L6 (pt.2) Flashcards
Graded potentials
A small change in membrane potential (depolarizing or hyperpolarizing)
Where do graded potentials (gp) occur?
Sensory receptors ➡️ receptor potential
Cell bodies/ dendrites ➡️ graded potential
Epsp-Ipsp cancellation
Excitatory and inhibitory graded potentials cancel each other out
Spatial summation
Excitatory potentials from many neurons trigger threshold potential
Temporal summation
Many excitatory potentials from one neuron triggers threshold potential
What are the two ways to reach threshold potential?
Temporal threshold ➡️ one neuron creates many graded potentials
Spatial summation ➡️ many neurons create graded potentials
What are graded potentials used for?
- Initiates information flow in sensory neurons
- Conducts information from cell bodies/ dendrites to initial segment of axon
- Initiate action potentials in cardiac muscle
What are properties of graded potentials?
- Depolarizes (epsp) or hyperpolarize (Ipsp)
- Amplitude modulate
- Amplitude delays w/ distance
- Can be summed ➡️ temporal or spatial
- Inhibited by synaptic transmission
Synaptic transmittion
Conduction across a synapse (leading to graded potential)
Synapse
Region of communication between two neurons
What are the two types of synapses?
Electrical and chemical
Electrical synapses function is to
Rapidly synchronize electrical events
- ions pass through gap junctions b/w cells
Chemical synapses function is to
Turn post synaptic neurons on/off by creating Epsp & Ipsp
- uses ligand gated ion channels
What are the 2 mechanisms for opening ion channel receptors?
Ligand- gated receptor & G protein receptors
Explain the mechanism for neurotransmitter release
- Action potential reaches axon terminal
- Voltage gated ca2+ channels open ➡️ca2+ diffuses down concentration gradient into cell
- Ca2+ binds to receptor protein (synaptotagmin) in cytoplasm
- Ca2+ protein complex stimulates fusion/ exocytosis of neurotransmitter
Nicotinic acetylcholine (ach) receptor is an example of what?
Ligand gated channel
What are the two types of acetylcholine (Ach) receptor?
Nicotinic = Epsp
Muscarinic = Ipsp
Where are ligand gated channel receptors found?
Post synaptic neuron membrane
What three components are found in the plasma membrane of a G protein receptor?
G protein, effector, receptor
Explain the process of a G protein using Ach as an example
- Ach binds to receptor
- G protein subunits dissociates ( alpha- beta - gamma)
- G protein binds to k+ channel, causing it to open
Where are g Proteins found?
At the post synaptic neuron membrane
How do you deactivate neurotransmitters?
By degrading ( destroying them/ breaking them apart)
Or reuptake
The production of Ipsp/Epsp depends on the ________ of ion channels
Nature
Neurotoxins
Disrupts normal signaling b/w neurons and muscles
What are so,e effects of neurotoxins?
- they block channels & allow for no breakdown
Neural pathways is defines as
Series of communicating neurons
What are the four neural Pathways?
- simple reflex arc
- complex reflex arc
- sensory pathways
- motor pathways
What is a simple reflex arc, and give an example
A series of communicating neurons
Ex. Pain reflex
Distinguish between a reflex and a reflex arc
Reflex = automatic, involuntary response to stimulus
Reflex arc = neural pathway
What is an example of a complex reflex arc
Crossed reflex arc
- Flexor contracts due to synapse of Epsp & extensor relaxes drawing foot away — Ipsp
- IN OTHER LEG - extensor contracts & flexor relaxes to support weight
What are sensory pathways and what are involved in Order to reach Ap consciousness?
Ascending tracts - arrive to the brain
- 1 sensory neuron and 2 interneurons
What are motor pathways and what are involved in order to reach Ap consciousness?
Descending tracts - deliver stimulus from brain ➡️ muscle/ gland
- 1 motor neuron and 1 interneuron
What factors contribute to neural complexity?
- Convergence & divergence
- Summation ( time and space)
- Synapses ( Epsp & Ipsp)
The difference between covergence and divergence?
Covergence = many cells include 1 cell
Divergence = 1 cell influences many cells
