Page 205 - Anatomy and Physiology of Farm Animals, 8th Edition

190 / Anatomy and Physiology of Farm Animals

• Identify by name the nerves of the bra- require the rapid transmission of informa-
All functions of the nervous system
chial plexus, indicating which are sen-
VetBooks.ir sory, which are motor, and which are tion from one site within the body to
both.
another. This transmission is possible
• Identify by name the nerves of the lum- because neurons have the property of
bosacral plexus, indicating which are excitability (see Chapter 2). This property
sensory, which are motor, and which are permits neurons to develop waves of mem-
both. brane depolarization called action poten-
• Name the 12 cranial nerves and provide tials which rapidly propagate along long
a description of the functions of each. cellular extensions, the axons, to distant
Indicate on a specimen or a diagram of locations. When an action potential
the brain the location where each reaches the end of an axon, the informa-
arises. tion encoded in the action potential is
• Describe the anatomy and functions of transmitted to another neuron or some
the autonomic nervous system, differen- other type of cell (a notable example being
tiating between sympathetic and para- muscle cells). This transmission is accom-
sympathetic divisions. plished at specialized junctions known as
synapses.
For descriptive purposes the entire
nervous system (Fig. 10‐1) can be divided
he nervous system consists of the
Tbrain, the spinal cord, and the into two parts: the central nervous system
(CNS), which includes the brain and spinal
peripheral nerves, which connect the var-
ious parts of the body to either the brain or cord, and the peripheral nervous system
(PNS), which largely consists of cranial
spinal cord. A variety of cell types are found nerves and spinal nerves going to and from
within the nervous system, but the primary somatic (body) structures. The autonomic
functional cell is the neuron. A major nervous system (ANS) is that portion of the
function of the other cell types (the glia) nervous system that coordinates activity of
appears to be to maintain the cellular visceral structures (smooth muscle, car-
environment to support the activity of the diac muscle, and glands). The ANS has
neurons. elements in both the central and peripheral
The basic functions of the nervous
system can be summarized thus: nervous systems, and it features both sen-
sory and motor components. One further
1. Initiate and/or regulate movement of division of the PNS is the enteric nervous
body parts by initiating and/or regulat- system, a partially autonomous collection
ing the contraction of skeletal, cardiac, of neurons contained within the walls of
and smooth muscles the gastrointestinal tract which controls GI
2. Regulate secretions from glands function locally and the activity of which is
3. Gather information about the external influenced by the ANS.
environment and about the status of In the PNS, sensory (afferent) nerves
the internal environment of the body, gather information about the external and
using senses (sight, hearing, touch, bal- internal environments and relay this infor-
ance, taste) and mechanisms to detect mation to the CNS. The information is
pain, temperature, pressure, and cer- obtained by specialized organs, cells, or
tain chemicals, such as carbon dioxide, axon terminals that react to specific envi-
hydrogen, and oxygen ronmental energies and initiate action
4. Maintain an appropriate state of potentials in associated sensory axons. The
consciousness specialized structures that detect environ-
5. Generate behaviors in response to basic mental stimuli are sensory receptors.
survival drives (e.g., drinking in response Sensory systems are discussed more com-
to thirst) pletely in Chapter 12.