Histology part 2

Question 1

Neurotransmitters of CNS

Answer 1

-Glutamate
-GABA

Question 2

Glutamate Neurotransmitter

Answer 2

• The most common neurotransmitter of CNS
• Always excitatory (depolarizes the cell)
• Vast majority of neurons are glutamatergic neurons

Question 3

GABA neurotransmitter

Answer 3

-Very common neurotransmitter in the CNS
-inhibitory (hyperpolarizes)

Question 4

Synapses with no effect (neuromodulation)

Answer 4

-some synapses on a neuron do not change the membrane potential (no depolarization or hyperpolarization)
-BUT they change how the cell responds to other neurotransmitters

**So intracellular pathways have the ability to neuromodulate via chemicals and change the future synaptic responses

Question 5

Neurotransmitters that act as neuromodulators within CNS

Answer 5

-dopamine
-Serotonin
-histamine
-acetylcholine
-norepinepherine
-nitric oxide
-various neuropeptides

Question 6

Neuromodulator hormone secretion

Answer 6

-neuromodulators are secreted as hormones in a couple ways:

1. directly from pre-synaptic neuron
2. delivered through the circulatory system or the cerebral spinal fluid, and eventually bind to a receptor on the membrane of a post-synaptic neuron
   *Binding is often to G-coupled protein receptors which uses second messengers to pass on information and cause an effect

Question 7

Potentiation

Answer 7

Refers to the change in a particular synapse that increases or decreases the efficacy of that synapse

-when a synapse is very active, that synapse becomes stronger and there is an increase in the post synaptic response
-using a synapse more often will strengthen the synaptic connection

Question 8

Long term potentiation

Answer 8

-permanent change in the strength of the synapse
**important because it is associated with learning and memory

Question 9

Different synapse connections

Answer 9

-synapses on dendritic spines
-axo-dendritic synapse
-axo-somatic synapse
-axo-axonic synapse

Question 10

Action potential speed

Answer 10

-move down axons
-will be faster if myelinated (by oligodendrocytes)

Question 11

Neuron shapes

Answer 11

1.bipolar neuron
-cell body in middle and axon on either side
2. unipolar
-sensory neurons; cell body up and away and two axons on either side, usually one connecting to CNS and other linked to PNS
3. multipolar
-most common; cell body with dendrites and single axon

Question 12

Neuron cellular activity

Answer 12

-has high cellular activity within neuronal cell body
-full of rER (nissl substance)

Question 13

Anterograde axonal transport

Answer 13

-the synthesis of proteins and the transport of mitochondria, structural proteins, etc. down to the end of the neuron

Question 14

Retrograde axonal transport

Answer 14

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

Question 15

Tract

Answer 15

-bundle of axons within the CNS
**NOT a nerve

Question 16

Nucleus

Answer 16

-bundle of cell bodies in CNS
(ganglion in PNS)

Question 17

Glia

Answer 17

-the support cells of the nervous system. Not involved in signalling or transmitting any information.
-CNS: includes astrocytes, microglia, ependymal cells, oligodendrocytes
-PNS: includes schwann cells and satellite cells

Question 18

Astrocytes

Answer 18

• most abundant glial cells in CNS (in some parts, up to 90% are astrocytes)
• very diverse cells with many functions
  *Most brain tumours are almost all astrocytes

Question 19

Functions of astrocytes

Answer 19

1.produce extracellular matrix (laminin)
2. induce formation of blood-brain barrier
3. Microcirculation- astrocytes have one process near arterioles and another process within the neuropil and can induce relaxation of arterioles to increase blood flow to certain areas of the CNS
4. Store glycogen and release glucose to neurons when needed
5. take up excess potassium in extracellular space

Question 20

Astrocyte appearance

Answer 20

1.fibrous astrocytes
2.protoplasmic astrocyte
3. oligodendrocytes
4. microglial cell

Question 21

Oligodendrocytes

Answer 21

-responsible for myelination within the CNS (schwann cells in the PNS)
-myelination allows for faster signal transmission, as it re-organizes the ion channels (voltage-gated Na and K channels) along the axon to nodes of ranvier
- also involved in insulation

Question 22

Microglia

Answer 22

-small
-not cells of the neuroepithelium (mesodermal)
-they serve as macrophages in the CNS

Question 23

Ependymal cells

Answer 23

-line the canal (fluid filled cavities of CNS), and are retained in the adult forming ciliated columnar epithelium
- there are choroid plexus that produces cerebral spinal fluid that is within the ventricles
-neural stem cells will reside along between ependymal cells

Question 24

White matter

Answer 24

-appears white in fresh tissues (from the lipids)
-formed by myelinated axons
-oligodendrocytes and astrocytes will also be found within the white matter

Question 25

Gray Matter

Answer 25

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

Question 26

Distribution of white vs. gray matter

Answer 26

Spinal cord: gray matter inside forming the core (butterfly) & white matter forms the outside (around butterfly)
Brain: Reverse. Gray matter outside, white matter inside
**Damage to white matter has different consequences than damage to gray matter

Question 27

Meninges

Answer 27

-just in CNS, for protection. Derived from mesoderm.
-composed of 3 layers
-dura mater
-arachnoid
-Pia mater

Question 28

Dura mater

Answer 28

-outermost layer
-dense, fibrous connective tissue

Question 29

Arachnoid

Answer 29

-middle layer
-there are two parts (one part is adhered to the layer of dura, another part forms trabeculae)

Question 30

Pia mater

Answer 30

-innermost layer
-thin layer of connective tissue that is adhered to the surface of the brain