Human Anatomy and Physiology I Laboratory Histology of Nervous Tissue and The Spinal Cord This lab involves two laboratory exercises: 1) Histology of Nervous Tissue, and 2) Spinal Cord, Spinal Nerves, and the Autonomic Nervous System. Complete the Review Sheet for the entire first exercise, and the portion pertaining to the spinal cord for the second. The remainder of the second exercise will be completed in the next lab on the spinal and peripheral nerves. The quizzes are separate as well: for this lab take the quiz on nervous tissue and the spinal cord. Alternately, your instructor may have you turn in drawings of nerve tissue in lieu of the Review Sheets. Use the Virtual Microscope or other histology sites for images of nerve tissue. Click on the sound icon for the audio file (mp3 format) for each slide. There is also a link to a dowloadable mp4 video which can be played on an ipod. 1
Cells of the Nervous System: Glial Cells (neuroglia) and other supportive cells: These provide supportive functions for the nervous system. And new information stresses the functional interdependence of glial cells and neurons. Neurons: these are the functional cells of the nervous system, i.e. they conduct the impulses. 2
CNS Neuroglia a) Astrocytes - these cells anchor neurons to blood vessels, regulate the micro-environment of neurons, and regulate transport of nutrients and wastes to and from neurons. They are part of the blood-brain barrier. b) Microglia - these cells are phagocytic to defend against pathogens. They may also monitor the condition of neurons. c) Ependymal cells - these cells line the fluid-filled cavities of the brain and spinal cord. They play a role in production, transport, and circulation of the cerebrospinal fluid. d) Oligodendrocyte - produce the myelin sheath in the CNS. 3
Peripheral Neuron Supportive Cells a) Schwann cells - derived from neural crest cells, they produce the myelin sheath in the PNS. b) Satellite cells - also derived from the neural crest, they surround cell bodies of neurons in ganglia. Their role is to maintain the micro-environment and provide insulation for the ganglion cells. 4
Functional Types of Neurons Sensory neurons receive an impulse from a receptor and transmit it to the CNS Motor neurons send an impulse to an effector. Interneurons (a.k.a. association neurons or connecting neurons) they carry impulses from neurons to one another. 5
Structural Types of Neurons: Multipolar Multipolar neurons have many dendrites and one axon. The axon typically branches near its destination. These cells are motor and interneurons (connecting neurons). Myelin sheath CNS Effector Multipolar neuron - has many dendrites and one axon. Multipolar neurons are found as motor and interneurons. 6
Structural Types of Neurons:Unipolar Unipolar neurons have one process, an axon. These are sensory neurons. Receptor CNS Unipolar neurons have one process from the cell body, classified as an axon. It branches to connect to receptors and the spinal cord or brain. Unipolar neurons are found as most of the body s sensory neurons. The dendrites are found at the receptor and the axon leads to the spinal cord or brain. 7
Structural Types of Neurons: Bipolar Bipolar neurons found only in the special senses. Bipolar neuron - has one dendrite and one axon attached to the cell body. Bipolar neurons are rare, found only in ear and eye, where they are part of the integration of incoming stimuli. 8
A Multipolar Neuron nucleus nucleolus cytoplasmic processes Notice the many processes attached to the cells body. This slide is a smear made from the gray matter of the spinal cord where motor and interneurons abound. The numerous other small cells that you see are glial cells. What type of glial cells might they be? 9
Gray Matter Neurons: The Brain The cerebrum contains multipolar cells similar to those in the spinal cord. These are known as pyramidal cells. Multipolar neurons are also found in the gray matter of the brain. These cells are motor neurons leading to the corticospinal tract and are known as pyramidal cells. 10
Spinal Cord - Neuron Relationships ganglion sensory fibers sensory cell bodies dorsal root dorsal sulcus (fissure) white matter receptor effector Interneuron gray matter spinal nerve motor fibers ventral root ventral sulcus motor cell bodies central canal 11
Spinal Cord C.S. White matter Dorsal root ganglion Ventral root Gray matter Dorsal root Meninges: Pia mater Arachnoid Dura mater Surrounding both the spinal cord and the brain are the meninges, a three layered covering of connective tissue. The dura mater is the tough outer layer. Beneath the dura is the arachnoid which is like a spider web in consistency. The arachnoid has abundant space within and beneath its thickened outer portion (the subarachnoid space) which contains cerebrospinal fluid, as does the space beneath the dura mater (subdural space). This cerebrospinal fluid supplies buoyancy for the spinal cord and brain to help provide shock absorption. The pia mater is a very thin layer which adheres tightly to the surface of the brain and spinal cord. It follows all contours and fissures (sulci) of the brain and cord. 12
Spinal Cord Vertebra Relationship Epidural space Dura mater Arachnoid Pia mater Body of vertebra Dorsal root ganglion An epidural injection of anesthetic, in childbirth for example, is placed immediately outside the dura mater. It penetrates slowly into the nearby nerve roots. 13
Spinal Cord w/ Ganglion 14
Dura mater WM GM 15
Spinal Root Dorsal root Ganglion GM WM Ventral root 16
Ganglion Cells 17
Structure of a Nerve Nerves are bundles of axon fibers with connective layers similar to those in a muscle. 18
Peripheral Nerve C.S. Perineurium Fasciculi Epineurium 19
Peripheral Nerve Epineurium Perineurium Fasciculi This is a scanning electron microscope image in which the individual fibers are barely visible, but their surrounding myelin sheaths stand out. 20
Myelinated Fibers in the PNS Axon Myelin sheath Perineurium Endoneurium In cross-section the axon fibers can be seen with their myelin sheaths composed of surrounding Schwann cells. 21
Nerve l.s. Node of Ranvier Nucleus of Schwann Schwann cells Nodes of Ranvier In this longitudinal section the nodes of Ranvier where the Schwann cells meet are evident. The axons are the thin lines running through the middle of each Schwann cell. 22
Medullated Nerve Node of Ranvier Schwann cell This tissue has been stained with osmium tetroxide, which renders the membranes in shades of contrasting gray. This allows you to see the axon fiber as it passes through from one Schwann cell to the next. 23
Lab Protocol for Histology of Nervous Tissue and the Spinal Cord 1) Complete the Review Sheet for the entire first exercise, and the portion pertaining to the spinal cord for the second. 2) Take the quiz for Nervous Tissue and the Spinal Cord 24