Psych 2210 Communication Within the Nervous System

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65 Terms

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neuron

a specialized cell of the nervous system that communicates information through electrical and chemical signals

  • 86B in the human brain

  • ~50% of brain cells

4 morphologically defined regions:

  1. cell body

  2. dendrites

  3. axon

  4. axon terminals

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dendrites

extensions of the neuron that receive information from other cells

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myelin sheath

increases speed of neural signals

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axon hillock

generates neural impulse

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axon

transfers neural signals

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axon terminal

forms junctions with other cells; contains neurotransmitters

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cell body (soma)

  • most prominent part of the neuron

  • filled with cytoplasm

    • salt water + ions, proteins, molecules

  • contains numerous organelles

    • nucleus: DNA-containing structure

    • endoplasmic reticulum, Golgi apparatus, ribosomes: protein synthesis

    • mitochondria: ATP production

  • cell membrane

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cytoplasm

in cell body; salt water + ions, proteins, molecules

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nucleus

in cell body; DNA-containing structure

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location of protein synthesis

in cell body; endoplasmic reticulum, Golgi apparatus, ribosomes

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mitochondria

in cell body; responsible for ATP production

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cell membrane

bilipid layer with proteins ā€œfloatingā€ within

  • lipid molecules = hydrophilic heads + hydrophobic tails

    • allows membrane to hold its shape

      • heads orient toward liquid

      • tail orients away from liquid

        • double-layer membrane

  • some small molecules can pass through; larger molecules only pass through protein channels

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motor neurons

  • carry commands to the muscles and other organs

  • brain → body

  • found mainly within CNS

    • multipolar

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sensory neurons

  • carry information from the body and external world

  • body → brain

  • found mainly within PNS

    • unipolar, bipolar

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interneurons

  • connect one neuron to another within CNS

  • multipolar

  • short or no axon

  • communicates locally

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selective permeability

some small molecules can pass through the cell membrane, larger molecules only pass through protein channels

→ polarization

  • positive electrical charge on one side and a negative charge on another side

  • difference in electrical charge between the inside and outside of the neuron = voltage

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voltage

the difference in electrical charge between the inside and outside of the neuron

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resting potential

the difference in charge between inside and outside of a neuron at rest (usually -70 mV)

  • as a result of unequal distribution of electrical charges on extracellular (outside cell) and intracellular (inside) fluid

  • the cell is ā€œpolarizedā€

  • maintained by passive transport (short-term) and active transport (long-term)

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ions outside the cell

lots of sodium (Na+) and chloride (Cl-), more positive ions

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ions inside the cell

lots of potassium (K+) and anions (A-), more negative ions (negative resting potential)

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ion channels

proteins in cell wall; pore in the center allows ions to enter and leave the cell

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passive transport

short-term way of maintaining resting potential; can move ions when the voltage-gated channels are not active

  • concentration gradient (force of diffusion): high concentration to low

  • electrostatic pressure: ions repelled from the side with similar charges; want to move toward the opposite charge

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active transport

long-term way of maintaining resting potential

  • sodium-potassium pump: uses ATP, pumps 3 Na+ out and 2 K+ in, uses 40% of the cell’s energy to keep the cell negatively charged at rest

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concentration gradient (force of diffusion)

passive transport; high concentration to low

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electrostatic pressure

passive transport; ions repelled from the side with similar charges; want to move toward the opposite charge

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sodium-potassium pump

active transport; uses ATP, pumps 3 Na+ out and 2 K+ in, uses 40% of the cell’s energy to keep the cell negatively charged at rest

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action potential

abrupt depolarization of the membrane that allows the neuron to communicate over long distances

  • if local threshold (by a stimulus) can reach a certain threshold, it is initiated (all-or-none)

  • then, electrical signal travels along axon

  • synapses on another neuron or the target

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glial cells

nonneural cells that provide a number of supportive functions to neurons

  • myelin-producing

    • oligodendrocytes (CNS)

    • Schwann cells (PNS)

  • astrocytes

  • microglia

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myelin-producing glia

  • myelin: fatty tissue that wraps around axon to insulate it

  • oligodendrocytes (CNS): 1 cell can wrap multiple internodes

  • Schwann cells (PNS): 1 cell wraps single internode

  • Nodes of Ranvier: gaps in myelin sheath

  • saltatory conduction: a form of transmission in which action potentials appear to jump from node to node

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myelin

myelin-producing glia, fatty tissue that wraps around axon to insulate it

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oligodendrocytes

myelin-producing glia, found in CNS, 1 cell can wrap multiple internodes

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Schwann cells

myelin-producing glia, found in PNS, 1 cell wraps single internode

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Nodes of Ranvier

myelin-producing glia, gaps in the myelin sheath

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saltatory conduction

myelin-producing glia, a form of transmission in which action potentials appear to jump from node to node

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astrocytes

type of glial cells

  • support/form blood-brain barrier, insulate neurons, structural support etc.

  • compose 20-50% of the brain volume

  • arise from radial glia

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microglia

  • mediate immune responses in the nervous system

  • engulf damaged tissue and invading organisms

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vesicles

membrane-enclosed bubbles at axon terminals which store neurotransmitters

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chemical transmission at the synapse

  1. action potential arrives at axon terminals

  2. opening of Ca2+ channels

  3. Ca2+ enters

  4. vesicles move to presynaptic membrane

  5. fusion of vesicles

  6. neurotransmitter release

effect on cellular processes:

  • EPSP and IPSP

  • neurotransmitter effects on presynaptic and postsynaptic neuron

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excitatory postsynaptic potential (EPSP)

postsynaptic cellular process; when receptors open sodium channels to produce a partial depolarization of the dendrites and cell body

  • partial depolarization - more likely to produce action potential

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inhibitory postsynaptic potential (IPSP)

postsynaptic cellular process; when receptors open potassium channels, chloride channels, or both to produce a hyperpolarization of the dendrites and cell body

  • hyperpolarization - less likely to produce action potential

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spatial summation

postsynaptic cellular process; combines potentials occurring simultaneously at different locations on the dendrites and cell body

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temporal summation

postsynaptic cellular process; combines potentials arriving a short time apart, from either the same or separate inputs

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neurotransmitter binding

postsynaptic cellular process

  • ionotropic receptors

    • ligand-gated ion channels

    • binding of neurotransmitter to receptor directly opens or closes an ion channel

    • local, fast, short

  • metabotropic receptors

    • ligand-activated proteins and enzymes ā€œsecond messengersā€

    • binding to receptors activates g-protein

    • distant, slow, long

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ionotropic receptors

neurotransmitter binding process, postsynaptic cellular process

  • ligand-gated ion channels

  • binding of neurotransmitter to receptor directly opens or closes an ion channel

  • local, fast, short

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metabotropic receptors

postsynaptic cellular process

  • ligand-activated proteins and enzymes ā€œsecond messengersā€

  • binding to receptors activates g-protein

  • distant, slow, long

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reuptake

presynaptic cellular process; process in which transmitters are taken back into the terminals

  • controlling this process is used extensively in psychopharmacology (e.g., antidepressants)

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autoreceptors

control the amount of transmitter

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neurotransmitter release

  • reuptake

  • excess neurotransmitters:

    • broken down by enzymes

    • absorbed by glial cells

    • diffuse away

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neurotransmitters

chemicals the neuron releases to communicate with a muscle, an organ, or the next neuron in a chain

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acetylcholine

  1. between nerves and muscles (movement)

    1. nerves communicate with muscles by releasing it

    2. release → muscle contraction

    3. inhibition → muscle relaxation

  2. involved in learning

    1. memory - death of these neurons in Alzheimer’s disease

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GABA

amino acid; main inhibitory neurotransmitter

  • anti-anxiety drugs and alcohol act to enhance it

  • deficiency can cause epilepsy

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glutamate

amino acid; main excitatory neurotransmitter

  • involved in learning and memory - lots in cerebral cortex

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serotonin

monoamine; involved in mood, sleep and arousal, aggression, depression, OCD, and alcoholism

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dopamine

monoamine

  • movement (death of these neurons impairs movement, Parkinson’s disease)

  • promotes reinforcing effects of food, sex, and abused drugs

    • motivation

  • schizophrenia (blocking its receptors improves psychological disturbance)

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norepinephrine

monoamine

  • released during stress

  • increase arousal and promote sleep/waking cycle

  • related to depression

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epinephrine (adrenaline)

monoamine

  • stress hormone from adrenal glands e.g., making heart beat faster

  • minor role in brain

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endorphins/enkephalins

neuropeptide

  • block pain, produce pleasure (heroin, morphine)

  • placebo, acupuncture effects

    • placebo can cause increase in its release/transmission

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Substance P

neuropeptide; transmission of pain info

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Neuropeptide Y

neuropeptide; initiates eating and produces metabolic shifts

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ligand

binds to receptor (has affinity)

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affinity

similarity, resemblance in structure

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direct agonist

binds and mimics effect of transmitter (has affinity and efficacy)

  • number of target chemicals increase

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efficacy

ability to produce a desired or intended result

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indirect agonist

increases neurotransmitters via a mechanism other than receptor interaction - changes could be in synthesis, storage, release, reuptake, or degradation stage as listed above (has efficacy)

  • number of target chemicals increase

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antagonist

binds and does not have an effect, preventing transmitter action (has affinity)

  • blocker