Intro to Nervous System 1 Flashcards
What comprises the CNS?
Brain and spinal cord
What comprises the PNS?
Nerves and ganglia
What is a ganglion?
A group of neuron cell bodies outside of the PNS.
What does the somatic nervous system do?
It supplies body parts that we are consciously aware of and have conscious control of – skin, fascia, skeletal muscles, and bones in the body wall and limbs = “the outer shell of the body”
What does the autonomic nervous system do?
It has motor only; supplies viscera (internal organs), smooth and cardiac muscle, and glands – roughly speaking, those structures we have no conscious perception or control of - “the inner guts of the body”. Innervates smooth muscle in the wall of blood vessels - important role in controlling blood vessel diameter and peripheral resistance to blood flow.
What are multipolar neurons?
Neurons with more than two processes (generally have many dendrites and one axon); most neurons within the CNS, including motor neurons that innervate (supply) skeletal muscles.
What type of neurons are most of the neurons in the CNS?
multipolar neurons
What are pseudo-polar neurons?
Neurons that carry sensory information (touch, pain, etc.) to the CNS; most are dorsal (posterior) root ganglion (DRG), or sensory, cells. They have a single short process arising from the cell body that branches into two longer processes – the peripheral process and the central process.
Describe motor neurons
project FROM the CNSmultipolar cells in gray matter of spinal cord innervate (supply) an effector (e.g., a muscle or gland)
Describe sensory neurons
project TO the CNSe.g., dorsal root ganglion (pseudounipolar) cellsbring information from the periphery (e.g. – skin) to the CNS
Describe grey matter
• contains cell bodies of neurons;• organized into clusters of cells called nuclei;• resembles the letter “H” in the spinal cord;• organized into two dorsal (posterior) horns and two ventral (anterior) horns. In some regions, there are also two lateral horns
What part of the grey matter deals with sensory processing?
The dorsal horn
What part of the grey matter deals with visceral motor(autonomic) output?
The ventral horn
Describe white matter
• axons wrapped by fatty myelin• surrounds the “H-shaped” gray matter• cell bodies of neurons absent.• white matter contains tracts (similar to nerves in the PNS)
Describe the tracts of white matter
• containing many nerve fibers (axon processes of nerve cells)• interconnecting regions of the spinal cord with the periphery, with each other, and with the brain.• [These tracts are organized in dorsal (ascending, sensory), lateral (descending motor and ascending sensory), and ventral (mainly descending, motor) locations.
Describe afferent nerve fibers
Afferents carry impulses to the CNS. Afferents that relay information from the body wall and limbs are called somatic afferents.
Describe efferent nerve fibers
Efferents carry impulses from the CNS to “effectors” (muscles, glands, etc. - structures that perform an action). Those that relay information to the body wall and limbs are called somatic efferents. Somatic effferents innervate their targets. Efferents that relay information to smooth muscle, glands, and cardiac muscle are called visceral efferents.
What do myotomes form?
Skeletal muscles of the trunk and limbs
What do dermatomes form?
The dermis of the skin in posterior regions of the body.
What do sclerotomes form?
The bones of the axial skeleton: ribs, vertebrae, and sternum.
What are myotomes supplied by?
Somatic efferents AND somatic afferents (afferents inskeletal muscle monitor stretch)
Where do somatic efferents terminate?
Only on skeletal muscles (NOT on smooth muscle,glands, or cardiac muscle;
What are dermatomes and sclerotomes supplied by?
Somatic afferents (sensory nerve fibers).
What does a spinal cord segment give rise to and receive?
Each segment gives rise to the ventral root and receives the dorsal root of a spinal nerve.
What are the 5 regions of the spinal cord?
cervical, thoracic, lumbar, sacral and coccygeal
What is the conus medularis?
The tapered end of the spinal cord, at about the L1/L2 level.
Why is the spinal cord so much shorter than the vertebral column?
Because of differential growth.
How many cervical segments are there?
8
How many thoracic segments are there?
12
How many lumbar segments are there?
5
How many sacral segments are there?
5
How many coccygeal segments are there?
Just one lonely segment. :(
Where does each spinal nerve exit?
Through the intervertebral foramen below its corresponding vertebra. (exception - the C1 nerve exits ABOVE C1)
What is the cauda equina?
The long dorsal and ventral roots at the end of the spinal cord, gathered together in a bushy structure within thevertebral canal that resembles a “horse’s tail.” There is no spinal cord below L1/L2, only the cauda equina.
Clinically, what is a dermatome?
An area of skin supplied by a single spinal nerve. For example, the T-10 dermatome is a strip of skin at the level of the umbilicus (“belly button”) supplied by the T-10 spinal nerve.
Tell me about myotomes
Myotomes consist of all of the muscles (or portions of muscles) innervated by single spinal nerve. Myotomes are complex because most limb muscles are innervatedby more than one spinal nerve. Myotomes are very important in neurological evaluation and can be successively tested in joints to help localize lesions. They are the key to strength testing and to interpreting tendon reflexes.
CN I
Name: Olfactory NerveFx: Olfaction
CN II
Name: Optic NerveFx: Vision
CN III
Name: Oculomotor nerveFx: Eye movement, pupil constriction
CN IV
Name: Trochlear nerveFx: Eye movement
CN V
Name: Trigeminal nerveFx: Facial sensation, muscles of mastication
CN VI
Name: Abducens NerveFx: Eye movement
CN VII
Name: Facial nerveFx: Muscles of facial expression, taste, lacrimation, salivation
CN VII
Name: Vestibulocochlear nerveFx: Hearing, equilibrium sense
CN IX
Name: Glossopharyngeal nerveFx: Pharyngeal muscles, carotid body reflexes, salivation
CN X
Name: Vagus nerveFx: Parasympathetics to most organs, laryngeal muscles (voice), pharyngeal muscles (swallowing), aortic arch reflexes
CN XI
Name: Spinal accessory nerveFx: Head turning (trapezius and sternomastoid muscles)
CN XII
Name: Hypoglossal nerveFx: Tongue movement
