Lecture 19: Nervous Tissue (Structure and Function) Flashcards
What are the 2 parts of the nervous system?
Central and peripheral
What are the 2 components of the central nervous system?
Brain and spinal cord
What are the 2 components of the peripheral nervous system?
Cranial nerves, spinal nerves and peripheral nerves
Where are 2 places that grey matter located?
- Peripheral in brain and in areas called nuclei
- Central in spinal cord (H shaped / butterfly shaped)
What are the 5 components of grey matter?
Nerve cell bodies Dendrites Axon terminals Non-myelinated axons Neuroglia
Where are the 2 locations that white matter is located?
Central in brain
Peripheral in spinal cord
What does white matter consist of?
Myelinated material
What are the 3 parts of the axon in the CNS?
Cell body, dendrites and proximal part of the axon
What part of the neuron is part of the PNS?
Distal axon
In the CNS, what produces myelin for the axon?
Oligodendrocyte
In the PNS, what produces the myelin?
Schwann cell
What are the 4 types of neurons?
Motor
Sensory
Integrative
Anaxonic
Where is motor neurons located?
CNS to PNS
Where is sensory neurons located?
PNS towards CNS
Where is integrative neurons located?
CNS
Where are anaxonic neurons located?
Retina (some parts of CNS)
What is the function of motor neurons?
Send signals to effector tissues
What is the function of sensory neurons?
Send environmental signals to integrative centre
What is the function of integrative neurons?
Collate all information
What is the function of anaxonic neurons?
Acts as relays
What are the 8 steps of neurotransmitter synthesis?
- Synthesis of neurotransmitter and formation of vesicles
- Transport neurotransmitter down the axon
- Action potential travels down the axon
- Action potential causes calcium to enter, evoking release of neurotransmitter
- Neurotransmitter attaches to receptor, exciting or inhibiting postsynaptic neuron
- Separation of neurotransmitter molecules from receptors
- Reuptake of neurotransmitter to be recycled
- Vesicles without neurotransmitter transported back to cell body
What are the organizations of peripheral nerves?
Endometrium (loose) surrounds single nerve cells
Perineurium (loose) surrounds a fascicle (clusters of axons)
Epineurium (dense irregular) separates different types of nerves and fills spaces between fascicles
Paraneurium (fascia) separates nerves from surrounding structure
What are the 4 steps of myelination?
- Axon sitting in a groove is surrounded by a Schwann cell
- Mesaxon membrane initiates myelination by surrounding the embedded axon
- Sheet like extension of the mesaxon membrane wraps successively around the axon, forming multiple membrane layers
- Cytoplasm is extruded from between the membranes - becomes compacted to form myelin
What is the relationship between intermodal distance and axon size?
Larger internodal distance = larger axon diameter = fastest saltatory conduction
What is the difference in speed of conduction in myelinated and unmyelinated nerve cells?
Unmyelinated is slower because no node of Ranvier, so cannot jump
What are the 2 places where myelinated axons are found?
CNS and viscera
Where is unmyelinated nerves found?
Periphery
What are 6 types of glia cells found in the body?
- Oligodendrocytes
- Astrocytes
- Microglial cells
- Ependymal cells
- Schwann cells
- Satellite cells
What is the function of oligodendrocytes?
Same as Schwann but in CNS - cytoplasmic processes from oligodendrocytes form flattened cytoplasmic sheaths that wrap around each axon BUT WRAPS AROUND MORE THAN ONE AXON SIMULTANEOUSLY
What are the 3 functions of astrocytes?
- Have perivascular and perineural feet that contain gap junctions to provide biophysical support for endothelial cells
- Transport nutrients from blood to nerve cells
- Regulate nerve impulses by releasing gamma amino butyric acid near nodes of Ranvier
Where are satellite cells found?
Sensory neuron cell bodies, not in CNS
What are the 2 functions of satellite cells?
Same as astrocytes: provide support and transport nutrients
What is the structure of astrocytes?
Star like
What is the structure of microglial cells?
Large cells with elongated nucleus and relatively few processes emanating from cell body
Where are microglial cells found?
Throughout CNS
What are the 4 functions of microglial cells?
- Immune function
- Emote damaged nerve cells
- Sense increased K+ ions
- Digest protein tangles that are associated with dementia and Alzheimer’s
Where are 2 locations that ependymal cells are found?
Line the spinal canal and ventricles of the brain
What kind of cell is ependymal cell?
Cuboidal epithelial but look like columnar
What are the 3cell surface specializations of ependymal cells?
Cilia and microvilli and tight junctions
What is the overall function of ependymal cells?
Synthesize and secrete cerebrospinal fluid in the ventricles
What is the function of cilia on ependymal cells?
Moves cerebrospinal fluid through ventricles to the spinal cord
What are the 2 functions of microvilli on ependymal cells?
Absorb cerebrospinal fluid for removal of pathogens and present them to microglial cells and astrocytes
What is the function of modified tight junctions between ependymal cells?
Control fluid release into brain
How do you monitor molecular and cellular contents of brain?
Spinal tap
What is the cause of multiple sclerosis?
Degenerative, caused by autoimmune degradation of myelin probably bc of Epstein Barr Virus, causing loss of conduction velocity, usually in CNS not peripheral
What are 7 symptoms of multiple sclerosis?
Fatigue
Vision problems (diplopia - double vision)
Slurred speech (dysarthria)
Numbness and tingling sensations (paraesthesia)
Mobility issues (muscle spasms)
Urinary retention
Constipation
What are 2 cells that can be found in PNS？
Schwann cells and satellite cells
What are 4 cells that can be found in CNS?
Oligodendrocytes, astrocytes, microglial cells, ependymal cells
