BIOH111. Cell Module Tissue Module Integumentary system Skeletal system Muscle system Nervous system Endocrine system. endeavour.edu.

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1 BIOH111 Cell Module Tissue Module Integumentary system Skeletal system Muscle system Nervous system Endocrine system

2 Textbook and required/recommended readings o Spinal nerves anatomy: Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 13; section 13.2 o Somatic sensory pathways: Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 16; section 16.3 o Somatic motor pathways: Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 16; section 16.4

3 BIOH111 NERVOUS SYSTEM MODULE Session 15 (Lectures 27 and 28) Organisation and histology of the nervous system Session 16 (Lectures 29 and 30) Function of neurons: conduction of nerve impulses Session 17 (Lectures 31 and 32) CNS: Brain anatomy and function Session 18 (Lectures 33 and 34) Sensations and special senses Session 19 (Lectures 35 and 36) Spinal cord anatomy and physiology Session 20 (Lectures 37 and 38) Spinal nerves and somatic sensory and motor pathways Session 21 (Lectures 39 and 40) Autonomic nervous system: anatomy and function

4 BIOH111 Lectures 37 and 38 Spinal nerves and somatic sensory and motor pathways Department of Bioscience

5 Objectives Lectures 37: 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 Lecture 38: Somatic sensory pathways Discuss the somatic sensory pathways: their organisation and function Somatic motor pathways Discuss the somatic motor pathways: their organisation and function Integrative roles of cerebellum Analyse the concept of sleep and wakefulness Analyse the concept of learning and memory

(DRG; swelling): cell bodies of sensory nerves o Ventral or anterior root - outgoing motor fibers

6 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 (DRG; 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 6

7 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 roots not in line with corresponding verterbrae so they form cauda equina o Function: paths of communication between the spinal cord and most of the body

fascicle is a bundle of fibers within a perineurium nerve is a bundle of

9 SPINAL NERVES CONNECTIVE TISSUE ospinal 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 onumerous blood vessels found within the connective tissue

rami - form plexus that supply anterior trunk & limbs

10 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

Intercostal or thoracic nerves do not form pexi and innervate intercostal spaces (e.g.

11 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 NERVE PLEXUS 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 11

12 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 12

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.

13 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 13

14 Lumbar plexus o Ventral rami of spinal nerves: L1 to L4 o Supplies abdominal wall, external genitals & anterior/medial thigh Injury to femoral nerve causes inability to extend leg & loss of sensation in thigh

down the back of the leg; sciatic nerve injury can occur due to a herniated disc, dislocated hip, osteoarthritis, pressure from

15 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 15

DERMATOMES oskin 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.

16 DERMATOMES oskin 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. oall spinal nerves except C1 innervate specific dermatomes. odermatomes help physician determine which segment of the spinal cord or which spinal nerve is malfunctioning. o 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?

17 Clinical application: DISORDERS OF SPINAL NERVES Neuritis: inflammation of nerves; caused by injury, vitamin deficiency or poison Shingles: infection of peripheral nerve by chicken pox virus; causes pain, skin discoloration, line of skin blisters Poliomyelitis: viral infection causing motor neuron death and possible death from cardiac failure or respiratory arrest Erb-Duchene palsy: waiter s tip position - fall on shoulder Radial nerve injury: improper deltoid injection or tight cast - wrist drop Median nerve injury: numb palm & fingers; inability to pronate & flex fingers Ulnar nerve injury (clawhand): inability to adduct/abduct fingers, atrophy of interosseous Long thoracic nerve injury (winged scapula): paralysis of serratus anterior, can t abduct above horizontal

18 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

SENSORY AND MOTOR TRACTS sensory (ascending) tracts motor (descending) tracts osensory (ascending) tracts conduct nerve impulses toward the brain.

19 SENSORY AND MOTOR TRACTS sensory (ascending) tracts motor (descending) tracts osensory (ascending) tracts conduct nerve impulses toward the brain. lateral and anterior spinothalamic tracts and posterior column tract omotor (descending) tracts conduct impulses down the cord. Direct pathways: lateral and anterior corticospinal and corticobulbar tracts Indirect pathways: rubrospinal, tectospinal, and vestibulospinal tracts

20 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

21 Objectives Lectures 37: 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 Lecture 38: Somatic sensory pathways Discuss the somatic sensory pathways: their organisation and function Somatic motor pathways Discuss the somatic motor pathways: their organisation and function Integrative roles of cerebellum Analyse the concept of sleep and wakefulness Analyse the concept of learning and memory

22 SOMATIC SENSORY PATHWAYS Somatic sensory pathways relay information from somatic receptors to the primary somatosensory area in the cerebral cortex (postcentral gyrus). The pathways consist of three neurons: 1. First-order neuron: conduct impulses to the CNS (brainstem or spinal cord); either spinal or cranial nerves 2. Second-order neuron: conduct impulses from brain stem or spinal cord to thalamus; cross over to opposite side of body 3. Third-order neuron: conduct impulses from thalamus to primary somatosensory cortex

of transverse white fibers longitudinal fissure o Each hemisphere divided in 4 lobes:

23 THE CEREBRUM STRUCTURE - revision o Divided into 2 hemispheres (right and left halves): separated by the longitudinal fissure internally connected by the corpus callosum, a bundle of transverse white fibers longitudinal fissure o Each hemisphere divided in 4 lobes: separated by the fissures and sulci Frontal, parietal, occipital and temporal Insula: fifth part, hidden

24 SENSORY AREAS - revision Precentral gyrus Postcentral gyrus

SOMATOSENSORY MAP (POSTCENTRAL GYRUS) orelative sizes of cortical areas proportional to number of sensory receptors proportional to the sensitivity of each

25 SOMATOSENSORY MAP (POSTCENTRAL GYRUS) orelative sizes of cortical areas proportional to number of sensory receptors proportional to the sensitivity of each part of the body ocan be modified with learning e.g. learn to read Braille & will have larger area representing fingertips Endeavour College of Natural Health 26

26 Examples of sensory pathways Divided according to the initial stimulus: General pathways: posterior column-medial lemniscus and anterolateral (spinothalamic) pathways Special senses pathways olfactory, gustatory, vision, auditory and equilibrium

General pathway: Posterior column-medial lemniscus pathway o Sensations conducted: proprioception, vibration, discriminative touch, weight discrimination; posture, balance and coordination of skilled

27 General pathway: Posterior column-medial lemniscus pathway o Sensations conducted: proprioception, vibration, discriminative touch, weight discrimination; posture, balance and coordination of skilled movements o Pathway: first order (signals travel up spinal cord in posterior column) second order (fibers cross-over in medulla to become the medial lemniscus pathway ending in thalamus third order (thalamic fibers reach cortex) Endeavour College of Natural Health 28

General pathway: Anterolateral (spinothalamic) pathways o Sensations conducted: pain & temperature (lateral tract); tickle, itch, crude touch & pressure (anterior tract) o Pathway: First order (first

28 General pathway: Anterolateral (spinothalamic) pathways o Sensations conducted: pain & temperature (lateral tract); tickle, itch, crude touch & pressure (anterior tract) o Pathway: First order (first cell body in DRG with synapses in cord) second order (cell body in gray matter of cord, sends fibers to other side of cord & up through white matter to synapse in thalamus); third order (cell body in thalamus projects to cerebral cortex) Endeavour College of Natural Health 29

Special senses pathway - olfactory pathway First order: axons from olfactory receptors form the olfactory nerves (Cranial nerve I) that synapse in the olfactory bulb Second order: neurons within the

29 Special senses pathway - olfactory pathway First order: axons from olfactory receptors form the olfactory nerves (Cranial nerve I) that synapse in the olfactory bulb Second order: neurons within the olfactory bulb form the olfactory tract Third order: olfactory tract synapses on primary olfactory area of temporal lobe Other pathways lead to the frontal lobe (area 11) where identification of the odour occurs

Special senses pathway - gustatory pathway First order: gustatory fibers found in cranial nerves V (trigeminal) VII (facial) serves anterior 2/3 of tongue IX (glossopharyngeal) serves posterior 1/3

30 Special senses pathway - gustatory pathway First order: gustatory fibers found in cranial nerves V (trigeminal) VII (facial) serves anterior 2/3 of tongue IX (glossopharyngeal) serves posterior 1/3 of tongue X (vagus) serves palate & epiglottis Second order: signals travel to thalamus or limbic system & hypothalamus Third order: taste fibers extend from the thalamus to the primary gustatory area on parietal lobe of the cerebral cortex

31 Special senses pathway - vision pathway First order Second order Third order

32 Special senses pathway - auditory pathway Cochlear branch of vestibulocochlear (VIII) nerve First order Primary auditory area in cerebral cortex Third order Same and cross-over area in medula Second order

Special senses pathway - equilibrium pathway First order: vestibular branch fibers of CN VIII enter the brain stem and terminate in the medulla (most) or cerebellum (some) Second order: fibers from

33 Special senses pathway - equilibrium pathway First order: vestibular branch fibers of CN VIII enter the brain stem and terminate in the medulla (most) or cerebellum (some) Second order: fibers from these areas connect to: cranial nerves: control eye and head and neck movements vestibulospinal tract: adjusts postural skeletal muscle contractions Third order: to cerebellum and then to the motor areas of the cerebral cortex Vestibular branch of vestibulocochlear (VIII) nerve Motor area in cerebral cortex Connections to other nerves in medula

34 Clinical application SYPHILIS Syphilis causes a progressive degeneration of the posterior portions of the spinal cord. Sexually transmitted disease caused by bacterium Treponema pallidum. Third clinical stage known as tertiary syphilis Progressive degeneration of posterior portions of spinal cord & neurological loss loss of somatic sensations proprioceptive impulses fail to reach cerebellum People watch their feet while walking, but are still uncoordinated and jerky

35 SOMATIC MOTOR PATHWAYS o Somatic motor pathways start in primary motor cortex (precental gyrus): 1. direct pathway from cerebral cortex to spinal cord & out to muscles 2. indirect pathway includes synapses in basal ganglia, thalamus, reticular formation & cerebellum o Functions: 1. Control of body movement: motor portions of cerebral cortex; initiate & control precise movements 2. Muscle tone & integration of semivoluntary automatic movements: basal ganglia 3. Smooth movements & helps maintain posture & balance: cerebellum

36 Direct pathway Indirect pathway

37 MOTOR AREAS - revision

38 PRIMARY MOTOR CORTEX (PRECENTRAL GYRUS) orelative sizes of cortical areas proportional to number of motor units proportional to the sensitivity of each part of the body oadjacent to somatosensory cortex Endeavour College of Natural Health 39

39 Direct pathway

40 DIRECT MOTOR PATHWAYS othe direct pathways (pyramidal tracts) include: lateral and anterior corticospinal tracts corticobulbar tracts o90% of fibers decussate in the medulla oterminate on interneurons which synapse on lower motor neurons in either: nuclei of cranial nerves anterior horns of spinal cord ofunction: convey impulses from the cerebral cortex that result in precise muscular movements.

41 Pyramidal pathways olateral corticospinal tracts cortex, cerebral peduncles, 90% decussation of axons in medulla, tract formed in lateral column. Function: skilled movements (hands & feet) oanterior corticospinal tracts the 10% of axons that do not cross Function: controls neck & trunk muscles ocorticobulbar tracts cortex to nuclei of CNs III, IV, V, VI, VII, IX, X, XI & XII Function: movements of eyes, tongue, chewing, expressions & speech Endeavour College of Natural Health 42

42 Clinical application o Amyotrophic Lateral Sclerosis (ALS) is a disease hat attacks motor areas of the cerebral cortex, axons of upper motor neurons and cell bodies of lower motor neurons. It causes progressive muscle weakness. There are several theories as to its cause. While there is no cure, several drugs are used to treat the symptoms. o Flaccid paralysis = damage lower motor neurons no voluntary movement on same side as damage no reflex actions muscle limp & flaccid decreased muscle tone o Spastic paralysis = damage upper motor neurons paralysis on opposite side from injury increased muscle tone exaggerated reflexes

43 Indirect pathway

44 INDIRECT PATHWAYS oindirect or extrapyramidal pathways include all somatic motor tracts other than the corticospinal and corticobulbar tracts. ocomplex polysynaptic circuits involve the motor cortex, basal ganglia, thalamus, cerebellum, reticular formation, and nuclei in the brain stem. odescend in spinal cord as 5 major tracts indirect tracts are the rubrospinal, tectospinal, vestibulospinal, lateral reticulospinal and medial reticulospinal tracts. oall 5 tracts end at interneurons or lower motor neurons

46 Indirect pathway via basal ganglia Circuit structure: cerebral cortex basal ganglia thalamus cortex ofunction: initiating and terminating movement; also: suppress unwanted movements influences aspects of cortical function including sensory, limbic, cognitive, and linguistic functions. helps to program automatic movement sequences (e.g. walking and arm swinging or laughing at a joke) set muscle tone by inhibiting other motor circuits odamage to the basal ganglia results in: uncontrollable, abnormal body movements, often accompanied by muscle rigidity and tremors Diseases: Parkinson disease and Huntington disease

47 Indirect pathway via cerebellum Circuit structure: cerebral cortex cerebellum brain stem spinal cord ofunction: active in learning and performing rapid, coordinated, highly skilled movements and in maintaining proper posture and equilibrium. The four aspects of cerebellar function: monitoring intent for movement, monitoring actual movement, comparing intent with actual performance, and sending out corrective signals odamage to the cerebellum is evidenced by ataxia and intention tremors.

48 Lower motor neurons o Lower motor neurons extend from the brain stem or spinal cord to skeletal muscles. o Also called the final common pathway: many regulatory mechanisms converge on these peripheral neurons

49 FINAL COMMON PATHWAY o Lower motor neurons receive signals from both direct & indirect upper motor neurons o Sum total of all inhibitory & excitatory signals determines the final response of the lower motor neuron & the skeletal muscles Endeavour College of Natural Health 51

50 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 most of the points

51 INTEGRATIVE FUNCTIONS OF THE CEREBRUM othe integrative functions include sleep and wakefulness, memory, and emotional responses. ocontrolled by Reticular Activating System (RAS) Arousal, or awakening from a sleep, involves increased activity of the RAS. When the RAS is activated, the cerebral cortex is also activated and arousal occurs. The result is a state of wakefulness called consciousness.

52 WAKEFULNESS AND SLEEP ocircadian rhythm 24 hour cycle of sleep and awakening established by hypothalamus oeeg recordings show large amount of activity in cerebral cortex when awake

53 SLEEP oduring sleep, a state of altered consciousness or partial unconsciousness from which an individual can be aroused by different stimuli, oduring sleep activity in the RAS is very low. onormal sleep consists of two types: non-rapid eye movement sleep (NREM) or slow wave sleep consists of four stages, each of which gradually merges into the next. rapid eye movement sleep (REM) Most dreaming occurs during rapid eye movement sleep.

54 LEARNING AND MEMORY olearning is the ability to acquire new knowledge or skills through instruction or experience. omemory is the process by which that knowledge is retained over time. ofor an experience to become part of memory, it must produce persistent functional changes that represent the experience in the brain. othe capability for change with learning is called plasticity.

55 LEARNING AND MEMORY omemory occurs in stages over a period and is described as immediate memory, short term memory, or long term memory. Immediate memory is the ability to recall for a few seconds. Short-term memory lasts only seconds or hours and is the ability to recall bits of information; it is related to electrical and chemical events. Long-term memory lasts from days to years and is related to anatomical and biochemical changes at synapses.

56 Clinical application AMNESIA oamnesia refers to the loss of memory oanterograde amnesia is the loss of memory for events that occur after the trauma; the inability to form new memories. oretrograde amnesia is the loss of memory for events that occurred before the trauma; the inability to recall past events.

57 Clinical application SPINAL CORD INJURY o Spinal cord injury can be due to damage in a number of ways, such as compression or transection, and the location and extent of damage determines the type and degree of loss in neural abilities. tumor, herniated disc, clot, trauma o Paralysis monoplegia is paralysis of one limb only diplegia is paralysis of both upper or both lower hemiplegia is paralysis of one side quadriplegia is paralysis of all four limbs o Spinal shock is loss of reflex function (areflexia) slow heart rate, low blood pressure, bladder problem reflexes gradually return

58 Clinical application CEREBRAL PALSY oloss of motor control and coordination odamage to motor areas of the brain infection of pregnant woman with rubella virus radiation during fetal life temporary lack of O2 during birth onot a progressive disease, but irreversible

59 Clinical application PARKINSON DISEASE o Parkinson s disease is a progressive degeneration of CNS neurons of the basal nuclei region due to unknown causes that decreases dopamine neurotransmitter production. Environmental toxins may be the cause in some cases o Neurons from the substantia nigra do not release enough dopamine onto basal ganglia tremor, rigidity, bradykinesia (slow movement) or hypokinesia (decreasing range of movement) may affect walking, speech, and facial expression o Treatments drugs to increase dopamine levels (L-Dopa), or to prevent its breakdown acetylcholine inhibitors

BIOH111. o Cell Module o Tissue Module o Skeletal system o Muscle system o Nervous system o Endocrine system o Integumentary system

BIOH111. o Cell Module o Tissue Module o Skeletal system o Muscle system o Nervous system o Endocrine system o Integumentary system 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