4.1 motor functions of the spinal cord, cord reflexes

CNS upper and lower motor neurons lower motor neurons -inside extrafusal/skeletal muscle fiber that goes from tendon to tendon you have interfusal fibers aka ____ --as extrafusal is stretched so is intrafusal/spindle ---sensory/afferent component = signaling muscle getting longer/shorter ---small motor componont = allows intrafusal/spindal to ___

--muscle spindle ---change length with the muscle to keep tabs on it

CNS upper and lower motor neurons upper motor neurons -motor neurons originate in the --____ gyrus of --____ cortex -activate _____

--precentral --motor -lower motor neurons

Transmission of Muscle Length and Tension Information to Higher Centers •Signal from Muscle Spindle and Golgi tendon are also transmitted to higher centers (not just the cord)—will be cognizant of it •This informs brain of instantaneous changes in muscle tension (____) and length (___) •Information is transmitted via ______pathway (fast sensory) at 120 m/sec •Important for feedback control of motor activity (discussed later) -feedback type = _______—can make corrective changes before next movement**

-GTO -muscle spindle -DCML -feed forward

autonomic motor neurons (not somatic/skeletal motor) -cell bodies located on the ___ horn of SC grey matter withing the ______ column --this column is only present in the thoracolumbar regions sympathetic pre-gang neurons -type ____ fibers --(not A orC) -between cord levels ____ --thoracolumbar -synapse with post-gang neurons in --____muscle --____ muscle --____

-LATERAL -intermediolateral (IML) SNS -type B -T1-L2 cardiac smooth glands

Flexor (Pain or Withdrawal) Reflex and Crossed Extensor Reflex -Receptor: _____activates AP in afferent neuron; -transmitted to dorsal root of SC and enters SC -branches into several collaterals -Collaterals synapse with several interneurons ipsilateral and contralateral CONTRALATERALLY = crossed extensor reflex -Pain elicits an extensor reflex in opposite limb -Extensor reflex begins 0.2-0.5 seconds after flexor reflex -Serves to push body ____, also to _____to opposite limb 1-Contralateral extensors contract -quad -plantar flexor 2-Contralateral flexors inhibited -semitendinosis -dorsiflexors

-Nociceptor -away from stimulus -shift weight

Flexor (Pain or Withdrawal) Reflex and Crossed Extensor Reflex -Receptor: _____activates AP in afferent neuron; -transmitted to dorsal root of SC and enters SC -branches into several collaterals -Collaterals synapse with several interneurons ipsilateral and contralateral IPSILATERALLY=Flexor reflex -Diverge to ipsilateral muscles for ___ from stimulus: 1-excite agonist flexor muscles (semitendinosus and dorsiflexors) and cause contraction 2-inhibit antagonist extensor muscle (quad) from contraction -Activate reverberating circuits to prolong contraction -Duration of after-discharge depends on stimulus strength

-Nociceptor -withdrawal

somatic/non-direct skeletal/helper motor neurons Interneurons--RENSHAW cells -located in the ____ horn of SC grey matter -____ neurons that release ____ -an axon collateral off a motor neuron can synapse with a renshaw cell/inhibitory interneuron -it can a-synapse with an adjacent motor neuron and produce ____ inhibition because it is not needed in a specific motor action b-synapse with the same axon that stimulated it and inhibit it to ____

-VENTRAL -inhibitory -glycine a-lateral b-regulate output

somatic/skeletal motor neurons -cell bodies located on the ____ horn of SC grey matter -2 types of motor neurons

-VENTRAL/ anterior -A-alpha -A-gamma

Cord Reflexes that Cause Muscle Spasms Pain signals can cause reflex activation and spasm of local muscles -Pain receptors in broken bones stimulate muscle contractions that can be very forceful- ____ can relieve spasms -Inflammation of peritoneum can cause abdominal muscle spasm -Muscle cramps caused by painful stimuli in the muscle --Can be due to cold, ischemia/tunaquit, or over-activity. --Reflex contraction increases painful stimulus and causes more muscle contraction—___ feedback

-anesthesia local/regional -positive

motor neurons are utilized in both the ____ /__and____/__nervous systems

-autonomic/ involuntary -somatic/voluntary

voluntary (somatic) activity ____ and _____ cerebellum are part of the feedback circuit to the ____ and _____ that PLAN and ORGANIZE VOLUNTARY movement

-basal ganglia -lateral cerebellum -premotor -motor cortex

voluntary (somatic) activity activity is planned in the ___ commands are sent to muscles via ____ tracts 1-cranial = 2-spinal =

-brain -pyramidal --corticobulbar --corticospinal

voluntary (somatic) activity POSTURE is continually adjusted before and during movement by info carried in 1-descending _____ pathways 2-peripheral _____ pathways

-brainstem -afferent/ proprioceptive/ sensory

how is spinal cord involved in voluntary (somatic) motor function -majority as a ____ for CNS to peripheral nerve fibers -also involved in *_____ circuits for walking and various ____ --contained within the spinal cord --higher brain centers _____ and ____ these circuits/reflexes ---walking ---maintaining equilibrium

-conduit -neuronal -reflexes --activate --command

CNS upper and lower motor neurons upper motor neurons 2 tracts down -______ cortical/1st neuron axons will end up synapsing/projecting to CN ___+___+___ = lower motor -_____ cortical/1st neuron axons will end up synapsing/projecting to _____ motor neurons = lower motor --______ or ______enlargements

-cortic-bulbar -5 trigeminal -7 facial -12 hypoglossal -cortico-spinal -spinal motor --cervical --lumbar

PNS composed of -__nerves -__nerves -__nerves contains -___neurons -___neurons

-cranial -spinal -peripheral -sensory -motor

CNS upper and lower motor neurons lower motor neurons -_____ and ____ motor neurons that innervate ____ ___ -includes what type of motor fibers/neurons 1- 2- 3-

-cranial -spinal -skeletal muscle 1-A alpha 2-A-beta--? 3-A gamma

Autonomic Reflexes in the Spinal Cord -Segmental autonomic reflexes 2-Spinal cord transection and shock •Transection causes ____ cord reflexes- spinal shock** •Spinal neurons may regain some function in several weeks- or become____** •Arterial BP falls to as low as 40 mmHg- indicating _____ •Skeletal muscle reflexes blocked then return- ___reflex first to return--monosynaptic •Sacral reflexes for Bladder and bowel control suppressed then return weeks later

-depressed - hyperexcitable -sympathetic blockade -stretch

Reciprocal Inhibition -the inhibition of opposing muscle that would prevent the -When a specific muscle contracts, opposing muscles must relax to ____ When the flexors contract, the extensors relax When the extensors contract, the flexors relax

-desired movement -permit the movement.

muscle-tendon receptor #2: Golgi Tendon Organs •Function is to _____contractile forces among muscle fibers --Prevents excess ____ on muscle tendons •Only affects an individual muscle (____muscles are not affected)

-equilize -tension -adjacent

Autonomic Reflexes in the Spinal Cord -Segmental autonomic reflexes 1-Mass reflex -occurs when the spinal cord becomes ____ active •A major portion of the skeletal muscles go into strong ____spasm -•Not common in humans but does happen from huge _____stimulation •Colon and bladder are likely to evacuate •Arterial pressure may exceed 200 mmHg •Large areas of body sweat profusely •When horses get scared, evacuate to get lighter

-excessively -flexor -sympathetic

Other Reflexes for Posture and Locomotion •Pressure on bottom of feet causes ____ reflex -More complex than flexor-crossed extensor reflex •Basic walking reflexes reside in the ____ •Scratch reflex (dog)- highly developed reflex in some animals -Position sense locates exact point of irritation -Scratching movement pattern generated in spinal cord --continues until trigger is releived

-extensor -spinal cord

Flexor (Pain or Withdrawal) Reflex and Crossed Extensor Reflex A painful stimulus causes 1-ipsilateral _______ and --flexor reflex 2-contralateral ______ --crossed extensor reflex

-flextion -extension

muscle-tendon receptor #2: Golgi Tendon Organs -receptor sensing = •_____-threshold mechanoreceptors located in ____ •Increased muscle tension compresses nerve endings, opening ____-sensitive ___channels •Autogenic ____ reflex: a sudden ___ of muscle at very high muscle tensions (protects against muscle ___) •However, Golgi tendon organs signal muscle force through the entire ______, not only at high levels of tension.

-force -Low -tendons -stretch sensitive -ion -inhibition -relaxation -tear -physiological range

interneurons (CNS) are able to ____ info so -brain can receive and efferents can send ____ ____

-inhibit -more specific signals

Sensory Receptors of Muscle --Sense the Dynamic State of Muscle Afferent signals from muscle sensory receptors are mainly for ___ muscle control of voluntary/somatic system. They (mainly) occur ____. They transmit information to cerebrum and cerebellum (as well as to spinal cord).

-intrinsic -subconsciously

somatic/skeletal motor neurons A-Alpha motor neurons •Transmit _____ sized-type Aα fibers --end of motor neuron called ___ aka ____ •a single A-alpha stimulation can excite 3 to >100 ____muscle fibers collectively called a _____ --innervates the extrafusal motor unit sarcolemma in the belly of the muscle (protected) A-Gamma motor neurons •Transmit ____sized-type Aγ fibers •Stimulation excites _____fibers, in _____, a special type of sensory receptor.

-large -motor end plate/NMJ -extrafusal -motor unit -small -intrafusal -muscle spindle

The Muscle Spindle Detects static and dynamic changes in muscle length INTRAFUSAL fibers--2 types: (motor innv = A-gamma) 1-nuclear bag = fast/dynamic -A-alpha sensory 2-nuclear chain = static/posture -A-beta sensory Density varies according to function -Larger muscles with coarse movements have ____ muscle spindles (e.g., quadriceps) -Smaller muscles with fine movements have _____ muscle spindles (e.g., extraocular muscles, hand muscles)

-less -more

Muscle force reflex Golgi Tendon Organ reflex -mono or polysynaptic -aka interneuron or no

-polysynaptic

CNS composed of -brain -spinal cord contains -____/__ neurons

-relay -interneurons

basic spinal reflex arc "Reflex arc" is the wiring of a ___ Basic Spinal reflex arc = ___synaptic --the simplest arc --what is polysynaptic? -begins at a peripheral receptor (____) -end at a peripheral effector (____) 1-sensory organ =Receptor stimulated -nonpropagated graded response occurs that is proportional to the magnitude of the stimulus 2- AP eventually generated down afferent sensory neuron 3-sensory neuron synapses in spinal cord 4-spinal cord -afferent sensory nonpropagated graded response occurs that is proportional to the magnitude of the stimulus = if enough EPSPs = AP generated down efferent motor neuron (-Interneurons typically present = typically sending IPSPs = polysynaptic) 5-AP generated down efferent motor neuron 4-Efferent motor neuron innervates an effector organ at NMJ -The response at the NMJ is also graded, though under normal conditions it is always large enough to produce a response in skeletal muscle = AP generated 5-Efferent organ /skeletal muscle fiber carries AP down fiver

-single reflex -mono -involve at least 1 interneuron -(sensory organ) -(skeletal muscle)

Types of Muscle Fibers •Extrafusal fibers generate ____ -Bulk of muscle tissue -Stimulated by A-alpha motor neurons -heavy myelinated/fast •Intrafusal fibers within ____ which control basic _____ -Arranged in ____ within extrafusal muscle fibers -Smaller, shorter, and _____ in ____to form muscle spindles -stimulated by A-____ motor neurons -afferent sensory neuron = 2 -a muscle relaxant/paralytic will remove this baseline tone = pain after OR

-skeletal muscle contraction muscle spindle muscle tone parallel encapsulated in sheaths -gamma -A-alpha / A-beta

voluntary (somatic) activity works in conjuction with these 3 -_____ - brain + ____ -cerebellum + ____

-spinal cord -brainstem -basal ganglia

integration of sensory inputs from - - (subcortical) -(highest) is then processed and regulated, coordinated to -induce ____ activity -adjust body ____ -make movements ____ and ____ CNS produce 2 types of motor output 1-____ --includes rhythmic movements/circuits like walking that are subject to ____ adjustment 2-___

-spinal cord -subcortical --dienceph, brainstem -sensory cortex/post-central gyrus -induce voluntary activity -adjust body posture -smooth and precise 1-reflex/involuntary -voluntary 2-voluntary

Autonomic Reflexes in the Spinal Cord -Segmental autonomic reflexes --Changes in ____tone resulting from changes in local skin temperature, also sweating, GI reflexes

-vascular

The Muscle Spindle Detects static and dynamic changes in muscle length INTRAFUSAL fibers--2 types: (motor innv = A-gamma) 1-Nuclear ____ intrafusal fibers --larger --detect fast _____ rate of change in length --more locomotive sensory afferents = ___ 2-Nuclear _____ intrafusal fibers --smaller --detect _____ changes in length --more postural sensory afferents = __

1-bag -dynamic A-alpha / type 1a 2-chain -static A-beta /type 2

The Muscle Stretch Reflex- Monosynaptic Reflex Arc 1.Sudden stretch of muscle excites ___ 2.Muscle spindle is connected to the axon of a primary afferent neuron DRG of SC = ____ 3.Single synapse with a ventral horn ____ neuron, axon exits ventral root to spinal nerve of stretched muscled 4.AP to stretched muscle stimulates ____ --function = ____ placed on that muscle 5.**At same time synergistic muscles are activated; --outside of this arc--antagonistic muscles are ____**

1-muscle spindle 2-A-alpha sensory neuron 3-A-alpha motor neuron 4-contraction --opposes stretch 5-inhibited

Sensory Receptors of Muscle --Sense the Dynamic State of Muscle 1-Muscle Spindle -Receptor sensing ____ --AKA muscle ____ and ___ in length -afferent signals sent via __2__ -Located throughout muscle -Intrafusal fibers -Arranged in parallel with extrafusal fibers --adapting in length via ____**still sensory function 2-Golgi Tendon Organ -Receptor sensing ___ -Located in ____ -Arranged in ____ with ___fibers --AKA gauges the force generated by a muscle (____) and ____in tension—and then IINHIBIT -afferent signals sent via___

1-stretch -- length and rate of change in length -A-alpha/A-beta --A-gamma 2-force -tendon -series -extrafusal -tension and -rate of change -A-

somatic NS/motor function 3 inputs to A-alpha lower motor neurons for skeletal muscle function 1-descending pathways --from ____motor neurons that end _____ on A-alpha motor neurons --often _____ --come from corticobulbar or corticospinal descending tracts 2-____ spinal neurons --extensive circuit of spinal ____ that exert their effects on other interneurons --often _____ and ____ from spinal circuits aka central_____ generators --walking, reflexes 3-_____ afferents --____ neurons from muscle _____ providing feedback about muscle length and tension --spinal block/swelling removes this proprioception

1-upper -directly --inhibitory 2-other --interneurons --excitatory and inhibitory --central pattern 3-peripheral --sensory --proprioceptors

Muscle force reflex Golgi Tendon Organ reflex •Number of synapses: _____reflex arc aka _____ •Stimulus: _____ created from _____ •Afferent fibers: •Response: ____of muscle

Disynaptic polysynaptic tension muscle stretch A-alpha/type 1B relaxation

Example of Monosynaptic Reflex Arc- the Patellar Reflex (knee jerk) 1.Strike patellar tendon with tendon hammer 2.Muscle spindle stretches (in quadriceps femoris) 3.A-alpha/Type Ia afferent stimulates A-alpha motor neuron in L4 (without interneurons - monosynaptic reflex arc) 4.A-alpha motor neuron stimulates quadriceps to contract 5.Leg kicks AT THE SAME TIME-this polysynaptic response is occuring 2.Muscle spindle stretches (in quadriceps femoris) 3.SAME A-alpha/Type Ia afferent stimulates an INTERNEURON 6.Antagonistic flexor (hamstring) relaxes via inhibitory interneuron.

areflexia L2-L4 C5-C6

Example of Monosynaptic Reflex Arc- the Patellar Reflex (knee jerk) Multiple oscillations of leg is sign of a cerebellar disease--antagonistic integration--which does use an interneuron--not functioning A lesion in ANY part of the myotactic reflex will result in ____ tested to see where the lesion is --The deep tendon reflexes associated with their spinal segments are used for neurologic examination- for example- L__-L__ for the knee C__-C__ for biceps

areflexia L2-L4 C5-C6

voluntary (somatic) activity movement is SMOOTHED and COORDINATED by the -_______: ______ and _____ portions

cerebellum -medial -intermediate

somatic/non-direct skeletal/helper motor neurons Interneurons/association neurons /internuncial •Cell bodies are located entirely in _____not one specific spot •millions of them--__ x more abundant than anterior motor neurons •____size and ____ excitable •Function is ____—of multiple pathways •Receive information from afferent neurons and transmit impulses to ____ or ____ -more excitatory or inhibitory?* •Most signals from the ___ terminate on interneurons* •Comprise ____ circuitry for especially for motor ____

gray matter 30x small highly integration other interneurons efferent neurons brain neural reflexes

The Muscle Spindle: Physiologic Function 1-Comparator of length between the____and ____muscle fiber •When the muscle is stretched = spindle length is stretched = senses too much = --Leads to the ____ reflex*** Purpose = _____ a change in muscle length

intrafusal and extrafusal stretch Oppose

The Muscle Spindle Detects static and dynamic changes in ____ •Intrafusal fibers = 3 to 12 per spindle -No actin/myosin in center of fiber because NO contraction in center --center functions as ___ receptor --Innervated by gamma motor neurons (type Aγ)

muscle length -sensory

The Muscle Stretch Reflex- Monosynaptic Reflex Arc -Receptor = -Stimulus = -Afferent fiber = -Number of synapses = -where? ___horn -efferent fiber = -Response = monosynaptic reflex arc—no pathway to _____ -no thinking about it -afferent synapses with efferent = involuntary

muscle spindle muscle stretch A-alpha/Type Ia 1 synapse anterior horn SC A-alpha contraction of muscle brain

Reciprocal Inhibition Reciprocal innervation- the ____ circuit that causes reciprocal relation can exist: 1-Between ipsilateral muscles 2-Between contralateral muscles Walking: arms and legs moving opposite from each other -Has to involve all muscle groups •What's going on in opposite extremity if step on something

neuronal

Motor Organization of Spinal Cord -AFFERENT sensory fibers (a-beta/a-delta/c) enter cord and are transmitted to higher centers via 1-DCML 2-spinothalamic/anterolateral Or they synapse locally to elicit 3-motor reflexes --Only a few sensory signals terminate directly on anterior motor neurons (monosynaptic) --Most signals transmitted first through interneurons (polysynaptic) ---organized in ____ pools that streamline through inhibition -EFFERENT motor neurons/a-alpha fibers are located in the _____portion of the cord -Motor neurons are _____% bigger than other neurons.

neuronal pools anterior 50- 100

nerve fiber info sensory function: A-alpha = (1) via 1a and 1b = A-beta = (2) A-delta = C = motor function: A-alpha = (1) A-gamma = (1) B = (1)

sensory -proprioception via 1a-muscle spindle/intrafusal 1b-golgi tendon organ -touch/pressure -fast pain/cold -slow pain/cold and warm motor -somatic motor/skeletal muscle/extrafusal -motor to muscle spindle/intrafusal -sympathetic fibers between T1-L2

The Muscle Stretch Reflex Stretch Reflex (Myotactic reflex) •The ____ manifestation of muscle spindle function •Protects skeletal muscle from _____ •The only _____ reflex***

simplest excessive stretching monosynaptic

somatic NS/motor function -depends ultimately on the activity of the output neurons aka 1- or 2- that innervate skeletal muscle somatic motor fiber type = _____ lower motor neurons --supply ___ ___

spinal motor neurons motor neurons of cranial nerves -A alpha -skeletal muscle

somatic/non-direct skeletal/helper motor neurons Propriospinal fibers -travel along propriospinal tracts = outline of butterfly--see pic -Allow connections to ___for 1- 2 segments* 1-Provides pathways for ____ reflexes that integrate ____ ex: Coordinating 4 legged walking movements, swinging arms and legs 2-Also important for _____ in terms of locomotion and posture

travel up and down cord multisegmental limb movement proprioception