Chapter 5 Vocab Flashcards
Primary ossification
Areas in the mid portion of the shafts of long bones where bone cells are formed so that the cartilage model bones of the fetal skeleton begin ossifying, from the center outward, to form bone shafts
Secondary ossification centers, epiphyseal plates, or pressure epiphysis
Areas near the ends of long bones where new bone cells are formed and deposited so that the bones grow in length. Active secondary ossification centers are indicated on X rays by a line (an area not opaque) that is a layer of cartilage cells
Appositional bone growth
involves addition of new layers so that a bone grows in girth
Twitch
a brief period of contraction of muscle fiber (cell) followed by relaxation. Muscles can be classified as slow twitch or fast twitch
Slow Twitch
Muscles that have a slower contraction- relation cycle and greater endurance than fast twitch ;
Suited to endurace activities
Fast twitch
Suited to intense short duration activities
Hormones
Chemical substances secreted into body fluids by a gland. These substances have specific effects on the activities of target cells, tissues, or organs
Neurons
Cells of the nervous system that receive and transmit information
Synapse
A connection between two neurons; it is made by the release of chemicals called neurotransmitters from an axon. These neurotransmitters cross a small gap between neurons, then permeate the cell wall at the dendrite, or cell body, of a receiving neuron to trigger an electrical impulse
Glia
The cells of the nervous system that support and nourish the neurons
Myelin
An insulating sheath around the axons
Cerebral Cortex
The wrinkled surface of the brain containing millions of neurons and regulating many human functions and behaviors
Myelination
The process whereby the axons of the neural cells are insulated when insulating myelin sheaths formed by Schwann (glial) cells wrap themselves around the axon
Nerve tracts
Major neurological pathways There are two major tracts: the extrapyramidal and the pyramidal
Extrapyramidal tract
Involved in delivering the commands for both the random and the postural movements made by the infant in the first days after birth
