Nervous Tissue Structure + Function

Question 1

What is the Central Nervous System?

Answer 1

The brain and spinal chord

Question 2

What is the Peripheral Nervous System?

Answer 2

Cranial nerves and spinal nerves

Question 3

Where is Grey matter found?

Answer 3

Peripheral in the brain in area called “nuclei”

Central in spinal chord (H/butterfly region)

Question 4

What does grey matter consist of?

Answer 4

Nerve cell bodies 
Dendrites 
Axon terminals 
Non-myelinated axons 
Neuralgia (support cells)

Question 5

Where is white matter found?

Answer 5

Central in the brain

Peripheral in spinal chord

Question 6

What is white matter made of?

Answer 6

Myelinated material

Question 7

Describe a cross-section of spinal chord.

Answer 7

Grey matter looks like a butterfly
Have dorsal horn and ventral horn-connected by grey commissure

White after contains fibres that form the acsending and descending tracks.

Question 8

What is the basic structure of a Neuron?

Answer 8

Normal cell organelles
Cytoplasmic projections-one axon, many dendrites
Main body (soma), dendrites and proximal axon in CNS
Distal axon + arborists ions in the PNS
Often myelinated

Question 9

What’s the difference between myelin in the CNS and PNS?

Answer 9

In CNS made from oligondedrocyte

In PNS made from Schwann cell

Question 10

Describe location + function of motor neurone and any special structures.

Answer 10

Location=CNS to periphery

FUnction=send signals to effector tissue

Structure= if cell body is outside the CNS it forms a ganglia

Question 11

Describe location + function of Sensory neurone and any special structure.

Answer 11

Location=periphery to CNS

Function=send environmental signal to integrative centre

Structure=a bipolar neurone has the cell body in the middle, a pseudounipolar neuron has the body to one side of the axon.

Question 12

Describe the function and location of an intergrative neurone, and any special structures.

Answer 12

Location=CNS

Function=Collate all info

Structure=pyramidal cells have a pyramid shap cell body, interneurons have pre and post synaptic neurones, purkinjie cells have many many dendrites into 1 axon.

Question 13

Describe the location and function of an anaxonic neurone and any special structures.

Answer 13

Location=retina (some parts of CNS)

Functions=Act as relays between nerve cells, they can hold the info for a period

Structure= cell body in centre and many dendrites

Question 14

What neurones are located outside the CNS?

Answer 14

Pseudounipolar, bipolar and postsyynaptic autonomic neurone cell bodies are outside CNS

Question 15

How are vesicles moved from the soma (cell body) to the synapse and back?

Answer 15

Anterograde (away from soma) and retrograde (to the soma) vesicles use microtubule “shuttle” system too move from soma to synapse and back. The microtubules can also transport mitochondria, but these don’t return

Question 16

How can you tell if a vesicle is immature?

Answer 16

It only contains enzyme in its membrane, no neurotransmitter etc.

Question 17

How does an immature vesicle develop?

Answer 17

As it travels the length of the axon it synthesis the neurotransmitter.

Transported using microtubules

Question 18

What are the 2 possible fates of a vesicle?

Answer 18

1) Recycled through Cathrin-coated endocytosis (removes plasma membrane from hillock to make vesicle)
2) Lost to the neurolemma

Question 19

List the different types of synapse and why they are classified as such.

Answer 19

Axodendritic-connect directly to plasma membrane of nerve/cell

Axodendritic or dendodendritic -axon terminal synapses with dendritic spine, fit to mould around spine for better neurotransmission

Axoaxonic-synapse at axon is bouton, the axoaxonic synapse may enhance/inhibit the axodendritic synapse

Axo-axonal-impinging another synapse, usually inhibits other outputs

Question 20

What are the connective tissue layers in peripheral layers and what does each surround?

Answer 20

Endoneurium=loose connective, surrounds single nerve cells

Perineurium=specialised connective (transport proteins), maintain ionic composition, surrounds axon cluster/fascicles

Epineurium=dense irregular connective, separates diff nerve types and fills space between fascicles

Paraneurium=fascia that separates nerves from surrounding tissue

Question 21

What does neurone diameter have to do with transmission speed?

Answer 21

Smaller diameter=slower signal

Larger diameter=faster signal

Question 22

How do Schwann cells connect unmyelinated neurones?

Answer 22

Connect a few into a bundle.
The Schwann cell is in the centre
Has clefts along the side to allow fluid to pass through

Question 23

How does myelination effect conduction?

Answer 23

The more myelinated a cell the faster conduction as it is saltatory. The distance between nodes of ranvier is larger in large diameter axons and so conduction is faster as the current jumps further

Question 24

How do Schwann cells perform myelination?

Answer 24

1) The axon sitting in a groove is surrounded by a Schwann cell
2) The mesaxon membrane initiates myelination by surrounding the embedded axon
3) a sheet-like extension of the mesaxon membrane then wraps around the axon, forming multiple membrane layers
4) cytoplasm is extruded form between the two apposing plasma membranes of the Schwann cell, they then become compacted to form myelin.

Question 25

How does an Oligodendrocyte perform myelination?

Answer 25

Same way as Schwann cell but in the CNS.

Cytoplasmic processes from the oligodendrocyte cell body form flattened cytoplasmic sheaths that wrap around each of the axons.

The relationship between cytoplasm and myelin is same as Schwann cells

HOWEVER=oligodendrocytes wrap around more than one axon simultaneously

Question 26

What relationship do unmyelinated nerve cells have with Schwann cells.

Answer 26

Individual axons are engulfed by the cytoplasm of a Schwann cell. Propagation of APs are slow

Question 27

List the 4 support cells in the CNS

Answer 27

Oligodendrocytes
Astrocytes
Microglial cells
Ependymal cells

(All very small compared to the nerves)

Question 28

What is an Astrocyte and what is its role?

Answer 28

Star-like structure

Have “perineural feet” that contain gap junctions (biochem support for endothelial cells, transport nutrients form blood to nerve)

Regulate nerve impulses by releasing glutamate near node of ranvier

Contribute to blood brain barrier (capillary is covered in feet, blood cant get out)

Question 29

What is a Microglial cell and what is its role?

Answer 29

Large cells with elongated nucleus and relatively few recesses emanating from the cell body

Found throughout CS

Resident macrophage (immune function, remove damaged nerve cells, sense increased K+ ions and move toward it)

Also thought to digest the protien tangles related to dementia/Alzheimer’s

Question 30

What are ependymal cells and what is their function?

Answer 30

Line the spinal cord

Derived from neural crest, made of neural tissue

Look like columnar epithelial cells lining spinal canal and brain ventricles, have cilia and microvilli

Joined by a junction complex

Synth and secrete CSF in ventricles
Cilia move CSF through ventricles to spinal cord
Microvilia absorb CSF to remove pathogens and present them
Modified tight junctions control fluid release to brain

Question 31

What is multiple sclerosis?

Answer 31

Remitting+relapsing diseases
Degenerative
Autoimmune degradation of myelin

Symptoms=fatigue, vision problems, slurred speech, numbness, tingling, mobility issues, urinary incontinace, constipation