1. Spinal Cord
& Nerves
Ch 13

2. The Spinal Cord

3. Peripheral Nervous System
cranial nerves- 12 pr
spinal nerves- 31 pr

4. The Spinal Cord white matter grey matter dorsal root pia mater
ventral root
pia mater
spinal nerves
arachnoid
dura mater

5. The Spinal Cord
vertebra
spinal cord
spinal nerve

6. Nerve Pathways into the Spinal Cord
sensory pathway
motor pathway

7. Neuron-To-Neuron Transmission
synapses
Interaction Between Neurons

8. Spinal Nerves

9. Spinal Cord

10. Spinal Nerves

11. Spinal Nerves

12. Cervical Plexus Formed by ventral rami of C1–C4
Innervates skin and muscles of the neck, ear, back of head, and shoulders
Phrenic nerve
Major motor and sensory nerve of the diaphragm (receives fibers from C3–C5)

13. Cervical Plexus

14. Brachial Plexus
Formed by ventral rami of C5–C8 and T1 (and often C4 and T2)
It gives rise to the nerves that innervate the upper limb
Major branches of this plexus:
Roots—five ventral rami (C5–T1)
Trunks—upper, middle, and lower
Divisions—anterior and posterior
Cords—lateral, medial, and posterior

15. Brachial Plexus Roots (ventral rami): C4 Dorsal scapular C5 Nerve to
subclavius C6
Suprascapular
Upper
Posterior
divisions C7
Middle
Trunks
Lateral C8
Lower
Cords
Posterior T1
Long thoracic
Medial
Medial pectoral
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)

16. Brachial Plexus: Nerves
Axillary—innervates the deltoid, teres minor, and skin and joint capsule of the shoulder
Musculocutaneous—innervates the biceps brachii and brachialis and skin of lateral forearm
Median—innervates the skin, most flexors and pronators in the forearm, and some intrinsic muscles of the hand
Ulnar—supplies the flexor carpi ulnaris, part of the flexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand
Radial—innervates essentially all extensor muscles, supinators, and posterior skin of limb

17. Musculocutaneous nerve Ulna Radius Ulnar nerve Median nerve
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)

18. Thoracic Nerves
T3-T12
11 intercostal nerve
1 subcostal nerve

19. Lumbar Plexus Arises from L1–L4
Innervates the thigh, abdominal wall, and psoas muscle
Femoral nerve—innervates quadriceps and skin of anterior thigh and medial surface of leg
Obturator nerve—passes through obturator foramen to innervate adductor muscles

20. Lumbar Plexus

21. Sacral Plexus Arises from L4–S4
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

22. Sacral Plexus

23. Functional Divisions of the Peripheral Nervous System
Afferent Division
Sensory (advances) neuron – goes toward CNS
Efferent Division
Motor (exits) neuron- leaves CNS
Somatic Nervous System
Autonomic Nervous System
A Typical Motor Neuron

24. Spinal Reflex Arc sensory neuron motor neuron stretch receptor
interneuron
stretch receptor
motor neuron
patellar ligament
Spinal Reflex Arc

25. Quadriceps (extensors) Hamstrings (flexors)1
Quadriceps strongly
contracts. Golgi tendon
organs are activated.
Interneurons
Quadriceps
(extensors)
Spinal cord
Golgi
tendon
organ
Hamstrings
(flexors) +
Excitatory synapse –
Inhibitory synapse
Figure 13.18, step 1

26. Quadriceps (extensors) Hamstrings (flexors)1
Quadriceps strongly
contracts. Golgi tendon
organs are activated. 2
Afferent fibers synapse
with interneurons in the
spinal cord.
Interneurons
Quadriceps
(extensors)
Spinal cord
Golgi
tendon
organ
Hamstrings
(flexors) +
Excitatory synapse –
Inhibitory synapse
Figure 13.18, step 2

27. Quadriceps (extensors) Hamstrings (flexors)1
Quadriceps strongly
contracts. Golgi tendon
organs are activated. 2
Afferent fibers synapse
with interneurons in the
spinal cord.
Interneurons
Quadriceps
(extensors)
Spinal cord
Golgi
tendon
organ
Hamstrings
(flexors) 3a
Efferent impulses
to muscle with
stretched tendon are
damped. Muscle
relaxes, reducing
tension. +
Excitatory synapse –
Inhibitory synapse
Figure 13.18, step 3a

28. Quadriceps (extensors) Hamstrings (flexors)1
Quadriceps strongly
contracts. Golgi tendon
organs are activated. 2
Afferent fibers synapse
with interneurons in the
spinal cord.
Interneurons
Quadriceps
(extensors)
Spinal cord
Golgi
tendon
organ
Hamstrings
(flexors) 3a
Efferent impulses
to muscle with
stretched tendon are
damped. Muscle
relaxes, reducing
tension. 3b
Efferent
impulses to
antagonist
muscle cause
it to contract. +
Excitatory synapse –
Inhibitory synapse
Figure 13.18, step 3b

29. Effector- part of body that responds to a motor nerve impulse
Reflex Arc
Sensory receptor
Sensory neuron
Integration center
Motor neuron
Effector- part of body that responds to a motor nerve impulse

30. Damage of the spinal cord above C3 can result in_____?
INQUIRY
What is a reflex?
Damage of the spinal cord above C3 can result in_____?
In which portion of the spinal cord do the interneurons lie?
What kind of peripheral nerve fiber carries motor impulses outward to smooth muscles and glands of internal organs?