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Histology > Nervous Tissue I > Flashcards

Nervous Tissue I Flashcards

1
Q

Central Nervous System (CNS)

A

Brain and Spinal Chord-Derived from the neutral tube

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2
Q

Peripheral Nervous System (PNS)

A

All nervous tissue outside CNS-derived from neutral crest cells

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3
Q

Nervous System main divisions

A

CNS, PNS

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4
Q

Functions of Nerve Cells

A
  • Irritability
  • Conductivity
  • Secretion
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5
Q

Irritability

A

Neurons rapidly respond to some stimuli

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6
Q

Conductivity

A

Transmission of a response spartially and temporarily to another part of the body

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7
Q

Secretion

A

Cell secrete neurotransmitters and other substanes that excite or inhibit neighboring cells

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8
Q

Neurons

A

Nerve cells of the CNS and PNS

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9
Q

Glial Cells

A

Support and protect Neurons

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10
Q

Connective tissue coverings

A

mostly everything is covered by connetive tissues

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11
Q

Bipolar Neurons

A

2 dendrites

  • Retina
  • Cochlear
  • Offactory
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12
Q

Multipolar

A

MOST COMMON

-multiple dendrites

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13
Q

Pseudounipolar

A

Found is dorsal root ganglia

  • Found in peripheral nervous system-tend to be part of long neurons
  • body of cell has been moved to the side
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14
Q

Afferent Neurons

A
  1. Sensory Neurons
  2. Recieve Stimuli from environment and body
  3. impulse travels towards CNS
  4. Cell bodies are near CNS
  5. Consist primarily of pseudounipolar neurons
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15
Q

Efferent Neurons

A
  1. Motor Neurons
  2. Control effector organs such as muscle fibers
  3. impulse travels away from CNS
  4. Cell bodies are within CNS (Exception in ANS)
    a. further classified
    1. Somatic- Voluntary Muscles
    2. Autonomic- Involuntary smooth muscles-both sympathetic and parasympathetic systems
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16
Q

Interneurons

A

Form functional networks or circuits (retina)

  1. Impulse travels within CNS
  2. Major Function-Coordinate all neural activities
  3. Consists mostly of multipolarNeurons
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17
Q

Classification of Neurons

A

-Myelinated
Myelin: formed by 2 different cells
WHAT ARE THEY??
-Non-Myelinated
Significant differences in transmission of the nerve impulses

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18
Q

Another name for Cell Body of a Neuron

A

Perikaryon- The space around the nucleus

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19
Q

Oligodendrocytes found in

A

CNS

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20
Q

Schwann Cells found in

A

Peripheral Nervous System

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21
Q

Perikaryon Structure

A

Perikaryon is like the cutoplasm of any cell

Organelles:
RER, Golgi, Mitochondria, Protein Synthesis Machinery
-Nucleus is centrally located in the cell
–When theyres a problem with the neuron, the nucleus is pulled away from the cell.

Nissl Bodies:

  • are basophilic and they stain in a different way
  • Area of extensive protein synthesis

Cytoskeleton:

  • required because neurons are much longer than any other cell.
  • Neurofilaments-provide cellular support
  • Microtubules-provide intracellular transport/support
  • Actin- Provides secondary transport

Lipfuscin-residual bodies left over from lysosomal digestion

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22
Q

Dendrites

A

Function: Receive Stimuli

  • Procesess that extend from perikaryon
  • Lack Golgi but contain most other components of perikaryon
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23
Q

Axon

A

Initial Segment of Axon is NON-Myelated

  • Axon Hillock
  • Initial Segment
  • Axoplasm
  • Collateral Branches (axon branches)
  • Axon Terminal
  • Axonal Transport
    • Anterograde: kinesin
    • Retrograde: Dyesin
24
Q

Axon Hillock

A
  • Short segment emanating from perikaryon
  • No Nissl Bodies
  • Initial site of microtubule bundling

Initial Segment:

  • Region between axon hillock and initial myelination point
  • Site of Neuron where stimulus is integrated-initiates/suppresses signal down the axon
25
Q

Axonal transport

A

Movement of proteins and vesicles within axon
-Vesicles attached via motor proteins move along microtubules

Two Types:
Anterograde (from perikaryon to axon terminal)= Kinesin

Retrograde (from axon terminal to perikaryon)=Dynein

26
Q

Anterograde Transport

A

From Perikaryon to Synapses

a) slow stream 1-4 mm/day
i. Necessary for axon growth

b) fast stream 50-400 mm/day
i. Vesicles carrying neurotransmitters and other membrane components needed for synaptic transmission (calcium channels)

27
Q

Primary protein responsible for anterograde motion

A

Kinesin

28
Q

Retrograde Transport

A

From synapses and axon to perikaryon

a) intermediate stream 10-100 mm/day
i. considered a salvage pathway

b) transports cytoskeletal components

29
Q

Primary protein responsible for retrograde motion

A

Dynein

30
Q

Axon terminal- Synapses

A

Types of Synapses:

a. Structure behind a Chemical Synapse (has a bigger gap which allows for diffusion)
b. Structure of an electrical synapse- composed of transmembrane proteins called CONNEXINS
c. combining both results in a mixed synapse

31
Q

Chemical Synapses

A

Vesicles:

  • Neurotransmitter vessicles
    • Adrenaline Secreting
    • Acetocholine secreting
  • Hormone Vesicles
  • Depolarization

Arrival of a nerve impulse causes an influx of Ca2+ into the axon terminal

Ca2+ influx triggers exocytosis of neurotransmitter vesicles into the synaptic cleft -Sympatheric, Parasympathetic

Neurotransmitter open or close ion channels to regulate depolarization at the postsynaptic membrane

32
Q

Types of Synapse

A

Axo-dendritic
Axo-somatic
Dendro-dendritic
Axo-axonic

33
Q

Gemmules

A

Show on pic

34
Q

Synapses-Membrane Structure

A
  • Presynaptic Membrane
  • Postsynapic membrane
  • Synaptic Cleft
35
Q

Presynaptic Membrane

A

Terminal ending membrane of axon-

36
Q

Postsynapic membrane

A

Membrane of cell juxtaposed to presynaptic membrane

37
Q

Synaptic Cleft

A

Space between the 2 membranes

38
Q

Synapses Histological View

A

PIC

Presynapic Cells are seen by staining of vesicles

Juxtaposed postsynaptic cell dendrites are vesicle-free

39
Q

Plasma Membrane Pumps

A
  • Pumps shuttles ions from one side of the membrane to another
  • Na+/K+ ATPase pump shuttles 3Na+ out for every 2k+ pumped in
  • ATP is necessary fo rthe action of this pump
  • Sets up an uneven electrochemical gradient
40
Q

How is a plasma membrane pump dipole?

A

Dipole: polarized with negative charge on the inside of cell and positively charged on the outside

41
Q

Ion Channels

A

PIC

42
Q

Nerve Impulse- Resting Potential

A

More K+ Leak channels are open compared to Na+ channels

  • Leakage creates a net negative charge inside
  • Electrochemical difference between the membrane results in an inactive (resting) neuron
  • Chloride Ions usually dont contribute to membrane potential because eiquilibrium potential for Cl-ions equals the resting membrane potential
43
Q

How do you measure Resting Potential?

A

Using 2 microelectrodes
-Inserted into axon
-Contact with external media
(both connected to voltmeter)

**before insertion, the voltmeter reads 0. Upon Insertion -70 mV are read

44
Q

Nerve Impulse- Action Potential

A
  • Resting State
  • Depolarization
  • Repolarization
  • Hyperpolarization
  • Back to resting State

*together the membrane is said to be excitable- phenomenon only resides in membranes of a few types of cells

45
Q

Propagaion of action potential is in ____ Direction

A

ONE direction- this is assured by the inactivared form of the Na+ Channel

-Nothing can get through the channel and the channel cannot be repopened for 2-3 msec

46
Q

Transition States of voltage-gated Na+ channels

A

Closed->open->inactivated->Closed

Closed=membrane polarized
Inactivated, Open=Membrane Depolarized

PIC

47
Q

Action Potential

A

a. In response to a signal, the soma end of the axon becomes depolarized
b. the depolarization spreads down the axon while the the first part of the membrane repolarizes because Na+ Channels are inactivated and additional K+ channels have opened, the membrane cannot depolarize again]
c. the action potential continues to travel down the axon

48
Q

Nerve Impulse-Saltatory Conduction

A

A. cross section of myelin-forming cell which wraps around the axon, the cell forms successive layers of membrane
B. Nodes of Ranvier form as spaces bw cells are left unmyelinated

49
Q

Shwann Cell purpose

A

Schwann cell is wrapping around axon- insulating it from any electrical changes happening outside- changing at different intervals

50
Q

The only point along the axon where Na+ channels are exposed to intersitial fluids. Only point where an action potential can occur

A

Nodes of Ranvier

51
Q

Speed of each action potential is greatly enhanced because…

A

The nodes are spaced much further apart than each Na+ Channel

52
Q

Synapses Saltatory Conduction: Conduction Velocity

A

Effects of myelination:

  • Myelin sheaths insulate and prevent leakage of charge
  • Saltatory conduction in myelinated axons is about 30x faster
    • Voltage- gated Na+ channels located at the nodes
      - AP’s appear to jump rapidly from node to node
53
Q

Synapses Chemical Transmission

A
  1. Action potentials arrive at axon terminal
  2. Voltage-gated Ca2+ channels open
  3. Ca2+ enters the cell
  4. Ca2+ signals to vesicles
  5. Vesicles move to the membrane
  6. Docked vesicles release neurotransmitter by exocytosis
  7. Neurotransmitter diffuses across the synaptic cleft and binds to to receptors
54
Q

Binding of neurotransmitter to receptor allows the ligan gated Na+ ion channel to open in the post synaptic membrane allowing….

A

Na+ ions to diffuse (facillitated diffusion) from the sunaptic cleft into the post-synaptic bulb.

*

55
Q

Synapses-Chemical Transmission

A
  1. Cholinergic junctions are those that release acetlycholine
    • Most Efferent nerves fall into this catagory (parasympathetic)
  2. Adrenergic Juntions are those that release norepinephrine
    • Postganglionic sympathetic neurons fall into this category

Histology (23 decks)

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