LEC 9: Histology of the Nervous System - 08.22.14

Question 1

From which embryological structure does the CNS develop and what does it include

Answer 1

• develops from neural tube
• Includes:
  
  • brain (cerebrum and brainstem)
  • spinal cord

Question 2

From which embryological structure does the PNS develop and what does it include

Answer 2

• neural crest derivative
• includes:
  
  • spinal (sensory and motor) nerves
  • sensory ganglia
  • Schwann cells
  • Autonomic nervous system
    
    • sympathetic
    • parasympathetic
    • enteric

Question 3

What are the two (2) main parts of the brain

Answer 3

1. cerebrum
2. brainstem

Question 4

What are the three (3) layers of meninges covering the CNS

Answer 4

1. Dura mater
   * tough, fibrous, protects brain inside skull
2. Arachnoid mater

• arachnoid trabeculae are connective tissue channels that connect arachnoid and pia
• blood vessels go through arachnoid
• arachnoid approximates brain surface

3. Pia Mater
   * follows every nook and cranny of brain

Question 5

meningiomas

Answer 5

tumors in meninges (pia, arachnoid, dura)

Question 6

Ventricular System

Answer 6

fluid filled sac that is the internal core of CNS; filled with CSF, which is produced by the choroid plexus

Question 7

ependymoma

Answer 7

tumors of ependymal cells

Question 8

Ciliated ependymal cells

Answer 8

brain ventricles (ventricular system) are lined by ciliated ependymal cells; promote movement of CSF

Question 9

Four (4) cellular constituents of the CNS

Answer 9

1. neurons (nerve cells)
2. glia (supporting cells)
3. capillaries
4. ependymal cells

Question 10

Parts of a neuron

Answer 10

1. one or more dendrites
   * information/signal receivers
2. a cell body (soma)
   * metabollic support, sums info received
3. one axon
   * transmits message

Neurons are structurally and functionally polarized

Question 11

Neuronal subtypes, categorized by relationship between cell body and its processes

Answer 11

1. multipolar neurons
   * throughout nervous system
2. bipolar neurons
   * only a few places (retina, C8 nerve which controls audio)
3. unipolar neurons
   * found only in sensory ganglia (info coming from skin, muscles, etc.)

Question 12

Neuronal subtypes, categorized by cell body shape and dendritic process morphology

Answer 12

1. pyramidal cells
2. spiny stellate cells

Main 2 types of cells of cerebral cortex

Question 13

Role of spines along axon of pyramidal cells

Answer 13

change with experience, learning, memory, cognition, plasticity, hormones, aging

Question 14

Neuronal subtypes, categorized on the basis of the axon

Answer 14

1. long axon projection neurons

• to other neurons
• to effectors (muscles, glands)

2. short axon interneurons
   * amacrine cells (interneurons in retina)

Question 15

functions of cells with short axons (or no axon, as in amacrine cells)

Answer 15

local circuit neurons (e.g. retina)

Question 16

Two (2) parts of the axonal ending

Answer 16

1. telodendron
2. terminal boutons

Question 17

What are the major organelles found in axon terminals

Answer 17

1. mitochondria (ATP)
2. synaptic vesicles (contain neurotransmitter molecules)

Question 18

Components of synapses

Answer 18

1. presynaptic membrane (with synaptic vesicles)
2. synaptic cleft
3. postsynaptic membrane

NB: can also have axo-spinous synapses

Question 19

Neuromuscular Junction

Answer 19

• motor end plate is an enlarged terminal with:
  
  • synaptic vesicles
  • junctional folds
  • enlarged synaptic cleft
  • muscle sole plate
• end plate is covered by lemmocyte cytoplasm and basal lamina

Question 20

nissl bodies

Answer 20

large glandular body found in neurons; actually RER with rosettes of free ribosomes

NB: spinal cord motor neurons have a prominent nucleus and lots of nissl

Question 21

Lower motor neuron diseases

Answer 21

• polio
• ALS

Question 22

Motor neuron diseases

Answer 22

• Parkinson’s disease and related disorders
• Huntington’s disease
• Alzheimer’s disease and other dementias
• Prion disease
• Spinocerebellar ataxia
• Spinal muscular atorphy

Question 23

Three (3) types of neuronal cell death

Answer 23

1. apoptosis (programmed cell death)
2. necrosis/cytoplasmic
3. authophagy

Question 24

Glia cells

Answer 24

support cells of neuronal cells

Question 25

Three (3) types of glial cells

Answer 25

1. astrocytes 2. oligodendrocytes 3. microglia

Question 26

astrocytes

Answer 26

Protoplasmic, fibrous * structural support * metabolic support * contribute to blood/brain barrier * form CNS scar tissue * provide scaffolding for neuronal migration and axon guidance * may participate in signal processing and memory encoding * scavenge neurotransmitters * send linings around capillaries

Question 27

oligodendrocytes

Answer 27

form CNS myelin

Question 28

microglia

Answer 28

CNS macrophages (exist in resting state, then activated to fight infection)

Question 29

Astrocytes and the blood brain barrier

Answer 29

astrocytic perivascular endfeet wrap around capillaries to protect brain from blood (may have disease in it)

Question 30

What do oligodendrocyte processes form

Answer 30

CNS myelin

Question 31

Nodes of Ranvier

Answer 31

breaks in the myelin, contributes to saltatory conduction (very rapid transmission of info)

Question 32

Multiple schlerosis

Answer 32

a demyelinating disease; plaques = absence of myelin

Question 33

myelin in CNS vs. myelin in PNS

Answer 33

* axons myelinated by oligodendrocytes in CNS * axons myelinated by Schwann cells in PNS

Question 34

Schwann cells

Answer 34

also called neurolemmocytes

Question 35

non-myelinated nerve fibers vs. myelinated nerve fibers

Answer 35

* non-myelinated nerve fibers are invested with neurolemmocytes (Schwann cells) alone * myelinated nerve fibers are invested with neurolemmocytes and several layers of connective tissue

Question 36

Schwannoma

Answer 36

a benign encapsulted tumor orginating from Schwann cells

Question 37

Nodes of Ranvier in CNS vs. Nodes of Ranvier in PNS

Answer 37

* in CNS, Nodes of Ranvier are exposed to extracellular space * in PNS, Nodes of Ranvier are covered by cytoplasmic processes from adjacent lemocytes

Question 38

Connective tissue associated with a peripheral nerve

Answer 38

* all PNS axons are invested with Schwann cells * Schwann cells surrounded by endoneurium * endoneurium surrounded by perineurium, with is lined with perineural epitheliod cells (perineural epithelium) * each nerve fasicle surrounded by perineurium * nerves are composed of multiple fasicles * whole nerve (all fasicles) is enveloped by epineurium

Question 39

What connective tissue surrounds Schwann cells

Answer 39

endoneurium

Question 40

What is perineurium

Answer 40

surrounds endoneurium, lined with perineural epitheliod cells to form perineural epithelium

Question 41

perineural epithelium

Answer 41

perineurium (which surrounds endoneurium) is lined with perineural epitheliod cells

Question 42

What are nerve fasicles surrounded by

Answer 42

perineurium

Question 43

nerves are composed of multiple fasicles; what surrounds all the fasicles together

Answer 43

epineurium