Reflexes, Spinal Cord, SCI (10) EXAM 3 Material Flashcards
Extrafusal fibers
Ordinary skeletal muscle fibers
Intrafusal fibers
Muscle spindle
Golgi Tendon Organ
lies in the junction of the muscle and tendon
Muscle spindle
lies parallel to muscle
What does the muscle spindle do?
Provides information on length and rate of length change in muscle
(stretching and how fast)
What type of afferents does the muscle spindle contain?
Ia and II afferents
Ia is faster than II
Where does the muscle spindle send information to?
Brain and SC (via DCML tract)
What information does the golgi tendon provide?
Information regarding muscle contraction
What type of afferents does the golgi tendon organ contain?
Ib afferents AND gamma motor neurons
Where does the golgi tendon send information to?
Brain and SC (via DCML tract)
Two types of LMNs:
- Alpha
2. Gamma
How can the alpha motor neurons be stimulated?
Ia afferents: from muscle spindle
Ib afferents: from golgi tendon organ (GTO)
UMNs from the brain and/or brainstem
What is the golgi tendon organ sensitive to?
Contraction of muscle and muscle tension
T or F: There is motor neuron innervation in the golgi tendon organ?
False, no alpha motor neuron innervation
What does stretching the golgi tendon organ cause to happen?
Straightens collagen fibers, squeezing and distorting the Ib axons, triggering an action potential
What afferents are firing when a muscle is stretched?
Ia and II (muscle spindle)
What afferents are firing when a muscle length is shortened?
Ib (golgi tendon organ)
What is the smallest behavioral unit controlled by the NS?
Reflexes
What is involuntary and relatively stereotypical?
Reflexes
What varies in location of stimulus and strength of stimulus?
Reflexes
For a reflex to occur, there must be:
- Sensory receptor
- Afferent (sensory)
- Efferent (motor)
- Connection between afferent and efferent
- Muscles (can’t be damaged)
Can reflexes operate without UMN input?
Yes, BUT signals from UMNs typically influence reflexes.
Myotatic Stretch Reflex: Monosynaptic or Dysynaptic?
Monosynaptic (one synapse between sensory and motor (alpha) neurons
Myotatic Stretch Reflex: Ia directly excites what motor neurons? And to what muscle (antagonist or agonist)?
Alpha motor neurons
Agonist muscle
(Causes contraction)
Myotatic Stretch Reflex: Ia causes inhibition of which muscle (agonist or antagonist)?
Antagonist
Myotatic Stretch Reflex: Ia causes inhibition of the antagonist muscle through what?
Inhibitory interneuron
Inverse Myotatic Reflex is done through what organ?
Golgi Tendon Organ
Inverse Myotatic reflex: Monosynaptic or Disynaptic?
Disynaptic
Inverse Myotatic Reflex: Golgi Tendon Organ is most sensitive to what? Causes what to fire?
Muscle contraction, causing Ib to fire
Inverse Myotatic Reflex: What inhibits the agonist muscle and through what?
Ib inhibits the agonist muscle through an inhibitory interneuron
Inverse Myotatic Reflex: What excites the antagonist muscle and through what?
Ib excites the antagonist muscle through an excitatory interneuron.
Cutaneous Reflexes are:
Polysynaptic, with interneurons in the reflex arc
In cutaneous reflex, there is:
- Flexor withdrawal
2. Crossed extension
What is a cutaneous reflex caused by?
Cutaneous stimulation
A lesion in the spinal region may interfere with the following:
- Segmental function
2. Vertical Tract Function
Spinal Region Injury: Segmental Function
Interfere with function only at the level of the lesion