Neuro 470 Chapter 2 – Flashcards

dendrite -‐-‐> cell body -‐-‐> axon -‐-‐> terminal button

axoplasmic transport; microtubules

-glial or neuroglial -Neuroglial cells provide nutrients, oxygen, and physical support to neurons.

-intracellular sodium concentrations are kept low. -The sodium-‐potassium transporter acts to move sodium ions out of the axon thus keeping intracellular sodium concentrations at a low level.

-The AP is an all-‐or-‐none electrical event -The action potential is an all-‐or-‐none event, occurring only if depolarization at the axon hillock meets threshold.

-entry of a negative ion; hyperpolarization -Hyperpolarization is produced by the entry of a negative ion into the axon or exit of a positive ion.

-influx of calcium ions into the axon terminal. -The depolarization of the terminal from the incoming action potential opens voltage-‐gated calcium channels. Influx of calcium ions into the axon terminal triggers neurotransmitter release from the presynaptic membrane.

-open ion channels in the postsynaptic membrane -Neurotransmitters act to produce postsynaptic membrane potentials by opening or closing ion channels, through which ions move down their electrochemical gradient. The gradient consists of two parts: the electrical potential and chemical concentration across the membrane.

metabotropic; G protein activation leads to activation of a second-‐ messenger

Ribosomes produce proteins. Endoplasmic reticulum: Rough ER contains the ribosomes (produces proteins). Smooth ER synthesizes lipids. Microtubules: Responsible for transport around the interior of the neuron. Mitochondria: Provide energy to the neuron. Lysosomes: Degrade surplus cellular materials. Golgi apparatus: Package the products of a secretory cell.

1. Resting State (B) A. Sodium are all open, potassium closed 2. Initial Depolarization (C) B. Sodium closed, potassium closed 3. Rising Phase of AP(A) C. Sodium start to open, potassium closed 4. Falling Phase of AP (E) D. Sodium closed, potassium closing 5. Undershoot (D) E. Sodium refractory, potassium open

detect changes in external/internal environment and send info to the CNS Afferent

controls contraction of a muscle or secretion of a gland Efferent

• located entirely w/in CNS • -Local: form circuits w/nearby neurons and analyze small pieces of info • -Relay: connect diff circuits of local interneurons in one region of brain with another

Greek, Dendron, for tree. Recipients of messages passed through synapses, the junction between terminal buttons of a sending cell and portion of somatic or dendritic membrane of receiving cell. Can be long (base of sciatic nerve to big toe). May or may not have myelin sheath.

Cell body that contains nucleus and much of the machinery that provides for life processes of cell

conveys info (action potential) from cell body to terminal buttons.

a specialized part of the cell body (or soma) of a neuron that connects to the axon. the last site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon.

Most axons divide and branch many times, these knobs are found at their ends. Secrete a chemical neurotransmitter.

Isolates axon. Fatty later to move electric pulses faster

Gap in the myelin sheath of a nerve, between adjacent Schwann cells.

Excite or Inhibit receiving cell and thus help to determine whether an action potential occurs in its axon. (details described later) *A neuron may receive info from tens or hundreds of other neurons, each which can form a large number of synapses with it.

• Structure consisting principally of lipid molecules(double layer) that defines out boundaries of a cell. Constitutes many of the organelles, such as Golgi. Membrane proteins w/special functions: receptors, channels, pumps • Lipid bi-layer defines boundary of cell (and many organelles) • Contains channels, pumps, receptors

• viscous, semiliquid substance contained in the interior of a cell • Viscous, semiliquid substance inside the cell

• organelle responsible for extracting energy from nutrients (ATP) • Extracts energy (ATP) from nutrients

• oval in center, enclosed by nuclear membrane, contains nucleolus and chromosomes • Helps package neurotransmitters to be secreted through exocytosis

• Rough ER: site of protein synthesis (contains ribosomes) • Smooth ER: lipid synthesis

• Nucleolus • Chromosomes

long strands DNA containing genetic info

produces ribosomes, involved in protein synthesis

• Structural support/shape of cell • Composed of proteins strands o Largely microtubules arranged around a hollow core o Highly dynamic

Proves the cell structure, a hallow cord inside the cytoskeleton

• One axon and many dendrites attached to soma. Most common type in CNS • 1 axon, Many dendrites

• One axon and one dendrite attached to soma. Usually sensory, detect events in environment and communicate to CNS • 1 axon, 1 dendrite • Sensory System (primarily) o Ex: vision, auditio

• One axon stalk that divides into two branches a short distance away. Like bipolar, transmit sensory info from the environment to the CNS. Most detect events that affect skin, other detect events in joints, muscles, and internal organs. • 1 axon, divides into 2 branches o Receiving sensory info o Sending info into CNS • Somatosensory System o Ex: touch, pain, temp

Provide support (nerve glue) and nutrients for neurons, clean up waste in extracellular fluid ( CNS gila)

• Each cell forms one segment of myelin sheath for several adjacent axons • Insulate axons from one another

• One segment of myelin sheath for a single axon. • Guides for axonal regrowth, a distinguishing feature from oligodendrocytes

An Electrical Force The effect of membrane potential on the ion's movement (magnets)

The diffusion of ions across the membrane is driven by two combined forces, collectively the electrochemical gradient. from high concentration to low concentration

Electrical change across a cell membrane. Difference in electrical potential from outside to outside. Stored up energy. Based on Charge of Ions Present

cell becomes positively charged (or less negative) in the cell

when the cell is becoming more negatively charged inside the cell

the sodium-potassium pump, continuously pushes Na+ back out of the axon. Active transport using ATP. Sodium-potassium transporters exchange Na+ for K+, 3 sodium ions out for every two potassium ions in.

Action potentials "jump" from one node of Ranvier to the next Advantages: Economic: expend less energy - less sodium-potassium transporters required Speed: conduction is faster in myelinated axons

postsynaptic potential that makes the neuron more likely to fire an action potential.

postsynaptic neuron less likely to generate an action potential.

EPSPs and IPSPs sum together at axon hillock to effect firing rate

Once trigger, an AP is propagated down the axon at the same strength to the end of the fiber If axon branches, AP splits but does not diminish in size

Rate (not size) of APs varies with strength of depolarizing stimulus Amount of neurotransmitter release varies with rate of AP firing

Loaded with neurotransmitters in the terminal button

At the end of the dendrite

open and allow Ca into the pre-synaptic ending. dependent on the voltage across the membrane

(direct) Ion channel opens when neurotransmitter attaches to binding site

(indirect) Neurotransmitter binds to receptor G protein activates an enzyme, produces a 2nd messenger that opens nearby channels

Metabotropic receptor on the presynaptic membrane Responds to the NT released by same neuron Regulate synthesis and release of the NT Inhibited if too much is released Increased if not enough is released Do not control ion channels or produce changes in membrane potential

NT's in synaptic cleft are transported back into terminal buttons

destruction of NT after release

Released by an endocrine gland into extracellular fluid, distributed through bloodstream, and have effects on target cells in other organs Many neurons contain hormone receptors