Exam 4: L2 Flashcards
Reflexes and Gait:
Involve motorneurons and local interneurons to produce reflexive and semi-automatic movements
Motor circuits in the _____ and _____ support reflex movements and feedback adjustments
Central pattern generators produce ______
Reflexes and Gait:
Involve motorneurons and local interneurons to produce reflexive and semi-automatic movements
Motor circuits in the brainstem and in the spinal cord support reflex movements and feedback adjustments
Central pattern generators produce semi-automatic movements such as walking, running, chewing
How does muscle sense stimuli?
There are two sensors within our muscles:
- Muscle spindes sense ______ and have ____ feedback on alpha motor neurons to cause ____
- Golgi tendon organs/GTO’s sense ______ and have ____ feedback on alpha-motoneurons
Descending control: ______ modulate muscle spindle contractions
How do muscles sense stimuli:
There are two sensors within our muscles:
Muscle spindles sense length/stretch and have positive feedback on alpha motorneurons to cause them to contract
GTO’s sense force/contraction, have negative feedback on motoneurons
Descending control: gamma-neurons modulate muscle spindle contractions
Reflex circuit components:
1.
2.
3.
4.
5.
Reflex Circuit Components:
- Receptor within the muscle
- Afferent fibers
- Interneuron
- Efferent nerve fiber
- Motor neuron on the effector organ
Muscle Spindle:
- capsule containing intrafusal fibers
- stretch ____ when the whole muscle is contracting
- intrafusal fibers do/do not contribute to the force of contraction
- ______ in number than extrafusal and _____ in orientation w/ extrafusal
- _________ sense stretch and conduct APs through myelinated axons at 70 m/s, wrap around the middle of the fiber
- y-MNs innervate the _______ regions of the fiber, they _____ the fiber
Muscle Spindle:
- capsule containing intrafusal fibers
- stretch passively when the whole muscle is contracting
- intrafusal fibers do NOT contribute to force of contraction
- fewer in number than extrafusal and parallel in orientation w/extrafusal fibers
- Type Ia sensory fibers sense stretch and conduct APs through myelinated axons at 70 m/s and wrap around the middle/equiatorial region of the fiber
- y-MNs innervate the polar regions of the fiber, they contract the fiber (stretching it as a result)
The central region of the intrafusal fibers lack contractile proteins and thus can’t contract. ______ fibers innervate that middle region of intrafusal fibers. The type II fibers innervate the ____. The gamma (y-MNs) fibers are efferent and innervate the ___ of the intrafusal fibers, which contain contractile proteins.
The central region of the intrafusal fibers lack contractile proteins and thus cannot contract.
Type Ia fibers innervate that middle region of intrafusal fibers
Type II fibers innervate the ends of intrafusal fibers
The gamma fibers (y-MNs) are efferents and they innervate the ends of the intrafusal fibers which contain contractile proteins.
The stretch reflex (or “myotatic reflex):
- is the _____ of reflexes
- the only _____ reflex in humans
- operates in many muscles, easily seen in knee-jerk reflex or patellar reflex in a doctor’s office
- stretch sensors: ________ innervate sensors called _____
The stretch reflex or “myotatic reflex”
- is the simpliest of reflexes
- the only monosynaptic reflex in humans
- operates in many muscles, easily seen in the knee-jerk reflex/petallar reflex in a doctor’s office
- stretch sensors: Ia afferent fibers innervate sensors called muscle spindles
Myotatic Reflex Excitability:
1) Stimulate patellar tendon
2) quad muscle stretches
3) via muscle _____, activation of ___ and ___ fibers of the femoral nerve
4) signal travels to spinal cord (which level)?
5) Monosynaptic
6) stimulate alpha motor neuron on quad muscle
7) quad contraction
8) leg kick
9) FAST, less than 50 milliseconds from stimulus to leg kick
Myotatic Reflex Excitability:
- Stimulate patellar tendon
- Quad muscle stretches
- via spindle fibers, activation of Ia and II afferent fibers of femoral nerve
4) signal travels to spinal cord (L4)
5) Monosynaptic
6) stimulate alpha motor neuron on quad muscle
7) quad contraction
8) leg kick
9) FAST, happens in 50ms from stimulus to leg kick
The monosynaptic stretch reflex:
The endings of Ia afferents wrap around intrafusal fibers and are excited by stretch. Ia afferents cross from the peripher into the CNS to contact alpha motoneurons that project into periphery to innervate extrafusal fibers in the ____ or _____ muscle.
The monosynpatic stretch reflex:
The endings of Ia afferents wrap around intrafusal fibers and are excited by stretch. Ia afferents cross from the peripher into the CNS to contact alpha motoneurons that project into periphery to innervate extrafusal fibers in the same or homonymous muscle.
The monosynpatic reflex:
Muscle stretch also results in the ______ of antagonist muscles. This inhibition of antagonist muscles is acomploshed through glycineric ____ neuron
Monosynaptic reflex:
Muscle stretch also results in inhibition of antagonist muscles
The inhibition of antagonist muscles is accomploshed through activation of glycinergic Ia inhibitory interneuron (Ia ii)
Reciprical Inhibition:
Type Ia activation of an alpha motor neuron results in:
- contraction of _________ and ______ muscle
AND
- inhibition of ______ muscle via _____
Reciprical Inhibition:
Type Ia activation of an alpha motor neuron results in:
- contraction of homonymous and synergistic muscles
AND
- inhibition of antagonistic muscles via interneuron called 1a inhibitory interneuron or 1aii
Activation of GTO inhibits contraction:
- ___synaptic
- muscle contraction or force activates GTO, located in a capsule within the tendon
- depends on afferent ____ fibers
- activates glycinergic ____, which inhibits ____ and ____ via their alpha MNs
- _____ of myotatic reflex (opposes function and terminates it)
Activation of GTO inhibits contraction:
- DI-synpatic
- muscle contraction or force activates GTO, located within capsule within tendon
- depends on Ib afferent fibers
- activates glycinergic inhibitory interneurons, which inhibits homonymous and synergistic contraction via their alpha MNs
- Inverse of myotatic reflex
y-MotorNeuron function:
- responsible for ______ to intrafusal muscle
- when only alpha-MNs are activated, yMNs will _____ and then ______
- Normal movements involve what
y-Motor Neuron Function:;
- responsible for feedback to intrafusal muscle
- when only alpha-MNs are activated, y-MNs will slack and then no further signaling can occur
- Normal movements involve co-activation of both alpha MNs and y-MNs
Recurrent Inhibition:
Renshaw cells are small MNs within ventral horn
aMNs release of Ach excites renshaw cells
Renshaw cells in turn release _____
- inhibition returns to motor neurons (recurrent inhibition—feedback loop)
- also inhibits type Ia ii neurons
This feedback loop causes rapid inhibition of contraction
Controlled by UMNs
y-Loop
gamma MNs alone can cause muscle contraction via indirect excitation of a-MNs
- yMN activation contracts ____ regions of intrafusal muscle
- contraction stretches equatorial regions by pulling on the ends
- stretch of that intrafusal fiber in turn activates ____ afferents, which excite ___ innervating homonymous muscle
Some brainstem motor control centers exert yMN excitation. After forebrain damage, brainstem yMN postural activation of extensor muscles take over, creating _____
y-Loop:
yMNs alone can cause muscle contraction via indirect excitation of aMNs
- yMN activation contracts polar regions of intrafusal muscle
- contraction stretcher equatorial regions by pulling on the ends
- stretch of the intrafusal fiber in turn activates Ia afferents, which excite aMNs innervating homonymous muscle
Some brainstem motor control centers exert yMN excitation. After forebrain damage, brainstem yMN postural activation of extensor muscles take over, creating spascitity
Moro Reflex;
MORO reflex is stimulated by sudden movement of _______.
This causes the baby to do what?
What is the moro reflex coordinated by?
Moro reflex:
Moro reflex is stimulated by sudden movement of the head backwards (in a child <6 months old)
The baby will abduct their arms, take a rapid intake of breath in and also flex their legs
Moro reflex is coordinated by fasiculus proprius
Tonic Neck Reflex;
Explain this position:
______ of the head to one side when the infant is lying back
extension of _____ arm and flexion of ____ arm (“fencing positon”)
2-4 mo can spend a lot of time in TNR
Persistance of TNR predicts what?
Tonic Neck Reflex: “fencing position”
Rotation of head to one side when the infant is lying back
Extension of ipsilateral arm and flexion of contralateral arm (“fencing position)
2-4 mo can spend a lot of time in this position
Persistance of TNR predicts poor motor development
Fill in blank:
UMN injury: ______ strength of reflex
LMN injury: _______ strength of reflex
UMN injury: increases strength of reflex
LMN injury: decreases strength of reflex
Clonus Reflex: Abnormal Hyperreflexia:
_______ oscillary response to muscle stretch
clonus occurs when there is a ____ of cortical inhibition of a deep tendon reflex, causing osciallting muscular contractions
occurs when ______ is placed on wrist or ankle
Clonus Reflex: Abnormal hyperreflexia
3-7 Hz oscillary response to muscle stretch
Clonus occurs when there is a LACK of cortical inhibition of a deep tendon reflex, causing the oscillating muscle contractions
Occurs when sustained tension is placed on wrist or ankle
Clasp Knife Reflex:
gradual ______ leads to reflex resistance followed by disappearance of that resistance and muscle ____ at a critical length of that muscle
Brief excitation, followed by a powerful, long lasting inhibition in homonymous and synergistic muscles
Clasp Knife Reflex:
gradual muscle stretch leads to reflex resistance followed by disappearance of that resistance and muscle extension at a critical length of that muscle
Brief excitation, followed by a powerful, long lasting inhibition in homonymous and synergistic muscles
Crossed Extensor Reflex: Nociceptive Withdrawl
You step on a rock with one of your feet
muscle groups on one side are ____ on the other side
function?
Crossed Extensor Reflex: Nociceptive Withdrawl
You step on a rock with one of your feet
involves contralateral activation or inhibition of those muscle groups opposite to the one that stepped on something
function: to allow the body to support its body weight on opposite side of withdrawl reflex
Supports alternate leg muscle activation on the opposite side while running or walking
