Nervous System Histology (Test 1)

Peripheral Nerve: What does it look similar to (in nature)? What do schwann cell nuclei look like?

"slushy river"

Axons: What will it look like when we stain for myelin? What is the difference between unmyelintated axons and myelinated axons?

*This electron micrograph shows a cross section of a myelinated nerve in the peripheral nervous system. The Schwann cell wraps around the axon to envelop it in a myelin sheath that functions as an electrical insulator.*Unmyelinated Axons EM Schwann cells and oligodendrocytes can also associate with axons but not wrap them in myelin sheaths. This EM image shows a Schwann cell associated with several small axons but without myelinating the axons. In unmyelinated nerves, Schwann cells can associate with several axons; whereas in myelinated nerves, Schwann cells associate with only one axon.

Sympathetic Ganglia: What are 4 differences between these and Dorsal Root ganglia (pseudounipolar)

Further apart smaller more pointed not as many satellite cells

Muscle Spindle: Where will these be found? What will it look like? What do they do?

It will be skeletal muscles surrounding an odd ball * sensory receptors within the belly of a muscle that primarily detect changes in the length of this muscle. They convey length information to the central nervous system via sensory neurons. This information can be processed by the brain to determine the position of body parts

Node of Ranvier: What is a node of ranvier?

Na+ -voltage channels!!!

Specialized Receptors: What are 2 corpuscles? Which is more advanced?

These are both in the skin and attached to pressure receptors (finger and penis)

Brain: What are 2 important cells found here? What part of the brain is each found in?

These are the normal neurons...they care just called different names *Pyramidal Cell The characteristic neuron of the gray matter of the cerebral cortex is the pyramidal cell, which is named for its triangular cell body. These cells feature a thick, branching dendrite that extends toward the surface of the cortex. Dendrites also extend from other sites along the cell body. On the opposite side of the cell from the thick dendrite, an axon descends toward the inner white matter of the brain. The axon is difficult to see and may not be apparent in all cells. *Purkinje Cells The characteristic neuron of the cerebellar cortex is the Purkinje cell. These are very large neurons most notable for their treelike branching dendrites. They form a single, central layer in the cerebellar cortex. This layer is sandwiched between the deeper granular layer that contains cells that modulate the activity of Purkinje cells and the more superficial molecular layer, containing additional inhibitory interneurons and many nerve cell processes.

Peripheral Nerve Fascicles: What are the 3 layers of a nerve fascicle? What will they look like longitudinally or cross-sectionally?

This slide allows you to visualize the different layers of connective tissue that comprise a nerve bundle. At the smallest level are the individual myelin sheaths covering the axons. Each of these nerve fibers is then ensheathed in a layer of endoneurium. Several fibers are surrounded and bound together by perineurium, which appears much thicker. Finally, an outer sheath of epineurium surrounds the entire trunk. You will see that muscle has a similar organization during the next laboratory.

Spinal Cord: Where is ventral horn and dorsal horn? Where are the motor neurons? What do they look like? Where is grey matter? white matter?

dime very fat Many important features of the spinal cord are visible in this cross section. The white matter is composed of nerve fibers carrying ascending and descending information and makes up the outer regions of the cord. The gray matter, which contains cell bodies, is located in the center of the cord and is easily identified by its color and butterfly shape. The central canal lies in the center of the cord and contains cerebrospinal fluid. The dorsal root contains afferent sensory fibers that transmit signals from the periphery, through the dorsal root ganglion, to the dorsal horn. The ventral root contains efferent motor axons. The ventral and dorsal roots come together to form a spinal nerve. What classes of neurons have their cell bodies in the dorsal horn and ventral horn? What is the direction of the action potentials for both of these classes? Answer: Dorsal horn - sensory neurons - action potentials travel from PNS to CNS. Ventral horn - motor neurons - action potentials travel from CNS to PNS.

Parasympathetic Ganglia: Where would these be found? What are 2 versions in the gut?

meisners and auberauch (submucosal, myenteric)

Dorsal Root Ganglia: What type of neurons are here? What are they surrounded by? What do those do?

pseudounipolar -support, nutrtion *The dorsal root ganglion contains the cell bodies of sensory neurons that bring information from the periphery to the spinal cord. These neurons are pseudounipolar and contain an axon-like process that bifurcates with one branch extending toward the periphery and the other branch heading toward the grey matter of the spinal cord. Fibers heading toward the periphery leave the ganglion through the spinal nerve, where they run together with motor fibers. Fibers leading to the spinal cord travel through the dorsal root.

Nerve Cell Body: What type of neuron is in the ventral horn? What does it look like? What is Nissl substance?

ribosomes *axon hillock does not have Nissle *The motor neuron in the ventral horn is easily identifiable by its large size, polygonal shape and extension from the cell body. Compare the size of the nucleolus in the motor neuron with the nuclei in the surrounding support cells *Nissl stain is used to label rough endoplasmic reticulum in neurons. The dark blue structures are referred to as Nissl bodies but are the equivalent of the rough endoplasmic reticulum. Note how Nissl bodies are confined to the soma and dendrites; they do not extend into the axon.