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Fundamentals of Neuroscience > Exam 1: Slide 2 > Flashcards

Exam 1: Slide 2 Flashcards

1
Q

Diversity of Neurons

A

-About 50 different neuronal types have been discovered, based on the cytology (and its subsequent function)

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2
Q

Neurons differ from most other cells in the body in that:

A
  • Neurons are more polarized, meaning the cytoplasm inside differs in composition to the outside, producing an electrical difference between the inside and outside of the cell
  • Because of the polarization, neurons are highly excitbale compared to other cells
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3
Q

Neuronal membrane

A

-consists of the same lipid bilayer that other cells of the body have, meaning there is a hydrophobic barrier to prevent most water-soluble substances from going in/out of the neuron

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4
Q

Cytoplasm of Neurons

A

Cytosolic Proteins and Membraneous Organelles

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5
Q

Cytosolic Proteins

A

– “housekeeping” function, enzymes to produces substances such as neurotransmitters, cytoskeletal to provide structure/move vesicles

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6
Q

Membraneous Organelles

A

– mitochondria, rough ER, smooth ER, Golgi body

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7
Q

Is the cytoplasm continuous and have the same composition throughout the neuron? Cell Body and Dendrites

A

-All neuronal parts have mitochondria and the smooth ER
-The cytoplasm of the neuronal cell body is functionally continuous with dendrites, meaning that all of the organelles in the cell body are present in the dendrites
-Differences exist in the concentrations of these
organelles i.e. the cell body will generally have more

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8
Q

Is the cytoplasm continuous and have the same composition throughout the neuron? Axons

A
  • axonal cytoplasm is functionally separate, though still continuous with the cell body
  • largely does not have the protein making machinery (ribosomes, RER, the golgi)
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9
Q

Capabilities of Each Part of the Neuron?

A

The cell body and dendrites can make own proteins, while axons have to get proteins shipped

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10
Q

Cytoskeleton

A
  • helps give the neuron its shape and help localize organelles to their locations
  • Neurons, given their functionally separate parts and often long axons, have high amounts of these proteins: up to 25% of the total neuronal protein.
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11
Q

Three Main Types of Cytoskeletal Proteins:

A
  1. Microtubules
  2. Neurofilaments
  3. Actin Microfilaments
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12
Q

Microtubules

A

– long protein scaffolds that run along the entire length of the neuron. Organelles and vesicles (filled with neurotransmitters) are transported along these proteins.

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13
Q

Neurofilaments

A

– the most abundant cytoskeletal protein and play the major role in creating the cytoskeleton throughout the neurons.
- Alzheimer’s disease is in part characterized by these proteins becoming tangled (i.e. the neurofibrillary tangles)

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14
Q

Actin Microfilaments

A

– concentrated at the neuronal periphery, where its role is to contribute to creating microdomains of proteins and stabilization of the neuronal “ends”. These proteins also help transport protein like microtubules.

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15
Q

How does the neuron transport proteins to the axon?

A
  • In order for neurons to signal with each other, there needs to be ion channels in the membrane to change neuronal excitability and produce neurotransmitter release
  • Ion channels are proteins and the axon is not capable of making them (remember, axon has limited synthesis machinery)
  • Axons need a transport system to get proteins and other components to/from the cell body
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16
Q

Two Ways/Mechanisms to Move Proteins:

A

fast axonal transport and slow axonal transport

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17
Q

Fast Axonal Transport

A
  • Protein-filled membranous organelles (such as what ion channels would be transported in) can move in the forward (toward the axon) anterograde direction or the backward retrograde (toward the cell body) direction
  • This transport can move about 400mm a day
18
Q

Slow Axonal Transport

A

-Cytosolic and cytoskeletal proteins move only in the anterograde direction and are substantially slower (0.2-2.5mm per day

19
Q

How does the neuron differentiate what gets transported via fast or slow transport?

A
  • Proteins that need to be transported using fast axonal transport are:
    (1) sent to the Golgi body after being made in the rough ER and
    (2) packaged into vesicles when they leave the Golgi.
  • This process places modifiable chemical groups on the vesicle so that the vesicles can find the microtubules and be transported appropriately
20
Q

Myelin Differences in the CNS and PNS

A
  • The glial cells do not produce myelin, they are the myelin
  • The myelin is in fact just an extension of the oligodendrocyte/Schwann cell itself, meaning that every time you look at a neuron, you are seeing
    (1) the neuron and
    (2) the cell processes of another cell, the oligodendrocytes/Schwann cell
21
Q

CNS Myelin Differences

A
  • In the CNS, a single oligodendrocytes myelinates many neurons, so that each neuron has myelin from multiple oligodendrocytes
  • Astrocytes trigger the oligodendrocytes to myelinate
22
Q

PNS Myelin Differences

A
  • In the PNS, each segment of myelin is due to a different Schwan cell that is wrapping itself around the axon
  • Contact with the axon triggers the myelination process
23
Q

Astroctyes

A
  • incredibly important for neuronal function, with up to half of all brain cells being these
  • very close proximity to neuronal synapses and blood vessels within the brain
24
Q

Astrocytes are important for:

A
  1. Regulating the extracellular ion and neurotransmitter concentration
    a. take up excess ions that result from neuronal signaling, and can swell up as a result.
    b. In cases of head injury, part of the swelling in the brain
    is from astrocytes attempting to buffer excess ions
  2. Regulating the blood brain barrier
25
Q

Neurons differ in the CNS versus PNS broadly, and also neurons within the CNS/PNS differ amongst each other – why? PNS

A

The purpose of the PNS is to

(1) detect sensory stimuli from an array of systems (and provide motor output and
(2) convey that information to/from the CNS

26
Q

Neurons differ in the CNS versus PNS broadly, and also neurons within the CNS/PNS differ amongst each other – why? CNS

A

The purpose of the CNS is to

(1) receive information from the PNS and
(2) internally “process” that information to give you complex cognition

27
Q

The Stretch Reflex

A
  • is a basic neuronal circuit that allows for reflexive leg movement
  • Used by physicians to test for motor neuron function (i.e. motor neurons in the spinal cord or CNS)
28
Q

Two Basic Neuronal Types in the Stretch Reflex

A

1) a sensory neurons to detect the tap and

2) a motor neuron to cause the knee-jerk in response

29
Q

The Stretch Reflex: Sensory Neurons

A
  • has a large cell body located adjacent to the spinal cord, within the vertebral column.
  • has no dendrites, only one axon that bifurcates with the one going to the periphery and the other to spinal cord.
  • The function is to detect the stretch of the muscle tendon and signal that to the motor neuron
  • Does not need to integrate input from many sources at once, and instead has divergent input to as a many as 500-1000 motor neurons
30
Q

The Stretch Reflex: Motor Neurons

A
  • has its cell body within the spinal cord and sends its single axon to the muscle.
  • The cell body has many dendrites (up to a 100) and they can be up to 20x as long as the cell body
  • The function is to receive synaptic input from the sensory neuron and cause a muscle to contract
  • Integrates input from many sources at once (convergence), with as many as 100 sensory neurons needed to activate one single motor neuron
31
Q

Cortical Pyramidal Neurons

A
  • pyramidal shaped cell body and a singular axon.
  • dendrites are numerous and contain thousands of dendrites spines, which allow for a great capacity to form synapses.
  • The spines are just a continuation of the dendrite, and allow for more synapses in a finite space
  • This capacity is dynamic, and spines can be produced/removed based on experience.
32
Q

Properties of Ion Channels

A

1) The channels recognize and select certain positively charged particles (i.e. the ions)
2) The channels open and close to specific stimuli, whether it is mechanical, electrical, or chemical
3) Have a pore in the middle that allows the ions to flow in when the right stimulus is present, which in turn changes the neuronal excitability

33
Q

Why are Ion Channels are Needed?

A

-to provide a pore in the membrane that is not hydrophobic, so that the ions can enter/leave the cell

34
Q

How are Ion Channels Gated?

A
  • The ion channel can be (1) closed and ready to be activated, (2) open and currently allowing ions to flow, or (3) closed and refractory (termed ‘inactivated’)
  • Ions always move passively through the ion channels (passive diffusion based on concentration gradient, no energy required)
  • Ion channels open and close in very specific ways, which either allow ions to flow or block the pore. The gating of these channels is by the ion channel itself changing conformation in the lipid bilayer
35
Q

What are Ion Channels Made of?

A
  • Just like with neurons, the ion channels will be similar in function but have differences in their structure
  • Overall, all ion channels are made of membrane spanning proteins that form a pore in the middle
  • Ion channels will have certain sequences that confer ion selectivity, allow for detecting of excitability (in voltage-gated channels), or allow for neurotransmitter binding
36
Q

4 Key Types of Ion Channels

A

a. Voltage-gated ion channels
b. Ligand-gated ion channels
c. Mechanical-gated ion channels
d. Thermosensitive ion channels

37
Q

Voltage-Gated Ion Channels (VGIC)-Function

A

-These channels open in response to voltage changes, made possible by a voltage sensor
-The voltage sensor is just a string of amino acids that
are positively charged (in yellow on the right)
-There are VGICs for each of the major ions (Na+, K+, Ca2+ and Cl-)
-The different VGICs have different properties: changes in activation time, inactivation time, time course of opening/closing etc.
-Each VGIC also has a pore that allows the ion to flow through

38
Q

Ligand-Gated Ion Channels

A
  • These channels open in response to ligands (i.e. drugs, neurotransmitters)
  • While VGICs allow only 1 ion through, these channels are less selective
  • The purpose of these channels is to turn a chemical cue into a electrical signal
  • For example, a neurotransmitter binding will cause ions to flow, resulting in current and a change in the membrane potential (i.e. hyperpolarization or depolarization
39
Q

Mechanical and Thermosensitive Ion Channels

A
  • These channels open in response to pressure or temperature, respectively
  • These channels are important in the skin, as they allow you to feel touch, pressure, and temperature
40
Q

Ion Pumps

A
  • a second set of proteins that also allow ions to flow
  • use ATP to push ions against their concentration gradient, allowing the ions to get back to their original state (before the ion channel opened)
  • are selective for specific ions and are also found throughout the entire neuron
41
Q

Ion EXchangers

A

Ion exchangers also exist to restore the ions back, but instead use the energy of ions flowing passively to move a specific ion back

42
Q

YOU GOT THIS

A

STAY ON THAT GRIND😩😩😩😤😤😤🤫🤑🤑🤑💦💦💦💦

Fundamentals of Neuroscience (10 decks)

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