Answer:
A presynaptic neuron knows when and how much of a certain neurotransmitter it has to release into the synapse by the frequency of the action potential.
Explanation:
Two nuerons connect to each other through synapse. When an action potential, or nerve impulse, arrives at the axon terminal, it activates voltage-gated calcium channels in the cell membrane, then the calcium which is present in hi highconcentration outside the neuron than inside, rushes into the cell. The Calcium then allows synaptic vesicles to fuse with the axon terminal membrane, releasing neurotransmitter into the synaptic cleft.
The nuerotransmitter than binds to the receptors at the post-synaptic cleft and causes the opening or closing of the channels, hence, depolarizing or hyperpolarizing the cells.This can produce a change in the membrane potential—voltage across the membrane of the receiving cell.
<span>The two major forces that shape/reshape the earth are internal forces, i.e.volcanoes and earthquakes and external forces, i.e. weather and the ocean, both of which cause erosion. Volcanoes can add landmass but also can destroy land or cause a winter-like state caused by ash in the atmosphere which can block out the sun and possible killing vast amounts of plant and animal life. Earthquakes can change the land by process of subduction where one plate (land surface or ocean bottom) is forced under another. Erosion wears down geologic formations by the actions of wind and water. Over time water can carve valleys or canyons. Ocean water can erode coastlines by the constant beating of waves on the shore. Wind can carry away particles of land and deposit them elsewhere. Wind and weather combined can be a powerful force for reshaping the earth.</span>
Sobre la pregunta:
Cucigrama. Pregunta 1 vertical. Absorbe nutrientes por medio de micro vellosidades que recubren y aumentan la superficie de absorción
Answer:
Intestino delgado
Explanation:
El intestino delgado es el organi mas largo del tubo digestivo, pudiendo medir 7 metros de longitud y 3 cm de diametro. Se caracteriza por estar sumamente plegado sobre si mismo. La primera porcion, llamada duodeno, recibe secresiones de glándulas biliar y pancreática, y las mezcla con enzimas digestivas. Esta mezcla se encarga de degradar la comida y transformarla en sustancias solubles, como amino ácidos.
Es en el intestino delgado donde ocurre la absorción de nutrientes. Las paredes intestinales estas cubiertas por microvellosidades que aumentan la superficie de absorción.
Las microvellosidades son células que componene el epitelio columnar, y que extienden proyecciones hacia el lumen del organo.
