ANS 123: Tissues II 4/2/2021
© YeunShin Lee 2021 1
Neuron types
Categorized based on relationship among soma, dendrites, and
axon (presented in order of abundance)
• Multipolar: Multiple dendrites that extend from soma in
opposite direction of the axon
o Most common
• Pseudo‐unipolar: Soma with an axon that has split into 2
branches; each branch goes in different direction
o “Pseudo” because embryologically they began as unipolar*
• Bipolar: Large single dendrite that extends from soma in
opposite direction of the axon
o Rare
o Temporarily seen during development
• Unipolar: Soma at one end of single axon
o Messages travel in single direction
o Uncommon in vertebrates
* According to text © 2003. According to Gold & Catania (2008), they begin as biploar
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Queensland Brain Institute
Dentrite
Soma
Glial cells
• Constitute ~ ½ total mass of nervous
tissue
• Provide insulation and structure
o Do not participate in electrical signaling
• Six types
1. Oligodendrocytes
2. Astrocytes
3. Microglia
4. Ependymal cells
5. Schwann cells
6. Satellite cells
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Getty Images
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ANS 123: Tissues II 4/2/2021
© YeunShin Lee 2021 2
Location & Function of glial cells
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Function
Produce lipid‐
rich myelin
sheaths that
wrap around
some axons
giving them
white
appearance;
single cell
produces
multiple
sheaths
Control levels
of neuro‐
transmitters
and important
ions around
synapses
Immune cells of
nervous tissue;
behave as
macrophages
Produce
cerebral‐spinal
fluid
Produce lipid‐
rich myelin
sheaths around
some axons;
single cell
produces single
sheath
[NOTE: Text
considers these to
be specialized
oligodendrocytes)
Control levels
of neuro‐
transmitters
and important
ions around
synapses
Location Central Nervous System Throughout body
Nervous tissue organization
Nervous system: Collection of nervous tissue that interact
1. Central nervous system (CNS) – Consists of the brain and spinal
cord
o Integrates and coordinates all bodily functions
2. Peripheral nervous system (PNS) – Consists of bundles of nervous
tissue that emanate from the central nervous system and
enervate the body
o Sensory component: Detects stimuli (both internal & external) and
delivers that information to the CNS
o Motor component: Carries response messages from the CNS to
appropriate tissues throughout body
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PNS bundles
Held together by layers of
connective tissue
• Epineurium: Wraps around
bundles of fascicles, blood
vessels, and adipose tissue to
form a nerve
• Perineurium: Wraps around
bundles of endoneurium
wrapped axons, blood vessels,
and adipose tissue (e.g., fat) to
form a fascicle
• Endoneurium: Wraps around a
single neuron’s axon, its
associated glial cells and
capillaries
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Courtesy of OpenStax
Epithelial Tissue
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Epithelial tissue
• Covers exposed surfaces of body
o Protects underlying tissue from its
environment (both internal and external)
• Controls nutrient flow to underlying
tissues
• Produces secretions via secretory cells
• Aids in sensory communication by
changing in response to external stimuli
Ex. Cells in taste buds, retinas, and nasal
cavity linings
• Basal lamina/Basement membrane:
Extracellular matrix consisting of
proteins that attaches and anchors
epithelial tissue to the underlying tissue
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Baker 2016
Types of epithelial tissue
Categorized based on:
• Cell shape/structure
• Layers/thickness
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Epithelial cell shape/structure
• Squamous: Thin, pancake‐
shaped
• Cuboidal: All cell dimensions
relatively equal
• Columnar: Slender and
elongated
9courtesy of OpenStax
Epithelial tissue layers
• Simple = Single layer
o All cells attached directly to basal
lamina and nuclei in straight line
o Function: Allows maximal secretion
and/or absorption
• Stratified = Many layers of cells that
can be shed easily
o Function: Protects underlying tissue
from abrasion
• Transitional: specialized stratified layers of
cuboidal epithelial cells
• Pseudostratified: technically a single
layer of columnar cells that initially
appeared stratified when first
discovered by biologists using low‐
tech magnification
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courtesy of OpenStax
Transitional epithelium
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Examples of epithelial tissue
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courtesy of OpenStax
Muscle tissue
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Muscle tissue
• Functions:
1. Enables movement to occur
• Muscle cells can contract and relax
2. Participates in body’s thermoregulation by producing heat
• Contracting muscle cells generate heat
• Constitutes 30‐40% of total body mass
o Can be major drain on energy efficiency
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Muscle cells
Many names: Muscle fiber, myocyte, myofiber
• Retain ability to change physiology and thus, function
indefinitely
o Physiological/functional plasticity
o Embryonic, fetal/perinatal, α‐cardiac, Types 1, 2A, 2B, 2X*
* We will re‐visit these in greater detail when we talk about muscle development & growth
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Muscle cells: General anatomy
• Sarcolemma = Muscle fiber cell
membrane
o Highly sensitive & responsive to
electrical stimulation by motor neurons
o Multiple pores that enable
communication to occur throughout
the cell
• Sarcoplasm = Muscle fiber
cytoplasm
o High concentrations of proteins &
mitochondria
o Sarcoplasmic reticulum = Muscle fiber
endoplasmic reticulum
• Repositories of Ca2+
• Cytoskeletal elements
o Actin filaments (microfilaments)
o Myosin 15
Courtesy of OpenStax
Muscle tissue
Types:
1. Cardiac
2. Smooth
3. Skeletal*
* We will spend most of our time talking about
skeletal muscle
Characterized based on:
• Function
• Cell structure
o Shape
o Number of nuclei
o Presence or absence of striations
• Organization of striations, if present
• Contractions
o Type ‐Voluntary or Involuntary
o Speed
o Direction
o Coordination
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Cardiac muscle characteristics
• Function: Rhythmic contractions of heart
• Cell structure
o Shape: Short & branched
o Nuclei #: 1‐2 per cell
o Striations?: Yes
• Interdigitated
• Contractions
o Type: Involuntary
o Speed: Fast & slow
o Direction: Unidirectional
o Coordination: High
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Courtesy of OpenStax
Smooth muscle characteristics
• Function: Move substances within the body
o Surrounds many internal organs & vessels of
circulatory system
• Cell structure
o Shape: Spindle‐shaped (e.g., thicker in middle;
tapering toward edges)
o Nuclei #: 1 per cell
o Striations?: No
• Contractions
o Type: Involuntary
o Speed: Slow
o Direction: Multi‐directional
o Coordination: Loose
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Courtesy of OpenStax
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