histology nervous tissue

what are the arrows pointing to?

cell bodies of neurons

label the parts of the neuron

what’s being shown in this picture?

A - Nissel’s Granules

B - Nucleus

what’s being shown in this picture?

dendrites

what are these pictures showing?

dendrites

what are the black arrows pointing to?

myelinated axons

What is each letter labeling?

A - dendritic spines

B - axon

C - cell body

D - dendrites

what is this?

myelinated axon

what is this

unmyelinated axon

what’s the blue arrow pointing to?

Node of Ranvier

what’s circled in this picture?

Nodes of Ranvier

what’s each letter pointing to?

A - Schmidt-Lanterman Cleft

B - Node of Ranvier

C - Myelin

what are these pictures showing?

Microglia

what’s being shown here?

oligodendrocyte

label the two circles

what’s this?

a protoplasmic astrocyte (grey matter)

what’s this?

fibrous astrocyte (white matter)

what’s this?

ependymal layer

label the boxes

what’s being pointed to here?

ependymal cells

what are the blue arrows pointing to?

pyramidal cells

what’s this showing?

white matter with neuropil and glial cells

what are the two types of cells in nervous tissue and what are their functions

1. neuron: specialized in perception of sensory stimuli and processing/receiving info, and transmitting it further to other neurons via nerve impulses

2. neuroglia: support, nourish, and protect neurons

what cell components are and aren’t in neurons?

not really a lot of mitochondria but do have neurofibrils to connect dendrites through cell body and axon

dendrite function

conduct impulses TOWARDS body

axon function

conduct impulses away from body, usually one at a time

dendritic spines

small projections off of dendrite that act as a point of contact where they’re contacting other neurons

synapses

contact points for dendritic spines, can either be between two neurons or between a neuron and a muscle fiber (via neuromuscular junction)

function of myelin in an axon

important for insulating axon and helps speed up impulse

axon hillock

point where cell body merges into axon

Schwann Cell placement in myelinated vs unmyelinated axon

myelinated: sheath wraps around and have Schwann cell at the end all bunched up

unmyelinated: Schwann cell cytoplasm

relationship between diameter of axon and action potential

larger axon diameter = faster action potential

importance of Node of Ranvier

important for nerve impulses and salt conduction by exposing small part of membrane to external environment

how are Schmidt-Lanterman Clefts formed and where are they found?

• formed from myelin clefts of cytoplasm that was left behind during Schwann cell myelinating process

• found in myelinated axons of the PNS

synapse importance with neurotransmitters

action potential comes down and synaptic vesicles release neurotransmitters, which can vary depending on purpose of that neuron and location within body (very specific!)

neuroplasticity

making new synapses to fix or accommodate for injured/damaged synapses; limited ability to produce new neurons but neuroplasticity allows for regrowth and regenerative capacity

3 main phases of neuroplasticity and what happens in each phase

1. injury: injury to neuron occurs, fibers distal to injury (away from cell body) die but Schwann cells above injury remain intact

2. Degeneration (Wallerian degeneration): macrophages clean up tissue debris, soma swells, ER breaks up, nucleus moves off center due to lack of nerve growth factor

3. Regeneration: axon stump sprouts multiple growth processes and regrows through Schwann cells that will create new myelin sheath

Nervous system divisions

CNS: brain/spinal cord, gray/white matter

PNS: nerves/ganglia

Glial Cells

supporting cells of CNS, filling inner spaces of nervous tissue, outnumber nerve cells (10:1) and much smaller than nerve cells

macroglia and microglia cells in CNS

types of macroglia in CNS

Ependymal cells, astrocytes, oligodendrocytes

microglia in the CNS

equivalent to macrophages but reside in brain, dispose of debris, dark stain and dense, found equally in gray and white matter; CEREBRAL CORTEX

oligodendrocytes

not as many processes, end in sheet of myelin, wrap around segment of axon (like Schwann cells but these are only in CNS and these can attach to multiple axons), responsible for normal propagation of action potentials in CNS; MYELINATED WHITE MATTER

astrocytes

most abundant glial cell in the brain, has GFAP (glial fibrillary acidic protein) which is found in the cytoskeleton of astrocytes, star shaped but shape can be varied depending on if it’s in white or gray matter; CAPILLARIES

protoplasmic astrocytes

found in GRAY matter, thicker branches and cell body, more fluffy looking, foot wraps around lots of synapses

fibrous astrocytes

found in WHITE matter, thinner branches, more twig looking, foot process wraps around blood vessels and Nodes of Ranvier

ependymal cells

form epithelial lining of ventricles in the brain and central canal of spinal cord, neuroectoderm, resembles cuboidal or columnar epithelium, dense chromatin, small nucleus and cilia

Wiegart stain

used to highlight different regions of brain and good to differentiate between white and gray matter (gray matter appears lighter and white matter appears darker), usually stains myelin black

Grey Matter

regions with cell bodies together with dendrites and axon terminals (contains lots of other stuff besides myelinated axons), found in surface area of cortex in the brain and deeper in nucleus masses of the brain

white matter

axons gathered into bundles, called white (and usually appears whiter) because of all the myelinated axons (myelin is mostly adipose and adipose appears white), parallel to act as finer tracks/pathways, some distance from cell bodies

betz cells

large pyramidal cells of motor cortex that help in movement; associated with the need to sustain extremely long axons

neuropils

unmyelinated cell processes that look like fibers of CT

what are the 6 layers of the cortex and what is found in each layer

1. Plexiform/Molecular Layer: sparse neurons/glia

2. outer granule layer: smaller pyramidal and stellate neurons

3. outer pyramidal layer: moderate sized pyramidal neurons

4. inner granule layer: packed with stellate neurons, very dense

5. inner pyramidal layer: large pyramidal neurons

6. multiform cellular layer: mix of pyramidal and stellate neurons

*All 6 layers are GREY MATTER, white matter is below these 6 layers*

Cerebellum

gray matter, referred to as “cortex”, has 3 layers

3 layers of cerebellum and whats in each one

1. outer molecular layer: synaptic, lots of axons/dendrites/granule cells, least dense, very light

2. Purkinje Cell layer: very thin, single layer of large pear shaped Purkinje cells, ONLY the cell bodies make up these layers (dendrites part of molecular layer and axons part of granular layer)

3. Inner Granular layer: very dark stained, densely packed granule/golgi cells with small neurons in brain, round/oval, mossy fiber

where are white and gray matter found in Spinal Cord

gray matter: “gray H”, butterfly shape on interior part of spinal cord

white matter: white commissure/area of white matter that’s just interior to central canal

layers of meninges and characteristics of each layer

1. Dura Mater: outermost layer of very dense and fibrous CT that’s tough/impermeable and has arachnoid grannulation/vila

2. Pia Mater: inner most layer, light layer of collagen and fibroblast cells that adhere to outermost layer of proper nervous tissue, very delicate

3. Arachnoid: in between dura and pia, very open/loose, loose CT with some CSF instead of GS, spiderweb-like collagen; subarachnoid space- fluid filled spaces of arachnoid, still within arachnoid layer though

choroid plexus

ventricular system of the brain liked by simple cuboidal epithelium, formed by wrinkles/folds of ependyma, important in forming blood-brain barrier, CSF leaked by these appendable cells at steady state and continues even if drainage points blocked

importance of blood vessels in CNS

small blood vessels are able to penetrate into gray and white matter while large blood vessels remain on surface of brain or spinal cord

2 supporting cells of PNS

Schwann cells and satellite cells

Schwann cells

form myelin around peripheral nerves (only in PNS), can envelope unmyelinated axons but without dense membrane wrapping normally thought of with myelin

satellite cells

round/circular cells found around cell bodies of unipolar axons (Schwann cells are around axons not cell body), sensory ganglia and sensory around unipolar cell bodies

3 layers of CT surrounding bundles of axons/dendrites

1. Epineurium: continuous with dura, in between fassicles

2. Perineurium: bundles of nerves, perineurial epithelium made of squamous perineurial cells and form continuous layer to isolate axon from surrounding CT

3. Endoneurium: each individual nerve fiber, biner network of collagen fibers

what are these showing?

satellite cells

what’s each letter pointing to?

A - Schwann Cell

B - Axon

C - Myelin sheath