Biology 1001: Nervous System Chapters 42-43

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Questions and Answers

Which type of animal is the simplest nervous system found in?

Cnidarians

What type of nervous system extends from the brain through the vertebral column?

Spinal cord

All animals have a nervous system.

False

What is the name of the simplest nervous system?

Nerve net Signup and view all the answers

What type of animal is a nerve ring around the mouth found in?

Echinoderms Signup and view all the answers

Which animal phylum is the first to evolve a brain with defined regions?

Platyhelminthes Signup and view all the answers

What are collections of neuron cell bodies called?

Ganglia Signup and view all the answers

What does the term 'cephalization' refer to?

Concentration of sense organs at the anterior end Signup and view all the answers

What are the two main branches of the nervous system in chordates?

Central nervous system (CNS) and peripheral nervous system (PNS) Signup and view all the answers

What type of cells make up the nervous system?

Neurons Signup and view all the answers

What are the extensions of a neuron's plasma membrane that receive incoming signals called?

Dendrites Signup and view all the answers

What is the name of the extension of a neuron's plasma membrane that sends signals to other cells?

Axon Signup and view all the answers

What part of the neuron is important in the generation of electrical signals?

Axon hillock Signup and view all the answers

What are the end branches of an axon called?

Axon terminals Signup and view all the answers

What are the cells that surround neurons called?

Glial cells Signup and view all the answers

What are the noninsulated gaps along a myelinated axon called?

Nodes of Ranvier Signup and view all the answers

What are the glial cells that produce myelin in the human brain and spinal cord called?

Oligodendrocytes Signup and view all the answers

What are the glial cells that form myelin on axons outside the brain and spinal cord called?

Schwann cells Signup and view all the answers

What type of signals do dendrites receive from other neurons?

Electrical and chemical Signup and view all the answers

What does the cell body do with incoming signals?

Processes them and generates outgoing signals Signup and view all the answers

What do axon terminals do?

Transmit signals to other cells Signup and view all the answers

What are the three main types of neurons?

Sensory neurons, motor neurons, and interneurons Signup and view all the answers

What is the difference in charge inside and outside a cell called?

Membrane potential Signup and view all the answers

What is the resting membrane potential of a neuron typically?

-70 mV Signup and view all the answers

What are the three factors that influence the resting potential of a neuron?

The Na+/K+-ATPase pump, the relative permeability of the membrane to different ions, and the number of leak channels for potassium ions (K+) Signup and view all the answers

What are the two types of gated ion channels that contribute to changes in membrane potential?

Voltage-gated ion channels and ligand-gated ion channels Signup and view all the answers

What are the two main types of changes in membrane potential?

Graded potentials and action potentials Signup and view all the answers

Graded potentials always have the same amplitude.

False Signup and view all the answers

Action potentials are always large in amplitude.

True Signup and view all the answers

Action potentials can be graded.

False Signup and view all the answers

Action potentials are actively propagated down the axon.

True Signup and view all the answers

What is the threshold potential for an action potential?

-55 to -50 mV Signup and view all the answers

What happens during depolarization?

The membrane potential becomes more positive as sodium ions (Na+) flow into the cell. Signup and view all the answers

What happens at the peak of an action potential?

Voltage-gated sodium channels inactivate, and voltage-gated potassium channels open. Signup and view all the answers

What is the absolute refractory period?

The period during which a neuron cannot generate another action potential, no matter how strong the stimulus. Signup and view all the answers

What is the relative refractory period?

The period during which a neuron can generate another action potential, but only with a stronger than usual stimulus. Signup and view all the answers

What is the junction where a nerve terminal meets another neuron, muscle cell, or gland called?

Synapse Signup and view all the answers

What are the two main types of synapses?

Electrical synapses and chemical synapses Signup and view all the answers

What type of synapse involves gap junctions?

Electrical synapse Signup and view all the answers

What type of synapse involves neurotransmitters?

Chemical synapse Signup and view all the answers

What happens to the membrane potential of a postsynaptic neuron when a neurotransmitter binds to its receptor?

It can either depolarize or hyperpolarize depending on the type of neurotransmitter and receptor. Signup and view all the answers

What are the two main classes of postsynaptic receptors?

Ionotropic receptors and metabotropic receptors Signup and view all the answers

What is the function of the Na+/K+-ATPase pump?

It actively transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, establishing and maintaining concentration gradients. Signup and view all the answers

What are the five classes of neurotransmitters?

Acetylcholine, biogenic amines, amino acids, neuropeptides, and gaseous neurotransmitters. Signup and view all the answers

What is the function of acetylcholine?

It is a neurotransmitter that is released at neuromuscular junctions, where it stimulates muscle contraction. It also plays a role in the brain and heart. Signup and view all the answers

What are biogenic amines?

Neurotransmitters that are derived from amino acids. They include dopamine, norepinephrine, epinephrine, serotonin, and histamine. Signup and view all the answers

What are the two most important amino acid neurotransmitters?

Glutamate and GABA (gamma-aminobutyric acid) Signup and view all the answers

What are neuropeptides?

Neurotransmitters that are short chains of amino acids. They often act as neuromodulators, modifying the effects of other neurotransmitters. Signup and view all the answers

What are the two main gaseous neurotransmitters?

Nitric oxide (NO) and carbon monoxide (CO) Signup and view all the answers

Study Notes

Biology 1001, Chapters 42 and 43

Chapter Organization: Chapters 42 and 43 cover the nervous system. Chapter 42 focuses on the cells of the nervous system, while chapter 43 covers neuroscience, evolution, and structure/function of the nervous system.

Nervous System Organization

Central Nervous System (CNS): Includes the brain and spinal cord. In vertebrates, the spinal cord runs from the brain through the vertebral column.
Peripheral Nervous System (PNS): All neurons outside the CNS. The distinction between the CNS and PNS is less clear in some invertebrates.

Representative Nervous Systems

Sponges: Lack a nervous system.
Nerve Net: The simplest nervous system, found in cnidarians (jellyfish, hydras, anemones). Neurons in a network connect to each other, and activation in one area spreads throughout the network, often stimulating contractile cells.
Echinoderms: Slightly more complex than nerve nets. A nerve ring surrounds the mouth, connected to radial nerves extending to the arms. Mouth and arms can function independently.
Flatworms (Platyhelminthes): The first animal phylum to evolve a brain with defined regions and synaptic connections. Characteristic "nerve ladder" structure: Two nerve cords extend the length of the animal and are connected by transverse nerves.
Annelids: Have ganglia (collections of neuron cell bodies) with limited processing ability and few synapses. Nerves and ganglia are often segmented throughout the animal.
Simple Mollusks: Similar to annelids, having a pair of anterior ganglia and paired nerve cords that coordinate local sensory and motor functions.
Insects (Drosophila): Advanced nervous system with a brain that is subdivided with distinct functions.
Advanced Mollusks: Well-developed brain with subdivisions. Coordinate complex visual sensing and motor functions.
Chordates: Brain connected to dorsal spinal cord (CNS). Composed of nerves (PNS) that route information into and out of the central nervous system.

Trend Toward Cephalization

The trend in nervous systems is towards cephalization, which involves the concentration of sense organs at the anterior (head) end of the animal. As the brain becomes larger, it becomes comprised of more anatomical and functional regions.

Cellular Components of Nervous Systems

Neurons: These are electrically excitable cells that send and receive electrical/chemical signals to/from other neurons or cells throughout the body.

Neuron Structure

Cell Body (Soma): Contains the nucleus and organelles.
Dendrites: Extensions of the cell membrane that receive incoming signals. They can be single or branched.
Axons: Extensions of the cell membrane that send signals to other cells. They typically have a single branch called an axon hillock, where signals are generated. Signals travel along the axon to the axon terminals, which form connections with other cells (such as neurons or muscle cells) at the synapse.

Glial Cells

Support and regulate neurons, wrapping around the axons at intervals to form an insulating myelin sheath.
Glial cells in the spinal cord and brain are oligodendrocytes.
Glial cells in the axons outside the brain/spinal cord are Schwann cells.

Signal Direction

Dendrites receive electrical/chemical messages.
Cell body processes incoming signals and generates outgoing ones.
Axons send outgoing signals to axon terminals.
Axon terminals transmit signals to nearby cells.

Three Main Types of Neurons

Sensory Neurons (Afferent): Detect information from the outside world or internal body conditions and transmit the signal to the CNS.
Motor Neurons: Send signals away from the CNS to elicit a response (like movement).
Interneurons (Association Neurons): Form connections between neurons in the CNS; have many dendrites and short, highly branched axons, allowing for complex connections between neurons.

Membrane Potential

A difference in charge between the inside and outside of the cell membrane.

Resting Membrane Potential

Neurons at rest have an internal resting potential which is -70mV and is more negative than the exterior.

Factors Affecting Resting Potential

The Na+/K+-ATPase is critical for maintaining concentration gradients.
Unequal permeability (selective permeability) of the membrane with leak channels influencing K+ and Na+ ions, greatly impacting the overall charge.

Excitatory and Inhibitory Neurotransmitters

They act like the brake and accelerator of a nervous system.
More than 100 different types in animals. Categorized by size, structure and combined effects.

Generation and Transmission of Electrical Signals

Action potentials are large depolarizations; all-or-none fashion.
Action potentials travel along axons and trigger a response at the next cell junction.

Absolute Refractory Period

While inactivation gates of Na+ channels are closed, the cell cannot respond to another stimulus.
Limits the frequency of action potentials and prevents the action potential from traveling backward down the axon.

Conduction of Electrical Signals

Graded potentials reach threshold potential at the axon hillock, triggering the opening of Na+ voltage-gated channels.
Sequential opening of Na+ channels produces a wave of depolarization down the axon to the axon terminal.

Synapses

Junctions where nerve terminals meet a neuron, muscle cell, or gland.
Electrical Synapses- electric charge flows through gap junctions.
Chemical Synapses- Neurotransmitter acts as the signal.

Chemical Synapse

Presynaptic cell releases neurotransmitters into the synaptic cleft after an action potential opens voltage gated Ca2+ channels, triggering neurotransmitter vesicles to fuse with the presynaptic membrane.
Neurotransmitters bind to receptors on the postsynaptic cell, thereby causing a new graded potential to be generated.
Neurotransmitter molecules are reabsorbed/broken down

Different Types of Postsynaptic Receptors

Ionotropic Receptors: Ligand-gated ion channels open in response to the neurotransmitter.
Metabotropic Receptors: G-protein coupled receptors initiate changes in the postsynaptic cell.

Five classes of neurotransmitters

Acetylcholine
Biogenic amines
Amino acids
Neuropeptides
Gaseous neurotransmitters

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Description

This quiz covers Chapters 42 and 43 of Biology 1001, focusing on the structure and function of the nervous system. It includes key concepts regarding the central and peripheral nervous systems, as well as the representative nervous systems of various organisms. Test your understanding of neuroscience and the evolutionary aspects of nervous systems.