PHTY 140 Peripheral Nerves PDF

PHTY 140 Nervous Tissue 2 Peripheral Nerves Emily Grant Contents E Lecture 1 – Structure of Nervous Tissue & Nerve Conduction Structure and Function of Neurones Structure and Function of Glial cells Nerve Conduction Synaptic Transmission Spatial and temporal summation E Lectu...

PHTY 140 Nervous Tissue 2 Peripheral Nerves Emily Grant Contents E Lecture 1 – Structure of Nervous Tissue & Nerve Conduction Structure and Function of Neurones Structure and Function of Glial cells Nerve Conduction Synaptic Transmission Spatial and temporal summation E Lecture 2 – Peripheral Nerves ▪ Afferent & efferent signalling ▪ ‘Mixed’ Spinal Nerves ▪ Nerve plexus ▪ Dermatomes & myotomes Emily Grant – Division of Physiotherapy  Autonomic sensory neurones Somatic sensory neurons transmit information from internal transmit information from sense organs and feed-back to the CNS organs and feed-back to the CNS Sympathetic Division Prepares the body for emergencies Autonomic Somatic Central Nervous System Nervous System Regulating the Nervous System Enables us to interact internal with the external Brain & Spinal Cord environment environment (Integration and command centre) Parasympathetic Division Regulates the body during non-emergencies Autonomic motor neurones Somatic motor neurones transmit signals from the CNS to transmit signals from the CNS to innervate internal organs and glands innervate skeletal muscles (involuntary control) (voluntary control)  The spinal cord is a long, delicate cord of nervous tissue that is responsible for transmitting nerve signals to and from the brain. The cord lies in the vertebral canal and is protected by the bony structures of the vertebral column https://www.cervicaldisc.com A pair of SPINAL NERVES emerge from the spinal cord at each vertebral/spinal level Spinal nerves leave the vertebral column by passing through the intervertebral foramen (and can easily become squashed / “impinged”)  The human vertebral column consists of Spinal Nerves 33 bones called vertebrae. (24 are separate allowing movement, 9 Brain are fused together) (PNS) 8 pairs of 7 cervical vertebrae cervical spinal C nerves 12 pairs of thoracic 12 Thoracic vertebrae spinal nerves T 31 pairs of Spinal Nerves 5 pairs of lumbar spinal L 5 lumbar vertebrae nerves 5 pairs of sacral spinal S 5 sacral vertebrae (fused) nerves 1 pair of 4 vertebrae fuse together C to form the coccyx coccygeal spinal nerves  Formation of a “Mixed” Spinal Nerve Dorsal Root Ganglion (cluster of cell bodies - sensory neurones) Dorsal Root Afferent (sensory) fibres Posterior ‘Mixed’ Spinal Nerve Dorsal Ramus Pass posteriorly to supply the skin and deep muscles of the back Cross section of Grey the spinal Matter cord Ventral Ramus Supplying the anterolateral parts of the trunk and limbs. Grey and White Rami Making connections with the ANS via the sympathetic ganglion Ventral Root Efferent (motor) fibres Anterior https://en.Wikipedia.org/wiki/Dorsal_root_of_spinal_nerve Emily Grant – Division of Physiotherapy Dermatome DERMATOME = the area of skin supplied by the afferent (sensory) fibres of a single spinal nerve Impaired sensation with a specific dermatomal pattern indicates a problem with the spinal root/ spinal nerve You will have an opportunity to practice clinical testing of dermatomes within your anatomy practical classes. Emily Grant – Division of Physiotherapy  The list below details which movement(s) have Myotome the strongest association with each myotome C2 Neck flexion C3 Lateral flexion of the neck C4 Shoulder elevation Myotome = a group of C5 Shoulder abduction muscles innervated by the C6 Elbow flexion with wrist extension efferent (motor) fibres of a C7 Elbow extension single spinal nerve C8 Finger flexion Changes in muscle strength within a T1 Finger abduction particular myotome may indicate damage L2 Hip flexion to a particular spinal nerve root L3 Knee extension You will have the opportunity to practice L4 Ankle dorsiflexion clinical testing of myotomes within your L5 Great toe extension anatomy practical classes S1 Ankle plantar flexion Emily Grant – Division of Physiotherapy  Some of the ventral rami of spinal nerves come together to from a bundle or PLEXUS that then branches back out to form named peripheral nerves. Brain There are 4 plexuses The cervical plexus creates named peripheral nerves that innervate the Spinal Nerves C1- C4 back of the head, the neck the form the Cervical Plexus shoulders and a muscle called the C diaphragm e.g. PHRENIC NERVE Spinal Nerves C5- T1 form the Brachial Plexus The brachial plexus creates named peripheral nerves that innervate the Thoracic nerves do not form a upper limbs e.g. MEDIAN NERVE T plexus but innervate the RADIAL NERVE intercostal muscles and lower ULNAR NERVE aspects on the abdomen Spinal Nerves L1-L4 The lumbar plexus creates named peripheral nerves that innervate the L form the Lumbar Plexus front (anterior) and sides (lateral) aspects of the thigh Spinal Nerves L4- S4 e.g. FEMORAL NERVE S form the Sacral Plexus The sacral plexus creates named peripheral nerves that innervate the C back (posterior) of the thigh and everything below the knee e.g. SCIATIC NERVE e.g. Cervical Plexus Each named peripheral nerve has a root value that indicates which spinal nerve roots have contributes to that nerve: e.g. the root value of the phrenic nerve is C3/4/5 “C3,4 & 5 keeps the diaphragm alive” Emily Grant – Division of Physiotherapy Common Peripheral Nerves & Their Nerve Root Derivation NB. There are many, many named peripheral nerves – you are not expected to know them all, but here are some examples. Ultimately you will need to learn the nerve supply to some of the main muscle groups (anatomy modules). Most peripheral nerves contain fibres from 2, 3, 4, or even 5 spinal nerves Axillary Nerve C5, 6 Subscapular Nerve C5,6 Medial cutaneous nerve of the forearm C8, T1 Radial Nerve C5, 6, 7, 8 T1 Median Nerve C6, 7, 8, T1 Lateral cutaneous nerve of the thigh L2, 3 Femoral Nerve L2, 3, 4 Sciatic Nerve L4, 5 S1, 2, 3 Common Peroneal Nerve L4, 5 S1, 2 Anatomical Structure of a Peripheral Nerve Peripheral Nerve Epineurium (dense, irregular connective tissue) Fascicle (a bundle of individual neurones) Axons Perineurium (individual (myelinated) axons) (cell layer around a fascicle) Endoneurium (connective tissue in between axons https://axogenic.eu Emily Grant – Division of Physiotherapy Revision Checklist Key Terms & Concepts ▪ Afferent (sensory) ▪ Mixed Spinal Nerve ▪ Efferent (motor) ▪ Ramus / Rami ▪ Central Nervous System (CNS) ▪ Plexus ▪ Peripheral Nervous System (PNS) ▪ Cervical ▪ Brachial ▪ Autonomic Nervous System (ANS) ▪ Lumbar ▪ Nerves ▪ Sacral ▪ Ganglion ▪ Root Value ▪ Special senses ▪ Dermatome ▪ Somatic sensation ▪ Myotome ▪ Spinal Cord ▪ Epineurium ▪ Grey matter ▪ Endoneurium ▪ White matter ▪ Ventral Root (anterior - motor) ▪ Perineurium ▪ Dorsal Root (posterior - sensory) ▪ Fascicle Emily Grant – Division of Physiotherapy