Download Biology Review: Auxins, Photoperiodism, Action Potentials, Sensory Systems, and Muscles - and more Study notes Biology in PDF only on Docsity! BIO REVIEW SESSION - transport of auxin is downward; unidirectional. High concentrations of auxin inhibit shoots, low concentrations stimulate it - plants have phytochromes which exist in Pr, or Pfr. - When sunlight hits pr, it converts it all into pfr; and then at night it is slowly converted back. Plants are able to tell how long a night was because of how much pfr they have. Some plants only flower in short nights, and some in long nights. - Conversion of pr to pfr is very quick, but pfr to pr is long. At night if you flash a light on the plant, it will convert all pr that is being converted back to pfr. (starts cycle over) - Portal vessels are a way for you to direct hormones somewhat - Hypothalamus somewhat controls the pituitary glands through hormones? - ACTION POTENTIALS o Remember that cell has a resting potential; lots of sodium ions outside, and lots of potassium ions inside as well as organic molecules (negative charge)… the inside is negative relative to the outside* this is true for all cells and for your nervous system. o In the nervous system, you can change the potential o Gated vs Voltage gated In voltage gated channels the channels respond to the voltage across the membrane. If the voltage gets to a certain point, the channels will open. They are responsible for creating the action potential. Only excitable cells have voltage gated ion channels. o By poking the membrane, sodium channels will open allowing sodium in the cell and it will depolarize, causing the inside of the cell to become less negative and more positive compared to the cell. If the cell reaches the threshold, it will activate the voltage gated channel and trigger an action potential. o Action potential propagates, in myelinated cells, the propagation is faster since there are less places for them to propagate. (Schwann cells) o Propagation happens all the way down the axon to the axon terminus and then causes voltage gated Calcium ion channels to open and calcium ions flow in; the calcium channels cause neurotransmitters inside to bind to the membrane and release their contents into the synaptic cleft; the contents then bind to the next cell (have receptors); once neurotransmitters bind, you have to stop them meaning you have to destroy the neurotransmitters o EPSP and IPSP: open up sodium channels is EPSP; open potassium channel IPSP o This is where you get the idea of integration because you don’t just have one neuron connected to another neuron, you have one neuron that’s connect to another neuron that’s also connected a bunch of
