1. Spinal Cord
Physiology

2. Spinal Cord Physiology
How does information travel in the spinal cord?
White matter tracts conduct nerve impulses to and from the brain
Gray matter receives and integrates incoming and outgoing information to perform spinal reflexes

3. Major Sensory and Motor Tracts
Direct and Indirect Motor Pathways
Light touch / pressure, vibration, proprioception
Posterior column:
Central canal
Gracile fasciculus
Cuneate fasciculus
Lateral corticospinal tract
Posterior spinocerebellar tract
Rubrospinal tract
Anterior spinocerebellar tract
Lateral reticulospinal
tract
Spinal nerve
Vestibulospinal
tract
Spinothalamic tract
Medial
reticulospinal tract
Sensory (ascending) tracts
Motor (descending) tracts
Anterior median fissure
Tectospinal tract
Anterior
corticospinal
tract
Pain, temp, itch, tickle, deep pressure

4. Reflexes and Reflex Arcs
A reflex is a fast, predictable, automatic response to changes in the environment
Reflexes help maintain homeostasis
The spinal cord serves as the integrating center for spinal reflexes
Integration takes place in the gray matter of the spinal cord

5. TYPES OF REFLEXES
Inborn
Learned / Acquired
LOCATION
Cranial
Spinal
FUNCTION
Autonomic (visceral)
Somatic

6. General Components of a Reflex Arc

7. Reflex Arcs: Vocabulary Terms
Ipsilateral
Contralateral
Monosynaptic
Polysynaptic
Reciprocal innervation

8. Stretch Reflex Controls muscle length by causing muscle contraction
Ipsilateral
NMJ
Monosynaptic vs. polysynaptic

9. Tendon Reflex
Controls muscle tension by causing muscle relaxation

10. Flexor (Withdrawal) Reflex
Moves a limb to avoid injury or pain
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

11. Crossed-Extensor Reflex
Maintains balance
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

12. Reflexes
Interactions Animation:
Reflexes

13. Clinical Connection
Reflexes are often used for diagnosing disorders of the nervous system and locating injured tissue
If a reflex is absent or abnormal, the damage may be somewhere along a particular conduction pathway
Read page 467

14. Homeostatic Imbalances
Damage that results from traumatic injuries depends on
Degree of spinal cord section Or
Degree of compression of the segments involved
Read pages C1
Cervical
segment
(A) C7 T1
Thoracic
segment T8
(B) T9
Lumbar
segment
T11
T12
Sacral
segment L2
(C)
(D)