Psych 3513 — Ch. 8: Action PDF

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Psych 3513 — Ch. 8: Action — 10.28.2020 Note: §/£ = SE: Semantic Encoding (Written attempts to help remember details more easily; e.g. mnemonics, memory palaces (method of loci); pay attention to BUI and capital letters. What is an Effector?: Any body part that is able to be moved ● Electromyogram (EMG) projects differential activity in biceps vs. triceps when extending vs. flexing (FIG 8.3) ● Primary role of Alpha motor neurons — make muscles move by causing contraction ○ They synapse on the muscle (Motor End Plate) ◆ Motor Unit: All of the muscle fibers synapsed by a single (unit) motor neuron ◆ Motor Pool: All of the alpha motor neurons which innervate a muscle. ○ Exit through ventral root (SAME-DAVE) ● The role of muscle spindles & Stretch Reflex ○ Muscle spindles- sensory receptors in muscle that inform about stretch (change in length and velocity of change in length) (Neuro 3050 Details enclosed below) ◆ Muscle Spindles: General purpose; Components — Proprioceptors/ stretch receptors registering changes in muscle length, position, velocity and acceleration (§ L, P, V, A (think of AP Physics C, derivatives, idk) ◆ Comprised of the following: 1. INTRAFUSAL STRIATED MUSCLE FIBERS (Provide regulation of muscle spindle stiffness; Located at either end of central area containing nuclei) ◆ 2. SENSORY AXONS ◆ Afferent cell bodies located in the DRG. These are axons of neurons who carry stretch information from the spindle to the spinal cord, through the DRG. ◆ >> Primary sensory axons, Type I-a axons: THICK, HEAVILY MYELINATED ◆ ---Terminate as a spiral around central nuclear region. ◆ ---RESPOND TO STRETCHING (Spindle Stretchingl; GTO Gato (deer thing; in Spanish sound of music) ◆ OF A MUSCLE + DETECT LENGTH + DETECT RATE OF CHANGE OF LENGTH ◆ >> Secondary endings, Type II: (less) THICK, MYELINATED ◆ --- Terminate near junction of intrafusal muscle fibers and nuclear area.

◆ ---RESPOND TO STRETCH + DETECT LENGTH ◆ >>Gamma Motor Axons ◆ ---Synapse on intrafusal fibers to regulate their tension (stiffness)

(RIT) ◆ --- NOT from alpha motor neuron; these are distinct and specific to ◆

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intrafusal fibers Objectove: Describe the primary afferents of muscle spindles. — Afferent cell bodies located in the DRG. These are axons of neurons who carry stretch information from the spindle to the spinal cord, through the DRG. Activated by stretching of muscle spindle which opens ion channels on terminals resulting in influx of ions and depolarization. (§ Actovated from SMS, opichart -> RI-I-De) ◆ Primary sensory axons, Type I-a axons: THICK, HEAVILY MYELINATED ◆ Terminate as a spiral around central nuclear region. ◆ RESPOND TO STRETCHING OF A MUSCLE + DETECT LENGTH + DETECT RATE OF CHANGE OF LENGTH ◆ (§ Dereliction of Duty; Extension from 1a -> 1st debates) ◆ Secondary endings, Type II: (less) THICK, MYELINATED ◆ Terminate near junction of intrafusal muscle fibers and nuclear area. ◆ RESPOND TO STRETCH + DETECT LENGTH (II ReSiDuLe) Extrafusal Fibers: the "regular,” frequent contractile fibers of the muscle — innervated by alpha motor neurons. ◆ Alpha motor neurons and lower motor neurons innervate extrafusal muscle fibers (§Almanac-Tra (recall from solo contests meetings; alumni). Intrafusal Fibers: the "inner" contractile fibers of the muscle. Compose muscle spindles (spINdles). ◆ Gamma motor neurons innervate intrafusal muscle (Regulate interʼs Tension (RIT) (Stiffness)) Primary afferents (Ia and II) of muscle spindles activated When a muscle is STRETCHED (¶Spindle SPreaD out), not in contraction. ◆ During contraction of the muscle, the spindle relaxes which decreases afferent input and thus motor output to extrafusal fibersm(§DMC,SpRindle — Daimopeff). 1. Static Nuclear Chain Fibers ◆ Linear chain (along the center) of fibers relaying info about STATIC muscle length. (§NSLC: National Student Leadership Conference) ◆ Innervated by static gamma-motor neuron fibers

◆ 2. Static Nuclear Bag Fibers ◆ Fibers with a bundle of nuclei at the center; Relay info about

STATIC muscle length. ◆ Innervated by static gamma-motor neuron fibers ◆ 3.Dynamic Nuclear Bag Fibers ◆ Fibers with a bundle of nuclei at the center; Relay info about the VELOCITY OF LENGTH CHANGE. ◆ Innervated by dynamic gamma motor neuronsm(§DIGIMON: DYNAMiC NuBagFib; VEL-Length-o-C(hange)-ity) (only fiber to receive innervstion from this specific neuron) ○ Annulospiral ending: Sensory ending of afferents in a muscle spindle (Type II and Ia) (§Afferent Nullment of SPI”n”dLe) ◆ Define the types of axons that innervate the muscle spindle (i.e., size, myelination, afferent, efferent). ◆ Type Ia: Larger diameter, heavily myelinated, afferent ◆ Type II: Medium diameter, myelinated, afferent (MDMA) ◆ Gamma Motor Axons: axons which innervate and bear effect upon intrafusal motor fiber ◆ Describe the pathway involved in generating a monosynaptic stretch reflex. --WHAT IS IT?-◆ A simple reflex that involves transmission of information from a sensory neuron to the appropriate motor neuron across a single synapse in the spinal cord. The knee-jerk reflex action is an example of a monosynaptic reflex ◆ --WHAT PATHWAY DOES IT USE?— (check this) ◆ Define the role of gamma motor neurons vs. alpha motor neurons in regulating muscle contraction. What is alpha-gamma co-activation? Alpha motor neurons: Contraction of extrafusal fibers ◆ Gamma motor neurons: Contraction of intrafusal fibers; ◆ During a muscle contraction, commands are simultaneously sent through alpha and gamma motor neurons (at the same rate) to maintain tension on the spindle and ensure that the muscle spindle afferents continue to be stretched and therefore relaying activation to the alpha-motor neurons, which maintain contraction of extrafusal muscle. ◆ Dynamic gamma motor neuron activation raises 1a fiber dynamic (d-oNe-A) sensitivity, but does not affect II fiber activity ◆ Static gamma motor activation raises II fiber (sTaTic) and Ia (sTAtic) fiber tonic sensitivity, and lowers Is fiber dynamic sensitivity. ◆ Role of interneurons in a spinal reflex circuit ◆ Muscle is stretched quickly ◆ I-a afferent synapse excites that muscle's alpha motorneurons

◆ I-a afferent synapses on the I-a inhibitory interneuron, which

suppresses antagonist motor neuron activation ◆ Summary: Alpha motor neuron is excited and antagonist muscle

contraction is suppressed ● Spinal interneurons found in spinal cord: Many descending neurons from

pyramidal/extrapyramidal synapse here. Interneurons then connect w/ other interneurons or alpha motor neurons Corticospinal tract (CST): Pyramidal vs. Extrapyramidal tracts ● Pyramidal tracts (lateral corticospinal tract (85%) and anterior CST (15%)) serve more direct roles in handling and guiding voluntary movements (of the distal and proximal muscles, respectively), whereas extrapyramidal tracts (e.g. reticulospinal tract, rubrospinal tract) serve more indirect roles in modulating and coordinating such movements. Regions of cerebellum, and functional dimensions. ● Vestobulocerebellum — oldest part of cerebellum which controls eye movement and balance (recall role of vestibulo-ocular reflex in allowing head rotation in tandem with eye movement to keep vision fixed upon an object) ● Spinocerebellum: receives sensory info from visual and auditory systems, affected by alcohol ● Neocerebellum: heavily innervated by descending neurons of parietal and frontal lobe; newest part What is the specialized role of the Supplementary Motor Area? (SMA) ● Involved in processing sequential and well-learned movements Ataxia vs. apraxia ● Ataxia - intention tremor, lesions in cerebellum (early lecture mentioned cerebellar ataxia) ● apraxia- lesions in cerebral cortex. hard time initiating movements ○ Ideomotor apraxia — patient has hard time initiating a movement, but has general idea of what the movement is for ○ Ideational apraxia — can execufe motions but does not know the purpose of the motion ● Intention tremor vs. resting tremor — intention tremor is seen in ataxia: shakes when trying to achieve task (Achieve -TAx/AXIon) ● Know the implications & description of the "Center-Out" task individual M1 neurons code for specific directions ● Role of Basal Ganglia as gatekeeper as specific motor plan gains strength, lessens the inhibition of this motor signal and it goes through ● Role of Substantia nigra: part of the basal ganglia ◆ 2 pars - pars compacta- releases dopamine and terminates in striatum (degenerates in Parkinsonʼs disease) ◆ Pars reticulus- is an output nuclei ● Hemiplegia — Loss of movement in one half of the body ○ Damage to corticospinal tract (ipsilateral if below caudal medulla)

● Central pattern generators: — neural networks limited to the spinal cord which

create patterned motor outputs without commands from brain or sensory feedback (§CREATE PATTERNed motor outputs generally without commands from general environment (sensory feedback) or the general (brain) ○ e.g. cat on treadmill ● What is endpoint control & how is it described? movements are planned based on goal of final location ○ Experiment of monkey pointing to light ● Preferred direction — in a motor pathway, when moving a particular direction, some neurons fire more (somewhat like feature detectors specific to orientation in the visual cortex) ○ Center-out test - monkey moving stick, showed that individual M1 neurons have preferred directions (like some V1 neurons preferring directions) ○ (The center-out task is the task in which a monkey has the stick which he moves in different directions) ● Population vectors -> abridged activity of all neurons ○ Provides better correlation for beha-ViOR than recording individual neurons ● Affordance competition hypothesis & FIG 8.17 — action selection and specification actuated simultaneously (ASASAS) w/in an interactive neural network (INN) ○ In test, cells tune for both possible spatial directions. then (once given cue) increases for the one direction and goes away for other ● Alien hand syndrome — when one limb does a seemingly meaningful action but the person denies responsibility for that action ● Caused by lesions in SMA (Seemingly Meaningful Action; SMA has role in processing sequenced-based behavior, especially rehearsal-based movement) ● BA 6 (medially; alongside premotor cortex); and damage to corpus callosum (coordination of commands between hemispheres is difficult then) Huntington's disease vs. Parkinson's disease ● Hypokinesiam(deficient GABA) & Bradykinesia (deficient dopamine) ● Hypo- reduction or absence of movement ○ brad- slowness in initiation on execution of movements ● Sensorimotor adaptation ● Sensorimotor learning ● Visuomotor adaptation (cf. BA 7) ● Forward models

Adapted and Revised, with Annotations, from Study-Guide-Based Quizlet set: [username withheld for privacy]...