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1

Neuroscience Definition

scientific study of the nervous system, chemistry, biology, computer science, engineering, linguistics, mathematics, physics, and psychology

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Santiago Ramon y Cajal

Reveals that neurons are individual cells.

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Sherrington

Discovered the synapse, 1. reflexes slower, 2. weak stimuli combine, 3. muscles relax/contract- thought neuron sent an excitatory message to leg being pinched and inhibitory message to other legs

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Behavioral Neuroscience

a.k.a. biological psychology, psychobiology, and physiological psychology, is the study of physiological, evolutionary, and developmental mechanisms of behavior and experience

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AMHS Brain Features

*Highly organized , specific, (i.e. specific areas handle specific tasks.
*Contains approximately 100 billion neurons and trillions of synaptic connections.
*Weighs three pounds on average, yet consumes 20-30% of caloric intake.
*Unlike static electronic circuitry, contains the unique ability to alter and change (plasticity).

*Gives rise to over 1000 brain nervous system disorders.
*Is directly responsible for all the incredible feats of science, technology, and art achieved by human beings.
*Is the most complex living structure in the known universe

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How do we know we use all of our brain?

*Evolutionary conservation.
*High caloric usage.
*Brain imaging.
*Localization of function.
*Sleep studies.

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Dualism

the belief that mind and body are different substances existing independently, Descartes, pineal gland, laws of thermodynamics, nothing created/destroyed, can't come out of nothing

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Problem of other minds

the difficulty in knowing whether other people or animals are have consciousness

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The Hard Problem

why and how is brain activity associated with consciousness

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Mendel

inheritance occurs through genes.

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Genes

basic units of heredity that maintain their structural identity from one generation to another.

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Proteins

determine the development of the body by:
forming part of the structure of the body.
serving as enzymes, biological catalysts that regulate chemical reactions in the body.

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Autosomal Genes

all other genes except for sex-linked genes

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Why do experiments on animals?

*Reductionism! (Breaking complex problems into smaller, easier to resolve parts)
*The underlying mechanisms of behavior are easier to study in nonhuman species.
*We are interested in animals for their own sake.
*What we learn about animals sheds light on human evolution.
*Some experiments cannot use humans because of legal or ethical reasons.

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Jobs in Neuropsychology

1. Research positions require a PhD in psychology, biology, neuroscience, or related field and may be in academic, government, or industrial settings.

2. Fields of therapy include clinical psychology, counseling psychology, school psychology, several specializations of medicine, and allied medical practice, such as physical therapy.

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Neuron definition

receive and transmit information to others cells

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Glia Definition

support neuron function in several ways

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Glia Cell Types

(Half the Total Volume of CNS)
Astrocytes: large, star shaped. Wraps functionally related axons, synchronizing the activity of the neuron group in waves (humans have the largest and most abundant astrocytes).
Microglia: Very small cells that remove waste material as well as viruses, fungi, and other microorganisms.
Oligodendrocytes: A type of glia that builds the myelin sheaths around certain neurons in the brain and spinal cord (CNS).
Schwann cells: A type of glia that builds the myelin sheaths around certain neurons in the periphery of the body (PNS).
Radial glia: Guides the migration of neurons and the growth of axons and dendrites during embryonic development.

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Types of Neurons

1. Motor Neurons: cell body located in the spinal cord, innervates musculature.
2. Sensory Neurons: specialized to be sensitive to a type of stimulus (i.e. light, sound, or touch), cell body located in the dorsal route ganglion.
3. Inter-Neurons/Intrinsic Neurons: pass information from one neuron to another, the majority of cells in NS are inter-neurons (i.e. cerebral cortex).

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Cell Body structures

contains the nucleus, mitochondria, ribosomes, and other structures found in other cells.
Also responsible for the metabolic work of the neuron

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Afferent

refers to bringing information into a structure. (Sensory Neurons). Brings information into the central nervous system.

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Efferent

refers to carrying information away from a structure. (Motor Neurons). Brings information out of the central nervous system.

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Interneurons/Intrinsic Neurons

are those whose dendrites and axons are completely contained within a single structure.

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Active Transport

brain.

-Glucose, hormones, amino acids, and vitamins are brought into the brain via active transport

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Glucose

is a simple sugar that is the primary source of nutrition for neurons.

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Thiamine

is a chemical that is necessary for the use of glucose.

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Neuron Nourishment

Neurons run primarily off of glucose (simple sugar).
*Glucose can easily pass across the blood brain barrier.
*Inability to use glucose is problematic.
*Chronic alcoholics often have a deficiency in vitamin B1 (thiamine), a chemical necessary for the use of glucose.
*Prolonged deficiency in B1 can lead to neuron death

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Electrical Gradient

a difference in electrical charge between the inside and outside of the cell. At rest, the neuron maintains an electrical polarization, 
(there exists a difference in electrical charge between the cell interior and exterior).

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Resting Potential

The difference in voltage of a resting neuron is called the resting potential.
-The resting potential remains stable until the neuron is stimulated.

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Threshold of Excitation

a level above which any stimulation produces a massive depolarization. (Approximately 15-20mv depolarizing change).

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Hyperpolarization, IPSP

refers to increasing the polarization or the difference between the electrical charge of two places

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Depolarization, EPSP

refers to decreasing the polarization towards zero

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AP

(a.k.a. nerve impulse): rapid depolarization of the neuron.
Speed = (less than 1 meter per sec – 100 meters per second)
*Considerably slower than an electrical impulse
*Axons regenerate the impulse along many points, so strength of impulse remains constant.
*This is achieved via the action of voltage gated ion channels

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selectively permeable

H20, carbon dioxide, urea, K+, and oxygen can freely cross the membrane.

Sodium (Na+), Potassium (K+), Calcium (Ca++), and Chloride (Cl-cross through ion channels that are sometimes open and sometimes closed depending on the state of the neuron, hence, their entry or exit is controlled

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Concentration at rest

Na+ molecules are concentrated outside of the cell. 

K+ is concentrated inside of the cell.

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Electrical Gradient

difference in positive and negative charges across a membrane.
(i.e. the cell interior is negative, the exterior is positive.)

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Concentration Gradient

difference in the distribution of ions across a membrane.
(i.e. the interior vs. exterior concentrations)

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na+ k+ pump

A mechanism that actively transports 3 sodium ions out of the cell while simultaneously drawing in 2 potassium ions.
*The SP pump requires energy (adenosine triphosphate:ATP).
*Various poisons (i.e. inhibit the SP pump, causing unsafe concentrations of NA+ outside the cell.
*Because of the selective permeability of the membrane, Na+ ions stay out of the cell once pumped out.
*Local anesthetic drugs block sodium channels and therefore prevent action potentials from occurring

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All or None Law

the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it

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Absolute Refractory Period

first part of the period in which the membrane can not produce an action potential. Lasts about 1ms.

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Relative Refractory Period

second part in which it take a stronger than usual stimulus to trigger an action potential. Lasts about 2-4ms

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Reflex arc

sensory neuron- spinal cord- brain/motor neuron, AP= 40m/s, reflex arc=15m/s or less

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Temporal Summation

the idea that repeated stimuli has a cumulative effect and can produce a nerve impulse when a single stimuli is too weak, lumpy line

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Spatial Summation

synaptic input from several locations can have a cumulative effect and trigger a nerve impulse

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Chemical Events at Synapse

1. The neuron synthesizes chemicals that serve as neurotransmitters.

2. Neurons store neurotransmitters in axon terminals or transport them there.

3. An action potential triggers the release of neurotransmitters into the synaptic cleft.

4. The neurotransmitters travel across the cleft and attach to receptors on the postsynaptic neuron.

5. The neurotransmitters separate from the receptors.

6. The neurotransmitters are taken back into the presynaptic neuron, diffuse away, or are inactivated by chemicals.

7. The postsynaptic cell may send negative feedback to slow the release of further neurotransmitters

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ACH

synthesized from acetyl coenzyme a (metabolized) and choline found in milk, eggs, and nuts, synthesized in presynaptic terminals (small), a modified amino acid

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Tryptophan

precursor for serotonin (poultry)

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Catacholamines

contain a catechol group and an amine group (epinephrine, norepinephrine, and dopamine)

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Amino Acids

glutamate (excitatory), GABA (inhibitory), glycine,
aspartate

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Monoamines

also modified from amino acids):
serotonin (5-HT), dopamine (DA), norepinephrine, epinephrine

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Peptides

(chains of amino acids): endorphins, substance P,
neuropeptide-Y

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Purines

ATP, adenosine, maybe others

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Gases (NT's)

NO (nitric oxide)

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Types of NT's

Amino Acids: glutamate (excitatory), GABA (inhibitory), glycine, aspartate.
A Modified Amino Acid: acetylcholine (AcH).
Monoamines (also modified from amino acids):
serotonin (5-HT), dopamine (DA), norepinephrine, epinephrine.
Peptides (chains of amino acids): endorphins, substance P,
neuropeptide-Y.

Purines: ATP, adenosine, maybe others.
Gases: NO (nitric oxide)

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Vesicles

tiny spherical packets located in the presynaptic terminal where neurotransmitters are held for release

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MAO

(monoamine oxidase) is a chemical that breaks down excess levels of some neurotransmitters (monoamines)

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Exocytosis

refers to the excretion of the neurotransmitter from the presynaptic terminal into the synaptic cleft.

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Phenylalanine precursor to

Tyrosine-dopa-dopamine-norepinephrine-epinephrine

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Transmission

across synapse, takes less than .01microseconds

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ionotropic effect

when a neurotransmitter attaches to receptors and immediately opens ion channels
Most effects occur very quickly and are very short lasting.
Most ionotropic effects rely on glutamate or GABA

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metabotropic effect

neurotransmitters attach to a receptor and initiates a sequence of slower and longer lasting metabolic reactions

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G protein

increases the concentration of a “second-messenger”

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Second Messenger

communicates to areas within the cell.
May open or close ion channels, alter production of activating proteins, or activate chromosomes

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Gap Junction

A few special-purpose synapses operate electrically.

Faster than all chemical transmissions.

the direct contact of the membrane of one neuron with the membrane of another.

Depolarization occurs in both cells, resulting in the two neurons acting as if they were one
Just like Na+ and K+ are voltage gate (i.e. voltage is required to open them), the channels found at the synapse are transmitter gated or ligand gated.

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Ligand

chemical that binds to another chemical

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Inactivation & Reuptake

reabsorption of the NT after use for repackaging and reuse.
This is achieved by a transporter, a membrane protein responsible for reuptake after release.
Certain chemicals also breakdown and remove spent neurotransmitters