Lecture25: The Motor Unit, Muscle Tone Flashcards
What is the function of LMN?
The innervation of striated muscles of body and head
What is the function of UMN?
They don’t innervate the muscles directly,
Where do sensory neurons enter the spinal cord?
From the Dorsal Horn
Where do sensory neurons exit the spinal cord?
The ventral horn
What do Dorsal and Ventral roots merge to form?
Spinal nerves
How long is the spinal cord?
46cm
What are both ends of the spinal cord?
The Foramen magnum to the L2 vertebrae
What is the narrow caudal end of the spinal cord called?
Conus medullaris
What are the horse-like things in the sacral region called?
Cauda equina
What is the definition of reflexes?
The simplest motor response to sensory input, the neural pathways involved are called reflex arcs
What is an example of monosynaptic reflexes?
The Withdrawal reflex
What is the definition of the Monosynaptic reflex?
Only one synapse in the reflex arc
What is the definition of the Polysynaptic reflex?
More than 2 synapses involved in the reflex
Are built-in unlearned responses classified as Simple-Basic?
Yes
Give an example of Acquired or conditioned reflexes
Going silent when the lights dim in a cinema
What is the function of crossed extensor reflexes?
The maintenance of balance
What is reciprocal inhibition?
The relaxation of the muscle opposite to the one involved in the reflex, seeing as they work in antagonistic pairs
What is Muscle Tone?
It’s that all muscles are under some degree of stretch to ensure proper posture
What are both reflexes that maintain the muscle tone and posture?
The stretch and myotatic reflexes
What defects cause a change in the muscle tone?
LMN damage or descending pathway damage
What are Motor Pools?
The motor neurons that innervate the same muscle
What are the 2 Types of LMN found in the same pool?
Both alpha and Y(gamma) motor neurones
What muscles do the Alpha motor neurons innervate?
The ones needed for balance and posture (extrafusal muscles)
What muscles do the Y(gamma) motor neurons innervate?
The extrafusal ones
What is a Motor unit?
The smallest functional component of the motor system
What does a motor unit consist of?
A motor neuron and all the muscle fibres it innervates
What is the function of a motor unit?
The precision of muscle control and how fast it’s activated
What are both types of motor units?
Small and large motor units
