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The document discusses spinal reflexes including stretch reflexes, polysynaptic reflexes, and crossed extensor reflexes. It describes the receptors, reflex arcs, and spinal cord pathways involved in these reflexes. It also mentions how the brain can alter spinal reflexes, giving examples of the plantar reflex and Babinski reflex.
55 part 2.pdf
- 1. 13-7 Spinal Reflexes Musclespindle structure (continued) Dendrites of sensory neurons wind around central region of intrafusal fibers. Sensory neuron axonenters CNS in posterior root Sensory neurons synapse in spinal cord directly with motor neurons .Gammaefferents complete reflex arc by synapsing back atthe intrafusal fibers Muscle contracts back to its resting length 5:20142:26
- 2. Solitary cel Sensary root Dorsalroot ganglion Posterior horn External besalcells Descending -Cornicospinal tract Intermediate zone Intemeurons Antenor hom LGarmma motor neurg ber Antenior motor neurons Alpha motor neuron 1b ber alpha motor Motor endplate neuron Gamma motor Motor roo Skeletal musce neuron Muscie spindle Goig tandon organ Figure 55-1. Comections of perpheral sersory tibesand corb COpna tibers with the nerneurons and anterior motor neuiors of the spend cord Figure 55-2. Penpheral sensory fibers aed anterior motor neurons innerating skeletal musce
- 3. In the stretchreflex, the receptor stimulated is called a muscle. The effector isthe a) Golgi tendon; same b) muscle spindle; same c) Golgi tendon;opposite Stretch Reflex/Myotatic Reflex d) muscle spindle; opposite Receptor- Stretch (muscle spinde) REFLEX ARC Stimulus fector Contrecton Response
- 4. Dorsal root ganglion- PosteriorhomEfferent Aipe molor innervation of Descending Jibers skeletal muscles: intermediate zone- Garma moor neuron Antenior hom Extrafusal fibers Gamma motor neuron 1atber a motor neurons Alpha motor neuron 1b fiber Intrafusal fibers-y Motor end piate motor neurons Exmua musoetbe Skeletal muscle Mace spindie Golg tendon organ sce Figure 55-2. Perpheral sensory fibers and anterior motor neurons innervating sieietal muscie
- 5. MUSCLE SENSORY RECEPTORS: TYPESSTIMULUs 1. MUSCLE SPINDLE Stretch; Rate of Stretch 2. GOLGI TENDON ORGAN Tension
- 6. Extratusal fibers Muscle FlowerspRy sensory neurons Gamma fferent ersto intratusal hbers Spindle Aipha motor neuron to extrafusa tbers Annulospral sensory neurons Gamma efterent tibers to ntratusai bers Nuciear chan ber intrausa fibers 1) Stretch Nucear bag foer 2)Speed of Stretch
- 7. A weight lifteris straining to lift a 200-kg barbell. Shortly after he lifts it to chest height, his muscles appear to relax and he drops thebarbell Which reflex has occurred? a) withdrawal reflex b) stretch reflex c) crossed extensor reflex c) d) tendon reflex 9:59142:26
- 8. X Application oftheGolgiTendonOrganJGTps) Even if the biceps brachii could somehow generate enough forceto cul 2000 lbs, the tendon is not strong enough to support the combined weighs,of the bone and enormous barbel. Muscles Absurd Type Ib afferent Golgi tendon organ Collagen Bone Tendon Tear 10:4 04614226
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- 10. Motor Motor Sensory la 17um MOTOR NERVES: 14m 5um 8um5 um alpha-Extrafusalmusclefibers Gamma-Intrafusal muscle fibers (endportions) SENSORY NERVES: Central portionof intrafusal muscle fibers Extrafusal fibers Sheath Aipha motor ending Primary ending Intrafusal fibers la- Primary ending I1-Secondary ending Gamma motor Fluid Secondary ending ending cavity 1 cm Figure 55-3. Muscle spindie, showing its relationship to the large extrafusal skeletal muscle fibers. Note also both motor and sensory innervation of the muscle spindle
- 11. TYPES OF INTRAFUSAL MUSCLEFIBERS SENSORY NERVE ENDING STIMULATED Dynamic y fiber (efferent) Staticy tiber (efterent) Group la fiber (primaryafferent) Group il fibers (secondary afferent) Piate ending 1.Nuclearbag Primary nerve ending Nuclear bag fiber (intrafusal muscle) 2. Nuclear chain Primary ending Secondary ending Nuclear chain fibaor (intrafusal muscle) nerve Trail ending Figure 55-4. Detals of nere connections from the nuckear bag and nuciearchainmuscie spindie fibers. (Modifiedfrom Stein RB:Periph eralcontrol ofmovement. Physiol Rev 54.225, 1974) nerve TYPES OF RESPONSES OF MUSCLE SPINDLES Static Response Stretch; if the receptor of the muscle spindle is stretched slowly 1 2. Dynamic Response - Rate ofstretch 3:52142:26
- 12. 13-7 Spinal Reflexes Posturalreflexes Include both stretch reflexes (monosynaptic) and also complex polysynaptic reflexes Maintain normal upright posture Often involve multiple muscle groups (e.g., back and abdominal muscles) Maintain firm muscle tone Extremely sensitive receptors allow constantfine adjustments to be made as needed
- 13. 13-7 Spinal Reflexes Polysynapticreflexes More complicated than monosynaptic reflexes Interneuronscan control multiple muscle groups Produce either EPSPsor IPSPs, stimulating some muscles and inhibiting others. Examples Tendon reflex Withdrawal reflexes Crossed-extensor reflexes
- 14. 13-7 Spinal Reflexes Thetendon reflex Prevents skeletal muscles from: Developing too much tension Tearing orbreaking tendons Sensory receptors are Golgi tendon organs Stimulated when collagen fibers are overstretched Stimulate inhibitory interneurons in spinal cord More muscle tension leads to more muscle inhibition 5:10142:26
- 15. 13-7 Spinal Reflexes Withdrawalreflexes Move body part awayfrom stimulus (pain or pressure) Example: flexor reflex in limbs; pullshandfrom hot pan Strength and extent of response dependson intensity and location of stimulus Reciprocal inhibition Forflexor reflex to work, stretch reflex of antagonistic (extensor) muscles must be inhibited(reciprocalI inhibition) by interneurons in spinal cord. When flexors contract, extensors relax When extensors contract, flexors relax 551 142:26
- 16. Withdrawal Reflex Distribution withingray matter horns to other segments of thespinal cord Painful stimulus Flexors stimulated Extensors inhiblted 7:01/42:26
- 17. You've just toucheda hot stove.What type of reflex did you experience? In what way was your brain involved in the reflex? a) cranial;the somatosensory cortex b) visceral; only tracts that respond to pain b) c) complex; all the sensory tracts d) spinal; it was not involved 7:21/42:26
- 18. 13-7 Spinal Reflexes Reflexarcs Ipsilateral reflex arcs Occur on same side of body as stimulus Stretch,tendon,andwithdrawalreflexes Crossed extensor reflexes involve contralateral reflex arcs Occur on side opposite stimulus
- 19. 13-7 Spinal Reflexes Crossedextensorreflexes .Coordinated with flexor reflex Step on something sharp; before flexorreflex can lift injured foot, crossed extensor reflex straightens oppositelimb to receive body weight, then flexor reflex can occur .Maintained by reverberating circuits 8:43/42:26
- 20. During a withdrawalreflex, the limb on the side opposite the stimulus called a .This response is a) flexes; stretch reflex b) adducts; tendon reflex c) extends; crossed extensor reflex d) abducts; tendon reflex 9:00/4226
- 21. aCrossed Extensor Reflex Tomotorneurons in other segments of the spinal cord Extensors. inhibited Flexors - Extensors stimulated stimulated Flexors inhibited KEY Sensoryneuron ----Motor neuron (stimulated) (inhiblted) Excitatory intermeuron --Inhibltory interneuron Motor neuron 29142.26nuh
- 22. 13-8 The BrainCan Alter Spinal Reflexes Plantar reflex Normal in adults Stroke lateral sole, causes reflexive toe-curling TheBabinski reflex Normal ininfants May indicate CNS damage in adults 0:17/42:26
- 23. After injuring herback, 18-year-old Tina exhibits a positive Babinski reflex. What does this imply about Tina's injury? a) possible paraplegia b) possible damageto sensory tracts to foot b) possible damage to ascending tracts in spinal cord c) d) possible damage to descending tracts in the spinal cord 0:44/ 42-26
- 24. After injuring herback, 18-year-old Tina exhibits apositive Babinski reflex. What does this imply about Tina's injury? a) possible paraplegia b) possible damage to sensory tracts to foot b) c) possible damage to ascending tracts in spinal cord d) possible damage to descending tracts in the spinal cord 1:00/ 42:26
- 25. aThe plantar reflex,a curling of the toes, is seen in healthy adults. bThe Babinski reflex occurs without descending inhibition. It is normal in infants, but pathological in adults.