4 – Neuro Histology Part II

Question 1

Glutamate:

Answer 1

-most common NT in CNS
-always excitatory (depolarizes the cell)
-vast majority of neurons are glutamatergic neurons

Question 2

GABA:

Answer 2

-common NT in CNS
-inhibitory (hyperpolarizes)

Question 3

Neuromodulation:

Answer 3

-some synapses on a neuron do NOT change the MP
*instead they change how the cell responds to other NT

Question 4

Neuromodulation via chemicals:

Answer 4

-can change future synaptic responses
>through intracellular pathways

Question 5

Examples of NTs that can act as neuromodulators within the CNS:

Answer 5

-dopamine
-serotonin
-histamine
-ACh
-NE
-NO
-various neuropeptides
-cannabinoids (endogenous opioids) and endorphins

Question 6

Neuromodulators are secreted as hormones:

Answer 6

-directly from pre-synaptic neuron
-delivered through circulatory system or CSP
>ultimately bind to a receptor on membrane of post-synaptic neuron
*often bound to GCPR

Question 7

Potentiation:

Answer 7

-change in particular synapse that increases or decreases the efficacy (efficiency) of that synapse

Question 8

When synapses are very active=

Answer 8

-it becomes stronger=increase in post-synaptic response
*using a synapse more often will strengthen the synaptic connection

Question 9

Long term potentiation:

Answer 9

-permanent changes in the strength of the synapse
*significant as it is associated with learning and memory

Question 10

Axons:

Answer 10

-long projections from the cell body
-conducts the AP

Question 11

Large diameter and myelinated axons:

Answer 11

-relay AP faster
>myelination from oligodendrocytes (glia)

Question 12

Neurons have various shapes and functions:

Answer 12

-bipolar neuron
-unipolar neuron (ex. sensory, cell body to side, 2 axons)
-multipolar neuron (most common)

Question 13

Nissl substance:

Answer 13

-lots of rER
-high cellular activity within neuronal cell body

Question 14

Anterograde axonal transport:

Answer 14

-neuron synthesizes proteins and transport mitochondria, structural proteins down to the end of the neuron
*cell body to synapse

Question 15

Retrograde axonal transport:

Answer 15

-process of transporting dead organelles from the synapses back to cell body to be destroyed
*synapse to cell body
*many pathogens use this to get into cell body and then into CNS (ex. rabies, tetanus)

Question 16

Tract:

Answer 16

-bundle of axons within CNS
>NOT a nerve (nerves are in PNS)
>usually perform similar function and going in similar direction
>often end or start from nucleus in CNS
*ascending and descending pathways

Question 17

Glia:

Answer 17

-support cells of NS
*not involved in signalling or transferring info

Question 18

Examples of glia in CNS:

Answer 18

-astrocytes
-microglia
-ependymal cells
-oligodendrocytes

Question 19

Examples of glia in PNS:

Answer 19

-Schwann cells
-satellite cells

Question 20

Astrocytes:

Answer 20

-very diverse=many functions
-most abundant glia
>some parts of CNS=90% of cells
-most brain tumours contain almost all astrocytes

Question 21

What are the functions of astrocytes?

Answer 21

1. Produce EC matrix (ex. laminin)
2. Induce formation of BBB
3. Microcirculation
4. Store glycogen and release glucose to neuron when needed
5. Take up excess potassium in EC space

Question 22

Microcirculation and astrocytes:

Answer 22

-one processes near arterioles
-one processes within the neuropil
*can induce relaxation of arterioles to increase blood flow to certain areas of the CNS

Question 23

Oligodendrocytes:

Answer 23

-responsible for myelination within CNS

Question 24

Myelination allows for:

Answer 24

-faster signal transmission
-insulates

Question 25

How does myelination make the signal transmission be faster?

Answer 25

-re-organizes the ion channels (voltage gated Na+ and K+) along the axon to ‘nodes of Ranvier’

Question 26

Microglia:

Answer 26

-NOT cells of neuroepithelium (mesodermal)
-serve as macrophages in the CNS

Question 27

Ependymal cells:

Answer 27

-line the neural canal
-retained in adult
-form a columnar epithelium
-ciliated
-NSCs reside along and between them
-has a choroid plexus

Question 28

Choroid plexus within ependyma:

Answer 28

-produces fluid that is within the ventricles

Question 29

White matter:

Answer 29

-white because it appears that colour in fresh tissues
-formed by myelinated axons-lipids form the myelin sheath
-oligodendrocytes and astrocytes

Question 30

Grey matter:

Answer 30

-NOT gray in fresh section (actually appears pink)
-composed of cell bodies, dendrites, astrocytes, some myelinated axons
-makes up most of the matter of the brain

Question 31

Location of gray and white matter in spinal cord:

Answer 31

-grey: inside (deep), forms the core of SC
-white: forms the outside
*opposite in brain

Question 32

Location of gray and white matter in brain:

Answer 32

-grey: outside
-white: inside
*opposite in SC

Question 33

Damage to white or grey matter:

Answer 33

-different consequences

Question 34

Meninges:

Answer 34

-derived from mesothelium
-external to CNS

Question 35

3 layers of meninges:

Answer 35

-dura matter
-arachnoid
-pia matter
*just cover the CNS

Question 36

Dura matter:

Answer 36

-outermost layer
-dense, fibrous CT

Question 37

Arachnoid:

Answer 37

-middle layer
-2 parts
>adhered to layer of dura
>forms the trabeculae
-cavity: blood vessels and CSF

Question 38

Pia mater:

Answer 38

-innermost layer
-thin layer of CT that is adhered to the surface of the brain and SC