lec 10 neurons Flashcards
What is the path that communications take thru the neuron?
Info received at dendrites –> soma along axon(myelin quickens)–>terminal buttons–>dendrites of other cells at meeting points (synapses)
what are the 2 major types of cells that comprise the nervous system?
Neurons, glial cells (glia)
what is the function of neurons? are the easily replaceable?
receive, integrate + transmit info
less able than other cells to replace themselves
what are the features of a neuron?
stoma with nucleus
dendrites
axon and myelin sheath
terminal branches
what is the function of a glial cell? how often are they replacing themselves?
support + nourishment to neurons, remove waste, insulate axons
constantly replacing themselves
what do glial cells play a role in?
thinking, learning + memory
what are the 5 parts of a neuron?
Cell body
Dendrites
Axon
Myelin Sheath
Terminal branches of axon
What is the function of each part of a neuron?
Cell body- support center
Dendrites- receive messages from other cells
Axon-passes info
Myelin Sheath- insulation, protection, speeds transmission
Terminal branches of axon- form junctions with other cells
What is the function of the myelin sheath?
-insulation layer for axon
-protects from unwanted messages from other cells
-speeds up transmission
What increases during myelination?
-neural efficiency
-judgement
-self control
What are the areas where myelin is thin/absent called? What is the purpose?
Nodes of Ranvier, allow ions to diffuse in/out of neuron
What happens if the myelin sheath degrades?
-results in multiple sclerosis
-communication to muscles slowed
-eventual loss of muscle control and sometimes sensation
how do neurons transmit signals?
electrochemically
-neurons generate electricity from chemical events
what are the 2 types of signals a neuron receives?
excitatory(‘the gas’)
inhibitory (‘the brake’)
from many other neurons
what is an action potential?
when excitatory signals minus inhibitory signals exceed minimum threshold, neuron fires
What causes positive sodium ions to flow into neuron
stimulation (axon firing) causes membrane to open, allowing them to flow in
What is resting potential?
the positive/negative state between a neuron outside neuron
neurons ‘at rest’ = negative charge
fluid inside+outside of neuron contain electrically charged ions
What is depolarization? What does it influence?
shift from negative to positive voltage in a neuron
influences next section of axon, causing its channels to open
What is the refractory period?
sodium channels close, positive potassium ions pumped out of cell
allows cells negative resting potential to be restored
what is the all or none response with respect to action potential?
-neuron either fires, or doesn’t
-increasing level of stimulation above threshold will NOT increase intensity of impulse
-intensity of action potential same thruout length of axon
How is intensity of a stimulus detected?
strong stimulus causes MORE neurons to fire and fire more OFTEN
what is the synapse? where are 3 places connections can occur?
junction b/w terminal button on end of axon from one neuron (pre-synaptic) and either:
- dendrite of another neuron (post synaptic)
- membrane of a muscle fiber
- a gland
what is the synaptic cleft?
gap b/w terminal button of pre-synaptic neuron and cell membrane of post synaptic neuron
what are neurotransmitters responsible for?
transmitting info from one neuron to another thru synaptic gap
where do neurotransmitters bind on post-synaptic cell
after diffusing across synaptic cleft, bind to receptor sites
What is important about neurotransmitters binding to receptor sites? What kind of mechanism is it?
each neurotransmitter will bind to specific receptor site
lock and key mechanism
what happens to excess neurotransmitters left in synaptic cleft?
either…
1. drift away
2. broken down by enzymes
3. re-absorbed by pre-synaptic neuron, used to produce more later (reuptake)
what are neurotransmitters? function?
chemical messengers released by terminal buttons of one neuron so it can communicate with other neurons thru synaptic cleft
each has specific function, sometimes many
What does Acetylcholine (ACh) play a role in? What happens if there isn’t enough?
-voluntary muscle activity
inadequate ACh results in type of memory loss seen in Alzheimer’s
What is the role of serotonin?
-mood, sleep, temperature
too little: depression
how does Mylin speed up the transmission of signals?
sodium channels are only open on Nodes of Ranvier
charge essentially ‘skips’ b/c all sodium channels don’t need to open, only on NOR
what are the 2 signals neurotransmitters can give to a receiving cell?
inhibitory or excitatory
What is the role of epinephrine?
increases heart rate and blood pressure as part of fight or flight response
