Exam 1 Week 2: ppt 2 Neuron Components

Question 1

Three main parts of a neuron

Answer 1

1. Soma (means “body”): the metabolic and information integrative center of the cell
2. Dendrites: the multiple information inputs into the cell body (soma )
3. Single Axon: the information output of the neuron.

Question 2

Three general parts of Plasma Mebrane

Answer 2

Phospholipid bilayer with imbedded Proteins, lipids, and carbohydrates.

Question 3

Glycoproteins: what are they and the types

Answer 3

Glycoproteins are Carbohydrates associated with membrane proteins and can be either

1. Peripheral -
   
   • internal
   • external
2. Embedded -
   
   • intrinsic

Not sure if this is correct because it conflcts with what I thought I already knew. Asking Dr. Lake.

Question 4

Ionophors

Answer 4

These glycoproteins can form ionic Channels (ionophores). These form membrane-spanning central pores that selectively allow specific ions to diffuse down their gradients. These channels come in 2 forms

1. Leak channels – let ions move spontaneously down their concentration gradients
2. Gated channels – regulated channels
   
   • Ligand – regulated by a chemical binding to a channel – such as a neurotransmitter
   • Voltage (charge) – regulated by changes in charge or potential difference across the membrane
   • Modality – regulated by an external factor such as mechanical forces, specific radiations of the light electromagnetic spectrum as seen at sensory receptors

Question 5

what are leak channels?

Answer 5

let ions move spontaneously down their concentration gradients

(a type of ionophore, glycoproten cell membrane channel)

Question 6

What are Gaited Channels?

Answer 6

(a type of ionophore, glycoproten cell membrane channel)

Gated channels – regulated channels

1. Ligand – regulated by a chemical binding to a channel – such as a neurotransmitter
2. Voltage (charge) – regulated by changes in charge or potential difference across the membrane
3. Modality – regulated by an external factor such as mechanical forces, specific radiations of the light electromagnetic spectrum as seen at sensory receptors

Question 7

the three types of gaited channels

Answer 7

1. Ligand – regulated by a chemical binding to a channel – such as a neurotransmitter
2. Voltage (charge) – regulated by changes in charge or potential difference across the membrane
3. Modality – regulated by an external factor such as mechanical forces, specific radiations of the light electromagnetic spectrum as seen at sensory receptors

Question 8

What are carrier proteins in the cell membrane?

Answer 8

“Pump”

Protein Molecules that bind, transport and then release substances to move them across the cell membrane

Done passively – facilitated diffusion DOWN a gradient

Done actively – use of ATP to move substances UP their concentration gradient

Question 9

Receptor Proteins (everything)

Answer 9

There are Receptor proteins which bind to external substances Ligands is the term used for these external substances which bind to the receptors. There are two types of these ligand receptors

1. Ionotropic receptors – bound to ionic channels figure (a)
2. Metabotropic receptors – bound to enzymes or other chemical systems figure (b)
   
   • like the 2nd messenger system

Question 10

two types of receptor proteins

Answer 10

1. Ionotropic receptors – bound to ionic channels figure (a)
2. Metabotropic receptors – bound to enzymes or other chemical systems figure (b)
   
   • like the 2nd messenger system

Question 11

What is the Soma? What major structures does it contain (including listing the organelles)?

Answer 11

Cell body is trophic, metabolic center of the neuron

Contains:

• Nucleus
• Organelles
  
  • •Mitochondria – high density in neuron and have great need for oxidative metabolism
  • •Rough endoplasmic reticulum (can be called Nissl bodies) & Golgi apparatus - assembly membranes & protein neurotransmitters (packaging)
  • •Lysosomes –membrane breakdown & recycling
  • •Fibrillar structures unique to neurons (Microtubules contribute to structural elements like in other cells, but in neurons are important in transport of chemicals along the axon to/from the cell body as well)
    
    • Neurofilaments
    • Microtubules
      *

(So long as soma is intact, the potential for axonal regeneration and recovery exists even if axon is damaged)

Question 12

Fibrillar structures in Neurons

Answer 12

Neurofilaments
Microtubules

Neurofilaments and Microtubule filaments have unique functions in neurons. Microtubule filaments are also found in other types of cells, where they help with structure (one of their neuron function too). In neurons these structures also play an important role in transport of vesicles, transmitters, trophic agents and membrane fragments along the axon both to and from the cell body to the distal axon terminals

Question 13

What do neurofilaments and microtubules help transport in neurons? (4)

Answer 13

1. vesicles,
2. transmitters,
3. trophic agents and
4. membrane fragments

Question 14

What is it called where axon attaches to cell body?

Answer 14

axon hillock

Question 15

What is the axolemma and axoplasm?

Answer 15

Part of an axon that is continuous with neurolemma and neuroplasm. (so basically the cell membrane and cytoplasm in the axon)

Question 16

What is the most senitive part of a neuron?

Answer 16

The axon hillock of the cell has an enhanced sensitivity to activation.

Question 17

what is specially about the initial portion of an axon and what it is sometimes called?

Answer 17

The Initial portion of the axon is unmyelinated and is sometimes referred to as the initial segment and site of generation of action potentials that will be running down the axon.

Question 18

What is an initial segment?

Answer 18

The Initial portion of the axon is unmyelinated and is sometimes referred to as the initial segment and site of generation of action potentials that will be running down the axon.

Question 19

What is the name for the spots between glial cells that myelinate an axon?

Answer 19

Noes of Ranvier

Question 20

Does an axon have many or few branches?

Answer 20

The axon has many branches - these are Axon collaterals which are major branches. The distal dense branching at the end of these major brnaches are telodendrons. At the end of each of the telodendrons with Axon terminals - synaptic buttons (boutons)

Question 21

Describe the levels (with names) of axon branches:

Answer 21

The axon has many branches - these are

Axon collaterals which are major branches. The distal dense branching at the end of these major branches are telodendrons. At the end of each of the telodendrons with Axon terminals - synaptic buttons (boutons)

Question 22

nerve fiber is another name for ______

Answer 22

axon

Question 23

Who could this be?

Answer 23

Baby Pigmy Hippo!!

Question 24

What influences the rate of conductance in an axon (2 things)?

Answer 24

Diameter

Degree of myelinaton

(more of both increase speed)

Question 25

What do axons make up in the CNS and PNS? (2 each)

Answer 25

–tracts and pathways in CNS
–spinal and cranial nerves in PNS

Question 26

What is Axoplasmic transport?

Answer 26

Axoplasmic transport is the Bidirectionaltransport between cell body and axon terminal

There is

1. Anterograde: fast, 400 mm/day – movement is distal towards the end of the axon
2. Retrograde – proximal movement at half the rate of anterograde

Question 27

What are the two types of axoplasmic transport?

Answer 27

Anterograde: fast, 400 mm/day – movement is distal towards the end of the axon
Retrograde – proximal movement at half the rate of anterograde

Question 28

What are the main things moved in anterograde transport?

Answer 28

§New vesicles & replacement membrane components
(moved to the end of the axon from soma)

Question 29

what does soma mean?

Answer 29

body

Question 30

What are the major things moved in retrograde transports?

Answer 30

Retrograde transports moves

1. used membrane components & vesicles for recycling and
2. neuromodulators signaling axon terminal environment so that the cell body can react to the axon terminal environment – either by increasing or decreasing protein synthesis

Question 31

What is Axoplasmic flow (not transport!)?

Answer 31

• –Unidirectional from cell body toward the axon terminal
• –Slow, .5–6 mm/day
• –Transportation of proteins for microtubules & neurofilaments and transmitter biosynthetic enzyme

(I don’t reall understand this slide. Probalby need the book or his lecture to understand what the words were supposed to mean. It is slide 17)

Question 32

What unintended problem can Retrograde transport cause?

Answer 32

Retrograde transport unfortunately also can include a number of toxins and viruses from the environment to the CNS

Examples include:

1. Clostridium tetani bacterium,
2. Rabies,
3. Herpes simplex virus and
4. Poliomyelitis

Question 33

What does damage to the neuron soma lead to?

Answer 33

Damage to the cell body leads to:

1. Necrosis - death of the neuron and all of its processes
2. Denervation of tissues innervated by that neuron

(Pretty much cannot survive if soma is injured)

Question 34

What is Wallerian Degneration?

Answer 34

Axon Damage leads to Degeneration of axon & myelin sheath distal to damage and back to most proximal node of Ranvier – this pattern is called Wallerian Degeneration

Question 35

What happens to the cell body during Wallerian degneration?

Answer 35

Cell body undergoes changes (chromatolysis) but remains intact

Question 36

How does Axonal Regenration work?

Answer 36

Following degeneration there is axonal regeneration. Axon terminal “sprouts” with growth cones. If one sprout can realign with original path, it regenerates and the other sprouts decay

Axonal regeneration can produce reinnervated target tissue. Regeneration potential in CNS limited so regeneration is of practical significance only in PNS

Question 37

Is neural regeneration of practical significance in PNS, CNS, or both?

Answer 37

Regeneration potential in CNS limited so regeneration is of practical significance only in PNS

Question 38

what does axonal regernation depend on? (2)

Answer 38

1. Extent of damage – extensive damage can lead to cell death
2. If connective tissues intact – to guide the regenerating sprout and axon

Question 39

How fast is the rate of neural regeneration under optimal conditions?

Answer 39

–Under optimal conditions regeneration occurs at a rate of 1 mm/day

Question 40

What are dentrites?

Answer 40

Dendrites are the Receptive portion of the neuron. They are Numerous extensions of the cell body with Short, tapering, irregular branches. Dendritic Branches are covered with knobs called dendritic spines. These greatly expand the surface area of dendrites and expand the potential for synaptic contacts. Activation of these terminals produce Locally conducted non-regenerative potentials

Question 41

what are dendritic spines?

Answer 41

Dendritic Branches are covered with knobs called dendritic spines. These greatly expand the surface area of dendrites and expand the potential for synaptic contacts.

Question 42

Are dendrites variable or uniform in different nerve cells?

Answer 42

Dendrites are highly variable in pattern in different neurons.

1. Motor neuron have extensive 3D branching of dendrites,
2. Purkinje cells have many branches but all in one plane.
3. Pyramidal neurons have a large apical dendrite which in turn have numerous branches.