Summary of Neurology | Spinal Cord: Stretch Reflex | Muscle Spindle

00:00:00 - 00:30:00

The video discusses the muscle spindle, stretch reflex, and how it works. The muscle spindle is a muscle receptor that can detect mechanical stimulation and generate a stretch reflex. The stretch reflex activates the sensory fibers of the muscle spindle, which then generate an action potential. This reflex is important because it can be used to control movement.

• 00:00:00 The stretch reflex is a reflex that enables skeletal muscles to generate movement. The intrafusal muscle fibers are proprioceptors that help the individual to maintain their position in space.
• 00:05:00 The video discusses the different types of intrafusal fibers and how they affect the stretch reflex. The nuclear bag and nuclear chain fibers are more sensitive to length and velocity, respectively, while the type 1a fibers are more sensitive to degree of stretch.
• 00:10:00 This video explains the importance of type 1a and type 2 sensory fibers in the spinal cord. These fibers pick up the degree of stretch or speed at which they are being stretched. The video also discusses the role of gamma motor neurons in causing contraction at the ends of the intrafusal fibers.
• 00:15:00 This video discusses the muscle spindle, stretch reflex, and how it works. The muscle spindle is a muscle receptor that can detect mechanical stimulation and generate a stretch reflex. The stretch reflex activates the sensory fibers of the muscle spindle, which then generate an action potential. This reflex is important because it can be used to control movement.
• 00:20:00 Type 1a reflexes are caused by the stimulation of sensory fibers that pick up the degree of stretch. These impulses travel down the spinal cord to the dorsal root ganglia and synapse on two points, one to the motor neuron and one to a little neuron between the sensory neuron and the motor neuron. This monosynaptic reflex is called a mono-synaptic reflex because it occurs on the same side as the motor neuron.
• 00:25:00 This video explains the function of alpha and gamma motor neurons, which contract when stimulated. It also explains the importance of corticospinal tracts, which contain upper motor neurons that can inhibit or stimulate these neurons.
• 00:30:00 This video discusses the muscle spindle, which is a stretch reflex pathway in the spinal cord. The muscle spindle helps generate potentials very quickly, and if the extrafusal fibers contract and the intrafusal fibers don't contract and stretch, the type 1a fibers become very slack, decreasing action potentials. Alpha, gamma, and alpha gamma co-activation is important to preventing decreased action potentials in the type 1a fibers, as is having the alpha motors contract to shorten the muscle and the gamma motors around the neuron to stimulate the intrafusal fibers to contract.