L5 Neural Tissues

Question 1

What is the difference between the central nervous system and the peripheral nervous system?

Answer 1

•CNS is the brain & spinal cord; PNS is all else. CNS is associated with Cerebrospinal fluid. CNS has a different cohort of glial cells (egoligodendrocytes vs Schwann cells)

Question 2

Which embryonic layer/tissue is the nervous system derived from?

Answer 2

•Ectoderm (or neuroectoderm)

Question 3

What are the main functions of neuroglia?

Answer 3

• Protect, nourish, support
• Make myelin (and increase conduction velocity)
• Regulate fluid and ion transport across membranes

Question 4

What is a Node of Ranvier?

Answer 4

• On an axon, this is a segment of an axon that is not covered with myelin, but is bare and facing the extracellular fluid
• It is an excitable part of the axon (whereas membrane under myelin is not excitable)

–Na+ channels are clustered at nodes

•This is where action potentials occur, and it is fundamental in saltatory conduction

Question 5

What is myelin?

Answer 5

• Myelin is a protective substance surrounding axons that is made up of successive layers of plasma membrane. As such, it is mostly lipid bilayers.
• It works as an electrical insulator
• It increases transmembrane resistance and decreases transmembrane capacitance

Question 6

What is the purpose of myelin?

Answer 6

• By reducing transmembrance conductance, myelin can lead to saltatory conduction
• Thus myelin increases conduction velocity.
• This means axons can have a thinner diameter and retain their conduction velocity

Question 7

What histological and physiological traits distinguish a neuron?

Answer 7

• Neurites (outgrowths)
• Excitability (can have action potentials)
• Many neurons have quite large cell bodies

Question 8

What histological traits distinguish an astrocyte?

Answer 8

•Many processes

–Star shaped

•Its feet abut blood vessels

Question 9

What histological traits distinguish a microglial cell?

Answer 9

• Small compared to other glia
• Spindly processes

Question 10

What histological traits distinguish an ependymal cell?

Answer 10

• Adjacent to a Site of CSF
• Organised as an epithelial layer

–I.e. highly cellular

–cilia

Question 11

What histological traits distinguish an oligodendrocyte?

Answer 11

•Can surround multiple axons

Question 12

What histological traits distinguish a Schwann cell?

Answer 12

• Wrapped around an axon
• Only around a single axon
• Peripheral nervous system only

Question 13

What histological traits distinguish
a satellite cell in the peripheral nervous system?

Answer 13

• Small and round
• Located as a group around a neuron’s large soma
• Often shown in Dorsal Root ganglia

Question 14

What is the function of a neuron?

Answer 14

• It communicates information quickly (allowing organism to respond to the environment)
• It does this by firing axon potentials
• In networks, it integrates information

Question 15

What is the function of an astrocyte?

Answer 15

• Support of nervous tissue
• Contributes to blood vessel control in CNS

–Perfusion, possibly permeability

• May be involved in the blood brain barrier
• Repair of nervous tissue after trauma

Question 16

What is the function of a microglial cell?

Answer 16

•Immune defense in the CNS

–Protect nervous tissue

–CNS is immune-privileged due to blood brain barrier

–Antibodies from rest of body are not in CNS

–CNS cannot tolerate inflammation

Question 17

What is the function of an ependymal cell?

Answer 17

•Forms CSF

–Controls fluid and ion transport

•Forms the epithelium that lines ventricular system

Question 18

What is the function of an oligodendrocyte?

Answer 18

•Forms myelin in CNS

–Increase conduction velocity

–Insulates axons

–Increases transmembrane resistance & decreases capacitance

Question 19

What is the function of a Schwann cell?

Answer 19

•Makes myelin in the peripheral nervous system

–Increases conduction velocity

–Insulates axons

–Increases transmembrane resistance & decreases capacitance

Question 20

What is the function of a satellite cell in the peripheral nervous system?

Answer 20

•In PNS, these support neurons

–Control microenvironment

–Similar roles to astrocytes

•Protect and cushion neurons

Question 21

Name a cell type or place where you would find a multipolar neuron.

Answer 21

• Many possible answers, including
• Cerebral cortex –Pyramidal cells
• Cerebellar cortex–Purkinje neurons

Question 22

Name a cell type or place where you would find a bipolar neuron.

Answer 22

• Many possible answers, including
• Retina

–Bipolar cells

•ganglia of the vestibulocochlear nerve

–Bipolar cells

Question 23

Name a cell type or place where you would find a pseudounipolarneuron.

Answer 23

• Best example is dorsal root ganglia
• Also in semilunar ganglia of trigeminal nerve

Question 24

Name a place where you would find afferent neurons.

Answer 24

• Many examples including sensory neurons from
• Special senses (retinal ganglia, cochlea, etc)
• Sensory neurons (and pain receptors) from skin
• Proprioceptors from muscles

Question 25

Name a place where you would find efferent neurons

Answer 25

* Many examples including motor outputs from brain * Motor cortex * Ventral horn of spinal cord

Question 26

What kind of axon fibres have the fastest conduction velocity?

Answer 26

* Neurons that are myelinated * Neurons that have a large cross-sectional area * E.g. Alpha motor neurons

Question 27

Name 4 ways in which glia (in general) differ from neurons (in general).

Answer 27

* Neurons have action potentials, glia do not \*E * Glia do not form synapses * Glia are able to divide, neurons cannot \*E * Glia form myelin sheaths * Neurons are usually bigger \*E * There are many more glial cells than neurons

Question 28

Name 4 differences between a glioma and a neuroblastoma.

Answer 28

* Glioma typically affects older individuals, neuroblastoma typically affects babies and very young individuals * Glioma is usually inside cranium, neuroblastoma is usually outside cranium * Glioma often has a poor outcome (malignant), neuroblastoma often has a good outcome * Neuroblastoma often secrete catecholamines, leading to high blood catecholamines

Question 29

Name two differences between an oligodendrocyte and a Schwann cell.

Answer 29

* Oligodendrocyte is in CNS * Oligodendrocyte typically myelinates many neurons

Question 30

What kind of neurons (histologically) would you expect to find in the dorsal root ganglia?

Answer 30

•Pseudounipolar

Question 31

Name two locations where you would expect to find ganglia in the peripheral nervous system.

Answer 31

* Enteric nervous system –Auerbach’s and Meissner’s * Parasympathetic ganglia in glands * Sympathetic chain ganglia

Question 32

Approximately how many neurons are in the brain?

Answer 32

* 10¹¹ * 100 (American) billion

Question 33

What is a Brodmann area

Answer 33

•A region of nervous tissue on the cerebral cortex –E.g. the primary visual cortex (V1) of the occipital cortex is Brodmann area 17 –E.g. the motor cortex is Brodmann area 4 •Each region is defined by its structure or organisation of cells

Question 34

Which part of the prefrontal cortex is nearest to the primary auditory cortex (on the outer shell of the temporal lobe): ventrolateral, ventromedial, dorsolateral, dorsomedial?

Answer 34

•Ventrolateral prefrontal cortex is closest to the auditory cortex of the temporal lobe