Somatic Motor and Reflex Arc Flashcards
What are the 3 main functions of the motor system?
- Maintain posture and provide stable platform for movement
- Control voluntary movement and locomotion
- Control visceral motor function (ANS)
What are the 2 main components of the motor system?
Upper motor neurons and lower motor neurons
Postural reactions with an UMN problem?
delayed to absent
Postural reactions with a LMN problem
delayed to absent
Tendon reflexes with an UMN problem
NL to exaggerated
Tendon reflexes with a LMN problem
decreased to absent
Withdrawl reflexes with UMN problem
Normal
Withdrawl reflexes with LMN problem
decreased to absent
Muscle tone with UMN problem
NL to increased
Muscle tone with LMN problem
decreased to absent
Muscle atrophy with UMN problem
Late (disuse)
Muscle atrophy with LMN problem
Early (denervation)
Bladder with UMN problem
Large, turgid, difficult to express
Bladder with LMN problem
Large, flaccid, easy to express
Where are upper motor neurons located?
CNS
Cell body in motor nucleus of the brainstem or motor cortex of the forebrain
Axons connect to lower motor neurons
Who organizes and directs the activity of lower motor neurons? (inhibit or facilitate)
Upper motor neurons
What happens with loss of inhibitory UMN?
increased muscle tone and spinal reflexes
What happens with loss of facilitative UMN?
paresis or paralysis
Where are LMN located?
Cell body in CNS, axons in PNS via cranial or spinal nerves
How many LMN are between the spinal cord and target organ in the somatic motor system?
One. Cell body in CNS, axon connects with skeletal muscle at the junction
How many LMN are between the spinal cord and target organ in the visceral motor system (ANS)?
Two. Cell body of the pre ganglionic neuron (myelinated) is inside the CNS, and its axon synapses with the body of the postsynaptic neuron in the autonomic ganglion. Axon of the post ganglionic neuron (unmyelinated) connects with smooth/cardiac muscle, glands and adipose.
What are the 5 components of the reflex arc?
Receptor Sensory neuron One or more synapses in the CNS Motor neuron Target organ
What detects stretch of the muscle in the patelar reflex test?
Muscle spindle
What happens after muscle stretch is detected by the muscle spindle?
Alpha motor neurons conduct action potentials to the muscle, causing it to contract, and resist being stretched.
Myotatic reflex/muscle stretch
When a muscle is stretched suddenly, excitation of spindles cause reflex contraction. (reflex opposes sudden changes in muscle length)
What detects tension in a muscle?
Golgi tendon
What happens after golgi tendon detects muscle tension?
inhibitory neuron inhibits alpha motor neuron activity, causing muscle relaxation.
Example of a monosynaptic reflex
patellar. most reliable test of myotatic reflex.
Example of a postsynaptic reflex
Flexor reflex (withdrawal)
