exam 4 Flashcards
what happens within the nervous system
impulses are transmitted along the specialized plasma membranes of nerve cells
central nervous system (CNS)
includes the brain and spinal cord
peripheral nervous system (PNS)
includes other sensory and motor components like: cranial nerves, neuromuscular junctions, spinal nerves
what are the 2 types of nervous system cells?
nerurons and glial cells
neurons
cells within the nervous system that send and receive electrical impulses
glial cells
variety of cell types and are abundant in the central nervous system
what are the types of neurons
sensory neurons, motor neurons, and interneurons
sensory neurons
are diverse cells specialized for stimuli detection
motor neurons
transmit signals from the central nervous system to muscles and glands to make synaptic connections
interneurons
process signals and transmit information between parts of the nervous system
what are the types of glial cells
microglia, oligodendrites, schwann cells, and astrocytes
microglia
fight infections and remove debris
oligodendrites + schwann cells
form insulating myelin sheath around neurons of the CNS and PNS
astrocytes
control access to blood borne components into extracellular fluid around nerve cells.
myelin sheath
protective membrane that surrounds CNS and PNS cells
processes that receive signals
dendrites
processes that conduct signals
axons
nerve
tissue composed of bundles of axons
fundamental property of all cells
membrane potential
synapse
the point of contact between a nerve cell, gland, or muscle cell.
where do synapses usually occur
between axon-dendrite, dendrite-dendrite, or axon-axon
what is the property of a cell at rest
negative charge outside the cell and positive inside the cell
potassium ion gradient
uneven distribution of potassium ions in and outside the cell
electroneutrality
ions are present in solutions in pairs, one negative-one positive
counter ion
oppositely charged ion in the solution
electrical potential
charges are separated so that one part has more positive charges and another has more negative
current
movement of ions
whats another name for electrical potential
voltage
how is current measured
in amperes (A)
action potential
stimuli trigger a rapid set of changes in membrane potential
what salts are within extracellular fluid
Na+ and Cl-
what macromolecules are within cytosol
proteins and RNA
Ion channels
form ion conducting pores through a lipid bilayer
leak channel
type of ion channel thats always open
potassium leak channel
K+ ions leak out of cell, more anions without counterions resulting in negative resting potential
Na+/K+ Pump
continuously pumps Na+ ions out of cell and K+ ions into cell
how many Na+ and K+ ions are moved in/out of cell
3 Na+ out, 2 K+ in
electrical equilibrium
when a chemical gradient is balanced with electrical potential
nernst equation
mathematical relationship between ion gradient and equilibrium potential
what happens when K+ diffuses out of the cell
membrane potential becomes more negative
what happens when Na+ goes into the cell
the membrane potential becomes more positive, polarizing
what happens when Cl- diffuses into the cell
its repelled by the negative potential, and enters with positive ions
what happens if the membrane is permeable to K+
the membrane potential will be equal to K+ equilibrium potential
what happens when the membrane is permeable to Na+
the membrane will be partly depolarized
patch clamping
modern technology thats used to record the ion currents passing through channels
optogenetics
genetic engineered channel proteins, and ion concentrations thats manipulated by light
bacteriorhodopsin
used to suppress neurons
channelrhodopsins
used to activate neurons
whats the function of voltage gated ion channels
respond to voltage channels across the membrane
voltage gated Na+/ K+ channels are
responsible for action potential
what do ligand gated ion channels do
open when a certain molecule binds to it
what types of voltage gated ion channels are there
voltage gated potassium channels and voltage gated sodium channels
how is channel specifity determined
by the size of the central pore and how it interactions with an ion
what is channel gating
channels opening rapidly to stimuli then closing
what is channel inactivation
voltage gated channels adopting a second closed state
what happens during channel inactivation
voltage gated channels can’t reopen immediately even when stimulated
describe a resting neuron
closed voltage gated channels. 100x more permeable to K+
subthreshold depolarizations
depolarizations too small to initiate action potential
steps to the depolarization stage
-membrane is depolarized past the threshold potential then Na+ channels activate
-membrane potential shoots upward fast
-the peak is +40mV
steps to repolarization stage
-when peaked the membrane repolarizes
-inactivated Na+ channels stay closed while membrane potential turns negative.
-Cell repolarizes until K+ leaves
Hyperpolarization stages
-membrane potential drops below resting potential when K+ increases.
-when K+ voltage gated channels close the membrane potential returns to normal
what is the refractory period
a few milliseconds after action potential when another cant be triggered
absolute refractory period
sodium channels are inactivated and cant open via depolarization
relative refractory period
when the membrane potential is below threshold of another action potential
what is myelination
the process where axons are coated with myelin, a fatty sheath that insulates and protects nerve fibers.
whats the role of myelination
Myelin increases the speed and efficiency of electrical signal transmission along the axon.
saltatory propagation
action potentials jump from one node to the next
electrical synapse
one neuron (presynaptic) is connected to another neuron (postsynaptic) via gap junctions
what are gap junctions
specialized intercellular connections that allow direct communication between nearby cells
how do ions move between cells and why is it efficient
through junctions as it allows no delays in transmission
presynaptic neuron
sends a signal to another cell at synapse
postsynaptic neuron
receives the signal at synapse
chemical synapse
presynaptic and postsynaptic neurons are separated by a small space called the synaptic cleft
neurotransmitters
chemical messengers that transmit signals across a synapse from one neuron to another
How Do Neurotransmitters Work?
- Released from the presynaptic neuron into the synaptic cleft.
-Bind to receptors on the postsynaptic cell.
-Trigger excitatory or inhibitory effects depending on the receptor type.
Types of Neurotransmitters
Excitatory
Inhibitory
Modulatory
Excitatory
Increase the likelihood of an action potential (e.g., glutamate).
inhibitory
Decrease the likelihood of an action potential
Modulatory
Regulate broader neural circuits
what is the criteria to be considered a neurotransmitter
occur naturally, be released during presynaptic stimulation, induce the correct response when induced to the synaptic cleft
what is the most common neurotransmitter in vertebrates and is it excitatory or inhibitory?
acetylcholine and excitatory
cholinergic synapses
synapses that use acetylcholine as their neurotransmitter
catecholamines
group of neurotransmitters and hormones derived from the amino acid tyrosine
adrenergic synapses
synapses that use catecholamines as neurotransmitters
glutamatergic neurons
neurons that use glutamate as their neuro transmitter
neuropeptides
small protein-like molecules that act as neurotransmitters
endocannabinoids
lipid-based neurotransmitters that regulate a variety of physiological processes
Steps in Neurotransmitter Secretion
-electrical signal reaches the presynaptic terminal
-Voltage-gated calcium channels open, allowing calcium ions to enter.
-Synaptic vesicles containing neurotransmitters fuse with the presynaptic membrane.
-Neurotransmitters are released into the synaptic cleft.
-Neurotransmitters bind to receptors on the postsynaptic cell, initiating a response.
Role of Calcium in Secretion
Calcium ions trigger vesicle fusion with the membrane by interacting with proteins like SNARE complex
active zone
region of the presynaptic membrane where synaptic vesicles dock, fuse, and release neurotransmitters
neurotoxins
chemical agents that disrupt normal function in the nervous system by damaging neurons or interfering with neurotransmission
Compensatory endocytosis
maintains the size of the nerve terminal by recycling membranes
kiss and run exocytosis
a vesicle will temporarily fuse with the membrane, release neurotransmitters, then reseal
what is endocytosis
cells take in substances from the outside environment by engulfing them with their cell membrane, forming a vesicle.
exocytosis
cells expel substances from inside the cell to the outside environment by fusing vesicles with the plasma membrane.
antagonist
bind to receptors and inhibit their activity
agonist
bind to the receptor and activates it
whats the function of the GAB A receptor
when GAB A binds to a receptor the ligand gated channel releases Cl- ions into the cell, inducing hyperpolarization, decreasing the chances of action potential
NMDA receptor
glutamate receptor and ion channel that plays a central role in synaptic plasticity, learning, and memory
acetylcholinesterase
enzyme that breaks down acetylcholine into acetic acid and choline
neurotransmitter reuptake
neurotransmitters are pumped back into the presynaptic neuron after they have been released
postsynaptic potentials
changes in membrane potential due to neurotransmitter binding
types of postsynaptic potentials (PSP)
excitatory postsynaptic potential, inhibitory postsynaptic potential
excitatory postsynaptic potential
depolarizes the membrane making firing more likely
inhibitory postsynaptic potential
hyperpolarizes the membrane making firing less likely
temporal summation
multiple postsynaptic potentials (PSPs) from the same presynaptic neuron add together over time, leading to a stronger overall signal
spatial summation
multiple postsynaptic potentials (PSPs) from different presynaptic neurons are added together at the same time, resulting in a stronger overall signal
