lecture 15 Flashcards
Is there OBESITY TREATMENT
Surgeries have developed that are designed to reduce the amount of food that can be eaten during a meal or interfere with absorption of calories from the intestines
what is Bariatric surgery
aimed at stomach, small intestine, or both
The most effective form of bariatric surgery is special form of gastric bypass called what
the Roux-en-Y gastric bypass, or RYGB
With RYGB surgery, what happens
jejunum (second part of small intestine, immediately “downstream” from duodenum) is cut, and upper end is attached to stomach pouch. (The digestive enzymes secreted into duodenum will now go upwards through upper intestine to meet up with meal in the stomach pouch.)
Rats that have the RYGB procedure do what
eat less, lose weight, and show decreased levels of ghrelin and increased levels of PYY.
what is Learning
refers to the process by which experiences change our nervous system and hence our behavior.
Learning refers to the process by which experiences change our nervous system and hence our behavior.
We refer to these changes as what
memories (memory traces or memory engrams)
what kinds of Memories are there
Memories can be transient or durable, conscious or unconscious, personal or impersonal
Accessing memories is known as what
memory retrieval
can memories go away
Memories traces can degrade or be corrupted, and thus be gone forever. They can also simply become inaccessible, either temporarily or permanently, but still exist somewhere in the brain.
what are the two types of learning
Associative Learning
Non-Associative Learning
what is Non-Associative Learning
Often refers to the phenomena of habituation and sensitization, which are when you start to respond differently
to a stimulus just because you have perceived it (seen it, smelled it, etc.) some number of times before. E.g., if a stimulus is neutral and without predictive value, animals habituate to it.
what animal was experimented on for Non-Associative Learning
The aplysia is an invertebrate sea slug with a simple nervous system (20,000 neurons).
why was the aplysia used for the experiment
It has a large gill for respiration, and a siphon through which it expels water.
If the siphon is lightly touched, the gill withdraws reflexively.
Repeated light touching of the siphon will reduce the magnitude of the reflex until the Aplysia completely ignores this stimulus
Repeated light touching of the siphon will reduce the magnitude of the reflex until the Aplysia completely ignores this stimulus.
This waning of sensitivity to repeated stimulation is known as what
habituation
what is habituation
waning of sensitivity to repeated stimulation
the sea slug’s response to an electrical shock may become greater with additional exposures. Increased sensitivity to a stimulus is known as what
sensitization
what is sensitization
Increased sensitivity to a stimulus
Does the sensory neuron become less sensitive to touch? (HABITUATION OF APLYSIA GILL WITHDRAWAL REFLEX)
No, it depolarizes the same amount
Has the excitability of the sensory neuron changed?
(HABITUATION OF APLYSIA GILL WITHDRAWAL REFLEX)
Yes, fewer action potentials occur when the siphon is touched (3 after habituation vs 4 before it).
Has the synaptic connection weakened between the
sensory and motor neurons? (HABITUATION OF APLYSIA GILL WITHDRAWAL REFLEX)
Yes
Has the motor neuron become less excitable?(HABITUATION OF APLYSIA GILL WITHDRAWAL REFLEX)
No, it spikes the same amount when depolarized.
Has the synaptic connection weakened between the motor neuron and gill?(HABITUATION OF APLYSIA GILL WITHDRAWAL REFLEX)
no, the gill is as sensitive to an action potential in the motor neuron as before.
what is Intrinsic excitability
refers to the number of action potentials a neuron will exhibit in response to an influx of positive charge
Intrinsic excitability refers to the number of action potentials a neuron will exhibit in response to an influx of positive charge.
Ø This variable is heavily influenced what
by the type and number of leak channels and voltage-gated channels in the membrane. For example, if there are extra leak channels, the neuron will be less excitable (it will exhibit fewer action potentials in response to the same synaptic input).
what is Synaptic strength
refers to the amount of positive (or negative) charge that enters the postsynaptic neuron (the postsynaptic response) following an action potential in the presynaptic cell.
Synaptic strength refers to the amount of positive (or negative) charge that enters the postsynaptic neuron (the postsynaptic response) following an action potential in the presynaptic cell.
Ø This variable depends what
both pre- and postsynaptic conditions. For example, the number of presynaptic voltage-gated calcium channels influences how many vesicles will be released in response to an action potential. The number of postsynaptic neurotransmitter receptors influences the sensitivity of the cell to neurotransmitter.
Cell excitability and synaptic strength can be directly measured how
in brain slice recordings
Synaptic plasticity refers to what
refers to changes in the number or function of synapses, which alter the synaptic strength.
what is EPSPs an acronym form
excitatory postsynaptic potentials
what are EPSPs (excitatory postsynaptic potentials)
membrane depolarizations caused by evoked activity in some number of inputs (synapses).
what is Long-term potentiation (LTP)
the phenomenon by which EPSPs become stronger in a long-term, stable manner
for Long-term potentiation (LTP), Long-term increase in the strength of the connection between what
two neurons (synaptic strength).
for Long-term potentiation (LTP), Repeated high-frequency stimulation of the inputs to a neuron (synapses) can do what
increase the strength of the activated synapses. LTP is often mediated by an increase in postsynaptic neurotransmitter receptors.
what is Long-term depression (LTD) and how does it work
Long-term decrease in the strength of the connection between two neurons (synaptic strength). Low-frequency stimulation of the inputs to a quiet neuron can decrease the strength of the activated synapses. LTD is often mediated by endocannabinoid signaling
what is Hippocampal formation
Forebrain structure of temporal lobe, constituting important part of limbic system. Includes the CA1,2,3, as well as dentate gyrus and subiculum
what is the Hippocampal formation involved in
Involved in learning and memory and shows remarkable synaptic plasticity in some areas
High frequency stimulation (~100 Hz) for 1 second, repeated a few times at 10 second intervals often produces what
LTP
High frequency stimulation (~100 Hz) for 1 second, repeated a few times at 10 second intervals often produces LTP.
• The same number of pulses given at a slow rate (1 Hz) over 5-10 minutes often produces what
the opposite effect: LTD
High frequency stimulation (~100 Hz) for 1 second, repeated a few times at 10 second intervals often produces LTP.
• The same number of pulses given at a slow rate (1 Hz) over 5-10 minutes often produces the opposite effect: LTD. Why???
It turns out that LTP and LTD are influenced by both the amount of times the synapses was active as well as whether the postsynaptic neuron fired at those precise times
High frequency input stimulation often causes downstream neurons to do what
spike
summation of EPSPs brings the neurons across threshold
is Low frequency stimulation on its own sufficient to get downstream neurons to spike.
Low frequency stimulation on its own is often not sufficient to get downstream neurons to spike.
For LTP to occur what needs to happen
the release of neurotransmitter has to coincide with a substantial depolarization of the postsynaptic cell
what receptor is The Coincidence Detector
NMDA Glutamate receptor
The NMDA receptor is what kind of receptor
ionotropic glutamate receptor (ion-channel gated by the neurotransmitter glutamate)
The NMDA receptor is a ionotropic glutamate receptor (ion-channel gated by the neurotransmitter glutamate) that has a large ion pore. When the NMDA receptor binds glutamate and opens, magnesium (Mg2+) ions try to pass through the pore, what happens
they get stuck in it and completely block it. This Mg2+ blockage of the ion channel only occurs when the membrane potential is below threshold (< -40mV).
if the NMDA Glutamate receptor membrane is depolarized (more positive than -40 mV), close to threshold or during an action potential, then what happens to the Mg2+ ions
Mg2+ ions will not try to enter and thus not clog the pore
If the membrane is depolarized (more positive than -40 mV), close to threshold or during an action potential, then Mg2+ ions will not try to enter and thus not clog the pore. So, current flow through the NMDA channel is gated by what
both glutamate and membrane voltage
what ions will enter a cell through NMDA receptors
Na+ and Ca2+ but only when these receptors are bound to glutamate and Mg2+ is not clogging the pore.
The NMDA receptor plays a large role in what
learning
what are the 4 main MECHANISMS OF SYNAPTIC PLASTICITY
AMPA receptor
NMDA receptor
CaMKII
Nitric oxide
what is the AMPA receptor
The glutamate receptor that mediates most excitatory fast synaptic currents in the brain. It is ionotropic and opens when glutamate binds.
It lets in sodium ions which cause EPSPs (excitatory postsynaptic potentials) that depolarizes neurons
what is the NMDA receptor
Ionotropic glutamate receptor that can get blocked by Mg2+ ions when glutamate binds while cell is hyperpolarized. It only opens when both glutamate binds and the membrane potential is slightly depolarized. It lets in both sodium and calcium. Most glutamate synapses in the brain have AMPA and NMDA receptors.
what is the CaMKII
Type II calcium-calmodulin kinase. It is an enzyme that is activated by calcium influx through NMDA receptors. It plays a role in the intracellular signaling cascade that establishes long-term potentiation, by increasing the number of postsynaptic AMPA receptors.
(not focusing too much on this)
what is Nitric oxide
LTP can also be expressed through changes on the presynaptic side of things, but postsynaptic neurons often initiate the process. Many experiments suggest that nitric oxide can act as a retrograde messenger (released from postsynaptic membrane and detected by presynaptic membrane) to promote LTP.
do dentrites grow/form
yes, with LTP
what is Associative Learning
Typically includes most forms of stimulus-stimulus & stimulus- response learning. Probably is responsible for all learning.
Basically, when you perceive a stimulus, it either makes you more likely to think of something else (stimulus-stimulus) or it makes you more likely to respond in some way (stimulus- response).
what is Non-Associative Learning
Often refers to the phenomena of habituation and sensitization, which are when you start to respond differently to a stimulus just because you have perceived it (seen it, smelled it, etc.) some number of times before. E.g., if a stimulus is neutral and without predictive value, animals habituate to it.
what is Associative long-term potentiation
The increase in synaptic strength that occurs in weak synapses when they are active right around the time when stronger inputs caused the postsynaptic neuron to spike
what is Hebb’s rule
Hypothesis proposed by Donald Hebb that the cellular basis of learning involves the strengthening of synaptic connections that are active when the postsynaptic neuron fires an action potential. This is known as:
Fire together, wire together…more strongly than before. The synaptic connection does have to initially exist.
what are the main NATURE OF LEARNING
Perceptual learning
Motor learning
Relational learning
Stimulus– response learning
what is Perceptual learning
Learning to recognize stimuli
The basis of recognition & categorization
– Largely dependent on the neocortex – sensory association areas
what is Motor learning
Learning to move effectively
Choreographed skilled movement sequences
The basis of motor skills (bike riding, ball throwing, etc….) – Involves different brain areas involved in movement
what is Relational learning
Learning relationships among individual stimuli.
The basis of declarative memory, both episodic and semantic
– Largely dependent on the hippocampus and neocortex
what is Stimulus– response learning
Learning the best motor response to particular stimuli
The basis of classical (Pavlovian) and instrumental (operant) conditioning – Involves different brain areas depending on the stimulus and response
is Perceptual learning implicit memory or explicit
implicit
is motor learning implicit memory or explicit
implicit
is Relational learning (stimulus-stimulus learning) implicit memory or explicit
explicit
is Stimulus– response learning implicit memory or explicit
both
Perceptual learning enables us to recognize and identify what
object or situations. It is a pattern recognition system. Through perceptual learning we can recognize changes or variations in familiar stimuli and respond to those changes.
This unconscious, implicit learning involves changes in the strength of connections between neurons in primary and association sensory cortices
what is Visual Agnosia
Damage to regions of brain involved in visual perception not only impair ability to recognize visual stimuli but also disrupt people’s memory of visual properties of familiar stimuli
so these people can draw something they are looking at currently, but if you ask them to draw it soon after they will only remember the VERY basics and it will look nothing like what it should
Motor learning involves learning to make what
a sequence of coordinated movements.
Wegetfeedbackfromourmovementsfromour joints, vestibular system, eyes, ears, and everything else. We use this information to improve, optimize our movements
