L

Question 1

Lactation

Answer 1

Production and release of milk from the mammalian mammary gland.

Question 2

Lagena

Answer 2

An extension of the saccule of the inner ear of vertebrates; small in reptiles and amphibians but extended to form the cochlear duct in birds and the cochlea in mammals.

Question 3

Lamella

Answer 3

A general term referring to a morphology that resembles stacks of leaves.

Question 4

Lamellipodia

Answer 4

Flat, sheet-like extensions of the cell, supported by the actin cytoskeleton.

Question 5

Laminar Flow

Answer 5

A pattern in which the layers of fluid move in parallel, usually relative to the surface of an object.

Question 6

Larva

Answer 6

A pre-adult developmental stage that bears little resemblance to the adult form.

Question 7

Latch State

Answer 7

A condition in smooth muscle in which force is generated with less than expected ATP consumption; usually attributed to a more efficient mechanism of crossbridge cycling.

Question 8

Lateral Inhibition

Answer 8

Process by which a sensory stimulus at one location inhibits the activity of adjacent neurons. Lateral inhibition enhances contrast and improves edge detection in sensory systems.

Question 9

Lateral Line System

Answer 9

A mechanoreceptive organ in fishes and amphibians that senses vibrations in the water surrounding the animal. Contains hair cells grouped into structures called neuromasts.

Question 10

Law of Bulk Flow

Answer 10

Physical principle that states that fluids flow down pressure gradients, and that this flow is opposed by the resistance of the system; flow = pressure gradient / resistance.

Question 11

Leak Channel

Answer 11

A passive ion channel in the cell membrane that allows the movement of ions down their concentration gradients.

Question 12

Leaky Epithelia

Answer 12

An epithelial layer with cell-cell connections that permit paracellular transport.

Question 13

Length Constant (λ)

Answer 13

A mathematical constant that expresses the distance that electrotonic current can spread along the membrane of a neuron; the distance over which a change in membrane potential decreases to 37% of its original value.

Question 14

Lengthening Contraction

Answer 14

A type of muscle contraction in which external forces cause the muscle to lengthen while force is being generated.

Question 15

Length-Tension Relationship

Answer 15

Describes the influence of sarcomere length on force development in muscle; muscle generates optimal force when sarcomere length is about 2 μm (in most muscles), and tension declines at higher or lower sarcomere lengths.

Question 16

Lens

Answer 16

A clear object that can refract light. In the eye, the lens bends incoming light rays, helping to form a focused image on the retina.

Question 17

Leukocytes

Answer 17

Vertebrate white blood cells; cells in blood that are involved in the immune system.

Question 18

Leydig Cell

Answer 18

A testosterone-producing cell interspersed in the interstitium of the testes.

Question 19

Lift

Answer 19

An upward force creating changes in pressure associated with movement over surfaces of an aerofoil/hydrofoil.

Question 20

Lift Coefficient

Answer 20

A property of a surface that expresses its ability to generate lift.

Question 21

Ligament

Answer 21

A form of connective tissue that joins two bones.

Question 22

Ligand

Answer 22

A chemical that specifically and reversibly binds to a receptor or enzyme.

Question 23

Ligand-Gated Ion Channel

Answer 23

An ion channel that opens or closes in response to the binding of a specific chemical.

Question 24

Limbic System

Answer 24

A group of structures in the vertebrate brain that is involved in processes
including emotions and memory.

Question 25

Lineweaver-Burk Equation

Answer 25

A plot of the reciprocals of reaction velocity (1/V) and substrate concentration (1/[S]); generates a linear relationship for enzymes with hyperbolic kinetics.

Question 26

Lipase

Answer 26

An enzyme that breaks down lipid; includes triglyceride lipases, lipoprotein lipase, and phospholipase.

Question 27

Lipid

Answer 27

A class of organic molecules that share hydrophobicity; includes fatty acids, phospholipids, triglycerides, and steroids.

Question 28

Lipid Bilayer

Answer 28

The model for a plasma membrane in which the hydrophobic faces of two monolayers of phospholipids are associated.

Question 29

Lipid Raft

Answer 29

A thickened region of the plasma membrane; often accumulates cholesterol, phospholipids with long chain fatty acids, and proteins with long transmembrane domains.

Question 30

Lipogenesis

Answer 30

Conversion of fatty acids and glycerol to acylglycerides including monoacylglycerides, diacylglycerides, triglycerides, and phospholipids.

Question 31

Lipolysis

Answer 31

Breakdown of acylglycerides and phospholipids.

Question 32

Lipophilic

Answer 32

Hydrophobic or nonpolar.

Question 33

Lipoprotein

Answer 33

A complex of lipids and proteins; central to the transport of lipids between tissues.

Question 34

Load

Answer 34

A force that opposes muscle contraction.

Question 35

Locomotor Module

Answer 35

A set of musculoskeletal components that work together to perform a single function, such as flying.

Question 36

Long-Term Potentiation

Answer 36

A long-lasting enhancement of the postsynaptic response as a result of high-frequency stimulation of the presynaptic neuron.

Question 37

Loop of Henle

Answer 37

A region of a mammalian kidney tubule that connects the proximal and distal tubule; central to the production of hyperosmotic urine.

Question 38

Lower Critical Temperature (LCT)

Answer 38

The lowest environmental temperature at which a homeotherm can survive for long periods; the lower limit of its thermoneutral zone.

Question 39

Lumen

Answer 39

The internal cavity of a multicellular unit, such as a kidney tubule or gastrointestinal tract.

Question 40

Lungs

Answer 40

Respiratory surfaces that originate as invaginations of the body surface. Generally used for gas exchange in air.

Question 41

Luteal Phase

Answer 41

The portion of an ovulatory cycle after the follicle has expelled the ovum and before a second follicle matures.

Question 42

Lymph

Answer 42

A fluid consisting of an ultrafiltrate of blood and immune cells that travels through the lymphatic system of vertebrates.

Question 43

Lymph Hearts

Answer 43

The pumping structures of the lymphatic system, present only in some vertebrates (including fish, amphibians, and reptiles).

Question 44

Lymph Nodes

Answer 44

Small bean-shaped organs found in various locations in the lymphatic system of tetrapods; they filter lymphatic fluid and produce lymphocytes.

Question 45

Lymphatic System

Answer 45

In the vertebrates, a network of vessels or sinuses (depending upon the species) that carries lymph back to the primary circulatory system. In many species it also performs an immune function.

Question 46

Lymphocytes

Answer 46

Leukocytes that are involved in adaptive immunity in vertebrates.

Question 47

Lysosomes

Answer 47

Organelles responsible for the breakdown of damaged and unnecessary membranous compartments and membrane proteins.