Refleks Arcs

Reflex Arcs – Reflex: An involuntary response to a stimulus: 1. Begins with sensory input 2. Ends with motor response – Reflex Arc is the pathway over which a reflex occurs

Types of Reflex Arcs 1.Visceral (autonomic) reflexes e.g. automatic production of saliva upon, seeing or smelling food 2.Somatic (skeletal) reflexes e.g. movement of a body part in the presence of pain

Sensory Ia & II

Muscle spindle Capsule Intrafusal fibers Stretch receptor Extrafusal fibers

Sensory Ib

Tendon

Organ tendon golgi

Muscle spindle 1. 2.

2~5 thin & short fibers known as intrafusal fibers. Muscle mass known as extrafusal with intrafusal bind at tendon attach to bone. 3. Intrafusal fibers:  Nuclear bag fiber  bulging & many nuclei at center (nuclear bag).  Nuclear chain fiber  thin, short & no nuclear bag

Sensory nerve: 1. Sensory Ia : 

Primary ending / annulospiral into center intrafusal fibers & conduct impulses at high speed

2. Sensory II :  Secondary ending / flower spray at peripheral nuclear bag fiber & conduct impulses at slower rate than Ia.

3. Sensory Ib :  Innervated at organ tendon golgi synapse with motorneuron (autogenic inhibition) conduct impulse at high speed

Muscle Spindle Efferent gamma dynamic

sensory Ia Efferent gamma static Sensory II

Primary ending /annulospiral ending

Secondary Ending / Flower spray ending

Muscle /extrafusal fibers stretch

intrafusal fibers stretch

Nuclear Bag & nuclear chain distorted

AP  conduct via sensory Ia to spinal cord

AP via alpha motor neuron to extrafusal fiber

Muscle or extrafusal : fibers contract

MECHANISM OF ACTION Muscle / extrafusal fibers stretch

Intrafusal fibers stretch 1.

Nuclear bag fiber distort if extrafusal stretch strongly (dynamic/ phasic  involve in movement)  generate AP  fast at primary / annulospiral ending AP conducted by sensory Ia nerve to spinal cord.

2. Nuclear chain fiber distort if extrafusal stretch (reflex static/ tonic  maintain posture)  generate AP  flower spray/ secondary ending AP conducted by sensory II nerve to spinal cord. Synapse at spinal cord & AP transfer to alpha motor neuron into extrafusal fibers

1. Extrafusal fibers / muscle contract fast 2. Extrafusal fibers / muscle contract slowly

Components of somatic reflex arc 1. Sensory receptor 2. Afferent (sensory) neuron 3. May include one or more interneurons 4. Efferent (motor) neuron 5. Efector (skeletal Muscle)

Reflex Arch

3.

2.

4. 1.

5.

Stretch reflex 2 1

4 5

3

The Patellar Tendon Reflex Arc

Type of reflexs 1. Monosynaptic reflex : 

kneel jerk & ankle jerk

2. Polysynaptic reflex : 

withdrawal reflex when touch hot object or step on sharp object

Skeletal Muscle Reflex Sensory Receptors: Proprioceptors 1. Muscle spindle  (In muscles for sense stretch)

2. Golgi tendon organ  (Near tendon & Sense force)

3. Joint receptors  (Sense pressure & Position)

Patellar reflex tests L2, L3, and L4 tracts

mono-synaptic Reflex Achilles reflex tests S1 and S2

2 3

Synapse in spinal cord

1 4 5 Babinski reflex tests mostly S1 and S2 but also L4 and L5

Flexor (withdrawal) reflex is withdrawal of foot Crossed extensor reflex is maintaining balance by extending other leg

Poly-synaptic reflex Inhibitory Synapse via motor neuron to extensor

iv

i

3

Synapse to brain

4 INTERNEURON

iii

4

Sinaps teruja motor neuron keotot ektensor kaki sebelahan

EFFECTORS' (EXTENSOR INHIBIT)

Excitatory synapse via motor neuron to flexsor muscle

2 4

1 RECEPTOR (SKIN)

EFFECTORS' (FLEXOR EXCITE)

ii

3

i ii

Poly-synaptic reflex

2

4 1

iii

Flexion Reflex: Pull away from Painful Stimuli

Reflex Tests • Biceps reflex tests C5 and C6 • Triceps reflex tests C7 and C8 • Brachioradialis reflex tests C5 & C6

Excite Triceps extensor Excite Bicep muscle flexor

Golgi Tendon Reflex: Response to Excessive Force 1. 2. 3. 4.

Myotactic unit: all pathways controlling a joint. Example: elbow joint – all nerves, receptors, muscles. Force pulls collagen fibers which squeeze sensors. Overload causes inhibition of contraction

Protective reflex /Lengthening reflex 1. Muscle stretch  2. Organ tendon golgi active & AP 

3

i

3. afferent nerve Ib 4. Polysynaptic spinal cord i. Inhibitory synapse to motor neuron extensor.

5

ii. Excitation Synapse via motor neuron flexor

1 5. Contraction muscle stop to prevent detach tendon from bone

2

4 ii

Golgi Tendon Reflex 1. Proprioceptors in a tendon near its junction with a muscle -1mm long, encapsulated nerve bundle. 2. Excessive tension on tendon inhibits motor neuronmuscle contraction decreased. 3. Also functions when muscle contracts unevenly

Voluntary Movement: “Conscious”

Rhythmic Movements

1. Cortex initiation 2. Central pattern generators i. In spine ii. Maintain motion

3. Combines movements i. Reflexive ii. Voluntary

Input serat aferen Gamma  1

2

 1

3

3

1. Input implus ke serat eferen  dari Pusat tertinggi otak 2.Gelendung otot terangsang & AP dijenakan di hantar ke korda spina melalui saraf sensori Ia (dinamik) / II (pasif) 3. EPSP & IPSP ke motor ke otot mengecut & relaks.

 Neuron as Servo-mechanism AP motor cortex synapse with gamma motor motor neuron at spinal cord gamma efferent AP conduct to muscle spindle

Intrafusal fiber contract   muscle spindle activity 1.  dynamic  distore anulospiral / primary ending)  flasic Ia    sensitive to velocity  without effect on tonic 2.  static  Distore nuclear chain (secondary ending)  tonic II     tonic level (sensitivity to muscle length) without effect on flasic α motor neuron to extrafusal fiber 1. Muscle Isotonic contraction for movement 2. Muscle Isometric contraction static (maintain posture)