physio test TEST module 1 & 2

the surface of a dendrite is lined with specialized junctions through which the dendrite receives information from other neurons. what are these junctions called?​

​synaptic receptors

sherrington deduced that transmission at a synapse must be slower than conduction along an axon. this was based on what kind of evidence?​

​the speed of reflexive responses

what leads to korsakoff's syndrome?​

​thiamine deficiency due to chronic alcoholism

temporal summation is to ____ as spatial summation is to ____?

​time, location

the circuit from sensory neuron to muscle response is called ____?

a reflex arc

ordinarily, stimulation of a neuron takes place ___?

at the synapse

what do temporal summation and spatial summation have in common?​

both enable a reflex to occur in response to weak stimuli

when a neuron is at rest, what is primarily responsible for moving potassium ions into the cell?​

both the sodium-potassium pump and electrical gradient

if you were to accidentally touch a hot stove with your hand, you would quickly pull your hand away. the information carried to the muscles in your arm to make them contract was carried by ____?

efferent neurons

the anterior pituitary is composed of ____ and the posterior pituitary is composed of ____?​

glandular tissue, neural tissue

inhibitory synapses on a neuron ____?

hyperpolarize the postsynaptic cell

under which conditions would the sodium-potassium pump likely be far less effective in creating a concentration gradient?​

if selective permeability of the membrane did not exist

many neurons release neuropeptides mostly from the ____?

in general, a single neuron releases ____ neurotransmitter(s) and can respond to ____ neurotransmitter(s)

glutamate opens sodium gates, enabling sodium ions to enter the postsynaptic cell. what type of effect is this?​

ionotropic

a receptor can directly open a channel and thereby exert a(n) ____ effect, or it can produce slower but longer ____ effect?

ionotropic, metabotropic

what is the function of the enzyme acetylcholinesterase?​

it breaks acetylcholine down into components for recycling

the resting potential is mainly the result of ____?

negatively charged proteins inside the cell

the two basic kinds of cells in the nervous system are _____?

neurons and glia

____ in the brain and spinal cord and ____ in the periphery are specialized types of glia that build the myelin sheaths that surround neurons?

oligodendrocyte, schwann cells

when a neuron's membrane is at rest, the concentration gradient tends to move potassium ____ the cell and the electrical gradient tends to move it ____ the cell?

out of, into

voltage-activated channels are channels for which a change in the voltage across the membrane alters their ____?

permeability

which category of chemicals includes adenosine and several of its derivatives?

purines

at the peak of the action potential, the electrical gradient of potassium ____?

pushes potassium out of the cell

which type of glia builds myelin sheaths around axons in the periphery of the body?​

schwann cells

compared to ionotropic effects, metabotropic effects are ____?

slower and longer lasting

what occurs when depolarization is less than the cell's threshold?

sodium crosses the membrane only slightly more than usua

what is the primary difference between temporal summation and spatial summation?​

spatial summation depends on contributions from more than one sensory neuron

which of the following is an advantage of having a resting potential?​

the cell is prepared to respond quickly to a stimulus

what determines whether a neuron has an action potential?​

the combined effects of EPSPs and IPSPs

what is the synaptic cleft?​

the gap between the presynaptic neuron and the postsynaptic neuron

which of the following describes the transmission of information in a local neuron?​

the signal decreases in strength as it travels

why is the speed of conduction through a reflex arc slower than the speed of conduction of an action potential along an axon?​

transmission between neurons at synapses is slower than along axons

the presynaptic terminal stores high concentrations of neurotransmitter molecules in ____?

vesicles

a normal, healthy animal never contracts the flexor muscles and the extensor muscles of the same leg at the same time. why not?​

when the interneuron sends excitatory messages to one, inhibitory messages go to the other

what is the approximate resting potential of the inside of a neuron's membrane, relative to the outside?​

-70 millivolts

graded depolarization is known as an ____?

EPSP

the primary difference between an EPSP and an action potential is that ____?

EPSPs are subthreshold events that decay over time and space

a temporary hyperpolarization is known as an ____?

IPSP

the all-or-none law states that?

a neuron produces an action potential of maximal strength, or none at all

adrenocorticotropic hormone (ACTH) controls secretions of the ____?

adrenal cortex

when the neuronal membrane is at rest, the sodium channels ____?

are closed, so there is almost no flow of sodium

which type of glia release chemicals that modify the activity of neighboring neurons?​

astrocytes

a drug that blocks the sodium gates of a neuron's membrane will?

block the action potential

when a membrane is at rest, what attracts sodium ions to the inside of the cell?​

both an electrical gradient and a concentration gradient

a metabotropic synapse, by way of its second messenger, ____?

can influence activity in much or all of the postsynaptic cell

you are eating a food containing tryptophan. what can you consume with it to increase its entry to the brain?​

carbohydrates

water, oxygen, and ____ most freely flow across a cell membrane?

carbon dioxide

the branching fibers that form the information-receiving pole of the nerve cells are called _____?

dendrites

an EPSP is to ____ as an IPSP is to ____?

depolarization, hyperpolarization

the concentration gradient refers to the ____?

difference in distribution for various ions between the inside and outside of the membrane

a neuron excretes neurotransmitters through its membrane by a process called ____?

exocytosis

which action would depolarize a neuron?​

increasing membrane permeability to sodium

what happens to acetylcholine after it attaches to a receptor on the postsynaptic cell?​

it is broken down into two components

the insulating material that covers many vertebrate axons is called the ____?

myelin sheath

which neurotransmitter is released by stimulated neurons to dilate the blood vessels?​

nitric oxide

why do neurons rely so heavily on glucose as their source of nutrition?​

other fuels do not readily cross the blood-brain barrier

local anesthetic drugs attach to the sodium channels of the membrane, which ____?

prevents sodium ions from entering and stopping action potential

small, charged molecules can cross the cell membrane through ____?

protein channels

what is the proper ordering of a reflex arc?​

sensory neuron, interneuron, motor neuron

in general, a single neuron releases ____ neurotransmitter(s) and can respond to ____ neurotransmitter(s)?

several, many

neurons differ most strongly from other body cells in their ____

shape

what happens when a neurotransmitter is released by a presynaptic cell?​

the neurotransmitter passively spreads across the synaptic cleft

what causes an EPSP?​

the opening of sodium channels

although slower than an action potential, synaptic transmission is still relatively fast because ____?

the synaptic cleft is very narrow

what do dopamine, norepinephrine, and epinephrine share in common?​

they are all synthesized from the same amino acids

which statement is TRUE of EPSPs?​

they decay over time and space

when a vertebrate animal contracts the flexor muscles of a leg, it relaxes the extensor muscles of the same leg. sherrington considered this evidence for the existence of ____?

​inhibitory messages

ionotropic effects are characterized by ____?

​rapid and short-lived effects

the cell membrane is composed of two layers of _____?

​fat

many dendrites contain short outgrowths called spines that _____?

​increase the surface area available for synapses

the main advantage of a neuron releasing more than one neurotransmitter is that?

​it can send more complex messages

the "spontaneous firing rate" of a neuron refers to ____?

​its rate of producing action potentials even when it is not stimulated

spatial summation refers to ____?

​multiple weak stimulations that occur at the same time

the endoplasmic reticulum is a ____?

​network of thin tubes that transport newly synthesized proteins

autoreceptors monitor the ____?

amount of neurotransmitter released

presynaptic terminal is also known as ____.?

an end bulb

the action potential of a neuron depends mostly on what movement of ions?​

sodium ions entering the cell

the basic building blocks for the majority of neurotransmitters are ____?

​amino acids

"second messengers" carry their messages to ____?

​areas within the postsynaptic cell

loewi demonstrated that synapses operate by the release of chemicals by ____?

​collecting fluid from a stimulated frog's heart, transferring it to another frog's heart, and measuring that heart rate

the speed of an action potential down an unmyelinated axon is best described as ____?

​faster in thick axons than in thin ones

what is the main source of nutrition for vertebrate neurons?​

​glucose

korsakoff's syndrome ____?

​is marked by severe memory impairments

which pattern of post-synaptic excitation will most likely result in an action potential?​

​rapid sequence of EPSPs

what structure is composed of two layers of fat molecules that are free to flow around one another?​

​the membrane