MMB [002] Reflexes Flashcards
Mention the three main components of the motor system (motor levels )
The ‘Higher Motor Level ’ represents :
Association areas in the cortex (Idea)
The ‘Middle Motor Level ’ represents :
Motor cortex, Basal Ganglia and Cerebellum (Program)
The ‘Lower Motor Level ’ represents :
Spinal cord and brain stem nuclei (performance)
The 1st Requirement for voluntary contraction :
1) Intact Upper motor neuron (from higher centers to …(), OR to …())
1) Intact Upper motor neuron (from higher centers to the spinal cord, OR to nuclei of cranial nerves)
The 2nd Requirement for voluntary contraction :
2) Intact lower motor neuron (from …() of spinal cord to the muscle, OR from …() to muscle)
2) Intact lower motor neuron (from anterior horn of spinal cord to the muscle, OR from cranial nerve nuclei to muscle)
The 3rd Requirement for voluntary contraction :
3-intact muscle
The 1st Requirement for reflex contraction ?
1- intact muscle
The main 2 Requirements for reflex contraction :
1- Intact lower motor neuron (from anterior horn of spinal cord to the muscle , OR from cranial nerve nuclei to muscle)
2- Intact pathway of a reflex arc
Illustrate the reflex pathway
sensory receptor > afferent nerve > integrating center > efferent nerve
> effector organ
Illustrate the reflex arc
(1) Stimulus
(2) Receptor
(sensory neurone)
(3) CNS motor neurone
(4) Effector Reflexes
(5) Response
The 2 types of reflexes ?
1) Protective
2) Regulatory
Mention Examples of protective reflexes
Eye blink , gag reflex , limb withdrawal
Mention Examples of Regulatory reflexes
Vestibulo–ocular reflex , muscle stretch reflex
Two types of motor neurons in the anterior horn ?
Alpha & Gamma
Alpha motor neurons supplies …. Skeletal muscle fibers.
Ordinary
α-motor neurons mainly originate from… sements (spinal segments)
Cervical and lumbosacral
In the thoracic segments below T1, the α-motor neurons are associated only with …(anatomical aspect) muscle
axial
Impulses in α-motor neuron are controlled by impulses coming from :
1- Sensory neurons in dorsal root ganglia
2- Interneurons inside the spinal cord gray matter
3- Descending fibers from higher brain centers (e.g. brain stem)
The Motor Unit Includes … motor neuron(s) and the contacting muscle fibres
Single motor neuron
In a small motor units the motor neuron is with …(degree) threshold of stimulation
LOW
In large motor units is the motor neuron with ….(degree) threshold of stimulation
HIGH
The total motor neurons projection to a single muscle is called the ….
The Motor Neuron Pool
Explain Proprioception
-feedback for the motor control system
-Changes in muscle length specifically stretch – detected by the muscle spindle
-Changes in muscle tension detected by the Golgi tendon organ
Changes in muscle length specifically stretch are detected by the ….
muscle spindle
Changes in muscle tension are detected by the ….
Golgi tendon organ
The muscle stretch reflex – a simple monosynaptic reflex driven by input from the ….
muscle spindle
Define Stretch reflex
It is reflex contraction of a muscle in response to its stretch.
Stretch reflex is a ….(-VE/+VE)feedback reflex that returns the muscle back to its normal length when stretched.
—VE
The Receptor of Stretch reflex is …
The Muscle spindle
….(reflex) is the only monosynaptic reflex in the body.
AKA : direct contact between afferent & efferent
Stretch reflex
What’s the Muscle spindle :
-Specialized encapsulated mechanoreceptor that monitors muscle length
The ends of the Muscle spindle’s capsule are attached to the … of the muscle
Tendon
The Muscle spindle Consists of ….. fibers parallel to …. fibers
3-10 intrafusal fibers parallel to ordinary contractile fibers
Mention the two types of Intrafusal fibers :
- nuclear bag fibers
- nuclear chain fibers
number of nuclear bag fibers ?
1-3
number of nuclear chain fibers in muscle spindles ?
3-9 in each spindle.
Intrafusal fibers have …. receptor at stretchable part ,,, and …., non receptor part.
Central receptor at stretchable part ,,, Peripheral contractile, non receptor part.
Compare in terms of :
-response to stretch
- contractility
-afferents/efferents
Case 2
Mrs. Stewart is a thirty-year-old woman presents to the ER with excessive sweating, tachycardia and tremors. She is diagnosed as hyperthyroidism, on examination she has exaggerated reflexes and Hypertonia.
1-Define Muscle tone.
2) 2-define tendon jerk.
1) A state of tension that is maintained continuously-minimally even when relaxed and which increases in resistance to passive stretch.
2) A reflex contraction of the muscle to which a tendon is attached when the tendon is struck sharply soas to exert a sudden pull on the muscles
Nerve root of Biceps reflex
C5
Nerve root of Brachioradial (supinator) reflex
C6
Nerve root of Triceps reflex
C7
At a reflex rated with +++ , the comment should be :
Slight hyperflexia
At a reflex rated with (++++) , the comment should be :
Very brisk, hyperactive
Nerve root of Knee reflex
L2, L3 & L4
Nerve root of Ankle reflex
S1
