Brachial%20Plexus - PowerPoint PPT Presentation

Title: Brachial%20Plexus


1
Brachial Plexus

• Formed by ventral rami of C5C8 and T1
• It gives rise to the nerves that innervate the
  upper limb
• Skin, Shoulder Joint, Muscles

2
Roots (ventral rami)
C4
Dorsal scapular
C5
Nerve to subclavius
C6
Suprascapular
Upper
Posterior divisions
C7
Middle
Trunks
C8
Lateral
Lower
Cords
T1
Posterior
Long thoracic
Medial pectoral
Medial
Lateral pectoral
Axillary
Upper subscapular
Musculo- cutaneous
Lower subscapular
Thoracodorsal
Radial
Medial cutaneous nerves of the arm and forearm
Median
Ulnar
(a) Roots (rami C5 T1), trunks, divisions, and
cords
Anterior divisions
Posterior divisions
Trunks
Roots
Figure 13.9 (a)
3
Axillary nerve
Anterior divisions
Posterior divisions
Trunks
Roots
Humerus
Radial nerve
Musculocutaneous nerve
Ulna
Radius
Ulnar nerve
Median nerve
Radial nerve (superficial branch)
Dorsal branch of ulnar nerve
Superficial branch of ulnar nerve
Digital branch of ulnar nerve
Muscular branch
Median nerve
Digital branch
(c) The major nerves of the upper limb
Figure 13.9 (c)
4
Lumbar Plexus

• Arises from L1L4
• Innervates the thigh, abdominal wall, and psoas
  muscle
• Femoral Nerve- Quadriceps
• Obturator Nerve- adductor muscles

5
Ventral rami
Ventral rami
Iliohypogastric
L1
Ilioinguinal
Femoral
Lateral femoral cutaneous
L2
Iliohypogastric
Ilioinguinal
Obturator
L3
Genitofemoral
Anterior femoral cutaneous
Lateral femoral cutaneous
Saphenous
L4
Obturator
L5
Femoral
Lumbosacral trunk
(a) Ventral rami and major branches of the
lumbar plexus
(b) Distribution of the major nerves from
the lumbar plexus to the lower limb
Figure 13.10
6
Sacral Plexus

• Arises from L4S4
• Serves the buttock, lower limb, pelvic
  structures, and perineum
• Sciatic nerve
• Longest and thickest nerve of the body
• Innervates the hamstring muscles, adductor
  magnus, and most muscles in the leg and foot
• Composed of two nerves tibial and common fibular

7
Ventral rami
Ventral rami
L4
Superior gluteal
L5
Lumbosacral trunk
S1
Inferior gluteal
S2
Common fibular
Tibial
S3
Posterior femoral cutaneous
S4
Pudendal
S5
Sciatic
Co1
Ventral rami and major branches of the
sacral plexus
Figure 13.11 (a)
8
Superior gluteal
Inferior gluteal
Pudendal
Sciatic
Posterior femoral cutaneous
Common fibular
Tibial
Sural (cut)
Deep fibular
Superficial fibular
Plantar branches
(b) Distribution of the major nerves from
the sacral plexus to the lower limb
Figure 13.11 (b)
9
Reflexes

• Inborn (intrinsic) reflex a rapid, involuntary,
  predictable motor response to a stimulus
• Learned (acquired) reflexes result from practice
  or repetition,
• Example driving skills

10
Stimulus
Skin
Interneuron
1
Receptor
2
Sensory neuron
3
Integration center
4
Motor neuron
Effector
5
Spinal cord (in cross section)
Figure 13.14
11
Secondary sensory endings (type II fiber)
Efferent (motor) fiber to muscle spindle
? Efferent (motor) fiber to extrafusal muscle
fibers
Primary sensory endings (type Ia fiber)
Extrafusal muscle fiber
Muscle spindle
Intrafusal muscle fibers
Connective tissue capsule
Sensory fiber
Golgi tendon organ
Tendon
Figure 13.15
12
Muscle spindle
Intrafusal muscle fiber
Primary sensory (la) nerve fiber
Extrafusal muscle fiber
Time
Time
(a) Unstretched muscle. Action
potentials (APs) are generated at a
constant rate in the associated
sensory (la) fiber.
(b) Stretched muscle. Stretching
activates the muscle spindle, increasing
the rate of APs.
Figure 13.16a, b
13
The patellar (knee-jerk) reflexa specific
example of a stretch reflex
2
Quadriceps(extensors)
3a
3b
3b
1
Patella
Musclespindle
Spinal cord(L2L4)
Tapping the patellar ligament
excitesmuscle spindles in the quadriceps.
1
Hamstrings(flexors)
Patellarligament
2
Afferent impulses (blue) travel to
thespinal cord, where synapses occur withmotor
neurons and interneurons.
3a
The motor neurons (red) sendactivating
impulses to the quadricepscausing it to
contract, extending theknee.
Excitatory synapseInhibitory synapse

3b
The interneurons (green) makeinhibitory
synapses with ventral horn neurons (purple) that
prevent theantagonist muscles (hamstrings)
fromresisting the contraction of thequadriceps.
Figure 13.17 (2 of 2)
14
Superficial Reflexes

• Plantar reflex
• Stimulus stroking lateral aspect of the sole of
  the foot
• Response downward flexion of the toes
• Tests for function of corticospinal tracts

15
Superficial Reflexes

• Babinskis sign
• Stimulus as above
• Response dorsiflexion of hallux and fanning of
  toes
• Present in infants due to incomplete myelination
• In adults, indicates corticospinal or motor
  cortex damage