Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuroanatomy > Cells and Cytoarchitecture of the Nervous System > Flashcards

Cells and Cytoarchitecture of the Nervous System Flashcards

1
Q

Describe the characteristics of neurons

A
  • A cell body containing the nucleus and most of the cell organelles.
  • A long process - the axon - often stretching for long distances which is responsible for transmitting data from the neurone to other cells.
  • Numerous short, branched processes - the dendrites - which increase the surface area available for connections from axons of other neurons.
  • Specialised junctions - synapses - between the axon and other cells to allow communication.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where does the axon arise from the cell body?

A

The axon hillock.

This area is important because action potentials arise here.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Neurons are highly diverse, but most fall into one of 3 categories. What are these categories?

A
  • Multipolar
  • Bipolar
  • Pseudounipolar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe multipolar neurons

A
  • Most common type of neuron
  • Many dendrites
  • One axon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe bipolar neurons

A
  • One dendrite
  • One axon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe pseudounipolar neurons

A
  • Short process gives rise to axon in both directions
  • Bring in tactile sensation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe typical neurons of the spinal cord

A
  • Large nucleus and prominent nucleolus
  • Cell body has the usual organelles, with an abundnce of rER represented by nissl bodies - each one a clump of rER.
  • Note: the axon lacks rER and golgi apparatus.
  • High amount of rER is an indication of a busy cell.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is axonal transport?

A

Energy moving mechanism to move material up and down the axon, which can be very long.

It is classified by speed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does axonal transport work?

A

Depends upon molecular motors such as kinesin which use microtubules as a sort of railway track to haul attached organelles, vesicles etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the different classifications of axonal transport

A
  • Most rapid is fast axonal transport and it travels up to 400mm / day moving material from the soma.
    • This is anterograde transport.
  • Fast axonal transport travels up to 200mm / day moving material towards the soma.
    • This is retrograde transport.
  • Slow axonal transport occurs at less than 10mm / day.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the neuropil

A
  • Occupies the majority of the space capacity of the grey matter.
  • Consists of a tangle of neuronal and glial cell processes containing a myriad of synaptic contacts.
    • These regions = neuropil
  • Neuropil = meshwork of crossing processes, synaptic processes and blood vessels.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens at a synapse?

A

The vesicles in the ends of axons contain neurotransmitters that are released in response to an action potential and diffuse across the gap and interact with the receptor on the other side.

These neurosecretory elements are either recovered for future use or broken down.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a terminal bouton?

A

Presynaptic axon terminal with vesicles of neurotransmitter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe glial cells

A
  • 10x more numerous than neurons in the CNS
  • There are 4 major types of glial cells:
    • Astrocytes
    • Oligodendrocytes
    • Microglia
    • Ependymal cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the role of astrocytes

A

Many roles in the CNS:

  • Many processes and extensive cytoskeleton so provide some physical support to the tissue by providing a scaffolding for other cells.
  • They surround synapses, and have some neurotransmitter transporters that, in some synapses, helps terminate the effect of the transmitter.
  • Astrocyte processes found near synapses, unmyelinated axons and nodes of ranvier can absorb potassium ions to help maintain the extracellular environment.
  • In development, astrocytes guide the migration of cells and processes.
  • The participate in the formation of the blood-brain barrier.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What 2 forms do astrocytes come in?

A
  • Fibrous astrocytes
  • Protoplasmic astrocytes
  • There are no fundamental differences between these types - the difference is simply that they look different in different locations.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe fibrous astrocytes

A
  • Most common in white matter
  • Have fewer processes which are typically long and thin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe protoplasmic astrocytes

A
  • Most common in grey matter
  • Have numerous short, branching processes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What do astrocytes have in their cytoplasm?

A

Astrocytes have large numbers of intermediate filaments in their cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe astrocytes in the blood brain barrier

A
  • Very impotant in inducing the blood-brain barrier.
  • Many astrocytes send cell processes that are applied to the outer surface of capillaries.
    • Since they typically end in flattened processes, they are called endfeet.
  • The astrocyte endfeet do not have tight junctions, so they do not actually form the blood-brain barrier, but rather they induce the capillary endothelium to form tight junctions.
    • These tight junctions between the capillary endothelial cells form the heart of the BBB.
  • Astrocytes also send similar foot-like processes to form a covering of the CNS just below the pia and ependymal lining of the ventricles.
    • This is called the glia limitans.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe oligodendrocytes

A

Typically small round cells with numerous processes that extend to produce internodes of myelin.

They have a round nucleus, round cell body and not much cytoplasm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the function of oligodendrocytes?

A

To produce myelin in the CENTRAL NERVOUS SYSTEM.

In the CNS, one oligodendrocyte produces several internodes of myelin, unlike in the PNS where a schwann cell only producs a single sheath.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe microglia

A
  • The brain’s own resident population of antigen presenting / phagocytic cells.
  • Of a similar lineage to macrophages and invade the brain from the circulation during development.
  • In resting state, they have:
    • Elongated nucleus
    • A number of short, spiny cell processes
  • When activated (example: by bacterial infection) they become rounder and take on an appearance similar to a macrophage.
  • As antigen presenting cells, they express major histocompatibility complex (MHC) class 2 proteins.
  • They are the smallest of the glial cells.
24
Q

Describe the second population of immune cells ‘in’ the brain

A
  • Perivascular macrophages
  • Found around blood vessels
  • However, since they are on the vascular side of the basal lamina that surrounds the blood vessel, they are not actually within the parenchyma of the CNS
25
Q

Describe ependymal cells

A

Cuboidal / columnar epithelium-like cells that line ventricles.

Ependymal cells don’t have a basal lamina which (strictly speaking) all epithelial cells should.

Line the ventricles in the central nervous system.

Also line the central canal of the spinal cord.

26
Q

Describe ependymocytes

A
  • Form the majority of the ependymal lining of the ventricles.
  • Ciliated
  • Similar to cuboidal / columnar epithelial cells
  • Lack a basal lamina
  • Basally, they interigitate with atsrocyte processes of the glia limitans.
  • Apically, they lack tight junctions, and this allows free exchange between the CSF and the CNS parenchyma.
27
Q

What are tanycytes?

A
  • A small, specialise subset of ependymocytes.
  • Mostly found in the ependyma lining the floor of the 3rd ventricle.
    • Here, there are specialised regions that lack a BBB called the circumventricular organs.
  • Long processes from the tanycytes contact these blood vessels, including those of the hypothalamic-hypophyseal portal system, and these cells are thought to play a role in monitoring hormone levels in the CSF.
  • They respond by discharging secretory products into capillaries (possibly to control secretion from the anterior pituitary).
28
Q

What is the choroid plexus?

A
  • Villous structure with a core of blood vessels covered by a layer of pia mater and an outer layer of choroid epithelium, which are modified ependymal cells.
  • These outer cells are cuboidal and have long microvilli on their surface.
  • Importantly, they have tight junctions between them that constitute the main component of the blood-CSF barrier.
  • These cells secrete most components of the CSF.
29
Q

What are ganlgia and what are the comprised of?

A
  • Neuronal relay centres in the PNS and are comprised of:
    • ​Neurone cell bodies - large with abundant cytoplasm, Nissl substance and large nuclei.
    • Satellite cells and schwann cells (support cells) - small cells which surround the neuronal cell body.
    • Axons
    • Loose fibrocollagenous connective tissue
30
Q

Two types of nerve ganglia can be distinguished on the basis of differing morphology and function. What are they?

A
  • Dorsal root ganlgia
  • Autonomic ganglia
    • Sympathetic
    • Parasympathetic
31
Q

What kind of neurons are in the dorsal root ganglia?

A

Pseudounipolar neurons - NO SYNAPSES!

32
Q

What are present in the autonomic ganglion that aren’t present in the dorsal root ganglion?

A

Synapses

33
Q

Describe a peripheral nerve

A
  • A collection of axons linked together by support tissue into an anatomically defined trunk.
  • The axons may be either:
    • Motor (efferent)
    • Sensory (afferent)
  • They can also be myelinated or unmyelinated
  • A peripheral nerve is composed of:
    • Axons
    • Schwann cells (some of which produce myelin)
    • Fibroblasts which produce fibrocollagenous material
    • Blood vessels
34
Q

Describe the connective tissue of a peripheral nerve

A
  • Peripheral nerves often contain several bundles of axons, each referred to as a fascicle.
  • Connective tissue sheaths associated with peripheral nerves:
    • Epineurium - surrounds the whole nerve.
    • Perineurium - surrounds a fascicle
    • Endoneurium - surrounds fibres within a fascicle
35
Q

Describe the blood-nerve barrier

A

Consists of tight junctions in the intrafascicular capillaries and tight junctions between cells in the perineurium.

36
Q

What are the non-neuronal cells of the peripheral nervous system?

A
  • Schwann cells - larger axons (above 1.5µm) in the PNS are myelinated by Schwann cells (each Schwann cell only forms a single internode of myelin around a single axon).
  • Satellite cells - Flat, epithelia-like cells that surround the neurons which live in the sensory and autonomic ganglia.
37
Q

What are remak bundles?

A
  • Small axons (pain fibres and postganglionic autonomic fibres) are embedded in clefts invaginating into the margins of Schwann cells.
  • Each Schwann cell ‘shelters’ from a few to a few dozen unmyelinated axons.
  • These Schwann cell unmyelinated axon groups are called Remak bundles.
38
Q

Where are unmyelinated axons found?

A

In clefts of the cytoplasm of Schwann cells.

39
Q

What is a Schmidt-Lanterman incisure?

A
  • Within the myelin sheath in both the CNS and the PNS there are sites where a strip of cytoplasm persists across the myelin sheath as a helical spiral.
  • These are Schmidt-Lanterman incisures.
  • They are thought to play a role in allowing the transport of molecules across the sheath, but this is uncertain.
40
Q

Describe a node of ranvier

A
  • The gaps between the segments of myelin along the axon.
  • At these sites the axon membrane is exposed.
  • Node is typically a gap of ~1µm
  • Causes saltatory conduction
  • Increases the speed of conduction substantially (~100 fold or more)
41
Q

Conduction speed of myelinated axons vs unmyelinated axons

A
  • Myelinated axons - maximum conduction speed is 220mph
  • Unmyelinated axons - maximum conduction speed is 2.2mph
42
Q

What are the sensory receptors of the skin?

A
  • Merkel disc - very sensitive to tissue displacement and widely distributed in the skin and some mucosae.
  • Ruffini endings - found in glabrous skin, mainly responds to skin stretch.
  • Pacinian corpuscle - Sensitive to deep pressure. Found deep in the dermis. 20-60 lamellae of connective tissue separated by gelatinous material. Up to 1mm in length.
  • Meissner’s corpuscles - Sensotive to light touch. Widely distributed, but concentrated in areas like fingertips and tongue. Located in dermal papillae.
43
Q

What do neuromuscular junctions consist of?

A

Presynaptic terminal and the motor end plate.

44
Q

What is a motor unit?

A

A single motor neuron and all of the muscle fibres it innervates

45
Q

What are the principal cells of the neocortex?

A

Pyramidal cells (most common cell type).

Fusiform cells that project to the thalamus.

46
Q

What are the interneurons of the cerebral cortex?

A
  • Spiny stellate cells
  • Non-spiny stellate cells, divided into:
    • Basket cells
    • Fusiform cells
    • Horizontal cells
    • Martinotti cells
    • Etc.
47
Q

Which cells in the neocortex are excitatory and which are inhibitory?

A
  • Excitatory:
    • ​Pyramidal cells
    • Spiny stellate cells
  • Inhibitory:
    • Non-spiny stellate cells
48
Q

Describe pyramidal cells

A
  • Triangular with their apex pointing towards the surface of the brain.
  • They have a single long apical dendrite that ascends towards the cortical surface and several basal dendrites that extend horizontally.
  • They have a single axon that arises from the centre of their basal surface and projects out of the grey matter and into the white matter below.
49
Q

Describe layer 1 of the neocortex

A
  • Molecular layer
  • Few cells
  • Mostly:
    • Horizontally arranged axons and dendrites of afferents
    • Intercortical neurons
    • Apical dendrites of pyramidal cells
50
Q

Describe layer 2 of the neocortex

A
  • External granular layer
  • Many small neurons, including interneurons and small pyramidal cells
51
Q

Describe layer 3 of the neocortex

A
  • External pyramidal layer
  • Contains many pyramidal cells as well as other cell types
  • Pyramidal cells, whose axons project to other parts of the cortex get progressively larger moving downward through this layer.
52
Q

Describe layer 4 of the neocortex

A
  • Internal granular layer
  • Mostly spiny stellate cells
53
Q

Describe layer 5 of the neocortex

A
  • Internal pyramidal layer
  • Large pyramidal cells predominate
  • Some other cells also present
  • Pyramidal cells here project to subcortical structures like the brainstem and spinal cord.
  • In the primary motor cortex, the pyramidal cells of layer 5 are giant cells (100µm) and are called Betz cells.
54
Q

Describe layer 6 of the neocortex

A
  • Multiform layer
  • Many different cell types present
  • Fusiform cells here project to the thalamus
55
Q

How is the cortex organised vertically?

A
  • Organised into small vertical regions, about 200-500µm in diameter that respond to the same peripheral stimulus.
  • These are cortical columns.
56
Q

What are the 3 layers of the cerebellar cortex?

A
  • Molecular layer.
  • Purkinje cell layer - only cells which communicate outwith the cerebellar cortex (like the pyramidal cells in the cerebral cortex).
  • Granule cell layer - contains over 50% of the neurons in the brain.

Neuroanatomy (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions