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.

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

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

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

Spinal Cord with Dorsal Root

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

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

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

Lining of the Central Canal Ependymal cells in central canal

Sensory Neurons of Dorsal Root

Dorsal Root, Sensory Neurons

Dorsal Root, Sensory Neurons

Dorsal Root, Sensory Neurons with Satellite Cells

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)

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

Spinal Nerve Branches into Dorsal and Ventral Rami

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)

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)

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

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

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

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

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

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

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

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

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

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

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

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. 10-21.

Lab 9 Written Homework to Turn in Next Week Answer the questions and fill out the Table on p. 10-21 Answer the questions on p. 10-23 Attach your Biopac Data Journal Put your name, your instructor’s name, day and time of your lab on all three pages

End Lab 10 Presentation