Lab 4

1 Module 4 Lab – Class Part 1: Nervous System Introduction A. Microscope Remember to clean the oculars and slide before you get started. Obtain a slide of neuron smear. Locate a neuron. You should be able to identify the cell body, nucleus, and processes (axon and dendrites). You will not be able to distinguish the axon from dendrites and you will also see numerous nuclei of oligodendrocytes and astrocytes. Sketch or insert a picture of a neuron below.

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4 11. Parietal lobe 12. Occipital lobe 13. Temporal lobe 14. Olfactory bulb 15. Optic chiasm 16. Infundibulum (caudal) 17. Septum pellucidum 18. Cerebellum 19. Hypothalamus 20. Thalamus 21. Pituitary gland 22. Pineal body/gland 23. Midbrain 24. Pons 25. Medulla oblongata 26. Choroid plexus 27. Corpus callosum 28. Choroid plexus 29. Cerebral aqueduct 30. Mamillary bodies B. For each of the following structures, describe ONE possible outcome if there was an injury or dysfunction to this area of the brain: 1. Frontal lobe – Damage to the frontal lobe can lead to a diminished sense of taste and smell. 2. Precentral gyrus – Damage to this region of the brain can lead to difficulty moving at best and paralysis at worst. 3. Postcentral gyrus – Damage to this structure can lead to loss of your kinesthetic sense, also known as not knowing where parts of your body are in relation to other parts. Such as being unable to touch your nose with your eyes closed. (I just REALLY like this little known sense.) 4. Cerebellum – Damage to the cerebellum can lead to difficulties maintaining your gait, you may walk shakily. 5. Medulla oblongata – Damage to this region is the most serious, because it controls many of your somatic muscles. Thus, a major concern is respiratory failure. C. Cranial Nerves – On the brain model, locate each of the cranial nerves. Within your lab group, discuss the functions of each. a. Olfactory nerve b. Optic nerve c. Oculomotor nerve d. Trochlear e. Trigeminal f. Abducens g. Facial h. Vestibulocochlear i. Glossopharyngeal

5 j. Vagus k. Accessory l. Hypoglossal D. Dissecting the Sheep Brain In groups of 2-3, obtain a sheep brain. Remove the brain from the plastic bag. You may throw the bag in the trash. Pick a selection of dissecting tools from the dissection drawer. Obtain a dissection tray. Be certain to wear gloves and goggles, and clear your work area of any food, drinks, or papers. 1. Examine the exterior features of the sheep’s brain and relate these to the features visible on the plastic model of the brain. You should be able to identify most of the structures from the list above. 2. With ventral side down, separate the cerebral hemispheres with a vertical cut down through the longitudinal fissure. This is an interesting area but be careful not to tear the tissue layers. 3. Continue your cut completely through the brain along its midline until it is separated into two halves. Examine each profile and visualize how they were originally joined together. 4. This saggital section profile can be compared directly to the saggital profile presented by ½ of the plastic brain model. Be careful to pick out the Cerebral cortex (in hemisphere), Corpus callosum , Cerebellum (if still attached), Medulla oblongata , Pons , and Optic chiasma . 5. Note how the Cerebellum relates to the Pons and “ midbrain ” area. 6. With difficulty you may be able to pick out some of the 12 pairs of Cranial nerves on the ventral side of your brain halves. The figures in the textbook are much easier to interpret, but it is interesting to note what the real thing looks like. 7. Take one of the brain halves and cut from the medial to lateral direction through the plane containing the “stalk” of the hypothalamus above the pituitary gland (the “infundibulum”). (The pituitary gland is usually no longer attached on the brains we purchase.) Note the juxtaposition of “gray matter” and “white matter” layers throughout the functional sections. The open cavities are termed “ventricles”. 8. If time permits, it is interesting to make similar medial-to-lateral vertical cuts through other regions such as the Cerebellum , the Pons , and the Midbrain . 9. Label the following structures on your specimen using the provided pins and include a photo of your labeled specimen below: 1) Cerebral cortex 2) Cerebellum 3) Hypothalamus 4) Thalamus 5) Pituitary gland 6) Optic chiasm 7) Pineal body/gland 8) Pons 9) Medulla oblongata 10) Corpus callosum

7 10. When you are finished, please dispose of all organic waste in the marked sack. Do not place gloves or plastic bags in this sack. 11. Carefully wash all scissors, scalpels, pins, probes, and similar tools. Rinse each item and towel-dry it before placing it in the dissection drawer. Please wash the dissection tray with soap and a sponge . Rinse tray with water and towel-dry before you leave the lab. 12. Make sure your table is cleaned and disinfected before you leave the lab . Part 3: The Spinal Cord & Spinal Nerves A. Spinal Cord Model – On the spinal cord model locate the following. Within your lab group, discuss the function of each of the structures and describe at least one : 1. Gray matter 2. White matter 3. Anterior root 4. Posterior root 5. Spinal nerve 6. Central canal 7. Anterior horn 8. Lateral horn 9. Posterior horn 10. Gray commissure B. The Neurological Exam Instructions: Use the handout and video provided to illicit the following reflexes. For each reflex, list each of the structural components included in the pathway (i.e., receptor location/type, spinal nerve, effector). 1. Knee Jerk Reflex. The hammer hits your patellar tendon, where it is noted by the stretch receptor in the biceps femoris. That is sent to a sensory neuron, with the cell body located in the dorsal root ganglia. From there, it goes to interneurons in the spinal cord. Finally, it is sent to the motor neurons in the quadriceps femoris. 2. Biceps Brachii reflex The hammer hits your biceps tendon, where it is noted by the muscle spindle in the biceps brachii. That is sent to a sensory neuron, with the cell body located in the dorsal root ganglia. From there, it goes to interneurons in the spinal cord. Finally, it is sent to the motor neurons in the triceps. 3. Babinski (Plantar) Reflex For this, you hit the bottom of the foot. The signal travels up the sciatic nerve and eventually ends up in the brain, then is sent to the effectors, which is most of the muscles in the lower leg. C. Peripheral Nerves – Using the spinal nerves model, locate each of the nerve plexuses. With your lab group, discuss the branches of each of the nerve plexuses and the structures they innervate.

8 1. Cervical plexus 2. Brachial plexus 3. Lumbar plexus 4. Sacral Plexus Part 4: Neurotransmitters Instructions: 1. Read the following scientific article: https://www.ncbi.nlm.nih.gov/books/NBK539894/ 2. Choose ONE of the neurotransmitters described in the article and, in the space provided, describe the following: a. The primary action(s) of the neurotransmitter you chose. b. At least TWO conditions or symptoms caused by alterations in the neurotransmitter. Be sure to explain the mechanism of action involved in each condition/symptom.