Nervous System Flashcards
Information processing steps
- Sensory input
- Integration
- Motor output
Sensory neurons
Function in transmitting information from external stimuli
Afferent: bringing in info
Interneurons
Function in integration of sensory information
Motor neurons
Function in triggering muscle or gland activity
Efferent: sending out info
Central nervous system
Portion of nervous system where signal processing and integration takes place
Includes brain and nerve cord
Peripheral nervous system
Portion of nervous system that carries information in and out of the CNS
Nerves
Neurons of PNS bundled together
Information transfer
Afferent (signals into CNS) and efferent (signals out of CNS)
Cell body (soma)
Location of most of neuron’s organelles
Dendrites
Highly branched extensions that receive signals from other neurons
Axon
Long extension that transmits signals to other cells at synapses
Axon hillock
Cone-shaped base of axon (place where axon is attached to cell body)
Synaptic terminal
End of axon
Passes information across the synapse
Neurotransmitters
Chemical messengers
Information that is transmitted across synapse
Synapse
Junction between an axon and another cell
Flow of information transfer
Info is transmitted from presynaptic cell (neuron) to postsynaptic cell (neuron, muscle, or gland cell)
Glial cells
Nourish or insulate neurons
Membrane potential
Cell’s voltage difference across its membrane
Changes in this act as signals
Resting potential definition
Membrane potential of a neuron not sending signals
Resting potential of a mammalian neuron
K+ is highest inside cell
Na+ is highest outside cell
Many open K+ channels, but fewer open Na+ channels: K+ diffuses outside of cell (resulting buildup of negative charge is major source of membrane potential)
Sodium-potassium pumps
Use energy of ATP to maintain K+ and Na+ gradients across plasma membrane (chemical potential energy)
Opening of ion channels in plasma membrane
Conversion of chemical potential to electrical potential
Gated ion channels
Open or close in response to stimuli, causing changes in membrane potential
Hyperpolarization
Increase in magnitude of membrane potential (increase in negative charge)
Caused by opening of gated K+ channels: K+ diffuses out of cell, making inside of cell more negative
Depolarization
Reduction in magnitude of membrane potential
Opening other types of ion channels (ex: Na+) counteracts hyperpolarization
Graded potential
Changes in polarization where the magnitude of the change varies with the strength of the stimulus
Action potential
Massive change in membrane voltage caused by a large shift in membrane potential by depolarization
Constant magnitude, all-or-none, transmit signals over long distances
Voltage-gated ion channels
Open or close when the membrane potential passes a certain level
Action potential steps
- Resting potential (voltage-gated Na+ and K+ channels are closed)
- Voltage-gated Na+ channels open: Na+ flows into cell
- Rising phase: threshold is crossed and membrane potential increases
- Falling phase: voltage-gated Na+ channels become deactivated and voltage-gated K+ channels open, causing K+ to flow out of cell
- Undershoot: membrane permeability to K+ is higher than normal, and then voltage-gated K+ channels close and resting potential is restored
- Refractory period: second action potential cannot be initiated (temporary inactivation of Na+ channels)
