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Chapter 14

Chapter 14. Integration of the nervous system functions

farrah-gallegos
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Chapter 14

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  1. Chapter 14 Integration of the nervous system functions Compared to animals we have large complex brains that have the same basic function of receiving and sending signals, but we are also capable to unique complex functions: recording history, reasoning, planning, to a degree unparalleled in the animal kingdom. AP1 Chapter 14

  2. Chapter 14 Outline • Sensation • Control of skeletal muscle • Brain Stem Function • Other Brain functions • FX of aging of the nervous system AP1 Chapter 14

  3. I. Sensation • Sensory receptors • Sensory tracts • Sensory areas of the cerebral cortex • Sensory processing AP1 Chapter 14

  4. I. Sensation • Sensation/perception • Conscious awareness of FX of stimuli on sensory receptors • Sensation requires 3 steps: Stimuli originating inside or outside of the body are detected by sensory receptors & AP’s are propagated to the CNS via the nerves w/in the CNS AP’s to the cerebral cortex & to other areas of the CNS Many AP’s reaching the cerebral cortex are ignored others are translated and person becomes aware of the stimuli AP1 Chapter 14

  5. Senses: means by which the brain perceives information about the environment & the body 5 recognized senses: Smell Taste Sight Hearing Touch • More specialized structure • Specialized nerve endings • Localized to specific organs Divided into 2 groups 1 2 Provide sensory info for internal organs Provide sensory info about the body & environment AP1 Chapter 14

  6. Sensory receptors can be categorized in various ways • Function: • Mechanoreceptors, Chemoreceptors, Thermoreceptors, Photoreceptors, & Nociceptors • Location: • Exteroreceptors, Visceroreceptors, & Proprioceptors • Structure: • Free nerve endings, Tacile/Merkle disks, Hair follicle receptors, Pacinian Corpuscles, Meissner corpusle, Ruffini end organs, Muscle spindles, & Golgi tendon apparatus AP1 Chapter 14

  7. Function: • Mechanoreceptor: • Mechanical stimuli (Compression, bending, or stretching) • Fxn: touch, tickle, itch, vibration, pressure, proprioception, hearing & balance • Chemoreceptors: • Ligands bind to cell membrane receptors • Fxn: Smell & taste • Thermoreceptors: • Responds to D’s in temp @ site of receptor • Fxn: req’d for sense of temp • Photoreceptors: • Responds to light striking receptor cells • Fxn: req’d for vision • Nociceptors: • (pain) responds to mechanical, chemical, or thermal stimuli, some can respond to more than 1. AP1 Chapter 14

  8. Location • Exteroreceptors: • Associated with the skin and detects the external environment • Visceroreceptors: • Associated with the visceral organs & detects the internal environment • Proprioceptors: • Associated with joints, tendons, & other CT & detects body position, mvmt, & extent of stretch or force of muscular contraction AP1 Chapter 14

  9. Structure • Free nerve endings • Tactile/Merkle Disk • Hair follicle receptors • Pacinian Corpuscle • Meissner corpusle • Ruffini end organs • Muscle spindles • Golgi Tendon Organ AP1 Chapter 14

  10. Structure • Free Nerve ending • Branches with no capsule • Tactile/Merkel Disk • Flattened expansions @ axon ends associated with Merkel cells • Hair follicle receptor • Wrapped around hair follicle or extending along axis each axons supplies X hairs and each hair has axons from X neurons AP1 Chapter 14

  11. Structure • Pacinian Corpuscle • Onion shaped multilayered capsule with 1 central nerve process found deep in the dermis/ hypodermis/ associated with joints • Meissner corpuscle • Several branches of 1 axon asso.’d w/ wedge shaped eptheliod cells & surrounded by a CT capsule • Ruffini end organs • Branching axon w/numerous terminal knobs surrounded by CT capsule AP1 Chapter 14

  12. Structure • Muscle Spindle • Sk muscle fibers enclosed by LCT capsule w/sensory nerve endings in the center • Proprioception asso w/detection of muscle stretch • Golgi End Organ • Surrounds tendon & enclosed in delicate CT capsule • Proprioception asso w/ stretch of tendon & imp in control of muscle contraction AP1 Chapter 14

  13. Responses of Sensory receptors:Primary vs. Secondary Receptors Primary Directly conduct an AP Secondary Sensory receptor releases NT, doesn’t carry AP AP1 Chapter 14

  14. Responses of sensory receptors • Accomidation/Adaptation: • A decreased sensitivity to a continued stimulus • The response of the receptors or sensory pathways to a certain stimulus strength lessens from that which occurs when the stimulus was 1st applied. • Tonic Receptors: • slowly adapting receptors generate AP’s as long as the stimulus is applied and accommodate very slowly • Phasic receptors: • Rapidly adapting receptors accommodate rapidly & are most sensative to changes in stimuli AP1 Chapter 14

  15. I. Sensation: Sensory Tracts • SC & brainstem have a # of sensory pathways that transmit AP’s from the periphery to various parts of the brain. • Each is involved with specific modalities (type of info transmitted) • Names indicate their origin & termination • 2 Major ascending tracts involved in consciousperception of external stimuli: • Anteriolateral system • Dorsal-column/medial lemniscal system • Ascending tracts involved with unconsciouss perception: • Spinocerebellar, spinoolivary, spinomesencephalic, & spinoreticular tracts AP1 Chapter 14

  16. I. Sensation: Sensory Tracts • Anterolateral Pathway • All originate from cutaneous receptors • Crossing over may occur near the level of neuron entry • Spinothalamic • Modaility (M) pain, temp, light touch, pressure, tickle, & itch • Termination (T) Cerebral cortex • Spinoreticular • (M) Pain • (T) Reticular formation & thalamus • Spinomesencephalic • (M) Pain & touch • (T) mesencephalon & superior colliculus AP1 Chapter 14

  17. I. Sensation: Sensory Tracts • Dorsal-column/Medial-lemniscal System • Fasciculus gracilis • Conveys impulses from nerve endings below the midthorax • Fasciculus cuneatus • Conveys impulses from below midthorax • (M) proprioception, 2-point discrimination, pressure, & vibration • (O) Joints, tendons, muscles • (T) Cerebral cortex & cerebellum • Contralateral • Involved in conscious awareness of proprioception but also unconscious neuromuscular fxns AP1 Chapter 14

  18. I. Sensation:Sensory Tracts • Trigeminothalamic Tract • Joins with spinothalamic tract as they both pass thru brainstem • Afferent fibers from • Trigeminal nerve (1o) • ear, tongue, cranial nerves 7, 9, &10 • Info from face, nasal cavity, & oral cavity • Pain, temp, light touch, pressure, tickle, itch, touch, proprioception, 2-p discrimination, & vibration • Spinoolivary tracts: • Project to: • Olivary nucleus • Cerebellum • AP’s contribute to coordintion of mvmtasso. 1oly w/mvmt & balance • Spinotectal tracts: • End @ superior colliculi of the midbrain • AP’s involved in reflexes that turn head & eyes toward point of cutaneous stimulation AP1 Chapter 14

  19. I. SensationSensory Tracts • Spinocerebellar (SpCB) System • Carry proprioceptive info to cerebellum so info concerning actual mvmt can be monitored & compared w/cerebral info rep’ing intended mvmts • Two tracts • Posterior SpCB tract • Info from thorax, upper limbs, & upper lumbar region  cerebellum • Anterior SpCB tract • Info from lower truck & lower limbs AP1 Chapter 14

  20. I. SensationSensory Tracts Descending Pathways that modify sensation • Corticospinal plus other descending tracts send collateral branches to the thalamus, reticular formation, trigeminal nuclei & spinal cord • Neuromodulators from these regions decrease the frquency of AP’s to sensory tracts via the cerebral cortex & other brain regions • This may reduce the conscious perception of sensations AP1 Chapter 14

  21. C. Sensory Areas of the Cerebral Cortex • Sensory pathways project to specific regions of the cerebral cortex where sensations are perceived • Must be intact for conscious perception, localization, & identification of a stimulus • Projection: although cutaneous sensations are integrated within the cerebrum, they are perceived as though on the surface of the body Figure 14.11 pg 481 AP1 Chapter 14

  22. C. Sensory areas of the cerebral cortex • 1o Somatic Sensory Cortex(PSSC) • This pattern can be found in both hemispheres • NOTICE the size of the areas corresponding to the sensory regions • The size of the region is related to the # of sensory receptors in that area of the body • THUS: the density of sensory receptors in the face is > than that seen in the legs (just look at how much area is dedicated to it.) • THUS the greater the area of the SSC the more sensory receptors in that area of the body AP1 Chapter 14

  23. C. Sensory areas of the cerebral cortex • Taste Area • Taste sensations are perceived • located at the end of the inferior end of the postcentralgyrus • Olfactory cortex: • Here conscious & unconscious responses to odor are initiated • (not shown) inferior surface frontal lobe • Primary Auditory cortex • Here auditory stimuli are processed by this part of the brain • Superior Temporal Lobe • Visual Cortex • Portions of visual images are processed by this part of the brain (Color, shape & mvmt are processed separately rather than a complete color motion picture) • Located in the occipital lobe AP1 Chapter 14

  24. D. Sensory Processing • Association Areas are involved in the process of recognition (Process sensory input from the primary sensory areas) • They are normally adjacent to their 1o sensory area. • There are 3 • Auditory Association Area • Somatic Sensory Association Area • Visual Association Area Also interconnected w/other parts of the brain AP1 Chapter 14

  25. II. Control of Skeletal Muscles • Motor areas of the cerebral cortex • Motor Tracts • Modifying and refining motor activities AP1 Chapter 14

  26. II. Control of Skeletal Muscle • Reflexes (occur w/o conscious thought) • Voluntary Mvmts: • Mvmts consciously activated to achieve a specific goal (*) • AP’s mv from upper motor neurons (UMN) to lower motor neurons (LMN) • UMN: cell bodies w/in cerebral cortex and connect directly or indirectly (internerons) to LMN • LMN: cell bodies synapse with UMN in the 1.anterior horns of the gray matter (SC) or 2. cranial nerve nuclei of brainstem then axons leave CNS & extend thru the PNS nerves to supply ske. muscle • Motor Syst of brain & SC responsible for maintaining: • Body’s posture & balance • Moving: trunk, head, limbs, & eyes • Communicating thru facial expressions & speech AP1 Chapter 14

  27. II. Control of Skeletal Muscles Initiation of of most voluntary mvmts begin in the premotor area of cerebral cortex & involve the stimulation of the UMN’s Voluntary Movements Depend on UMN form descending tracts i Stimulate LMN i Stimulate skeletal muscle contraction Cerebral cortex interacts with Basal nuclei & cerebellum  to plan, coordinate, & execute mvmts AP1 Chapter 14

  28. A. Motor Areas- Cerebral Cortex • *Primary Motor Cortex(PMC) • Although only 30% of the UMN are located in the PMC, AP’s from PMC control many voluntary mvmts • The higher the # of MU (that have few muscle fibers) the more precise the movement • Premotor Area: • Staging area where motor fxns are organized b4 they are initiated in the (PMC) • Which muscles must contract, in what order to contract, & to what degree do they contract • Prefrontal Area: • Involved in motivation & foresight to plan and initiate mvts • Involved in motivation & regulation of emotional behavior & mood AP1 Chapter 14

  29. B. Motor TractsDescending pathways w/axons carrying AP’s from regions of the cerebrum/cerebellum to brainstem & SC 2 divisions Direct Pathways/Pyramidal System Indirect Pathways/Extrapyramidal System Rubrospinal Tectospinal Corticobulbar Tract Corticospinal Tract Vestibulospinal Reticulospinal Anterior Corticospinal Tract Lateral Corticospinal Tract AP1 Chapter 14

  30. Direct Pathway Maintenance of muscle tone & controlling the speed & precision of skilled mvmts, 1oly fine mvmts involved in dexterity* Corticospinal Tracts Corticobulbular Tracts Mvmts below the head esp the hands Control eye & tongue mvmts, mastication, facial expression & palatine, pharyngeal, & laryngeal mvmts Anterior Corticospinal Tracts Lateral Corticospinal Tracts Mvmt of neck, trunk & limbs (push-ups, moving with a hola hoop.) Mvmt of the neck & upper limb extremities (Typing) AP1 Chapter 14

  31. *Indirect Pathway Less precise (unconscious) control of motor fxns especially those involved in overall body coordination & cerebellarfxn such as posture Rubrospinal Tracts Tectospinal Tracts • Mvmt coordination • Positioning digits & palm when reaching out to grasp • Reg’ing fine motor control of muscles in the distal part of the upper limbs Reticulospinal Tracts • Mvmt of head and neck in response to visual & auditory reflexes • Mvmt of head & neck away from a sudden flash of light • Posture Adjustment/ Walking • Maintenance of posture while standing on 1 foot Vestibulospinal Tracts • Maintenance of upright posture /balance • Extension of upper limbs when falling down AP1 Chapter 14

  32. Direct vs. Indirect AP1 Chapter 14

  33. C. Modifying & refining motor activities • Basal Nuclei • Important in planning, organizing, & coordinating motor mvmts & posture. • Links to both the thalamus & cerebral cortex • These form feedback loops • Can be stimulatory/inhibitory • Disorder • Cerebellum • Vestibulcerebellum: • Controls balance & eye mvmt • Spinocerebellum: • Corrects discepanciesbtwn intended & actual mvmts (Comparator) • Cerebrocerebellum: • Can “learn” highly specific complex motor activites (piano/baseball) • Also involved in cognitive fxns AP1 Chapter 14

  34. Cerebellar Comparator FXN AP1 Chapter 14

  35. III. Brain stem fxnsMajor ascending & descending pathways project thru the brainstem • Sensory input projecting through the brainstem • RAS functions of the brainstem • Vital fxns controlled in the brainstem AP1 Chapter 14

  36. III. Brainstem (Bnsm) fxns • Sensory Input Projecting Thru the BnSm • Sensory axons project thru the BnSm from the ascending SC pathways • Sensory nuclei from cranial nerves (CN) 3-10 & 11 • Nuclei of the reticular formation • Cranial Nerve (CN) 2 Vision • CN 5 tactile sensation from face, nasal & oral cavities • CN 7 Taste • CN 8 Hearing and balance • CN 9  Taste and tactile sensation in the throat • CN 10 Taste and tactile sensation in the larynx; visceral sensation in the throat and abdomen AP1 Chapter 14

  37. B. RAS Fxns of the Bnsm • Reticular activating system (RAS) • Can be stimulated by inputs from the cerebral cortex (mental activities), & a variety of sensory inputs from stimuli such as visual (flashes of light), auditory (ringing alarm), olfactory (burning/coffee), & sematosensory (splashing cold H2O on/touching your face). • CN’s 2,5,&8 stimulate wakefulness & consciousness • RAS is involved in sleep wake • Maintain alertness & attention AP1 Chapter 14

  38. C. Motor Output & reflexes projecting thru the Bnsm Somatic Motor Output & Reflexes Parasympathetic Output & Reflexes Reflexes controlled via the reticular formation: Visual reflexes (pupil size) Passin’ thru Sneeze reflex Salivary glands stimulation to salivate Gag reflex Cough reflex Heart rate Respiration Digestion • Reflexes: • Eyes/neck mvmt in response to visual & auditory stimuli or tactile stimulation • Passin’ thru • Eyes: move & look toward on object, tracking a moving object • Chewing, how hard or soft something is and changing mvmt accordingly control of tongue for chewing & speech • Facial muscles for expressions • Pharynx & larynx associated with swallowing & speech. AP1 Chapter 14

  39. IV. Other brain functions • Brain is capable of many fxns besides sensory input & muscle control. Speech, mathematical & artistic abilities, sleep memory, emotions, & judgement • Speech • Right & Left cerebral cortex • Brainwaves and sleep • Memory • Limbic System AP1 Chapter 14

  40. A. Speech- 2 major areas 1. Wernicke’s Area 2. Broca’s Area Inferior part of the frontal lobe Motor speech area Initiates the complex series of mvmts necessary for speech • Portion of the parietal lobe • Sensory speech area • Req’d for understanding & formulating coherent speech Connected to each other by a bundle of neurons known as arcuate fasciculus AP1 Chapter 14

  41. Commissure: band of tracts that connect the 2 hemisphere for info sharing B. Right & Left Cerebral cortex Rt. Cerebral Hemisphere Lt. Cerebral Hemisphere • Motor Output goes to the left side • Sensory input comes from the left side • Spatial perception, facial recognition, & musical ability • Motor Output goes to the right side • Sensory input comes from the right side • mathematics & speech AP1 Chapter 14

  42. C. Brainwaves & sleep • Electroencephalogram: (EEG) • Can record simultaneous Ap’s in large #’s of neurons & displays wave-like patterns known as brain waves. • Most normal people don’t have a regular pattern but there are 4 regular patterns seen at specific times: • Alpha • Beta • Theta • Delta • These waves can be used as a diagnostic tool to diagnose brain disorders • Patterns also vary during the 4 stages of sleep. AP1 Chapter 14

  43. D. Memory: 3 types • Sensory memory: • Lasts less than a sec & involves transient D’s in membrane potential • Retention of sensory input received by the brain while something is scanned, evaluated, & acted on • Short term memory • Lasts sec’s to min’s if considered important enough to move from 1 to 2. • Limited by the # of bits of info that can be stored at 1 time • New info may cause loss of old • Physiology: short term D’s in membrane potential (longer than 1) but can be eliminated by new info entering the cell • Long term memory • Lasts hours to years to a lifetime • There are 2 types: • Declarative/ Explicit • Procedural/ Implicit/ Reflexive AP1 Chapter 14

  44. D. Memory: Long term Declarative Procedural Involves the development of skills like riding a bike or playing the piano. Primarily stored in cerebellum & premotor area of the cerebrum (only small amounts are lost thru time)# Conditioned/Pavlovian reflexes are implicit (but cerebellar lesions cause their loss) • Retention of facts • Accessed via the hippocampus, amygdala, or amygdaloid nuclear complex • H: involved in retrieving the actual memory* • A: involved in the emotional overtones of that memory * • Emotions may also serve as a switch for storing or not storing a memory • Memories appear to be compartmentalized* in the cerebrum • This also makes retrieval complex (put a puzzle together) AP1 Chapter 14

  45. D. Memory: Long term • Physiology of long term memory: • D’s in the neuron (long term potentiation) which facilities future transmission of AP’s. • The neuron grows new axons to increase the number of synapse. (especially seen in development of skills) • Repetition of info association with new info with existing memories assist in the transfer from short to long term memory AP1 Chapter 14

  46. D. Limbic System • Influences emotions, innate responses to emotions, motivation, mood & sensations of pain & pleasure • Associated with basic survival (reproduction, food H2O) • Damage: • Voracious appetite • Increased sexual activity (often inappropriate) • Docility (loss of fear and anger) • Temporal lobe damage (Loc of Limbic System) • Can also result in loss of memory formation AP1 Chapter 14

  47. V. FX of Aging on the NS • General decline in sensory & motor fxns • Short term memory is decreased • Thinking ability doesn’t D AP1 Chapter 14

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