Chapter 4 Flashcards
neurons always look the same
f Dif shapes and sizes
A protein is a chain of fairly simple building-block molecules called …
amino acids
how many of the 22 amino acids must we ingest in food
8
what is a node of ranvier
Uninsulated sections of the axon
REVIEW FIGURE 4.1
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what is the charge difference inside and outside the neuron
The inside of the neuron is slightly negative relative to the outside.
why is it important that neutrons are slightly negative in cell
This potential difference results from an uneven distribution of ions between the inside and outside of a cell.
what ionized molecules make for the resting potential of a cell
K + and Na +
Cl-
To understand the resting potential, we need to under-stand two things: …2
(a) The membrane potential is a relative potential—that is, we are always comparing the inside to the outside of the membrane; and (b) the outside of the membrane is always considered equal to zero.
of K, A, Cl and Na which are more inside or outside the cell
more K and A inside cell
3 passive processes?
diffusion, electrostatic charge and differential permiability
what is differential permeability
The only way ions can move into and out of the cell is through thousands of these specialized protein channels called ionophores or ion channels. These proteins are often a target of behav-iorally active drugs.
K+ and Cl–ions cross the cell membrane by easily passing through these channels, but tend to maintain their relative concentrations ..why?
inside and outside the cell (respectively) because the forces of diffusion and electrostatic charge off-set each other,
does A ever move in or out of cell
no too big
passively there is more Na inside the cell
t active t keeps it out (3 na out for every 1 k in
The resting potential of a neuron describes the …
distribution of ions in the absence of stimulation, but this membrane potential can vary substantially in response to a variety of stimuli.
When the membrane potential becomes less negative (i.e., moves toward zero and positive numbers), it is called…
depolarization
When the membrane potential becomes more negative (i.e., moves further away from zero), it is called ….
hyperpolarization.
what’s a cells normal resting potential
-70 mV
if the neuron is depolarized to about −55 mV, called the …, the entire resting potential and the processes that maintain it break down.
threshold
why does breakdown occur at threshold
because of special gated ion channels that are sensitive to the number of positive charges inside the cell. When the potential difference is reduced beyond the threshold, these voltage-gated ion channels open, allowing the free flow of ions across the membrane.
At this point, Na+ channels close, mark-ing the end of the … of the action potential. K+ channels remain open, and the efflux (outflow) of K+ continues; this is called the … phase of the action potential.
rising phase
repolarization
This breakdown and restoration of the resting poten-tial is known as an …., and it occurs very quickly.
action potential
how many ap can occur per second
thousands
The term … is often used to indicate the occurrence of an action potential
firing
where is an action potential generated
section of the neuron’s axon that lies adjacent to the axon hillock
The Na+ ions that move into the cell through ion channels also move sideways along the inside surface of the membrane. This passive movement, due to diffusion and electric charge, what does this do to resting potential
reduces the resting potential of the surrounding membrane
what does it mean to say APs are nondecremental
they reach the axon terminal with the same strength as which they were ini-tiated near the axon hillock.
what is the jumping of AP called
saltatory conduction
how fast can APs move
120 meters per second
APs are always the same
t as long as stimulations is strong enough to depolarize cell at threshold = all or none law
if all action potentials are the same, how does a neuron convey information about the strength of the stimulus depolarizing it?
rate at which action potentials are generated. If a depolarizing stimulus is applied continuously to a cell, it will cause the cell to produce repeated action poten-tials
Therefore, the stronger the … stimulus, the faster the membrane will fire. This principle is called the …
depolarizing
rate law.
why is AP all or nothing
The action potential is invariable in axons because axons have only voltage-gated ion chan-nels and nothing else that can modulate the effect of depolarization
Because the consequence of this disturbance is variable, we refer to depolarization in the cell body and dendrites as …, rather than action potentials
graded or postsynaptic potentials (PSPs)
The intensity of PSPs is propor-tional to the magnitude of the disturbance; however, this intensity decreases as the …
distance from the site of stim-ulation lengthens
where?: where variable PSPs have the potential to be converted to unvarying action potentials.
The region of the axon adjacent to the axon hillock is the place
If stimulation of dendrites or the cell body results in the opening of voltage-gated Na+ channels what will result
depolarization = excitatory postsynaptic potential (EPSP)
the more the cell is depolarized past its threshold, the … it will fire.
faster
If stimulation of dendrites or the cell body results in the opening of voltage-gated K+ chan-nels, K+ ions will rush out of the cell and the resting potential will increase or opening of voltage-gated Cl–channels;:T
hyper polarized = harder to produce AP
inhibitory postsynaptic potential (IPSP).
There are two major types of integration of signals in neurons: …`
(a) temporal summation and (b) spatial summatio
Temporal summation occurs when a neuron experi-ences …
several PSPs closely in time
Spatial summation occurs when two or more PSPs occur in …
close proximity on a neuron.
The neuron may have Na+ ions entering in some regions (…) and Cl–ions entering or K+ ions leav-ing in other regions (…).
excitation
inhibition
what determines if voltage gated Na+, K+, or Cl–channels will open
Opening of these ion channels is controlled by activation of various receptor subtypes by neurotransmitter chemicals
figure 4.4
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Where do natural action potentials come from?
the outside world =sensory receptor neutrons
do neuron membranes touch ever
no but can happen in other tissues
Information is transferred between neurons at …
syn-apses.
Synapses are most frequently located between terminal buttons and dendrites (…) or between terminal buttons and cell bodies (….). They may also be located on or near another neuron’s axon or terminal buttons (…), thereby allowing one neuron to modulate another neuron’s influence on the postsynaptic cell
axodendritic synapses
axosomatic synapses
axoaxonic synapses
Synap-tic vesicles are more densely packed in the … of the terminal button where there also exist many voltage-gated calcium (Ca2+) channels
release zone
Upon arrival of an action potential, these channels open, permitting an influx of Ca2+ ions into the terminal button. Ca2+ influx triggers ….
the movement and fusion of synaptic vesicles with the pre-synaptic membrane and the exocytosis of neurotransmit-ter.
neurtransmitters can be secreted from regions along the axon in the general vicinity of a number of cells and diffuse to their synapses where they influence the activity of many cells at the same time
t
A .. is a chemi-cal that is synthesized and released by neurons and that modulates the effects of neurotransmitters
neuromodulator
Neuromodulators or NT are typically released in greater amounts and travel further distances
neuromod
Substances that act as neurotransmitters at one synapse may also act as neuromodulators at a differ-ent synapse.
t
A … is a special-ized protein that spans the membrane of the postsynaptic cell and contains a binding site to which a specific neu-rotransmitter molecule can briefly attach
receptor, receptor site, or receptor complex
each neurotransmitter mole-cule must have only one receptor to which it can bind
F often many different receptor subtypes to which a particular neurotransmitter molecule can bind
T: In some synapses, postsyn-aptic receptor proteins contain binding sites directly con-nected to a gated ion channel
IONOTROPIC receptors
The binding sites on …. are not directly connected to an ion channel. Instead, receptor sites are situated on the extracellular portion of a long signal protein that weaves its way back and forth seven times across the cell membrane
metabotropic recep-tors
metabolic: … are composed of subunits that, when the receptor is in an inac-tive state, are bound together.
G proteins
explain what happens during metetrobic reception
Some neurotransmitter molecules bind to receptors on membrane signal proteins, which are linked to G proteins. When a neurotransmitter molecule binds to a metabotropic receptor, a subunit of the G protein breaks off into the neuron and either binds to an ion channel or stimulates the synthesis of a second messenger.
figure 4.5
?
metabotrophic: the subunit may initiate a biochemical (enzymatic) reac-tion that leads to the synthesis of another molecule called a …
second messenger (neurotransmitters are considered first messengers).
what are the 3 ways second messangers work
Often, a second messenger interacts with gated ion chan-nels from inside the cell with similar but stronger and more long-lasting effects, compared to those of directly gated ion channels. Or, the second messenger can alter the operation of nongated ion channels in a way that changes the resting potential or the cell’s sensitivity to other stimuli.
release of a second mes-senger may lead to even longer-term or permanent effects because it can activate a type of protein called a …
kinase.
what are kinases
Kinases are enzymes that alter the functioning of other proteins, including ion chan-nels and receptors, and they do so for a much longer time than do second messengers.
how long will a kinase last
can remain active for many minutes or even hours.
The proteins created by the DNA could be …3 or any of the other molecules used by the cell in receiving and trans-mitting information
receptor sites, ion channels, ion pumps,
Patterns of gene activa-tion and silencing are known as the …, and the study of their influence on behavior and health is a hot field of research called …
epigenome
epigenetics
.T:stretches of DNA that determine whether a particular gene is expressed to initiate and regulate protein production.
enhancers or promotors—
what ultimately controls the expression of particular genes in the cell
transcription factors which bind directly to the “switches” to activate or repress tran-scription of a gene
what is it that arises from changes in gene expression that can be very long-lasting and are thought to be responsible for the formation and storage of memories in the brain.
Changes in neuron excitation or sensitivity
a type of metabotropic receptor. Receptor sites for neurotransmit-ters are located not only on the postsynaptic neuron but also on the presynaptic neuron:T
autoreceptors
how do auto receptors work on antidepressants
(regulate its levels through the activity of G proteins and second messengers)
Antidepressants produce a buildup of crucial neurotransmitters, but autoreceptors detect this excess and reduce production and release of the neu-rotransmitter molecules, thus blocking the effectiveness of the drug.
why do antidepressants start working after a few weeks
takes a few weeks to exhaust the autoreceptors before the drug can make changes in the functioning of the synapse.
T: The release of neurotrans-mitters from the presynaptic cell to alter the excit-ability of a postsynaptic cell most common communication method
heteroreceptors
hetero: from post to pre cell These are metabotropic receptor sites that func-tion very similarly to autoreceptors except that they respond, not to the release of neurotransmitter by the cell upon which they reside, but to …
chemicals released by the postsynaptic cell or other nearby cells when they become depolarized.
This transmission of chemi-cal information from a postsynaptic to a presynaptic cell is termed ….
retrograde signaling
2 ways of terminating synaptic action
reuptake
enzymatic degradation or deactivation
define reuptake
most common : (a) The presynaptic cell may quickly reabsorb the intact neurotransmitter mole-cule, taking it back into the cytoplasm of the terminal button where it gets repackaged into vesicles (which also get recycled) for future use
2 things at work during reuptake
glial cells and transporter proteins
explain enzymatic degradation or deactivation
The synapse may contain an enzyme, produced in and released from the same neuron as the neurotransmitter breaks the neurotransmitter into its precursors (constituent parts), which may also be taken back into the presynaptic cell to be remanufactured for future release
In the PNS, these groups of cell bodies are called …., and the bundles of axons are called nerves
ganglia (singular is ganglion)
In the CNS, the cell body groups are called … or centers, and the bundles of axons are called …
nuclei (singular is nucleus)
tracts
what makes up white and grey matter
Because axons are gener-ally covered with myelin, which is white, the nerves and tracts are called white matter. The unmyelinated cell bodies are called gray matter.
reuptake and is accomplished by a specialized mechanism that actively employs … molecules embedded in the membrane of the pre-synaptic cell.
transporter protein
what does the somatic NS do
how the brain and spinal cord recieve info from and allow us to interact with our enviro
where are the cell bodies of motor neurons
in the CNS= spinal cord
what nervous system contains the motor nerves
The somatic nervous system also contains the motor nerves
what kind of nerves are in the somatic system
motor, cranial
… is the transmitter at most neuromuscular junc-tions in the somatic system, and the receptor sites are of the nicotinic cholinergic type.
Acetylcho-line (ACh)
what do cranial nerves do
which are attached to the undersurface of the brain. Mostly, these nerves convey motor commands and/or sensory information to and from areas of the face and neck.
is somatic carrying to or from
to CNS
what is the autonomic NS in charge of
the autonomic nervous sys-tem is concerned with sensory information that we are usually unaware of
examples of autonomic info?
information about blood pressure and blood gases, the functioning of organs, and levels of hormones.
does somatic or automatic control the systems we have conscious control over
somatic system usually com-mands muscles over which we have voluntary control, the autonomic nervous system commands the muscles of the heart and intestines, the secretions of glands, and other regulatory systems over which we normally have no conscious control.
what are the 2 divisions of the ANS
parasympathetic and sympathetic division
T: generally keeps the internal functioning of the body running smoothly and calmly, in a rest-and-digest mode of operation
parasympa
The parasympathetic and sympathetic divisions of the autonomic nervous system are anatomically, function-ally, and neurochemically distinct.
t
where do the cell bodies of parasympathetic neuron originate
sacral region of spinal cord and cranial nerves
cell bodies of the sympathetic division originate in the …
tho-racic and lumbar regions of the spinal cord
The parasym-pathetic system uses… as a transmitter to control glands and muscles
ACh
what system are atropine drops in eyes that dilate pupils blocking
para system
