Introduction to nervous tissue

Question 1

Which two components form the peripheral nervous system

Answer 1

Spinal nerves and cranial nerves

Question 2

Which two components form the central nervous system?

Answer 2

Brain and spinal cord

Question 3

The structure of neurones is designed to reflect their function of:

Protection
Support
Intercellular communication
Metabolic activity

Answer 3

Intercellular communication

Question 4

What is the function of the neuronal axon?

a.Propagate action potentials

b.Convert action potentials

c.Process action potentials

d.Initiate action potentials

Answer 4

a.Propagate action potentials

Question 5

Action potentials are initiated in the cell body in response to external stimuli detected by receptors present within dendrites. When the action potential reaches the axon terminals (boutons) this triggers the release of chemicals. What is the generic name for the chemical signals released from the axon terminal?

Answer 5

Neurotransmitters

Question 6

What is the name of the junction where the axon terminals of one neurone interact and communicate with the dendrites of an adjacent neurone in a pathway?

a.Neuromuscular junction

b.Gap junction

c.Synapse

d.Terminal boutonn

Answer 6

c.Synapse

Question 7

Identify the neuroglial cells located only within the central nervous system. Select all that apply.

a.Satellite cells

b.Ependymal cells

c.Oligodendrocytes

d.Schwann cells

e.Astrocytes

f.Microglia

Answer 7

b.Ependymal cells
c.Oligodendrocytes
e.Astrocytes
f.Microglia

Question 8

Which type of neuroglia forms part of the blood-brain barrier?

a.Astrocyte

b.Ependymal cell

c.Schwann cell

d.Oligodendrocyte

Answer 8

a.Astrocyte

Question 9

Which type of neuroglia lines the spinal canal?

a.Astrocytes

b.Oligodendrocytes

c.Microglia

d.Ependymal cells

Answer 9

d.Ependymal cells

Question 10

Which type of neuroglial cell myelinates neuronal axons in the central nervous system?

a.Oligodendrocyte

b.Schwann cell

c.satellite cell

d.Microglial cell

Answer 10

a.Oligodendrocyte

Question 11

Which type of neuroglial cell myelinates neuronal axons in the peripheral nervous system?

a.Schwann cell

b.Satellite cell

c.Oligodendrocyte

d.Microglial cell

Answer 11

a.Schwann cell

Question 12

Which type of neuroglial cell has phagocytic capacity?

a.Ependymal cell

b.Satellite cell

c.Astrocyte

d.Microglial cell

Answer 12

d.Microglial cell

Question 13

What is the role of nerve cells (Neurons)?

Answer 13

Functional unit of NS send signal around the body

Question 14

What is the role of Glial cells ?

Answer 14

Support and protect cells that provide nutrients and immune functions to the neurones

Question 15

The function of the nervous system

Answer 15

Provide rapid and precise communication between different parts of the Nervous
body via the action of neurones

Question 16

Basic structure of neuron

Answer 16

Dendrites
Large cell body
Single axon
Terminal boutons

Question 17

Where electrical signal converted to chemical signal?

Answer 17

Terminal boutons

Question 18

What is an alternative name for nerve fibres?

Perikaryon
Dendrite
Axon

Answer 18

Axon

The perikaryon refers to the cell body of the neurone. Processes of two types extend from the cell body, namely a single axon and one or more dendrites . Dendrites are highly branched tapering processes, which either end in specialised sensory receptors (as in primary sensory neurones) or form
synapses with neighbouring neurones from which they receive stimuli. In general, dendrites function as the major sites of information input into the neurons. Axons are commonly referred to as nerve fibres and carry information from the perikaryon towards the synapse.

Question 19

Are these large diameter fibres:

Myelinated
Non-myelinated

Answer 19

In the peripheral nervous system, all axons are enveloped by highly specialised cells called Schwann cells , which provide structural and metabolic support. In general, small-diameter axons (e.g. those of the autonomic nervous system and small pain fibres) are simply enveloped by the cytoplasm of Schwann cells; these nerve fibres are said to be non-myelinated. Large-diameter fibres are wrapped by a variable number of concentric layers of the Schwann cell plasma membrane forming a myelin sheath; such nerve fibres are said to be myelinated.

Question 20

By looking at the individual fibres at high magnification, you will notice that there are short intervals at which the axon is not covered by a myelin sheath. What is the name of these intervals?

Schwann cells
Nodes of Ranvier
Dendrites
Terminal buttons

Answer 20

Nodes of Ranvier

The myelin sheath of an individual axon is provided by many Schwann
cells (oligodendrocytes in the CNS), each Schwann cell covering only a segment
of the axon. Between the Schwann cells, there are short intervals where the
axon is not covered by a myelin sheath; these points are known as nodes of
Ranvier .

Question 21

What is the function of the nodes of Ranvier? (select all that apply).
Select more than one:

Allows nutrients and waste to enter and exit the neuron.

Inhibits the conduction velocity of axons.

Enhances the conduction velocity of axons.

Answer 21

Allows nutrients and waste to enter and exit the neuron.

The myelin
sheath is lipid rich and forms a barrier to the diffusion of nutrients and
waste from and into the neurone, hence the nodes of Ranvier are important for
enabling these processes.

Enhances the conduction velocity of axons.

The myelin sheath prevents the nerve action potential from being
propagated continuously along the axon, and the action potential travels by
jumping from node to node. This mode of conduction, known as saltatory
conduction, greatly enhances the conduction velocity of axons.

Question 22

Local anaesthesia is widely used in dental practice. The local anaesthetic acts by binding to an internal site on the Na+ channels and blocking them. Why are the nodes of Ranvier important in this process? Select all that apply.

Na+ must pass through the myelin to access sodium channels

Na+ channels are enriched at nodes of Ranvier

They allow Na+ to access the sodium channels.

Answer 22

Na+ channels are enriched at nodes of Ranvier
The myelin sheath acts as a barrier to the diffusion of Na+ ions.
The nodes of Ranvier are important for allowing Na+ access to sodium channels,
which are enriched at the nodes of Ranvier.

They allow Na+ to access the sodium channels.
The myelin sheath acts as a barrier to the diffusion of Na+ ions.
The nodes of Ranvier are important for allowing Na+ access to sodium channels,
which are enriched at the nodes of Ranvier.

Question 23

What is the name of this collagenous tissue layer?

Perineurium
Endoneurium
Epineurium

Answer 23

Perineurium

Within the fascicles, each individual nerve fibre with its investing
Schwann cell is surrounded by a delicate packing of loose vascular supporting
tissue called endoneurium. Each fascicle is surrounded by a condensed layer of
robust collagenous tissue invested by a layer of flat epithelial cells called
the perineurium. In peripheral nerves consisting of more than one fascicle, a
further layer of loose collagenous tissue called the epineurium binds the
fascicles together and is condensed peripherally to form a strong cylindrical
sheath.

Question 24

Under a high magnification, you can visualise the circular profile of the myelin sheath around the densely packed individual nerve fibres. Do these nerve fibres differ in calibre?

No
Yes

Answer 24

Yes
Calibre refers to the diameter of the axon and as can be seen from
the section, there are a wide variety of different diameter nerve fibres.

Question 25

Groups of fascicles are bound together by loose collagenous tissue. What is the name of this layer?

Epineurium
Perineurium
Endoneurium

Answer 25

Epineurium

In peripheral nerves consisting of more than one fascicle, a layer
of loose collagenous tissue called the epineurium binds the fascicles together
and is condensed peripherally to form a strong cylindrical sheath.

Question 26

How can the effectiveness of local anaesthesia be affected by the presence of adipocytes?

The potency of an anaesthetic is associated with its lipid solubility.
Adipocytes sequester the anaesthetic, reducing its potency.

Answer 26

The potency of an anaesthetic is associated with its lipid solubility.

Greater lipid solubility enhances
diffusion through nerve sheaths, as well as the neural membranes of individual
axons comprising a nerve trunk.

Question 27

The local anaesthetic bupivacaine is more lipid soluble compared with lidocaine. Which of these anaesthetics is most likely to be prepared at a higher dose to achieve equivalency of action with the other?

Lidocaine
Bupivaciane

Answer 27

Lidocaine

Lidocaine is less lipid soluble and thus less potent. It is prepared
at 2% concentration (20 mg/ml) compared with 0.5% concentration (5 mg/ml) for
bupivacaine.

Question 28

Are all of the nerve fibres myelinated?
Yes
No

Answer 28

No
The circular profile of the deeply
stained myelin sheath is not evident throughout this area, indicating that many
of the fibres are non-myelinated.

Question 29

Compared with the previous section (sciatic nerve) are these myelinated fibres…..

Of low calibre and widely spaced
Of high calibre and densely packed

Answer 29

Of low calibre and widely spaced

Axon (nerve fibre) calibre correlates positively with myelin sheath
dimensions. With increasing axon calibre, myelin sheaths are proportionally
thicker and longer. Although large diameter, myelinated axons can be observed
in this section, the majority are of low calibre (thin and unmyelinated).

Question 30

What organs do the motor neurones at the lumbar level predominantly innervate?

Lower limb muscles
Digestive system
Respiratory system
Upper limb muscles

Answer 30

Lower limb muscles

Motor neurones are part of the somatic motor system that
innervates skeletal muscle. The volume of gray matter is more extensive in the
lumbar region corresponding to innervation of the lower limbs.

Question 31

What organs do the motor neurones at the cervical level predominantly innervate?

Digestive system
Lower limb muscles
Respiratory system
Upper limb muscles

Answer 31

Upper limb muscles
Motor neurones are part of the somatic motor system that
innervates skeletal muscle. The volume of gray matter is more extensive in the
cervical region corresponding to innervation of the upper limbs (of course the
axons of motor neurones innervating the lower limbs are also present).

Question 32

In which direction does information typically travel in the ventral horns?

Bi-directional
Downwards
Upwards

Answer 32

Downwards

Question 33

In which direction does information typically travel in the dorsal horns?

Downwards
Upwards
Bi-directional

Answer 33

Upwards
The dorsal horns contain the cell bodies of small second-order
sensory neurones. These relay upwards sensory information on pain and
temperature and participate in spinal reflexes.

Question 34

Examine the thoracic region (spinal 3) and identify the small lateral horns. What type of nerves are located here?

Sympathetic efferent neurones
Sensory neurones
Motor neurones

Answer 34

Sympathetic efferent neurones