Synapses, NTs, Circuity Flashcards
The purpose of the nervous system
Communication
Brain—>Target Organ—->Response——>Feedback—–>Brain Etc.
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In order to preserve communication, a message must propagate along each cell (A.P.) and between each cell (synapse)
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Nerve Cell—->Nerve cell—-> Nerve cell——> Target Organ
Na+ Channels do what to the cell membrane?
K+ channels do what to the cell membrane?
Depolarization
Repolarization and hyperpolarization
Propation in unmyelinated cell
Na and K channels open and close sequentially along the membrane, voltage gated channels located across entire membrane
Continuous Conduction
Propagation of action potential involves ____ coated nerves,
A lipid coating on nerve axons that serves as an insulator
Myelin
Propagation of A.P. along nerve cells is what type of conduction
(to jump in Spanish)
Saltatory Conduction
Saltar
Areas of no myelin that contain voltage gated channels only in nodes
Nodes of Ranvier
Action potential is generated at nodes, ion current travels rapidly between nodes. Regenerate action potential at next node
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In the myelinated or unmyelinated nerve, the action potential travels from the beginning to the end of the nerve. When it reaches the end, it must enter the
synapse
Why are myelinated nerves advantageous?
Speed of conduction
Junction between nerve and effector cell. Permits and preserves communication between cells.
In skeletal muscle, what is the synapse?
Synapse
Neuromuscular Junction
In the nervous system, a synapse exists between 2 nerves.
The neuron that submits action potential to the synapse is called the
Pre-synaptic neuron
The neuron that receives the action potential from the synapse
Post-synaptic neuron
Anatomical arrangement that is the most common, the axon of the pre-synaptic neuron synapses with the dendrite of the post-synaptic neuron.
Axo-Dendritic (axo-somatic) synapse
Anatomical arrangement where the axon intersects with another axon and may go in two directions
Axo-axonal synapse
Anatomical arrangement with 2 dendrites
Anatomical arrangement with a dendrite and a body
Dendro-Dendritic Synapse
Dendro-somatic synapse
Communication between neurons can be modified and protected by the surrounding
What’s the most common type of these cells?
Glial Cells
The astrocyte
These type of glial cells absorb extra K+ ions from neurons, recapture and recycle NTs, and are connected to each other by gap junctions
Astrocytes
With what chemical do astrocytes communicate with one another via their gap junctions?
Ca2+
Functional arrangement of gab junctions that are found in the brain. There is ion flow from one cell to another
Electrical Synapses
The gap junction proteins in gap junctions of pre synaptic and post synaptic membrane
Connexons
Synapse with a synaptic cleft where there is no physical contact between cells and no ion flow between cells
Chemical Synapses
These type of synapses use a NT that is synthesized and stored by the presynaptic nerve in synaptic vesicles
Chemical Synapses
Where did chemical synapse occur where we’ve studied?
Neuromuscular junction
How are chemical synapses in the brain different from those in skeletal muscle?
They go from nerve to nerve, not nerve to muscle
As before, the plasma membrane of the terminal bouton of the pre-synaptic cell contains what type of voltage gated channels?
Ca2+ voltage gated channels
Is intracellular of extracellular Ca2+ higher before AP arrives?
Extracellular is higher
When A.P. arrives to the chemical synapse, what happens
Channels open and Ca2+ diffuses into terminal bouton
What does Ca2+ flow into terminal bouton cause?
Synaptic Vesicle migration and fusion with plasma membrane
How does the NT from the terminal bouton in chemical synapses enter the synaptic cleft?
Diffusion
What happens to the NT wants it reaches post synaptic membrane?
Binds with receptors
What does binding of NTs to receptors on post synaptic neuron membrane initiate?
Which is often followed by…
Graded potential
Action potential
The only place in the body where you see action potential always following graded potential in post synaptic cell is the..
Neuromuscular junction
The three methods of degradation and removal of NT to prevent inappropriate graded/action potential initiation
Pre-synaptic neuron reuptake (good for recycling)
Glial cell uptake
Enzymatic degradation and diffusion of components
NT type that occurs in NM junction, widespread throughout cerebral cortex, brainstem and hippocampus, therefore possibly memory
(Chemical classification)
Acetylcholine
NTs made from amino acids (protein based) are called
Biogenic amines
A type of catecholamine involved in coordination of body movements, feel good NT (love), deficient in Parkinson’s, excess in schizophrenia
Dopamine
Important catecholamine NT for sleep/wake cycle, attention, feeding, and feeling good
Norepinephrine
Catecholamine that is similar to norepinephrine, considered the same
Epinephrine
A type of Indolamine that is important in the sleep/wake cycle, appetite, mood regulation (deficient in depression)
Serotonin
An indolamine that is important in wakefulness, appetite, learning and memory
drowsiness from anti ___ drugs (benadryl)
Histamine
In general, what to biogenic amines regulate?
Biological clock
Mood/behavior
This recreational drug can bind to biogenic amine receptors and cause hallucinations
LSD
amino acids in nervous system have specific or general roles?
General
2 Amino acids in CNS that are inhibitory
GABA
Glycine
Amino acid in CNS that is excitatory
Glutamate
One of two peptides in the CNS that is an important mediator of pain transmission in the PNS
Substance P
One of two peptides in the CNS that are natural opiates, blocks pain and inhibits substance P
Endorphins
An excitatory or inhibitory bolecules; present in the CNS and PNS; important for pain modulation
ATP (purine)
The nitrogen base within ATP that is inhibitory on the brain and induces sleep. Caffeine blocks its receptors.
We’re tired because there is free adenosine that was used by ATP
Adenosine
A gas molecule involved in learning and memory and strengthening synapse formation
Nitric Oxide
NT that causes action potential on a post-synaptic neuron
Excitatory
NTs that cause suppression of action potential on post-synaptic neuron
Inhibitory
Excitation or inhibition is normally determined by what?
The receptor at the post-synaptic membrane
Excitation or inhibition can be accomplished by two means
Direct and Indirect
These type of receptor opens ion channels directly after binding to the NT. Ex: Acetocholine
Direct Receptor
Channel linked receptors (direct) are seen when rapid response is needed
NM Junction
This type of receptor uses second messengers to open ion channels and also initiate other intracellular effects
ex:: g-protein linked receptor
Indirect Receptor
Post synaptic potential that is often located on dendrites, and often involves sodium ion channels
EPSP - excitatory post-synaptic potentials
Type of post synaptic potential that is often in the cell body, open CL- channels (Cl-enters cell and hyperpolarizes)
Action potential cannot occur
Inhibitoory post-synaptic Cell
Most of the synapses in the brain are electrical or chemical?
Chemical
Since chemical synapses are more complicated, slower, and take more energy, why are they more abundant in the brain?
Chemical synapses allow discrete control
Electrical impulses are fast but uniform
Type of summation when multiple impulses are sent rapidly to the post-synaptic neuron
ensures suppression or excited (inhibitory or excitatory)
Temporal
Type of summation where several pre-synaptic neurons send impulses to the post-synaptic neuron simultaneously
Important in chemical synapse
Can have different types of synapses depending upon receptor, good for control
Spatial
An amplifying type of circuit of neurons
different events occur because of one single event
Divergent
A concentrating type of circuit of neurons
See, hear, smell, touch = love (one output)
Convergent
A reverberating type of neural circuit
Goes round and round fro usually a number of hours
Ex) Sleep and wake, found in brain stem
Oscillating
Type of processing that is typically a reflex arc
Serial-sensation
Higher level mental functions are often performed by what type of processing?
Parallel Processing
Rapid, automatic responses to stimuli that are serial-sensation processing
Reflex arc
Components of a reflex arc (6)
Stimulus Receptor Sensory neuron Integration center Motor Neuron Effector
The component of a reflex arc that translates a stimulus into A.P.
Receptor
The component of a reflex arc that carries the A.P. to the CNS
Sensory Neuron
The component of the reflex arc that is the CNS
Integration Center
The component of the reflex arc that carries A.P. to the effector (muscle)
Motor Neuron
The component of the reflex arc that executes the appropriate response
Effector
What’s an example of a stimulus that we don’t have a receptor for so we don’t see when it’s effecting us?
UV light
Name the two type of reflexes
Visceral
Somatic
Type of reflex that involves glands
Visceral
Type of reflex that involves skeletal muscles
This includes spinal reflexes - stretch deep tendon, crossed extensor, superficial
Somatic
A somatic reflex that involves muscle spindles embedded in skeletal muscle, made of intrafusal fibers
each skeletal muscle contains many spindles, not just one
Stretch Reflex
More muscle spindles means more….
Flexor pollicis muscle has more or them that latissimus dorsi
control
Which fibers are in the non-contratile center?
Which fibers synapse at contractile ends?
Sensory Fibers
Gamma Motor Fibers
When large skeletal muscle is stretched, the spindle is also stretched. Stretch irritates the ____ fibers which fires AP to the spinal cord
Sensory Fibers
At the spinal cord, there is a synapse with a ______ neuron supplying skeletal muscle and antagonist muscle
Alpha motor Neuron
What action does the stimulated/stretched muscle have?
What action does that antagonist muscle have?
Contraction
Relaxation
Spindle tension is maintained by APs from….
Gamma motor neurons
Spindle tension must be maintained at all times so that when the skeletal muscle is stretched, the spindle fiber is stretched enough to irritate the sensory nerves. If the spindle becomes loose, than no mechanical irritation of the sensory nerves will occur
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The deep tendon reflex area with collagen fibers in a tendon with sensory nerve endings attached. They synapse in the spinal cord.
Golgi Tendon Organ
In response to stretch of a tendon, the GTO is stimulated and AP fires off along sensory nerve. Synapse with alpha motor neurons of both stretched and antagonistic muscle.
What happens to stretched muscle?
What happens to antagonist muscle?
Stretched muscle relaxes
Antagonist muscle contracts
What does the deep tendon reflex with the GTO prevent?
What type of control?
Muscle tearing
Postural Control
Reflex of withdrawal due to a painful stimulusm occurs BEFORE concious perception of a stimulus
Flexor reflex
Reflex of ipsilateral withdrawal and contralateral extension
ex) walking along beach, step on sharp seashell, withdraw foot and extend other foot to keep upright (postural)
Crossed extensor
Two type of superficial reflexes
Plantar
Abdominal
The superficial reflex that tests integrity of L4-S2 nerve roots
If normal it will cause (only if babies walk)
If abnormal, it will cause….
Plantar Reflex
Downward flexion of toes (plantar flexion) (opposite if baby doesn’t walk)
Babinski sign
Superficial reflex that tests the integrity of T8-T12.
Normal =
Abdominal Superficial Reflex
umbilical moves to stimulated side due to abdominal muscle contraction
