VAKALS (Vanir, Anj, Kim, Abi, Lyka, Suni)

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OutlineI. Segmental Innervation of Skin

a. Trunk Dermatomesb. Face Dermatomesc. Limb dermatomes

II. Segmental Innervation of Muscles Biceps brachii tendon reflex Triceps tendon reflex Brachioradialis tendon reflex Abdominal superficial reflexes Patellar tendon reflex (Knee Jerk) Achilles tendon reflex

III. Muscle Tone & Muscle Action Motor unit Muscle tone

o Muscle spindleso Tendon spindles

IV. Summation of Motor UnitsV. Muscle Fatigue

VI. Posture Line of gravity in Standing Position

SEGMENTAL INNERVATION OF SKINDERMATOME- Area of skin supplied by a single spinal nerve (a single segment of spinal cord)

Trunk dermatomes- extend round the body from posterior to anterior median plane- Overlapping of Dermatomes- To produce a region of complete anesthesia at least three

contiguous spinal nerves have to be sectioned- Area of Tactile loss > Area of loss of pain & temperature

o Reason: Degree of overlap of fibers carrying pain & temperature is more extensive than overlap of fibers carrying tactile sensations

Face dermatomes- divisions of trigeminal nerve supply a precise area of skin

- Little or no overlap to the cutaneous area of another divisio

Limb dermatomes- complicated dermatomal innervation due to embryological rotation of the limb buds as they as they grow out from the trunk

SEGMENTAL INNERVATION OF MUSCLES- Muscles are innervated by more than one spinal nerve- To paralyze a muscle completely, it would be necessary to

section several spinal nerves or destroy several segments of the spinal cord

1. Biceps brachii tendon reflex C5-C6 Elbow joint Flexion by tapping the biceps tendon

2. Triceps tendon reflex C6, C7 & C8 Elbow joint Extension by tapping the triceps tendon

3. Brachioradialis tendon reflex C5, C6 & C7 Supination of Radioulnar joints by tapping insertion of

brachioradialis tendon4. Abdominal superficial reflexes

Upper: T6 -7 Middle : T8 -9 Lower : T10 -12 Contraction of underlying abdominal muscles by

stroking the skin5. Patellar tendon reflex (Knee Jerk)

L2, L3 & L4 Knee joint Extension by tapping patellar tendon

6. Achilles tendon reflex S1 & S2

VAKALS (Vanir, Anj, Kim, Abi, Lyka, Suni)

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Plantar Flexion of ankle joint by tapping Achilles tendon- tendo calcaneus

MUSCLE TONE & MUSCLE ACTIONMotor unit- consists of a motor neuron in the anterior gray column of the spinal cord and all the muscle fibers it supplies

Muscle tone- Partial state of contraction in a skeletal muscle during rest- Accomplished by asynchronous discharge of nervous impulses in the

motor neurons in anterior gray horn of spinal cord- Dependent on a monosynaptic reflex arc composed of 2 neurons

(Afferent neuron: arising from neuromuscular and neurotendinous spindles and Efferent neuron: cell body lies in the anterior gray column of spinal cord) Muscle spindles- sensitive sensory endings that detects

lengthening and shortening in a muscle- Response regulated by small Gamma efferent fibers

Tendon spindles- detects tensionNOTE!

Neurotendinous receptor- inhibitory; reduces toneNeuromuscular spindle- excitatory; increases tone

Degree of muscle tone depends on Summation of nerve impulses received:Cutting of Afferent or Efferent Pathways

↓Loss of muscle tone

↓Flaccid

↓Quick atrophy and reduced volume

SUMMATION OF MOTOR UNITSAt beginning of muscular contraction, smaller motor units are recruited firstSmaller motor units are innervated by smaller neurons in spinal cord

and brainstem- Lower threshold of excitability

MUSCLE FATIGUE

It is the progressive loss of strength of a muscle with prolonged strong contraction due to reduction in amounts of ATP within muscle fibers.

POSTUREIt is the position adopted by an individual within his/her environment.Line of gravity in Standing Position:

1. Odontoid process of the axis2. Behind the centers of the hip joints3. In front of Knee joints4. In front of Ankle joints

Since greater part of body weight lies anterior to vertebral column, the deep muscles of the back are important in maintaining normal postural curves of the vertebral column in standing position.

Posture depends on: Integrity of the reflex arc Summation of the nervous impulses received by the motor

anterior gray column cells from neurons of nervous system

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“The desire to take medicine is perhaps the greatest feature which distinguishes man from animals.” ~ William Osler :P

“The hardest thing you can do is smile when you are ill, in pain, or depressed. But this no-cost remedy is a necessary first half-step if you are to start on the road to recovery.” ~Allen Klein

“HAKUNA MATATA!- means NO WORRIES!” ~Lion King

Root Injur

yDermatome Pain Muscles Supplied Movement Weakness

Reflex Involved

C5 Lateral side of the upper part of arm

Deltoid and biceps brachii Shoulder abduction, elbow flexion Biceps

C6 Lateral side of forearm Extensor carpi radialis longus and brevis Wrist extensors BrachioradialisC7 Middle finger Triceps and flexor carpi radialis Extension of elbow and flexion of wrist Triceps

C8 Medial side of forearm Flexor digitorum superficialis and profundus Finger flexion NoneL1 Groin Iliopsoas Hip flexion Cremaster

L2 Anterior part of thigh Iliopsosas, Sartorius, hip adductors Hip flexion, hip adduction Cremaster

L3 Medial side of knee Iliopsosas, Sartorius, quadriceps, hip adductors

Hip flexion, knee extension, hip adduction Patellar

L4 Medial side of calf Tibialis anterior, quadriceps Foot inversion, knee extension PatellarL5 Lateral side of lower leg and

dorsum of footExtensor hallucis longus, extensor digitorum longus

Toe extension, ankle dorsiflexion None

S1 Lateral edge of foot Gastrocnemius, soleus Ankle plantar flexion Ankle jerk

S2 Posterior part of thigh Flexor digitorum longus, flexor hallucis longus Ankle plantar flexion, toe flexion None