1. Lab 10
Anatomy of Spinal Cord and Spinal Nerves, Reflexes, and Reaction Time and Learning
Joseph R. Schiller, Ph.D., James F. Thompson, Ph.D., and Gilbert Pitts, Ph.D.

2. Lab 10 Activities Identify spinal cord structures on microslides
Identify spinal cord structures on models and charts, including the protective coverings
Identify major nerve plexuses on nerve tree model (cervical, brachial, lumbar, + sacral)
Elicit somatic, superficial, and autonomic reflexes in members of your lab group to learn about the various kinds of reflexes (stretch reflex, Babinski, pupillary + ciliospinal)
Biopac Lesson 11 – Reaction Time and Learning: understand a basic difference in reflexes versus learning

3. Structure of the Spinal Cord
Gray Matter: deep “H” shaped region
White Matter: peripheral (myelinated) fiber tracts
Protective coverings: bone, meninges, related tissues
related structures: spinal nerve roots, spinal nerves, dorsal root ganglia

4. Functional Map of Gray Matter
Posterior (dorsal) (gray) horns: sensory axonal endings synapse with interneurons
Anterior (ventral) (gray) horns: somatic motor neuron cell bodies
Lateral (gray) horns: visceral = autonomic motor neuron cell bodies

5. Spinal Cord with Dorsal Root

6. Spinal Cord, c.s., silver stain, 40x
Silver stain produces sharp contrast between white and gray matter
Note the meninges and a dorsal root ganglion are also present

7. Spinal Cord, c.s., Masson, 40x This slide also provides good contrast
Posterior/dorsal horn
Gray commissure
Central canal
Anterior/ventral horn

8. Spinal Cord, c.s., Thoracic, 40x
Gray commissure
Lateral horn

9. Lining of the Central Canal
Ependymal cells
in central canal

10. Sensory Neurons of Dorsal Root

11. Dorsal Root, Sensory Neurons

12. Dorsal Root, Sensory Neurons

13. Dorsal Root, Sensory Neurons with Satellite Cells

14. 31 Pairs of Spinal Nerves All are mixed (m/s) nerves
Thousands of fibers per spinal nerve
Each pair serves a particular region of the body, but overlaps some with the region supplied by the spinal nerve above and below it (redundancy)

15. Spinal Nerve Anatomy Formed from junction of dorsal and ventral roots
Divide into:
dorsal ramus - supplies posterior body trunk
ventral ramus - supplies the rest of body trunk and the limbs

16. Spinal Nerve Branches into Dorsal and Ventral Rami

17. Branches of Ventral Ramus
Rami Comminicantes (autonomic system: supplies viscera)
White ramus communicans (to sympathetic chain)
Gray ramus communicans (from sympathetic chain)
Intercostal nerve (somatic motor and somatosensory supply to muscle and skin)
Cutaneous branches (supply skin)

18. Dermatomes
Areas of skin innervated by the cutaneous branches of each pair of spinal nerves
Each pair also provides some service to the region of the spinal nerve above and the spinal nerve below (redundancy)

19. Reflexes A rapid, predictable, automatic response to a stimulus
Unlearned, unpremeditated, and involuntary
One is aware of somatic reflexes only after they occur
A homeostatic mechanism (feedback path)
Two fundamental types:
Somatic – effector is skeletal muscle
Autonomic (visceral) – effector is smooth muscle, cardiac muscle, or glands
Generally not consciously perceived

20. Components of a Reflex Arc
Receptor - dendrites or other sensory structures respond to changes in the internal or external environment
Sensory neuron - conducts from a receptor to axon terminals
Integrating center (region within the CNS)
Simple - monosynaptic (2 cells only: sensory and motor neurons)
Complex – polysynaptic (> 2 cells: interneurons involved)
Motor neuron - impulses from integrating center to effector
Effector - body part (muscle or gland) which responds to the motor nerve impulse

21. Stretch Reflexes Receptor - muscle spindles
Mechanoreceptors which respond to stretching
Stimulus: stretch, causes increased nerve impulses to the spinal cord
Response: muscle contraction which reduces stretching of the muscle spindle and decreased nerve impulses to spinal cord

22. Stretch Reflexes
Remember, if a muscle is being stretched, its antagonist is contracting
This sensory proprioception information contributes to maintaining proper muscle tone

23. Patellar Reflex Monosynaptic Ipsilateral (same side)
Segmental (at one level of the spinal cord)
Reciprocal component – polysynaptic, inhibition of the antagonist

24. Golgi (Deep) Tendon Reflex
Receptor: Golgi tendon organ
Mechanoreceptor that responds to muscle tension (via the tendon)
Stimulus: increased tension (increased nerve impulses to spinal cord)
Response: muscle relaxes (decreased nerve impulses to spinal cord)
Inhibits the agonist
Reciprocal path: activates the antagonist
Polysynaptic, ipsilateral, and segmental

25. Flexor Reflex
A pull on the limb, extending it, will trigger the reflex
Also a painful stimulus – a burn, pin prick, toe stub, etc.
F-R causes an automatic withdrawal from the (dangerous) stimulus
Polysynaptic, ipsilateral, and segmental

26. Classifying Reflexes Reflexes are classified according to:
Number of synapses in path: mono- versus polysynaptic
Location of receptor versus effector: ipsi- versus contralteral
Level of receptor versus effector: segmental (at same level) versus intersegmental (at different levels)
Patellar (stretch) reflex: monosynaptic, ipsilateral, segmental
Golgi Tendon Reflex: polysynaptic, ipsilateral, segmental

27. Crossed Extensor Reflex
Flexion of a body part is often balanced by extension of the same body part on the opposite side of the body
Polysynaptic
Contralateral
Segmental

28. Reflexes to Observe in Lab
Patellar or Knee Jerk Reflex
Ankle Jerk Reflex
Plantar (Babinski) Reflex – sole of the foot
Abdominal Reflex – if dressed appropriately
Pupillary Reflex
Ciliospinal Reflex

29. Biopac Lesson 11 Reaction Time and Learning
Note: change font size to 9 before printing collected data
Learning requires the ability to connect one event (symbol, stimulus, pattern) with another
Reflexes do not
This lesson involves two different types of events:
Random: cannot be predicted and connected
Regularly repeated: can be learned and anticipated

30. segment 1 segment 2 segment 3 segment 4
 Reformat
Follow the onscreen instructions to collect five segments of data. Reformat the lesson-file name-day/date-time lines into a single line. Print your data journal with font size set to 8). You do not have to print the graph. Use the first four data segments to answer the questions from your lab guide on p

31. Lab 9 Written Homework to Turn in Next Week
Answer the questions and fill out the Table on p
Answer the questions on p
Attach your Biopac Data Journal
Put your name, your instructor’s name, day and time of your lab on all three pages

32. End Lab 10 Presentation