Studied by 31 people
what does rostral mean?
towards the ceiling
what does caudal mean?
towards the floor
what is a nucleus?
a group of neuronal cell bodies in the CNS
what is a ganglion?
a group of cell bodies in the PNS (outside the CNS)
what is a nerve?
a collection of axons in the CNS
tract (affarent/efferent)
what is a fasciculus?
a bundle of nerve fibers (axons)
what makes up white matter in the CNS?
axons
what makes up gray matter in the CNS?
cell bodies
what are the two classes of cells in the CNS and give a synopsis of what they do.
neurons: carry nerve impulses
neuroglial cells: support nerve cells (nutritionally and structurally)
are there more neurons or neuroglial cells?
neuroglial cells
what are neurons?
the structural and functional unit of the nervous system that are highly specialized for the encoding, conduction, and transmission of info
what is the cell body? what does it do? what is the cytoplasm of the cell body called?
the cell body (aka soma) contains the nucleus; it receives info from receptors and integrates the information
cytoplasm: perikaryon
what are dendrites? what do they do?
dendrites are short branches off the cell body that receive signals from other neurons
what is an axon? what does it do? what is the cytoplasm called?
an axon is a long process off the cell body that carries signals away from the cell body and to other neurons
cytoplasm: axoplasm
where is the nucleus located and what does it hold?
located in the center of the cell body and contains chromosomal DNA
what does the cell body contain?
nucleus
cytoplasm (perikaryon): mitochondria, ER, Golgi bodies, ribosomes
nissel granules: consist of rough ER and associated ribosomes
Neurofibrils: composed of a complex network of structural proteins called neurofilaments (plays a role in impulse propagation)
are dendrites uniform in structure?
no
what is the dendritic spine?
where it connects to other neurons
the postsynaptic part of the dendrite
does the axon of a nerve cell have a uniform diameter?
yes
long axons are motor or interneurons?
motor
short axons are sensory or interneurons?
interneurons
what are the terminal branches of an axon called?
telodendria: make contact with other neurons
what is the surface membrane of the axon called?
axolemma
what does the axoplasm contain?
neurofilaments, microtubules, mitochondria, and fragments of the smooth ER
what is the myelin sheath?
a covering on the axon that protects the neuron from damage and speeds up impulse conduction
is myelin sheath continuous?
no, there are gaps in each sheath that are called the nodes of ranvier
longer and/or thicker myelin sheath results in quicker or slower transmission?
quicker
where are the voltage gated sodium channels located at?
the nodes of myelinated axons
what does saltatory conduction mean?
impulses jump from one node to another making the conduction velocity higher
conduction velocity is dependent on what?
myelination
the diameter of the nerve fibers - larger diameter means faster conduction
what are the three types of neurons (functionally)?
afferent (sensory)
efferent (motor)
interneurons
what are afferent neurons and what do they do?
they are neurons that carry information from receptors in the body to the CNS
what are sensory neurons?
afferent neurons when the information reaches a conscious level
what are efferent neurons?
nerve fibers that carry information away from the CNS
what are motor neurons?
efferent neurons when the information reaches the effector organ (ex.muslce)
what are interneurons?
neurons in the CNS that connect one neuron to the other
what are the three types of neurons (structurally)?
unipolar: there is only one process that comes off the cell body, and from there it splits into two (axon and dendrites)
bipolar: there are two processes that come off the cell body (axon one way and dendrite the other)
multipolar: there are multiple processes that come off the cell body (one axon and multiple dendrites)
what type of structural neuron is the most common?
multipolar
where is each type of structural neuron found?
unipolar: only in dorsal root ganglia
bipolar: retina, cochlea of ears, nasal mucosa
multipolar: spinal motor neuron, Purkinje neuron, pyramidal cell
what are pyramidal cells and where are they found?
(multipolar) cells with a long axon found in the cerebral cortex
what are purkinje cells and where are they found?
(multipolar)cells where the dendrites look like a tree found in the cerebellum
in reference to unmyelinated neurons, what type of fibers play a role in slow (chronic) pain?
c fibers
what are glial cells?
an abundant (15 times more glial than neurons) type of supporting cell that provide structural and biochemical support (nutritional and environmental - remove waste)
do glial cells conduct impulses?
no
where are Schwann cells found and what do they do?
schwann cells are in the axon of neurons in the PNS and are responsible for the synthesis of myelin in the PNS
they also help to buffer excess extracellular K+ which prevents rampant depolarization
where are oligodendrites found and what do they do?
oligodendrites are found in the axons of neurons in the CNS and are responsible for the synthesis of myelin in the CNS
they are only found in the brain
unlike schwann cells, they can myelinate a segment of several axons
what are the functions of astrocytes?
blood-brain barrier: prevent circulatory chemicals from entering the brain and spinal cord
nutrition: transport nutrients, ions, and molecules from capillary to neurons (thought to be important communicators between neurons and capillaries)
healing: astrocytes act as scavengers to remove neuronal debris and seal off areas for healing
prevent excess depolarization: buffer excess K+
remove neurotransmitters from synaptic cleft
support: provide structural support and stability
developmental: act as a guide for outgrowth and migration in developing nervous system
what are ependymal cells and what do they do?
found in the ventricles of brain
they are ciliated columnar epithelial cells with tight junctions that line cavities of the neural tube forming a selective barrier between nervous tissue and ventricular fluid
ependymal cells form the?
choroid plexus which produces CSF by filtering components from the blood
what are microglia and what do they do?
they develop from the mesoderm and normally exist in small #s until needed
they become macrophages in response to injury or damage (act as scavengers because they have a phagocytic role in removing debris and damaged cells)
all glial cells (except microglia) develop from what?
ectoderm
give a synopsis of each glial cell.
oligodendrocytes: synthesis of myelin in the CNS
Schwann cells: synthesis of myelin in the PNS
ependymal cells: ciliated cells that form the choroid plexus
astrocytes: BBB, nutrition, healing, support, prevent excess depolarization, remove neurotransmitters, development
microglia: act as macrophages
differentiate gray matter and white matter in the spinal cord compared to the brain.
brain: grey matter (cell bodies) is outside and white matter (axons) is inside
spinal cord: grey matter (cell bodies) is inside and white matter (axons) is outside
what is the synapse? what are the two types and which is most common?
the junction between neurons where impulses are transmitted
electrical and chemical
chemical is most common
what is the electrical synapse?
the cell membrane of one neuron is very close to the other neurons cell membrane (makes a small gap) so the electrical signal easily jumps from one membrane to the other
what is the chemical synapse?
nerve impulses are transmitted via chemical substances from one cell membrane to the next
the presynaptic membrane is where the impulse comes from, the post synaptic membrane is where it goes to, and the synaptic cleft is the junction (gap)
what are the different types of chemical synapses?
axodendritic: axon-dendrite connection (most common)
axoaxonic: axon-axon connection
axosomatic: axon-cell body connection
what are the different types of neurotransmitters? give a small synopsis of each
acetylcholine: CNS and PNS; in the neuromuscular junction
serotonin: only CNS (mainly midbrain - raphe nucleus); sleep wake cycle; when concentration is low = depression
dopamine: only CNS (basal ganglia); important for movement; low dopamine related to Parkinsons
noradrenalin: in sympathetic post ganglionic nerve fibers and hypothalamus
glutamin acid: in the brain
GABA (gamma amino butyric acid): in the spinal cord and cerebellum
are neurons able to multiply?
most cannot because they do not have centromeres but some peripheral nerve fibers are able to regenerate because they contain the growth factor
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