BIOH111 o Cell Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system Endeavour College of Natural Health endeavour.edu.au 1
Textbook and required/recommended readings o Spinal cord anatomy: Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 13; section 13.1 o Spinal cord physiology: Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 13; section 13.3 Endeavour College of Natural Health endeavour.edu.au 2
BIOH111 NERVOUS SYSTEM MODULE o Session 15 (Lectures 27 and 28) Organisation and histology of the nervous system o Session 16 (Lectures 29 and 30) Function of neurons: conduction of nerve impulses o Session 17 (Lectures 31 and 32) CNS: Brain anatomy and function o Session 18 (Lectures 33 and 34) Sensations and special senses o Session 19 (Lectures 35 and 36) Spinal cord anatomy and physiology o Session 20 (Lectures 37 and 38) Spinal nerves and somatic sensory and motor pathways o Session 21 (Lectures 39 and 40) Autonomic nervous system: anatomy and function Endeavour College of Natural Health endeavour.edu.au 3
BIOH111 Lectures 35 and 36 Spinal cord anatomy and physiology Department of Bioscience endeavour.edu.au
Objectives Lecture 35: 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 Lecture 36: 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 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: 1. Dura mater: outer layer; dense irregular tissue 2. Arachnoids: middle layer; spider web of collagen fibers 3. 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) - revision 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
Objectives Lecture 35: 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 Lecture 36: 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 Endeavour College of Natural Health endeavour.edu.au 16
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 17
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) 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 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 18 2 1
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 19
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 20
Not assessable 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 21
Not assessable 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 22
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 23
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 24
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 towards found in WHAT part of the spinal cord Endeavour College of Natural Health endeavour.edu.au 25
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 28
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 29
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