Physiology: Membrane Potentials, Neuronal Signaling, Basic Physiology, and Hormonal Control

Fill-in-the-blank practice flashcards covering electricity, resting membrane potentials, graded and action potentials, diffusion/osmosis, cell membrane properties, and hormonal signaling mechanism from physiology lecture notes.

Separated electrical charges of opposite sign have the potential to do work, which is defined as __________.

electrical potential

The average resting membrane potential across the plasma membrane of a typical cell is __________.

$$-70\,mV$$

The resting membrane potential exists because of a tiny excess of __________ ions inside the cell and positive ions outside the cell.

negative

The extracellular concentration of $Na^+$ is __________ $mM$, while its intracellular concentration is __________ $mM$.

$145\,mM$ and $15\,mM$

The extracellular concentration of $K^+$ is __________ $mM$, while its intracellular concentration is __________ $mM$.

$5\,mM$ and $150\,mM$

The $Na^+/K^+$ ATPase pump maintains ion concentration gradients by pumping __________ $Na^+$ ions out of the cell and __________ $K^+$ ions into the cell per ATP molecule.

$3\,Na^+$ and $2\,K^+$

Resting membrane potential is predominantly generated and maintained by leak channels for __________ ions.

$$K^+$$

A cell membrane is __________ when its potential becomes less negative than the resting potential.

depolarized

The phase of an action potential in which the membrane potential becomes positive relative to the outside is termed an __________.

overshoot

A membrane is __________ when it returns to its resting membrane potential following depolarization.

repolarized

A membrane is __________ when its potential becomes more negative than its resting potential.

hyperpolarized

Graded potentials are initiated by __________-gated or mechanically gated protein channels.

ligand

Graded potentials decrease in magnitude as they move away from the site of initial depolarization due to the leakage of charge, predominantly __________, across the plasma membrane.

$$K^+$$

Upon membrane depolarization, voltage-gated $Na^+$ channels open quickly and then __________ very rapidly.

inactivate

Voltage-gated $K^+$ channels open __________ upon depolarization and close slowly upon repolarization.

slowly

To trigger an action potential positive feedback loop, a depolarizing stimulus must reach a minimum level known as the __________.

threshold potential

The threshold potential required to initiate an action potential is typically about __________ $mV$ more positive than the resting potential.

$$15\,mV$$

During the __________ refractory period, a second stimulus cannot produce an action potential regardless of its strength because $Na^+$ channels are open or inactivated.

absolute

During the __________ refractory period, a second action potential can be produced only if the stimulus strength is considerably greater than usual.

relative

The relative refractory period can last as long as __________ milliseconds and roughly coincides with after-hyperpolarization.

$$15\,ms$$

In myelinated nerve fibers, action potentials appear to jump from one node to the next in a process called __________ conduction.

saltatory

Action potentials occur only at the __________, where the myelin sheath is interrupted and the concentration of voltage-gated $Na^+$ channels is high.

nodes of Ranvier

Action potentials propagate faster along axons with larger fiber diameters because larger fibers offer less __________ to local current flow.

resistance

Boyle's Law states that pressure is __________ to volume in a closed system at constant temperature, represented as $P_1V_1 = P_2V_2$.

inversely proportional

Diffusion is the movement of a solute down its concentration gradient, whereas __________ is the diffusion of water across a semipermeable membrane.

osmosis

Diffusion times increase in proportion to the __________ of the distance over which molecules diffuse.

square

Substances that cannot cross the plasma membrane are referred to as __________ solutes.

nonpenetrating

An __________ solution has the same concentration of nonpenetrating solutes as normal extracellular fluid.

isotonic

A red blood cell placed in a __________ solution will swell due to net water movement into the cell.

hypotonic

Phospholipid molecules are described as __________ because they contain both polar hydrophilic heads and non-polar hydrophobic tails.

amphipathic

Ion channels that open or close in response to physical deformation or pressure are called __________ ion channels.

mechanically gated

An acid is defined as a proton donor that increases the __________ concentration of a solution.

$$H^+$$

In any aqueous solution at $25\,^\circ\text{C}$, the product of $[H^+]$ and $[OH^-]$ is constant and equals __________.

$$10^{-14}$$

The physiological pH range of extracellular fluid in the human body is maintained between __________.

$$7.35\text{--}7.45$$

Intracellular fluid accounts for approximately __________ of total body fluid in the human body.

$$67\%$$

The surface of an epithelial cell facing a hollow tube or lumen is called the __________ membrane.

apical

Homeostasis is defined as a maintained state of __________ constancy.

dynamic

Chemical messengers that exert their physiological effects on the exact same cells that secreted them are called __________.

autocrines

Locally acting chemicals that affect cells other than those that secretes them are called __________.

paracrines

Amine hormones are derivatives of the amino acid __________.

tyrosine

Water-soluble amine hormones derived from tyrosine, such as epinephrine, norepinephrine, and dopamine, are collectively called __________.

catecholamines

Steroid hormones are lipid-soluble hormones synthesized from __________.

cholesterol

Because water-soluble peptide and catecholamine hormones cannot cross the plasma membrane, they bind transmembrane receptors linked to second-messenger systems via a __________.

G protein

Lipid-soluble steroid and thyroid hormones bind intracellular receptors to form complexes that enter the nucleus and bind specific regions of __________.

DNA

When target cells form more receptors in response to low levels of a hormone, the process is called __________.

up-regulation

The hormonal interaction in which one hormone cannot exert its full effects without the presence of a second hormone is called __________.

permissiveness

As illustrated in the diagram, epinephrine alone releases a small amount of fatty acids, but in the presence of thyroid hormone, fatty acid release is greatly enhanced due to _________.

permissiveness

The interaction in which more than one hormone produces the same effect on a target cell, resulting in amplification, is called __________.

synergism

During labor, the head of the baby pushing against the cervix stimulates nerve impulses that cause oxytocin release, which enhances uterine contractions in a __________ feedback loop.

positive

An endocrine disorder characterized by decreased responsiveness of target cells to a hormone is classified as __________.

hyporesponsiveness