Introduction to nervous tissue Flashcards
Which two components form the peripheral nervous system
Spinal nerves and cranial nerves
Which two components form the central nervous system?
Brain and spinal cord
The structure of neurones is designed to reflect their function of:
Protection
Support
Intercellular communication
Metabolic activity
Intercellular communication
What is the function of the neuronal axon?
a.Propagate action potentials
b.Convert action potentials
c.Process action potentials
d.Initiate action potentials
a.Propagate action potentials
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?
Neurotransmitters
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
c.Synapse
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
b.Ependymal cells
c.Oligodendrocytes
e.Astrocytes
f.Microglia
Which type of neuroglia forms part of the blood-brain barrier?
a.Astrocyte
b.Ependymal cell
c.Schwann cell
d.Oligodendrocyte
a.Astrocyte
Which type of neuroglia lines the spinal canal?
a.Astrocytes
b.Oligodendrocytes
c.Microglia
d.Ependymal cells
d.Ependymal cells
Which type of neuroglial cell myelinates neuronal axons in the central nervous system?
a.Oligodendrocyte
b.Schwann cell
c.satellite cell
d.Microglial cell
a.Oligodendrocyte
Which type of neuroglial cell myelinates neuronal axons in the peripheral nervous system?
a.Schwann cell
b.Satellite cell
c.Oligodendrocyte
d.Microglial cell
a.Schwann cell
Which type of neuroglial cell has phagocytic capacity?
a.Ependymal cell
b.Satellite cell
c.Astrocyte
d.Microglial cell
d.Microglial cell
What is the role of nerve cells (Neurons)?
Functional unit of NS send signal around the body
What is the role of Glial cells ?
Support and protect cells that provide nutrients and immune functions to the neurones
The function of the nervous system
Provide rapid and precise communication between different parts of the Nervous
body via the action of neurones
Basic structure of neuron
Dendrites
Large cell body
Single axon
Terminal boutons
Where electrical signal converted to chemical signal?
Terminal boutons
What is an alternative name for nerve fibres?
Perikaryon
Dendrite
Axon
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.
Are these large diameter fibres:
Myelinated
Non-myelinated
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.
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
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 .
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.
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.
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.
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.
What is the name of this collagenous tissue layer?
Perineurium
Endoneurium
Epineurium
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.
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
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.
Groups of fascicles are bound together by loose collagenous tissue. What is the name of this layer?
Epineurium
Perineurium
Endoneurium
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.
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.
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.
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
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.
Are all of the nerve fibres myelinated?
Yes
No
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.
Compared with the previous section (sciatic nerve) are these myelinated fibres…..
Of low calibre and widely spaced
Of high calibre and densely packed
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).
What organs do the motor neurones at the lumbar level predominantly innervate?
Lower limb muscles
Digestive system
Respiratory system
Upper limb muscles
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.
What organs do the motor neurones at the cervical level predominantly innervate?
Digestive system
Lower limb muscles
Respiratory system
Upper limb muscles
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).
In which direction does information typically travel in the ventral horns?
Bi-directional
Downwards
Upwards
Downwards
In which direction does information typically travel in the dorsal horns?
Downwards
Upwards
Bi-directional
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.
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
Sympathetic efferent neurones
