Exam 1 Lecture 2 Pathophysiology of Tone part 1: proprioceptors and reflexes Flashcards
Types of Muscle Spindles (3)
Located in parallel with muscle fibers
- Nuclear Chain Fiber
- Aligned in single row in center of fiber
- Signal static length of muscle
- Signal rate of change of muscle length
- Static Nuclear Bag Fiber
- Aligned in bundle in center of fiber
- Signal static length of muscle
- Signal rate of change of muscle length
- Dynamic Nuclear Bag Fiber
- Aligned in bundle in center of fiber
- Signal rate of change of muscle length
Where are muscle spindles located?
•Located in parallel with muscle fibers
Nuclear Chain Fibers
- Aligned in single row in center of fiber
- Signal static length of muscle (II group sensory fibers)
- Signal rate of change of muscle length (Ia group sensory fibers)
Static nuclear Bag fiber
- Aligned in bundle in center of fiber
- Signal static length of muscle (II group fibers)
- Signal rate of change of muscle length (Ia group fibers)
Dynamic Nuclear Bag Fiber
- Aligned in bundle in center of fiber
- Signal rate of change of muscle length (Ia group fibers)
Group Ia afferents - sensory fibers
- Innervates
- all 3 types (of muscle spindle)
- Provides information about
- length and velocity
•Group II afferents- sensory fibers
- Innervates
- nuclear chain fibers
- static nuclear bag fibers
- Provides information
- about length only
What are muscle spindles?
Muscle spindles are sensory receptors within the belly of a muscle that primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts. The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, by activating motoneurons via the stretch reflex to resist muscle stretch.
http://en.wikipedia.org/wiki/Muscle_spindle
Where are muscle spindles found?
within the belly of a muscle
What do muscle spindles do?
- they primarily detect changes in the length of this muscle.
- They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts.
- the responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, by activating motoneurons via the stretch reflex to resist muscle stretch.
Extrafusal muscle fibers vs intrafusal muscle fibers
Extrafusal muscle fibers are standard skeletal muscle fibers that are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement. (they are just the regular muscle fibers we refer two when talking about skeletal muscles). Shappy: “outside the bags and chains”
http://en.wikipedia.org/wiki/Extrafusal_muscle_fiber
Intrafusal muscle fibers are skeletal muscle fibers that serve as specialized sensory organs (proprioceptors) that detect the amount and rate of change in length of a muscle.[1] They constitute the muscle spindle and are innervated by two axons, one sensory and one motor. Intrafusal muscle fibers are walled off from the rest of the muscle by a collagen sheath. This sheath has a spindle or “fusiform” shape, hence the name “intrafusal”
http://en.wikipedia.org/wiki/Intrafusal_muscle_fiber
Three types of intrafusal muscle fibers (muscle spindles):
- nuclear chain fibers
- static nuclear bag fibers
- dynamic nuclear bag fibers
Intrafusal fibers: contractile and non-contractile parts
Ends are contractilie
- Innervated by gamma motorneurons (sometimes 1-2 beta motorneurons)
- activate to keep tension in the spindle as the extrafusla fibers contract and so that the middle sensory part of the intrafusal fibers can stay taut and detect change in length
Middle is non-contractile
- Innervated by sensory nerve fibers
- provide the sensory component of the interfusal fibers
- Nuclear chain and Static Bag fibers are innervated by Ia & II afferent neurons
- detect rate of change in length of muscle
- detect static length of muscle
- Dynamic Bag fibers are inervated by Ia afferent neurons
- detect rate of change in length of muscle
Motor portion of all muscle spindles (interfusal fibers) are innervated by:
Gamma motor neurons (NOT alpha)
maybe 1-2 beta motor neurons
Muscle spindles innervated by group aI afferent (Sensory) neurons
All of them
- Static Chain Fiber
- Statiic Nuclear Bag Fiber
- Dynamic Nuclear Bag Fiber
- Muscle spindles innervated by group II afferent (sensory) fibers:
Static Chain Fiber
Statiic Nuclear Bag Fiber
What is a type Ia sensory fiber?
A type Ia sensory fiber, or a primary afferent fiber is a type of sensory fiber.[1] It is a component of a muscle fiber’s muscle spindle, which constantly monitors how fast a muscle stretch changes.
(In other words, it monitors the velocity of the stretch).
What does a type II sensory fiber respond to?
provide position sense of a still muscle, fire when muscle is static [2]
Where do you find a type Ib sensory neuron?
In Golgi Tendon Organ
What is a type II sensory fiber?
Type II sensory fiber (group Aβ) is a type of sensory fiber, the second of the two main groups of stretch receptors. They are non-adapting, meaning that even when there is no change in muscle length, they keep responding to stimuli. In the body, Type II fibers are the second most highly myelinated fibers.
Innervate
- nuclear chain fibers
- Static nuclear bag fibers
(but NOT dynamic nuclear bag fibers)
Golgi Tendon Organ
- –Located in series with muscle fibers in musculotendonis junctions
- –Provides information about load and force
- –Innervated by Group Ib fibers- sensory
- Causes Spinal reflex known as AUTOGENIC INHIBITION REFLEX
- First thought of as a protective mechanism
- When too much for Force is applied to muscle, GTO is stretched and activates Group Ib fibers
- causes muscle to relax to avoid tearing
- Now it is thought that GTOs are much more active than previously suspected. Instead of activating only when muscle completely overloads, it is now thought to activate when GTO detects certain parts of the muscle have more tension. The GTO causes that part of the muscle to relax more so that the strain is distributed to other parts of the muscle.
- When too much for Force is applied to muscle, GTO is stretched and activates Group Ib fibers
- First thought of as a protective mechanism
- –http://neuroscience.uth.tmc.edu/s3/chapter02.html
Autonomic Inhibition Reflex
AUTOGENIC INHIBITION REFLEX
- First thought of as a protective mechanism of the GTO
- When too much for Force is applied to muscle, GTO is stretched and activates Group Ib fibers
- causes muscle to relax to avoid tearing
- Now it is thought that GTOs are much more active than previously suspected. Instead of activating only when muscle completely overloads, it is now thought to activate when GTO detects certain parts of the muscle have more tension. The GTO causes that part of the muscle to relax more so that the strain is distributed to other parts of the muscle.
- When too much for Force is applied to muscle, GTO is stretched and activates Group Ib fibers
Gamma Motor Neurons
–Innervate intrafusal fibers
–Mildly contractible
–Controls sensitivity of muscle spindle; keeps spindle taut
–Contracts the ends of the bag and chain fibers and stretches the center of the muscle spindle to adjust the level of tension
Alpha Motor Neurons
- Innervate extrafusal fibers (just regular fibers of the skeletal muscles)
- Highly contractible
- Respond to muscle contraction and force
Muscle spindle: response to muscle stretch
–Afferent endings vigorously increase firing rate to muscle stretch in proportion to rate & amount of stretch
What is a Reflex
•subconscious, programmed unit of behavior in which a certain type of stimulus from a receptor automatically leads to the response of an effector
Reflex Arc
–Neural pathway between the simulation point and a responding organ (muscle or gland)
–Path followed by a nerve impulse to produce a reflex action
Five elements of a basic reflex
- –Sensory receptor
- –Afferent fiber
- –Reflex center
- –Efferent fiber
- –Efferent organ
draw a simple reflex
True or false: reflexes need brain input to operate
false
•Reflexes can operate without brain input
Two types of reflexes that don’t involve the cerebrum
- –Spinal
- •Ex: myotatic reflex, withdrawal reflex
- •Entirely contained within spinal cord
- –Supraspinal (brainstem)
- •Ex: cranial nerve reflexes, postural reflexes
Monosynaptic Reflex
•Monosynaptic Reflex—sensory neuron synapses directly on a motor neuron
Polysynaptic reflex
•Polysynaptic Reflex—one or more interneurons connect the sensory and motor components
- –Longer delay between stimulus and response (than monosynaptic reflex)
- –Length of delay is proportional to the number of synapses involved
- –Can control several muscle groups
Stretch or Myotatic Reflex
- •Simplest type
- •Monosynaptic and ipsilateral muscle stretch reflex
- •Has an afferent and an efferent limb
- –Afferent limb includes muscle spindle and a dorsal root neuron and its afferent fiber
- –Efferent limb includes ventral horn motor neuron that innervates muscle alpha motor neuron
- •Produces contraction of same muscle (agonist) – shortens a lengthened muscle (relaxes the antagonist muscles)
- Same as the deep tendon reflexes we test during a PT exam
Deep Tendon Reflex
(with grades)
Stretch Reflex (myotactic reflex)
- •Muscle tendon is tapped when muscle is in a relaxed but slightly stretched position.
- •Can distract the brain from trying to help or resist by locking fingers together and pulling apart or clenching jaw
- •Reflex responses are graded
- –0 denotes absent reflex response
- –1+ denotes hypoactive reflex response
- –2+ denotes normal reflex response
- –3+ denotes hyperactive without clonus response
- –4+ denotes hyperactive with clonus response
Five most common MSR
(Muscle Stretch Reflex = Deep Tendon Reflex)
Inverse Myotactic Reflex
- •GTO help to prevent excessive tension within a muscle or on the tendon
- •Tension feedback system
- –When the muscle contracts, the GTO stimulation triggers a reflex relaxation of that muscle to prevent tearing of the muscle or tendon (old research)
- –Synergist is inhibited and the antagonist is excited ie. Quad tendon tap produces Hamstring contraction
- –GTO sensitive to lower levels of force than previously believed therefore GTO active in motor control to “spread” the amount of work evenly across the muscle (newer research)
(It is usually protective. Often caused caused by patellafemoral pain or problem in leg give out scenario, wher patent says they are walking and all of a sudden my leg “gives out,”)
Flexor Reflex
- Reflex occurs before conscious awareness
- Serves to protect or escape because the afferents mediate this reflex and convey info regarding painful stimuli
Flexor Reflex with Cross Extensor Reflex
- •Same concept as flexor reflex in it serves to protect you
- •If the stimulus is intense, the contralateral limb extends to maintain posture and prevent fall
What are Primitive Reflexes?
- •Observable in healthy infants within a given time frame but not in adults or neurologically impaired infants
- •Reflexes become integrated into the nervous system as the child ages
- •Each designed with a different purpose
Primitive Reflexes: Grasp Reflex
What
Appears
Integrates
–Placement of the examiner’s finger in the palm of the hand causes grasping of the fingers
–Appears: birth
–Integrates: approx 4-7 months
Primitive Reflexes: Rooting reflex
What it is
Appears
Integrates
- –Gently stroking the cheek towards the lips
- –Baby should open the mouth towards the stimulus and turn the head to latch on to the object
- –Begins: birth
- –Integrates: approx 3 months
Primitive Reflexes: Sucking reflex
What it is
Appears
Integrates
- –Strong, coordinated suck reflex with good stripping action of the tongue
- –Should be resistance to pulling out the pacifier
- –Begins: birth
- –Integrates: approx 3-5 months
Primitive Reflexes: Moro reflex
What it is
Appears
Integrates
- –Hold the baby’s head and shoulders off of the mat with the arms held in flexion on the chest
- –Suddenly lets the head and shoulders drop back a few inches while releasing the arms
- –Arms should fully abduct and extend, then return towards the midline
- –Begins: birth
- –Integrates: approx 3-6 months
Primitive Reflexes: Asymmetrical tonic neck reflex (ATNR)
What it is
Appears
Integrates
- –Head turned to one side, the ipsilateral (same) arm and leg extend while the contralateral (opposite) arm and leg flex (fencing position)
- •Begins: Birth
- Integrates: 4-6 months
Primitive Reflexes: Symmetrical tonic neck reflex (ATNR)
What it is
Appears
Integrates
- –Quadraped
- –Arm and head do the same thing; legs do the opposite
- –Head is extended, arms extend and legs flex
- –Head is flexed, arms flex and legs extend
- –Divides body top to bottom
Begins: 4-6 months
Integrates: 8-12 months
(legs do the opposite thing as head)
When does a baby learn to crawl?
Learns to crawl between 4 and 12 months
STNR
Symmetrical tonic neck reflex
ATNR
Asymmetrical tonic neck reflex
TLR
Tonic labyrinthine reflex
Name the Primitive Reflexes (7)
- Grasp Reflex
- Rooting Reflex
- Sucking Reflex
- Moro Reflex
- ATNR - Asymmetrical tonic neck reflex
- STNR - Symmetrical Tonic neck reflex
- TLR - Tonic Labyrinthine reflex
- prone
- sidelying
- supine
Primitive Reflexes: Tonic labyrinthine reflex (TLR)
What it is
Appears
Integrates
- –Controlled by where head is related to gravity
- –Begins at birth
- –Integrates sometime after 6 months
- Three examples given
- prone
- Sidelying
- Supine
Primitive Reflexes: Tonic labyrinthine reflex (TLR), prone
–Arms and legs exhibit higher flexor tone
Primitive Reflexes: Tonic labyrinthine reflex (TLR), Sidelying
–Weight bearing side exhibits higher extensor tone
–Non-weight bearing side exhibits higher flexor tone
Primitive Reflexes: Tonic labyrinthine reflex (TLR), Supine
–Arms and legs extend
Are Cranial Nerve reflexes considered supraspinal reflexes?
Yes
Name the Cranial Nerve Reflexes (6)
- Pupillary Light
- Accommodation
- Jaw Jerk
- Corneal
- Vestibul-Ocular Reflex
- Gag
Cranial Nerve Reflexes: Corneal
–Closure of eyelids resulting from direct corneal stimulation
Cranial Nerve Reflexes: Vestibulo-ocular reflex
–Patient visually fixate on an object straight ahead, then rapidly turning the patient’s head form side to side and up and down. The eyes should stay fixed on the object and turn in the opposite direction of the head movement.
Cranial Nerve Reflexes: Gag
Gagging or vomiting with irritation of the throat or pharynx
Cranial Nerve Reflexes: Pupillary Light
–Constriction of pupil upon stimulation of the retina by light
Cranial Nerve Reflexes: Accomodation
–Demonstrates changes in lens shape, pupil size and vergence by focusing on a near then far object
Cranial Nerve Reflexes: Jaw Jerk
–Place finger on patient’s chin, with patient’s mouth slightly open, and strike your finger with a reflex hammer. Normally there is no movement.
What are postural reflexes
•any reflex concerned with maintaining posture or ability to assume correct alignment when there has been a departure from it
Are postural reflexes supraspinal reflexes?
yes
what are two types of supraspinal reflexes?
Cranial nerve reflexes
Postural reflexes
Name the Postural Reflexes (6)
- Cross Extensor Component of Flexor Reflex
- Righting Reflexes
- Equilibrium Reflexes
- Protective Reflexes
- Parachute Reflexes (type of protective)
- Propping Reflexes (type of protective)
Is any part of the Cross Extensor Reflex or any part of the flexor reflex part of postural reflexes?
Yes. The cross extensor component of flexor reflex is
Postural Reflexes: Righting Reflexes
- •Orientation of the head in space so eyes and mouth are in a horizontal plane or body parts are restored to proper alignment
- •Tend to be dominant when moving across a fixed or stable surface, such as a sidewalk or balance beam in gymnastics
Postural Reflexes: Equilibrium Reflexes
- •Responses to changes of posture or movement that seek to restore disturbed balance when the body’s base of support is subjected to perturbation (push, pull, or tilt)
- •Tend to be dominant when the supportive surface moves underneath us, such as wind surfing, working on a fishing boat in the open sea, riding a horse, a motorcycle, or a subway train (unstable surface)
- –Use righting responses too but primarily equilibrium dominant
Postural Reflexes: Protective Reflexes
- Can be parachute or propping
- Extension movements of the extremities generally in the same direction as the displacing force
- Parachute
- When the baby is turned face down towards the mat, the arms will extend as if the baby is trying to catch himself
- Propping
- Anterior propping the baby will extend the arms forward to catch himself and prevent falling forward
- Lateral propping occurs when the baby is falling to one side or the other and he extends the arm laterally to catch himself
Postural Reflexes: Parachute Reflexes
- A type of protective reflex
- When the baby is turned face down towards the mat, the arms will extend as if the baby is trying to catch himself
Postural Reflexes: Propping Reflexes
- One of the protective reflexes
- Anterior propping the baby will extend the arms forward to catch himself and prevent falling forward
- Lateral propping occurs when the baby is falling to one side or the other and he extends the arm laterally to catch himself
Name the Spinal Cord Injury Reflexes (3)
- Bulbocavernousus Reflex
- Anocutaneous Reflex (anal wink)
- Internal Anal Sphincter Reflex
Spinal Cord Injury Reflexes: Blubocavernous Reflex
- –Tests for spinal shock after a spinal cord injury
- •absence of the reflex without sacral spinal cord trauma indicates spinal shock
- –involves monitoring anal sphincter contraction in response to squeezing the glans penis or tugging on an indwelling Foley catheter
Spinal Cord Injury Reflexes: Acocutaneous Reflex
“Anal wink”
- –reflexive contraction of the external anal sphincter upon stroking of the skin around the anus (S2-S4)
- –absence of indicates interruption of the reflex arc
- •(sensory afferent or the motor efferent)
Spinal Cord Injury Reflexes: Internal Anal Sphincter Reflex
- –reflexive contraction of the sphincter upon insertion of a gloved finger into the anus
- –Absence of reflex indicates interruption of reflex arc
- –If after spinal shock and with lack of S2-S4 sensation, indicates complete spinal cord injury
What are spinal cord injury reflexes for?
(from my notes)
Helps determine if complete or incomplete spinal cord injury
Bulbocavernosus and Anocutaneous Reflexes are the most common ways MD determines complete or incomplete
Helps with evaluation of rehab potential
Upper vs Lower Motor Neuron
Upper motor neuron (UMN)—
- provides all motor signals from the brain to the spinal cord and from the cerebrum to the brain stem
- Terminate on LMN or exert influence on LMN through local interneurons
- Characterized by spastic paralysis
- Babinski sign (+) is an abnormal UMN reflex
Lower motor neuron (LMN)—innervate postural and girdle muscles
- in the PNS and directly influence muscles
- LMN branch off of the UMN where the PNS and CNS meet
