Download Structural elements and mechanisms involved in the transformation

Shokoya Mariam Majida
MOTOR NEURON:
 Cell body located in the spinal cord
 Axon is efferent, it carries information from the spinal cord to the effectors in
the PNS (muscles and glands)
 Two main categories : Somatic / Visceral motor neurons
Somatic motor neurons:
 Originate from CNS direct axons to skeletal muscles  control locomotion
Types of efferent motor neurons: Alpha / Beta / Gamma motor neurons
Types of muscle fibers they innervate: Intrafusal / Extrafusal muscle fibers
Extrafusal muscle fibers:
• generate tension  allow skeletal movement
• mostly striated fibers attached to the bone by tendons
• innervated by ALPHA motor neurons :
cell body in ventral horn of the spinal cord
contribute to maintain muscle tone  resist further stretches
Intrafusal muscle fibers:
• serve as sensory organs  detect the amount of change in the muscle
• innervated by both sensory afferent and motor efferent neurons
• Motor neurons are BETA and GAMMA
beta: axon collateral to extrafusal muscle
gamma: regulate sensitivity of the fiber to stretching
Visceral motor neurons:
 indirectly innervate cardiac muscle, smooth muscle and glands
 disynaptic command: visceral motor neuron (CNS) 
 ganglionic neuron (PNS)  visceral muscles (PNS)
 sypmpathetic (noradrenalin release) or parasympathetic (acetylcholin release)
nerve fibers
Basicly all motor neurons release acetylcholin.
Neuromuscular junction:
 action potencial
 Calcium ion inflow in axon terminal
 fusion of synaptic vesicles  release
Acetylcholin
 postsynaptic membrane: binding to
nicotinic acetylcholin receptors
 depolarization of muscle fiber 
contraction
Thank you for your attention!
Sources:
https://en.wikipedia.org/wiki/Intrafusal_muscle_fiber
https://en.wikipedia.org/wiki/Extrafusal_muscle_fiber
https://en.wikipedia.org/wiki/Motor_neuron
https://en.wikipedia.org/wiki/Alpha_motor_neuron
https://en.wikipedia.org/wiki/Neuromuscular_junction
https://en.wikipedia.org/wiki/General_visceral_efferent_fibers
https://en.wikipedia.org/wiki/Muscle_spindle