Final Review Flashcards
Mechanisms for maintaining a voltage across a neuron’s membrane
Selective Permeability: lipid bilayer that separates the extracellular from intracellular space allows some substances to pass through, but not others
Active ion transport: specialized pumps within the lipid bilayer that pump ions in and out of the cell
Action potentials
produced by voltage gated ion channels
propagated down the axon, from the soma toward the synapse
When a presynaptic neuron fires an action potential, it causes a postsynaptic potential in the postsynaptic neuron.
Axon hillock
Cone shaped region where the axon emerges from the soma. Contains a high density of voltage gated channels
EPSPs and IPSPs
At the Summation at the Axon Hillock, EPSPs add in mV, while IPSPs reduce
Synapses
briefly translate electrical action potentials into chemical signals, then back into electrical signals.
When an AP arrives at the Synapse, it activates voltage gated calcium (Ca2+) channels, which allow calcium levels to increase in the presynaptic terminal, which causes vesicles to fuse with the membrane of the presynaptic terminal, releasing neurotransmitter into the synaptic cleft.
Synaptic Vesicles
small bags filled with neurotransmitters, just waiting in the presynaptic terminal for an action potential to arrive.
Ionotropic receptors
fancy ion channels. Neurotransmitter molecules bind directly onto ionotropic receptors. This causes a conformational change – the receptor changes its shape, which allows ions to pass through.
Different ionotropic receptors allow different ions to enter the postsynaptic neuron. Those that allow cations to enter are excitatory synapses and produce EPSPs. Those that allow anions to enter are inhibitory synapses and Produce IPSPs
Metabotropic receptors
indirectly allow ions to enter the postsynaptic neuron. Neurotransmitter molecules bind directly onto metabotropic receptors too. But these receptors do not allow ions in. Instead, they activate G proteins (also called second messengers), that bind to ion channels from the inside, allowins ions to enter the postsynaptic neuron.
G proteins
Talk to other machinery inside cell to facilitate synaptic plasticity.
Can be activated by metabotropic receptors to bind to ion channels from the inside allowing ions to enter the postsynaptic neuron.
Drugs and Neurotransmitter Receptors
Neurotransmitters are endogenous, produced from within, agonists of neurotransmitter receptors.
Drugs that mimic or potentiate the actions of a transmitter are called exogenous agonists.
A partial agonist only partially activates a receptor.
Drugs that reduce the normal action of a neurotransmitter are called agonists
Psychedelics (Hallucinogens)
Hallucinogens act on serotonin receptors.
LSD (acid) is a serotonin receptor agonist
Psilocybin (magic mushrooms) are agonists for serotonin receptors and bind particularly in the prefrontal cortex
MDMA (ecstasy) increases extracelullar levels of serotonin (+ dopamine and norepinephrin) in part by blocking their reuptake. This leaves more transmitter in the synaptic cleft to bind to postsynaptic receptors.
Psychedelics (Dissociatives)
Dissociatives act on glutamate receptors
Ketamine: inhibits NMDA glutamate receptors by occupying the Ca2+ channel
Dextramethorphan (cough syrup) is metabolized to DXO, which is an NMDA receptor antagonist
Sensations are routed into the brain
Labeled lines: Nerve fibers that carry information about each sensory modality are segregated from one another, keeping sensory information about different modalities separate until they reach the brain.
Eventually combined together in the brain in a concept called binding.
There can even be labeled lines within a particular sensory modality, for different types of tough (light, stretch, pain, etc.)
Spatial Receptive Fields
Often have center-surround organization, which have three regions. They are most responsive to stimuli in the center. They are suppressed by stimuli in a ring around the center. And they are unaffected by stimuli outside the surround.
Attention alters neural responses
ERPs (which are measures of neural activity) made over primary visual cortex are different when a subject views the exact same image, depending on whether or not they are attending to it.
Motor plans
strive for speed and accuracy.
The speed/accuracy tradeoff is the concept that improvement in one of these goals usually comes at the cost to the other.
Motor neurons
Most motor neurons synapse onto a few muscle fibers.
The fewer the fibers a motor neuron connects to, the finer the control of movement.
Motor neurons and the muscle fibers they connect to form the motor unit.
The muscle fibers that a motor neuron connect to produce a voltage, called electromyograms (EMGs)
Motor Cortex
Primary motor cortex lies just anterior (in front) to the somatosensory cortex.
Like the somatosensory cortex, the motor cortex is organized (like a homunculus)
Together, motor cortex neurons form a population code of movement
Motor Cortex Responses Measuring Experiment
Monkey reaches in one of several different directions while the action potentials produced by M1 neurons are recorded.
Each movement is made several times, and the action potential patterns produced by a neuron are visualized to examine the tuning of each neuron
The activity of a single neuron is not adequate for decoding movement direction
Visualizing motor cortex neurons
Each M1 neuron has a best direction, which is the reach direction at which the neuron fires the most action potentials.
When arm movements are made in one direction, a population of M1 neurons are active. And a largely (but not completely) non-overlapping population of neurons are active when arm movements are made in another direction
Patient HM
had his medial temporal lobe removed, including his hippocampus and surrounding cortical regions.
HM suffered rom anterograde amnesia, or the ability to form new memories. But he didn’t lose the ability to form all memories (non-declarative)
Long Term Memory
Declarative: Things you know that you can tell others (hippocampus dependent)
- Episodic: remembering your first day of school (Storage in cortex) - Semantic: knowing the capital of france (Storage in cortex)
Non-Declarative: Things you know that you can show by doing (hippocampus independent)
- Skill Learning: knowing how to ride a bike (Basal ganglia, motor cortex, cerebellum)
- Priming: Being more likely to use a word you heard recently (Cortex)
-Classical conditioning: salivating when you see your favorite food (Cerebellum)
Short term habituation
occurs because the synapse connecting the sensory motor neuron becomes weaker (Gill withdrawal)
Long term habituation
Occurs because some of the synapses connecting the sensory to motor neuron are pruned away (Gill Withdrawal
Schizophrenia Positive Symptoms
Abnormal behavioral states that are gained. (Symptoms that are present but should not be).
Hallucinations, Delusions, Disorganized thought and speech. Bizarre behaviors
Schizophrenia Negative symptoms
Abnormalities that reflect insufficient functioning. (Characteristics of the individual that are absent but should be present.
Lack of emotional expression, reduced facial expression (Flat effect), inability to experience pleasure in everyday activities (anhedonia).
Reduced conversation (alogia), Diminished ability to begin or sustain activities, social withdrawal
Delusion
false belief that is strongly held in spite of contratry evidence
Hallucination
realistic sensory percept that is not actually happening
Schizophrenia Cognitive Symptoms
Refers to problems with processing and acting on external information.
Memory problems, poor attention span, difficulty making plans, reduced decision making capacity, poor social cognition, abnormal movement patterns
Dopamine Hypothesis
Antipsychotic drugs are more effective than lobotomies
Idea that schizophrenia results from excessive levels of DA or excessive postsynaptic sensitivity to DA.
The strength with which a drug binds to the dopamine D2 receptor strongly predicts the dose of the drug necessary to relieve symptoms
Depression
caused by a combination of genetic and environmental factors. (like schizo)
Stress is one of the more common environmental factors that leads to depression
Dose Response Curve
Shows increasing drug dose (x axis) agains increasing strength of response being studied
The effective dose (ED50) is the dose at which the response reaches 50% of its maximum effect
The lethal dose (LD50) is defined as the dose that takes you 50% of the way to lethality
The therapeutic index is the difference between ED50 and LD50 doses
Psychedelics
Hallucinogens act on serotonin receptors
LSD (acid) is a serotonin receptor agonist
Psilocybin (magic mushrooms) are agonists for serotonin receptors and bind
particularly in the prefrontal cortex
MDMA (ecstasy) increases extracellular levels of serotonin (+ dopamine and
norepinephrin) in part by blocking their reuptake. This leaves more transmitter in
the synaptic cleft to bind to postsynaptic receptors.
Dissociatives act on glutamate receptors
Ketamine (special K) inhibits NMDA glutamate receptors by occupying the Ca2+
channel
Dextramethorphan (cough syrup) is metabolized to DXO, which is an NMDA
receptor antagonist. (“robo-tripping”)
