Nervous Tissue Flashcards
What is a satellite cell?
- a Glial cell of the PNS
- found on only Ganglia
- surround cell bodies
What do satellite cells do?
provide metabolic support to neurons
What are Glial cells?
Cells that support nerve cells
How do Schwann cells provide myelination?
- concentric layers of Schwann cell plasma membrane
- (lipid rich) myelin sheath of an axon provided by many Schwann cells
How do Schwann cells surround unmyelinated neurons?
- one or more axons invaginated into a Schwann cell
- ensheathment continued along the neuron by multiple Schwann cells
How does myelination increase speed of conductance?
- segments of myelination separated by nodes of Ranvier
- action potential jumps from node to node (saltatory conduction)
Outline the structure of a neuron
- dendrites; branched structures that carry the impulse towards the cell body
- soma; contains organelles and nucleus
- axon; long fibre that carries the impulse away from the soma
Outline synaptic transmission…
- action potential causes vesicles containing NT to fuse with pre-synaptic membrane
- NT enters synaptic cleft by exocytosis
- NT binds to receptors on post synaptic membrane
What are Ependymal cells?
- Glial cells of the CNS
- found lining ventricles (brain) and central canal (spinal cord)
What do Ependymal cells do?
Produce, secrete, absorb and propel CSF
What are microglia?
phagocytotic glia that are active in regions of injury and inflammation (CNS)
What are Oligodendrocytes?
Glia that myelinate segments of multiple axons in the CNS
What are Astrocytes?
- physical and metabolic support for CNS
- regulates microenvironment
- forms blood-brain barrier
What is a multipolar neuron?
- a neuron with with a single axon and multiple dendrites
- can receive large amounts of information
What is a bipolar neuron?
a nerve cell that has one axon and one dendrite, with the cell body between the two
What are pseudo-unipolar neurons?
- a neuron with one development from the cell body that develops into 2 axons
- NO dendrites
What type of neurons are pseudo-unipolar?
sensory
What do spinal nerves contain?
- myelinated and unmyelinated neurons
- sensory and motor nerves
- connective tissues and coverings
- blood vessels and lymphatics
How are peripheral neurons arranged?
- Axon
- Myelin sheath
- Endoneurium
- Peripheral Nerve Fibre
- Fascicle
- Perineurium
- Epineurium
- Nerve and Blood Vessels
What are Ganglia?
collections of neuronal cells outside of the CNS
Describe the cell bodies of neurons in ganglia…
- large and spherical
- surrounded by satellite cells
- pale nuclei
What are the 2 types of sensory nerve endings?
- free nerve endings (no myelin sheath)
- encapsulated nerve endings
Give 3 examples of encapsulate nerve endings…
- Pacinian Corpuscles; detect pressure and vibration
- Meissner’s Corpuscles; detect discriminatory touch
- Muscle Spindle; detect stretch in skeletal muscle
Describe the ending of a motor nerve…
- axon terminal divides, each part terminating on a different skeletal muscle fibre.
- ## myelin sheath lost, Schwann cell remains
What impacts how many skeletal muscle fibres1 motor neuron innervates?
depends on the precision of movement needed
What does the endoneurium become continuous with at motor nerve endings?
the endomysium
What is a motor unit?
1 motor neurone and all the muscle fibres it innervates
What does white matter comprise of?
- ascending/descending tracts of myelinated neurons
- glia
What does grey matter comprise of?
- cell bodies
- unmyelinated neurons
- glia
How is white and grey matter arranged in the brain?
central region: white matter
outer layer: grey matter
deep aggregations of grey matter (nuclei)
How is white and grey matter arranged in the spinal cord?
central region: grey matter
Outer layer: white matter
