Muscle Tone & Reflexes

Question 1

Muscle tone definition :

Answer 1

Mild maintained reflex contraction during rest

Question 2

Distribution of muscle tone

Answer 2

Found in all skeletal muscles but more in antigravity muscles

Question 3

Antigravity muscles ?

Answer 3

Muscles that support body weight.

Extensors in LL,Trunk and neck
Flexors in UL and elevators of jaw

Question 4

Mechanism of muscle tone

Answer 4

Stretch reflex

Length of the muscle is shorter than the distance between origin and insertion

Question 5

Stretch reflex definition

Answer 5

Stretch of skeletal muscle leads to feedback contraction of it

Question 6

Pathway of stretch reflex

Answer 6

1- Stimulus
2- Receptor : muscle spindle
3- Afferent : Primary and secondary endings > Posterior root of spinal cord
4- Center : AHC
5- Efferent : Alpha motor neuron to extrafusal muscle fibers
6- Effector organ
7- Response

Question 7

Intrafusal muscle fibers types

Answer 7

Nuclear bag (1-2 in each spindle)
Nuclear chain (3-9 in each spindle)

Question 8

Characters of nuclear bag

Answer 8

Rapidly response
Rapidly adapting
Their nuclei collected in the center

Question 9

Characters of nuclear chain

Answer 9

Spread throughout the central receptor area
Slowly responding
Slowly adapting

Question 10

Which type of fibers of skeletal muscles are not contractile

Answer 10

Intrafusal muscle fibers

Question 11

Types of afferent fibers from muscle spindle

Answer 11

Primary ending

Secondary ending

Question 12

Characters of primary ending afferent fibers

Answer 12

Spiral around nuclear bag and nuclear chain
Group A alpha neurons
Respond first
Responsible for both types of stretch reflex

Question 13

Characters of secondary ending afferent fibers

Answer 13

Originate from nuclear chain
Group A beta neurons
Responsible for static stretch reflex

Question 14

The efferent innervation of muscle spindle

Answer 14

Group A gamma from small AHC that receives impulses from supraspinal centers

Question 15

Ways of stimulation muscle spindles

Answer 15

Stretch of the whole muscle

Increased gamma efferent discharge

Question 16

Types of stretch reflex

Answer 16

Dynamic

Static

Question 17

Dynamic stretch reflex occurs with the ……….. not ………….. stretch

Answer 17

Sudden | maintained

Question 18

Stimulus of dynamic stretch reflex

Answer 18

The start of a long stretch

Sudden not maintained stretch

Question 19

Receptor of dynamic stretch reflex

Answer 19

Nuclear bag

Question 20

Afferent of dynamic stretch reflex

Answer 20

Primary ending only

Question 21

Function of dynamic stretch reflex

Answer 21

Tendon jerks

Question 22

Static reflex occurs as ……. as the stretch is ……………

Answer 22

Long | maintained

Question 23

Stimulus of static stretch reflex

Answer 23

Maintained stretch

Question 24

Receptors of static stretch reflex

Answer 24

Nuclear chain

Question 25

Afferent in static Stretch reflex

Answer 25

Mainly secondary endings and also primary endings

Question 26

Function of static stretch reflex

Answer 26

Muscle tone

Question 27

Functions of gamma efferents

Answer 27

1- Adjusting the muscle tone | 2- Co-activation with A-motor neurons

Question 28

How does gamma efferents adjust muscle tone

Answer 28

Descending stimulatory impulses through it > Contraction in peripheral contractile parts > Stretch of the receptor > Reflex muscle contraction

Question 29

Benefits of Co-activation of gamma motor neurons with A-motor neurons

Answer 29

Potentiate the voluntary movement | Keep the muscle spindle sensitive even during contraction

Question 30

Higher centers that stimulate stretch reflex

Answer 30

``` Area 4 Caudate nucleus Neocerebullum Facilitatory reticular formation Vestibular nucleus ```

Question 31

Higher centers that inhibit stretch reflex

Answer 31

``` Area 6 Lentiform nucleus Paleocerebullum Inhibitory reticular formation Red nucleus ```

Question 32

Clinical importance of stretch reflex

Answer 32

1- Muscle tone 2- Tendon jerks 3- Role in voluntary movement a- potentiation b- damping

Question 33

Tendon jerks definition

Answer 33

Sudden brief contraction in muscle after tapping it's tendon

Question 34

Mechanism of tendon jerks

Answer 34

Dynamic stretch reflex

Question 35

Diagnostic value of tendon jerks

Answer 35

Increased in UMNL Hyperthyroidism Nervousness Deceased or absent in LMNL Hypothyroidism Sleep

Question 36

Plantar reflex center

Answer 36

S1

Question 37

Stimulation of plantar reflex

Answer 37

Firm scratching of the lateral side of the sole from behind forward

Question 38

Normal response of plantar reflex

Answer 38

Flextion of all toes

Question 39

Abnormal response to plantar reflex

Answer 39

Dorsiflexion of big toe and fanning of the others (Babinski's sign)

Question 40

Causes of abnormal plantar reflex

Answer 40

``` Physiological: Deep sleep Deep come General anesthesia Infants below 1 year ``` Pathological : UMNL

Question 41

Abdominal reflex center

Answer 41

T8-T12

Question 42

Abdominal reflex stimulation

Answer 42

Gentle scratching of the skin of the four quadrants of the abdominal using pointed object towards the midline

Question 43

Normal response of abdominal reflex

Answer 43

Contraction of underlying muscles of the abdominal wall

Question 44

Abnormal response of the abdominal reflex

Answer 44

Absent of contraction of underlying

Question 45

Pathological Causes of absence of abdominal reflex

Answer 45

UMNL | LMNL affecting the reflex arc

Question 46

Physiological Causes of absence of abdominal reflex

Answer 46

weakness of the muscles Obesity Multiparous women

Question 47

Golgi tendon reflex definition

Answer 47

Severe contraction > Relaxation

Question 48

Function of Golgi tendon reflexe

Answer 48

Prevents rupture of the tendon

Question 49

Pathway of golgi tendon reflex

Answer 49

Stimulus: Marked muscle contraction (Severe stretch of the tendon) Receptor: Golgi tendon organ (in the tendon) Afferent: A alpha Center: Polysynaptic > Glycine > Hyperpolarization of AHC Efferent: A alpha Response: muscle relaxation

Question 50

Effects of hypersensitivity of muscle spindle on muscle tone | Clasp-knife spasticity

Answer 50

Condition in which during examination of muscle tone the muscle tone will gradually increase then sudden disappear near the end

Question 51

Flexion withdrawal reflex definition

Answer 51

Painful stimulus applied to a limb will lead to flextion of it away from the pain

Question 52

Crossed extensor reflex definition

Answer 52

Painful stimuli applied to a limb leads to flexion and withdrawal of it and extension of the same limb on the other side to support body weight