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lateral line system
The lateral line is a sense organ in aquatic organisms (chiefly fish), used to detect movement and vibration in the surrounding water. Isolated sensory organs called pit organs and grooves that are lined with arrays of sensory organs. Detect water displacement and currents. lost in adult amphibians, entirely absent in amniotes. TERM 2
Origin of receptor cells
DEFINITION 2 In the lateral line system develop from nuerogenic placodes called lateral line placodes TERM 3
Inner
Ear
DEFINITION 3 Sense of hearing Sense of balance develops from nuerogenic placode called otic placode TERM 4
What do the lateral line system and the inner
ear have in common?
DEFINITION 4
- Receptor cells associated with lateral line system, hearing and equilibrium are called hair cells. 2)Hair cells are mechano-electric transducers that convert a mechanical force into an electric signal that is sent to the brain. * The receptor in the lateral line sytem are cluster of sensory cells ( hair cells) called nueromasts TERM 5
Individual Hair Cell
DEFINITION 5 apical end or the hear of the hair cell is covered with cilias (single kinocilium and a series of sterocilia that are of decreasing length away from the kinocilium) Basal end of the hair cell synapses with neurons that take info from and to the central nervous system Hair cells are often arranged in pairs
Stereocilia
Stereocilia are apical modifications of the cell, which are distinct from microvilli and cilia. are actin filaments covered by plasma membrane, they lack microtubules and are not true true cilia. TERM 7
kinocilium
DEFINITION 7 A kinocilium is a special structure on the apex of hair cells located in the sensory epithelium. is a true cilium with a central axoneme that has 9+2 arrangement of microtubules. TERM 8
Occurrence of nueromasts
DEFINITION 8 Some nueromasts are free standing and occur as isolated structures in shallow pits in the skin. these nueromasts are known as pit organs. pits may be arranged in rows. TERM 9
Role of Hair Cells in Detecting Water Currents
DEFINITION 9 When water currents move the cupula, this causes the cilia to bend and can excite or inhibit the hair cell. hair cell is excited (depolarization) if the stereocilia bend along the axis of symertry toward the kinocilium ion channels open--> influx of K+ into apical end of cell -->calcium ions admitted near base of cell --> release of neurotransmitters -->firing rate increases Hair cell is inhibited if displacement of stereocilia is along the axis of symmetry but away from the kinocilium (firing rate decre TERM 10
Role of Hair Cells in Detecting Water Currents
DEFINITION 10 Movement of cilia that is prependicular to the axis of symmetry will have no effect on exciting or inhibiting the hair cell. Morphological polarization of paired hair cells allows for currents in opposite direction.
Eggs
classified by the relative amount of yolk(microlecithal, mesolecithal, macrolecithal) TERM 17
microlecithal
DEFINITION 17 eggs have a small amount of yolk that is evenly distributed throughout the egg amphioxus has microlecithal eggs, drive their nourishment from the yolk; hatching occurs shortly after fertilization because of the limited yolk supply TERM 18
microlecithal
DEFINITION 18 therian mammals also have microlecithal egss, but microlecithal eggs are secondarily derived in therians and are associated with matrotrophic ebroys that drive nourishment from alternate source such as placenta and lactation TERM 19
Mesolecithal
eggs
DEFINITION 19 mecolecithal eggs have a moderate amount of yolk that is unevenly distributed mesolecithal eggs are found in lampreys, primitive bony fish, lungfish, and amphibians additional yolk allows embryos to hatch at a later stage of development than in amphioxus. the pole of the egg with the highest concentration of yolk is the vegetal pole, and the opposite pole is the animal pole. TERM 20
macrolecithal
eggs
DEFINITION 20 macrolecithal eggs are trlolecithal and have a small disc of cytoplasm sitting atop a large amoun of yolk. macrolecithal eggs are found in most fish (sharks ) reptiles birds and monotremes. large amount of yolk allows for more ectended development
cleavage
is a period of cell division during which the zygote is first converted into a solid ball of cells called the morula, and then into hollow ball of cells known as the blastula. The space inside of the blastula is the blastocoel (segmentation cavity). Little or no growth occurs during cleavage cells become smaller and smaller with successive cell divisions individual cells are blastomeres TERM 22
cleavage in microlecithal
DEFINITION 22 The first cleavage divides the cell into two vertically, the second divides the 2 into 4 vertically, the third divides the 4 into 8 horizontally.
