Notebook – Pre-Midterm 2024 PDF

Notebook – Pre-Midterm 2024-08-29 1:31 PM Organization of the Nervous System Central nervous system (Brain + Spinal Cord) Peripheral nervous system...

Notebook – Pre-Midterm 2024-08-29 1:31 PM Organization of the Nervous System Central nervous system (Brain + Spinal Cord) Peripheral nervous system Somatic nervous system – things you are aware of or you can control Autonomic nervous system - sympathetic nervous system – fight or flight - parasympatetic nervous system – rest and digest Enteric nervous system – the "brain" of your gut Functions of the Nervous System 1. Sensory function 2. Integrative function 3. Motor function Classification of Neurons: Functional Sensory Motor Integrative Neuroglia In the CNS Astrocytes – form the blood brain barrier Oligodendrocytes – form myelin Microglia – part of immune system Ependymal Cells – produce CSF In the PNS Schwann cells – myelination Satellite cells – help with regeneration Class 1: Spinal Cord Anatomy What protects the spinal cord? 1. Bony vertebral column + skull 2. Meninges 3. Space w/ cerebrospinal fluid Meninges 3 connective tissue coverings *Epidural space 1. Dura mater – "tough mother" *Subdural space 2. Arachnoid mater – "spider mother" *Subarachnoid space – contains CSF 3. Pia mater – "soft mother" Dura mater Superficial layer Dense irregular connective tissue (thick & strong) Arachnoid mater Middle layer Avascular Delicate collagen fibers and some elastic fibers Continuous with arachnoid mater of the brain Pia mater Innermost layer Thin & transparent Adheres to surface of spinal cord and brain Lots of blood vessels to supply spinal cord Denticulate ligaments: Extension of pia mater that suspend the spinal cord in the middle – connects to the arachnoid mater Protect against sudden displacement Found b/w anterior and posterior neural routes Suspends laterally Spinal cord External Anatomy Shape Oval – flattened anteriorly and posteriorly Length Medulla oblongata to L2 In newborns it goes to L3 or L4 2 Enlargements Cervical enlargement From C4 – T1 Nerves to and from the arms Lumbar enlargement From T9 – T12 Nerves to and from legs Conus medullaris End of the spinal cord Ends b/w L1 and L2 Filum terminale Extension of pia mater that runs from conus medullaris to coccyx Anchors spinal cord to coccyx Cauda equina "horse tail" The spinal nerve roots at the end of the spinal cord don’t exit the vertebral column at the same level that they exit the cord, they fan out like a horse's tail Spinal Nerves Paths of communication b/w spinal cord & specific areas of the body Spinal nerve and nerve that branch off them = PNS They connect CNS to – sensory receptors, mm, glands Mixed nerves (contains sensory + motor axons) C1 – C7 spinal nn exit above their vertebra, and then C8 T1 – L5 spinal nn exit below their vertebra S1 – S4 exit sacral foramina S5 – C01 exit sacral hiatus Rootlets Bundles of axons directly off spinal cord Roots Bundles of axons off rootlets Connect spinal The ant & post roots unite to form spinal nerves Posterior dorsal root sensory axons (sensory receptors to CNS) each has a posterior (dorsal) root ganglion swelling on root cell bodies of sensory neurons Anterior (ventral) root motor axons (CNS to effectors – mm) Spinal Cord Internal Anatomy White matter Bundles of myelinated axons Anterior white columns Posterior white columns Lateral white columns Each column contains distinct bundles of axons with common origin or destination and carry similar info Grey matter Dendrites + cell bodies of neurons Unmyelinated axons Neuroglia Have synapses Posterior Grey Horns Incoming sensory axons Cell bodies + axons of interneurons Anterior Grey Horns Somatic motor cell bodies Lateral Grey Horns Only in thoracic spine and upper lumbar spine Autonomic motor cell bodies Other features Posterior median sulcus – post furrow Grey commissure – cross bar of H Central canal – in center (extends entire length of spinal cord) Anterior median sulcus – wide groove on anterior side Anterior white commissure – connects white matter of left & right sides Tracts Bundles of axons in the CNS Nerves Bundles of axons in the PNS Nuclei Clusters of cell bodies in the CNS Ganglion Clusters of cell bodies in the PNS Spinal Nerve Coverings: Endoneurium Innermost layer Wraps individual axons Perineurium Middle layer Wraps fascicles Epineurium Outer layer Wraps entire nerve Branches of spinal nerves "rami" 1. Posterior (dorsal) ramus Muscle + skin of posterior trunk 2. Anterior (ventral) ramus Muscles + structures of limbs Skin of anterior + lateral trunk 3. Meningeal ramus/branch Re-enters vertebral canal to supply Vertebrae Vertebral ligaments Blood Vessels of Spinal Cord Meninges 4. Rami communicantes Autonomic nervous system Plexuses Formed by axons from anterior rami of spinal nerves (excluding thoracic nerves) Cervical plexus Brachial plexus Lumbar plexus Sacral plexus Intercostal nerves Anterior rami of spinal nerves T2 – T12 (thoracic nerves) T2 intercostals – 2nd intercostal space (b/w T2 – T3) Skin of axilla Posterior/medial arm T3 – T6 intercostals Skin of anterior + lateral chest T7 – T12 intercostals Abd muscles + overlying skin Classification of Nerve Injury: Neurapraxia First degree nerve injury Mild focal compression ( causing a conduction block ) Segmental demyelination **** key feature Reversible in hours to months No break in the fiber Axonotmesis Second degree nerve injury Prolonged, severe compression Wallerian degeneration **** (degeneration of the axon, distal to injury) Endoneurium intact **** key feature Prognosis > 6 months Sensory, motor and autonomic loss Neurotmesis Third degree nerve injury Damaged endoneurium **** key feature Wallerian degeneration Hard to regenerate Surgical intervention to suture Causes of peripheral nerve lesions: Compression Internal: bony callous, hypertoned mm, tumour External: crutches, prolonged leaning Trauma Systemic disorder Leprosy Systemic edematous conditions Pregnancy, DM, hypothyroidism, kidney, heart conditions Class 2: Cervical and Brachial Plexus Cervical Plexus: Neck and Back of the Head: C1 – C4 Superficial (sensory) Branches: Nerve Origin Distribution Lesser occipital C2 Posterior Head --> Posterior to ear (skin) (wrap both your hands around occiput and that is the nerve) Great auricular C2 – C3 Anterior/inferior to ear + Parotid gland (skin) (put your fist to the front of your ear near the parotid gland) Transverse cervical C2 – C3 Anterior neck (skin) (put your hand around the front of your throat) Supraclavicular C3 – C4 Over anterior/superior chest + shoulders (skin) (2 fingers near the clavicle all the way to the shoulders) Deep (mostly motor) Branches: Nerve Origin Distribution Ansa cervicalis superior root C1 Infrahyoids mm Ansa cervicalis inferior root C2 – C3 Infrahyoids mm Phrenic C3 – C5 Diaphram Segmental branches C1 – C5 Prevertebral mm of the neck Ansa = handle Brachial Plexus: Arm, Shoulder, Chest area: C5 – T1 Nerve Origin Distribution Dorsal scapular C5 Levator Scapula + Rhomboid Major and Minor Long thoracic C5 – C7 Serratus Anterior Nerve to subclavius (subclavian n.) C5 – C6 Subclavius mm Suprascapular C5 – C6 Supraspinatus + Infraspinatus Musculocutaneous*** C5 – C7 Coracobrachialis + Biceps + Brachialis (Anterior Arm) Lateral pectoral C5 – C7 Pec Major C5 Dorsal scapular - lev scap, rhomboids maj/min mm Upper subscapular C5 – C6 Subscapularis C5 – C6 Nerve to subclavius – subclavius mm Thoracodorsal C6 – C8 Latissimus Dorsi Suprascapular – supraspinatus + infraspinatus mm Lower subscapular C5 – C6 Subscapularis + Teres Major Upper subscapular – subscapularis mm Axillary*** C5 – C6 Deltoids + Teres minor Lower subscapular – subscapularis + teres major mm Skin over Deltoid + Teres Minor Axillary – deltoid + teres minor mm (+ skin over both) Median*** C5 – T1 Forearm flexors (except FCU) + Thenar group + Lateral Central Compartment C5 – C7 Long thoracic – serratus anterior mm Skin of digit 1 – ½ 4 and palm of hand + posterior distal digits 1 – ½ 4 Musculocutaneous – anterior arm mm Radial*** C5 – T1 Posterior Arm/Forearm mm + Brachioradialis Lateral pectoral – pec major mm Skin of Posterior Arm/Forearm + Posterior hand + Proximal Posterior Digits 1 – ½ 4 C5 – T1 Median forearm flexors (except FCU) + thenar eminence + lateral central compartment mm Medial pectoral C8 – T1 Pec Major + Pec Minor skin over palmar surface of hand, digits 1,2,3, ½ 4, and posterior distal digits 1,2,3, ½ 4 Medial (brachial) cutaneous nerve of arm C8 – T1 Skin of distal medial arm (put a hand on the medial side of your arm where your fingers touch the elbow) Radial posterior arm and forearm mm + brachioradialis mm skin of posterior arm and forearm, dorsum of hand and proximal posterior digits 1,2,3,½ 4 Medial (antibrachial) cutaneous nerve of forearm C8 – T1 Skin of medial forearm Ulnar*** C8 – T1 Flexor Carpi Ulnaris + Hypothenar group + Medial central compartment of the hand + C6 – C8 Thoracodorsal nerve – latissimus dorsi mm Adductor Pollicis Palm + Dorsum and digits ½ 4 and 5 C8 – T1 Medial pectoral – pec major/minor mm Medial brachial cutaneous nerve of the arm – skin of distal medial arm Top 2: axillary Medial antibrachial cutaneous nerve of the arm – skin of medial forearm Bottom 2: ulnar Top 3: musculocutaneous Ulnar nerve And all the nerve roots: median, radial FCU, hypothenar eminence, medial cental compartment, adductor pollicis mm skin of palm and dorsum of hand + digits ½ 4, 5 Compression Syndromes of Peripheral Nerves: Result in a conduction block in the peripheral nerve, but no structural damage to the axon or to the tissue distal to the lesion Symptoms Numbness Tingling Weakness Pain Sensory = numbness, tingling, pain Motor = weakness, pain Pain can be found in a sensory neuron or motor neuron ---> other symptoms will follow to lead if its sensory or motor If the nerve is not fully compressed it will show different symptoms than the regular pattern Venous system unrelated w/ TOS Symptoms due to: Impaired oxygenation (ischemia) of nerve Impaired local neural conduction Classification of Neuropathy: Mononeuropathy When a single peripheral nerve is affected Polyneuropathy When several peripheral nerves are involved Radiculoneuropathy Involvement of the nerve root as it emerges from the spinal cord (nerve root problem) Polyradiculitis Involvement of several nerve roots and occurs when infections create an inflammatory response Brachial Plexus Injuries: Erb-Duchenne Palsy Injury to the superior roots of the brachial plexus: C5-C6 Traction injury (pull injury) Forceful pulling away of head from shoulder No sensation over lateral arm (sensory loss C5 & C6 dermatomes) Waiter's tip position: Arm is adducted Med rotation Elbow extended Forearm pronated Wrist and fingers flexed Dermatome pattern over C5 – C6 Causes: Child birth – doctor pulls head and can traction the head away from the shoulder Trauma – MVA Klumpke's paralysis Traction injury of lower brachial plexus: C8 – T1 Due to: Poor positioning at birth (breech) or pulled by forceps Falling from height & grabbing something to break a fall Arm pulled up beside the head Results in: Median and ulnar lesions Claw hand Sensory loss affecting C8 & T1 dermatomes Can get Horner's syndrome – can be acquired Horner's syndrome On affected side – 4 symptoms: Miosis – constriction of pupil Ptosis – drooping of eyelid Anhydrosis – loss of sweating to face and neck Enophthalmos – recession of eyeball into orbit *** animals can get this syndrome – like dogs – huskies (heterochromia) *** Thoracic Outlet Syndrome: Pathway Compression of brachial plexus (C5-T1) from structures in the thoracic outlet Thoracic outlet runs from interscalene triangle to inferior border of axilla (from neck – axilla) Subclavian artery and vein may also be compressed 1. The brachial plexus travels w/ the subclavian artery b/w the anterior and middle scalene – minus subclavian v. 2. The subclavian vein joins in after the scalenes and the whole neurovascular bundle goes below the clavicle and under the pec minor insertion and down the arm – subclavian vein included Causes Internal compression (bony callus, cervical rib) External compression Prolonged poor positioning Poor posture (hyperkyphosis, scoliosis, mm HT, TrP's) Systemic immune or metabolic disorders (RA, DM, hypothyroidism) Trauma (whiplash) Joint subluxation of c-spine Pregnancy Symptoms Pain, numbness, weakness, tingling in arm or across upper thoracic area over scapula Trophic changes (skin changes due to lack of blood flow – red shiny skin, lack of hair, swelling) in tissue w/ blood vessel compression Locations: Anterior Scalene Syndrome Compression b/w anterior and middle scalene Interscalene triangle anterior scalene middle scalene rib 1 brachial plexus and subclavian artery pass through only (subclavian v. is ant) Costoclavicular Syndrome Compression between the clavicle and rib 1 Pectoralis Minor Syndrome Compression between coracoid process and pec minor Presence of Cervical Rib Additional rib at C7 Radial Nerve Lesions: C5 – T1 Pathway From posterior axillary wall b/w long and medial heads of triceps Spiral groove of humerus Winds to lateral humerus to anterior humerus (lateral epicondyle) b/w brachialis + brachioradialis To supinator Branches just before supinator: Posterior motor branch - posterior interosseous nerve - enters supinator + travels down lateral radius to wrist - only goes to the wrist – because we don’t have muscles in the hand just tendons which don’t need to be innervated Superficial branch - travels down posterior forearm to hand - goes above supinator Causes Fractures – at spiral / radial groove Dislocations – of head of radius, humeroradial or radioulnar joints Post surgical complications Compression Symptoms Numbness, tingling, weakness, pain Altered sensation at posterior arm and hand (digit 1, 2, 3, and lateral ½ of 4) Wrist drop – cant extend wrist and fingers If injury is proximal to elbow, both sensory & motor affected (before the split of the radial nerve) If injury is distal to elbow, only sensory OR motor is affected Location: Crutch Palsy At axilla Entire posterior arm and hand would have symptoms Saturday Night Palsy Compression at spiral groove of humerus From direct pressure against a firm object Deep sleep on arm – passed out on hard surface Entire posterior arm and hand would have symptoms – just not the upper/axilla portion of the arm Posterior Interosseous Syndrome Posterior interosseous nerve comes off in front of the lateral epicondyle of the humerus Motor nerve Gets wrist drop Compression from the Supinator – underneath the supinator Cheiralgia paresthetica Compression of the superficial branch of the radial nerve as it passes under the tendon of brachioradialis (by the wrist) Sensory Pain at dorsum of wrist, thumb, webspace Cause – trauma, tight cast, swelling Eg. When you are carrying groceries and the grocery bag falls down to your wrist Median Nerve Lesions: C5 – T1 Pathway Medial humerus Underneath biceps a little, that’s where the median nerve is Pass anterior to medial epicondyle near the cubital fossa Goes underneath pronator teres - deep branch: deep motor nerve (anterior interosseous syndrome) - superficial branch: carpal tunnel Goes down the wrist, through carpal tunnel to structures in the hand Etiology Fracture at elbow, wrist and carpals Dislocation at elbow, wrist, carpals Compressions Trauma Symptoms Ape hand Thumb in same plane as rest of hand since there is no opposition (wasting of thenar eminence) Oath hand You see when you go to make a fist only digit 4 & 5 can be flexed – b/c of median nerve damage Cant grasp objects Cant pronate forearm, flex PIP's, flex DIP's of digit #2, #3 (cant do air quotes) Weak wrist flexion, weak thumb movements Altered sensation on digit 1, 2, 3, and ½ of 4 (palmar surface) Ape and Oath hand Locations: Carpal Tunnel Syndrome Compression through the carpal tunnel at wrist Most common entrapment condition in arm Carpal tunnel: carpal bones form the floor of the tunnel flexor retinaculum forms the roof flexor retinaculum attaches to scaphoid tubercle & trapezium structures that pass through carpal tunnel - median nerve - flexor digitorum superficialis (4 tendons) - flexor digitorum profundus (4 tendons) - flexor pollicis longus (1 tendon) Symptoms: Numbness & tingling in digit 1, 2, 3, and ½ of 4 (palmar surface) Distinguishing feature – presence of nocturnal symptoms that wake person up, excrusiating pain Muscle weakness and clumsiness of thumb and fingers Later get thenar muscle wasting Compression of the median nerve in the carpal tunnel occurs in 2 ways: 1. Size of the tunnel decreases - bony callous, space occupying lesion, bony changes, fracture/dislocation (lunate goes anteriorly) eg. RA 2. Size of contents passing through increases - repetitive actions --> edema and then fibrosis + tendon thickening - retinaculum thickening from scar tissue (repeated trauma) - systemic conditions that cause edema + fluid retention Pronator Teres Syndrome Compressed at proximal attachment of pronator teres Aching in anterior forearm Numbness in thumb and index finger Some weakness in thenar muscle Second most common Anterior Interosseous Syndrome Branch of median nerve – deep branch; Can be pinched or entrapped as it passes b/w the heads of pronator teres Mostly affects the deep muscles of the forearm Pain and motor loss of flexor pollicis longus, lateral ½ FDP, and pronator quadratus – purely motor Paralysis of flexors in index finger & thumb Ligament of Struthers Tiny ligament that runs from an abnormal spur on the shaft of the humerus to the medial epicondyle Median nerve can be compressed above the elbow as it passes under Only in 1% of the population Ulnar Nerve Lesions: C8 – T1 Pathway Comes from underneath coracoid Directly medial humerus Posterior to medial epicondyle Ulnar groove Under FCU Over the flexor retinaculum Between the pisiform and hook of the hamate (guyon's canal) Etiology Fractures at medial epicondyle, midforearm, wrist Dislocations of elbow Post-surgical complications (badly positioned arm while under anesthetic) Compression resting elbow on hard surface wearing tight wrist band cycling Repetitive actions Direct trauma Symptoms Muscle wasting of hypothenar Altered sensation in little finger + medial ½ of right finger (palmar and dorsal) Froment's sign is positive Ulnar claw hand Ulnar claw hand Baby finger is hyperextended and abducted at MCP and flexed at IP Ring finger is hyperextended at MCP and flexed at IP Atrophy of interosseous muscle Froment's sign Hold paper b/w thumb + index finger You need adductor pollicis to hold the paper like the clinician (which is innervated by the ulnar nerve) So patients flex thumb to use flexor pollicis longus – rather than using adductor pollicis Locations: Tardy Ulnar Palsy Ulnar nerve palsy is a common complication of fractures to the elbow It is a late (tardy) palsy that can occur years after a fracture It is associated with a callus formation or a valgus deformity of the elbow It produces a gradual stretching of the nerve in the ulnar groove of the medial epicondyle Handle Bar Palsy Compresses the nerve at the tunnel of guyon As you cycle if you rest your hands on the bar it can physically press the nerve Class 3: Lumbar and Sacral Plexus Lumbar Plexus: L1 – L4 Nerve Origin Distribution Iliohypogastric L1 Anterior/lateral abs inferior abs ---> lateral glutes Ilioinguinal L1 Anterior/lateral abs Anterior/superior/medial thigh (over inguinal ligament) Genitals Genitofemoral L1 – L2 Cremaster mm Anterior/superior/middle thigh Genitals Lateral cutaneous nerve of thigh (lateral L2 – L3 Lateral thigh (goes slightly posteriorly and anteriorly) femoral cutaneous) Femoral L2 – L4 Quads, Sartorius (anterior thigh muscles) *** largest & thickest *** Anterior/medial thigh Medial leg and foot Obturator L2 – L4 Adductors Medial thigh Injury to Femoral Nerve Can occur in stab or gunshot wounds Cant extend leg (at knee) Trouble flexing hip Wasting of quads No sensation over ant/medial thigh Injury to Obturator Nerve Paralysis of adductor muscles No sensation over medial thigh Can occur from pressure on nerve by fetal head during pregnancy Meralgia Paresthetica Lateral femoral cutaneous nerve entrapment Occurs near the ASIS as the nerve passes under the inguinal ligament L1 1. Iliohypogastric nerve Sensory nerve – sensory alteration and/or burning pain on the lateral thigh anterior/lateral abs mm skin of inferior abs to lateral glutes Cause: Heavier people who sit a lot 2. Ilioinguinal nerve Trauma (seat belt in car accident) anterior/lateral abs mm During delivery (in stirrups) skin of ant/sup/med thigh (over inguinal ligament) & genitals Tight clothing Complication of surgery (hernia) L1 – L2 Genitofemoral nerve cremaster mm skin of ant/sup/middle thigh & genitals Sacral Plexus: L4 – S4 L2 – L3 Lateral cutaneous nerve of thigh – skin of lateral thigh (post/ant sl) Nerve Origin Distribution Superior gluteal * L4 – S1 Glute med/min, TFL L2 – L4 1. Femoral nerve anterior thigh mm (quads, sartorius) skin of ant/medial thigh + medial leg & foot Inferior gluteal * L5 – S2 Glute max 2. Oburator nerve Nerve to piriformis * S1 – S2 Piriformis adductors mm skin of medial thigh Nerve to quadrator femoris + inferior gemellus * L4 – S1 Quadratus femoris + inferior gemellus Nerve to obturator internus + superior gemellus* L5 – S2 Obturator internus + superior gemellus Perforating cutaneous * S2 – S3 Inferior/medial buttock (right overtop ischial tuberosity) Posterior cutaneous nerve of thigh * S1 – S3 Inferior/lateral buttock, posterior thigh, genitals, superior calf Sciatic * L4 – S3 Hamstrings + adductor magnus Largest n in the body Longest n in the body Longest neurons Tibial + common fibular nerve bound together & split at knee Tibial * L4 – S3 Posterior leg muscles + popliteus Medial plantar * Abductor hallucis, flexor digitorum brevis, flexor hallucis brevis Medial plantar foot Lateral plantar * Other foot muscles Lateral plantar foot Common fibular * L4 – S2 Divides into superficial + deep fibular branch Superficial fibular * Lateral compartment of the leg muscles Lateral compartment, dorsum of the foot Deep fibular * Anterior compartment of the leg muscles, fib tertius, extensor hallucis brevis, extensor digitorum brevis Dorsum of digits 1 & 2 Pudendal S2 – S4 Pelvic floor Genitals L4 – S1 1. Superior gluteal nerve Sciatic Nerve Lesions: glute med/min + TFL mm Causes Fractures pelvis, femur, tibia, fib head, ankle 2. Nerve to quadratus femoris + inferior gemellus quadratus femoris + inferior gemellus mm Dislocation Hip, knee, ankle L4 – S2 Common fibular nerve : branches to superficial and deep Iatrogenic reasons Superficial fibular nerve Glute injury, hip surgery, meniscal repair, improper positioning during surgery lateral compartment of leg mm skin of lateral compartment & dorsum of foot Compression from internal sources Herniations – 1st most common Piriformis (piriformis syndrome) - 2nd most common Deep fibular nerve Flexor retinaculum (tarsal tunnel syndrome) anterior compartment of leg mm, fib tertius, extensor hallucis brevis, extensor digitorum brevis Ganglion skin of dorsum of digits 1 & 2 Morton's foot L4 – S3 1. Sciatic nerve – hamstrings + adductor magnus Compression from external sources Against fib head (cast, splint) Crossing legs 2. Tibial nerve – posterior leg mm + popliteus mm Trauma Medial plantar nerve Herniations is the most common cause of sciatic nerve problems - abd hallucis, flexor digitorum brevis, flexor hallucis brevis mm - skin of medial plantar foot Symptoms Pain at butt and down lateral leg and possibly to lateral foot Lateral plantar nerve Foot drop - other foot mm Paralysis of dorsiflexors and everters - skin of lateral plantar foot Leads to steppage gait – big large steps so their toes don’t drag L5 – S2 1. Inferior gluteal nerve glute max mm Tarsal Tunnel Syndrome: 2. Nerve to obturator internus + superior gemellus The tibial nerve can be compressed at the ankle as it passes through the tarsal tunnel obturator internus + superior gemellus mm The tarsal tunnel is formed by.. The medial malleolus S1 – S2 Nerve to piriformis Calcaneous piriformis mm Talus (on the floor of the tunnel) Flexor retinaculum (on the roof) S1 – S3 Posterior cutaneous nerve of thigh Causes: skin of inf/lat buttocks, posterior thigh, genitals, superior calf Swelling after trauma Space-occupying lesion (eg. Ganglion) S2 – S3 Perforating cutaneous Inflammation (eg. Paratendonitis) skin of inf/med buttocks (right overtop ish tube) Valgus deformity – runner who has flat feet S2 – S4 Pudendal Chronic inversion pelvic floor mm + genitals Symptoms Pain and paresthesias into sole of foot Symptoms often worse after long periods of standing or walking or at night Pain localized or radiated over medial ankle, distal to medial malleolus Has been misdiagnosed as plantar fasciitis Class 4: Dermatomes Neuritis Inflammation of the nerve Mainly the sheath and connective tissue are affected (usually the axon is not) Constant dull pain Can also get numbness and tingling Causes: Secondary to a pathology (DM, leprosy, TB) Trauma to nerve Chronic exposure to a toxin like lead, drugs or alcohol Neuralgia Nerve pain Recurrent attacks of sudden excruciating pain along distribution of the nerve Has a trigger zone Trigger zone: Area that causes an attack when stimulated Usually it's an area of skin supplied by the nerve Movement of the area increases pain Commonly affected are trigeminal and intercostal nerves (T-spine) Intercostal Neuralgia Affects intercostal nerves that travel between the internal and innermost intercostal muscles Causes: Diabetes Herpes Zoster/Post-herpes zoster Herpes Zoster/Post-Herpetic Neuralgia Starts w/ chicken pox Varicella zoster virus is the virus that causes chicken pox in children – varicella zoster is the virus for shingles too After recover from chicken pox in childhood, the virus is not eliminated from the body but lies dormant within the sensory ganglia of cranial or spinal nerves (dorsal root ganglion) and can become activated later in life to cause herpes zoster (shingles) Years later, when the immune system is depressed, the virus reactivates Usually only 1 nerve affected When reactivated, the virus causes a generalized inflammatory response starting in the sensory ganglion and spreading along the nerves causing demyelination and degeneration Inflammation produces pain and tingling in the involved dermatome w/ a rash and then vesicles that burst and encrust Skin lesions can last up to a month and disappear as the effects of the virus resolve Thoracic and trigeminal nerves are the most common Intermittent attacks of deep, burning, sharp shooting pain along the affected nerve Trigger is often light touch and movement over affected area Class 5 – Spinal Cord Physiology Spinal Cord Physiology: 2 main functions of the spinal cord 1. Propagates nerve impulses 2. Integrates information Sensory and Motor Tracts: White Matter 2 main sensory tracts 1. Spinothalamic tract Conveys nerve impulses for sensing Pain Temperature Itch Tickle PTIT 2. Posterior column Made up of 2 tracts: gracile fasciculus & cuneate fasciculus Conveys nerve impulses for Touch light pressure Vibration Conscious proprioception Conscious proprioception The awareness of the positions and movements of muscles, tendons, and joints 2 main motor tracts 1. Direct pathways From your brain ---> muscles Nerve impulses originate in cerebral cortex Cause voluntary movements of skeletal muscle 2. Indirect pathways Nerve impulses originate in brain stem Causes automatic movements (involuntary) – skeletal muscle Helps coordinate body movements with visual stimuli Maintains skeletal muscle tone Sustained contraction of postural muscles Major role in equilibrium by regulating muscle tone in response to movements of head Reflexes and Motor Arcs: Grey Matter Stimulus A change in the internal or external environment Reflex A fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus Can be inborn or learned Spinal reflex When integration happens in grey matter of spinal cord Cranial reflex When integration happens in brain stem Somatic reflex Involves contraction of skeletal muscle Autonomic reflexes Not usually consciously perceived Involve responses of smooth mm, cardiac mm, and glands Reflex Arc The reflex arc or reflex circuit is the pathway for nerve impulses that produce a reflex It is made up of 5 things: 1. Sensory receptor 2. Sensory neuron 3. Integrating center 4. Motor neuron 5. Effector Made up of 5 things: 1. Sensory receptor Responds to a stimulus by producing a generator or receptor potential 2. Sensory neuron Axon conducts impulses from receptor to integrating center 3. Integrating center Monosynaptic reflex arc most simple a reflex pathway w/ only 1 synapse in the CNS (so 2 neurons and 1 synapse) Polysynaptic reflex arc when the integrating center consists of at least one interneuron involves more than 1 synapse in the CNS (so 3 neurons and 2 synapses) 4. Motor neuron Axon conducts impulses from integrating center to effector 5. Effector Muscle or gland that responds to motor nerve impulses 1. The Stretch Reflex 2. The Tendon Reflex 3. The Flexor (withdrawl) Reflex 4. The Crossed Extensor Reflex Effector Reflexes: The Stretch Reflex Contraction of a skeletal muscle in response to stretching of that muscle Monosynaptic reflex arc Can be elicited by tapping on tendons attached to muscles at elbow, wrist, knee and ankle joints Stimulates muscle spindles – in the muscle belly Muscle spindles are sensory receptors in the mm They monitor the change in length of the mm Stretch reflex is an ipsilateral reflex arc Sensory nerve impulses enter the same side that the motor nerve impulses come out Tone of a muscle is also set through muscle spindles Muscle tone – the small degree of contraction present when a muscle is at rest Small motor neurons innervate specialized fibers within the muscle spindle – this is how the brain regulates tone By adjusting how much a muscle spindle responds to stretching, the brain sets an overall level of muscle tone Reciprocal innervation When parts of a neural circuit simultaneously cause contraction of 1 muscle and relaxation of its antagonists Branches of the muscle spindle sensory neuron also relays information to the brain so that you know what is happening Helps avoid injury by preventing overstretching of the muscle The Tendon Reflex Relaxation of a muscle when there is too much tension Prevents tearing of a tendon Ipsilateral reflex arc Polysynaptic Stimulates Golgi tendon organs (GTO) Sensory receptor found within tendon near its junction with a mm monitors changes in mm tension (musculotendinous junction) This reflex protects the tenson and muscle from damage due to excessive tension Reciprocal innervation: When parts of a neural circuit simultaneously cause contraction of 1 muscle and relaxation of its antagonists The Flexor (withdrawl) Reflex When you step on a tack, you will flex or withdraw your leg away from the painful stimulus Polysynaptic reflex arc Ipsilateral reflex arc This is a protective reflex because it moves the limb away from a possibly damaging stimulus It is an intersegmental reflex arc Nerve impulses from 1 sensory neuron ascend and descend in the spinal cord, activating interneurons in several segments of the spinal cord This way a single sensory neuron can activate several motor neurons Reciprocal innervation When parts of a neural circuit simultaneously cause contraction of 1 muscle and relaxation of its antagonists The Crossed Extensor Reflex Happens with the flexor reflex; when you step on a tack and withdraw or flex your leg, the other leg needs to extend so you dont fall over Contralateral reflex arc Sensory impulses enter one side of the spinal cord and motor impulses exit on the opposite side Intersegmental reflex arc Reciprocal innervation Class 6: Development of the Brain Major Parts of the Brain: Brain Stem Continuous with spinal cord Medulla oblongata Pons Midbrain Cerebellum Posterior to brain stem Diencephalon Superior to brain stem Thalamus Hypothalamus Epithalamus Cerebrum Largest part of the brain Sits on diencephalon Protective Coverings of the Brain: Cranium and cranial meninges surround and protect the brain Cranial meninges are continuous with the spinal meninges ***No epidural space around the brain*** 1. Dura Mater Outer meningeal layer Made up of 2 layers: Periosteal layer – external Meningeal layer – internal These two layers are fused together except where they separate to enclose the dural venous sinuses Dural venous sinuses Endothelial-lined venous channels Drain blood from the brain and deliver it into internal jugular veins 3 extensions of dura mater separate parts of the brain: 1. Falx cerebri: separates the 2 hemispheres of the cerebrum 2. Falx cerebelli: separates the 2 hemispheres of cerebellum 3. Tentorium cerebelli: separates the cerebrum from the cerebellum Subdural space *** same as spinal cord *** 2. Arachnoid mater Middle layer ***same as spinal cord*** Avascular Delicate collagen fibers and some elastic fibers Continuous with arachnoid mater of the brain Subarachnoid space *** same as spinal cord *** contains CSF 3. Pia mater Innermost layer ***same as spinal cord*** Thin & transparent Adheres to surface of spinal cord and brain Lots of blood vessels to supply brain Denticulate ligaments: Extension of pia mater that suspend the spinal cord in the middle – connects to the arachnoid mater Protect against sudden displacement Found b/w anterior and posterior neural routes Suspends laterally Brain Blood Flow: Blood flows to brain mainly via Internal carotid Vertebral arteries Blood flows out of brain via The dural venous sinuses which drain into the internal jugular vein In adults, brain is 2% of total body weight but consumes 20% of all the oxygen and glucose Neurons use glucose and oxygen to make ATP in the brain No glucose is stored in the brain so the supply of glucose must be continuous If blood entering the brain has a low level of glucose: Mental confusion Dizziness Convulsions Loss of consciousness Even a brief slowing of brain blood flow causes disorientation or a lack of consciousness Interruption in blood flow for 1 – 2 minutes impairs neuronal function Total deprivation of oxygen for about 4 minutes may cause permanent injury Blood Brain Barrier: Made up of: 1. Tight junctions seal together endothelial cells of capillaries in the brain 2. Thick basement layer surrounds the capillaries (extra protection) 3. Astrocytes their processes press up against the capillaries and secrete chemicals that maintain the permeability characteristics of tight junctions (wrap around capillaries for extra protection) What crosses it? Water-soluble substances cross by active transport glucose Creatinine, urea, ions cross slowly Lipid-soluble substances O2, carbon dioxide, alcohol, most anesthetic agents Proteins and most antibiotic drugs – do NOT cross Trauma, certain toxins and inflammation can cause a breakdown of the blood brain barrier Cerebrospinal Fluid: Protects the brain and spinal cord from chemical and physical injuries Clear colourless liquid Mainly water Also carries a small amount of O2, glucose and other chemicals in blood to the neurons and neuroglia CSF is constantly moving CSF continuously circulates through The cavities in the brain + spinal cord Around the brain Spinal cord in the subarachnoid space Total volume = 80 – 150 mL in adults (½ a cup) Contains: Small amounts of glucose, proteins, lactic acid, urea, cations, anions and some WBCs Functions 1. Mechanical Protection Shock absorbing medium that protects brain + spinal cord from jolts Fluid also keeps brain floating in the cranial cavity 2. Homeostatic Function The pH of CSF affects pulmonary ventilation & cerebral blood flow 3. Circulation Minor exchange on nutrients + waste products btw blood and nervous tissue Ventricles Cavities within the brain filled with CSF Two Lateral Ventricles 1 in each hemisphere of the cerebrum Septum pellucidum – thin membrane that separates the lateral ventricles Third Ventricle Fourth Ventricle Formulation of CSF in Ventricles: CSF is formed in choroid plexus Choroid plexuses – network of blood capillaries in the walls of the ventricles Steps: 1. Ependymal cells joined by tight junctions cover the capillaries 2. Substances from blood plasma (mostly water) are filtered from the capillaries through the ependymal cells to produce CSF 3. Because of the tight junctions b/w ependymal cells, fluid must pass though the ependymal cells, creating a blood-cerebrospinal fluid barrier This protects the brain + spinal cord from harmful blood-borne substances Blood brain barrier is made up of Tight junctions b/w brain capillary endothelial cells The blood-cerebrospinal barrier is made up of Tight junctions b/w ependymal cells Circulation of CSF Lateral ventricles ---> third ventricle ---> fourth ventricle ---> central canal, subarachnoid space ---> arachnoid villi Arachnoid Villi Arachnoid villi are finger-like extensions of arachnoid that project into dural venous sinuses CSF is reabsorbed into blood through arachnoid villi Granulation A cluster of arachnoid villi Class 7: The Brain Stem The Brain Stem: 1. Medulla Oblongata 2. Pons 3. Midbrain Medulla Oblongata: Starts at the foramen magnum and goes to pons Made up of sensory (ascending) tracts and motor (descending) tracts Pyramids – bulges of white matter on the anterior part of the medulla Formed by the corticospinal tract Purely motor Decussation of pyramids – crossing of axons in pyramids 90% of axons cross here Explains why each side of brain controls the opposite side of body Medulla Nuclei's Many of these nuclei control vital body functions Swallowing, breathing, vomiting, blood pressure control, rate/evenness of heart rhythm 1. Cardiovascular center 2. Medullary rhythmicity area of the respiratory center 3. Vomiting center 4. Deglutition center 5. Olive 6. Gracile nucleus & cuneate nucleus 7. Gustatory nucleus 8. Cochlear nucleus 9. Vestibular nucleus No BLINKING OR SNEEZING 1. Cardiovascular center Regulates the rate and force of the heartbeat & the diameter of blood vessels 2. Medullary rhythmicity area Adjusts the basic rhythm of breathing (along with areas in the pons) 3. Vomiting Center Causes vomiting 4. Deglutition center Causes swallowing 5. Olive Just lateral to each pyramid Oval – shaped swelling Inferior olivary nucleus Within the olive Receives input from – cerebral cortex, red nucleus (midbrain), spinal cord Its neurons extend into cerebellum. Where they regulate the activity of cerebellar neurons It provides instructions that the cerebellum uses to make adjustments to muscle activity as you learn new motor skills 6. Gracile nucleus & cuneate nucleus Are associated with sensation of Touch Pressure Vibration Conscious proprioceprion 7. Gustatory nucleus From tongue to brain Receives gustatory input from taste buds of tongue 8. Cochlear nucleus Part of the auditory pathways from inner ear to brain