Cells that send and receive electrical (long distance) or chemical signals(short distance) (aka transfer info in body) Form matches function
Central Nervous System (CNS)
Vertebrates= brain and spinal cord integrates sensory input
Peripheral Nervous System (PNS)
Vertebrates= nerve cells outside the CNS motor output response
Contains cell machinery
Integrates/generates signals , the "decider"
Sends signals to terminal branches
Synaptic (aka Axon) Terminals
Send signals to other cells (neurons, muscles, glands etc...)
Chemical messengers that pass info. from transmitting neuron (presynaptic cell) to receiving cell (postsynaptic cell)
Junction/space between 2 cells
Supporting cells that help neurons of vertebrates and many invertebrates function normally. Outnumber neurons by a LOT. A single glial cell wraps itself around an axon to form a segment of the myelin sheath
Astrocytes (type of glia)
-Metabolic support to neurons. Form blood-brain barrier see p 1067 for more info
Myelin Sheath (type of glia)
-Signaling speed Myelin integrity genetically determined in many brain areas important for intelligence and better integrity= more intelligence
go back to slide 12
All cells have this, a voltage (diff. in electrical charge) across their plasma membrane. The inside of cell is negative relative to outside. In neurons, inputs cause changes in this potential that acts as signals, transmitting and processing info.
The membrane potential of a neuron that is NOT transmitting signals. Na+ and K+ gates closed initially. Depends on the differences concentration gradients of K+ and Na+ ions across plasma membrane, more K+ inside cell, more Na+ outside in mammals. Concentration maintained by Na-K pumps pump transports Na out of cell and K into it. ion channels w/ selective permeability exist and many are of K+ type, so K+ allowed to flowout easily in this state leading to - charge in cell.
Electrical: opposites attract Chemical: move away from other ions
An increase in the magnitude of the membrane potential (inside More -) due to opening of K+ channels allowing K+ to flow out Any stimulus that increases outflow of + ions or inflow of - ions
A reduction in the magnitude of the membrane potential (inside more +) Often involves gated Na channels opening and Na+ inflowing creating more + charge inside
Voltage-gated Ion Channels
gates that open/close in response to a change in the membrane potential and can lead to an action potential
Nerve impulses/signals that carry info. along an axon caused by a rapid opening of many Na+ gates leading to a strong depolarizing stimulus which results in an A.P. due to it passing the THRESHOLD value of membrane potential... a brief all-or-none depolarization of a neuron's plasma membrane
Hyperpolarization and depolarization are both this b/c magnitude of the change in the membrane potential VARIES w/ the strength of the stimulus.
K+ channels open up and K+ rushes out of the cell at the same time the Na+ gates are closed as we return to resting potential (and actually pass it) aka more negative inside cell
K+ gates opened too long and go past resting potential so now K+ allowed to exit during this period as we build back up to resting potential, and once reached, K+ gates close . Also, a 2nd AP cannot be initiated here, this interval sets a max. frequency at which APs can be generated and ensure that APs travel in ONE direction from cell body to axon terminals due to inactivation of Na+ channels as well
The ones that target ion channels have evolved as self-defense or predatory capturing mechanisms. Scientists use these toxins to study ion channels.
for defense Blocks Na+ channels= paralysis
Alpha- and Beta- Toxins
predatory Shift opening and closing of Na+ channels = scrambled signals
for defense Blocks K+ channels= prolonged action potentials
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