Exam 1 Flashcards
For extrinsic control systems, the sensor and integrator components will ALWAYS involve
the nervous system and/or endocrine system system
Which of the following transporters would be ‘electrogenic’
One that transports one Ca2+ out of the cell and one Na+ into the cell
Graded potentials and action potentials
propagate along the plasma membrane from where they begin by current flowing along the membrane to adjacent regions that have a different membrane potential
The rate at which Na+ diffuses across an axon’s plasma membrane can increase greatly
Once the threshold is reached
Suppose that the presynaptic neurons A,B, and C converge to communicate with postsynaptic neurons neuron D. Furthermore, suppose that when neurons A and B are active, neuron D exhibits lower action potential frequency than when only B is active. When all three presynaptic neurons are active, neuron D generates no action potential. Given this, which of the following must be true?
Neurons A and C elicit inhibitory responses while neuron B has an excitatory response.
During the first phase of an action potential where it approaches a ‘peak’
the net electrochemical force acting on Na+ is less than at the resting potential
As interstitial fluid begins to accumulate in one area of the body, it is returned to ____ by ____
the plasma; lymphatic vessels
Hypokalemia is a condition in which someone has an abnormally low concentration of K+ in the ECF. How could this condition impair neural function?
This could result in hyperpolarization by increasing the net electrochemical force acting on K+.
The Nernst equation
predicts the membrane potential at which an ion reaches equilibrium
Regulating the concentration of a solute within ____ is more important than its regulation within ____ because the former process will affect the solute’s concentration in all organs, whereas the latter process will not.
the plasma; an organ
What sub-types of channels are preferentially found at high density in the dendrites but not within other regions of a neuron?
stimulus-gated channels that are not voltage-gated
IPSP
reduces the probability of that postsynaptic neurons will reach threshold
Suppose that depolarizing current #1 reaches the axon hillock such that it depolarizes this region from the resting potential (-70mv) by +30 mv for a short period of time and then shortly thereafter depolarizing current #2 reaches the axon hillock such that it depolarizes this region by +50mv. Which of the following is true?
Both currents will trigger action potentials, but the frequency resulting from current #1 will be less than that from current #2.
The convergence of two or more distinct graded potentials in a neuron on the ____ results in ____
axon hillock; spatial summation
The Na+/K+ pump
hydrolyzes ATP to move both Na+ and K+ against their favorable gradient
Homeostasis is
maintained by organs and body systems that operate as negative feedback loops.
If a 2% NaCl solution is is prepared, then the concentration of NaCl is
20mg/mL
Assume than an antiporter within the red blood cell plasma membrane moves HCO3- from the plasma into the red blood cell. assume the same antiporter moves Cl- across the plasma membrane.
HCO3- transport is driving the unfavorable transport of Cl-
Orthodromic conduction
refers to the movement of action potentials from the axon hillock to the axon terminals
At the resting membrane potential, the net electrochemical force acting on Na+
is larger than either the chemical or electrical force acting on this ion
Physiological variables such as blood pressure and O2 tend to fluctuate around a specific value referred to as
the set point
Activation of the voltage-gated ____ channels trigger ____
Ca2+; synaptic vesicle exocytosis
Interstitial fluid
has a much higher concentration of Na+ than K+
If an ion moves across the plasma membrane from a fluid where its concentration is low to a fluid where its concentration is high, then
its movement must have occurred through an ion channel
Transduction of stimulus intensity within a dendrite
is possible because the stimulus intensity determines the percentage of specialized gated channels which switch from the close to open state.
Intracellular fluid
has a higher concentration of K+ than extracellular fluid
The Na+/K+ pump
functions to maintain the Na+/K+ concentration gradients across the plasma membrane
The plasma membrane of an unstimulated neuron
differs in its permeability to Na+ and K+ because of the density of leak channels
Synaptic communication
involves Ca2+ influx into the axon terminal
The velocity of action potential conduction
depends on the diameter of the axon
Many neurons have Na+-Ca2+ secondary active transporters in their plasma membrane. The transporter moves Na+ from the interstitial fluid to the cytoplasm. Knowing this, Ca2+ must be transported ___ so this transporter must be a ____
against its favorable gradient; antiporter
If a voltmeter that measures the plasma membrane potential reads +30mv then
Na+ is closer to its equilibrium potential than K+ is to its equilibrium potential
In neurons, action potentials are first initiated
when a depolarizing current enters the axon hillock
Inactivation
is responsible for the absolute refractory period of action potentials
Neurons communicate information about stimulus intensity over the long distance of an axon
by the frequency of action potentials occuring
Excitable cells
are those capable of generating action potentials
When ONE action potential occurs presynaptically at an excitatory synapse
are those capable of generating action potentials
Neurotransmitter reuptake
occurs by secondary active transport
Neurotransmitter release can trigger postsynaptic responses
by their interaction with ligand-gated channels
If the membrane potential measured with a voltmeter is the same as that predicted by the Nernst equation for a hypothetical X having a higher concentration inside the cell than outside the cell,
X+ is at equilibrium
Which is true of action potentials
the magnitude of each action potential produced by a neuron is constant
The stomach contains glands that secrete an acidic fluid and the enzyme pepsin to help digest food within the stomach lumen. The glands in the stomach are classified as
epithelial tissue
Neurons that communicate information about physiological variables within the blood or internal organs
are classified as visceral afferents
A physiological saline solution
contains 150 mM NaCl
If a postsynaptic neuron’s activity is 50 Hz, then
it generates 50 action potentials per second
A regulatory system
a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions
Neurons that propagate action potentials away from the CNS
are efferent neurons
Metabotropic receptors
transiently interact with G proteins once activated
A threshold potential is
the membrane potential at which voltage-gated channels open
A chemical messenger released by non-excitable cells that does not enter the blood
is classified as a paracrine factor
If a postsynaptic neuron hyperpolarizes in response to a neurotransmitter release, this change in membrane potential is specifically referred to as _____
inhibitory post synaptic potential
Stimulus-gated channels that do not respond to changes in the membrane potential are primarily restricted to the ___ and the ____ regions of a neuron
dendrites; cell body
Physiology
the study of all function that occur within an organism
Antidromic conduction occurs when
action potentials move from axon terminals toward the axon hilock in a non-physiological direction
Neurons that have all of their morphological components within the CNS are referred to as
interneurons
Spatial summation refers to
action potentials that occur in two or more presynaptic neurons within a short time period
this period affects the net graded potential at the axon hillock
Myelin sheaths are formed by ___ and ___ in which both are glial cells
oligodendrocytes
schwann cells
What are factors that determine if a synapse is excitatory or inhibitory?
- the type of neurotransmitter released by the presynaptic neuron
- the type of receptor found in the presynaptic neuron
- if the receptor is a GPCR – type of G protein in the postsynaptic neuron
- if the receptor is a GPCR – types of ion channels
Explain how neurons have the ability to detect stimulus, what specifically happens in the process of detection? Once detected, how do neurons intially transduce information
- Neurons are able to detect stimulus due to specialized stimulus gated channels in dendrites. Closed if stimulus is not present; open if present.
- Neurons transduce informtion about stimulus intensity and stimulus duration. Graded potential varies in magnitude and duration.
- GP magnitude varies with intensity due to stimulus intensity. The amount of open channels affect the change in membrane permeability.
- Stimulus duration depends on affects how long the gated channels remain open. This also affects the membrane permeability in which the the longevity of the the change and diffusion of ions.
