Neuroanatomy Quiz #1 Flashcards
What is the myelin sheath? (relevant cards = 1-2, 1-6, 1-7, 2-4, & 3-14)
The insulated covering that surrounds an axon with multiple spiral layers of myelin. It is discontinuous at the nodes of Ranvier and it increases the speed at which a nerve impulse can travel along an axon. It is formed by Schwann cells in the PNS and oligodendrogial cells in the CNS. Each myelin-generating cell furnishes myelin for only one segment of any given axon.
What is a Schwann cell? (relevant cards = 1-2, & 2-4)
The principal glia of the PNS. There are two types of Schwann cell, myelinating and nonmyelinating. Both types of Schwann cell help keep peripheral nerve fibres (both myelinated and unmyelinated) alive. In myelinated axons, Schwann cells form the myelin sheath. Another way to think of them is as the PNS’s analog to the CNS’s oligodendrocytes. Although, they differ from oligodendrocytes in that each myelinating Schwann cell provides insulation to only one axon. As for nonmyelinated Schwann cells, they are involved in maintenance of axons.
A well-developed Schwann cell is shaped like a rolled-up sheet of paper, with layers of myelin between each coil. The inner layers of the wrapping, which are predominantly membrane material, form the myelin sheath while the outermost layer of nucleated cytoplasm forms the neurolemma.
What is an oligodendrocyte? (relevant cards = 1-2, 1-3, & 1-5)
A type of neuroglia. Its main functions are to provide support and insulation to the axons within the CNS. It does this by creating the myelin sheath. Each oligodendrocyte forms one segment of myelin for several adjacent axons. It is also the last cell type to be generated by the CNS.
More specifically, the myelin formed by oligodendrocytes helps increase impulse speed because saltatory propogation of actional potentials occurs at the nodes of Ranvier in between the myelin sheaths.
What is an autonomic ganglion cell? (relevant card = 1-2)
A cluster of autonomic neuronal cell bodies and their dendrites. In essence, it is a junction between autonomic nerves originating from the CNS and autonomic nerves innervating their target organs in the periphery.
There are two main types: sympathetic ganglia & parasympathetic ganglia
Other useful info:
- In the autonomic nervous system, fibers from the CNS to the ganglia are known as preganglionic fibers, while those from the ganglia to the effector organs are called postganglionic fibers.
What is a myelinated motor axon? (relevant card = 1-2)
It is an axon from the CNS that is myelinated and projects outside of the CNS to directly or indirectly control muscles.
What is a motor end plate (neuromuscular junction)? (relevant cards = 1-2, & 1-5)
A large and complex end formation by which the axon of a motor neuron establishes synaptic contact with a skeletal muscle fiber (cell). Another way to put it is…the flattened end of a motor neuron that transmits neural impulses to a muscle.
What else happens there?
- It is where a neuron activates a muscle to contract
How it works:
- As an action potential reaches the end of a motor neuron, voltage-dependent calcium channels open allowing calcium to enter the neuron. Then, the calcium binds to sensor proteins on synaptic vesicles triggering vesicle fusion with the plasma membrane and subseqeuent neurotrasmitter release from the motor neuron into the synaptic cleft.
What is an astrocyte? (relevant cards = 1-2, 1-3, & 1-4)
A star-shaped glial cell in the brain and spinal cord. Some of the functions performed include biochemical support of endothelial cells that form the blood-brain barrier, provision of nutrients to the nervous tissues, maintenance of extracellular ion balance, and playing a role in the repair and scarring process of the brain and spinal cord following traumatic injuries. It is also the most abundant cell of the human brain.
The neuroanatomy cards said that they…“provide trophic and molecular support for neurons.”
What is a microglial cell? (relevant card = 1-3)
A type of glial cell that is the resident macrophage of the brain and spinal cord, and thus acts as the first and main form of active immune defense in the CNS. Microglial cells constitute 10-15% of the total glial cell population within the brain. They are constantly scavenging the CNS for plaques, damaged neurons and infectious agents.
According to the neuroanatomy cards it…“provides other immunologic and cytokine reactivity.”
What are pia mater cells? (relevant card = 1-3)
Pia mater cells are cells of the pia mater. Pia mater is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. It is a thin fibrous tissue that is impermeable to fluid. This allows the pia mater to enclose cerebrospinal fluid. By containing this fluid the pia mater works with the other meningeal layers to protect and cushion the brain. The pia mater allows blood vessels to pass through and nourish the brain. The perivascular space created between blood vessels and pia mater functions as a lymphatic system for the brain. When the pia mater becomes irritated and inflamed the result is meningitis.
In short, it is…“the thin, translucent, mesh-like meningeal envelope, spanning nearly the entire surface of the brain.”
What is an astrocytic foot process? (relevant cards = 1-3, & 1-4)
Something that surrounds brain capillaries and, during development, induces endothelial cells to form tight junctions. It contributes to the formation of the blood-brain barrier. The astrocytic feet surround the endothelial cells of the blood-brain barrier, providing biochemical support to those cells.
What are the nodes of Ranvier? (relevant cards = 1-5, 1-6, & 1-7)
Periodic gaps in the insulating myelin sheath on the axon of certain neurons that serve to facilitate the rapid conduction of nerve impulses.
What is the ventral root? (relevant cards = 1-30, 1-31, 2-1, & 2-9)
The efferent motor root of a spinal nerve (also called the anterior root). At its distal end, the ventral root joins with the dorsal root to form a mixed spinal nerve.
The ventral root (motor root) of each spinal nerve consists of axons from motor neurons whose cell bodies are found within the gray matter of the spinal cord. A ventral root and a dorsal root unite to form a spinal nerve, which passes outward from the vertebral canal through an intravertebral foramen (bone opening). A posterior branch (posterior ramus) of each spinal nerve turns toward the posterior to innervate muscles and skin of the back. The main portion of the nerve, the anterior branch (anterior ramus), continues forward to supply muscles and skin on the front and sides of the trunk and limbs. The spinal nerves in the thoracic and lumbar regions have a fourth or visceral branch, which is part of the autonomic nervous system.
What is the dorsal root? (relevant cards = 1-30, 1-31, 2-1, & 2-9)
One of the two roots of a spinal nerve that passes dorsally to the spinal cord and consists of sensory fibers. It is the more posterior of the two nerve fibers and it carries sensory information to the CNS.
What is a dorsal root ganglion? (relevant cards = 2-1, & 2-39)
A nodule on a dorsal root of the spine that contains cell bodies of nerve cells (neurons) that carry signals from sensory organs toward the appropriate integration center. A dorsal root ganglion is related to afferent processes.
One is located on the dorsal root of every spinal nerve.
What are sympathetic chain ganglia? (relevant cards = 2-1, & 3-39)
Chains of ganglia of the sympathetic nervous system that deliver information to the body about stress and impending danger, and are responsible for the familiar fight-or-flight response.
They are bilaterally symmetric and located just ventral and lateral to the spinal cord (i.e., on either side of the spinal cord in long chains). Each chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.
