Nervous System Flashcards
Nervous System
senses and responds to changes in the environment
Three classes of neurons:
afferent neurons, interneurons, efferent neurons
afferent neurons
Sensory neurons. detect stimulus and relay info about it to central nervous system
Stimulus-
form of energy that specific receptors detect
interneurons
In the spinal cord and brain, interneurons receive and process the sensory information and integrate a response
efferent neurons
Motor neurons (efferent neurons) delivers information away from the brain and spinal cord to the body’s effectors, which carry out the specified response
effectors
muscles, glands
Dendrites-
slender extensions of cell body that are input zones for info
Cell body neuron
contains nucleus, cytoplasm, most of the organelles
Axon-
slender and long extension that is neuron’s conducting zone (where it sends the message)
Terminal branches-
ending axon branches
Synaptic terminals-
ends of terminal branches which release neurotransmitters-
neurotransmitters
chemicals that transmit signal from one neuron to another
Synapse-
junction between a synaptic terminal of one neuron and the dendrites of another (between two neurons or between a neuron and an affector)
Myelin sheath-
insulating covering on axons of vertebrate nerve cells made of special cells called Schwann cells
Nodes of Ranvier + signals
gaps in sheath between successive Schwann cells. signals are electrical (ions) and to bridge
the gaps between synapses there are chemical signals
Nerve-
hundreds or thousands of neurons wrapped together
Resting neuron
polarized
polarized
cytoplasmic fluid is negatively charged
Resting membrane potential-
-70 millivolts
electrical response to stimulation in neurons
action potential–In neurons, this electric gradient will briefly reverse itself in response to stimulation–goes from - to +, travels from a neuron’s trigger zone (dendrites) to output zone (axon)
neurons at rest
hen a neuron is at rest, there are about 15 sodium ions in the fluid inside the cell for every 150 outside. There are 150 potassium ions inside for every 5 outside. The ions can only enter and leave the cell through transport proteins
Passive ion channels
permit the passage of specific ions; Potassium channels are the most common- potassium ions leak out of the cell, down their conc gradient. This increases the positive charge in the extra cellular fluid outside the cell.
Gated ion channels
closed when the neuron is at rest and only open at certain voltages