Lecture 15 - Nervous Tissue Flashcards
What do irritability and conductability mean with respect to nerve tissue?
Irritability:
-specialized to receive stimuli
Conductibility:
-specialized to transmit impulses
What are the cellular components of nerve tissue and what are their functions?
Neurons:
- conduct impulses
- functional unit of nervous system
Neuroglial cells:
- nonconductive
- support and protect the neurons
What are the features associated with the cell body? (8)
Slide 18
- contains nuclei
- Nissl bodies; RER and ribosomes
- extensive RER
- elaborate Golgi
- abundant mitochondria
- abundant microtubules (neurotubules) and intermediate filaments (neurofilaments)
- lipofuscin granules (increase with age)
- ligand gated channels; local potentials
What are the features associated with the dendrites? (6)
Slide 19
- conduct local potential towards body
- contains Nissl substance
- does not contain Golgi
- may have dendritic spines
- taper distally and may branch
- ligand gated channels
What is the axon hillock?
- site of origin of the axon
- does not contain Nissl substance
- generates action potenial
What are the features associated with the axon? (7)
Slide 20
- voltage gated channels; action potentials
- contains mitochondria and microtubules
- lacks other organelles
- constant diameter
- terminate in branching telodendrites
- synaptic vesicles in telodendrites
- may have a myelin sheath
What are the classifications of neurons according to function and what differentiates them?
(Slide 24)
Sensory (afferent):
-transmit sensory impulses towards CNS
Motor (efferent):
-transmits impulses from CNS to muscle (somatic) or glands (autonomic)
Interneurons:
-transmits impulses within CNS between sensory and motor neurons
What are the classifications of neurons according to the number of processes?
(Slide 25)
Multipolar:
- most common
- single axon, multiple dendrites
Bipolar:
- two processes, one at each end of neuron
- associated with special senses
Pseudounipolar:
- single process from cell body that bifurcates
- found in dorsal root ganglia
What are the classifications of neurons according to the length of the axon?
(Slide 26)
Golgi I:
-long axons which leave grey mater they are a part of
Golgi II:
-short axons which ramify through gray matter
What is the terminology used to describe neuron structures in the CNS and PNS?
(Slide 32)
Nerve:
-bundle of axons in the PNS
Tract:
-bundle of axons in the CNS
Ganglion:
-aggregation of cell bodies and dendrites in PNS
Nucleus:
-aggregation of cell bodies and dendrites in the CNS
What are the different outer layers of a nerve and what are the features of each?
(Slide 33-34)
Epineurium:
- thick fibrous coat around entire nerve
- supplied by blood and lymphatic vessels
- contains fibroblasts and type I collagen
Perineurium:
- dense connective tissue covering bundles of axons (fascicles) within he nerve
- inner layer of fibroblasts joined by tight junctions
- blood nerve barrier
Endometrium:
- thin layer of reticular connective tissue surrounding individual fibers and Schwann cells
- type III collagen
What are the different membrane specialization of nerves?
Slide 34
Receptors
Ion channels:
- ligand-gated channels on dendrites and cell bodies
- potassium channels on axon
- voltage gated sodium channels on axon
- voltage gated calcium channels on axon
What features differentiate presynaptic membranes and postsynaptic membranes?
(Slide 38)
Presynaptic:
- synaptic vesicles
- vesicular docking proteins and synapsin filaments
- dense bodies
- mitochondria
- voltage-gated calcium channels
Postsynaptic:
- receptors
- ligand-gated ion channels
Differentiate anterograde transport and retrograde transport along the axon.
(Slide 42)
Anterograde: -from cell body to distal axon -uses kinesin -slow (1-6 mm/day) —SCa (preassembled mitrotubules and neurofilaments) —SCb (enzymes, actin, and clathrin) -intermediate (50-100 mm/day) —mitochondria and other organelles -fast (400 mm/day) —synaptic vesicles and neurotransmitters
Retrograde:
- from axon to cell body
- uses dynein
- carries endocytosis material and recycled proteins
- 100-300 mm/day
What are glial cells and what are the different types?
Slide 46
- non-neuronal cells
- support neurons in the PNS and CNS
- capable of cell division
Types:
- astrocytes
- oligodendrites
- Schwann cells
- microglial cells
- ependyal cells?
What are the characteristics of astrocytes?
Slide 46
- derived from neural crest
- only in CNS
- many processes that terminate on capillaries or the pia mater
Fibrous astrocytes:
- predominately in white matter
- long processes with few branches
Protoplasmic astrocytes:
- predominately in gray matter
- shorter processes with many short branches
Describe the functions of astrocytes.
Slide 47
- provides structural support
- establishes blood-brain barrier
- development of cerebral cortex
- potassium sink
- secretes neuron trophic factors
- uptake/metabolism of neurotransmitters
- helps form noncollagenous scar tissue following CNS injury
What are the characteristics and functions of oligodendrocytes?
(Slide 50)
- derived from neural crest
- only in CNS
Functions:
- function as satellite cells; closely associated with cell bodies
- surround axons of unmyelinated fibers
- myelinates axons in CNS (several axons)
What are the characteristics and functions of Schwann cells?
Slide 51
-derived from neural crest
Functions:
-Mylinates axons in PNS (portions of single axons)
What are the characteristics and functions of microglial cells?
-derived from macrophage precursors (bone marrow)
Functions:
- phagocytic in PNS
- recruits leukocytes across blood-brain barrier
- modulates initiation and progression of immune responses
What are the characteristics and functions of ependymal cells?
(Slide 54)
- ciliated cuboidal
- derived from neuroepithelium and line ventricular system
Functions:
- transport
- secretes CSF (choroid plexus)
What are the characteristics and functions of satellite cells?
(Slide 54)
- derived from neural crest
- forms crescents around cell bodies in ganglia
Functions:
-insulation
What are internal and external mesaxons?
Slide 57
Internal mesaxon:
-internal termination of the myelin sheath
External mesaxon:
-external termination of the myelin sheath
Differentiate the major dense lines, intraperiod line, and Schmidt-Lanterman clefts.
(Slide 58-59)
Major dense line:
- electron dense line created by cytoplasmic space between innerleaflets
- contains myelin basic protein
Intraperiod line:
- electron dense line created by extracellular space between outer leaflets
- contains major protein zero (PNS) or proteolipid protein (CNS)
Schmidt-Lanterman clefts:
-area of cytoplasm within the major dense lines
Mutation of which proteins are responsible for Charcot-Marie-Tooth diseases and Pelizaeus-Merzbacher disease?
(Slide 58)
Charcot-Marie-Tooth:
-major protein zero
Pelizaeus-Merzbacher:
-proteolipid protein
What structures are found on the presynaptic membrane and what role do they play?
(Slide 66)
Voltage-gated calcium channels
SNAPs:
- bind synaptic vesicle to presynaptic membrane
- soluble NSF
Vesicle docking proteins:
-SNAP receptors
Synapsins:
-filaments of he presynaptic membrane
What are the types of synapses?
Slide 68
Axosomatic:
-axon terminal synapses with neuron cell body
Axoanxonic:
-axon terminal synapses with another axon terminal
Axodendritic:
-axon terminal synapses with dendrite
Axospinous:
-axon terminal synapses with dendritic spine
Excitatory:
-more positive end-plate potential (closer to threshold)
Inhibitory:
-more negative end-plate potential (farther from threshold)
What are the components of the meninges from superficial to deep?
(Slide 71)
-epidural space
-dura mater
-subdural space
-leptomenix
—arachnoid membrane
—arachnoid villi
—pia mater
What are the characteristics of the dura mater?
Slide 72
- thick sheet of tough, fibrous connective tissue
- lines cranial vault and acts as periosteum (cranial cavity)
- connective tube separated from bone by epidural space (vertebral column)
- venous sinuses that receive blood from cerebral drainage and CSF
What are the characteristics of the arachnoid mater?
Slide 73
- composed of delicate connective tissue
- separated from dura mater by single layer of arachnoid barrier cells
- connected to pia mater by delicate strands forming subarachnoid space
- arachnoid villi extend into venous sinuses allowing CSF to drain
What are the characteristics of the pia mater?
Slide 74
- thin, delicate connective tissue associated intimately with brain and spinal cord
- continuous with blood brain barrier
What are the characteristics of the choroid plexus?
Slide 77
- highly infolded layer of simple cuboidal epithelium found in the ventricles
- connected by tight junctions
- apical microvilli and abundant mitochondria
- contains leaky capillaries
- apical membrane transport proteins responsible for CSF producitionn
What are the characteristics of ependyma?
Slide 79
- simple cuboidal epithelium lining ventricles
- linked by zonula adherens
- apical microvilli and cilia
- basal domain in contact with astrocytic processes forming part of blood-brain barrier
Compare sensory and autonomic ganglia.
Slide 82
Sensory (dorsal root):
- capsule of epineurium
- pseudounipolar neurons
- postganglionic axons are myelinated
- satellite cells; similar to Schwann cells and form a single layer around each neuron
Autonomic:
- capsule of epineurium
- multipolar neurons
- postganglionic axons are not myelinated
- similar to sensory