Spinal Cord and the Somatic Motor System-Lecture 13 Exam 3 Flashcards
Divisions/Segments of the Spinal Cord
-Cervical (C1 – C8)
-Thoracic (T1 – T12)
-Lumbar (L1 – L5)
-Sacral (S1 – S5)
Cross-Sectional Spinal Cord Anatomy
White Matter & Gray Matter
Dorsal/Posterior Horn
-Somatic sensory (afferent) neurons travel through the spinal nerve then through the dorsal/posterior root & synapse in the dorsal horn
-Carry sensory information from the body to the spinal cord
Dorsal/Posterior Root Ganglia
Contains sensory neuron cell bodies
Ventral/Anterior Horn
-Contains somatic motor neuron cell bodies
-Somatic motor (efferent) axons travel through the ventral root then
through the spinal nerve to skeletal muscles
-Transmit voluntary motor information from spinal cord to skeletal muscles
Dorsal Root
Above & diagonal of ventral root
Ventral Root
Below & diagonal of dorsal root
Spinal Nerve
Where dorsal root and ventral root come close to contact heading towards somatic neurons
Lateral Corticospinal Tract (descending)
Voluntary motor control of skeletal muscles
Lateral Spinothalamic Tract (ascending)
Sensory info about pain & temperature
Ventral Spinothalamic Tract (ascending)
Sensory info about touch
White Matter (outer portion)
Myelinated axons (fiber tracts)
Gray Matter (inner portion)
-Neuron cell bodies, unmyelinated axons, axon terminals
-Dorsal (posterior) horn: sensory neuron axon terminals
-Ventral (anterior) horn: motor neuron cell bodies
-Lateral horn: (between T1 and L2) ANS cell bodies
Components of Neuromuscular Junction
-Somatic Motor Neuron
-Synaptic Cleft
-Skeletal Muscle Fiber
Somatic Motor Neuron
-Presynaptic axon terminal with ACh-filled vesicles
-Cell body originates in the ventral horn of the spinal cord
-Synapses directly onto skeletal muscle (target) & releases ACh
-Axon branches at its terminal end to innervate more than one skeletal
muscle fiber
Skeletal Muscle Fiber
Postsynaptic membrane (motor end plate) with nicotinic receptors
Synaptic Cleft
The gap between neurons that allows chemical signals to pass between them