21. Nervous Tissue Structure And Function

Question 1

What are the 2 parts of the nervous system?

Answer 1

CNS - brain and spinal cord

PNS - cranial nerves and spinal nerves

Question 2

What neurons are present in the CNS and PNS?

Answer 2

CNS - relay

PNS - sensory, motor

Question 3

What is grey matter?

Answer 3

Peripheral in brain and in areas called nuclei
Central in spinal cord (butterfly shaped)
Has nerve cell bodies, dendrites, axon terminals, non-myelinated axons, neuroglia

Question 4

What is white matter?

Answer 4

Central in brain
Peripheral in spinal cord
Has myelinated material
Has nerve fibres that form ascending and descending tracts

Question 5

What are the anterior and posterior prongs in the great matter referred to?

Answer 5

Ventral and dorsal horns, connected by grey commissure

Question 6

What is the outer connective tissue layer surrounding the spinal cord called?

Answer 6

Pia mater

Question 7

What are the properties of a neuron?

Answer 7

Many dendrites
Single axon
Often myelinated

Question 8

Which parts of a neuron are in the CNS?

Answer 8

Main cell body
Dendrites
Proximal part of axon

Question 9

Which parts of a neuron are in the PNS?

Answer 9

Distal axon

Arborisations

Question 10

What is the myelin for the axon produced by and is part of in the CNS and PNS?

Answer 10

CNS - oligodendrocyte

PNS - Schwann cell

Question 11

Describe a motor neurone

Answer 11

Located in CNS to periphery

Function is to end signals to effector tissues

Question 12

Describe a sensory neurone

Answer 12

Located in periphery towards CNS
Function is to send environmental signals to integrative centre
Have ganglions along axon, both pseudounipolar and bipolar

Question 13

Describe integrative neurons

Answer 13

Located in the CNS
Function is to collate all information
Can be pyramidal, interneurons or purkinje cells

Question 14

Describe anaxonic neurons

Answer 14

Location is in retina
Function is to act as relays and thought to hold memory
No axons but many dendrites

Question 15

Which cell bodies are located outside the CNS?

Answer 15

Pseudounipolar (unipolar)
Bipolar
Postsynaptic autonomic neuron cell bodies

Question 16

Which is the most predominant cell type in the CNS?

Answer 16

Interneurons

Question 17

What is a multipolar neuron?

Answer 17

One axon and multiple dendrites
Most common
Most neurons in CNS

Question 18

What is a bipolar neuron?

Answer 18

One axon and one dendrite
Olfactory cells (smell), retina, inner ear

Question 19

What is a unipolar neuron?

Answer 19

Single process leading away from soma

Sensory from skin and organs to spinal cord

Question 20

What are the characteristics of the neuron cell body?

Answer 20

Lots of RER
Lots of Golgi apparatus
Many free ribosomes

Question 21

What are Nissl bodies?

Answer 21

In cytoplasm of neuron

Made of RER and Golgi

Question 22

What is the anterograde movement?

Answer 22

Microtubules in axon attract kinesin
Kinesin binds to empty vesicles and mitochondria
Moves these organelles from soma to synapse

Question 23

What is the retrograde movement?

Answer 23

Microtubules attract dynactin
Dynactin binds to retrograde vesicles
Moves vesicles back from synapse to soma

Question 24

Describe what happens to the vesicle as it moves down the axon

Answer 24

Immature vesicles contain only enzyme in its membrane

As it travels, starts to synthesise neurotransmitter

Question 25

What are the 2 things that could happen to vesicles at the synapse?

Answer 25

Recycled through clathrin-coated endocytosis | Lost to neurolemma

Question 26

What nerve fibres can be present in peripheral nerves?

Answer 26

All types - sensory, integrative, motor | Each separated by connective tissue layers

Question 27

What is the endoneurium?

Answer 27

Loose connective tissue | Surrounds single nerve cells

Question 28

What is the perineurium?

Answer 28

Specialised connective tissue Maintains ionic composition Surrounds clusters of axons (fascicles)

Question 29

What is the epineurium?

Answer 29

Dense irregular connective tissue Separates different types of nerves and fills spaces between facsicles Surrounds groups of fascicles

Question 30

What is the paraneurium?

Answer 30

Fascia that separates nerves from surrounding structures

Question 31

What creates faster saltatory conduction?

Answer 31

Myelinated axons

Question 32

What creates faster conduction?

Answer 32

Large diameter axons

Question 33

How does myelination occur?

Answer 33

1. Axon sitting in grove is surrounded by Schwann cell 2. Mesaxon membrane initiates myelination by surrounding embedded axon 3. Sheet-like extension of mesaxon membrane wraps successively round axon, forming multiple membrane layers 4. Cytoplasm extruded from between 2 apposing plasma membranes of Schwann cell, the becomes compacted to from myelin

Question 34

What is an oligodendrocyte?

Answer 34

Does same thing as Schwann cell but in CNS | Cytoplasmic processes from oligodendrocyte cell body form flattened cytoplasmic sheaths that wrap around each axon

Question 35

How is oligodendrocyte different to Schwann cell?

Answer 35

Oligodendrocytes in CNS Oligodendrocyte wraps around more than one axon simultaneously Oligodendrocytes are incredibly small

Question 36

What are astrocytes?

Answer 36

Control flow of nutrients in CNS Regulate nerve impulses by releasing glutamate near to node of ranvier Impact on numerous nerve cells ‘Feet’ contribute to blood-brain barrier (attach to capillaries causing it to be almost completely covered)

Question 37

Name the 4 support cells in the CNS

Answer 37

Oligodendrocytes Astrocytes Microglial cells Ependymal cells

Question 38

What are microglial cells?

Answer 38

Large cells with elongated nucleus and relatively few processes emanating from cell body Found in CNS Resident macrophage

Question 39

What are ependymal cells?

Answer 39

Line spinal canal Apical surface has cilia and microvilli Synthesise and secrete CSF in ventricles Cilia move cerebrospinal fluid (CSF) through ventricles to spinal cord Microvilli absorb CSF Modified tight junctions between epithelial cells control fluid release into brain

Question 40

How can the molecular and cellular contents of the brain be monitored?

Answer 40

Spinal tap