Exam 4 Objectives
Class 30 - Cell Communication
-Be able to explain how cells communicate via direct contact, local signaling, and long-distance signaling
-Direct contact: the method of cell to cell communication requires CHANNELS connecting the cytoplasm of one cell to the cytoplasm of another
-It is rapid
-It involves ions or small molecules going through these connecting channels in order for information to pass from 1 cell to another
-Names for direct contact structures:
-Gap junctions (in animal cells)
-Electrical synapses (specifically in animal neurons)
-Plasmodesmata (in plant cells)
-Cell-cell recognition and docking (ex: between immune cells)
-Local signaling: this involved a chemical signal being released and received
-Understanding local signaling requires that you remember the meanings of intra and extracellular
-Autocrine and Paracrine
-Autocrine signaling: released by cell and received by same cell
-Paracrine signaling: local regulator is released it diffuses through extracellular fluids and binds receptors on other cells
-Long Distance Signaling:
-Exactly like paracrine signaling except between cells that are further apart and the circulatory system (bloodstream) may be used to transport the signal
-Molecules are called hormones or first messengers or ligands
-Can be ligand or protein based
-Move through the extracellular fluid via diffusions (sometimes with assistance of carrier)
Class 31 - Neurons
-There is a CNS and PNS (central and peripheral nervous system)
-Enteric nervous system
-Includes neurons and glia
-Involves integration of sensory information (hypothalamus)
-Regulates other organ systems
-Neuronal membrane potential
-Resting neuron contains potential energy from charge difference from outside and inside of plasma membrane
-Inside neg, outside positive (measured in voltages)
-Membrane potential is the result of a electrochemical gradient
-What causes the difference in charge across the neuron’s plasma membrane?
-Large, negatively charged proteins inside the cell
-Higher Na+ outside than inside/higher K+ inside than outside; maintaiined by sodium/potassium pump
-K+ lead channels - constantly open (so open at rest), allow K+ to diffuse out of the cell -Very few Na+ are open at rest
-OVERALL THE INSIDE OF THE NEURON IS MORE NEGATIVE THAN THE OUTSIDE OF THE NEURON at rest
-The distribution of ions inside and outside a neuron that produces the resting membrane potential
-Equilibrium potential -Reversal potential -Value or voltage that is specific for a particular ion
-The equilibrium potential tells you the membrane potential at which your ion of interest would have no net movement into or out of the cell -Net movement = overall movement in or out of cell -Use Nernst equation -Closer to equilibrium potential, the less driving force for its diffusion -A cell has to balance the equilibrium potential for all the ions it is permeable to - at any given time the membranes potential is going to sit closest to whatever membrane is permeable
-Nernst Equation -Neuron Membrane Permeability can Change
-If you change the membranes permeability, you will change the distribution of charge across the membrane
-Depolarization: the difference in charge between the inside and outside of the neuron is decreasing, the neuron is more +
-Hyperpolarization: the difference in charge between the inside and outside of the neuron is increasing, the neuron is more -
-Upon the arrival of chemical signals an action potential may occur
-An action potential is an electrical impulse in a neuron -They arise from the movement of ions, mostly Na+ and K+, that means each one of the events MUST correspond to changes on some ion channel
-They are rapid and transient -STEPS:
-1. Positive charge comes into the cell
-2. The cell reaches the threshold
-3. There is an even faster/greater entry of positive charges
Class 30 - Cell Communication
-Be able to explain how cells communicate via direct contact, local signaling, and long-distance signaling
-Direct contact: the method of cell to cell communication requires CHANNELS connecting the cytoplasm of one cell to the cytoplasm of another
-It is rapid
-It involves ions or small molecules going through these connecting channels in order for information to pass from 1 cell to another
-Names for direct contact structures:
-Gap junctions (in animal cells)
-Electrical synapses (specifically in animal neurons)
-Plasmodesmata (in plant cells)
-Cell-cell recognition and docking (ex: between immune cells)
-Local signaling: this involved a chemical signal being released and received
-Understanding local signaling requires that you remember the meanings of intra and extracellular
-Autocrine and Paracrine
-Autocrine signaling: released by cell and received by same cell
-Paracrine signaling: local regulator is released it diffuses through extracellular fluids and binds receptors on other cells
-Long Distance Signaling:
-Exactly like paracrine signaling except between cells that are further apart and the circulatory system (bloodstream) may be used to transport the signal
-Molecules are called hormones or first messengers or ligands
-Can be ligand or protein based
-Move through the extracellular fluid via diffusions (sometimes with assistance of carrier)
Class 31 - Neurons
-There is a CNS and PNS (central and peripheral nervous system)
-Enteric nervous system
-Includes neurons and glia
-Involves integration of sensory information (hypothalamus)
-Regulates other organ systems
-Neuronal membrane potential
-Resting neuron contains potential energy from charge difference from outside and inside of plasma membrane
-Inside neg, outside positive (measured in voltages)
-Membrane potential is the result of a electrochemical gradient
-What causes the difference in charge across the neuron’s plasma membrane?
-Large, negatively charged proteins inside the cell
-Higher Na+ outside than inside/higher K+ inside than outside; maintaiined by sodium/potassium pump
-K+ lead channels - constantly open (so open at rest), allow K+ to diffuse out of the cell -Very few Na+ are open at rest
-OVERALL THE INSIDE OF THE NEURON IS MORE NEGATIVE THAN THE OUTSIDE OF THE NEURON at rest
-The distribution of ions inside and outside a neuron that produces the resting membrane potential
-Equilibrium potential -Reversal potential -Value or voltage that is specific for a particular ion
-The equilibrium potential tells you the membrane potential at which your ion of interest would have no net movement into or out of the cell -Net movement = overall movement in or out of cell -Use Nernst equation -Closer to equilibrium potential, the less driving force for its diffusion -A cell has to balance the equilibrium potential for all the ions it is permeable to - at any given time the membranes potential is going to sit closest to whatever membrane is permeable
-Nernst Equation -Neuron Membrane Permeability can Change
-If you change the membranes permeability, you will change the distribution of charge across the membrane
-Depolarization: the difference in charge between the inside and outside of the neuron is decreasing, the neuron is more +
-Hyperpolarization: the difference in charge between the inside and outside of the neuron is increasing, the neuron is more -
-Upon the arrival of chemical signals an action potential may occur
-An action potential is an electrical impulse in a neuron -They arise from the movement of ions, mostly Na+ and K+, that means each one of the events MUST correspond to changes on some ion channel
-They are rapid and transient -STEPS:
-1. Positive charge comes into the cell
-2. The cell reaches the threshold
-3. There is an even faster/greater entry of positive charges
