Question 1

Why do Na⁺ ions enter the cell when voltage-gated Na⁺ channels are opened in neurons?

Accepted Answer

A)  because the Na⁺ concentration is much lower outside the cell than it is inside 
B)  because the Na⁺ ions are actively transported by the sodium-potassium pump into the cell 
C)  because the Na⁺ concentration is much higher outside the cell than it is inside, and the Na⁺ ions are attracted to the negatively charged interior 
D)  because the Na⁺ concentration is much higher outside the cell than it is inside, and the Na⁺ ions are actively transported by the sodium-potassium pump into the cell 
A)  because the Na⁺ concentration is much lower outside the cell than it is inside 
B)  because the Na⁺ ions are actively transported by the sodium-potassium pump into the cell 
C)  because the Na⁺ concentration is much higher outside the cell than it is inside, and the Na⁺ ions are attracted to the negatively charged interior 
D)  because the Na⁺ concentration is much higher outside the cell than it is inside, and the Na⁺ ions are actively transported by the sodium-potassium pump into the cell

Question 2

Action potentials are normally carried in only one direction: from the axon hillock toward the axon terminals. If you experimentally depolarise the middle of the axon to threshold, using an electronic probe, then ________.

Accepted Answer

A)  no action potential will be initiated 
B)  an action potential will be initiated and proceed only in the normal direction toward the axon terminal 
C)  an action potential will be initiated and proceed only back toward the axon hillock 
D)  two action potentials will be initiated, one going toward the axon terminal and one going back toward the hillock 
A)  no action potential will be initiated 
B)  an action potential will be initiated and proceed only in the normal direction toward the axon terminal 
C)  an action potential will be initiated and proceed only back toward the axon hillock 
D)  two action potentials will be initiated, one going toward the axon terminal and one going back toward the hillock

Question 3

The three stages of information processing in animals include ________.

Accepted Answer

A)  chemical senses, mechanoreception, and vision 
B)  dendrites, a cell body, and an axon 
C)  a presynaptic cell, neurotransmitters, and a postsynaptic cell 
D)  sensory reception, an integrating centre, and effectors (motor neurons) 
A)  chemical senses, mechanoreception, and vision 
B)  dendrites, a cell body, and an axon 
C)  a presynaptic cell, neurotransmitters, and a postsynaptic cell 
D)  sensory reception, an integrating centre, and effectors (motor neurons)

Question 4

Action potentials move along axons ________.

Accepted Answer

A)  more slowly in axons of large than in small diameter 
B)  by activating the sodium-potassium "pump" at each point along the axonal membrane 
C)  more rapidly in myelinated than in unmyelinated axons 
D)  by reversing the concentration gradients for sodium and potassium ions 
A)  more slowly in axons of large than in small diameter 
B)  by activating the sodium-potassium "pump" at each point along the axonal membrane 
C)  more rapidly in myelinated than in unmyelinated axons 
D)  by reversing the concentration gradients for sodium and potassium ions

Question 5

Refer to the following graph of an action potential to answer the question.   The membrane's permeability to sodium ions is greatest at label ________.

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D Disallow randomisation 
A)  A 
B)  B 
C)  C 
D)  D Disallow randomisation

Question 6

Why are action potentials usually conducted in one direction?

Accepted Answer

A)  The nodes of Ranvier conduct potentials in one direction. 
B)  The brief refractory period prevents reopening of voltage-gated sodium channels. 
C)  The axon hillock has a higher membrane potential than the terminals of the axon. 
D)  Voltage-gated channels for both Na⁺ and K⁺ open in only one direction. 
A)  The nodes of Ranvier conduct potentials in one direction. 
B)  The brief refractory period prevents reopening of voltage-gated sodium channels. 
C)  The axon hillock has a higher membrane potential than the terminals of the axon. 
D)  Voltage-gated channels for both Na⁺ and K⁺ open in only one direction.

Question 7

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels ________.

Accepted Answer

A)  are always open, but the concentration gradients of ions frequently change 
B)  are always closed, but ions move closer to the channels during excitation 
C)  are open or closed depending on their type, and are specific as to which ion can traverse them 
D)  open in response to stimuli, and then close simultaneously, in unison 
A)  are always open, but the concentration gradients of ions frequently change 
B)  are always closed, but ions move closer to the channels during excitation 
C)  are open or closed depending on their type, and are specific as to which ion can traverse them 
D)  open in response to stimuli, and then close simultaneously, in unison

Question 8

The amino acid that operates at most inhibitory synapses in the brain is ________.

Accepted Answer

A)  acetylcholine 
B)  endorphin 
C)  nitric oxide 
D)  gamma-aminobutyric acid (GAB
A)  
A)  acetylcholine 
B)  endorphin 
C)  nitric oxide 
D)  gamma-aminobutyric acid (GAB
A)

Exam 48: Neurons, Synapses, and Signalling

Why do Na⁺ ions enter the cell when voltage-gated Na⁺ channels are opened in neurons?

Action potentials are normally carried in only one direction: from the axon hillock toward the axon terminals. If you experimentally depolarise the middle of the axon to threshold, using an electronic probe, then ________.

The three stages of information processing in animals include ________.

Action potentials move along axons ________.

Refer to the following graph of an action potential to answer the question. The membrane's permeability to sodium ions is greatest at label ________.

Why are action potentials usually conducted in one direction?

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels ________.

The amino acid that operates at most inhibitory synapses in the brain is ________.

Evolution, the Themes of Biology, and Scientific Inquiry

The Chemical Context of Life

Water and Life

Carbon and the Molecular Diversity of Life

The Structure and Function of Large Biological Molecules

A Tour of the Cell

Membrane Structure and Function

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cell Communication

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

The Molecular Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

Viruses

Dna Tools and Biotechnology

Genomes and Their Evolution

Descent With Modification: a Darwinian View of Life

The Evolution of Populations

The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

Bacteria and Archaea

Protists

Plant Diversity I: How Plants Colonised Land

Plant Diversity Ii: the Evolution of Seed Plants

Fungi

An Overview of Animal Diversity

An Introduction to Invertebrates

The Origin and Evolution of Vertebrates

Vascular Plant Structure, Growth, and Development

Resource Acquisition and Transport in Vascular Plants

Soil and Plant Nutrition

Angiosperm Reproduction and Biotechnology

Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

Animal Development

Nervous Systems

Sensory and Motor Mechanisms

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