L.6 Flashcards
What is a neuron
nerve cell that transmits electrical signals
What are the 3 basic structures of every neuron
- dendrite
- cell body
- axon
What is a neuron
nerve cell that transmits electrical signals throughout the body
What are the 3 basic structures of neurons
- dendrites
- cell body
- axon
What is the function of the dendrite
it receives electrical signals from other neurons
What is the function of the soma
contains genetic information + maintains cell functions
What is the function of the axon
it transmits the electrical signals to other neurons
What are the 3 neuron classifications
- unipolar
- bipolar
- multipolar
What are the features of unipolar neurons
- 1 process that is split into 2 branches
- 1 functions as the dendrites
- 1 functions as the axon
- “part of the same branch, just different sections”
Where are unipolar neurons generally found
sensory neurons in PNS (ex: dorsal root ganglion)
What are features of bipolar neurons
- 1 axon & 1 dendrite
Where are bipolar neurons generally found
sensory pathways (ex: retina of eye)
What are features of multipolar neurons
- 1 axon & multiple dendrites
Where are multipolar neurons generally found
motor pathways and interneurons in CNS
What is an interneuron
neurons which connects sensory and motor neurons within CNS
What is the function of interneurons
relays information between sensory inputs and motor outputs
What is a special feature of interneurons
they can reverse a signal (create an inhibitory signal to an excitatory one)
Why are pyramidal cells important neurons
- have long axons which allow for long-range communication
Why are Purkinje cells important neurons
- allows for massive synaptic input
- helps w/ precise control of motor movements
Why are dorsal root ganglions important cells
- allows fast sensory signal w/o having to through the cell body
What is myelin
an insulating layer around axons
what are the 2 main roles of myelin
- increases conduction speed
- protects and insulates neurons
How does myelin increase conduction speed
electrical impulse can jump between between Nodes of Ranvier via saltatory conduction
What is a chemical synapse
electrical signals are passed via neurotransmitters
What are ganglion cells
group of neuron cell bodies
Where are motor ganglion cells found
in the ANS
What is the function of motor ganglion cells
- relays signals from CNS to control & regulate muscle movement and involuntary activities
- part of sympathetic & parasympathetic system
What kind of neuron classification would motor ganglion cells tend to be
multipolar
What kind of neuron classification would sensory ganglion cells tend to be
unipolar
Where are sensory ganglion cells found
in the PNS
What is the function of sensory ganglion cells
transmits sensory information from the body to the CNS
Name 6 types of ganglion cells
- oligodendrocyte
- astrocyte
- microglia
- ependymal cell
- Schwann cell
- satellite cell
What is the role of oligodendrocyte
production of myelin sheath
What is the role of astrocyte
supporting neurons via maintaining blood-brain barrier
What is the role of microglia
it engulfs microbes (act’s as brain immune system)
What is the role of ependymal cells
produces and pushes CSF around
What is the role of Schwann cells
produces myelin for 1 axon
What is the role of satellite cells
support and protect neurons by maintaining and regulating the environment
What are electrical synapses
connections between neurons that allow the direct transmission of nerve impulses through the gap junctions
What are features of electrical synapses
- faster transmission
- bidirectional
- smaller gap
- no plasticity
- no amplification
What does no amplification mean in electrical synapses
- post-synaptic response is directly proportional to pre-synaptic input
- 1st neuron sends weak signal = 2nd neuron gets weak signal
What does no plasticity mean in electrical synapses
they can’t strengthen or weaken over time (based on activity/experience)
What is temporal summation
when one neuron sends multiple signals quickly, one after the other
What is spatial summation
many different neurons send signals to the same neuron at the same time
What are the 4 main stages of action potential generation
- resting period
- depolarisation
- repolarisation
- refractory period
Outline the resting period
- no neuron firing
- -70mV
- Na+/K+ pump moves 3Na+ in and 2K+ out
- membrane more permeable to K+ (inwards rectifier)
Outline the depolarisation period
- inside the cell becomes more positive
- influx of Na+
- +30mV
Outline the repolarisation period
- inside the cell becomes more negative
- K+ leave
explain the 2 delayed action events during repolarisation
- Na+ channel inactivation isn’t instataneous (lags slightly behind depolarisation – it overlaps with the opening of K+ channels)
- K+ channels open slower than Na+ channels (they open when Na+ channels are closed)
What is hyperpolarisation
K+ channels stay open for longer (more negative than usual – delay)
Outline the refractory period
- amount of time before a neuron is ready to start an action potential
What does the “all or none” principle mean
- a neuron either fires an action potential or it doesn’t fire at all
- response of neuron is the same not matter the size of stimulus (always maximum response)
How do neurons code the intensity of an input
- firing frequency
- neuron type
How does firing frequency tell you the intensity of the input
- stronger stimulus = higher firing frequency
- weaker stimulus = lower firing frequency
How does the neuron type tell you the intensity of the input
- low threshold neurons = respond to weak stimuli (touch receptors)
- high threshold neurons = respond to strong stimuli (pain receptors)
What is excitability
how easy it is to generate an action potential
How to increase the firing rate
- increased receptor activation (more frequent stimuli)
- increased neuronal excitability (lower threshold)
What are the dangers of over-excitability
- lead to seizures and muscle spasms because threshold has become too low
What is the effect of Lidocaine on excitability
- blocks sodium ion channels
- raises threshold –> lower excitability –> stops APs locally
- acts as local anesthetic
What is the effect of Carbamazepine on excitability
- inactivates sodium channels
- raises threshold
- lowers excitability
- may prevent seizures
What is the effect of Carbamezepine on body
may prevent seizures
What are the 3 different conformation states channels can have
- close: can’t conduct but can open if stimulated
- open: can conduct
- inactivated: close and cannot reopen immediately
What are the 2 forces that act on each ion
- chemical
- electrical
What is chemical force
ions are driven by diffusion
What is electrical force
ions move towards areas of opposite charge
What are graded potentials
- changes in the membrane potential that vary size depending on the stimulus
- don’t follow the all-or-none principle
What are features of graded potentials
- last longer
- flatter shape
- conducted instantly but decreased in strength with distance from stimulus
When is conduction fastest
myelinated & larger diameter (lower resistance) of neurons
