Integration of the nervous system functions

Integration of the nervous system functions
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

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

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

w/in the CNS AP’s to the cerebral cortex & to other areas of the CNS
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 Thalamus & amygdala are involved in the sense of pain Many AP’s reaching the cerebral cortex are ignored others are translated and person becomes aware of the stimuli AP1 Chapter 14

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

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

Function: Mechanoreceptor: Chemoreceptors: Thermoreceptors:
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 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

Location Exteroreceptors: Visceroreceptors: Proprioceptors:
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

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

Structure Free Nerve ending Tactile/Merkel Disk Hair follicle receptor
Branches with no capsule Tactile/Merkel Disk Flattened 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 Temp for FNE: Cold (increases action potentials when skin is cooled (10-15X as many as warm) degrees C Warm: (Increase AP’s when skins is warmed (25-47 degrees C) PAIN!: extreme temp change 0-12oC or above 47oC AP1 Chapter 14

Structure Pacinian Corpuscle Meissner corpuscle Ruffini end organs
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 2 point discrimination: able to detect simultaneous 2 points on the skin ^ #’s include fingers & tongue \/ #’s on shoulders AP1 Chapter 14

Structure Muscle Spindle Golgi End Organ
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 7 important for control of muscle tone brain centers act to increase ot decrease Ap’s in g motor neurons via descending tracts (react w/ reflex when stretched to increase tension in stretched muscle.) AP1 Chapter 14

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

Responses of sensory receptors
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 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. AP1 Chapter 14

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 conscious perception of external stimuli: Anteriolateral system Dorsal-column/medial lemniscal system Ascending tracts involved with unconsciouss perception: Spinocerebellar, spinoolivary, spinomesencephalic, & spinoreticular tracts Spinocerebellar (Ori SC) (Terminatecerebellum) NEXT 6 Slides are Sensory Tract examples AP1 Chapter 14

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 Primary Cell body (found in dorsal root ganglion), Secondary Cell body (Found in posterior gray horn), Tertiary Cell Body (a. Thalamus b. Reticular formation c. Superior colliculus) AP1 Chapter 14

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 M Modality O Origin T Termination 1o cell body Dorsal root Ganglion 20Cell body Medulla Oblongata Crossover (if any)  MO 30 Cell body Thalamus Lemniscus (means ribbon & refers to the thin ribbon-like appearance of the pathway as it passes thru the brainstem AP1 Chapter 14

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 mvmt asso. 1oly w/mvmt & balance Spinotectal tracts: superior colliculi of the midbrain AP’s involved in reflexes that turn head & eyes toward point of cutaneous stimulation TGTL Tract: 10 from 1side cross synapse w 2o to opposite side of brainstem 2o-Synapes w/3o in thalamus which project to somatic sensory cortex AP1 Chapter 14

I. Sensation Sensory 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 Posterior: contains uncrossed nerve fibers that enter the cerebellum thru the inferior cerebellar penduncles Anterior: both crossed & uncrossed & enter cerebellum thru superior cerebellar penduncles (those that crossover recross to end in the same cerebellum hemisphere as original side of the body (Why?? Unknown) AP1 Chapter 14

I. Sensation Sensory 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

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 pg 481 AP1 Chapter 14

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

C. Sensory areas of the cerebral cortex
Taste Area Taste sensations are perceived located at the end of the inferior end of the postcentral gyrus 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

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 D. Sensory Processing Example: Visual cortex Sensory AP’s from retina reach visual cortex and image is perceived; AP’s are then sent to the VAA it takes the present info and compares it to past visual experiences  w/this in mind the area decides if input is recognized or ignored (it passes judgment on the info’s importance) [we pay more attention to people we know in a crowd] [INTERCONNECTIONS [emotionally we recognize people we love with more enthusiasm] AP1 Chapter 14

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

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 (*) most will occur automatically after you learn the mvmt (walking) AP1 Chapter 14

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

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 *Precentral gyrus/Primary Motor Area Just like the PSSA size of the area is indicative of # of motor units. Higher the # of MU in an area the larger the region in the PMC is. (Fine motor control would occur in the hands (look at the areas representation) While large muscles do not necessarily have high #’s b/c they don’t need to be precise) AP1 Chapter 14

B. Motor Tracts Descending 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 Names  Prefix origin Suffix termination (Ex/ corticospinal (Cerebral cortex  origin / SC termination)) Corticobulbar Tract Corticospinal Tract Vestibulospinal Reticulospinal Anterior Corticospinal Tract Lateral Corticospinal Tract AP1 Chapter 14

Direct Pathway Maintenance of muscle tone & controlling the speed & precision of skilled mvmts, 1oly fine mvmts involved in dexterity* Corticobulbular Tracts Corticospinal Tracts Mvmts below the head esp the hands Control eye & tongue mvmts, mastication, facial expression & palatine, pharyngeal, & laryngeal mvmts Lateral Corticospinal Tracts Anterior Corticospinal Tracts Direct pathway anmed b/c UMN’s in cerebral cortex synapse directly z/LMN in brainstem & SC * Main fxn add speed & agility to conscious mvmts, esp the hands & provide a high degree of motor control such as individual fingers Mvmt of neck, trunk & limbs (push-ups, moving with a hola hoop.) Mvmt of the neck & upper limb extremities (Typing) AP1 Chapter 14

*Indirect Pathway Less precise (unconscious) control of motor fxns especially those involved in overall body coordination & cerebellar fxn 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 *Originate in neurons of the cerebrum & cerebellum whose axons synapse w/some intermediate nucleus rather than directly with the LMN Maintenance of upright posture /balance Extension of upper limbs when falling down AP1 Chapter 14

Direct vs. Indirect AP1 Chapter 14

C. Modifying & refining motor activities
Cerebellum Vestibulcerebellum: Controls balance & eye mvmt Spinocerebellum: Corrects discepancies btwn intended & actual mvmts (Comparator) Cerebrocerebellum: Can “learn” highly specific complex motor activites (piano/baseball) Also involved in cognitive fxns 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 Stimulatory: facilitate muscle activity esp the beginning of voluntary mvmt (rising from sitting or beginning to walk) Inhibitory: facilitate the actions of the stimulatory by inhibiting muscle activity in antagonist muscles (decrease muscle tone when body/limbs & head rest (Eliminating unwanted mvmts) Basal Ganglion (difficulty rising from sitting, initiating walking; increased in muscle tone & exaggerated/uncontrolled mvmts rest CP/Parkinsons Cerebrocerebellum: such as rhythm, conceptualization of time intervals, word associations, solutions to pegboard puzzles, (Tasks once thought to occur only in the cerebrum) AP1 Chapter 14

Cerebellar Comparator FXN
AP1 Chapter 14

III. Brain stem fxns Major 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

III. Brainstem (Bnsm) fxns
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 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 AP1 Chapter 14

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

C. Motor Output & reflexes projecting thru the Bnsm
Somatic Motor Output & Reflexes Parasympathetic Output & Reflexes 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. 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 Ultimately what we are talking about are signals (Somatic or Parasympathetic) that begin in the upper brain to get something to move and these signals pass through the BS nuclei (OR) we are talking about reflexes that are controlled by parts of the BS. AP1 Chapter 14

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

A. Speech- 2 major areas 1. Wernicke’s Area 2. Broca’s Area
Portion of the parietal lobe Sensory speech area Req’d for understanding & formulating coherent speech Inferior part of the frontal lobe Motor speech area Initiates the complex series of mvmts necessary for speech Normally found in the left cerebral cortex So step by step ((Read aloud))  AP’s from the eye carried to the 1o visual cortex  WORD IS SEEN Word is recognized via the visual association area **& understood in parts of wernicke’s area** AP’s representing the word are conducted thru association fibers from WA to BA  in Broca’s area word is formulated as it will be spoken AP’s to the premotor area (movements programmed)  AP’s to 1o motor cortex tigger proper movement ** hearing: repeat a spoken word- hear it and auditory AP’s are carried to the 1o auditory cortex (word is heard)  auditory association area recognizes the word ** Connected to each other by a bundle of neurons known as arcuate fasciculus AP1 Chapter 14

B. Right & Left Cerebral cortex
Commissure: band of tracts that connect the 2 hemisphere for info sharing 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 Hemispheric lateralization: Left: reasoning, numerical & scientific skills, ability to use & understand sign language, spoken & written language Right: Musical & artistic awareness, Space & pattern perception, Recognition of faces & emotional content of facial expressions, Generating emotional content of language, Generating mental images, Identifying & discriminating among odors B. Right & Left Cerebral cortex AP1 Chapter 14

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 C. Brainwaves & sleep 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

D. Memory: 3 types Sensory memory: Short term memory Long term 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 The amount of bits can vary from person to person & if those bits are grouped it may be easier to store it Give someone a phone number and then give them another the 1st will be lost Long term (next slide) AP1 Chapter 14

D. Memory: Long term Declarative Procedural 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) 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) Facts like names, dates, or places H: Person’s name (Damage! Can’t move things to long term memory) A: Like or dislike the person good or bad experiences with them? Compartmentalized: Different regions for people’s name, vs. people’s faces, verses places, vs things recognized by shape (animals) vs things recognized by feel Retrieval of a complex memory involves accessing parts of a memory from different compartments (this may also explain why some memories change over time) # “ It’s like riding a bike you never forget” AP1 Chapter 14

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 Presynaptic neuron increase glutamate prod’n & release, the # of glutamate receptors in postsynaptic cell increase which helps to carry the signal longer in the postsynatic cell. The glutamate receptors allow the influx of calcium which associates & activates calmodulin in the neuron calmodulin acts thru a cAMP mechanism that stimulates specific proteins to prod These D the cell’s shape (grow new axons). AP1 Chapter 14

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

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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