Lecture 6 - Nervous System Flashcards

1
Q

CNS vs PNS

A

Central nervous system - includes brain and spinal cord
Peripheral Nervous System- includes nervous tissue outside brain and spinal cord (ie. cranial nerves, spinal nerves, ANS)

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2
Q

Cell body (Know Alt. Names)

A

Aka soma, perikaryon

function: supports metabolic and synthetic needs of the neuron

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3
Q

Dendrite

A

provides increased surface area for synaptic input from the other neurons

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4
Q

Axon

A

single axon conducts info away from cell body via action potential
Parts: axon hillock, initial segment, node of ranvier, internodal segment, axon terminal

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5
Q

Axon hillock

A

the ANATOMICAL region where the axon rises from the soma

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6
Q

Initial segment

A

PHYSIOLOGIC trigger zone for an AP; located bw the axon hillock and beginning of myelin sheath

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7
Q

Node of Ranvier

A

Between myelinated segments

conducts AP

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8
Q

internodal segment

A

myelinated segments

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9
Q

Axon terminal

A

conveys info to other neurons via synapses

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10
Q

Multipolar neuron

A

most common
present throughout nervous system
multiple dendrites emerge from the soma
SINGLE axon emerges from soma

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11
Q

Pyramidal Neuron

A

type of multipolar neuron
-large triangular shaped soma
-single apical dendrite extends toward pial surface (the outside of brain)
-multiple basal dendrites
singla axon
-location: cerebral cortex and hippocampus

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12
Q

Bipolar neuron

A
has 2 processes that emerge from soma
-single dendrite 
-single axon
Few locations in CNS
-associated with CN-I (olfactory neurons)
-CN II- retinal bipolar cells)
CN VIII
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13
Q

Unipolar neurons

A

aka pseudounipolar
one process emerges from the soma
-bifurcates into peripheral (receives signals) and central branch (enters the CNS)
-both branches are morphologically axons and can propagate an AP

Location: mainly in the PNS (dorsal root ganglia, cranial nerve ganglia)

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14
Q

Neuronal Cell Body

A

nucleus, rough er, free ribosomes, golgi apparatus, mitochondria, microfilaments, neurofilaments, microtubules

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15
Q

Cell nucleus

A
has euchromatin (dispersed chromatin- available for transcription) 
-well defined nucleolus is common (center for ribosomal RNA synthesis and formation of ribosomal subunits
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16
Q

Cytoplasm In a Neuron

A

contains rER for prot synth

Free ribosomes are scattered within it

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17
Q

Golgi apparatus in a Neuron

A

prominent

packages newly synthesized proteins

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18
Q

mitochondria in a neuron

A

numerous

meet energy requirements

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19
Q

cytoskeletal elements in a neuron

A

microfilaments & neurofilaments, microtubules

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20
Q

Nissl stain

A

light microscopy

BASIC stain - visualization of cell body/soma

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21
Q

Nissl bodies

A

NB: the light microscopic term for aggregates of rER and polyribosomes
Axons does not have Rough ER

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22
Q

Presence of Nissl Bodies location in neuron

A

High in the Soma
presence of NB in Proximal dendrite
-diminishes distally
-Absent in axon

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23
Q

Free ribosomes & Nissl stain

A

may be located in axons and distal dendrites, but do not aggregate and cannot be seen with light microscope
-do not form Nissl Body

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24
Q

Ganglion vs Nucleus

A

ganglion: collection of neuronal cell bodies outside CNS
- Note: their cell bodies are surrounded by small support cells called satellite cells (glial cells)

Nucleus: collection of neuronal cell bodies within CNS

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25
Q

Dendrites

A

receive signals

  • extensive branching pattern allows dendrites to receive input from many neurons simultaneously
  • dendritic spines increase surface area for synaptic contact
  • base of dendrites contain typical organelles EXCEPT golgi apparatus
  • many organelles become absent distally
  • contain cytoskeletal elements: micro and neurofilaments, microtubules
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26
Q

axons

A

arise from soma as a single process, may extend long distances
NO golgi apparatus
-may see occasional ribosomes, not large aggregates
contain cytoskeletal microfilaments, neurofilaments and microtubules

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27
Q

Cytoskeletal elements

A

microfilaments
Neurofilaments
Microtubules

(small ->large)

28
Q

microfilaments

A

smallest diameter, actin filaments

location: mainly along the cell membrane around the soma
function: provides structural support to the cell and maintains cell shape

29
Q

neurofilaments

A

intermediate filament

function: provides structural support of cell

30
Q

Microtubules

A

largest diameter

function: key role in an intracellular transport system toward and away from the cell body

31
Q

Axonal transport

A
  • energy dependent transport
  • moves to and from axon terminal along microtubules
  • too long to allow efficient movement of substances between the soma to the axon terminal by simple diffusion
  • dendrites have capacity to transport substances but is not as extensive as in the axon
32
Q

anterograde vs retrograde transport

A

Anterograde- from soma to axon terminal

Retrograde - from terminal to soma

33
Q

anterograde transport

A

involves KINESIS, a microtubule associated protein that moves along microtubules

34
Q

Kinesin

A

‘molecular motor’

interacts with both the microtubule and element to be transported in anterograde motion from soma to axon terminal

35
Q

retrograde transport

A

involves DYNEIN and moves from axon to soma

36
Q

dynein

A

microtubule associated protein

moves vesicles along microtubles but in retrograde

37
Q

Synapse

A

mediates info transfer bw neurons

-includes: presynaptic element and post synaptic element

38
Q

presynapse

A

axon terminal/bouton
contains NT in membrane bound synaptic vesicles
presence of mitochondria

39
Q

postsynapse

A

NT binds to receptor on post membrane

results in electrical signal in postsynaptic neuron

40
Q

Types of synapses

A

axosomatic
axodendritic
axoaxonic

41
Q

Axosomatic

A

axon forms a synapse with a cell body

42
Q

axodendritic

A

axon forms a synapse with a dendrite

43
Q

axoaxonic

A

axon forms a synapse with another axon

-synapses modulate activity of other two types

44
Q

Neurological cells

A

astrocytes, microglia, oligodendrocyte, schwann cells

45
Q

Astrocytes Function and location

A

located throughout CNS
cover most surfaces of neuron (soma, dendrite, node of ranvier) via cytoplasmic extensions (astrocytic processes/end feet) (END FEET)
- outer surface of brain and spinal cord is covered with astrocytic processes called glial limiting membrane
- every blood vessel in CNS is covered by astrocytic processes that seperate it from the neural tissue
-provide structural support in CNS
-protect neurons by removing ions and neurotransmitters (eg. glutamate) form extracellular space

46
Q

glial limiting membrane

A

glial limiting membrane that covers brain and spinal cord
-a specific astrocyte
Just below the Pia Mater

47
Q

Astrogliosis (gliosis)

A

transformation astrocytes from a quiescent to reactive state in response to CNS injury
cellular changes associated with astrogliosis: increased number of astrocytes, increased cell size, extension of cytoplasmic process, increased production of intermediate filaments
changes give rise to formation of a dense gliotic scar
can last weeks, months, years
If you see thesse you know there was an injury but you do not know when

48
Q

Horseradish peroxidase

A

 Enzyme injected into specific terminal and will be transported back to the cell body
 Studies wanted to see if this retrograde motion would affect Primate teeth to find cell bodies
•Results -Labelled neurons in ipsilateral trigeminal ganglion, mesencephalic nucleus and superior cervical ganglion

49
Q

clostridium tetani

A

Tetanus bacteria takes advantage of reterograde transport

- toxin can block inhibitory interneuron receptors and cause tetanic contraction

50
Q

Rabies

A

travels retrograde to CNS

51
Q

Alzheimer’s disease

A

Tau protein on microtubule becomes hyperphosphorylated

- becomes unstable and can no longer stabilize microtubules, depolymerizes

52
Q

CTE

A

evidence of hyperphosphorylation of tau protein

53
Q

Microglia

A

transform from a quiescent to reactive state in response to CNS injury; process is termed microgliosis

  • remove foreign and degenerating cellular elements through phagocytosis
  • microglia return to resting state once reactive process has ceased
  • If you see them then you have a current active problem
54
Q

Microgliosis

A

Key changes
Increased number of microglia
increased cell size
includes extension of cytoplasmic processes

55
Q

Oligodendrocyte

A

responsible for producing and maintaining the myelin sheath around CNS axons
One Cell Body away from the nerve acting on multiple axons
ID on pic

56
Q

Schwann Cells

A

form myelin sheath around axons in PNS
Each schwann cell myelinates a single internode (an internode is a myelinated axonal segment between two nodes of ranvier
- contact both myelinated and unmyelinated axons in the PNS
- unmyelinated are surrounded by the schwann cell plasma membrane (for protection)

57
Q

Epineurium

A
conective tissue of nerve cell 
outermost layer
Dense CT forming most of the CT investment
Thickest of the three
surrounds the entire nerve
58
Q

perineurium

A

middle layer
dense CT layer that surround a bundle of axons within the nerve
ARound the nerve fassicle

59
Q

Endoneurium

A

innermost layer
Loose CT that surrounds individual axons
Around an individual Nerve

60
Q

PNS damage and regeneration

A

Retrograde: axon proximal to injury degenerates
Anterograde: axon distal to injury degenerates
local: axonal ends retract; macrophages and fibroblasts gather

61
Q

neurolemma

A

the thin sheath surrounding a nerve axon maintained by the schwann

62
Q

Regeneration of Nerve

A

within 96 hours of injury, the axon proximal to the lesion sends out sprouts
if the axonal sprouts reach the tube left by schwann cells, then the axon is guided to the target (1 mm/day)
The schwann cells maintain the path that the nerve should take and it follows this

63
Q

Non continuous neurolemma Regeneration of Nerve

A

if the cut ends of the axon are separated such that there is a non continuous neurolemma (aka the schwann cells dont maintain the path), then the regrowth of the axon toward its target is disrupted and reinnervation of the target cannot occur

64
Q

Nerve vs tract

A

nerve: collection of nerve fibers that carries info to and from the CNSd
Tract: collection of nerve fibers within the CNS

65
Q

What Are the Morphological Classifications for Neurons

A

Multipolar
Pyrimidal
Bipolar
Unipolar (pseudounipolar)

66
Q

Dorsal Horn

A

The location in which the axon enters the spinal chord

67
Q

What are the connective tissue of peripheral Nerves

A

Epinerium, Perioneruium, Endoneurium