BIOH111 o Cell Module o Tissue Module o Skeletal system o Muscle system o Nervous system o Endocrine system o Integumentary system Endeavour College of Natural Health endeavour.edu.au 1
Textbook and required/recommended readings o Chapter 13, Principles of Anatomy and Physiology, Tortora et al, 14 th edition Endeavour College of Natural Health endeavour.edu.au 2
BIOH111 NERVOUS SYSTEM MODULE o Session 13 (Lectures 25 and 26) Organisation and histology of the nervous system o Session 14 (Lectures 27 and 28) Function of neurons: conduction of nerve impulses o Session 15 (Lectures 29 and 30) Spinal cord and spinal nerves o Session 16 (Lectures 31 and 32) CNS: Brain anatomy and function o Session 17 (Lectures 33 and 34) Autonomic nervous system: anatomy and function o Session 18 (Lectures 35 and 36) Sensations o Session 19 (Lectures 37 and 38) Special senses Endeavour College of Natural Health endeavour.edu.au 3
BIOH111 Lectures 29 and 30 Spinal cord and spinal nerves Department of Bioscience endeavour.edu.au
Lecture 29: Objectives Anatomy and function of spinal cord: Describe structure and functions of spinal cord, including supporting system Describe external and internal anatomy of spinal cord Describe and discuss arrangement and functions of grey and white matter in the spinal cord Describe and understand reflex arcs Describe and understand ascending and descending tracts Understand the relationship between functions of the spinal cord grey and white matter in conducting nerve impulses Lectures 30: Anatomy and function of spinal nerves: Describe structure, origin and function of spinal nerves Describe anatomy and understand function of plexi Describe dermatomes and understand their importance Endeavour College of Natural Health endeavour.edu.au 5
FUNCTIONS OF SPINAL CORD o The spinal cord and spinal nerves mediate reactions to environmental changes. 1. Processes reflexes 2. Site for integration of EPSPs and IPSPs that arise locally or are triggered by nerve impulses from the periphery and brain. 3. Conduction pathway for sensory and motor nerve impulses. Endeavour College of Natural Health endeavour.edu.au 6
NERVOUS SYSTEM DIVISIONS - REVISION Endeavour College of Natural Health endeavour.edu.au 7
REVISION SPINAL CORD SUPPORT SYSTEMS o The spinal cord is protected and supported by: 1. Vertebral column: provides a bony covering and support of the spinal cord (revision: BIOH111 session 8) 2. Meninges: connective tissue covering 3. Cerebrospinal fluid Endeavour College of Natural Health endeavour.edu.au 8
MENINGES o 3 coverings that run continuously around the spinal cord and brain. Dura mater: outer layer; dense irregular tissue Arachnoids: middle layer; spider web of collagen fibers Pia mater: inner meninx; thin, transparent connective tissue layer that adheres to the surface of the spinal cord and brain Endeavour College of Natural Health endeavour.edu.au 9
CEREBROSPINAL FLUID (CSF) o Cerebrospinal fluid (CSF) is a clear, colorless liquid that protects the spinal cord and brain against chemical and physical injuries. o Structure: Clear liquid containing glucose, proteins, & ions; 80-150 ml; produced by ependymal cells; production rate same as reabsorption rate (20ml/hour); contained within Subarachnoid space o Functions: 1. mechanical protection: floats cord & softens impact with bony walls 2. chemical protection: optimal ionic concentrations for action potentials 3. circulation: nutrients and waste products to and from bloodstream o Clinical applications: meningitis and spinal tap Endeavour College of Natural Health endeavour.edu.au 10
EPENDYMAL CELLS - revision synapticplasticity.wix.com o Structure: columnar cells with apical cilia o Functions: form epithelial membrane lining cerebral cavities & central canal produce cerebrospinal fluid (CSF) Endeavour College of Natural Health endeavour.edu.au 11
EXTERNAL ANATOMY OF THE SPINAL CORD o Flattened cylinder; 16-18 Inches long & 3/4 inch diameter o In adult ends at L2; in newborn ends at L4; growth of cord stops at age 5 o Begins as a continuation of medulla oblongata and terminates at about the second lumbar vertebra in an adult; segmented into spinal segments - origin points for spinal nerves o Cervical and lumbar enlargements: serve as points of origin for nerves to the extremities o Conus medullaris: tapered portion of the spinal cord; spinal tap area below conus medullaris Endeavour College of Natural Health endeavour.edu.au 12
INTERNAL ANATOMY OF THE SPINAL CORD SPINAL SEGMENT posterior median sulcus gray matter white matter anterior median fissure o General structure: gray matter shaped like the letter H or a butterfly surrounded by the white matter o Anterior median fissure and the posterior median sulcus divide spinal cord into right and left sides. Endeavour College of Natural Health endeavour.edu.au 14
GRAY MATTER OF THE SPINAL CORD o Structure: paired dorsal and ventral gray horns lateral horns only present in thoracic spinal cord gray commissure surrounds central canal nuclei and unmyelinated axons of association and motor neurons dorsal gray horns o Function: receives and integrates incoming and outgoing information; reflex arcs ventral gray horns central canal Endeavour College of Natural Health endeavour.edu.au 15
o REFLEXES AND REFLEX ARCS Reflex: fast, predictable, automatic response to changes in the environment that helps to maintain homeostasis; 4 types: 1. Spinal integration occurs in spinal grey matter; e.g. patellar reflex 2. Cranial integration occurs in brain stem; e.g. eye movement while reading 3. Somatic involves contraction of skeletal muscles 4. Autonomic not consciously perceived; e.g. heart rate o Reflex arc: specific nerve impulse pathway that produces a reflex; include at least one synapse Endeavour College of Natural Health endeavour.edu.au 16
o 5 components: REFLEX ARC 1. Sensory receptor responds to stimulus 2. Sensory neuron conducts nerve impulse from receptor to integrating center 3. Integrating center CNS region(s) relay impulses from sensory to motor neurons (EPSPs and IPSPs revision session 14 BIOH111) 4. Motor neuron - conducts nerve impulse from integrating center to effector (EPSPs and IPSPs) 5. Effector responds to stimulus (EPSPs and IPSPs) 3 4 5 2 1 o Somatic spinal reflexes: stretch reflex, tendon reflex, flexor (withdrawal) reflex, and crossed extensor reflex; all exhibit reciprocal innervation. Endeavour College of Natural Health endeavour.edu.au 17
Stretch (Patellar) Reflex Signal Reflex arc type Reciprocal innervation muscle spindle signals stretch of muscle Monosynaptic, ipsilateral Polysynaptic; interneuron antagonistic muscles relax as part of reflex Effect motor neuron activated & muscle contracts Function Feedback mechanism to control muscle length by causing muscle contraction Endeavour College of Natural Health endeavour.edu.au 18
Tendon Reflex Signal Reflex arc type Reciprocal innervation stretching of tendon Polysynaptic ipsilateral Polysynaptic; interneuron contraction of ipsilateral muscle group Effect Inhibitory neuron is stimulated; motor neuron is hyperpolarized and muscle relaxes Function feedback mechanism to control muscle tension by causing muscle relaxation when muscle force becomes too extreme Endeavour College of Natural Health endeavour.edu.au 19
Flexor (Withdrawal) Reflex Signal pain Reflex arc type Reciprocal innervation Effect Function Intersegmental; Ipsilateral Polysynaptic; interneuron contraction of ipsilateral muscle group - Interneurons branch to different spinal cord segments - Motor fibers in several segments are activated - More than one muscle group activated to lift foot off away from pain protective withdrawal reflex that moves a limb to avoid pain Endeavour College of Natural Health endeavour.edu.au 20
Crossed Extensor Reflex Signal pain Reflex arc type Reciprocal innervation Effect Intersegmental; contralateral Polysynaptic; extensors contract flexors relax Contralateral extensor muscles are stimulated by interneurons to hold up the body weight Function protective withdrawal reflex that moves a limb to avoid pain Endeavour College of Natural Health endeavour.edu.au 21
WHITE MATTER OF THE SPINAL CORD o Structure: White matter is divided into columns: distinct bundles of myelinated axons of motor and sensory neurons that have a common origin, destination and function; 3 pairs: dorsal, lateral and anterior Bundles in columns are called tracts; 2 types: ascending and descending o Function: tracts are highways for nerve impulse conduction to and from the brain Dorsal columns Lateral columns Anterior columns Endeavour College of Natural Health endeavour.edu.au 22
SENSORY AND MOTOR TRACTS sensory (ascending) tracts motor (descending) tracts o Sensory (ascending) tracts conduct nerve impulses toward the brain. lateral and anterior spinothalamic tracts and posterior column tract o Motor (descending) tracts conduct impulses down the cord. Direct pathways: lateral and anterior corticospinal and corticobulbar tracts Indirect pathways: rubrospinal, tectospinal, and vestibulospinal tracts Endeavour College of Natural Health endeavour.edu.au 23
Naming of tracts indicates position & direction of signal Example: anterior spinothalamic tract impulses travel from spinal cord towards brain (thalamus) found in anterior part of spinal cord Example: anterior corticospinal tract impulses travel from found in WHAT part of the spinal cord Endeavour College of Natural Health endeavour.edu.au 24
Clinical application: Babinski sign o Checking a patient s reflexes may help to detect disorders/injury o Plantar flexion reflex -- stroke the lateral margin of the sole normal response is curling under the toes abnormal response or response of children under 18 months is called Babinski sign (upward fanning of toes due to incomplete myelination in child) Endeavour College of Natural Health endeavour.edu.au 27
Work in groups of 2-4: follow the neurons below and comment on the structures encountered and integrate functions between grey and white matter in spinal cord and brain with sensation and effect. Endeavour College of Natural Health endeavour.edu.au 28
Lecture 29: Objectives Anatomy and function of spinal cord: Describe structure and functions of spinal cord, including supporting system Describe external and internal anatomy of spinal cord Describe and discuss arrangement and functions of grey and white matter in the spinal cord Describe and understand reflex arcs Describe and understand ascending and descending tracts Understand the relationship between functions of the spinal cord grey and white matter in conducting nerve impulses Lectures 30: Anatomy and function of spinal nerves: Describe structure, origin and function of spinal nerves Describe anatomy and understand function of plexi Describe dermatomes and understand their importance Endeavour College of Natural Health endeavour.edu.au 29
SPINAL CORD - ORIGIN FOR SPINAL NERVES dorsal root ganglion o Spinal nerves begin as roots. ventral (anterior) root(lets) o Dorsal or posterior root - incoming sensory fibers dorsal root ganglion (swelling): cell bodies of sensory nerves o Ventral or anterior root - outgoing motor fibers sensory neurons IN motor neurons OUT skeletal muscles cardiac/smooth muscle and glands Endeavour College of Natural Health endeavour.edu.au 30
SPINAL NERVES o Connect CNS to sensory receptors, muscles, and glands and are part of the peripheral nervous system. o Structure: mixed nerves: connected to spinal cord via posterior root (sensory axons) and anterior root (motor axons) o 31 pairs of spinal nerves: named and numbered according to the region and level of the spinal cord from which they emerge: 8 pairs of cervical nerves 12 pairs of thoracic nerves 5 pairs of lumbar nerves 5 pairs of sacral nerves 1 pair of coccygeal nerves o Function: paths of communication between the spinal cord and most of the body Endeavour College of Natural Health endeavour.edu.au 31
SPINAL NERVES CONNECTIVE TISSUE o Spinal nerve axons are grouped within connective tissue sheathes fiber is a single axon within an endoneurium fascicle is a bundle of fibers within a perineurium nerve is a bundle of fascicles within an epineurium o Numerous blood vessels found within the connective tissue Endeavour College of Natural Health endeavour.edu.au 32
BRANCHING OF SPINAL NERVE o Spinal nerves branch into: dorsal rami - supply skin & muscles of back ventral rami - form plexus that supply anterior trunk & limbs meningeal rami - supply meninges, vertebrae & blood vessels Endeavour College of Natural Health endeavour.edu.au 33
NERVE PLEXUS o Structure: ventral rami of spinal nerves forms a nerve network or plexus found in neck, arm, low back & sacral regions; corresponds to 4 plexi: cervical, brachial, lumbar and sacral Intercostal or thoracic nerves do not form pexi and innervate intercostal spaces (e.g. T7 to T12 supply abdominal wall) roots nerves Picture of the plexus example Endeavour College of Natural Health endeavour.edu.au 34
Cervical Plexus o Ventral rami of spinal nerves: C1 to C5 o Supplies parts of head, neck & shoulders o Phrenic nerve (C3-C5) keeps diaphragm alive o Damage to cord above C3 causes respiratory arrest Endeavour College of Natural Health endeavour.edu.au 35
Brachial plexus o Ventral rami of spinal nerves: C5 to T1 o Supplies shoulder & upper limb o Passes superior to first rib and under clavicle Axillary n. = deltoid & teres m. Musculocutaneous n. = elbow flexors Radial n. = shoulder & elbow extensors Median & ulnar nerves. = flexors of wrist & hand; injury results in carpal tunnel and claw hand median nerve ulnar nerve Endeavour College of Natural Health endeavour.edu.au 36
Lumbar plexus o Ventral rami of spinal nerves: L1 to L4 o Supplies abdominal wall, external genitals & anterior/medial thigh o Injury to femoral nerve causes inability to extend leg & loss of sensation in thigh Endeavour College of Natural Health endeavour.edu.au 37
Sacral plexus o Ventral rami of spinal nerves: L4- L5 & S1-S4 o Anterior to the sacrum o Supplies buttocks, perineum & part of lower limb Sciatic nerve = L4 to S3 supplies post thigh & all below knee; injury results in pain that extends from the buttock down the back of the leg; sciatic nerve injury can occur due to a herniated disc, dislocated hip, osteoarthritis, pressure from the uterus during pregnancy or an improperly administered gluteal injection. sciatic nerve Endeavour College of Natural Health endeavour.edu.au 38
DERMATOMES o Skin over the entire body is segmented into dermatomes. All dermatomes are supplied by spinal nerves that carry somatic sensory nerves impulses into the spinal cord. o All spinal nerves except C1 innervate specific dermatomes. o Dermatomes help physician determine which segment of the spinal cord or which spinal nerve is malfunctioning. NOTE: Skin on face supplied by Cranial Nerve V Think back to tissues which tissue type do you think would be used by skin for innervation? Endeavour College of Natural Health endeavour.edu.au 39
Work in groups of 3-4 and identify processes you learned about in each of the spots labelled 1-6. HINT: you should now be able to identify all points Endeavour College of Natural Health endeavour.edu.au 40
Clinical application: DISORDERS OF SPINAL NERVES o Neuritis: inflammation of nerves; caused by injury, vitamin deficiency or poison o Shingles: infection of peripheral nerve by chicken pox virus; causes pain, skin discoloration, line of skin blisters o Poliomyelitis: viral infection causing motor neuron death and possible death from cardiac failure or respiratory arrest o Erb-Duchene palsy: waiter s tip position - fall on shoulder o Radial nerve injury: improper deltoid injection or tight cast - wrist drop o Median nerve injury: numb palm & fingers; inability to pronate & flex fingers o Ulnar nerve injury (clawhand): inability to adduct/abduct fingers, atrophy of interosseous o Long thoracic nerve injury (winged scapula): paralysis of serratus anterior, can t abduct above horizontal Endeavour College of Natural Health endeavour.edu.au 42
COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been reproduced and communicated to you by or on behalf of the Endeavour College of Natural Health pursuant to Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Endeavour College of Natural Health endeavour.edu.au 43