PBL(1L) Histology

Histology - Chapter 8

Interneurons

form communicating and integrating network between sensory and motor neurons, 99.9% of all neurons are this.

Perikaryon

cell body of a neuron

Axon

most neurons have only one

Mulipolar

one axon, 2 or more dendrites, MOTOR AND INTERNEURONS

Bipolar

one axon - one dendrite, special senses, retina and CN VIII

Psudeounipolar

develops from bipolar, most are sensory located close to the CNS

Nissl Bodies

ribosomal content

Axon hillock

lacks organelles

Axonal transport

newly synthesized proteins are transported to distant locations within a neuron, bidireectional, mode of communication

Anteroretrograde

Nerve cell body -> periphery, uses kinesin (uses ATP)

Retrograde

from axon terminal and dendrites -> nerve cell body, mediated by dynein

Nueral stem cells

olfactory bulb and dentate gyrus of hippocampus, able to divide and generate new neurons

Nestin

intermediate filament that characterizes neural stem cells - used to ID them

Golgi type 1

skeletal muscle, travel more than a meter

Golgi type 2

interneurons, have very short axons

Symptoms of Parkinsons:

1. resting tremor 2. rigidity 3. increased tone 4. slowness of movement (bradykinesia) 5. lack of spontaneous movement 6. slurred speech 7. loss of postural movement

Secondary parkinsons caused by?

toxins and infection

Parkinsons histologic findings:

Gliosis (increase in the number of glial cells), loss of pigmentation, and Lewry bodies (characteristic inclusions)

Synapses

are not histologically resolvable

Electricl synapses

contain gap junctions and allow movement of ions - the spread of electrical current

SNAREs

v-SNARE (vesicle-bound) and t-SNARE (target membrane bound)

Synaptotagmin-1

replaces the SNARE complex (SNARE dismantled and recycled by SNAP25/NSF)

Presynaptic densities

proteins on cytoplasmic side of the presynaptic membrane, ACTIVE zone

Rab-GTPase, t-SNARE, and synaptotagmin binding protein

Active zones are rich in these

Postsynaptic density

interlinked proteins that serve numerous functions

Porocytosis

secretion of NT w/o vesicle fusion, vesicles anchored at active zones release NT through transient pore

Transmitter gated channels

post synaptic membrane - bind and change conformation

Curare

poison tip arrow, bind to NA+ channels and blocks action of Nicotinic = muscle paralysis

Atropin

belladona, blocks action of muscarinic rececptors

Clostridium botulism

blocks ACH release

Chromaffin cells

also release E into the blood stream (found in adrenal medulla)

Na+ dependent transporters

action of catecholamines terminated by use of these (cocaine and amphetamine block reuptake, lasts longer in synapse)

COMT and MAO

degrade catecholamines - MAO found in outer mitochondria membrane

AChE inhibitors

used for the treatment of Lambert-Eaton, Myasthenia Gravis, glaucoma, and Alzheimers Disease

Slow transport

ONLY ANTEROGRADE

Fast transport

both directions, therefore antero and retrograde

Retrograde transport

is used by viruses and infection, carries to the cell body

Mullers Cells

Retina (peripheral neuroglia)

Schwann cells

develop from NC and differeniate via Sox-10

Abaxonal Plasma Membrane

shwann cell exposed to endoneurium

Adaxonal periaxonal plamsa

direct contact with axon

Mesaxon

axon is completely enclosed by the schwann cell

Guillan-Barre syndrome (PNS) Multiple Sclerosis (MS) - CNS Disease

common life-threatening disease of the PNS, MS damaged, axons exposed to ECM - paralysis, loss of muscle coordination, loss of sense attacks myelin in CNS, destroy oligodendrocytes, MBP is major target, white matter plaques - neuro deficits, unilatera vision issues

Neureglin (Ngr1)

Myelin sheath thickness is regulated by this growth factor that workds on schwann cells

Schmidt-Lanterman Cleft

small islands within successive lamellae of the myelin

Astrocytes

Largest - physical and metabolic support, protoplasmic - outer covering of gray matter, fibrous - inner core of white matter

Tumors from fibrous

80% of all brain tumors, identified via GFAP

Glia limitans

BBB, protoplasmic astrocytes extend processes to basal lamina of pia mater to form this barrier around CNS

Oligodendrocytes (CNS)

maintain myelin sheath on many axons

Myelin of CNS

PLP, MOG, Omgp

Myelin of PNS

Po and PMP-22

Microglia

Phagocytic cells - remove bacteria, microorganisms, play critical defensive role

Epindymal cells

form epithelium like lining of the fluid filled cavities of the CNS, histologically - basal cell surface interdigitates with astrocyte processes

Choroid Plexus

modified ependymal and associated capillaries

Histology - Chapter 12

Ground Substance

other matrix of non-collagenous proteins, only 10% of bone

Collagens?

Type 1 (mostly) and some Type 4

Proteoglycan Macrmolecules

contain glycosaminoglycans - contribute to compressive strength of bone

Mutliadhesive glycoproteins

attach bone cells and collagen to ground substance (= glue b/n collagen and hydroxyapatite) osteonectin - glue b/n collagen and hydroxyapatite osteopontin - attach bone cells to matrix sialoprotein 1 and 2 - mediate cell attachment and initiate Ca2+ phosphate formation during mineralization

Osteocalin

captures calcium from circulation and stimulate OC remodel

Protein S

assists in the removal of cells undergoing apoptosis

MGP

development of vascular calcifications

BMPs (bone morphogenic proteins)

induce differentiation of mesenchymal cells -> osteoblasts

OP-1

recombinant human BMP-7 used clincially to induce bone growth post-op

Lacunae

contain bone cells (osteocyte)

Canaliculi

osteocytes extend numerous processes into these tunnels - connect lacunae

Osteoprogenitor

arise from mesenchyme -> OB, enlongated nuclei

Osteocyte

OB completely surrounded by ECM that it secreted

Bone-lining cells

remain on bone surface when no active growth (come from OB), thought to function in nutirtion and support of osteocytes

Osteoclasts

bone resorption cells that are present on bone surface

Trabeculae

spongelike network consisting of thin anastomosing spicules of bone tissue)

Compact bone

Dense layer outside

Long bones

longer in one direction (tibia, metacarpals)

Short bones

equal in length and diameter (carpal bones)

Flat bones

thin and platelike (skull and sternum) - contains layer of spongy bone b/n two dense layers of compact

Irregular bones

don't fit into any category, complex structure - vertebra, or may contain air/sinus - ethmoid bone

Sharpey's fibers

extend into the bone, continuous with the collagen in ECM

Periosteum

fibrous outer layer that resembles dense CT and inner layer with osteoprogenitor cells

Aricular Cartilage

hylaine cartilage

Endosteum

one-cell think layer that lines bone cavities, w/ osteoprogenitor cells

Arthritis

inflammation of the joints -> degrees of pain

Ankylosis

damged cartilage that calcifies and is replaced by bone

Rhematoid Arthritis

Immune response mediated damage to articular cartilage

Tuberculosis

Infectious response mediated damage to articular cartilage

Gouty Arthritis

deposition of uric acid crystals, common side effect of thiazide diruetics

Haversian canal

contains the vascular and nerve supply

Osteon

concentric lamellae + haversian canal

Interstital lamallae

remnants of previous concentric lamallae

Volkmanns canal

channels in lamallar bone that allow A/V/N from periosteum and endosteum to reach osteonal canal - NOT surrounded by concentric

Nutrient foramina

most likely found in diaphyses and epiphyses

Immature bone

no concentric, more cells than mature, randomly arranged, more ground substance, not heavily mineralized (found in mouth, orthodontic)

CBFA1

triggers differentiation of osteoprogenitor cells -> OB

ALP and osteocalin

used a clinical markers for osteoblast activity

Matrix vesicles

contain ALP and are secreted only during the period where cells produce bone matrix

Osteocytic Osteolysis

degradation of bone by MMPs (maintains that resorptive nature of osteocytes deals with ca2+ homeostasis, not remodelling)

Howship's Lacuna

resorption bay created by OC activity on the bone surface

TRAP

used clinically as a marker of OC activity and differentiation

Osteoclast

large size and marked acidophilia, strong histochemical reaction for acid phosphatase

GMP, CFU-GM

what osteoclasts are derived from

c-fos and NFκB

osteoclast precursors express these transcription factors

RANK

later, is produced and expressed

RANK-RANKL signaling

essential for OC differentiation and maturation

Inflammatory Reaction

inflammation can cause T-lymphos to express RANKL - inflam processes can stimulate OC-mediated bone resorption

OPG

can block RANK-RANKL, it is a decoy -> lack of available RANKL, produced by OB

Ruffled border

part of the OC that is in direct contact with bone

Clear zone (sealing zone)

ringlike perimeter of cytoplasm near the ruffled border that demarcates the bone area being resorbed

EC matrix adhesion molecules

provide tight seal b/n plasma membrane and mineralized matrix of bone, use integrins

Basolateral region

exocytosis of digested material, vesicles fuse here to release their contents - use TRAP

Cathepsin K and MMPs

hydrolytic enzymes that degrade collagen and other proteins in the bone matrix

Decalcify before Digest

carbonic anhydrase II -> H2CO3 -> HCO3 and H+ ->ATP proton pump (H+ thru ruffled) -> into resorption bay

Chief cells of the Parathyroid

secrete PTH

Parafollicular Cells of the Thyroid

secrete calcitonin