S-words

Question 1

saltatory conduction

Answer 1

the propagation of APs from myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of APs

Question 2

sarcolemma

Answer 2

membrane of the muscle fiber

Question 3

sarcomere

Answer 3

basic unit of striated muscle tissue

Question 4

sarcoplasm

Answer 4

cytoplasm of the muscle fiber

Question 5

sarcoplasmic reticulum

Answer 5

similar to the smooth endoplasmic reticulum, the sarcoplasmic reticulum stores calcium ions and pumps them out into the sarcoplasm when the muscle fiber is stimulated

Question 6

scalar electrocardiogram

Answer 6

signal measured in any of the Einthoven leads, corresponding to the projection of the electrical vector of the heart onto a line connecting two electrodes, thus transforming the vector into a scalar variable

Question 7

Schwann cell

Answer 7

glia cell forming the myelin sheath around the periphery (external surface) of axons

Question 8

second messengers

Answer 8

small molecules whose concentration changes after the first messenger attaches to the membrane receptor

Question 9

secondary structure of proteins

Answer 9

regular structures of peptide chains stabilized by hydrogen bonds (alpha helix, beta sheet)

Question 10

semilunar valves

Answer 10

valves at the opening of the aorta and pulmonary artery

Question 11

semipermeable membrane

Answer 11

membrane separating two solutions, permeable to only some of the solvents

Question 12

septum

Answer 12

muscular tissue separating the left and right atria and ventricle

Question 13

side chain

Answer 13

a group bond to the carbon atom of amino acids

Question 14

sinoatrial node

Answer 14

specialized cardiac tissue in the right atrium acting as the pacemaker of the heart

Question 15

sliding filament hypothesis

Answer 15

theory explaining muscle contraction by the sliding of actin and myosin filaments on each other

Question 16

space constant

Answer 16

externally induced and electronically conducted potential changes in the membrane decrease to 37% after traveling a distance equal to the space constant

Question 17

specificity

Answer 17

due to its spatial structure, a receptor, enzyme or transporter molecule can only bind a limited number of substrate molecules

Question 18

spirometer

Answer 18

device used to measure lung volumes and aspects of breathing

Question 19

Starling’s hypothesis

Answer 19

theory used to explain the production and absorption of interstitial fluid

Question 20

strength (energy) of a bond

Answer 20

energy released during the formation of the given bonds between atoms, which is needed to break apart the atoms

Question 21

sucrose

Answer 21

built up of glucose and fructose, most common commercially available sweetener

Question 22

summation

Answer 22

adding up the effects of two synaptic potentials occurring at the same synapse with short delay, or in neighboring synapses concurrently

Question 23

surface active agent

Answer 23

amphipathic molecule bearing both hydrophilic and hydrophobic groups

Question 24

surface active substance

Answer 24

its molecules possess both hydrophilic and hydrophobic parts and they tend to line up at the border separating two different phases with the hydrophilic and hydrophobic parts located in the appropriate phase

Question 25

surfactant

Answer 25

surface active agent lining the inner surface of the alveoli and decreasing surface tension

Question 26

saturation

Answer 26

characteristic feature of protein mediated transport processes – if the concentration of the molecules to be transported increases, the speed of the transport decreases, as most of the transporter molecules tend to be occupied after a certain concentration

Question 27

systole

Answer 27

the part of the cardiac cycle when the heart contracts