Transcript Nervous System I

Nervous System I
Chapter 11
Nervous System
 The nervous system is the master controlling
and communicating system of the body
 Every thought, action, and emotion reflects its
activity.
 Three overlapping functions
 Millions of sensory receptors to monitor changes
occurring both inside and outside the body. (called
sensory input)
 It processes and interprets sensory input and decides
what should be done at each moment
 It causes a response (called motor output), by
activating effector organs
 This next slide is on pg 389 in your book!
Nervous System
Central Nervous System and
Peripheral Nervous System.
 Central Nervous System (CNS) composed
of the brain and spinal cord
 Peripheral nervous system (PNS)
composed of the nervous (cranial and
spinal) that connects the CNS to other
body parts.
 Together these systems provide three
general functions sensory, integrative and
motor.
Autonomic and Somatic Nervous
Systems
 Autonomic:
 Somatic:
Portion of the
nervous system
that controls the
actions of the
viscera. (such as heart,
stomach, intestines, and
various glands)
Portion of the
nervous system
that controls skin
and skeletal
muscles.
Two Divisions of Autonomic
Nervous Systems
 Sympathetic
Division:
Mobilizes body
systems. Arises
from the thoracic
and lumbar regions
of the spinal cord.
 Parasympathetic
Division:
Conserves energy
and promotes
housekeeping
functions during
rest. Arises from
the brain and
sacral regions of
the spinal cord.
Nervous System
 The nervous system is composed
predominantly of neural tissue.
 It also includes some blood vessels and
connective tissue.
 Neural Tissue consists of two cell types
 Nerve cells called Neurons
 Neurogilia or glial cells
Neurons and Neuroglial Cells
 Neurons-
A nerve
cell that consists of a
cell body and its
processes.
 Neuroglialspecialized cell that
produces myelin,
communicates
between cells, and
maintains the ionic
environment, as well
as other functions.
Neurons
 They are specialized to react to physical and
chemical changes in their surroundings.
 While variable in size and shape, all neurons
have three parts. Dendrites receive information
from another cell and transmit the message to
the cell body. The cell body contains the
nucleus, mitochondria and other organelles
typical of eukaryotic cells. The axon conducts
messages away from the cell body.
 The information is in the form of of bioelectric
signals called nerve impulses.
 Nerves are bundles of axons.
Neurons
Draw, Color and Label
 You need to use a plain white sheet of
paper and properly draw, color, and label
a neuron.
 You may use the drawing in this
PowerPoint or on pg 392 in your book.
Classification of Neurons
 Neurons vary in size and shape, and in function.
 Structure is different.
 Bipolar- a cell body with two processes, one axon
and one dentrite. (Specialized parts of eyes, nose and
ears.)
 Unipolor- Cell body with a single process that divides
into two branches and functions as an axon.(cell body
in ganglion outside the brain or spinal cord)
 Multipolar- Cell body with many processes, one of
which is an axon, the rest dendrites.( Most common
type of neuron in the brain and spinal cord)
Classification of Neurons
 When function is different…
 Sensory neuron conducts nerve impulses from
receptors in peripheral body parts into the brain
or spinal cord
 Interneuron-Transmits nerve impulses between
neurons within the brain and spinal cord
 Motor Neurons- conduct nerve impulses from
the brain or spinal cord out to effectors- muscle
or glands.
The Synapse
 The operation of the nervous system depends
on the flow of information through chains of
neurons functionally connected by synapses.
 The synapse is a junction between two cells.
 A synaptic cleft is the gap between parts of the
two cells at a synapse.
 Synapse can occur between two neurons, a
receptor cell and a neuron, or a neuron and an
effector.
The Synapse
Transmission
 Between adjacent neurons, there is a
microscopic gap called the synaptic
cleft.
 However small, the electrical signal
carrying a message cannot bridge
the synaptic cleft as it is.
The Synapse
 The neuron conducting impulses toward the
synapse is the presynaptic neuron
 The neuron transmitting the electrical signal
away from the synapse is the postsynaptic
neuron.
 There are two varieties of synapses:
 Electrical
 Chemical
The Electrical
Synapse
 Less common variety.
 They intimately connect the cytoplasm of
adjacent neurons and allow ions and small
molecules to flow directly from one neuron to the
next.
 Found in regions of the brain responsible for
certain stereotyped movements.
 Jerking of the eyes
 Involved in emotions and memory.
 Abundant in embryonic nervous tissue.
The Chemical Synapse
 The chemical synapse are specialized for release and
reception of chemical neurotransmitters.
 The solution to this is the synapse, an elegant way of
bridging the gap chemically. The electrical impulse
triggers the release of certain chemical substances
into the gap. These substances are called
neurotransmitters and are carried over the small
synaptic cleft by diffusion.
The Synapse
Transmission
 Once on the other side of the cleft,
the neurotransmitters bind to certain
proteins, called receptors, that are
attached to the cell surface of the
receiving cell. The binding of the
transmitter to the receptor leads to
the generation of a new electrical
impulse. The gap has been bridged!
 The SynapseNerve Signaling – An
Introduction
The Synapse
Synapse Transmission
Transmission
 Impulses usual travel from dendrite or cell body, then
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along the axon to a synapse.
Axons have synaptic knobs at their distal ends that
secrete neurotransmitters.
The neurotransmitter is released when a nerve impulse
reaches the end of an axon, this opens two channels
Na+ and Ca2+
This surge of Ca2+ acts as a messenger, directing
synaptic vesicles to empty contents.
Then the neurotransmitter diffuses across the synaptic
cleft
A neurotransmitter reaching the dendrite or cell body on
the distal side of the cleft triggers a nerve impulse.
Neurotransmitters
Neurotransmitter
 Different neurotransmitters are being
released on different occasions. The
intensity and strength of the
electrical impulse will decide which
neurotransmitter to be released.
Neurotransmitters
Neurotransmitter
 Not all neurotransmitters are known, but
among the more profoundly mapped
 Some medical disorders are caused by the
dysfunction of neurotransmission in the
central nervous system, for example lack
of certain neurotransmitters.
 One such disorder is Parkinson's disease.