Anterior grey column s in the anterior grey column of the
spinal cord The
anterior grey column, (also known as the anterior horn of spinal cord and anterior cornu) is broad and of a rounded or quadrangular shape. Its posterior part is termed the base, and its anterior part the head, but these are not differentiated from each other by any well-defined constriction. It is separated from the surface of the spinal cord by a layer of white substance which is traversed by the bundles of the anterior nerve roots. In the thoracic region, the posterolateral part of the anterior column projects laterally as a triangular field, which is named the
lateral grey column. It comprises three different types of neurons, two types of
lower motor neuron – large
alpha motor neurons, and medium
gamma motor neurons, and small neurons thought to be
interneurons. They are organized in the same manner as the muscles they innervate.
Gamma motor neurons Gamma motor neurons innervate
intrafusal muscle fibers that control the sensitivity of
muscle spindles to stretch. They have smaller cell bodies than alpha motor neurons and do not receive proprioceptive input.
Posterior grey column The
posterior grey column, also known as the posterior (or dorsal) horn of spinal cord, is subdivided into six layers known as
Rexed laminae, based on the type of sensory information sent to each section. •
Marginal nucleus of spinal cord (lamina I) •
Substantia gelatinosa of Rolando (lamina II) •
Nucleus proprius (laminae III, IV) •
Spinal lamina V, the neck of the posterior horn •
Spinal lamina VI, the base of the posterior horn. The other four laminae are located in the other two grey columns in the spinal cord. The function of the spinal dorsal horn is to process and integrate sensory information from the
peripheral nervous system. It receives inputs from
primary afferent fibers and modulatory systems, and it projects to higher brain centers and
motor neurons. The dorsal horn circuitry is involved in various aspects of sensory processing, including discrimination, integration, and modulation of
nociceptive and non-nociceptive signals. Dysfunction of the dorsal horn circuitry has been implicated in chronic pain conditions and other neurological disorders. Laminae I and II receive information from
afferent neurons that sense nociception, temperature, and itching, laminae III and IV are sent information from neurons that sense mechanical pressure, and laminae V and VI are sent information from proprioceptors. It is known to be the primary relay point for
haptic and
nociceptive messages. The function of the spinal dorsal horn is to process and integrate sensory information from the
peripheral nervous system. It receives inputs from
primary afferent fibers and modulatory systems, and it projects to higher brain centers and
motor neurons. The dorsal horn circuitry is involved in various aspects of sensory processing, including discrimination, integration, and modulation of
nociceptive and non-nociceptive signals. Dysfunction of the dorsal horn circuitry has been implicated in chronic pain conditions and other neurological disorders.
Lamina I Lamina I is also known as the
marginal nucleus of spinal cord. The majority of posterior column projection neurons are located in lamina I, however most neurons in this layer are interneurons. The main areas these neurons innervate are the
caudal ventrolateral medulla (CVLM), the
nucleus of the solitary tract (NTS), the
lateral parabrachial area (LPb), the
periaqueductal grey matter (PAG), and certain regions in the
thalamus. The CVLM receives nociceptive and
cardiovascular responses. The NTS receives cardio-respiratory inputs and affects
reflex tachycardia from noxious stimulation. The LPb projects to the
amygdala and
hypothalamus and is involved in the emotional response to pain. The PAG develops ways to deal with pain and is a main target of
analgesics. It projects to other parts of the brainstem. The nuclei of the thalamus affect sensory and motivational aspects of pain. The neurons of this lamina can be distinguished by their morphology as
pyramidal,
spindle, or
multipolar.
Lamina II This layer is also known as the
substantia gelatinosa of Rolando and has the highest density of neurons. These neurons mediate the activity of nociceptive and temperature afferent fibers.
Laminae III and IV These laminae are also known as the
nucleus proprius and contain a much smaller density of neurons than lamina II.
Lamina V This lamina is also known as the neck of the posterior column and receives information from mechanoreceptors and danger information from nociceptors.
Lateral grey column The
lateral grey column, or the lateral horn of spinal cord, is part of the
sympathetic nervous system and receives input from
brain stem, organs, and
hypothalamus. The lateral column is only present in the thoracic region and upper lumbar segments. The lateral grey column contains preganglionic cell bodies of the autonomic nervous system and sensory relay neurons. ==Clinical significance==