write down the property of synapse

  1. Unidirectional communication: Synapses transmit information in one direction, from the presynaptic neuron to the postsynaptic neuron.
  2. Chemical signaling: Synapses use chemical neurotransmitters to transmit information between neurons.
  3. Plasticity: Synapses can undergo structural and functional changes in response to activity and experience, a property known as synaptic plasticity.
  4. Spatial and temporal summation: Synaptic inputs can be integrated through spatial and temporal summation, where the combined effect of multiple inputs determines whether a neuron fires an action potential or not.
  5. Synaptic delay:  Due to various mechanisms involved in the synaptic trans- mission, some time is lapsed at the synapse. This delay at the synapse is called synaptic delay. For one synapse, the delay is 0.5 msec. 
  6. Fatigue
  7. occlusion
  8. subluminal fringe
  9. convergence and divergence

write down the property of reflex

  1. Involuntary: Reflexes are automatic and occur without conscious thought or effort.
  2. Rapid: Reflexes typically occur quickly, within a few hundred milliseconds of the stimulus.
  3. Stereotyped: Reflexes have a fixed and predictable response pattern that does not vary from one instance to another.
  4. Protective: Many reflexes serve a protective function, such as withdrawing from a painful stimulus or blinking in response to an object coming toward the eye.
  5. Can be modified: Reflexes can be modified by experience and learning, although the basic response pattern remains intact.
  6. Involves neural circuitry: Reflexes involve a neural circuit that includes a sensory receptor, an afferent neuron, one or more interneurons, and an efferent neuron that activates the reflex response.

write short note on muscle tone

Resistance of the muscle to stretch due to continuous state of tension in the muscle is called muscle tone
Control of muscle tone:
• Muscle tone is purely a spinal segmental reflex.
• Produced by continuous, asynchronous, low frequency discharge from anterior horn motor neurons.
• This depends upon the activation of muscle spindle & stretch reflex.
Role of muscle Spindle
• Receptor organ present in the muscle
• Consists of infrafusal fibers (nuclear bag and nuclear chain fibers)
  Sensory supply
▪     Group-Ia (annulospiral ending) – supply both fibers
▪     Group-II (Flower spray endings) – supply only nuclear chain fibers
Motor nerve supply
    Gamma motor neuron
Muscle spindle participate in stretch reflex which play an important role in regulation of muscle tone and posture.
Role of stretch reflex
  Reflex arc:
• Receptor – Muscle spindle
• Stimulus – Stretch
• Afferent – Group Ia & II fibers
• Center – Spinal Cord
• Efferent limb – motor nerve fiber ( α motor neuron)
• Response: Contraction of extra fusal fibers
Two types of reflexes:-
     1)Dynamic stretch reflex: (phasic stretch reflex)
     Activation of Group Ia fibers – contraction of agonist muscle and relaxation of antagonistic muscle (helps is movement)
     2)Tonic stretch reflex:
        Activation of Group Ia & II fibers – continuous steady contraction of the antigravity muscles due to asynchoronous discharge of motor units         supplying the muscle (necessary for maintaining muscle tone and posture)
Role of γ motor neurons on muscle tone
• γ motor neuron increases the sensitivity of muscle spindle to stretch
• increase inγ motor (gamma motor) neuron discharge increases muscle tone
• γ motor neuron discharge is increased in following conditions-
i) noxious (painful) stimulation of skin
ii) anxiety
iii) Jendrassik phenomenon

Role of higher centers in regulation of muscle tone

Brain stem reticular formation
Facilitatory reticulospinal tract Pons                                                                      Inhibitory reticulospinal tract(Medulla)
Facilitates motor neuron discharge                                                                           Inhibits motor neuron discharge
         ↑muscle tone                                                                                                                                   ↓muscle tone  

Cerebellum: Increases muscle tone by
           Facilitating motor cortex
           Facilitating descending pathways
Cereberal cortex

cereberal cortex                     ⟶             indirect pathway
     ↓                                                              ↓
pyramidal tract                               brain stem nuclei
     ↓                                                              ↓
facilitates muscle tone                  inhibits muscle tone


Hypotonia: ↓in muscle tone (lower motor neuron lesion & cerebellar lesion)
Hypertonia: ↑ in muscle tone (UMN lesion)
Spasticity – hypertonia only in antagonistic muscles (clasp knife rigidity)
                  e.g Hemiplegia due to pyramidal lesion
Rigidity: Hypertonia in both agonistic & antagonistic muscle
                   e.g Basal ganglia lesion – Parkinsonism