ANATOMICAL TERMS Anatomical stance

Transcription

1 ANATOMICAL TERMS Anatmical stance Is a stance in which a persn stand erect with the feet flat n the flr and clse tgether, arms at their sides and the palms and face directed frwards? Bdy Planes Sagittal Plane Passes vertically thugh the bdy r an rgan and it divides it int right and left psitins Midsagittal (median) plane The sagittal plane that divides the bdy r rgan int equal halves Parasagittal Planes Sagittal planes that are parallel t the medium and divide int unequal right and left prtins Frntal (crnal) planes - Extends vertically but is perpendicular t the sagittal plane and divides the bdy int anterir and psterir psitins Hrizntal (crss-sectinal r transverse) planes - Passed acrss the bdy r an rgan perpendicular t its lng axis; it divides the bdy r rgan int superir (upper) and inferir(lwer) prtins Directin Plane Frntal (Crnal) Anterir (ventral) twards the frnt r belly Psterir (drsal) Twards the back r spine Plane (Hrizntal (Transverse) Superir (cranial) Abve

2 Mvements Inferir (caudal) Belw Plane (Sagittal) Medial Twards the median plane Lateral Away frm the medial plane Superficial Clser t the bdy surface Deep further frm the bdy surface Prximal Clser t the pint f attachment f rigin Distal Further frm the pint f attachment f rigin Flexin Mvement that usually decreases a jint angle, usually in the sagittal plane Eg: Bending elbw r knee Extensin Mvement that straightens a jint and generally returns a bdy pint t the zer psitin Eg: Straightening the elbw r knee Hyperextensin further extensin f the jint passed thrugh the zer psitin Eg: Whiplash Abductin the mvement f a bdy part in the frntal plane away frm the midline f the bdy Eg: Mving feet apart t stand spread legged r raising ne arm t ne side f the bdy Adductin mvement in the frntal plane back twards the midline f the bdy Eg: Clsing arms back t the chest Rtatin Mvement in which a bne spins n its lngitudinal axis Prnatin Mvement causing the palm t face psterirly r dwnwards Supinatin Mvement that turns the palm t face anterirly r upwards Circumductin - One end f an appendage remains statinary while the ther end makes a circular mtin Eg: A baseball player thrwing a ball Elevatin Mvement that raises a bdy part vertically in the frntal plane Eg: Raising yur eyebrws Depressin Lwers a bdy part in the same plane Eg: Lwering yur eyebrws Inversin Ft mvement that tips the sles medially, smewhat facing each ther Eversin mvement that tips the sles laterally away frm each ther NERVOUS SYSTEM Overview Central Nervus System cnsists f the brain and the spinal crd, which are enclsed and prtected by the cranium and vertebral clumn Peripheral Nervus System cnsists f all the rest (smatic and mtr), it is cmpsed f nerves and ganglia Nerves a bundle f nerve fibres (axns) wrapped in fibrus cnnective tissue (CT) Ganglia a knt like swelling in a nerve where the cell bdies f neurns are cncentrated

3 Sensry (afferent) divisin carriers signals frm varius receptrs t the CNS Smatic sensry divisin carriers signals frm receptrs in the skin, muscles, bne and jints Visceral sensry divisin carriers signals mainly frm the viscera f the thracic and abdminal cavities Mtr (efferent) divisin carriers signals frm the CNS t gland and muscle cells that carry ut the bdy s respnses Smatic mtr divisin carriers signals t the skeletal muscles Visceral mtr divisin (autnmic nervus system) carriers signals t glands, cardiac muscles and smth muscles Sympathetic divisin tends t aruse bdy fr actin, accelerating the heartbeat Parasympathetic divisin tends t have a calming effect, slwing the heartbeat a) Describe the embrylgical develpment f the nervus system. Embrynic Develpment The nervus systems develps frm the ectderm Within the first 3 weeks the neural plate frms alng the midline f the embry and sinks int the tissue t frm the neural grve, with raised neural flds The neural flds rll twards each ther and fuse By day 26 the neural flds frm the neural tube As the neural tube develps it frms a neural crest Neural crest cells give rise t the peripheral nervus system, including the sensry and autmatic nerves By the furth week the neural tube frms the frebrain, midbrain and hindbrain Neural tube Everything n the drsal side is sensry Everything n the ventral side is mtr Failure f the neural tube t clse results in spina bifida Smites are regular repeating pattern alng the tube Each segment has a spinal nerve The spinal nerve is prtected by vertebrae s

4 Shingles is a viral infectin that affects neurns Embrylgical Develpment Failure Spina Bifida Indicates a failure f the drsal prtins f the vertebrae t fuse with each ther Mre severe frms, invlve failure t clse f mre than ne r tw vertebrae, resulting in the meninges bulging thrugh (meningcele) the pening r the meninges, spinal crd and nerves bulging ut (meningmyelcele) The mre sever frms invlve gradatin f neurlgical symptms which may include paralysis, lss f bladder and anal cntrl and absence f reflexes T prevent this cnditin females shuld have a high level f flic acid, when trying t have a child Anencephaly Results frm failure f the cephalic part f the neural tubes t clse The fre and mid brain d nt develp fully The cranial vault is als absent, resulting in the infant nt surviving past birth Hydrcephaly The circulatin r drainage f CSF is bstructed resulting in a build-up in pressure This result in abnrmal skull in infants, as there skull is nt yet fused, which can lead t pssible retardatin

5 This can be treated befre birth by inserting a shunt which drains the fluid frm the ventricles int a vein in the neck In adults the skull is unable t grw and the brain is cmpressed causing pain, cma and then death if nt treated b) Describe and identify grss anatmical features f the nervus system. Structure f a Neurn The cntrl centre f a neurn is the sma/neursma/cell bdy The sma usually gives rise t the dendrites, lng, thin like branches They are the primary site fr receiving signals frm ther neurns The mre dendrite a neurn has the mre infrmatin it can receive 5 t 135 micr metres in diameter Axn - a cylindrical and relatively unbranched fr mst f its length Specialised fr rapid cnductin f nerve signals t pints remte frm the sma 1 t 20 micr metres lng Neurn Classificatins Multiplar Neurns ne axn and multiple dendrites Biplar Neurns ne axn and ne dendrite Anaxnic Neurns multiple dendrites and n axns Axnal Transprt Axnal transprt the tw-way passage f prteins, rganelles and ther materials alng an axn Antergrade transprt mvement away frm the sma dwn the axn Retrgrade transprt mvement up the axn tward the sma Fast axnal transprt ccurs at a rate f 20 t 400 mm/day and may either be antergrade r retrgrade Fast antergrade transprt mves mitchndria, synaptic vesicles Fast retrgrade transprt returns used synaptic vesicles and ther material t the sma and infrms the sma f the cnditins f the axn terminals Slw axnal transprt an antergrade prcess that wrks in a stp and g fashin, mves at 0.5 t 10 mm/day Mves enzymes and cytskeletal cmpnents dwn the axn Types f Neurglia Neurglia f CNS Oligdendrcytes frm myelin in brain and spinal crd Ependymal cells line cavities f brain and spinal crd Micrglia destrys micrrganisms, freign matter and dead nervus tissue Astrcytes cver brain surface Neurglia f PNS Schwann cells frms a myelin sheath arund nerve in the PNS Satellite cells surrund smas f neurns in the ganglia

6 Myelin Myelin sheath is a spiral layer f insulatin arund a nerve fibre, frmed by ligdendrcytes in the CNS and Schwann cells in the PNS Prductin f the myelin sheath is called myelinatin, begins at the 14 th week f fetal develpment Cnductin speed f Nerve Fibres The speed at which a nerve signal travels alng a nerve fibre depends n tw facts, the diameter f the fibre and the presence r absence f myelin Travel fast in the presence f myelin Lcal Ptentials Stimulatin f neurn causes lcal disturbances in membrane ptential Deplarizatin any such case in which the vltage shifts t a less negative value Lcal Ptential Shrt range change in vltage Characteristics Graded they vary in magnitude (vltage) per the strength f the stimuli An intense r prlnged stimulus pens mre in channels than a weaker stimulus Decremental they get weaker as they spread frm the pint f stimulatin Reversible if stimulatin ceases, catin diffusin ut f the cell quickly returns the membrane vltage t its resting ptential Either excitatry r inhibitry Actin Ptentials Actin ptential a mre dramatic change prduced by vltage-gated in channels in the plasma membrane Characteristics All r nn-law the neurn will nly fire if the threshld has been reached Nn-decremental they d nt get weaker with distance Irreversible if a neurn reaches threshld, the actin ptential ges t cmpletin, it cannt be stpped nce it begins Threshld the minimum needed t pen vltage-gated channels

7 Refractry perid during an actin ptential and fr a few millisecnds after, it is difficult r impssible t stimulate that regin f a neurn t fire again Abslute refractry perid n stimulus f any strength will trigger a new actin ptential Relative refractry perid it is pssible t trigger a new actin ptential, but nly with an unusually strng stimulus Lcal vs Actin Ptential Lcal Ptential Prduced by gated channels f the dendrites and Sma May be psitive (deplarizing) r negative (hyperplarizing) vltage change Graded; prprtin t stimulus strength Reversible Lcal Decremental Actin Ptential Prduced by vltage-gated channels n the trigger zne and axn Always begins with deplarizatin All r nne Irreversible Self-prpagating Nndecremental Spinal Crd Structure A cylinder f nervus tissue that arises frm the brainstem at the framen magnum f the skull 45cm lng and 1.8cm thick During embrylgical develpment, the spinal crd extends fr the full length f the vertebrae, but since the vertebrae grws faster than the spinal crd, the crd nly extends t L3 by the time f birth and t L1 in an adult 31 pairs f spinal nerves The part supplied by each pair f nerves is called a segment Regin f Spinal Crd Number f pairs f nerves Cervical 8 Thracic 12 Lumbar 5 Sacral 5 Cccygeal 1 Spinal crd is divided int cervical, thracic lumbar and sacral regins Thicker in tw areas In the inferir cervical regin, a cervical enlargement gives rise t nerves f the upper limbs In the lumbsacral regin, lumbar enlargement that issues nerves t the pelvic regin and lwer limbs Cauda equine is a bundle f nerve rts Spinal crd is enclsed by three fibrus membranes called meninges, that separate the sft tissue f the central nervus system frm the bnes f the vertebrae and skull Dura mater frms a lse-fitting sleeve called the Dural sheath arund the spinal crd

8 Tugh, cllagenus membrane Epidural space space between the sheath and vertebral bnes, that is ccupied by bld vessels, adipse tissue and lse cnnective tissue Epidural anaesthesia anaesthetics intrduced t this space t blck pain signals during childbirth r surgery Arachnid mater a lse mesh f cllagenus and elastic fibers spanning the gap between the arachnid membrane and the pia mater Simple squamus epithelium Subarachnid space gap between the arachnid membrane and the pia mater that is filled with cerebrspinal fluid Pia mater Delicate, transparent membrane that clsely fllws the cnturs f the spinal crd Crss sectinal anatmy Cnsists f tw kinds f nervus tissue called grey and white matter Grey matter relatively dull clur because it cntains little myelin White matter bright, pearly white appearance due t an abundance f myelin There is mre white matter n sectins f the spinal crd that are clser t the brain since there are mre ascending and descending tracts clser t the brain Axns run thrugh white matter Surrunds the grey matter Spinal tracts Ascending tracts carry sensry infrmatin up the crd Example Gracile fasciculus carries signals frm the mid thracic and lwer parts f the bdy Cuneate fasciculus jins the gracile fasciculus at the T6 level Spinthalamic tract carriers signals fr pain, temperature, pressure, tickle, itch and tuch Spinreticular tract carries pain signals resulting frm tissue injury Psterir and anterir spincerebellar tracts carry prpriceptive signals frm the limbs and trunk t the cerebellum at the rear f the brain Descending tracts cnduct mtr impulses dwn Example Crticspinal tract carry mtr signals Tectspinal tract invlved in reflex turning f the head Lateral and medial reticulspinal tract cntrl muscle f the upper and lwer limbs Lateral and medial vestibulspinal tract cntrl f extensr muscles f the brain Decussatin the tracts crss ver frm the left side f the bdy t the right

9 Neurns Neurns are cells 10^10 neurns As a result the left side f the brain receives sensry infrmatin frm the right side f the bdy and sends mtr cmmands t that side Predminantly the same structure A living cell with a nucleus Neurns cannt divide The Brain Rstral twards the frehead Caudal twards the spinal crd Three majr prtins f the brain (Majr parts f CNS) Cerebrum 83% f brains vlume Grey matter n utside Marked by thick flds called gyri and separated by shallw grves called sulci The lngitudinal fissure separates the right and left prtin The hemispheres are cnnected by a thick bundle f nerve fibers called the crpus callsum