Histo Lecture 1 Flashcards
two types of cells found in nervous tissue
- nerve cells or neurons
2. neuroglia, glia, or supporting cells
special characteristics of neurons
- extreme longevity
- most are amitotic
- high metabolic rate
neurons are made up of ____ and ____
- neuron cell body (perikaryon)
2. processes: dendrite(s) or axon (nerve fiber)
biosynthetic center of a neuron
neuron cell body (perikaryon)
Rough ER and ribosomes in the perikaryon create ____- darkened areas within the cytoplasm which can be readily seen with a hematoxylin stain
Nissl bodies
the perikaryon is always ____ and has no ____
unmyelinated; action potentials (nerve impulses)
main receptive or main input region of a neuron
dendrite
many organelles in the cell body extend into the dendrites, except ____
the golgi apparatus
conducting region of a neuron; it can generate action potentials (nerve impulses) and transmit them; can be myelinated
axon (nerve fiber)
a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other cell parts (i.e. organelles) to and from a neuron’s cell body, through the cytoplasm of its axon
axonal transport
movement toward the synapse or down the axon toward the axon terminal (i.e. of a neurotransmitter) is _____
anterograde transport
movement toward the cell body
retrograde transport
types of neurons based on structure (number of processes connected to cell body)
- multipolar - 3 or more processes
- bipolar - 2 processes
- unipolar - 1 process
types of neurons based on function (impulse’s direction of travel relative to CNS)
- sensory of afferent (toward CNS)
- motor or efferent (away from CNS)
- interneurons or associations neurons (found betw sensory and motor neurons)
most abundant type of neuron, major neuron type in the CNS
multipolar
rare neuron found in some special sensory organs (olfactory mucosa, eye)
bipolar
found mainly in PNS; common only in DRG of the spinal cord and sensory ganglia of cranial nerves
unipolar neurons
multipolar neurons can be ____ or _____
motor (efferent); interneurons (association) neurons that conduct impulses within the CNS
unipolar neurons are ____ neurons that conduct impulses along ____ pathways to the CNS for interpretation; deal with ____ info from the skin or muscles
sensory; afferent; somatic afferent
transmission of info from neuron to neuron or neuron to effector organ
synapse
classification of synapses based on which neuronal components are involved
- axodendritic - axon terminal and dendrite
- axosomatic- axon terminal and cell body
- axoaxonic synapse- between axons
- dendrodendritic- between dendrites
- dendrosomatic- between dendrite and cell body
neuron carrying impulse/signal toward synapse
presynaptic neuron
neuron carrying impulse/signal away from synapse
postsynaptic neuron (effector cell)
2 types of synapses
electrical and chemical
chemical synapses have a synaptic cleft of ____ nm
20-50
in chemical synapses, depolarization causes ____ to open
voltage-gated Ca channels
chemical synapse: Ca signals for release of nt (stored in synaptic vesicles) via ____ into the _____
exocytosis; synaptic cleft
chemical synapse: NT diffuses across synaptic cleft and binds to NT receptors at _____; each receptor is part of a ____
postsynaptic membrane; ligand-gated channel
chemical synapse: binding of the NT opens associated ligand-gated channels, allowing _____ to flow across ____
ions; post-synaptic membrane
the flow of ions in a chemical synapse produces local changes in membrane potential called the _____, a type of ____ potential (depolarizing or hyperpolarizing)
postsynaptic potential; graded
a typical chemical synapse contains a _____, a ____, and a _____
presynaptic knob (synaptic end bulb or presynaptic axon terminal); synaptic cleft; postsynaptic membrane
examples of neurotransmitters in a chemical synapse
ACh, biogenic amines, amino acids, peptides, ATP, dissolved gases (nitric oxide, carbon monoxide)
3 ways the nt can be removed from the postsynaptic receptor
- degradation by enzymes
- reuptake by astrocytes or presynaptic terminal
- diffusion away from synapse
types of neuroglia
astrocyte, microglial cell, ependymal cell, oligodendrocyte (all in CNS)
schwann cells and satellite cells (in PNS)
produce myelin sheaths in the CNS, providing electrical insulation to axons; the prominent neuroglia in white matter
oligodendrocytes
the largest of the neuroglia; can be found in either white or gray matter- majority in gray matter
astrocytes
astrocytes are connected to one another through ____
gap junctions
astrocytes control the ionic environment around neurons by regulating ____ concentration
potassium
astrocytes have ____ that contribute to the BBB
perivascular feet
neuroglia cell that lines spaces in the brain and spinal cord (ventricles, central canal, etc.)
ependymal cells
ependymal cells have ____ that extend into spaces with CSF; helps the CSF move and flow; help to make up the choroid plexus that produces CSF
cilia
neuroglia that is less numerous than oligodendrocytes and astrocytes; have elongated nuclei
microglia
microglia originate from ____ and enter CNS during development
blood monocytes (bone marrow)
microglia are part of immune system- look like ____ when activated; proliferate and act as ____ cells
macrophages; antigen-presenting
schwann cells also called _____
neurolemmocytes
difference between oligiodendrocytes and schwann cells
one schwann cell produces one myelin sheath or internodal segment and one oligodendrocyte can produce many sheaths
cells found in the PNS surrounding cell bodies in ganglia; have a supportive role, most likely having to do with metabolic exchange or structural support
satellite cells
clusters of neuronal cell bodies in PNS/CNS
PNS: ganglion
CNS: nucleus
bundle of neuronal axons in PNS/CNS
PNS: nerve
CNS: tract
a nerve contains:
- neuron processes (i.e. axons)
- schwann cells
- connective tissue
- blood vessels
- lymphatic vessels
connective tissue coverings associated with nerves:
- endoneurium
- perineurium (forms fascicles)
- epineurium
nerves classified by what direction they are transmitting their impulses
- sensory (afferent)
- motor (efferent)
- mixed- both sensory and motor fibers; most common
nerves can also be classified as:
- cranial- originate/arise at brain- 12 pairs
2. spinal- originate/arise at spinal cord- 31 pairs
schwann cells associated with unmyelinated axons for a ____ role for ____ support
supportive; structural
function of myelin sheaths
- protect and electrically insulate axons from other axons
2. increase speed of nerve impulse transmission
the nucleus, cytoplasm, and last layer of plasma membrane make up the _____ of the schwann cell
neurilemma
rate of impulse propagation depends on:
- axon diameter
2. myelination
the larger tha axon diameter, the ____
faster the action potential
unmyelinated axons produce ____ conduction
continuous
myelinated axons produce ____ conduction
saltatory
