chapter 35 Animal nervous system

the resting membrane potential is ___________ and results in part from the movement of _________ ions

-70 mV, potassium

name the three basic types of neurons and describe their function

1. sensory: respond to physical features such as temperature, light, touch, or to chemical signals such as molecules conveying odor or taste 2. interneurons: process info received by the sensory neurons and transmit it to different body regions 3. motor neurons: at the end of the pathway and produce a suitable motor response based on the info from the sensory neurons and interneurons

a neurons ability to generate action potential depends: A. on the axon reaching threshold and the opening of voltage-gated sodium channels, allowing sodium to enter the axon. B. on the axon reaching threshold and the opening of voltage-gated sodium channels, allowing sodium to leave the axon. C. on the immediate opening of voltage-gated potassium channels once threshold has been reached, allowing potassium to leave the axon. D. on the immediate opening of voltage-gated potassium channels once threshold has been reached, allowing potassium to enter the axon.

A. on the axon reaching threshold and the opening of voltage-gated sodium channels, allowing sodium to enter the axon.

which of the following occurs when a neuron is depolarized? A. Sodium ions enter the neuron through voltage-gated sodium channels. B.Sodium ions diffuse along the outside of the neuron, bringing nearby regions to threshold. C. Potassium ions enter the neuron through voltage-gated potassium channels. D. Calcium ions enter the cell through voltage-gated calcium channels.

A. sodium ions enter the neuron through voltage-gated sodium channels

transmission of impulses along a neuron in the vertebrate nervous system ordinarily occurs in only one direction because, following passage of an action potential, the neuron is temporarily in a refractory period, or hyperpolarized. This is caused by which of the following? A. the movement of potassium ions out of the axon B. the movement of potassium ions into the axon C. the movement of sodium ions out of the axon D.the movement of sodium ions into the axon

A. the movement of potassium ions out of the axon

Action potentials typically move in one direction along the neuron away from the cell body. this is due to which of the following? A. the temporary hyperpolarization of the axon membrane following the action potential spike B. the temporary inactivation of sodium and potassium channels following the action potential spike C. the movement of sodium ions out of the cell through voltage-gated potassium channels D. the myelination of the axon membrane

A. the temporary hyperpolarization of the axon membrane following the action potential spike

the sodium-potassium pump uses the energy of ______ to move ______ Na+ ions outside of the cell for every ______ K+ ions moved in

ATP, 3, 2

in vertebrates, the speed of transmission along neurons is much faster in myelinated neurons compared to unmyelinated neurons. which of the following is not true of transmission along myelinated neurons? A. Sodium and potassium channels are concentrated at nodes of Ranvier. B. Saltatory conduction in non-myelinated neurons slows the process of transmission. C. Action potentials are generated only in the nodes of Ranvier.

B. Saltatory conduction in non-myelinated neurons slows the process of transmission.

in vertebrates, the speed of transmission along a neuron can be increased by which of the following? A. the presence of additional voltage-gated sodium channels B. the presence of additional voltage-gated potassium channels C. myelinating the axon D. myelinating the dendrites

C. myelinating the axon

Which of the following determines whether or not an action potential is triggered in the postsynaptic neuron? A. the magnitude of the depolarizing excitatory postsynaptic potentials (EPSPs) B. the magnitude of the hyperpolarizing inhibitory postsynaptic potential (IPSP) C. the overall net change in membrane potential caused by the combined EPSPs and IPSPs

C. the overall net change in membrane potential caused by the combined EPSPs and IPSPs

among multicellular organisms, the simplest nervous systems are found in ___________

Cnidarians (jellyfish or sea anemones)

Stretch receptors in the knee extensor muscles stimulated by the tap of a physician's reflex hammer just below the knee cap directly triggers a nerve impulse in which of the following? A. the patellar tendon B. an motor neuron C. an interneuron D. a sensory neuron

D. a sensory neuron

When an action potential reaches the axon terminal: A. sodium ions are released from the axon terminal, enter the cell body of the postsynaptic neuron through its sodium channels, and may initiate an action potential in that neuron. B. calcium ions are released from the axon terminal, bind to and open the sodium channels on the cell body of the next neuron, and may initiate an action potential in that neuron. C. neurotransmitter molecules are released from the axon terminal, bind to and open the potassium channels on the cell body of the next neuron, and may initiate an action potential in that neuron. D. neurotransmitter molecules are released from the axon terminal and bind to receptors on the postsynaptic neuron, causing either an inhibitory hyperpolarization or an excitatory depolarization.

D. neurotransmitter molecules are released from the axon terminal and bind to receptors on the postsynaptic neuron, causing either na inhibitory hyper polarization or an excitatory depolarization

in a typical neuron, what happens during an action potential when a voltage gated potassium channel opens? A. potassium enters cell, cell depolarizes B. potassium enters cell, cell repolarizes C.potassium leaves cell, cell depolarizes D. potassium leaves cell, cell repolarizes

D. potassium leaves cell, cell repolarizes

What causes the increase in cytosolic calcium that triggers the fusion of secretory vesicles to the membrane and the release of neurotransmitters into the synaptic cleft? A. the hyperpolarization of the membrane at the axon terminal B.the release of calcium from intracellular calcium stores C. the opening of ligand-gated calcium channels in the axon terminal membrane D. the change in conformation of voltage-gated calcium channels in the axon terminal membrane

D. the change in conformation of voltage-gated calcium channels in the axon terminal membrane

Which of the following could be inhibited by greatly decreasing extracellular calcium? A. the arrival of the action potential at the presynaptic axon terminal B. the production of neurotransmitter by the presynaptic neuron C. the opening of voltage-gated calcium channels on the presynaptic axon terminal D. the fusion of secretory vesicles with the presynaptic plasma membrane

D. the fusion of secretory vesicles with the presynaptic plasma membrane

T/F the human brain has more neurons than glial cells

False, the human brain has more glial cells that neurons

neurons

Nerve cell; the basic fundamental unit of the nervous system

Place the following events in the correct order. I. opening of voltage-gated calcium channels II. change in membrane potential of the postsynaptic neuron III. fusion of secretory vesicles with the plasma membrane of the axon terminal IV. binding of neurotransmitters to receptors on the postsynaptic neuron V. increase in cytosolic calcium levels in the presynaptic neuron VI. arrival of action potential at the axon terminal of the presynaptic neuron

VI, I, V, III, IV, II

action potential

a brief electrical signal transmitted from the nerve cell body along one or more axon branches

nerves

a bundle of long fiberlike extensions from multiple nerve cells

nerve cords

a bundle of long fiberlike extensions from multiple nerve cells that serves as the central nervous system of invertebrates such as flatworms and earthworms

the binding of neurotransmitters to receptors of target cells causes

a change in electrical charge across the membrane of the receiving postsynaptic cell, continuing the signal to the second cell

membrane potential

a difference in electrical charge across the plasma membrane

dendrites

a fiberlike extension from the cell body of a neuron that receives signals from other nerve ells or from specialized sensory endings; the input end of a nerve cell

axons

a fiberlike extension from the cell body of a neuron that transmits signals away from the nerve's cell body; the output end of a nerve cell

ganglia

a group of nerve cell bodies that processes sensory information received from a local, nearby region, resulting in a signal to motor neurons that control some physiological function of the animal

synapse

a junction through which the axon terminal communicates with a neighboring cell

neurotransmitters

a molecule that conveys a signal from the end of the axon to the postsynaptic target cell

inhibitory postsynaptic potential

a negative change in the postsynaptic membrane potential

nervous system

a network of many interconnected nerve cells

explain why action potentials propagate along an axon only in a single direction

a neuron cannot fire a second action potential during a refractory period, when the inner membrane voltage falls below and then returns to resting potential. the refractory period prevents the membrane from reaching its threshold too quickly after an action potential and firing an action potential in the reverse direction

interneurons

a neuron that processes information received by sensory neurons and transmits it to motor neurons in different body regions

sensory neurons

a neuron that receives and transmits information about an animal's environment or its internal physiological state

motor neurons

a neuron that, on receiving information from interneurons, effects a response in the body

excitatory postsynaptic potential

a positive change in the membrane potential

ligan gated ion channel

a receptor that alters the flow of ions across the plasma membrane when bound by its ligands

knee-jerk extension reflex

a reflex commonly tested by physicians to evaluate peripheral nervous and muscular system functions

glial cells

a type of cell that surrounds neurons and provides them with nutrition and physical support

astrocytes

a type of star shaped glial cells that contributes to the blood-brain barrier by surrounding blood vessels in the brain and thus limiting the size of compounds that can diffuse from the blood to the brain

refractory period

after an action potential is transmitted, a brief period where the neuron is slightly more polar /negative than its resting positions

explain what is meant by saying action potentials are "all or nothing"

an action potential is said to be all or nothing because the magnitude of the action potential is always the same, regardless of the strength of the initial stimulating input

the end of each axon forms a swelling called the

axon terminal

why is protection of the brain and spinal cord critically important?

because nerve cells have limited capacity to regenerate after damage

an EPSP and an IPSP may ____________ so no action potential is set off

cancel each other out

the bulk of information processing occurs in the ___________ nervous system

central

what are reflex circuits?

circuits that connect sensory neurons directly with motor neurons

peripheral nervous system (PNS)

collectively, the sensory and motor nerves, including the cranial and spinal nerves, and interneurons and ganglia

___________ link specialized sensory organs (eyes, ears, tongue) to the brain. therefore they control eye movement, facial expression, speech and feeding

cranial nerves

the peripheral nervous system is organized into left and right sets of ______________ located within the head and ________________running from the spinal cord to the periphery

cranial nerves, spinal nerves

neurons share a common organization: they have _______ that receive inputs, a _________ that receives and sums the inputs, and ____________ that transmit signals to other nerve cells

dendrites, cell body, axon

membrane __________ makes neurons more likely to respond and transmit an action potential, whereas membrane ___________ inhibits the neuron from sending an action potential

depolarization, hyperpolarization

voluntary

describes the component of the nervous system that handles sensing and responding to external stimuli

involuntary

describes the component of the nervous system that regulates internal bodily functions

negative feedback

describes the effect in which the final product of a biochemical pathway inhibits the first step; the process in which a stimulus acts on a sensor that communicates with an effector, producing a response that opposes the initial stimulus. negative feedback is used to maintain steady conditions, or homeostasis

widely spaced out EPSPs _________ sum

do not

what are the two types of synapses?

electrical and chemical

_________ synapses tend to transmit relevant information between nerve cells, and ____________ synapses often serve to filter out unimportant information

excitatory, inhibitory

When summed over time, the ___________ determines whether the postsynaptic cell fire an action potential

frequency of synaptic stimuli

the ability to process information first evolved with the formation of:

ganglia

polarized

having opposite properties in opposite parts; describes a resting membrane potential in which there is a buildup of negatively charged ions on the inside surface of the cell's membrane and positively charge ions on the outer surface

spinal cord

in vertebrates, a central tract of neurons that passes through the vertebrae to transmit information between the brain and the periphery of the body

cranial nerves

in vertebrates, a nerve that links specialized sensory organs to the brain; most contain axons of both sensory and motor neurons

central nervous system (CNS)

in vertebrates, the brain and spinal cord; in invertebrates, centralized information-processing ganglia

what could a motor neuron trigger in the bod?

it may stimulate a muscle contraction, constrict blood vessels to adjust blood flow, or anything else that may adjust an animal's internal homeostasis

why is the evolution of cephalization so important?

it puts a concentration of sensory organs near the brain and allows animals to take in sensory information as they move ahead in the environment

in general, the organization and complexity of an animal's nervous system reflects its __________

lifestyle

the binding of some neurotransmitters depolarizes the postsynaptic membrane, making the membrane potential more positive, by opening ______________ channels and activating an excitatory postsynaptic potential

ligan gated Na+

the postsynaptic membrane receptors are called

ligan gated ion channels

the binding of neurotransmitters can hyper polarize the postsynaptic membrane, making the potential more negative through the opening of ______________ and activating an inhibitory postsynaptic potential

ligand-gated Cl- pr K+ channels (Cl- ions diffuse into the cell adn K+ ions out)

myelin

lipid rich layers or sheaths formed by glial cells that wrap around the axons of vertebrate neurons and provide electrical insulation

ion channels open and close in response to changes in ____________, underlying the production of action potentials in nerve cells

membrane voltage

at the moment that action potential has reached its maximum height, the potential (or voltage) difference across the nerve membrane is:

more positive inside than out

glial cells form lipid-rich layers or sheaths called ____________ that wrap around the axons of neurons

myelin

when no signal is present, there are more __________ ions inside the neuron cell and the inside is thus __________ charge relative to the outside

negative, negatively

in animals with an organized nervous system, information is transmitted to different regions along the length of an animal's body by distinct __________

nerve cords or nerves

how are signals transmitted from one end of a nerve cell to the other, and from one neuron to another?

nerve signals are transmitted electrically (in the form of an action potential) from one end of a neuron to the other. they are transmitted chemically (by neurotransmitters) across a synapse from one neuron to another

simply organized animals, such as cnidarians, have a nerve _________ to coordinate sensory and motor function

net

describe how neurotransmitter binding to receptors on a postsynaptic cell causes inhibition or excitation

neurotransmitters binding to receptors on the postsynaptic membrane can elicit an excitatory response if they depolarize the postsynaptic membrane. Excitatory neurotransmitters trigger the opening of Na+ channels. neurotransmitters cause inhibitory response if they bind to receptors and hyperpolarize the postsynaptic membrane. inhibitory neurotransmitters trigger the opening of Cl-, or sometime sK+ channels

how do signals cross the synaptic cleft

neurotransmitters convey the signal from the end of the axon to the postsynaptic target cell

the arrival of a nerve signal at the axon terminal triggers the release of ____________ from vesicles located in the terminal. the vesicles fuse with the axon's __________, releasing neurotransmitter molecules into the ____________.

neurotransmitters, membrane, synaptic cleft

at regular intervals, the axon membrane is exposed at sites called _____________ that lie between adjacent segments wrapped with myelin

nodes of ranvier

at rest, nerve (and muscle) cells have a greater concentration of sodium (Na+) ions ____________ the cell, and a greater concentration of potassium (K+) ions ____________ the cell

outside, inside

___________ nerves leave the CNS from the brain by cranial nerves and from lower (sacral) levels of the spinal cord

parasympathetic

nervous systems are organized into into _________ and ________ components

peripheral, central

the resulting membrane potential of a cell that is rest with no signal being received or sent is said to be ___________

polarized

under normal (resting) cellular conditions, the _______ concentration is greater inside the cell, and the plasma membrane is most permeable to ____________>

potassium, potassium

how do glial cells help neurons?

protection, glial cells also hellp orient neurons as the develop their connections, and they provide electrical insulation to vertebrate neurons that allows nerve signals to be transmitted rapidly

electrical synapses enable _________ communication, but limit the ability to ___________________

rapid, process and integrate information

the animal nervous system is made up of what three types of cells?

sensory neurons, interneurons, and motor neurons

nodes of ranvier

sites on an axon that lie between adjacent myelin-wrapper segments, where the axon membrane is exposed

__________ concentration is always higher outside the cell. during the peak of the action potential, the plasma membrane is becoming more permeable to ____________

sodium, potassium

the vertebrates, the peripheral nervous system is divided into __________ and _________ components

somatic (voluntary), autonomic (involuntary)

the central nervous system of vertebrates includes both the brain and ___________

spinal cord

____________ receive sensory information from receptors in nearby body regions along the length and send motor signals from the spinal cord back to those regions

spinal nerves

________ are the only multicellular animals that lack a nervous system

sponges

_____________ nerves leave the CNS from the middle (thoracic and lumbar) region of the spinal cord, forming ganglia along much of the length of the spinal cord

sympathetic

___________ neurons stimulate the heart to beat faster, whereas _____________ neurons cause the heart to beat slower

sympathetic, parasympathetic

the autonomic nervous system is divided into a ______________ division and a __________ division

sympathetic, parasympathetic

an axon terminal communicates with a neighboring cell through a junction called a

synapse

what separates the end of an axon of the presynaptic cell and the neighboring post synaptic cell?

synaptic cleft

reciprocal inhibition

the activation of opposing sets of muscle so that one set is inhibited as the other is activated, allowing the movement of joints such as the knee

homeostasis

the active regulation and maintenance, in animals, organs, or cells, of a stable internal physiological state in the face of a changing external environment

what happens to signals at the axon hillock?

the axon hillock determines if the signal is valid for a response and it will either be ignored or transmitted to the axon to create an action potential

brain

the centralized concentration of neurons in an organ that processes complex sensory stimuli from the environment or from anywhere in the body

cephalization

the concentration of nervous system components at one end of the body

spatial summation

the converging of multiple receptors onto a neighboring neuron, increasing its firing rate proportionally to the number of signals received

sympathetic division

the division of the autnomic nervous system that generally produces arousal adn increased activity; active in fight-or-flight response

parasympathetic divsion

the division of the autonomic nervous system that slows the heart and stimulates digestion and metabolic processes that store energy, enabling the body to "rest and digest"

temporal summation

the frequency of synaptic stimuli; the integration of sensory stimuli that are received repeated over time by the same sensory cell

autonomic nervous system

the involuntary component of the peripheral nervous system, which controls internal functions of the body such as heart rate, blood flow, digestion, excretion, and temperature

axon hillock

the junction of the nerve cell body and its axon

saltatory propagation

the movement of an action potential along a myelinated axon, "jumping" from node to node

briefly describe how myelinated axons increase the speed of signal transmission

the myelin sheath insulates the axon, spreading the charge from a local action potential over a much greater distance along the axon's length. the axon membrane is exposed at regular intervals at sites called nodes of Ranvier that lie between adjacent segments wrapped with myelin. the action potential jumps from node to node, greatly increasing the speed of transmission

resting membrane potential

the negative voltage across the membrane at rest

how could a reflex circuit help a gazelle about to be attacked?

the sensory neurons will detect the presence of a predator and directly rely that information to motor neurons that will provide a quick movement necessary to escape the predator

synaptic cleft

the space between the axon of the presynaptic cell and the neighboring postsynaptic cell

somatic nervous system

the voluntary component of the peripheral nervous system, which is made up of sensory neurons that respond to external stimuli and motor neurons that synapse with voluntary muscles

what does a nervous system allow an organism to do?

to sense and respond to the environment, coordinate action of muscles, and control the internal function of its body

T/F neurons all share some basic features

true

conscious reactions are under the control of the _____________ component of the nervous system, and unconscious ones are under the control of _____________ component

voluntary, involuntary

chemical synapses signal

when an action potential reaches the end of an axon the resulting depolarization induces voltage-gates Ca2+ ions channels to open (only found in axon terminal membrane). Ca2+ ions diffuse into axon terminal, and in response of the high Ca2+ conc the vesicle with neurotransmitters fuse with the pre synaptic membrane and release the neurotransmitter into the synaptic cleft by exocytosis. the neurotransmitters diffuse rapidly across the cleft and bind to the postsynaptic membrane receptors of the neighboring cell which will open the ion channels, causing a change in the postsynaptic cell membrane potential that allows the signal to propagate along the next neuron