Neural tissues

Question 1

Role of afferent neuron

Answer 1

• Transmit sensory info to brain/spinal cord

Question 2

Role of efferent neuron

Answer 2

• Motor neurons transmitting info from the brain to effector organ ie muscle

Question 3

What is a ganglion

Answer 3

• Group of cell bodies outside CNS

Question 4

Where are motor ganglia located

Answer 4

• Many motor ganglia are located in the sympathetic trunks, two long chains of ganglia stretching along each side of the vertebral column from the base of the skull to the coccyx, these are referred to as paravertebral ganglia

Question 5

Where are prevertebral motor ganglia located

Answer 5

• Located near internal organs innervated by their projecting fibres, while terminal ganglia are found on the surfaces or within the walls of the target organs themselves

Question 6

What are eccentric nuclei

Answer 6

• Eccentric nuclei aren’t in the centre

- Usually in smaller neurons

Question 7

What type of ganglion is the dorsal root ganglion

Answer 7

• A sensory ganglion

Question 8

What are the broadmann areas of the neocortex numbered between

Answer 8

• 1-52

- boundaries determined by cellular cortex

Question 9

What does broadmann area 4 correspond to

Answer 9

• Primary motor cortex

Question 10

What does broadmann area 17 correspond to

Answer 10

• Primary visual cortex

Question 11

What are the protruding processes of a neuron also known as

Answer 11

• Neurites

Question 12

What does arborization refer to

Answer 12

• Refers to the fact that the dendrite splits into branches that make it look like a tree

Question 13

What are the two main factors that increase conduction velocity

Answer 13

• Myelin increases it

- Increase in diameter increases it

Question 14

Describe the classification of neurons

Answer 14

• Multipolar
• Bipolar
• Unipolar
• All neurons have just 1 axon
• Majority of neurons have several dendrites ‘multipolar’

Question 15

Where are pyramidal cells located

Answer 15

• Pyramidal cells are located in the neocortex
• Neocortex is the part of the mammalian brain involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language

Question 16

What are the type of cells in the cerebellum

Answer 16

• Purkinje cells which are GABAergic

- Single layer of them in the cerebellum

Question 17

What type of neurons are present in the dorsal root ganglion

Answer 17

• Pseudounipolar
• One axon
• One dendrite

Question 18

Give an example of where bipolar neurons are present

Answer 18

• Retina
• One dendrite
• One axon
• least numerous
• Sensory neurons

Question 19

Where are true unipolar neurons present

Answer 19

• Sensory cells such as rods and cochlear hair cells

Question 20

How big is the gap of a chemical synapse on average

Answer 20

• 30nm
• Common throughout nervous system
• Signalling is not in retrograde direction(with some exceptions)

Question 21

Give an example of divergent signalling

Answer 21

• Skin receptors

- A single neruon sends its output signal to many neurons

Question 22

Give an example of convergent signalling

Answer 22

• Retina

- Multiple inputs influence a single neuron

Question 23

What percentage of the brain is roughly composed of interneurons

Answer 23

• Brain is 80% interneurons

- Cortex is only 20-30% interneurons

Question 24

How do interneurons receive signals from an alpha neuron

Answer 24

• Receive an excitatory collateral from the alpha neuron’s axon as they emerge from the motor root, and are thus ‘kept informed’ of how vigorously that neuron is firing

Question 25

How do renshaw cells work

Answer 25

• Renshaw cells are inhibitory interneurons found in the gray matter of the spinal cord, and are associated in two ways with an alpha motor neuron
• They send an inhibitory axon to synapse with the cell body of the initial alpha neuron of the same pool

Question 26

How do glial cells differ from neurons

Answer 26

Glia differ from neurons in that they:

• Have no action potentials
• Do not form synapses
• Are able to divide
• Form the myelin sheaths

Question 27

Why are glial cells a common source of tumours

Answer 27

• Due to their ability to divide as adult cells

- Glial cells do not conduct electrical impulses

Question 28

Role of oligodendrocytes

Answer 28

• Production/maintenance of myelin sheath in CNS

- One ligodendryocyte myelinates multiple axons(from different neurons)

Question 29

Role of astrocytes(CNS)

Answer 29

• Supports neurons(star shaped)
• Assists neuronal development/growth(neurotrophic), protects neurons from harmful substances
• Its ‘feet’ on processes about blood vessel endothelium - influence blood and flow and blood-brain barrier

Question 30

Role of microglia(CNS)

Answer 30

• Immune cells
• Protect neurons from disease, migrate to injury sites, engulf microbes/debris
• Of mesodermal origin(like other immune cells), also develop from monocytes
• Actually move around in real time

Question 31

Role of ependymal cells(CNS)

Answer 31

• Line brain’s ventricles and central canal of spinal cord, forms CSF

Question 32

Role of schwann cells(PNS)

Answer 32

• Production/maintenance of myelin sheath, PNS regeneration
• 1 axon wrapped per schwann cell
• Multiple lipid bilayers which allow for resistance, vital for regeneration in the event of trauma

Question 33

Role of satellite cells(PNS)

Answer 33

• Support neurons, regulate exchange of materials between neurons and interstitial fluid
• Perform analogous role in PNS to what astrocytes do in CNS

Question 34

What are gliomas

Answer 34

• Largest group of primary tumours derived from glial cells
• Usually highly malignant
• Grow rapidly
• Difficult to remove completely with surgery
• Usually inside cranium

Question 35

What is a neuroblastoma

Answer 35

• Tumour(cancer)
• Most common in children and infants
• Outside cranium
• Derived from neural crest cells from sympathetic NS

Question 36

What are the two most common metabolites made by the breakdown of epinephrine and norepinephrine

Answer 36

• Homovanillic acid(HVA)
• Vanillylmandelic acid(VMA)
• Neuroblastoma cells can also make these catecholamines, these two catecholamine metabolites can be measured in blood and urine

Question 37

Prognosis for neuroblastomas

Answer 37

• Initial prognosis is typically good, survivors often develop neurological problems - 30 years later
• Treatment depends on type