Term
Central Nervous System
- Includes brain & spinal cord
Peripheral Nervous System
- Includes all of the nerve tissue
makes up what division of the NS? |
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Definition
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Term
Somatic NS
Autonomic NS
make up what division of the NS? |
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Definition
| Functional Division of the NS |
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Term
• Includes all nerve tissue except that of ANS
• Controls somatosensory perception (touch, heat, etc) & somatomotor voluntary
• Ach is most common neurotransmitter
are all components of ??? |
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Definition
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Term
• Controls involuntary visceral functions (gland secretion, smooth muscle contraction)
• Consists of pre & post ganglionic neurons
• Divided into 2 components
o Sympathetic
Has LONG postganglionic axons & SHORT preganglionic
o Parasympathetic
What has these components? |
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Definition
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Term
- Specialized to receive, integrate, & transmit electrochemical messages
- Unit structure for CNS
- Composed of:
• Soma or parikaryon: the body
• Variable number of dendrites (cytoplasmic processes that collect incoming messages & carry them towards the soma)
• Single Axons: cytoplasmic process that transmits messages to target cell
o Most axons have a myelin sheath formed by supporting cells & interrupted by gaps called nodes of ranvier
o Internodes: myelinated axon segments between gaps |
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Definition
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Term
- There is no connective tissue in brain, therefore need supporting cells
- Structural & nutritional support of neurons
- Electrical insulation & enhancement of impulse conduction velocity
- “Glue” |
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Definition
| Supporting cells called Neuroglia or Glial Cells |
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Term
- Signals are transmitted by the exocytosis of neurotransmitters
- Synaptic vesicles contains NTs causing specific ion channels to open |
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Definition
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Term
- Signals are transmitted by ions flowing through a gap-junction like complex
- Shape & complexity of neurons varies in CNS
- Gap Junction transmits electrical information |
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Definition
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Term
Naming of Synapses
- Named according to structures they connect
- Axodendritic = axon connecting to dendrite
- Axosomatic
- Axoaxonic = axon fusing with another axon
- Dendrodendritic |
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Definition
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Term
• Most abundant, 2 or more dendrites
• Dendrites radiate in many directions |
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Definition
| Multipolar (Purkinje cells) |
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Term
| Single short axon with NO dendrites |
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Definition
| Unipolar (ex. photoreceptor cells) |
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Term
| • Single “T” shaped process (ex. sensory neurons of dorsal root ganglion_ |
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Definition
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Term
| • Single dendrite arising from pole of soma opposite the axon |
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Definition
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Term
• Carry impulses to end organs
• Induce or inhibit muscle contraction & glandular secretion
• Both somatic & ANS have these components |
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Definition
| Motor Neurons (multipolar neurons, purkinje cells) |
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Term
• ??? = a single neuron & all the corresponding muscle fibers it innervates
o Arm & Leg muscles have a LOT of fibers in each unit
o Eye muscles have relatively few fibers per unit
- Allows faster & more accurate processing of signals |
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Definition
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Term
| • Receive impulses generated by stimulation of peripheral sensory cells & organs carry them toward central nervous system |
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Definition
| Sensory Neurons (bipolar neurons, pseudounipolar neurons, unipolar neurons) |
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Term
| • Carry signals between (1) motor neurons (2) sensory neurons (3) motor & sensory neurons |
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Definition
| Interneurons (golgi Type II neurons) |
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Term
o RER & free ribosomes are not found in axon
o Use Nissl stain to find an axon
o Injury to nerve
- Will see chromatolysis & RER simply disappears
o Find a decrease in RER when cell is overly active
o Cytoskeleton of neuron has microtubules, neurofilaments (intermediate), microfilaments
- Microtubules (made of tubulin)
- MAP = microtubule associated protein
• MAP2 = associated with dendrites & soma
• MAP3 = exclusively found in axon |
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Definition
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Term
- Another axon communicates here (location for axon communication)
- Act as synaptic sites |
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Definition
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Term
Microtubules (13 protofilaments) 25-28 nm
- Microtubule-association proteins (MAPs)
-MAP2 in dendrites
-MAP3 in axons
Neurofilaments (intermediate) 10 nm
Microfilaments 3-5 nm |
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Definition
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Term
- Largest glial cells
- 2 types
• Protoplasmic Astrocytes – common in gray matter
• Fibrous Astrocytes – more common in white matter
o Less branched than protoplasmic |
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Definition
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Term
- Most numerous supporting cells of CNS
- Occur in both gray & white matter
- Nuclei size is between astrocytes & microglia
- Form myelin & occur in rows to myelinate entire axons
- Can provide myelin for segments of several axons unlike a Schwann cell (only 1 segment myelinated per Schwann cell) |
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Definition
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Term
- Smallest & rarest of glia
- Occur in both gray & white matter
- Processes shorter than those of astrocytes
- Very dense chromatin of nuclei
- Have phagocytic capabilities
• If there is injury, there will be increase in size |
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Definition
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Term
- Derived from ciliated neuroepithelial cells
- Lining resembles simple columnar
- Have basal cell processes that extend deep into gray matter
- Lines the ventricles
- Supporting Cells of CNS |
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Definition
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Term
| True or False: Astrocytes, oligodendrocytes, microglia, and ependymal are supporting cells of the PNS. |
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Definition
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Term
Supporting Cells of PNS
- Schwann Cells
- 1 schwann cell may envelope segments of several unmyelinated axons or one segment of a single myelinated axon
- Schwann cell squeezes most of the cytoplasm out
- Myelin is the plasma membrane for Scwann cell & consists mainly of phospholipids (stains with osmium)
- Satellite Cells
- Specialized Schwann cells in craniospinal & autonomic ganglia
- Nuclei appear as a “string of pearls” |
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Definition
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Term
Axon Hillock
Intial Segment
Mitochondria
Smooth ER
Synaptic Vesicles
What has these components |
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Definition
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Term
Myelination
o Proteins have to be transported to distal end
o Myelin is concentric layers of cell membrane
o Wrapping of myelin squeezes out the cytoplasm
o Initial Segment = Action potential is generated here
o Myelin sheath on brain has whitesh look, unmyelinated is grey
- White Matter is bundling of axons
- Gray Matter are groups of cell bodies in gray matter (soma & cell bodies)
o Myelin ↑ the rate of conduction
o Saltatory conduction
- Depolarization of myelinated axons occurs ONLY at nodes of ranvier, where insulation is reduced & Na+, K+ channels are concentrated
- Therefore, action potential “jumps” from node to node
- This leads to faster impulse conduction & less change in ion concentration
o Demyelination
- Myelin sheath is missing
- Conduction will eventually stop because there are NO ion channels below the myelin sheath
- Myelin Basic Protein (MBP) – mice lacking this protein “shivered”
• Transfected mice stopped shivering MBP generated myelin |
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Definition
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Term
o Responsible for movement of mitochondria, lipids, synaptic vesicles, proteins and other cell parts to and from a neuron’s cell body through the cytoplasm of its axon.
o Also responsible for moving molecules destined for degradation from the axon to lysosomes to be broken down.
o There are two types |
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Definition
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Term
• Mediated by kinesin
• Carries organelles and substances for making neurotransmitters away from the cell body toward the + (plus) end of microtubules
• Efferent Neurons work this way |
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Definition
| Anterograde Transport (Axoplasmic Transport) |
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Term
• Mediated by dynein
• Sends chemical messages and endocytosis products headed to endolysosomes from the axon back to the cell
• Afferent Neurons work this way |
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Definition
| Retrograde Transport (Axoplasmic Transport) |
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Term
o The synapse or junction of the axon terminal of a motor neuron with the motor end plate
o Responsible for initiation of action potentials across the muscle's surface, ultimately causing the muscle to contract |
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Definition
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Term
- nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves
- Convey somatosensory information into the brain & spinal cord
- Neurons whose cell bodies are found outside CNS |
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Definition
| Dorsal Root Ganglion (Part of Peripheral Nerve) |
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Term
| • Connective tissue investment that surrounds the entire nerve & is thus the thickest layer |
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Definition
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Term
| • A denser connective tissue that contains fibroblasts that appear to form septa as it divides the nerve into bundles termed fasicles |
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Definition
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Term
• A basal lamina like extracellular matrix that surrounds the Schwann cells
• Composed of bundled myelinated axons |
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Definition
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Term
o Responsible for peristalsis
o Digestive tract is also innervated by the Autonomic Nervous System
- Parasympathetic – promotes digestion
- Sympathetic – shuts down digestion |
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Definition
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Term
| True or False: Cells that need high accuracy have small motor unit |
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Definition
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Term
| True or False: Oligodendrocytes can only myelinate one axon, while schwann cells can do more than one. |
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Definition
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