Neurophysiology Flashcards
3 Different types of Neurons are…
Sensory, Motor, and Interneurons
Sensory Neurons
Receive sensory information (light, sounds, etc) “Afferent neurons
Motor Neurons
Control the muscles, “efferent neurons”
Interneurons
Lie between sensory and motor neurons (found only within the brain and spinal cord), “afferent and efferent”
Soma
- Cell Body
- Contains all material needed for the life processes of the cell ( nucleus, mitochondria, etc)
Dendrites
serve to receive incoming signals from other neurons
Terminal Buttons
- site of neurotransmitter synthesis & release to other neurons
- communicates vis chemical means
Axon
- transmits signal to another neuron
- covered in myelin sheath
Multipolar neuron
neurons that have one axon and many dendrites
- most common neuron n the CNS
Bipolar neuron
neurons that have 1 axon and 1 dendrite, usually at opposite ends of the soma
- usually sensory neurons
- found in the visual, olfactory and auditory systems
Unipolar Neurons
Neurons that have 1 process that leaves the soma and then divides into 2 branches, one that receive information and the other transmits it
- cell body is separated
- associated with touch and pain
- usually sensory neurons
- found in the somatosensory system
Glia Cells (supporting Cells) are…
1) Astrocytes
2) Oligodendrocytes
3) Microglia
Astrocytes
- provides structural support and nutrients for neurons
- metabolizes sugars which allows them to provides energy for neurons
Oligodendrocytes
provide structural support and myelin to axons
Microglia
- recognize and remove foreign cells
- scavenge dead neurons
Myelin Sheath
- produced as oligodendrocyte wraps itself around the axon
- not continuous
Nodes of Ranvier
Gaps in the myelin sheath
Neuron resting membrane potential
- (-70mV) voltage
- the neurons interior is polar
- maintained by two forces
1) Force of Diffusion
2) Electrostatic Force
Force of Diffusion
between areas of different concentration; particles want to evenly distribute
Electrostatic Force
between charged particles; differently charged particles are attracted to each other
Membrane at Rest (Ions) location
K+ - more inside
Cl- - more outside
Na+ - more on outside
K+ feel more pressure from…
force of diffusion
Cl- feels more pressure from
force of diffusion
Na+ feels pressure from…
electrostatic force and force of diffusion
At rest voltage gated channels are…
innactive
At rest leaky channels are
slightly permeable
With the depolarization of neuron the membrane potential becomes
less negative
Decremental Potentials
short lived depolarizations
- as it spreads down the axon it gets weaker
Threshold of excitation
-60mV
Which channels open at -60mV
Sodium voltage gated channel opens
-Na+ is coming into the cell
Which channel opens at -45mV
Potassium voltage gated channels
- leaving the cell
Action potential
+40MV
- large depolarization
- membrane potential reverses itself
Which channel become refractory at action potential
sodium ion channels
What allows the membrane to re-polarize
- K+ channels staying open longer then Na+
- sodium/potassium pumps taking Na+ out of cell and K+ into cell
Action Potential obeys…
All or none law
- runs down entire length of axon
- does not decline in strength
Saltatory Conduction
The jumping of the AP from one Node of Ranvier to the next
At each node of ranvier …
The AP is regenerated
Why is the AP regenerated at each node?
There is a high density of sodium channels at each node
The two advantages of saltatory conduction
1) Na+/K+ pumps only have to work at the nodes, reduces energy
2) Decremental conduction under myelin is very fast
Refractory Na+ channels allow the AP…
to move in one direction
AP is conducted along the axon membrane to the…
axon terminals
Presynaptic Neuron
Neuron that send the signal
Postsynaptic Neuron
neuron that receives signal
At the axon terminal there are _____ that contain________
synaptic vesicles, neurotransmitters
Neurotransmitters
Chemical messengers released by the neuron
Neurotransmitters are released into the ____ and bind with ______
synapse, specialized receptors
Types of synapse
Axosomatic synapse Axodendritic synapse (most common)
Arrival of AP to axon terminal causes ___ to open
Opens Ca+ ion channels
Ca+ channels opening cause____ to move to release zone
synaptic vesicles
_____ binds to the presynaptic membrane to form a ____ shape to release _____
Synaptic vesicle; omega; neurotransmitters
NT interaction with receptors causes…..
change in membrane potential ( Transient Change )
EPSPS
Depolarize, make inside more negative, more likely to reach threshold
IPSPS
hyperpolarize, make inside more negative, less likely to reach threshold
EPSPS and IPSPS are ….
decremental conduction ( loose strength over time and distance)
if Na+ comes inside the neuron
EPSPS
if K+ leaves neuron
IPSPS
if Cl- enters neuron
IPSP
Excititory Connections
release of NT for presynaptic neuron to postsynaptic neuron makes it more likely to reach threshold
Inhibitory Connections
release of NT from presynaptic neuron to postsynaptic neuron makes it
less likely to reach threshold
Effects of neurotransmitters must be ____ quickly
terminated
Neurotransmitter reuptake
We remove NT from the synapse back to presynaptic terminal to be recycled
- requires transporter molecules
- most NT go through this
Enzyme degredation
Enzymes degrade NT into their smaller parts
When a neuron is sufficiently stimulated…
it will fires a volley of action potentials
Neural Integration
At the axon hillock if the sum of EPSPS and IPSPS are above the threshold an action potential will occur, if not, then no action potential
