Brain and Behavior test2 Flashcards
Magnetoencephalograph (MEG)
Similar to EEG but measures faint magnetic fields generated by brain activity instead of electric
Electroencephalograph (EEG)
Records electrical activity produced by various brain regions, measures sleep stages
Positron-emission tomography (PET)
Records emission of radioactivity from injected radioactive chemicals to produce detailed image
Functional magnetic resonance imaging (fMRI)
Modified MRI, oxygen consumption of brain to show moving picture, safer and less expensive than pet
Computerized axial tomography (CAT or CT scan)
Injection of dye in blood, passage of X-rays through head, sees tumors and abnormalities
Magnetic resonance imaging (MRI)
Powerful magnetic field to image the brain
Types of synapses
Dendrodendritic, axondendritic, axoextracellular, axosomatic, axosynaptic, axoaxonic, axosecretory
Dendrodendritic
Synapse where dendrites send messages to other dendrites
Axondendritic
Axon terminal of one neuron synapses on dendritic spine of another
Type of synapse
Axoextracellular
Terminal with no specific target, secretes transmitter into extracellular fluid
Synapse type
Axosomatic
Axon terminal ends on cell body
Synapse type
Axosynaptic
Axon terminal ends on another terminal
Synapse type
Axoaxonic
Axon terminal ends on another axon
Synapse type
Axosecretory
Axon terminal ends on tiny blood vessel and secretes transmitter directly into blood
EPSP
Excitatory post-synaptic potential
Graded potential that decays over time and space
IPSP
Inhibitory post-synaptic potential
When x causes y to be hyperpolarized
Temporal summation
If presynaptic neuron is stimulated more than once, this can occur
Spatial summation
Two different parts of post synaptic neuron are stimulated at the same time
Electrical synapses
Gap junction, direct contact membrane to membrane of neurons
Chemical synapse
Second type of synapse
Gap junction
Electrical synapse
Info passed through tubular channels containing cytoplasm, cytoplasm is continuos, found on mammal brains.
Advantage: two way comm, fast
Chemical synapses
Neurotransmitters across synapses
Neurotransmitters
Chemicals that travel across the synapse and allow communication. Made from diet, can excite or inhibit.
Neuroteansmitter sequence of chemical events
1) synthesis and packaging
2) transport to axon terminals
3) release via exocytosis
Amino acid derivatives
Glutamate and GABA, Neurotransmitters
Peptides
Neurotransmitters:
Met-enkephalin
And leu-enkephalin
Larger than other Neurotransmitters
Co-localization
Presence of two or more Neurotransmitters in same axon terminal
Exocytosis
Neurotransmitters are released by this
Vesicle containing nt fuses with membrane of presynaptic terminal
Postsynaptoc response
Effect of NT depends on the receptor on the Postsynaptic cell
(ionotropic, metabotropic, neuromodulatory)
Ionotropic Response
Neurotransmitter attaches to receptors and immediately opens ion channels
- very quick, doesn’t last very long
- involves GABA, glutamate, glycine
Metabotropic response
Slower and longer lasting
- involves dopamine, norepinephrine, serotonin, glutamate or GABA
- NTs attach to metabotropic receptor
Metabotropic events
Behaviors such as taste, smell, attention, arousal and pain
Neuromodulatory Response
Produced by Neuropeptides, colocalized in same neuron
-effect neighbors, all release same neuropeptide
Autoreceptors
Receptors that detect the amount of transmitter release and inhibit further synthesis
Presynaptic inhibition
neurotransmitter binding to presynaptic receptor decreases neurotransmitter from that axon terminal
Presynaptic facilitation
Neurotransmitter (NT) binding to presynaptic receptor increases release of NT from axon terminal
The nerve impulse
Electrical message transmitted down axon, action potential
Nerve impulse travel
Does not just travel down, is regenerated along the way so not weakened.
1 m per second to 100 meters per second depending on myelination
Neuron at rest
Inside cell K+ and anions (large protein)
Outside: Na+ and some CI-
Membrane Potential
Voltage difference, difference in electrical charge between inside and outside neuron
Electrical gradient
Membrane of a neuron maintains this, difference between inside and outside electrical charge
-called polarization
Resting potential (neuron)
State of the neuron prior to sending nerve impulse
Ionic basis of resting membrane potential
These things explain it:
1) chemical gradient
2) electrical gradient
3) selective permeability
4) sodium-potassium pump
Concentration gradient
How much of a thing in a cell spreads out throughout cell, amount is the concentration
Electrical gradient
Inside a cell negative, outside positive, that means outside wants to go in etc
Semi-permeable nature of membranes
Cell membrane allows some chemicals to pass in more freely than others
Sodium, potassium, calcium, chloride can only get in when membrane channels open
What can get in cell membrane always?
O2, CO2, H2O, urea
Hyper polarization
Increasing difference between the electrical charge of two places
Depolarization
Refers to decreasing the difference so membrane potential moves toward zero
Characteristics of graded potential
Amplitude of response is proportional to intensity of stimulus that elicited it
-amplitude of response decreases we potential moves through neuron
Action potential
Rapid depolarization of a neuron, varies from one neuron to another, this is a nergnimpuls
Threshold of excitation
When any stimulation produces massive depolarization which triggers a nerve impulse or action potential
Voltage-activated channels
Eg sodium and potassium
Proteins whose permeability depends upon the voltage difference across the membrane
Sodium-potassium pump
Process of restoring to original distribution of ions
-can be dangerous when too much sodium builds up in axon, can kill cells, but only when you take drugs or stroke
Local anesthetic
Local anesthetic blocks sodium channels which stops sodium entering cell
Example: novocain and xylocaine
All or none law
Law for action potentials, if the threshold is reached it works, of it isn’t reached nothing happens
-they don’t decrease as they travel, stay the same and are the same no matter the strength of stim
How are different messages conveyed with action potentials?
Frequency or rhythm
Refractory periods
Time when neuron to re-excitation and will not produce action potential
Absolute refractory period
First part of the period on which membrane cannot produce an action potential, regardless of stimulation
Relative refractory period
Second part in which it takes a stronger than usual stimulus to trigger an action (takes about 2 to 4 milliseconds)
Propagation of action potential
Starts axon hillock
- propagated down the axon
- regenerated along the way like the way like ‘the wave’
Action potential on un- myelinated axons
Charge goes down, depolarizes areas on membranes it passes causing those membrane areas to reach excitation threshold and and generate their own action potential
Electrical resistance
Opposition to the passage of a steady electrical current
-influenced by axon diameter and insulation (effect speed of propagation)
Conduction velocity
How fast action potential is propagated (measured in meters per second)
= distance action pot. Moves/ time it take to travel the distance
Multiple Sclerosis
Occurs when myelin sheath is destroyed.
Progressive disease in early adult life.
-breaks down and then hardening of sheath and axons into scar tissue
Symptoms of MS (multiple sclerosis)
Muscular weakness, visual dis, urinary incontin, tremor, loss of motor control (remission up to 2 years)
Cause unknown, maybe autoimmune problem. No cure
Antagonist (drug)
Drug that blocks effects of natural neurotransmitter
Agonist (drug)
Drug that mimics or increases a Neurotransmitters effects
Inverse agonist (drug)
Drug that produces opposite effect of natural Neurotransmitter
Affinity (drug)
Refers to how tightly bound the drug is to the receptor, can be strong or weak
Efficacy (drugs)
Refers to a drug’s tendency to activate the receptor
Other behaviors that release dopamine
Sexual excitement, gambling and video games and drugs
Stimulant (drugs)
Drugs that increase excitement, alertness, motor activity, elevate mood
Ex: amphetamine, cocaine, Ritalin, nicotine
Hallucinogenic drugs
Drugs that cause distorted perception
LSD, ecstasy
Opiate (drugs)
Drugs derived from, or similar to, those from opium poppy, effects of decreasing pain perception
Ex endorphins
Three ways that drugs can act on agonists or antagonists
1) alter release of neurotransmitter from presynaptic neuron
2) alter the binding of NT to Postsynaptic receptor
3) alter the events that occur after neurotransmission is complete
Drugs can alter release of neurotransmitter from presynaptic neuron
Alter synthesis of neurotransmitter (NT)
Alter amount of NT released from axon terminal (ecstasy releases dopamine with low dose etc)
Caffeine effect
Blocks glutamate which makes you tired, example of disinhibition
Cholinergic
Having to do with acetylcholine (ACh)
Effect two major cholinergic receptors: muscarinic=metabotropic, nicotinic=ionotropic
Three sites with no brain blood barrier
Pineal gland: chemicals for day-night cycles
Area postrema: entry of toxic substances to induce vomiting
Pituitary: allows entry of Chemicals that influence pituitary hormones
Acetylcholine (ACh)
Activates muscles
In central nervous system: enhances sensory perceptions when we wake up and in sustaining attention. Plasticity, arousal, reward.
One member family, similar to amino acid
Capsaicin
Used as a way to deter abuse of certain drugs
Catecholamine
Group containing epinephrine (adrenaline), norepinephrine and dopamine
Dopamine (DA)
Monoamine neurotransmitter, responsible for reward-driven learning
-stimulants such as cocaine and methamphetamine act directly on dopamine system
Enkephalin
There are lucine and methionine ones, met-enkephalin and leu-enkephalin.
They are peptides
Regulates process of encoding and processing noxious stimuli
GABA
Chief inhibitory neurotransmitter in central nervous system. An amino acid.
Glutamate
Excitatory transmitter in the brain, major mediator of excitatory signals in mammalian central nervous system
Nitric oxide
Free radical
Important biological regulator
A gas released by local neurons
Norepinephrine (NE)
Stress hormone, attention Alertness, arousal and influences or reward system
Prozac
Antidepressant that’s a serotonin reuptake inhibitor
Serotonin
Known as 5-HT
Substance P
A neuropeptide, Neurotransmitter and neuromodulator. Associated with inflammatory process and pain
