Nervous Tissue Flashcards
Divisions of the Nervous System:
How are neurons classified?
Functional components of the neuron: (4)
cell body, axon, dendrites and synaptic junctions
What are Multipolar neurons? (3)
o Have 1 axon and 2 or more dendrites
o Direction of impulse is form dendrite to cell body to axon
o Motor neurons and interneurons account for most of the multipolar neurons in the nervous system
What are bipolar neurons? (3)
o Have 1 axon and 1 dendrite (very rare)
o Associated with receptors for special senses
o Found in the retina, olfactory mucosa and the ganglia of the vestibulocochlear nerve
What are Pseudounipolar neurons? (4)
o Has 1 process that divides into 2 close to the cell body
o After the division- 1 branch extends into the periphery and 1 into the CNS
o Most of these neurons are sensory neurons
o Cell bodies of sensory neurons are in the dorsal root ganglia and cranial nerve sensory ganglia
What are Interneurons? (3)
o Modulatory role
o Most are inhibitory (releasing GABA)
o Some are excitatory (releasing glutamate)
What are Motor neurons (efferent)? (2)
o found in the anterior (ventral) horn of spinal cord
o Multipolar
What are Sensory neurons (afferent)? (3)
o Found in dorsal root of spinal cord
o Pseudounipolar
o Cell bodies clump together with axons on the periphery
What are Cell bodies?
o Contains a large, euchromatic nucleus, a prominent nucleolus and cytoplasm
What are Nissl bodies? (3)
o Rough ER and free ribosomes clumped together in the cell body
o Make membrane proteins and intracellular proteins
o Extend into dendrites but not into axons
What is the axon hillock?
o Region where the axon originates
What is the Neuropil?
o All the neuronal processes and processes of glial cells
What is the Ganglion? (2)
o Collection of cell bodies outside the CNS
o In the dorsal root ganglia, the cell bodies are clumped together so that the processes are invisible until the periphery of the group of cell bodies
Central vs Peripheral Neurogli:
What are Satellite cells? (2)
- Small cuboidal cells forming a layer around neuronal cell bodies of ganglia
- Only the nuclei are visible in H&E staining
What is the function of satellite cells? (2)
o They establish and maintain a microenvironment around the neuronal body
o Provide electrical insulation and a pathway for metabolic exchanges
What are Schwann cells?
In the PNS, Schwann cells produce myelin sheath
What are Astrocytes? (2)
- Largest of the neuroglial cells
- Form a network of cells within the CNS and communicate with neurons
What are the functions of astrocytes? (4)
o Control of signal propagation and synapse formation
o Maintenance of ionic and transmitter metabolism
o Component of the blood-brain barrier
o Involved in brain repair
What are Oligodendrocytes?
- Small cells with rounded, condensed nuclei and unstained cytoplasm
- Responsible for producing and maintaining myelin in the CNS
- Processes of one cell wraps around parts of several axons
What are Microglia? (4)
- Have short irregular processes and rod-shaped nuclei
- Evenly distributed throughout the white and grey matter
- Capable of migrating
- Specialized phagocytes- monocyte derived, antigen-presenting cells of the CNS
What is the function of Microglia? (2)
o Immune effector cell
o Phagocytic
What are Ependymal cells? (2)
- Low columnar or cuboidal cells
- Lines ventricles of brain and central canal of spinal cord
What are the functions of ependymal cells?
o CSF production and secretion
Surface specializations of ependymal cells: (2)
o Cilia- facilitates movement of CSF
o Microvilli- for absorption
What are Peripheral Nerves?
- A bundle of nerve fibers held together by connective tissue
- Nerve fiber- an axon
Connective tissue of peripheral nerves: (3)
- Endoneurium
- Perineurium
- Epineurium
What is the endoneurium?
- Loose connective tissue surrounding each individual
nerve fibre
What is the perineurium?
- Specialized connective tissue surrounding each nerve
fascicle and contributes to the blood-nerve barrier - Has no immune cells
What is the epineurium?
- Dense irregular connective tissue surrounding the
peripheral nerve and fills the spaces between fascicles
What is grey matter?
- Gray matter- neuronal cell bodies and their dendrites
What is the ventral horn?
o Cell bodies of motor neurons that innervate striated muscle
