L4 - Proprioception and Spinal Reflexes Flashcards
What does fusiform mean?
Tapered at both ends/spindle shaped
A 1a sensory axon would refer to what?
The afferent axon to the CNS.
What is the difference between intrafusal and extrafusal muscle fibre?
Intrafusal muscle is embedded in muscle spindle, while extrafusal isn’t. Extrafusal is the fibre that does the work in contracting, etc.
What information does the muscle spindle send to the CNS?
Sends information about muscle length and rate of change (of length)
Describe the monosynaptic reflex arc when the tendon below your knee is tapped.
- muscle spindle stretches when tapped, pulling intra-fusal and extrafusal muscle fibre.
- 1a afferent fibre fires, sending a signal into the spinal cord.
- This 1a afferent is connected to alpha motor neurons, which are activated by the 1a afferent signal.
- Muscle contracts to oppose the stretching
How do muscle spindles signal the length and rate of change in length of the muscle?
- Bag fibres
- Chain fibres
What are the two types of bag fibres?
Bag 1 and bag 2
In muscle spindle, what signals information about length and what signals information about rate of change in length?
Bag 1 is called the dynamic bag - sends information about rate of change.
Bag 2 and chain fibres sends static information about absolute length.
In what ways can gamma motor neurons tune muscle sensitivity?
- The sensitivity of the muscle spindles can change by pulling them together
- The type of information sent from the spindles can be influenced by pulling on one type of fibre more than another.
What is spasticity and what is it caused by?
Pathologically increased muscle tone (rigidity) because of excessive stretch reflex. Caused by overactive muscle spindle.
What are the functions of gamma motor neurons?
- alter the length of intrafusal muscle fibres
- can bias spindle towards dynamic or static sensitivity.
- regulates sensitivity during voluntary contraction
- important in the regulation of muscle tone
What do Golgi tendon organs detect?
Tension in a tendon or muscle
Where are Golgi tendon organs located?
Between the muscle spindle and tendon.
How can Golgi tendon organs be activated?
Passive stretch or active muscle contraction
What does GTO stand for?
Golgi tendon organ
1b afferents refer to what?
Signals from the Golgi tendon organ
What action do Golgi tendon organs take and how do they do it?
They control muscle tension by inhibiting alpha motor neurons using inhibitory interneurons.
What is the purpose of the actions of Golgi tendon organs?
They are protective mechanisms - preventing muscles from having sustained levels of high tension, which could be dangerous for the muscle.
What does CPG stand for?
Central pattern generators
What might the CPG be responsible for?
Regulating limb and inter-limb movements, such as the ones required for walking, running, etc.
If you don’t have proprioception - what might happen if you don’t have it?
Won’t be able to co-ordinate limbs properly.
What is the time delay in the monosynaptic reflex arc?
40 milliseconds.
What is an elemental action?
A motor action in which the goal outcome is achieved by executing just one goal-directed action
Typically, what type of actions are elemental actions?
Discrete actions
