Nervous System Flashcards
The nervous system
obtains sensory information, sensory input,
processes sensory information, integration, and
sends commands to effector cells (muscles) that carry out appropriate responses, motor output.
The central nervous system (CNS)
consists of the
brain and spinal cord (vertebrates).
The peripheral nervous system (PNS)
is located outside the CNS and
consists of
cranial and spinal nerves (axons wrapped in connective tissue)
ganglia (clusters of neuron cell bodies).
Sensory neurons
convey signals from sensory receptors to the CNS.
Interneurons
are located entirely in the CNS,
integrate information, and send it to motor neurons.
Motor neurons
convey signals to effector cells.
Neurons are
cells specialized for carrying signals and
the functional units of the nervous system.
A neuron consists of
a cell body and
two types of extensions or processes that conduct signals,
dendrites and
axons.
Myelin sheaths
form a cellular insulation, and
speed up signal transmission.
myelin is a lipoprotein
myelin accounts for “white matter
Gray Matter
Comprised mostly of neuron cell bodies
Possibly some blood vessels. - A fair amount of
neuroglial cells, cells that support and nourish neurons
membrane potential
At rest, a neuron’s plasma membrane has potential energy—the membrane potential, in which
just inside the cell is slightly negative and
just outside the cell is slightly positive.
The resting membrane potential
The resting membrane potential is the voltage across the plasma membrane of a resting neuron.
The resting potential exists because of
differences in ion concentration of the fluids inside and outside the neuron. Inside the neuron K+ is high and Na+ is low. Outside the neuron K+ is low and Na+ is high.
Resting Membrane Potential is established by….
Na+/K+-ATPase pump
3 Na + ions out for every 2 potassium ions in
Leakiness of membrane to K+
many more K+ leak channels compared to Na+
Intracellular Proteins tend to be negatively charged
“fixed anions”
At Rest = polarized = -70mV
A stimulus
is any factor that causes a nerve signal to be generated. A stimulus
alters the permeability of a portion of the membrane,
allows ions to pass through, and
changes the membrane’s voltage.
Thus, depolarizing the membrane
action potential
A nerve signal, called an action potential, is
a change in the membrane voltage, from the resting potential, to a maximum level, and back to the resting potential.
Action potentials are
self-propagated in a one-way chain reaction along a neuron and are
all-or-none events.
The frequency of action potentials (but not their strength) changes with the strength of the stimulus.
Synapses
are junctions where signals are transmitted between
two neurons or
between neurons and effector cells.
Electrical signals pass between cells at electrical synapses. Found between:
- smooth muscle and cardiac muscle cells
At chemical synapses
the ending (presynaptic) cell secretes a chemical signal, a neurotransmitter,
the neurotransmitter crosses the synaptic cleft, and
the neurotransmitter binds to a specific receptor on the surface of the receiving (postsynaptic) cell.
