Exam 2 Flashcards
What are the 2 primary ligands
Hormones , Neurotransmitters
Hormones are secreted by?
- endocrine glands
- can travel long distances
- considered metabotrophic
Neurotransmitters are secreted by?
axon terminal knobs into a synaptic cleft.
- considered ionotropic (directly)
- considered metabotropic if binding to a receptor results in changing its target cells metabolism (indirectlyO
Receptors can be found on?
Surface of the cell membrane or in the cytosol of a cell.
Ion channel linked receptors and G protein linked receptors or intracellular.
What are the 2 kinds of Surface receptors
- ion channel-linked receptors
- G protein-linked receptors
Where is leakage channels located?
located all over the surface of aneuron
Two main types of ion channels
- Leakage
- Gated channels
1. Ligand gated
(open with binding of a specific chemical )
2 . voltage gate
(open and close in response to changes in membrane potential)
Resting membrane potential?
-70mV
At what voltage does action potential get triggered
- 55mV
Sodium Na+ fuse down concentraiton gradient T/F
T
Which is more permeable? K+ channel or Na+?
K+ .
K+ diffuses out of cell down gradient
More K+ diffuses out than sodium diffuses in –> inside of cell is more negative
Graded potential moves __ distances
short
Depolarization ?
decrease in membrane potential
- inside of membrane becomes less negative than resting membrane potential.
Action potential moves ____ distance
long signals of axons
Hyperpolarization?
increase in membrane potential
- inside of membrane becomes more negative than resting membrane potential
Action potential only occurs in?
muscle cell and axons of nuerons
Which potential decays over distance?
Graded potential
What is saltatory conduction
Action potentials can only be generated at the Nodes of Ranvier
The action potential jumps from node to node
Because of saltatory conduction the speed of impulse transmission is much faster on myelinated process
(The synapse) : Electrical synapse?
when an action potential spreads from one cell to another through a gap junction
- associated with smooth and cardiac muscle
Chemical synapse?
- a junction between 2 neurons
- include the axon terminal of presynaptic neuron and the dendrite, cell body or axon hillock of post synaptic neuron
- neurotransmitter is released int othe synaptic cleft by terminal knobs
What is the process of chemical synapse?
Excitatory neurotransmitters?
cause depolarization of a postsynaptic neuron by opening chemically gated Na+ ion channels.
- ACH
- is the most common neurotransmitter in the whole body
- comes in both ionotropic and metabotropic - Glutamate
- is the most common neurotransmitter in the brain.
Inhibitory neurotransmitters
cause hyperpolarization of a postsynaptic neuron by opening chemically gated K+/Cl- ion channels.
- harder to reach threshold and initiate action potential
- GABA is the most common inhibitor in the brain.
GABA
- inhibitory
- most common n the brain
- opens chloride ion channels
-the brain relies heavily on inhibition through GABA to prevent too many stimuli - is enhanced by valium
Glycine
- inhibitory
- primary inhibitor in the spinal cord
spatial summation
when terminal knobs all contribute neurotransmitter to the same postsynaptic neuron
Chemically gated channles
Open in response to the binding of neurotransmitters
Depolarization is caused
when the neuron becomes more positve than resting potential
- Na+ influx
Hyperpolarization is cuased
when the neuron becomes more negative than resting potential
- K+ ions following out of the neuron or Cl- following into the neuron
The action potential is what voltage and occurs where
-55mV. occurs at the axon hillock.
Absolute refractory periods
begins when the action potential starts and ends when repolarization is well underway. during this time, another action potential CANNOT be generated because the sodium channels are either open or inactived/
Relative refractory period
until the membrane has returned to its resting state.
During this time, an action potential can be generated, but it requires a much stronger stimulus since many of the potassium channels are still open, and the cell is hyperpolairzed.
What is the neuron before the synapse called?
presynaptic neuron.
transmits signals toward the synapse.
What is the neuron after the synapse called?
Postsynaptic neuron
receives the signal transmitted across the synapse
Where is the neurotransmitter found
in synaptic vesciles within the axon terminal of the presynaptic neuron.
What type of ion channel is opened on the synaptic knob
When an action potential reaches the axon terminal, voltage-gated Ca2+ channels on the synaptic knob open, allowing the Ca2+ flow into the cell.
the influx of Ca2+ triggers the synaptic vesicles to fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft through exocytosis
What happens to the neurotransmitter after it binds to the receptor
After binding to receptors on the postsynaptic membrane, the neurotransmitter’s signal is terminated in one of three ways: 1. Reuptake: The neurotransmitter is taken back into the presynaptic neuron through reuptake pumps or transporters (e.g., serotonin reuptake). 2. Enzymatic Degradation: Enzymes in the synaptic cleft break down the neurotransmitter (e.g., acetylcholine is broken down by acetylcholinesterase). 3. Diffusion: The neurotransmitter diffuses away from the synaptic cleft into the surrounding areas.
Excitatory Neurotransmitters
promotes action potentials in the postsynaptic neuron.
Glutamate
Acetylcholine
How do they act to EXCITE the post-synaptic neuron?
excitatory neurotransmitters bind to receptros that open ion channels allowing positive ions to enter the postsynaptic neuron, leading to depolarization
How do they act to INHIBIT the post-synaptic neuron?
inhibitory neurotransmitters bind to receptors that open channels for negative ions (Cl-) to enter or for positive ions (K+) to leave, leading to hyperpolarization.
Acetylcholine role
ACH can be ionotropic (directly opens ion channels) or metabotropic.(acts through a G-protein signalling cascade)
Glutamate
The main excitatory neurotransmitter in the CNS.
it binds to ionotropic receptors to open NA+ and Ca2+
GABA ?
the main INHIBITORY neurotransmitter in the brain .
binds to A receptors which are ionotropic and opens CI- cahnnels, and B receptors which are metabotropic
Glycine?
INHIBITORY neurotransmitter, particularly in the spinal cord.
Which of the following ions enters the synaptic knob to trigger neurotransmitter release?
Calciums
What effect does an excitatory neurotransmitter typically have on the postsynaptic neuron?
C) Depolarizes the neuron
excitatory neurotransmitters usually depolarize the postsynaptic neuron, making it more likely to fire an action potential.)
Saltatory Conduction
refers to the way action potentials propagate along myelinated axons.
Unlike continuous conduction in unmyelinated axons, saltatory conduction allows the action potential to “jump” from one Node of Ranvier to the next.
Saltatory conduction makes the transmission of nerve signals more energy-efficient and faster
Acetylcholine (ACh)
primary neurotransmitter used by the parasympathetic nervous system, which is responsible for regulating the body’s “rest and digest” activities.
BOTH ionotropic and metabotropic
GABA A?
Ionotropic
GABA B
Metabotropic
GABA opens?
Cl- channels and hyperpolarize
neuron typically carries sensory information from the periphery to the central nervous system?
Pseudounipolar neurons
Which type of ion channel opens in response to a neurotransmitter binding to a receptor on the postsynaptic neuron
Chemically-gated ion channel
Cl-?
flow into the neuron during inhibitory synaptic transmission. This occurs when an inhibitory neurotransmitter like GABA binds to its receptor on the postsynaptic membrane.
Ca2+
flow into the presynaptic neuron at the axon terminal when an action potential arrives, and they are crucial for triggering the release of neurotransmitters into the synaptic cleft.
Temporal Summation
occurs when a single presynaptic neuron releases neurotransmitters rapidly over time
