Chapter 48: Neurons, Synapses, and Signaling Flashcards
Neurons
- Nerve cells
- Transfer information within the body
- Long and short-distance electrical signals
- Receive, transmit, and regulate flow of information
Brain
Groups of neurons that sort neuronal paths and connections
Ganglia
Simpler clusters of neurons
Cell Body
Where most of a neuron’s organelles are located
Dendrites
Branched extensions of a neuron
Axon
- Each neuron has one
- Extension that transmits signals to other cells
- Much longer than dendrites
Synapse
Junction that receives transmitted information from the branched end of an axon
Neurotransmitters
- Chemical messengers
- Pass information from a transmitting neuron to a receiving cell at synapses
Glial Cells/Glia
- Supporting cells
- Nourish neurons
- Insulate axons of neurons
- Regulate extracellular fluid surrounding neurons
- Replenish certain groups of neurons and transmit information
- There are more of them than neurons
Sensory Neurons
Transmit info about an external stimuli (i.e. light, touch, smell, or internal conditions like blood pressure)
Interneurons
- Most of the neurons in the brain
- Form local circuits connecting neurons in the brain
Motor Neurons
Transmit signals causing muscle cells to contract
Central Nervous System (CNS)
- In many animals
- Organization of neurons that carry out integration
- Brain and spinal cord
Peripheral Nervous System (PNS)
Neurons that carry information in and out of the central nervous system
Nerves
Bundles of axons of neurons
Membrane Potential
Charge difference/voltage because of potential energy from the attraction of opposite charges across the membrane
Resting Potential
- Membrane potential of a neuron that isn’t sending a signal
- Usually -60 to -80 mV (millivolts)
Sodium-Potassium Pump
- Actively transports K+ in the cell and Na+ out
- Maintains K+ and Na+ gradients
Ion Channels
Pores formed by clusters of specialized proteins across the membrane
Equilibrium Potential (Eion)
- Magnitude of membrane voltage at equilibrium for a particular ion
- Can be calculated with Nernst equation
Gated Ion Channels
- Ion channels that open/close in response to stimuli
- Opening/closing alters membrane’s permeability to ions and therefore alters potential
Hyperpolarization
Ions flow across the membrane, increasing magnitude of membrane potential
Depolarization
- Reduction in the magnitude of membrane potential
- Often involves gated sodium channels
Graded Potential
- Shift in membrane potential
- Magnitude that varies with the strength of the stimulus (larger stimulus causes a greater change in membrane potential)
- Decays with time and distance from source
Action Potential
- Massive change in membrane voltage
- Have constant magnitude and can regenerate in adjacent regions of the membrane
- Good for long distance signal transmission
Voltage-Gated Ion Channels
Open/close when membrane potential passes a particular level
Threshold
- Particular value that depolarization increases membrane voltage to
- In mammalian neurons it’s about -55 mV
Refractory Period
Time when the second activation potential cannot be initiated (caused by inactivation of sodium channels)
Myelin Sheath
Electrical Insulation that surrounds vertebrate axons
Oligodendrocytes
- Produce myelin sheaths
- In the central nervous system
Schwann Cells
- Produce myelin sheaths
- In the peripheral nervous system
Nodes of Ranvier
Gaps in the myelin sheath
Saltatory Conduction
- Mechanism for propagating action potentials
- Action appears to leap from node to node
