Neurons, glia and neuron communication: L2 Flashcards
1
Q
define Multiple sclerosis (MS)
A
- starts: visual problems, weakness of limbs
- leads to: paraplegia - slurred speech, problems with vision and eye movements
- neurological disorder attacks the insulating sheath called myelin that surrounds the axons of neurons
- appears late 20s/30s, more common in females
2
Q
withdrawal reflex
A
- dendrites of a sensory neuron respond to noxious stimulus in the environment
- signal sent along axon to terminal buttons
- > synaptic connections = excitatory effects
3
Q
terminal buttons do what
A
- release a neurotransmitter into synapse
- excites an interneuron which is in the spinal cord
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
5
Q
define the neuron
A
- basic information-processing and receiving unit
2. separated by gaps called synapses across which chemicals called neurotransmitters pass
6
Q
define:
1. cell body
2. dendrites
3. axon
4. action potential
5. terminal button
A
- cell maintenance
- allow neurons to communicate with one another (tree-like branches) - receive information from other neurons
- carries signals from cell body. signal carried is action potential
- wave of electrical potential travels down the axon to terminal buttons
- small knobs at the ends of axons. secrete chemical called neurotransmitter. either excite or inhibit subsequent neuron
7
Q
Inside the cell body: define
- cytoplasm
- mitochondria
A
- jelly-like substance in the cell
2. use glucose to produce energy. produce chemical adenosine triphosphate (ATP) used as an energy source
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
9
Q
Define Glial cells (different types)
- astrocytes
- oligodendrocytes
- microglia
- 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)
10
Q
- uncoated gap between axon is called
2. segments of myelin sheath are how many mm long
A
- nodes of ranvier
2. 1mm
11
Q
Communication within a neuron
- cell membrane of neuron is composed of
- purpose of cell membrane
- critical for
A
- double layer of lipid (fat) molecules, containing complex protein molecules that regulate entrance and exit of chemicals from the neuron
- keeps fluid outside cell (extracellular fluid) separated from inside (intracellular fluid)
- transmission of information along the axon
12
Q
resting membrane potential
- what is it
- micro electrode mm diameter
- micro electrode measures
- inside of axon is
- resting membrane potential is
A
- electrical process involving movement across the axon membrane of ions (electrically charged molecules)
- 1/1000th of mm
- difference in electric potential between intracellular and extracellular fluid
- more negatively charged
- -70 millivolts
13
Q
Depolarisation by injecting current
- define
- adding positive electrical current inside neuron =
- depolarisation of the membrane potential of an axon is called
A
- disturb RP of neuron by passing current into it
- depolarisation
- action potential = message transmitted down an axon from cell body to terminal buttons
14
Q
Natural axon potential
- diffusion
- electrostatic pressure
- 2 types of ions (charged particles)
A
- movement of molecules from high concentration to regions of low concentration
- force of combination of molecules of opposing electrical charges
- anion - negatively charged
cation - positively charged
15
Q
- ions that have the same charge
- ion that have the opposite charge
- force created by the combination of repulsion and attraction is called
A
- repel
- attract
- electrostatic pressure
16
Q
ion movement across the axon membrane
- 4 ions crucial to resting membrane potential
- where are they found
- which is higher concentration outside
- NA+
A
- sodium (NA+), Chloride (CL-), Potassium (K+), organic anions (A-)
- all inside & outside of cell, except A- which is inside only
- NA+ & CL- (outside of cell = salt water NaCl)
- diffusion and electrostatic pressure move sodium ions in the same direction
17
Q
Sodium-potassium transporters
- what is the sodium potassium pump
- what does it consist of
- sodium-potassium transporters present in neurons and glia consume how much of the neurons metabolic resources
A
- pushes excess NA+ out of the cell
- sodium-potassium transporters, use energy provided by the cell’s mitochondria to drive out sodium Na+ in exchange for potassium K+, ratio 3:2
- 40%
18
Q
AP = ion exchange across the axon
- what causes an action potential to occur
- ion channels?
A
- 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 - 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
- threshold of excitation reached -> NA+ channels open -> rapid influx of positively charged ions -> membrane potential changes from -70 to +40 (depolarisation)
- > 1 ms after K+ channels open -> charged ions leave axon (repolarisation)
- at the peak of AP (1ms) NA+ channels close & cannot reopen until membrane reaches its resting potential (-70) again = refractory period
- 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
- triggered when
- signal is passed
A
- excitatory input is passes from the terminal buttons of the presynaptic neuron & received by the dendrites of the postsynaptic neuron
- passively, postsynaptic neuron stimulates depolarisation of the membrane if it is above the threshold of excitement
21
Q
Saltatory conduction of the AP
- how APs travel down axon
- this can only occur when
- strength of the electrical potential?
- advantages of jumping AP
A
- jump into the nodes of ranvier (gaps) between the segments of myelin
- the axon membrane is in direct contact with the extracellular fluid
- decreases as it moves along myelinated portions of the axon
- saves energy
- increases speed of neural signalling (speed of reacting/thinking)
- saves energy
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
- how is variable information signalled
- the basic unit of information carried by axons is their rate of firing known as
A
- number the number of action potentials produced by a neuron (i.e. rate of firing)
- 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
- Astrocytes
- Schwan cells
- Microglia
- oligodendrocytes
A
- clean waste in neuron
- prevent unwanted communication in the PNS
- immune system of the neuron
- prevent unwanted communication in the CNS
