origin b.i.iii. Varicosities i. Light energy i. Visceroceptors corpuscles—deep pressure a.Ruffini’s Sensory receptors Motor information from CNS to periphery b. Some may be myelinated b. Complex ii. Merkel discs i. Release of neurotransmitter b. Spinal nerves i. Contact between autonomic motor iv. Muscle spindles—muscle stretch ii. Exclusively in the retina b. Peripheral nerves and ganglia ii. Visceral organs and blood vessels iii. Root hair plexus c. Mixed nerves i. Special senses (vision, audition, i.Proprioceptors Arise from spinal cord stretch v. Golgi tendon organs—tendon Endings and visceral effectors and organs, c. Efferent motor endings d. Chemoreceptors c. i. olfaction, Include sensory and motor gustation) Smooth and cardiac muscle Chemical in solution i.i. Musculoskeletal organs e. Nociceptors Home Exit i. Pain BASIM ZWAIN LECTURE NOTES Cranial Nerves I II III IV V VI VII VIII IX X XI Cranial Nerve Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Accessory Sensory Function YES—smell YES—vision NO NO YES—general sensation NO YES—taste YES—audition; balance YES—taste YES—taste NO XII Hypoglossal NO Exit Motor Function NO NO YES—eye muscles YES—eye muscle YES—chewing YES—abducts eye YES—facial expression NO YES—tongue and pharynx YES—pharynx and larynx YES—head and neck movement YES—tongue BASIM ZWAIN LECTURE NOTES Home Spinal Nerves Nomenclature Structure Nerves Dermatomes plexuses 1. Dorsal and ventral rootlets 3.Named Fibers of different rami for the level ofventral theroot vertebral 2. Dorsal and ventral 1. Specific to ventral rami 1.Area ofare skin innervated byexits the column from which the nerves cross and redistributed 3. Dorsal root ganglion 2. Types a. 31 spinal nerves cutaneous branch of a single a.Branches contain fibers originating 4. Spinal nerve a. Cervical i. 8 cervical (C1 – C8)nerves spinal nerve from different spinal 5. Dorsal ramus of spinal nerve b. Brachial ii.All 12 Thoracic (T1 – T8) 2. spinal nerves (except C1) b.Innervation arrives via multiple 6. 5Ventral ramus of spinal nerve c. Lumbar iii. Lumbar (L1 – L8) Have dermatomes routes 7. Rami communicantes iv. 5 d. Sacral (S1 regions – S8) Sacral Dermatomes overlap i.3. More than a single spinal nerve a. Autonomic fibers v. 1 Coccygeal (C0) serves each limb muscle 8. Sympathetic chain ganglion Exit BASIM ZWAIN LECTURE NOTES Home Reflex Activity Background Components Stretch and deep of a tendon reflex arc reflexes Muscle spindles 1. Receptor (site of stimulus action) Sequence of events 2. 1. Sensory neuron (transmits the afferent Stimulus-response sequence a. Stretching muscle activates muscle spindle a. Consist of CNS) intrafusal fibers impulse to the a. Unlearned Extrafusal muscle fiberssensory fiber to b. Impulse carried by primary b. Wrapped center by afferent sensory endings 3. Integration b.i.cord Unpremeditated a. Skeletal muscle spinal Type Ia fibers a. Monosynaptic reflex (single synapse) Innervated by alpha (a) motor c.ii.b. Involuntary c. Activates alpha motor neuron Type II fibers b. Polysynaptic (multiple synapses with neurons c.Mediated Gamma (g) by efferent fibers i. Sends efferent signal to muscle (effect) 2. spinal cord circuits chains of interneurons) i. Innervate contractile region of spindle d. Stretched muscle contracts a. Information may ultimately 4. Motor neuron (conducts efferent impulse ii. Maintain spindle sensitivity e. Antagonist muscle is reciprocally inhibited relayed to the brain from integration center to effector 5. Effector (muscle fiber or gland) Exit BASIM ZWAIN LECTURE NOTES Home Autonomic Nervous System 5. Neurotransmitter 9. 10. Sympathetic Parasympathetic response response Division Preganglionic Postganglionic a. ACh acts locally 8.6.Function 2.Cell bodies of alllength lower autonomic motor Fiber Somatic Nervous System i. ACh a. always has a stimulatory effect a. Pupil dilated Divisions work in concert a. Pupils constrict neurons lie outside the CNS a. Parasympathetic 4. Divisions differ based on: 1. Voluntary i.b.Increase e. Increased metabolic blood rate pressure NE has spreads far and can dision exert its effects 3. Divisions d. Constricts bronchioles b. Secretory responses inhibited b. Parasympathetic b. Stimulates secretory activity Sympathetic ACh NE a. Autonomic ganglia i. Long preganglionic 1.Autonomic Nervous System is involuntary a. Neurotransmitter type Voluntary muscle movement i.a.Glucose i.Increases Constricts is released most into vessels blood over distances when circulated in the blood e.long activity of digestive system a. Sympathetic c. Stimulates sweating i. b. Salivation i. Maintenance of function b. Neurons are postganglionic ii. Short postganglionic (autonomic functions are carried out Fiber length ii. Lipolysis f. Bronchioles dilate Adrenergic receptors 2.c.Sensory information to the CNS f. Causes erection (penis and clitoris) d.Heart Heart function b. Parasympathetic c. function ii.by Energy conservation c. Driven preganglionic neurons whose b. Sympathetic without conscious, voluntary control) j. Increased g. Decreased alertness activity ofganglia digestive system c. Location of i. Alpha—stimulatory i. Vasodilation 3. Organization of cell bodies i. Increases rate i.Sympathetic Decreases ACh ratedivision Parasympathetic ACh c. h.a. Causes h. Piloerection ejaculation (vaginal reverse peristalsis) ii. Beta—inhibitory (except in the heart when cell bodies are in the spinal cord or brainstem i. Short preganglionic Function ii.d. Dilates coronary vessels Lie within spinal cord or brainstem ii. Constricts coronary vessels i. Emergence it is excitatory) ii. Long postganglionic b. Targets are controlled monosynaptically ii. Intense muscular activity Exit BASIM ZWAIN LECTURE NOTES Home Somatic Sensory System Background Mechanical Organization Somatic Somatosensory Pain andSensory Its Senses Control of Somatic Cortex Pathways Sensory Information Types Types of of receptors somatic sensation receptors DCML Pathway Spinal segments c. Two different mechanosensitive 1. Experiment--three Mechanoreceptors--sensitive beakers of water: one to physical cold, one Somatotopy 4. Proprioceptors 1. Mechanoreceptors 2. Nociceptors Characteristics 1. In the DCML pathway information ascends 3. Thermoreceptors Information carried in each pathway remains 1. 30 spinal segments consisting of paired proprioceptors: Mechanism of function 3. hot, Brain one lukewarm. chemicals One finger from one hand into Classification Pathways 1. Mapping of the body's surface sensations onto a distortion Posterior parietal lobe 2. Several ST Pathway brain regions can suppress pain a. Body position Responds to many kinds of stimuli Differences between somatic senses and a.Pacinian (sensitive to vibration (250-350 Hz), Free,and unmyelinated nerve endings 3. Regulation Characteristics of pain Mechanical energy 1. Pain is influenced cognitively through the dorsal column on the ipsilateral Dermatomes separate a. Brain temperature is tightly regulated dorsal ventral roots hot; one finger from the other hand into cold. After i. Muscle spindles-consist of specialized brain structure 1. Stimuli applied to skin deform or change a. Endorphins 1. 1. Free Dorsal nerve column-medial endings c. Ruffini's ending-not well understood 2. Nociceptors--respond to damaging stimuli Primary somatosensory cortex receives Anatomy PAG 1. Information (periacqueductal crosses gray to the matter) contralateral project i. Where the body is Note: Like other sensory receptors, (usually mechanical) other senses involved in fine discrimination ofcortex texture orinto b. Signal that body tissue is being damaged a. 1. Overlap Pain can between be modified the dermatomes by non-painful 1. Easily differentiated 2. Hyperalgesia side of the spinal cord Two basic systems Segmental organization of spinal nerves & Nociception 1. Segregated all the way to the (close to 37C, brain function changes above some time period, immerse both simultaneously 2. Features of the map: a. Not continuous, b. Not 2. Spinal segments are divided into 4 groups: intrafusal muscle fibers distributed among receptor i. Share many opioid properties and bind to a. lemniscal Nociceptors pathway DCML d. Mercel's disks (light pressure and 3. Thermoreceptors--sensitive to changes in simple segregated streams of sensory 1. Parietal lobe side in the spinal cord to the raphe (serotonin) that sends axons to ii. Direction of movement temperature receptors adapt. They respond to 3. At least four senses (temperature, body Receptors are distributed throughout other moving stimuli that cause vibrations c. In most tissues, not brain b. sensory Cervical input dermatomes: (i.e., rub the above skin the around sternum a a.Stimulus frequency a. Tissue already damaged is much more 2. Synapses in the medulla 1. Pain and temperature the lukewarm. Thetemperature) finger from the hot senses the innervation of skin are related 1. Sensory process that signals that Thalamus and below that scaled to the human body, c.provides Relative size of the cervical, thoracic, lumbar, sacral ordinary (extrafusal) muscle fibers; detect a. Alters the ionic permeability of the receptor opioid receptors in the brain b. a. Thermoreceptors Touch and proprioception Tactile discrimination temperature information Post-central gyrus the 2. spinal Ascends cord via (5-HT the spinothalamic is inhibitory, block tract iii. Speed of movement sudden changes in temperature. position, touch & pain) body as opposed to being concentrated b. Meissner's corpuscle (most common d. Types of damage detected c.Thoracic bruise) dermatomes: top of sternum tosenses waist b. Stimulus pressure water to be cold and the finger from the cold sensitive to pain cortex devoted to each body part is correlated with 3. Crosses over and ascends via the medial 2. Touch and Proprioception 2. Area of skin innervated by the dorsal roots trigger pain a. Ventral posterior (VP) nucleus receives the b. Specialized receptors that can perceive 3. Each segment is named after vertebra from changes in muscle length creating generator potentials ii. Opioid receptors are throughout body, but 2. 2. Encapsulated Spinothalamic pathway ST e. Hair follicle receptor 4. Proprioceptors--monitor body position 2. Integration takes place in the posterior i. Most complex processing occurs in cortex synaptic 3. Synapses activity) in the thalamus (VP) b. Receptors in the skeletal muscles (more in 4. Place, pressure, sharpness, texture, and at small, specialized locations receptor in glabrous skin (smooth, hairless), same water to be hot. Why? Adaptation--the hot i. Mechanical-strong pressure (sharp objects) the density of sensory input (i.e., lips versus the d.Lumbar a. Gate Theory dermatomes: of Pain-circuit front of in legs spinal &stomach cord c. Receptive field Nociceptors are sensitized by various lemniscus to the thalamus (VP) of a single spinal segment is a dermatome information and projects to the changes in temperature as small as 0.01C. which nerves emerge (cervical: C1 C8, ii. Golgi tendon organs-distributed among i. Trigger action potentials especially in brain and particularly in brain a. a. Most Pain and cutaneous temperature receptors 5. Chemoreceptors--respond to certain parietal cortex 4. Projects to the cortex. movement lecture) and cold receptors adapted (stopped firing). When skin on your calf) & d. Size is related to importance duration can be accurately gauges sensitive to vibration ( low frequency , 30-50 Hz) ii. Thermal (different from temperature)-e.Sacral dorsal root dermatomes (back of legs & genitals) substances released by damaged tissue 4. Synapses in VP thalamus somatosensory cortex c. Two types (warm--begin firing at 30C-45C thoracic: T1 T12, lumbar: L1 L5 & sacral: S1 collagen fibers in tendons and detects areas that process and modulate nociceptive chemicals immersed in lukewarm, only the unadapted of the sensory input (i.e., fingerto tipbe versus elbow) Active when tissues begin destroyed (protaglandins, histamines, etc.) 5. Projects to the cortex (above causes damage and pain) &cord) cold--changes S5) in muscle tension information receptors were (PA, available. raphe, You and need spinal both to sense iii. Chemical--environmental agents or those below 35C to 10C) Home lukewarm, etc. Exit BASIM ZWAIN LECTURE NOTES from tissues itself--pH, histamine, etc.