Animal Physiology ~ Vick ~ Ch.4: Neuron Structure & Function

Front 1

Neurons

Back 1

These vary in structure and properties, they use the same basic mechanisms to send signals, they have a resting membrane potential & they are excitable

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Four

Back 2

There are ___ functional neural zones

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Signal reception

Back 3

The dendrites and cell body are responsible for this

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Membrane potential

Back 4

An incoming signal is received & converted to change in membrane potential

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Axon hillock

Back 5

This is responsible for signal intergration, action potentials start here

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Action potential

Back 6

Strong signals are converted to this

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Axon

Back 7

This is responsible for signal conduction, it can be wrapped in a myelin sheath, action potential travels down this

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Axon terminals

Back 8

These are responsible for signal transmission, they release neurotransmitters, action potentials travel to here

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Negative

Back 9

Neuron membrane potential is ___ at rest

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Depolarization

Back 10

Membrane potential becomes less negative than resting value

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Repolarization

Back 11

Membrane potential returns to resting value

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Hyperpolarization

Back 12

Membrane potential become more negative than resting value

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Electrical signals

Back 13

Changes in membrane potential act as...

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Factors that contribute to membrane potential

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Distribution of ions across the membrane, permeability of the ions, & charges attached to the ions

Front 15

Goldman equation

Back 15

This is used for calculation of membrane potential

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Selectively altering permeability

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Neurons depolarize or hyperpolarize by...

Front 17

Gated ion channels

Back 17

These open or close in response to a stimulus, most notably neurotransmitters, they only allow specific ions to pass through, this terms tells you what passes through

Front 18

Nernst Equation

Back 18

This equation says that as permeability to a specific ion increases, membrane potential will approach that ion’s equilibrium potential

Front 19

Graded potentials

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These vary in magnitude depending on the strength of the stimulus; more neurotransmitter = more ion channels open = larger magnitude of this; they travel short distances; these start at the dendrites of the neuron & enough of them cause action potentials

Front 20

Na+ & Ca+

Back 20

In depolarization these channels open...

Front 21

K+ & Cl-

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In hyperpolarization these channels open...

Front 22

Conduction with decrement

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This says that the magnitude of graded potential decreases with increasing distance from the opened ion channel

Front 23

Decrement

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This is due to leakage of changed ions across membrane, electrical resistance of cytoplasm, & electrical properties of the membrane

Front 24

Electrotonic current spread

Back 24

This is when positive charge spreads through the cytoplasm and causing a depolarization of an adjacent membrane

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Characteristics of Action Potentials

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They are triggered by net graded potential at an axon hillock, they do not degrade over time, they travel long distances along a membrane, they are all-or-none, they must reach a threshold potential to fire

Front 26

Simultaneously

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Many graded potentials can be generated ___, as there are many receptor sites and many types of recpetors

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Spatial summation

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This occurs when graded potentials from different sites influence the net change

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Temporal summation

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This occurs when graded potentials at slightly different times influence net change

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Absolute refractory period

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In this a cell is incapable of generating a new action potential

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Relative refractory period

Back 30

In this it is more difficult for a cell to generate a new action potential

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Voltage gated channels

Back 31

These change shape due to changes in membrane potential, these are closed at resting membrane potential, this term tells you how that channel opens (not what goes through)

Front 32

Na+ channel

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This channel type has two gates: a voltage dependent, activation gate which opens when membrane potential reaches the threshold and a time-dependent, inactivation gate which closes after a brief time

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Myelin

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This is an insulating layer of lipid-rich Schwann cells wrapped around an axon, it reduces "leakage of charge across axon, speeds up information transmission, found in vertebrate cells

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Nodes of Ranvier

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These are areas of exposed membrane between myelin, action potentials occur in these

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Internodes

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The myelinated region of a neuron

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Saltatory conduction

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This phenomenon occurs in myelinated cells, action potentials "leap" from Node of Ranvier to Node of Ranvier & electrotonic current spreads through internodes; this is rapid

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Backwards/ retrograde transmission

Back 37

On an axon, upstream/ just behind the area of depolarization Na+ channels are in an absolute refractory period this prevents...

Front 38

Action potential frequency

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This carries information, increases with stronger stimuli, the max is limited by the absolute refractory period

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Synapse

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Signal transmission from neuron to another cell, it includes the presynaptic cell, synaptic cleft, and postsynaptic cell

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Synaptic cleft

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The space between the presynaptic and the postsynaptic cell

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Postsynaptic cell

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This may be another neuron, a muscle cell, or an endocrine cell

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Neuromuscular junction

Back 42

This a synapse between a motor neuron and a skeletal muscle cell

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High amounts of neurotransmitter in the synapse

Back 43

High action potential frequency will cause...