Nervous System - Segmental Innervation of Muscles Flashcards
What is a myotome?
Amount of muscle supplied by one segment of the spinal end.
How are most muscles supplied segmentally?
Equally from two adjacent segments - however, some are predominantly unisegmental (upper limb).
Describe muscles that share a common primary action?
Supplied by the same (normally two) segments, irrespective of their anatomical situation.
Describe muscles that have opposite actions?
They are supplied by the same segments and these usually run in numerical sequence with the former.
What happens for joints distal in limbs?
The spinal centre lies lower in the cord.
What happens with spinal centres?
They tend to occupy continuous segments in the cord - upper one or two segments Innervated one movement, and the lower one or two Innervated the opposite movement.
What is the spinal centre for the elbow?
C5-8:
- C5+6 supply the flexors.
- C7-8 supply the extensors.
What are the main flexors of the elbow?
Brachioradialis.
Brachial is.
What are the main extensors of the elbow?
Triceps.
What is the spinal centre of the hip?
L2-5:
- L2-3 = flexion (legs closer to anterior side of hip).
- L4-5 = extension (legs closer to posterior side of hip).
What muscles flex the hip?
Ilacus.
What is the spinal centre of the knee?
L3-5 and S1:
- L3-4 = extension (legs closer to anterior side of knee).
- L5-S1 = flexion (legs closer to posterior side of knee).
What is the spinal centre of the ankle?
L4-5 and S1-2:
- L4-5 = Dorsiflexion (foot goes up).
- S1-2 = Plantarflexion (foot goes down).
What muscle causes plantarflexion of the ankle?
Soleus.
What segments cause adduction (medial rotation - leg is out and comes in sideways)?
L2-3. Same as flexion.
What segments cause abduction (lateral rotation - leg goes out sideways)?
L4-5. Same as extension.
What is inversion of the foot?
Lateral malleolus goes down towards the ground and first big toe goes up.
What is eversion of the foot?
Lateral malleolus goes up towards the sky/medial goes down, and first big toe goes down.
What segment supplies inversion?
L4. Supplied by tibia is anterior and tibilalis posterior.
What segment supplies eversion?
L5-S1.
What are the segments of the bum?
L4-5 and S1-2.
What is the segment for the superior gluteal nerve?
L4-5 and S1.
What muscles does the superior gluteal nerve supply?
Glutei medius, glutei minimus, tensor fasciae latae.
What is the segment for the inferior gluteal nerve?
L5 and S1-2.
What muscles does the inferior gluteal nerve supply?
Gluteus maximus.
What is the segment for the elbow?
C5-C8.
What segment causes elbow flexion (hands to shoulder)?
C5-C6.
What segment causes elbow extension (hands to body)?
C7-8.
What segment causes abduction and lateral rotation of the shoulder?
C5.
What segment causes adduction and medial rotation of the shoulder?
C6-8.
What segment causes forearm pronation (palm turn to ground)?
C7-8.
What segment causes forearm supination (palm turn upwards from ground)?
C6.
What segment causes wrist flexion (wrist goes down)?
C6-7.
What segment causes wrist extension (wrist goes up)?
C6-7.
What segment causes finger and thumb (long tendons) flexion (fingers in)?
C7-8.
What segment supplies the hand (intrinsic muscles)?
T1.
How is the upper limb segments different to the lower limb segments?
The spinal centres in the upper limb have broken up into separate nuclei to control these precise movements.
Where do the motor spinal centres for the joints of the limb lie?
Cell aggregates in the lateral parts of anterior grey horns in cervical and lumbar enlargements of the cord.
What is the two most important information required with motor innervation?
- Segmental/root supplies.
- Peripheral nerve supplies.
What does C4 supply segmentally?
Diaphragm - controls respiration.
What does C5 supply segmentally?
Deltoid - abduction of the shoulder.
What does C6 supply segmentally?
Biceps - flexion of the elbow. Biceps jerk.
What does C7 supply segmentally?
Triceps - extension of the elbow. Triceps jerk.
What does C8 supply segmentally?
Flexor digitorum profundus and extensor digitorum - finger flexion and extension.
What does T1 supply segmentally?
Abductor policis brevis (small hand muscles) - abduction of the thumb.
What does T7-12 supply segmentally?
Anterior abdominal wall muscles. Abdominal reflex.
What does L1 supply segmentally?
Lowest fibres of internal oblique and trans versus - guarding the inguinal canal.
What does L2 supply segmentally?
Psoas major - flexion of the hip.
What does L3 supply segmentally?
Quadriceps femoris - extension of the knee. Knee jerk.
What does L4 supply segmentally?
Tibialis anterior and posterior - inversion of the foot.
What does L5 supply segmentally?
Extensor hallucinations Lingus and perineal muscles - extension of the great toe and eversion of the foot.
What does S1 supply segmentally?
Gastrocnemius - plantarflexion of the foot (ankle jerk).
What does S2 supply segmentally?
Small muscles of the foot.
What does S3 supply segmentally?
Perineal muscles - bladder (parasympathetic), anal reflex, bulbocarvernosus reflex.
What does root injury entail?
From the side of the spinal cord to the intervertebral foramen, or the roots of the plexuses.
