Neurohistology Flashcards
The initial segment of the axon is the first ——— μm after the axon leaves the axon hillock
400 μm
———- is Bundle of axons in PNS
Nerve
Nerve
• ———: Loose CT around each axon
•———: CT around a bundle of axons
• ———: CT around a nerve
Nerve
Bundle of axons in PNS
Endoneurium
• Loose CT around each axon
Perineurium
• CT around a bundle of axons
Epineurium
• CT around a nerve
Neuronal Cell Body
• also called———
• Variablesize
– ~— to —μm diameter
Neuronal Cell Body
• Soma/Perikaryon • Variablesize
– ~5-140 μm diameter
Do dendrites have Rough ER
Yes
The ———— is the
primary receiving site for
synaptic information.
Dendritic tree
The dendritic surface of many neurons has ————- which further increase the synaptic surface area.
Dendritic spines
Abundant neurotubules
and neurofilaments and
components of the rough
endoplasmic reticulum
(Nissl bodies) may extend
into the base of the ———.
Dendrite
———- is the Last site where membrane potentials propagated from synaptic inputs are summated before being transmitted to axon
Axon hillock
——— is a Barrier for lateral diffusion of transmembrane proteins & lipids embedded in plasma membrane
Axon hillock
Do axons have Nissl bodies
No
Classification of neuron based on Dendrite structure
Pyramidal
Stellate
Most neurons of brain & spinal cord are ——— type of neuron
Multipolar
Multipolar neurons are >—% of neurons
99
How many processes do the following have:
Multipolar
Bipolar
Pseudounipolar
Multipolar- >2 processes
Bipolar- 2
Pseudounipolar- 1 process;quickly forms 2 processes
Which neurons are rare
Bipolar neuron
Anterograde transport of a vesicle along a microtubule is mediated by ———.
kinesin.
Retrograde transport of a vesicle along a microtubule is mediated by cytoplasmic ———.
dynein.
Pseudounipolar neuron are (sensory/motor?) neurons – located mainly in ————
Sensory neurons – located mainly in dorsal root ganglia
Classification based on Cell Body & Dendrites
-———-cells : Pyramid-shaped
-———- cells: Star-shaped
Cells can also be classified by whether the dendrites have spines or not
Those that do are called —— Neurons Those that don’t are called ———-
Neurons
Classification based on Cell Body & Dendrites
Pyramidal cells Pyramid-shaped
Stellate cells Star-shaped
Cells can also be classified by whether the dendrites have spines or not
Those that do are called Spiny Neurons Those that don’t are called Aspinous
Neurons
Classification based on Cell Body & Dendrites
——— cells are spiny, while ——- cells can be spiny or aspinous
Classification based on Cell Body &
Pyramidal cells are spiny, while stellate cells can be spiny or aspinous
Neuron Classification by Axon Length
Neuron Classification by Axon Length
Golgi type I Neurons Long axon
Golgi type II Neurons Have short axon
Neuron Classification by Axon Length
Golgi type I Neurons Long axon include:
Golgi type II Neurons Have short axon
Greatly outnumber type I
Numerousin ——— &———
Often (inhibitory/excitatory?) in function
Neuron Classification by Axon Length
Golgi type I Neurons Long axon:
Pyramidal cells
Purkinje cells
Motor cells of spinal cord
Golgi type II Neurons Have short axon
Greatly outnumber type I
Numerousin cerebral&cerebellarcortex Often inhibitory in function
Classification of neurons By Axon Diameter
By Axon Diameter
1. Sensory afferents
-Size: largest -> smallest
-Aa,Ab,Ad,C
2. C: small, unmyelinated
-pain & temperature
3. Aa:
- Proprioceptors in muscle
Neuron Classifications By Function
Neuron Classifications By Function
1. Sensory receptors in PNS
- Motor/efferent neurons
- Inter neurons/ association neurons
Neuron Classifications By Function
1. Sensory receptors in PNS
-Send AP to ——
-———soma
-Located in ganglia in ——
2. Motor/efferent neurons
- ——— soma
-Soma in CNS
- Except ——
-Send AP to —— or ——
3. Inter neurons/ association neurons
-Located in ——
->—% of all neurons
-~ all ——— soma
Neuron Classifications By Function
1. Sensory receptors in PNS
-Send AP to CNS
-Pseudounipolar soma
-Located in ganglia in PNS
2. Motor/efferent neurons
- Multipolar
-Soma in CNS
- Except ANS
-Send AP to muscle or gland
3. Inter neurons/ association neurons
-Located in CNS
->99% of all neurons
-~ all multipolar
-Integration of information
Types of Synapses
Synapses
Axodendritic synapses
Axosomatic synapses
Axoaxonic synapses
Synaptic cleft ~— nm; shorter than — to — nm distance that separates cells at chemical synapse
Synaptic cleft ~3.5 nm; shorter than 20-40 nm distance that separates cells at chemical synapse
CNS Neuroglia include
CNS Neuroglia
• Astrocytes
– Control [ion]
• Microglia
– Phagocytic
• Ependymal cells – Line ventricles
• Oligodendrocytes – Form myelin
Astrocytes
——— -shaped
̈Bind neurons to ——— & ——-
Astrocytes
̈Star-shaped
̈Bind neurons to capillaries & pia mater
——— is the Most abundant glial cells
Astrocytes
Astrocytes functions:
Functions
1) Supportive
2) Insulating, particularly with regard to synapses
3) Electrolyte balance, particularly regarding K+ ions
4) pH balance of extracellular milieu
5) Sequestration of neurotransmitters
6) Communicate with capillary endothelial cells
7) Interactions with immune system
Types of astrocytes
Fibrous astrocytes
Protoplasmic astrocytes
Fibrous astrocytes
-prominent in ——- matter
-describe the processes:
Protoplasmic astrocytes
-prominent in —— matter
-describe the processes:
Fibrous astrocytes
-prominent in white matter
-fine, long, straight processes
Protoplasmic astrocytes
-prominent in gray matter
-wavy, thin, fluffy processes
Ependyma
———-epithelial cells lining the ventricles of the brain & central canal of the spinal cord
Low columnar
Myelin is —% lipid & —% protein & allows for efficient conduction of action potentials down the axon
Myelin is 80% lipid & 20% protein & allows for efficient conduction of action potentials down the axon
Oligodendrocytes (II)
•Unlike ——— cells, form segments of myelin sheaths of numerous neurons at once
Oligodendrocytes (II)
•Unlike Schwann cells, form segments of myelin sheaths of numerous neurons at once
SUPPORTING CELLS IN THE PNS
SUPPORTING CELLS IN THE PNS
• Satellite cells
• Located around nerve cell bodies in
ganglia
• Schwann cells / neurolemmocytes
• Form myelin around axon in PNS
——— disease
-Neurons that produces dopamine in the substantia nigra begin to degenerate.
Parkinson’s
In people with PD, ———- levels are lower in the brain, specifically in the substantia nigra.
, glutathione
Tay-Sachs Disease
Autosomal recessive disease
Mutations in both alleles of a gene——-on chromosome —
HEX A codes for the alpha subunit of the enzyme ———- found in lysosomes
Juvenile: symptoms: —-
Chronic adult form, symptoms:
Tay-Sachs Disease
vAutosomal recessive disease
vMutations in both alleles of a gene (HEX A) on
chromosome 15
vHEX A codes for the alpha subunit of the enzyme beta- hexosaminidase found in lysosomes
vJuvenile: paralysis, dementia, blindness and early death (3 yrs)
vChronic adult form: neuron dysfunction and psychosis
Shingles (Herpes Zoster) (I)
• Shingles is a disease caused by same virus that causes chickenpox called———. After chickenpox, virus remains dormant in —— neurons for life.
• The virus can become active again and cause ——- (unusual skin sensation, itching or a burning, tingling, or shooting pain).
Shingles (Herpes Zoster) (I)
• Shingles is a disease caused by same virus that causes chickenpox (varicella zoster). After chickenpox, virus remains dormant in DRG neurons for life.
• The virus can become active again and cause shingles (unusual skin sensation, itching or a burning, tingling, or shooting pain).
Some researchers believe that ——— is the prime candidate for the location of neural stem cells.
ependyma .
Neurogenesis predominantly occurs in the ——— and ——— zones of the brain.
Neurogenesis predominantly occurs in the subventricular and subgranular zones of the brain.
Multiple sclerosis occurs more in women than in male T or F
T
Multiple Sclerosis (II)
Two characteristic microscopic features are:
Two characteristic microscopic features are: (1) infiltration of inflammatory cells (T cells and macrophages) inside and around multiple sclerosis plaques; (2) plaques of astrocytic aggregates.
Multiple sclerosis
— and — cells, recruited to multiple sclerosis lesions, secrete ———
CD8+ and CD4+ T cells, recruited to multiple sclerosis lesions, secrete cytokines (interleukin-2, tumor necrosis factor-o, and interferon-y).
Multiple sclerosis
T cells secrete ——- which binds to ——- on which glial neuron to induce their programmed cell death.
T cells secrete Fas ligand which binds to Fas receptor on oligodendrocytes to induce their programmed cell death.
Leukodystrophy
They may be inherited in a ———-, ———, or ———manner, depending on the type of leukodystrophy.
They may be inherited in a recessive, dominant, or X-linked manner, depending on the type of leukodystrophy.
