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peripheral nervous system
sensory receptors are responsive to external and internal stimuli; such input is conveyed to integration centers, which is interpreted and associated with a response.
motor output
the conduction of signals from integration centers to effector cells
effector cells
carry out the body’s response to a stimulus (ex: muscles, glands)
central nervous system
responsible for integration; message conveyed through relay neurons to interneurons
nerves
signals of the nervous system are conducted by…
neuron
structural and functional unit of the nervous system; where nerve impulses are conducted
myelin sheath
axon coated with myelin and composed of many layers of phospholipid bilayer, which increases transmission
schwann cells deposit the myelin by growing around the nerve fiber, depositing a double layer of phospholipid bilayer
cell body
where most of a neuron’s organelles are located
dendrite
highly-branched extension that receives signals from other neurons
axon
a much longer extension than the dendrite that transmits signals to other cells at synapses
axon hillock
cone-shaped base of an axon
synaptic terminal
another name for axon endings; contain neurotransmitters which conduct a signal across a synapse
synapse
junction between a presynaptic and a postsynaptic cell, or a neuron and some other cell
presynaptic cell
cell that SENDS signals
postsynaptic cell
cell that RECEIVES signals
membrane potential
all living cells possess some sort of electrical charge difference, with one side being more negatively charged than the other. this difference is known as…
-70 mV
membrane potential of a neuron in its resting state (resting potential)
difference in ion concentation
why potential exists; difference between cytoplasm and extracellular fluid
Na+
sodium; naturally wants to follow concentration gradient and flow into the cell
K+
potassium; naturally wants to diffuse out of the cell
sodium-potassium pump
helps maintain concentration differences; uses active transport to pump 3 Na+ out and 2 K+ in; represents chemical potential energy
gated ion channels
make changes possible in membrane potential by opening and closing in response to stimuli; excitable, show specificity
voltage-gated ion channels
respond to external stimuli, such as a specific voltage, and respond to changes in potential difference.
threshold potential
depolarization is graded with stimulus intensity only up to a particular voltage
action potential
only triggered once the threshold is reached, can only be generated in the axon of a neuron; triggered by graded (specific) depolarization that originates in a dendrite, or in a cell body and spreads to the axon
nerve impulse
action potential of an axon; non-graded (all-or-nothing propagation) event! reaching the threshold initiates it
factors of impulse speed
axon diameter, myelinated neurons insulated with schwann cells; voltage gates concentrate in nodes of ranvier
schwann cell
any of the cells in the peripheral nervous system that produce the myelin sheath around neuronal axons
nodes of ranvier
gaps in-between schwann cells; extracellular fluid is only in contact with the neuron at these points, so the flow of ions may only take place here
saltatory conduction
action potential travels from node to node
electrical synapse
allows action potential to travel cell to cell through gap junctions
chemical synapse
has neurotransmitters that are released into the synaptic cleft
excitatory synapse
opens ion gates that allow Na+ to enter and K+ to leave
inhibitory synapse
opens Na+ and/or K+, causing hyperpolarization
Ach
aka acetylcholine; one of the most common transmitters, degraded by acetylcholinesterase; both inhibitory and excitatory, depending on the type of receptor
neonicotinoids
synthetic compound similar to nicotine, which binds to the Ach receptor in cholingeric (uses choline) synapses in the CNS of insects; acetylcholinesterase doesn’t break it down, so binding is irreversible and nerve transmission is prevented (but also the insect is paralyzed and dies rather than just being poisoned)
