Exam 1 Week 2: ppt 2 Neuron Components Flashcards
Three main parts of a neuron
- Soma (means “body”): the metabolic and information integrative center of the cell
- Dendrites: the multiple information inputs into the cell body (soma )
- Single Axon: the information output of the neuron.
Three general parts of Plasma Mebrane
Phospholipid bilayer with imbedded Proteins, lipids, and carbohydrates.
Glycoproteins: what are they and the types
Glycoproteins are Carbohydrates associated with membrane proteins and can be either
- Peripheral -
- internal
- external
- Embedded -
- intrinsic
Not sure if this is correct because it conflcts with what I thought I already knew. Asking Dr. Lake.
Ionophors
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
- Leak channels – let ions move spontaneously down their concentration gradients
- 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
what are leak channels?
let ions move spontaneously down their concentration gradients
(a type of ionophore, glycoproten cell membrane channel)
What are Gaited Channels?
(a type of ionophore, glycoproten cell membrane channel)
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
the three types of gaited 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
What are carrier proteins in the cell membrane?
“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
Receptor Proteins (everything)
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
- Ionotropic receptors – bound to ionic channels figure (a)
- Metabotropic receptors – bound to enzymes or other chemical systems figure (b)
- like the 2nd messenger system
two types of receptor proteins
- Ionotropic receptors – bound to ionic channels figure (a)
- Metabotropic receptors – bound to enzymes or other chemical systems figure (b)
- like the 2nd messenger system
What is the Soma? What major structures does it contain (including listing the organelles)?
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)
Fibrillar structures in Neurons
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
What do neurofilaments and microtubules help transport in neurons? (4)
- vesicles,
- transmitters,
- trophic agents and
- membrane fragments
What is it called where axon attaches to cell body?
axon hillock
What is the axolemma and axoplasm?
Part of an axon that is continuous with neurolemma and neuroplasm. (so basically the cell membrane and cytoplasm in the axon)
What is the most senitive part of a neuron?
The axon hillock of the cell has an enhanced sensitivity to activation.
what is specially about the initial portion of an axon and what it is sometimes called?
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.
What is an initial segment?
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.
What is the name for the spots between glial cells that myelinate an axon?
Noes of Ranvier
Does an axon have many or few branches?
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)
Describe the levels (with names) of axon branches:
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)
nerve fiber is another name for ______
axon
Who could this be?
Baby Pigmy Hippo!!
What influences the rate of conductance in an axon (2 things)?
Diameter
Degree of myelinaton
(more of both increase speed)
What do axons make up in the CNS and PNS? (2 each)
–tracts and pathways in CNS
–spinal and cranial nerves in PNS
What is Axoplasmic transport?
Axoplasmic transport is the Bidirectionaltransport between cell body and axon terminal
There is
- Anterograde: fast, 400 mm/day – movement is distal towards the end of the axon
- Retrograde – proximal movement at half the rate of anterograde
What are the two types of axoplasmic transport?
Anterograde: fast, 400 mm/day – movement is distal towards the end of the axon
Retrograde – proximal movement at half the rate of anterograde
What are the main things moved in anterograde transport?
§New vesicles & replacement membrane components
(moved to the end of the axon from soma)
what does soma mean?
body
What are the major things moved in retrograde transports?
Retrograde transports moves
- used membrane components & vesicles for recycling and
- neuromodulators signaling axon terminal environment so that the cell body can react to the axon terminal environment – either by increasing or decreasing protein synthesis
What is Axoplasmic flow (not transport!)?
- –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)
What unintended problem can Retrograde transport cause?
Retrograde transport unfortunately also can include a number of toxins and viruses from the environment to the CNS
Examples include:
- Clostridium tetani bacterium,
- Rabies,
- Herpes simplex virus and
- Poliomyelitis
What does damage to the neuron soma lead to?
Damage to the cell body leads to:
- Necrosis - death of the neuron and all of its processes
- Denervation of tissues innervated by that neuron
(Pretty much cannot survive if soma is injured)
What is Wallerian Degneration?
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
What happens to the cell body during Wallerian degneration?
Cell body undergoes changes (chromatolysis) but remains intact
How does Axonal Regenration work?
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
Is neural regeneration of practical significance in PNS, CNS, or both?
Regeneration potential in CNS limited so regeneration is of practical significance only in PNS
what does axonal regernation depend on? (2)
- Extent of damage – extensive damage can lead to cell death
- If connective tissues intact – to guide the regenerating sprout and axon
How fast is the rate of neural regeneration under optimal conditions?
–Under optimal conditions regeneration occurs at a rate of 1 mm/day
What are dentrites?
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
what are dendritic spines?
Dendritic Branches are covered with knobs called dendritic spines. These greatly expand the surface area of dendrites and expand the potential for synaptic contacts.
Are dendrites variable or uniform in different nerve cells?
Dendrites are highly variable in pattern in different neurons.
- Motor neuron have extensive 3D branching of dendrites,
- Purkinje cells have many branches but all in one plane.
- Pyramidal neurons have a large apical dendrite which in turn have numerous branches.
