The Three Trunks Of The Plexus

p.483 The cell bodies of primary-order neurons or pain-transmitting neurons reside in the dorsal root ganglia just lateral to the spine along the sensory pathways that penetrate the posterior part of the cord. The second order neurons are found in the dorsal horn (p.484) Most nociceptive information tranvels by means of ascending columns in the lateral spinothalamic tract (also called the anterolateral funiculus). The principal target for nociceptive afferents is the thalamus (the major relay station of sensory information in general) Third order neurons project to portions of the CNS involved in the processing and interpretation of pain, the chief areas being the reticular and limbic systems and cerebral cortex. (p 484)

6. Define the term stretch reflex and describe how stretch reflexes are used to anatomically localize SCI.

Movement of the deltoid begins in the cerebrum of the brain, but more specifically: in the frontal lobe, the premotor cortex is relaying instructions to the primary motor cortex. The primary motor cortex contains the upper motor neurons whose axons will travel down the pyramids of the medulla oblongata and synapse on lower motor neurons in the anterior gray horns of spinal cord segments C5-C6. From there, the ventral rami of spinal nerves C5-C6 form the superior trunk of the brachial plexus, which splits into two divisions. We will follow the posterior division that supplies to extensor muscles. This posterior division then runs into the posterior cord from which the axillary nerve is derived. The axillary nerve’s motor end innervates the deltoid through its neuromuscular junction.

The cervical spinal nerve C3-5 innervate the phrenic nerve. These are the lower motor neurons.

a) The structures and the afferent division of the peripheral nervous system that are involved in

Motor Tracts- Lateral and Anterior corticospinal tracts all decussate (cross over) between the cerebral cortex and the spinal cord.

A. Starting at the epiblast, describe five developmental events leading up to the generation of upper motor neurons that reside in layer 5 of the motor cortex.

Lightly myelinated Aδ fibers and unmyelinated C fibers have thinner axons and a higher threshold of activation. Nociceptors of Aδ fibers can be either mechanosensitive or thermosensitive. Polymodal nociceptors (of C fibers), may respond to both mechanical and thermal stimuli, as well as chemicals [261-263]. When nociceptors are activated, the fibers transmit action potentials along the axon to the spinal cord [264, 265]. The spinal cord mediates sensory and motor communication between the periphery and the brain, and is organized into four regions; cervical, thoracic, lumbar, and sacral. The gray matter contains cell bodies of neurons and glia and is divided into the dorsal horn, intermediate column, lateral horn, and ventral horn. The dorsal horn is comprised of sensory nuclei that receive and process incoming sensory information [266], and like the rest of the spinal gray matter, is organized histologically into parallel laminae based on the size and density of neurons [267]. In general, laminae I to IV are involved in exteroceptive sensation whereas laminae V and VI are involved in proprioceptive sensations [263]. Nociceptors terminate in the dorsal horn laminae in a

The spinal cord consists of a superficial White matter and a deep Gray matter. The white matter consists of myelinated axons, which form nerve tracts and the Gray matter consists of neuron cell bodies, dendrites and axons. The white matter in each half of the spinal cord is organized into ventral, dorsal and lateral columns. Each column is subdivided into tracts also called pathways. A collection of axon inside the CNS is called a tract but outside the CNS it is called a nerve.

The preganglionic fibres are myelinated and project out of the cord via the ventral root. From there

The brachial Plexus is the network of nerves that sends signals from the spine to the shoulder, arm, and hand. The nerve fibers within this network run from the spine where it passes through the cervico-axillary canal where it finally reaches the axilla. It is formed in the cervical and thoracic parts in the spine, (C5-C8, T1). An injury occurs to this when the nerves are aggravated. This could mean they become stressed, compressed, or ripped away from the spinal cord. Some common injuries that cause this is in contact sports such as football, basketball, hockey, or lacrosse. More serious injuries are from car accidents or motorcycle incidents that can leave someone paralyzed and with a loss of all sensations or functions the arm, hand, or

is a split or divide in the spinal column, and the spinal cord and nerve roots exit through

Knowing the anatomy of the muscle system can help many people when understanding different parts of the field they study. Aspiring to be a cosmetologist, it is important for me to understand the muscle system in the way that certain muscles can stimulate certain reactions of the human body. Services such as facials and scalp massages involve the movement of the face, neck, back, head, arms, and hands. By knowing the way the muscular system is organized to better accommodate a client, a better and more successful cosmetologist can be formed. Also, by being aware of the best way to move and take care of my own muscles, I can avoid long term pain, fatigue, and other problems common to cosmetologists.

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brain, the centre of the spinal cord and in the ganglia. Nerve fibres are grouped together to form the