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MBB1 > Neurons, glia and neuron communication: L2 > Flashcards

Neurons, glia and neuron communication: L2 Flashcards

1
Q

define Multiple sclerosis (MS)

A
  1. starts: visual problems, weakness of limbs
  2. leads to: paraplegia - slurred speech, problems with vision and eye movements
  3. neurological disorder attacks the insulating sheath called myelin that surrounds the axons of neurons
  4. appears late 20s/30s, more common in females
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2
Q

withdrawal reflex

A
  1. dendrites of a sensory neuron respond to noxious stimulus in the environment
  2. signal sent along axon to terminal buttons
    - > synaptic connections = excitatory effects
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3
Q

terminal buttons do what

A
  • release a neurotransmitter into synapse

- excites an interneuron which is in the spinal cord

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4
Q

role of inhibition

A
  • neuron excites an inhibitory interneuron which releases an inhibitory neurotransmitter
  • decreases activity of motor neuron, blocking withdrawal reflex
  • > principles of neural communication
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5
Q

define the neuron

A
  1. basic information-processing and receiving unit

2. separated by gaps called synapses across which chemicals called neurotransmitters pass

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6
Q

define:
1. cell body
2. dendrites
3. axon
4. action potential
5. terminal button

A
  1. cell maintenance
  2. allow neurons to communicate with one another (tree-like branches) - receive information from other neurons
  3. carries signals from cell body. signal carried is action potential
  4. wave of electrical potential travels down the axon to terminal buttons
  5. small knobs at the ends of axons. secrete chemical called neurotransmitter. either excite or inhibit subsequent neuron
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7
Q

Inside the cell body: define

  1. cytoplasm
  2. mitochondria
A
  1. jelly-like substance in the cell

2. use glucose to produce energy. produce chemical adenosine triphosphate (ATP) used as an energy source

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8
Q

Nucleus contains?

A
  • Chromosomes composed of deoxyribonucleic acid (DNA)
  • the genes making up the chromosomes provide recipes to make proteins
  • proteins build cell structure and form enzymes that create & break down molecules
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9
Q

Define Glial cells (different types)

  1. astrocytes
  2. oligodendrocytes
  3. microglia
  4. schwann cells
A
  • > provide physical support for neurons supplying oxygen and nutrients
    1. physical support, maintain chemical composition of extracellular fluid. clean debris from dead neurons = phagocytosis (in the CNS)
    2. provide insulating myelin sheath - prevents unwanted cross-talk from neighbouring axons
    3. act as phagocytes. attack invading micro-organisms. inflammation after brain damage
    4. same as oligodendrocytes but perform in peripheral nervous system (PNS)
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10
Q
  1. uncoated gap between axon is called

2. segments of myelin sheath are how many mm long

A
  1. nodes of ranvier

2. 1mm

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11
Q

Communication within a neuron

  1. cell membrane of neuron is composed of
  2. purpose of cell membrane
  3. critical for
A
  1. double layer of lipid (fat) molecules, containing complex protein molecules that regulate entrance and exit of chemicals from the neuron
  2. keeps fluid outside cell (extracellular fluid) separated from inside (intracellular fluid)
  3. transmission of information along the axon
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12
Q

resting membrane potential

  1. what is it
  2. micro electrode mm diameter
  3. micro electrode measures
  4. inside of axon is
  5. resting membrane potential is
A
  1. electrical process involving movement across the axon membrane of ions (electrically charged molecules)
  2. 1/1000th of mm
  3. difference in electric potential between intracellular and extracellular fluid
  4. more negatively charged
  5. -70 millivolts
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13
Q

Depolarisation by injecting current

  1. define
  2. adding positive electrical current inside neuron =
  3. depolarisation of the membrane potential of an axon is called
A
  1. disturb RP of neuron by passing current into it
  2. depolarisation
  3. action potential = message transmitted down an axon from cell body to terminal buttons
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14
Q

Natural axon potential

  1. diffusion
  2. electrostatic pressure
  3. 2 types of ions (charged particles)
A
  1. movement of molecules from high concentration to regions of low concentration
  2. force of combination of molecules of opposing electrical charges
  3. anion - negatively charged
    cation - positively charged
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15
Q
  1. ions that have the same charge
  2. ion that have the opposite charge
  3. force created by the combination of repulsion and attraction is called
A
  1. repel
  2. attract
  3. electrostatic pressure
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16
Q

ion movement across the axon membrane

  1. 4 ions crucial to resting membrane potential
  2. where are they found
  3. which is higher concentration outside
  4. NA+
A
  1. sodium (NA+), Chloride (CL-), Potassium (K+), organic anions (A-)
  2. all inside & outside of cell, except A- which is inside only
  3. NA+ & CL- (outside of cell = salt water NaCl)
  4. diffusion and electrostatic pressure move sodium ions in the same direction
17
Q

Sodium-potassium transporters

  1. what is the sodium potassium pump
  2. what does it consist of
  3. sodium-potassium transporters present in neurons and glia consume how much of the neurons metabolic resources
A
  1. pushes excess NA+ out of the cell
  2. sodium-potassium transporters, use energy provided by the cell’s mitochondria to drive out sodium Na+ in exchange for potassium K+, ratio 3:2
  3. 40%
18
Q

AP = ion exchange across the axon

  1. what causes an action potential to occur
  2. ion channels?
A
  1. rush of NA+ ions into the cell = increase the concentration of positively charged ions changing the membrane potential
    -> this change in membrane permeability causes an action potential
  2. provide an opening through which ions can rapidly enter or leave the cell
    NA + channel opens -> NA + rushes in
    K+ channel opens -> K+ rushes out
19
Q

AP - change in membrane potential over time.

sequence of events (4)

A
  1. threshold of excitation reached -> NA+ channels open -> rapid influx of positively charged ions -> membrane potential changes from -70 to +40 (depolarisation)
  2. > 1 ms after K+ channels open -> charged ions leave axon (repolarisation)
  3. at the peak of AP (1ms) NA+ channels close & cannot reopen until membrane reaches its resting potential (-70) again = refractory period
  4. K+ move out of the axon -> membrane overshoots its resting value (goes below -70) = hyperpolaraisation before returning to resting level
20
Q

AP movement along the axon

  1. triggered when
  2. signal is passed
A
  1. excitatory input is passes from the terminal buttons of the presynaptic neuron & received by the dendrites of the postsynaptic neuron
  2. passively, postsynaptic neuron stimulates depolarisation of the membrane if it is above the threshold of excitement
21
Q

Saltatory conduction of the AP

  1. how APs travel down axon
  2. this can only occur when
  3. strength of the electrical potential?
  4. advantages of jumping AP
A
  1. jump into the nodes of ranvier (gaps) between the segments of myelin
  2. the axon membrane is in direct contact with the extracellular fluid
  3. decreases as it moves along myelinated portions of the axon
    • saves energy
      - increases speed of neural signalling (speed of reacting/thinking)
22
Q

All-or-none law of the AP

A
  • AP occurs or it doesn’t
  • must meet threshold to occur
  • once triggered, an AP remains at the same amplitude (same level of depolarisation reached by membrane) & travels down the axon to the end
23
Q

Rate law of the AP

  1. how is variable information signalled
  2. the basic unit of information carried by axons is their rate of firing known as
A
  1. number the number of action potentials produced by a neuron (i.e. rate of firing)
  2. rate law
24
Q

effects of myelin damage in multiple sclerosis (MS)

->MS cure?

A
  • disruption of the normal process of transmission of the action potential along the axon
  • the saltatory conduction between the nodes of ranvier is disrupted
  • > no, only a drug called interferon B modules the responsiveness of the immune system & reduces severity of attacks
25
Q
  1. Astrocytes
  2. Schwan cells
  3. Microglia
  4. oligodendrocytes
A
  1. clean waste in neuron
  2. prevent unwanted communication in the PNS
  3. immune system of the neuron
  4. prevent unwanted communication in the CNS

MBB1 (7 decks)

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