Download Golgi Tendon Organs

Spinal Cord
Lec: 4
Assis.Professor Dr. Farah Nabil
Abbas
MBChB, MSc, PhD
Golgi Tendon Organs
Encapsulated sensory receptors.
 Located in tendons near their junction with the
muscle.
 10-15 muscle fibers are connected in series
with each Golgi tendon organ.
 Endings of afferent nerve fibers wrapped
around collagen bundles in tendon.

Golgi Tendon Organs
Contraction of attached extrafusal muscle
fibers  pull on the tendon  straightens
collagen bundles  distorts receptor endings
 activating their afferent neurons
 Transmission of APs to CNS via type Ib nerve
fibers.

• Inhibit via interneurons, of motor neurons
contracting muscle and its synergists.
• Stimulate motor neurons of antagonistic muscles.
to
Inverse Stretch Reflex
Sense Organ
Golgi tendon organ
Afferent Neuron
Ib fiber
Synapse
CNS (spinal cord)
Efferent Neuron
Alpha Motor Neuron
Effector
Muscle (extrafusal muscle)
Importance
1.
2.
Prevent muscle tearing or tendon avulsion
from its attachments to the bone.
Equalize contractile forces of separate
muscle fibers (fibers which exert excess
tension become inhibited by the reflex 
spread muscle load over all fibers 
prevent damage in isolated areas of a
muscle where small numbers of fibers
might be overloaded
Polysynaptic Reflexes
A.
B.
C.
D.
Withdrawal reflex
Crossed-extensor reflex.
Abdominal reflex
Cremasteric reflex
Withdrawal Reflex
Cutaneous sensory stimuli on a limb 
contraction of flexor muscles 
withdrawing limb “flexor reflex" or
"nociceptive reflex" or "pain reflex".
 Polysynaptic reflex
A. Contraction of flexor muscles
B. Inhibition of extensor muscles.

Crossed Extensor Reflex
Application of strong stimulus to a limb.
 Response includes:
A. Flexion and withdrawal of that limb
B. Extension of the opposite limb after 0.20.5 second.

Abdominal Reflex
Superficial reflex
 Thoracic 7th -12th segments
 Polysynaptic
 Subject lie down in the supine position.
 Gently stroke abdominal skin from lateral to
medial aspect in all four quadrant → abdominal
muscles contract → umbilicus deviate towards
the area stimulated.

Absent Abdominal reflex
1.
2.





Physiological (obesity, tolerance, children,
multiparous lax abdominal wall).
Pathological:
Multiple Sclerosis
Motor Neuron Disease
Neurogenic Bladder
Brown-Séquard syndrome
Chiari Malformations
Cremaasteric Reflex
Area A (orange): area of sensory
fibers
controlled
by
the
genitofemoral nerve
Area B (green): area of sensory
fibers controlled by the ilioinguinal
nerve
Arrow C (red): direction and
location where the skin must be
stroked to elicit this reflex.
Functions of Stretch Reflex
1)
Skeletal Muscle Tone:
• Maintenance of erect posture against force of
gravity, by producing a strong muscle tone in the
antigravity muscle.
2)
Damping (smoothing) function:
• Signals discharged to a muscle often have varying
intensities  irregular movements. However
through muscle spindle and alpha-gamma linkage,
signal are adjusted to produce smooth movements.
Functions of Stretch Reflex
3)
Servo-Assist Function: servo = force
regulator:
• Stretch reflex assists the brain to produce and
regulate force of muscle contraction as follow when
the muscle contract:
I. α and γ motor fibers are activated to same degree.
II. Extrafusal & intrafusal muscle fibers equally contracted
and shortened to same degree.
III. Central part of intrafusal muscle fibers does not change,
and intensity of stretch receptor remains unchanged.
Functions of Stretch Reflex
iv. If the muscle tries to left a heavy weight, extrafusal fiber
contract isometrically and intrafusal fibers contract at the
periphery and lengthen central part.
v. Potentiates stretch reflex leading to strong muscle
contraction to help lifting the weight.
4)
Antigravity Function:
• To resist gravity effect which tends to flex muscle of
lower limbs and trunk. Stretched muscles respond
by reflex contraction to maintain upright position of
body and prevent its fall down.
Arrival of
stimulus and
activation of
receptor
Activation of a
sensory neuron
Receptor
Sensation
relayed to
the brain by
collateral
Dorsal
root
REFLEX
ARC
Stimulus
Effector
Ventral
root
Activation of a
motor neuron
Response
by effector
Information
processing
in CNS
KEY
Sensory neuron
(stimulated)
Reflex Action
Excitatory
interneuron
Motor neuron
(stimulated)
Stretching of muscle tendon
stimulates muscle spindles
Muscle spindle
(stretch receptor)
Stretch
Spinal
cord
REFLEX
ARC
Contraction
Activation of motor
neuron produces reflex
muscle contraction