Histology Block 3 Exam 1

Front 1

cell body or soma

Back 1

(1) nucleus contains prominent nucleolus >> transcriptionally very active

(2) Nissl bodies - darkly staining RER >> not present in axon or axon hillock

(3) large number of golgi complexes, mitochondria and lysosomes

(4) often sequester substances in storage vesicles over time (ex. aluminum, iron, lipofuscin, melanin, etc.) Kind of like a pack rat. Different neurons in different locations will collect different substances.

Front 2

cytoplasmic extensions
(axons and dendrites)

Back 2

- shape maintained by neurofilaments (cytoskeletal elements) >> visible with silver or gold stains (Figure 7.4) silver and gold allow to stain certain neurons

Front 3

myelinating cells

Back 3

oligodendrocytes (CNS)- can myelinate several axons
Schwann cells (PNS)can myelinate only one axon, but can ensheath several unmyelinated axons

Front 4

neurosecretory granules

Back 4

neurotransmitter plus packaging and transport proteins >> contents released into synaptic cleft upon stimulation of action potential

Front 5

glial cells

Back 5

astrocytes
oligodendrocytes
ependymal
microglial

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astrocytes

Back 6

(1) form framework guide so that axons and dendrites migrate to correct locations during fetal development >> maintained in certain brain regions in the adult

2) move fluid from extracellular spaces to blood vessels (fluid back to capillary)

(3) may play role in blood-brain barrier (pretty much discredited now, though) - form end feet around blood vessels >> create a highly selective permeability

(4) gliosis - form scar when neurons lost (ex: after stroke or other damage to CNS)

Front 7

ependymal

Back 7

appear as ciliated simple cuboidal epithelial cells or nervous tissue (different books will say one or the other) that line the ventricles and the central canal of the spinal cord

Front 8

glial limitans

Back 8

unique basement membrane of the ependymal cells.

Front 9

microglial cells

Back 9

specialized immune cells of the CNS that demonstrate a low level of phagocytosis >> will increase in number if pathogen present within CNS (Figure 7.26)
Amoeboid-like cells that travel around. Can migrate towards the source of infection. Don’t have connective tissue, which is where immune cells function, so the microglial cells (nervous tissue cells) take up that role

Front 10

gray matter and nuclei

Back 10

composed of unmyelinated fibers and nerve cell bodies

Front 11

white matter

Back 11

composed of unmyelinated and myelinated fibers

Front 12

choroid plexus

Back 12

lining of ventricles that produces cerebral spinal fluid (CSF) via selective filtration and supplementation of plasma (allow certain things to leak out. Close to plasma, but it’s been modified). These are highly folded in order to increase surface area

A. composed of simple cuboidal epithelium overlying a highly vascularized connective tissue

Front 13

nerve

Back 13

a bundle of axons and dendrites bound together by connective tissue

Front 14

endoneurium

Back 14

surrounds individual axons/dendrites and any associated Schwann calls

Front 15

perineurium

Back 15

groups axons/dendrites into small bundles called fascicles

Front 16

epineurium

Back 16

tough outer sheath that binds fascicles into a nerve

Front 17

ganglia

Back 17

only site where neuron cell bodies are located outside of the CNS

Front 18

sensory ganglia

Back 18

recognized by pseudounipolar neurons surrounded by a capsule composed of satellite cells

Front 19

autonomic ganglia

Back 19

do not have satellite cells
(1) sympathetic ganglia – recognized by multipolar neurons that lack capsule (Figure 7.21)

a. cell bodies accumulate lipofuschin with age (reddish brown- wear and tear pigment) This is characteristic of sympathetic ganglia. A young child would not show this.

(2) parasympathic ganglia – quite small and embedded within wall of organ to be innervated (Figure 7.22) Not as large as neurons and other ganglia, but larger than other cells.

Front 20

tendon

Back 20

composed entirely of collagen fibers coursing precisely parallel >> attaches muscle to bone
A. fibroblasts arranged in rows and flattened between thick collagen fibers

B. minimum vascularization >> slow to heal

C. fibers bundled into fascicles >> endo, peri and epitendineum

D. often contained in a lubricated tough fibrous sheet >> minimizes friction

Front 21

ligament

Back 21

parallel bundles of collagen and elastic fibers (percentage will differ from ligament to ligament)>> connect bones within a joint

. amount of elastic fibers varies among different ligaments

B. distinguished from tendon via color and abundance of fibroblasts >> elastic fibers may be evident as negative images (due to fact that elastic fibers do not stain)

Front 22

components of muscle tissues

Back 22

A. muscle fibers >> typically grouped in bundles

B. rich capillary networks (Figure 6.7) because they are such major users of energy/ATP.

C. supporting connective tissue rich in collagenous and elastic fibers

Front 23

general info on skeletal muscle

Back 23

1. Cells fuse together during fetal development >> syncytium that may contain several hundred nuclei >> skeletal muscle fiber (ancillary figure)

A. nuclei just below sarcolemma (cell membrane) and usually flattened (Figure 6.3)

B. cytoplasm packed with longitudinally oriented actin and myosin (contractile units) >> precise parallel arrangement produces a striated appearance (Figures 6.10 and 6.9)

C. Cytoplasm also richly endowed with mitochondria and sarcoplasmic reticulum (same as smooth ER) (Figure 6.11)

Front 24

skeletal muscle fiber types

Back 24

differ according to size and specialized staining properties (myoglobin content) (Figure 6.14)
Staining of succinate dehydrogenase (found in Kreb’s cycle) can see three shades of staining.
A. red (aerobic) fibers - small with high myoglobin (looks like monomer of hemoglobin. It is what’s responsible for the color) content and a rich blood supply >> able to generate slow but more sustained contractions. Higher oxygen supply. Ex: muscles that run along spine to hold the head up, etc.

B. white (anaerobic) fibers - large with low myoglobin content and a minimal blood supply >> rapid contractions but easily fatigued

C. intermediate fibers: tend to be most common in common muscles (bicep, tricep, deltoid, etc..)

Front 25

types of innervation of skeletal muscle

Back 25

(1) motor end plates - found at the neuromuscular junction (Figure 7.12)

a. motor nerve axon branches into twigs that innervate several fibers >> fewer fibers per axon yields finer muscle control

(2) sensory - provide information about tension of muscle >> component of feedback system that maintains muscle tone, proprioception and prevents ripping of muscle

a. encapsulated nerve endings within tendon

b. muscle spindle (Figure 7.33)
important for maintaining muscle tone.
i. fibrous capsule containing 5-15 thin intrafusal muscle fibers

ii. two sources of innervation

Front 26

organization of skeletal muscle as an organ

Back 26

A. endomysium - surrounds individual muscle fibers

B. perimysium - groups many muscle fibers together to form a fascicle (Figure 6.2)

C. epimysium - groups many fascicles together to form a muscle

(1) continuous with tendon

Front 27

smooth muscle general info

Back 27

A. myofilaments not well organized >> no striations

(1) oriented in all directions and inserted into anchoring points called focal densities (Figure 6.20)

B. individual cells surrounded by and external lamina composed of reticular fibers (Figure 6.15)

(1) capable of secreting both collagen and elastic fibers for anchoring purposes

C. communication via gap junctions or nexus junctions- link the smooth muscle fibers together.

Front 28

arrangement of smooth muscle within organs

Back 28

A. unitary smooth muscle - cells have synchronized rhythmic contractions stimulated primarily by stretch- connected by the gap junctions: work as a single unit. Same chemical stimulus shared with neighboring cells.

(1) patterns modified by hormonal and/or neural input
Makes mesh or network under cell membrane, so that when contracts it contracts in all directions. Unlike skeletal, which contracts in one direction.
B. multi-unit smooth muscle - precisely controlled by the autonomic nervous system

4. capable of regeneration

Front 29

type 1 neurofibromatosis

Back 29

1. cafe au lait spots
2. neurofibromata
3. skeletal malformations including deformation of sphenoid, bowed legs, scoliosis
4. optic gliomas
5. range of mental deficits

Front 30

cafe au lait spots

Back 30

type 1 neurofibromatosis
. develop in childhood and increase in number and size until puberty

b. most common in axially and inguinal regions

Front 31

neurofibromata

Back 31

– benign tumors of Schwann cells (Figure 2)

a. increased number with age

Front 32

minor features of type 1 neurofibromatosis

Back 32

a. axillary and truncal freckling (Figure 6)

b. macroencephaly: enlarged brain/head. Goes along with dysplasia of bones

c. Lisch nodules (Figure 7 ): nodules on the iris. Rather benign and don’t ause problems

Front 33

type 2 neurofibromatosis

Back 33

much less common
(1) café-au-lait spots and neurofibromata – less severe that type 1

(2) characterized by vestibular Schwannomas (Figure 8) and other CNS tumors in approximately ½ of affected patients. Affects hearing and balance due to affecting cranial nerve.

(3) subclinical cataracts: lens is cloudy. Cataracts in teenager would be a clue that soething is wrong.

Front 34

genetics of neurofibromatosis

Back 34

A. autosomal dominant pattern of inheritance

B. complete penetrance by age 5

C. variable expressivity

D. 100x expected mutation rate

Front 35

molecular genetics of NF1

Back 35

A. loci at 17q11.2 (Figure 9)

B. allelic heterogeneity - wild type gene converted to neurofibromatosis via point mutations, deletions and insertions typically resulting in a truncated protein

c. gene contains 59 exons
D. gene product = neurofibromin >> GTPase-activating protein which down regulates RAS activity

(1) homozygous for NF1 gene results in high rate of malignancy
Increased RAS activity will lead to benign tumors in CNS and other places.
(2) gene also known to play a role in tumorgenesis in non-NF patients

Front 36

molecular genetics of NF2 gene

Back 36

A. loci at 22q 12.2

B. gene product named schwannomin or merlin >> cytoskeletal protein that also counteracts RAS: this is where the similarity is.