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Fight or flee artifact Fight or flee artifact Document Transcript

  • Inside:  CNS and its parts  PNS and its parts
  • Three MeningesThe meninges is the system of membranes which envelops the central nervous system. In mammals, themeninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primaryfunction of the meninges and of the cerebrospinal fluid is to protect the central nervous system. © 15Dura materThe dura mater [Latin: tough mother] (also rarely called meninx fibrosa or pachymeninx) is a thick,durable membrane, closest to the skull. It consists of two layers, the periosteal layer which lies closest tothe calvaria (skull), and the inner meningeal layer which lies closer to the brain. It contains larger bloodvessels which split into the capillaries in the pia mater. It is composed of dense fibrous tissue, and itsinner surface is covered by flattened cells like those present on the surfaces of the pia mater andarachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve severalfunctions. The dura mater surrounds and supports the large venous channels (dural sinuses) carryingblood from the brain toward the heart.The dura has four areas of infolding which include :Falx cerebri, the largest, sickle-shaped; separates the cerebral hemispheres. Starts from the frontal crestof frontal bone and the crista galli running to the internal occipital protuberance.Tentorium cerebelli, the second largest, crescent-shaped; separates the occipital lobes from cerebellum.The falx cerebri attaches to it giving a tentlike appearance.Falx cerebelli, vertical infolding; lies inferior to the tentorium cerebelli, separating the cerebellarhemispheres.Diaphragma sellae, smallest infolding; covers the pituitary gland and sella turcica.[edit]Arachnoid materThe middle element of the meninges is the arachnoid mater, so named because of its spider web-likeappearance. It provides a cushioning effect for the central nervous system. The arachnoid mater is athin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flatcells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of thesurface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large
  • number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoidspace to blend with the tissue of the pia mater.The arachnoid and pia mater are sometimes together called the leptomeninges.Pia materThe pia mater [Latin: soft mother] is a very delicate membrane. It is the meningeal envelope whichfirmly adheres to the surface of the brain and spinal cord, following the brains minor contours (gyri andsulci). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet offlat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel tothe brain and spinal cord, and its capillaries are responsible for nourishing the brain.SpacesThe subarachnoid space is the space which normally exists between the arachnoid and the pia mater,which is filled with cerebrospinal fluid.Normally, the dura mater is attached to the skull, or to the bones of the vertebral canal in the spinalcord. The arachnoid is attached to the dura mater, while the pia mater is attached to the central nervoussystem tissue. When the dura mater and the arachnoid separate through injury or illness, the spacebetween them is the subdural space.meninges /me·nin·ges/ (mĕn-in´jēz) sing. meninx [Gr.] the three membranes covering the brain andspinal cord: dura mater, arachnoid, and pia mater.menin´geal ©16Spinal cordThe spinal cord in the simplest part of the central nervous system and is connected to the brain by thedelicate brain stem and contained within the spinal cavity. It is an oval shaped cylinder that tapersslightly as it descends with two bulges as labeled in the diagram. The spinal cord mediates simplereflexes and is extremely delicate and important. It provides conduction paths to and from the braincalled ascending tracts and descending tracts. The sensory impulses go up towards the brain and the
  • motor impulses come back down. It also is the reflex center for all spinal reflexes. IT switches impulsesfrom afferent to efferent neurons. ©8Nerve rootsThere are 31 spinal nerves connected to the spinal cord, numbered by the level they emerge from thespinal cavity. These attach by 2 types of short roots, a ventral nerve root or a dorsal nerve root. Vertral isanterior and dorsal is posterior. The dorsal is easily recognized by the spinal ganglion. The ventral rootscarry motor neurons to effectors, also known as muscles and glands. The dorsal root carry informationfrom receptors in the peripheral nerves. ©8
  • ©12Function of the Brainstem: It performs sensory, motor, and reflex functions. Thespinothalamic tracts that pass through the brain stem are on the way to the thalamus.Nuclei in the medulla have reflex centers like cardiac, vasomotor, and respiratory. Othercenters in the medulla are responsible for nonvital refluxes such as vomiting. The ponscontains centers for reflexes mediated by the 5th, 6th, 7th, and 8th cranial nerves. Finally,the midbrain also contains reflex centers for certain cranial nerves such as eyemovements mediated by the 4th cranial nerve.
  • Functions and Structure of the Cerebellum ©13Function: The cerebellum performs three general functions. It acts with the cerebralcortex to produce movements by coordinating the groups of muscles. It helps controlposture by functioning below the level of consciousness to ensure smooth and steadymovements. It also controls skeletal muscles to maintain balance.
  • Structure and Function of the Diencephalon ©14Function: The functions of the thalamus are the part it plays in themechanism responsible for sensations. Impulses from receptors uponreaching the thalamus produce conscious recognition of the sensations. Itplays a part in the mechanism responsible for emotions by associatingsensory impulses with feelings. It plays a part in the alerting mechanism,and the mechanism that produces complex reflex movements. Thefunctions of the hypothalamus are that it functions as a high autonomiccenter and as a relay station between the cortex and the lower autonomiccenters. It synthesizes hormones, performs endocrine functions, essentialrole in maintaining the waking state, appetite mechanism, and part of themechanism responsible for maintain body temperature.
  • Cerebral Cortex Structure and Function ©14Functions: Functions of the cerebral cortex include: sensory functions being somatic or“general senses”, motor functions such as movement of individual muscles, andintegrative functions such as consciousness, language, emotions, and memory. All theparts of the cerebral cortex work together and individually to help with the mechanismsthat control many parts of the body.
  • The somatic nervous pathway is made up of nerves that connect to the skin, sensory organs and allskeletal muscles. The system is responsible for nearly all voluntary muscle movements as well as forprocessing sensory information that arrives through external stimuli, which are things like hearing, touchand sight.The somatic motor pathways include smooth muscle, cardiac muscle, and glands. The two divisionswould be sympathetic division and parasympathetic division. Parietal lobe Frontal lobe Occipital lobe Thalamus Cerebellum
  • Cerebrum ain Cervical Cerebellum Enlargement SpinalNerve CordRoot ain ain Membranous covering (meninges) Lumbar Enlargement Filum terminale
  • The Cerebral Cortex is described the “gray” matter that covers the entire brain. The cerebral has a very important function of responsible for sensing and interpreting input from various sources and maintaining cognitive function. Sensory functions interpreted by the cerebral cortex include hearing, touch, and vision. Cognitive functions include thinking, perceiving, and understanding language. For additional information on the cerebral cortex visit the Cerebral Cortex and Cerebral Cortex Lobes pages. ©11 Somatic Sensory and Motor PathwaysSomatic Sensory pathways send impulses to the cerebralcortex for it to perform its sensory functions. Most impulsessent to the cerebral cortex end up going through three levelsthrough three pools of sensory neurons primary, secondary,and tertiary. Primary sensory neurons conduct from theperiphery to the central nervous system. Secondary sensoryneurons conduct from the cord or brainstem up to thethalamus. Tertiary neurons conduct from the thalamus to thepostcentral gyrus which extend through the portion known asthe internal capsule to the cerebral cortex. Somatic Motorpathways are there for the cerebral cortex to perform itsmotor functions. Impulses are from the motor areas and aresent to the skeletal muscles .
  • Brain Pg. 414 & 417 Sensory to back of head, front of neck, and upper part ofCervical plexus found deep shoulder; motor to numerous Cervical Plexus neck muscleswithin the neck. BrachialPlexus found deep within theshoulder. Lumbar Plexus;network of nerves located in ©11the Lumbar region of the backnear the psoas muscle. Fibersfrom the fourth and fifthlumbar nerves and the firstfour sacral nerves form theSacral Plexus. (LUMBOSACRALPLEXUS) when together. Last Sensory to anterior abdominal wall,sacral nerve, along with a few Lumbar Plexus external genitalia; sensory to outer partfibers from S4 joins with the of thigh.coccygeal nerve to form asmall coccygeal plexus. Nervesinnervate the floor of the Sacral Plexus Motor to quadriceps, Sartorius, andpelvic cavity. Iliacus muscles. Motor to adductor muscles of the thigh and medial side of lower leg. Motor to calf and leg Coccygeal Plexus muscles (skin of calf and foot). Sensory to lateral surface on leg, and dorsal surface on foot. Motor to muscles on the back of the thigh. Motor to buttock muscles, sensory to skin of buttocks, posterior surface of thigh and leg.
  • Pg. 418- 419 Dermatomes- “Each skin surface area supplied by sensory fibers of a given spinal nerve iscalled a dermatome, name that means “skin section.” Image (4)
  • Pg. 421 Myotomes- “skeletal muscle or group of muscle’s that receives motor axons from a given spinalnerve. “ Image (5)
  • ©11 Pg. 421 Brain Olfactory Nerve- sense of smellFacial Nerve- facialexpressions, secretion ofsaliva, and tears. Trigeminal Nerve- sensations of head and face, chewing Vestibulocochlear Nerve- movements. Balance or equilibrium sense. Glossopharyngeal Nerve- Brain StemVagus Nerve- Sensations of tongue,Sensations and swallowing movements, aidmovements. Slows in reflex control of bloodheart, increases pressure.peristalsis. Hypoglossal Nerve- tongue Accessory Nerve – Shoulder movements movements, turning movements of head, movements of viscera, and voice production.
  • Afferent vs. EfferentFunction:  Carries information into the Central Nervous System  Afferent nerves in the Somatic Sensory system, feedback information detected by receptors in skin, skeletal muscles and sense organs.  In the ANS feedback information regarding the autonomic control of the viscera.Purpose:  Help us maintain homeostasis by sensing changes in internal and external environment Above is a chart of the efferent and afferent and the difference between them. ©7
  • Autonomic Nervous SystemFunction: Pathways in the ANS carryinformation to the visceral effectors which arethe smooth muscles, cardiac muscles, and
  • glands. It powers itself without our consciousknowledge. It has two efferent divisionsincluding the sympathetic andparasympathetic division. They are made upof autonomic nerves, ganglia, and plexuses.The parasympathetic division is the “rest andrepair” division that uses acetylcholine it’stransmitter to slow the heartbeat, promotedigestion etc. Parasympathetic stimulationshave different effects on effectors such asconstriction of bronchioles and contraction ofurinary bladder. The sympathetic divisionopposes the parasympathetic impulses whichwould for example, raise the heartbeat.
  • Sympathetic stimulations have effects likedilation of bronchioles and relaxation ofurinary bladder. As a whole, the ANSfunctions to regulate autonomic effectors tomaintain homeostasis. For example, X Vagusgoes to the heart and controls the heartbeat,while the IX Glossopharyngeal goes to thelungs and control respiratory actions.
  • Sympathetic and Parasympathetic SystemsSympathetic divisions consist of neural pathways separate from theparasympathetic pathways. Sympathetic impulses stimulate an effector whileparasympathetic impulses tend to inhibit it. Sympathetic division’s main purposeis to serve as a responder to stressful/increased demanding situations and theparasympathetic division’s main purpose is to serve as a non-emergency, routinebody maintenance function. ©10 ©9Sympathetic is like an ambulance Parasympathetic is like a doctor’s visit(Responding to immediate emergencies) (Routine checkup)