Organization of the Nervous System, Basic Functions of Synapses, and Neurotransmitters Flashcards
SENSORY PART OF THE NERVOUS
SYSTEM—SENSORY RECEPTORS
somatic portion of the sensory
system, which transmits sensory information from the
receptors of the entire body surface and from some
deep structures. This information enters the central
nervous system through peripheral nerves and is conducted immediately to multiple sensory areas in (1) the
spinal cord at all levels; (2) the reticular substance of
the medulla, pons, and mesencephalon of the brain;
(3) the cerebellum; (4) the thalamus; and (5) areas of
the cerebral cortex.
what is somatic nervous system
he somatic nervous system is a component of the peripheral nervous system associated with the voluntary control of the body movements
motor functions of the nervous system
(1) contraction of appropriate
skeletal muscles throughout the body, (2) contraction of
smooth muscle in the internal organs, and (3) secretion
of active chemical substances by both exocrine and endocrine glands in many parts of the body
muscle and glands functioning as motor functions are called
effectors
that the skeletal muscles can
be controlled from many levels of the central nervous
system which are
(1) the spinal cord; (2) the reticular
substance of the medulla, pons, and mesencephalon;
(3) the basal ganglia; (4) the cerebellum; and (5) the motor
cortex
e integrative function of the nervous system
important sensory information excites
the mind, it is immediately channeled into proper integrative and motor regions of the brain to cause desired
responses. This channeling and processing of information is called the integrative function
most storage occurs in?
Most storage occurs in the cerebral cortex, but
even the basal regions of the brain and the spinal cord can
store small amounts of information
what is fascillation
if one type of nerve impulse travels from a synpase more than one time the synpase becomes more capable of transmitting the same impulse After the sensory
signals have passed through the synapses a large number
of times, the synapses become so facilitated that signals
generated within the brain itself can also cause transmission of impulses through the same sequences of synapses,
even when the sensory input is not excited.
three major levels of the
central nervous system have specific functional characteristics
(1) the spinal cord level, (2) the lower brain or
subcortical level, and (3) the higher brain or cortical level.
Even after the spinal cord has been cut in the high neck region, many highly organized spinal cord functions still occur.
For instance,?
neuronal circuits in the cord can cause
(1) walking movements, (2) reflexes that withdraw portions of the body from painful objects, (3) reflexes that
stiffen the legs to support the body against gravity, and
(4) reflexes that control local blood vessels, gastrointestinal movements, or urinary excretion.
subconscious activities of the body is controlled by
Many, if not most, of what we call subconscious activities of the body are controlled in the lower areas of the
brain—that is, in the medulla, pons, mesencephalon,
hypothalamus, thalamus, cerebellum, and basal ganglia.
cerebral cortex function
store house of memory
works in association with lower parts of the brain
withoutthe cortex the lower parts of the brain does not work as effeciently
synaptic functions of the neuron
(1) may be
blocked in its transmission from one neuron to the next,
(2) may be changed from a single impulse into repetitive
impulses, or (3) may be integrated with impulses from
other neurons to cause highly intricate patterns of
impulses in successive neurons. A
2 types of synapses
chemical and electric
chemical synapse
In these synapses, the first neuron secretes
at its nerve ending synapse a chemical substance called a
neurotransmitter (often called a transmitter substance),
and this transmitter in turn acts on receptor proteins
in the membrane of the next neuron to excite the
neuron, inhibit it, or modify its sensitivity in some other
way
eg of nerotransmitters
acetylcholine, norepinephrine, epinephrine, histamine,
gamma-aminobutyric acid (GABA), glycine, serotonin,
and glutamate.
electrical synapse
ions move through gap junctions from cytoplasm of one cell to another
principle of one-way conduction
. This characteristic is that they
always transmit the signals in one direction—that is, from
the neuron that secretes the neurotransmitter, called the
presynaptic neuron, to the neuron on which the transmitter acts, called the postsynaptic neuron.
role of calcium
when action potential reaches presynaptic molecule depolarization occurs which causes ca ions to be released into the terminal The quantity of neurotransmitter that is then released from the terminal into the synaptic cleft is directly related to the number of calcium ions
that enter.
calcium binds with release protein in the presynaptic membrane and releease neurotransmitter in the cleft
The membrane of the postsynaptic neuron contains
large numbers of receptor proteins, also shown in . The molecules of these receptors have two important components
(1) a binding component that protrudes
outward from the membrane into the synaptic cleft—
here it binds the neurotransmitter coming from the presynaptic terminal—and (2) an intracellular component
that passes all the way through the postsynaptic membrane to the interior of the postsynaptic neuron
receptor activation controls the opening of ion channels in the
postsynaptic cell in one of two ways:
(1) by gating ion
channels directly and allowing passage of specified types
of ions through the membrane, or (2) by activating a
“second messenger” that is not an ion channel but instead
is a molecule that protrudes into the cell cytoplasm and
activates one or more substances inside the postsynaptic
neuron.
Neurotransmitter receptors that directly gate ion
channels are often called those that act through second messenger systems are
called ?
ionotropic receptors,
metabotropic receptors
second messenger main role
memory is a prolomged neuronal effect which can be causes only due to te releasing of second messenger because the gated ion channels close in milliseconds but the second messenger doesn’t ( pg 575)
changes that can occur trough second messenger
- Opening specific ion channels through the postsynaptic cell membrane.
- Activation of cyclic adenosine monophosphate
(cAMP) or cyclic guanosine monophosphate (cGMP)
in the neuronal cell. - Activation of one or more intracellular enzymes
Activation of gene transcription.
