Peripheral Nervous System Quiz

Spinal Nerves and ANS Overview

• Spinal nerves connect the spinal cord to the vertebral column, exiting through the vertebral canal.
• A typical spinal nerve has distinct parts: dorsal and ventral rami.
• Dermatomal and cutaneous innervation patterns differ, the former relates to segmental innervation and the latter to peripheral skin innervation.
• A myotome is a group of muscles innervated by a specific spinal nerve; testing myotomes is a clinical technique.

Overview & Objectives

• The relationship between the spinal cord and the vertebral column and how spinal nerves exit the vertebral canal are described.
• Parts of a typical spinal nerve, including the distribution of the dorsal and ventral rami, are identified.
• Comparison and contrast of segmental and peripheral cutaneous innervation, and what a myotome is, are explained.
• The organization of the somatic nervous system is described, including neuron locations, pathway neuron counts, and information types.
• Differentiation between the sympathetic and parasympathetic nervous systems of the autonomic nervous system (ANS) is described, including their organization and the information they carry.

Nervous System

• The nervous system functions as a highway to facilitate communication with the external environment.
• The ability to react and respond to external stimuli is a key function of the system.

Neurons

• Neurons are the fundamental structural and functional units of the nervous system, responsible for rapid communication.
• Dendrites receive and process incoming information, relayed to the cell body (soma) for interpretation.
• Axons transmit the signal away from the cell body towards the synapse, via myelination.
• Synapses mediate signal transmissions between neurons through chemical messages (neurotransmitters).
• Motor neurons have numerous dendrites; sensory neurons have a distinct structure.
• Electrical signals, called action potentials, travel within a neuron in one direction, away from the cell body and towards the synapse.

Spinal Cord

• The spinal cord, part of the CNS, is organised into 31 segments.
• Sensory and motor neurons carry information to and from the spinal cord.
• Spinal nerves derive from the spinal cord and are named based on the vertebrae between which they exit.
• The spinal cord processes both sensory and motor information.

Spinal Nerves

• 31 pairs of spinal nerves exit the vertebral column via intervertebral foramina.
• Cervical nerves (C1-C8) exhibit a distinct pattern of exiting superior to their corresponding vertebra.
• Thoracic, lumbar, sacral, and coccygeal nerves exit below their respective vertebrae.
• Spinal nerves are formed from the ventral and dorsal roots.
• Each dorsal ramus innervates muscles intrinsic and skin of the back
• Ventral rami may form plexuses or remain separate, contributing to peripheral nerve formation.
• Dermatomes are specific areas of skin supplied by sensory branches from a particular spinal nerve.
• Cutaneous innervation is an area of skin innervated by a peripheral nerve; this is frequently used when assessing sensory function in patients..

Case: IVD Hernitation

• A 30-year-old patient presented with low back pain and radiating pain in the right lower extremity, alongside associated numbness.
• Imaging revealed a large right-sided L5/S1 extruded disc herniation.
• The herniation may explain the patient's symptoms.

Spinal Nerves: Radiculopathy

• Radiculopathy is a condition involving nerve root compression.
• Symptoms associated with radiculopathy depend on the affected nerve root.
• Sensory symptoms can include paresthesia, numbness, or anesthesia.
• Motor symptoms may involve weakness, and potentially atrophy.

Spinal Nerves Myotome

• Myotomes are groups of muscles innervated by a particular spinal nerve.
• Specific myotomes, like those of S1 for plantar flexion or C6 for elbow flexion, can be clinically tested. Videos demonstrate clinical testing procedures

Overview: Nervous System

• The somatic nervous system conveys information between the CNS and skeletal muscles.
• The visceral nervous system interacts with internal organs, which includes glands and blood vessels.
• Information transmission between the CNS and body parts are described generally.

Somatic Nervous System

• The somatic nervous system consists of one sensory and one motor neuron, directly affecting the muscles and skin.

Visceral Nervous System

• The visceral nervous system uses two motor neurons to relay information to organs, glands and blood vessels. The pathways of this system are more complex, differing from the somatic system's direct connection.

Autonomic Nervous System

• The autonomic nervous system, part of the visceral system, involves two neuron pathways.
• Two divisions exist: the sympathetic and parasympathetic systems.

Autonomic Nervous System Ganglia

• Three types of autonomic ganglia exist: intramural, prevertebral, and paravertebral
• Intramural ganglia are embedded in the target organ.
• Sympathetic and Parasympathetic nerves have different cell body locations in the cord.
• Sympathetic neurons have short preganglionic, and long postganglionic neurons.
• Parasympathetic neurons have opposite arrangements to sympathetic neurons in locations.

Sympathetic Nervous System Pathway

• The sympathetic pathway, originating from T1-T12, follows distinct routes to regulate responses.
• Three different, basic options exist during this function.