Transcript Motor System

Motor Function of spinal cord
Human Reflexes

What is a reflex?
Functional unit of CNS, involuntary
response to a stimulus
 -example/pinprick

Reflex Arc
-DIF/
- formed of :
-Sense organ (receptor).
-An afferent neuron.
-One or more synapses (CNS).
-An efferent neuron.
-An effector organ
-Bell-Magendi law
Components of reflex arc
**-Afferent

neuron
- Afferent neurons undergo:
1- Divergence WHY?
2- Convergence WHY?
**- Interneurons (excitatory or inhibitory).
- (Two types of circuits formed by inter neurons
(parallel and reverberating circuits).
Reverberating circuits
1- Parallel
2-Reverbrating
Reverberating circuits
--Function
--
In brain and spinal cord
-- Respiration&Wakefulness
Renshaw cells
- located in anterior horn with motor neurons.
-inhibitory (presynaptic inhibition, negative
feedback fashion)
& lateral inhibition to nearby neurons.
Efferent neuron
1.
alpha motor neurons
2.
Gamma motor neurons
Types of reflexes
Stretch reflex
Stretch reflex
-Components:Receptor
Afferent
AHC
Efferent
Effector
:
Stretch Reflex/ example Knee jerk
Stretch reflex receptor ( Muscle Spindle)
Structure of Muscle Spindle:-
Two types of intrafusal fibres:
.
Innervation of the muscle spindle
1-Sensory Afferent fibres:
2-Efferent fibres to spindle
Reaction time/
Central delay/
-Number of synapses
Functions of muscle spindle:-
Types of responses
Component of stretch reflex
1-Dynamic stretch reflex (dynamic or phasic
response)
2- Static stretch reflex( static response
.1
Muscle Tone:- Static stretch reflex
resistance of muscle to stretch
-Stimuli for muscle tone
Dif/
-Present in ?
-hypotonic or flacidity
-hypertonic,spastic muscle
Effect of gamma efferent discharge:a- dynamic gamma efferent
B-Static gamma efferent

Muscle can contract by:-

alpha-gamma linkage(coactivation)
Reciprocal inhibition
IN KNEE JERK/
contraction of EXTENSOR of thigh
relaxation of FLEXORS
>>>>>>>
Physiological Tremor :-.
Higher control on gamma efferent
discharge :1-Cortical areas.
2-Basal ganglia.
3-Brain stem.
Facilitatory
Inhibitory:
4-The cerebellum.
Facilitatory supra spinal centers
Inhibitory supra spinal centers
Factors influence stretch reflex
)
Enhances
Inhibits
Jendrassik’s Maneuver :
The Golgi tendon reflex
(inverse stretch reflex- (AUTOGENIC INHIBITION))
The Golgi tendon reflex (inverse
stretch reflex)
Lengthening Reaction:- response of spastic muscle to
lengthening
Clonus:- as Ankle clonus
Clinical significance of stretch
reflex:-Tendon jerks
Centers of some reflexes
Clinical significant
Centers of some reflexes
Clinical significant
Withdrawal reflex
(flexor reflex)
-Properties of withdrawal R
- crossed extensor reflex
Crossed extensor reflex
Importance of withdrawal reflex:Other examples of polysynaptic reflexes
