02 - Spine (1).ppt animal anatomy neurology

Animal Anatomy

1. Seven Clinically Recognizable
Regions:
HYPOTHALAMUS
MIDBRAIN
PONS
MEDULLA
CEREBRUM
CEREBELLUM
SPINAL CORD
MOTOR UNIT

2. Spinal Cord
The spinal cord contains:
•Gray matter with
neurons
•White matter with
ascending sensory and
descending motor
tracts

3. Spinal Cord
•Lower motor neurons
are located in every
segment of the spinal
cord
•Since spinal reflexes
are an important part
of their evaluation, we
can only thoroughly
evaluate those LMN
that innervate limbs

4. Distribution of Spinal Nerves

6. Ascending Sensory
Descending Motor

8. C6 -T2 L4 -S3
UMN located in brainstem (some in cerebrum)

9. UMN
Clinical signs of Upper Motor Neuron Injury
1.Weak or ineffective voluntary movement
2.More gradual loss of muscle tone or bulk
(from disuse rather than denervation)
3.Loss of sensation if sensory fibers are severely
affected
4.Exaggerated and Abnormal Reflexes

10. Abnormal Reflexes
•Spinal reflexes will be
DIMINISHED OR
ABSENT with injury
to peripheral nerves

11. Abnormal Reflexes
•Upper motor neurons
influence spinal
reflexes.
•Injury to Upper motor
neuron will cause
spinal reflexes to
appear spastic or
exaggerated

12. Abnormal Reflexes
•Crossed extensor
reflex
–Withdraw stimulated
limb
–Involuntarily extend
opposite limb

13. Mass Reflexes

14. Abnormal Reflexes
•Babinski Reflex
Stimulation of the tarsus will elicit a marked
extension of the digits in animal with UMN
injury
•Mass Reflex
New reflexes form as a result of chronic
denervation of LMNs

15. Babinski

16. Important:
Do not confuse reflex movement with
voluntary activity. Reflex movement is
initiated by mechanical stimulation,
voluntary activity is not.

17. We can localize spinal cord
lesions into 4 general regions

18. Lumbosacral (L4-S3)
•Contains lower motor neurons to the pelvic limbs, genitourinary and
perineum
•Clinical signs if injury consist of LMN signs to the pelvic limbs
•Dilated rectum, flaccid bladder and loss of resistance to urine outflow.

20. Spinal cord ends @L5 or L6
Nerves roots extend to
corresponding vertebrae
and form cauda equina

21. Thoracolumbar (T3-L3)
•Contains lower motor neurons paraspinal muscles and sympathetic
first order neurons to viscera
•Contains ascending sensory and descending motor tracts to pelvic
limbs
•Clinical signs of injury consist of UMN clinical signs to the pelvic
limbs

24. Panniculus Response

26. Cervicothoracic (C6-T2)
•Contains lower motor neurons to brachial plexus and lateral thoracic nerve
•Contains first order sympathetic fibers to head and face
•Contains ascending sensory and descending motor tracts to pelvic limbs
•Clinical signs of injury consist of UMN clinical signs to the pelvic limbs,
LMN signs to thoracic limbs, and Horner’s syndrome

28. Lateral Thoracic Nerve

29. C6 -T2
ear
Facial Sympathetic Innervation
(Horner' s Syndrome)

31. Cervical (C1-C6)
•Contains ascending sensory and descending motor tracts to
all four limbs, diaphram and intercostal muscles
•Clinical signs of injury consist of UMN clinical signs to all
four limbs.
•Severe injury may cause respiratory paralysis and death

34. Learning Objectives Lecture 2



What is contained in the gray matter of the spinal cord?

What is contained in the white matter of the spinal cord?

What is an upper motor neuron and what does it do?

What clinical signs do we attribute to loss of injury of upper motor neurons?

What clinical signs would we expect if an animal injured both LMN and UMNs to the
back legs at the same time?

We divide the spinal cord into 4 regions based on the distribution of UMN/LMNs in each
region. Please name both the spinal cord segments as well as vertebral segments where
these are located.

What are mass reflexes and what do they signify?

What are postural reactions? What neuroanatomical structures do they test?