PT PT PT 2 PT 2 The nervous system has been compared with a computer system, with the brain acting...
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Transcript of PT PT PT 2 PT 2 The nervous system has been compared with a computer system, with the brain acting...
The nervous system has been compared with a computer system, with the brain acting as the central processing unit, relaying messages by way of the spinal cord through nerve fibers
◦ Nerves radiate to every structure in the body to provide connection for input and output data Myelinated nerves – have a coat of white fatty
material, interrupted along the length of the nerve at regularly spaced intervals -found mostly in the CNS
Nonmyelinated nerves – have a thin coat of myelin – found in the autonomic nervous system
Normally, impulses pass in only one direction.◦ Sensory neurons conduct impulses from the sense
organs to the spinal cord and brain◦ Motor neurons conduct impulses from the brain and
spinal cord to muscles and glands◦ Interneurons are responsible for delivering a signal
from one neuron to another The point at which an impulse is transmitted
from the axon of one neuron to the dendrite of another is a microscopic space called a synapse.
Myelinated nerves have a faster signal than nonmyelinated
There is no physical contact of neurons in the synapse.◦ The electrical impulses from one neuron to the
next neuron do not directly jump the synapse but instead cause release of a chemical at the synapse.
Neurons are so specialized that they have lost the power to produce new cells.◦ When an axon is severed, that part distal to the
cell body dies. Once a connection is broken within the CNS, it is
broken forever.
The CNS includes the brain and spinal cord◦ Each are protected from injury by the skeletal
system Brain – skull Spinal Cord – vertebrae
The CNS contains both white and grey matter◦ White color is created by myelinated fibers
formed by the bundles of axons and dendrites◦ Gray color is created by the masses of nerve cells
The meninges are three membranes that envelop the CNS, separating the brain and spinal cord from the body cavities.◦ Dura matter
Outermost layer, hardest, toughest, most fibrous◦ Arachnoid
Middle membrane, less dense, web like in appearance
◦ Pia matter Innermost, thin, compact, very vascular
Supplies blood for the CNS tissue
**Inflammation of the meninges is called meningitis
The brain contains about 100 billion neurons.
The brain in the dog and cat is a highly evolved structure but is less well developed than in more specialized mammals, such as primates.◦ The brain of a canine is more immature than the
human brain at birth, but maturation of cerebral function proceeds at a higher rate. A 1 month old puppy has near adult development of
the CNS
The brain is divided into ◦ Forebrain
Motor area Controls gross, fine, and complicated muscle movements Collects, recognizes, and organizes sensations of pain,
temperature, touch, position, and movement
◦ Midbrain Located between the forebrain and hindbrain
Contains auditory, visual, and muscle control centers and is involved in body posture and equilibrium
◦ Hindbrain Reflex centers for controlling respiration and circulation
Damage to this area instantly causes death