Lecture 10 Flashcards
Why can’t action potentials move in 2 directions?
Due to the refractory period-propogation must travel away from the site of initial stimulation
What is myelination?
Oligodendrogliain CNS and Schwann Cells in PNS-speeds up neural impulses (200m/s).
What are the Nodes of Ranvier?
Tiny gaps in the myelin-use saltatory conduction to propagate the action potential at successive nodes of ranvier.
Why do action potentials remain the same size across the axon?
Because they are an all-or-none response.
What does myelination and the nodes of ranvier result in?
Faster electrical signal that doesn’t dissipate.
Is neural transmission instantaneous?
No. There is a finite amount of time between sense organs detecting phenomena and perception of the phenomena.
What is the excitatory post synaptic potential (EPSP)
Brief depolarization of a membrane in response to stimulation-more likely to produce an action potential.
What is the inhibitory post-synaptic potential (IPSP)
Brief hyperpolarization of a neuron in response to stimulation-less likely for an action potential.
What are the two ways that neurons integrate information?
Temporal summation and spatial summation
What is temporal summation?
Pulses that occur at approximately the same time on a membrane are summed.
What is spatial summation?
Pulses that occur at approximately the same location on a membrane are summed.
What is being summed in these 2 events?
EPSP- Influx of Na+ ions
IPSP- Efflux of K+ ions or influx of Cl- ions.
What is the initial segment?
Overlaps with the axon hillock, it is rich in voltage sensitive channels, and is where EPSPs and IPSPs are integrated and action potentials start.
What is back propogation?
Reverse movement of an action potential into the dendritic field-some neurons may have voltage gated channels on dendrites.
What do voltage gated channels on dendrites do?
, which may underlie some of the plastic changes in learning and memory-makes dendritic field refractory and reinforces signals coming into certain dendrites.
What are stretch sensitive receptors?
Ion channel on tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse-causes stretch sensitive membrane to open, allowing an influx of Na+.
What is an end-plate?
Receptor/ion complex that is activated by the release of the neurotransmitter acetylcholine: Action potential starts-produces contraction of muscle fibres.
How does sensory info get into the nervous system?
Sensory info is transmitted to the brain, info is processed and a decision to respond (pull away or not) is generated, muscle neurons generate action potentials to make muscles contract.
What is myasthenia gravis?
Autoimmune disease where the body attacks the end-plate receptors on muscles. By consequence, the receptors become less sensitive to Na+ and K+ ions.
How do we cure myasthenia gravis?
Surgery or pharmacological intervention-try to keep acetylcholine in the synapse for longer so it might activate something
What is the hard question of consciousness?
How is it that the movement of ions across a cell membrane translates to a rich perceptual experience of consciousness? (all you are is sodium and potassium moving around)
Who was Otto Loewi?
Won the nobel prize in physiology/medicine (1936)-discovery of chemical transmission of nerve impulses (using frog hearts)
How did Otto Loewi discover the chemical transmission of nerve impulses?
Stimulated a frog heart in water, which decreased beating. Took a second frog heart and allowed fluid transfer. Stimulating the first frog heart caused the same change in the second frog heart.
What was Otto Loewi’s conclusion?
There must be a chemical released by a nerve that is the basis for communication between neurons. Also discovered acetylcholine (inhibits heart rate and activates muscles) and epinephrine (speeds up heart rate, adrenaline).
What are neurotransmitters?
Chemicals released by a neuron onto a target with an excitatory or an inhibitory effect.
