Part 11 Anaphy Kylaa PDF

**FUNCTIONS OF THE NERVOUS SYSTEM** 1. **SENSORY INPUT** - Gathering information - Sensory receptors monitors changes, called stimuli occurring inside and outside of the body 2. **INTEGRATION** - Nervous system processes and interprets sensory input and decides whether action is...

**FUNCTIONS OF THE NERVOUS SYSTEM** 1. **SENSORY INPUT** - Gathering information - Sensory receptors monitors changes, called stimuli occurring inside and outside of the body 2. **INTEGRATION** - Nervous system processes and interprets sensory input and decides whether action is needed 3. **MOTOR OUTPUT** - A response, or effect, activates muscles or glands **NERVOUS SYSTEM CLASSIFICATION ARE BASED ON:** - STRUCTURES ( structural classification ) - ACTIVITIES ( Functional classification ) **STRUCTURAL ORGANIZATION** 1. **CENTRAL NERVOUS SYSTEM ( CNS )** 2. **PERIPHERAL NERVOUS SYSTEM ( PNS )** - Nerves extending from the brain and spinal cord - Spinal nerves- carry impulses to and from the spinal cord - Cranial nerves- carry impulses to and from the brain - **SENSORY (afferent) DIVISION** - Nerve fibers that carry information to the central nervous system - Somatic sensory (afferent) fibers carry information from the skin, skeletal muscles, and joints - Visceral sensory (afferent) fibers carry information from the visceral organs - **MOTOR (efferent) DVISION** - Nerve fibers that carry impulses away from the central nervous system organs to effector organs ( muscles and glands ) - Two subdivision: Somatic nervous system ( voluntary ) -- consciously control skeletal muscles and Autonomic nervous system (involuntary)- automatically controls smooth and cardiac muscles. Divided into sympathetic and parasympathetic nervous system - Supports cells in the CNS are grouped together as **neuroglia** - Support - Insulate - Protect neurons **TWO PRINCIPAL CELL TYPES OF NERVOUS TISSUE** 1. **Supporting cells (called neuroglia, or glial cells, or glia)** - Resemble neurons - Unable to conduct nerve impulses - Never lose the ability to divide 2. **Neurons** - **CNS glial cells: astrocytes** - Abundant, star-shaped cells - Brace and anchor neurons to blood capillaries - Determine permeability and exchanges between blood capillaries and neurons - Control the chemical environment of the brain - **CNS glial cells: micro glia** - Spiderlike phagocytes - Monitor health of nearby neurons - Dispose of debris - **CNS glial cells: ependymal cells** - \> line cavities of the brain and spinal cord - Cilia assist with circulation of cerebrospinal fluid **NERVOUS TISSUE: NEURONS** Nissl bodies (Round endoplasmic reticulum) Neurofibrils (intermediate filaments that maintain cell shape) Processes (fibers) - Dendrites- conduct impulses toward the cell body - Axons- conduct impulses away from the cell body - Neurons have only 1 axon - Synaptic cleft- gap between axon terminals and the next neurons - Synapse- functional junction between nerves where a nerve impulse is transmitted **Myelin**- White, fatty material covering axons. Protects and insulates fibers and speeds nerve impulse transmission **Myelin Sheaths** - Schwann cells- wrap axons in jelly roll-like fashion (PNS) to form the myelin sheath - Neurilemma- part of the Schwann cell external to the myelin sheath - Nodes of Ranvier- gaps in myelin sheath along the axon - Oligodendrocytes- produce myelin sheaths around axons of the CNS - Lack of neurilemma **Terminology** - Nuclei- cluster of the cell bodies in the CNS - Ganglia- collections of the cell bodies outside the CNS in the PNS - Tracts- bundles of nerve fibers in the CNS - Nerves- bundles of nerve fibers in the CNS - White matter- collections of myelinated fibers( tracts ) - Gray matter- mostly unmyelinated fibers and cell bodies **Functional classification** - Sensory (afferent) neurons - Carry impulses from the sensory receptors to the CNS - Receptors include: cutaneous sense organs in skin and Proprioceptors in muscles and tendons - Motor (efferent) neurons - Carry impulses from the central nervous system to viscera or muscles and glands - Inter neurons (association neurons) - Cell bodies located in the CNS - Connect sensory and motor neurons **Structural Classifications** - Based on number of processes extending from the cell body - Multipolar neurons- many extensions from the cell body - Bipolar neurons- one axon and one dendrite - Located in special sense organs, such as nose and eye - Rare in adults - Unipolar neurons- have a short single process leaving the cell body **Functional Properties** - Irritability- ability to respond to a stimulus - Conductivity- ability to transmit the impulse to other neurons, muscles or glands **Depolarization** - The inward rush of sodium ions changes the Polarity at that site **Repolarization** - Membrane permeability changes again and becoming impermeable to sodium ions and permeable to potassium ions. Involves restoring the inside of the membrane to a negative charge and the outer to positive charge **Reflexes** - Rapid, predictable and involuntary responses to stimuli **Reflex arcs** - Where reflexes occur over neural pathways - Two types: Somatic reflexes and Autonomic reflexes **Somatic reflexes** - Reflexes that stimulate the skeletal muscles - Involuntary - Ex. Pulling your hand away from a hot object **Autonomic reflexes** - Regulate the activity of smooth muscles, the heart, and the glands - Ex. Regulation of smooth muscles, heart and blood pressure, glands, digestive system **Five elements of a reflex arc** - Sensory receptor- reacts to a stimulus - Sensory neuron- carries message to the integration center - Integration center (CNS)- processes information and directs motor output - Motor neuron- carries message to an effector - Effector organ- is the muscle or gland to be stimulated **Two neuron reflex arcs** - Simplest type- ex. Patellar reflex **Three neuron reflex arcs** - Consist of receptor, sensory neuron, interneuron, motor neuron and effector - Ex: Flexor reflex **Cerebral hemispheres** - Paired superior parts of the brain - Include more than half of the brain mass - Made of ridges (gyri) and grooves (sulci) **Three main region of cerebral hemisphere** - Cortex is superficial gray matter - White matter - Basal nuclei are deep pockets of gray matter FUNCTIONS OF MAJOR REGIONS OF BRAINS **Cerebral Hemispheres** - Cortex: Gray matter - Localizes and interprets sensory inputs - Controls voluntary and skilled skeletal muscle activity - Acts in intellectual and emotional processing - Basal nuclei: subcortical motor center help control skeletal muscles movements **Diencephalon** - **Thalamus** - Relays sensory impulses to cerebral cortex - Relays impulses between cerebral motor cortex and lower motor centers - Involved in memory - Encloses the third ventricle - **Hypothalamus** - Chief integration center of autonomic (involuntary) nervous system - Regulates body temperature, food intake, water balance and thirst - Regulated hormonal output of anterior pituitary gland , acts as endocrine organ - **Limbic system- Afunctional system ( epithalamus )** - Includes cerebral and diencephalon structures ( eg. Hypothalamus and anterior thalamic nuclei) - Mediates emotional response; involved in memory processing **Brain stem:** - **Midbrain** - Contains visual and auditory reflex centers - Contains subcortical motor centers - Contains nuclei for cranial nerves III and IV, contains projections - **Pons** - Relays information from the cerebrum to the cerebellum - Cooperates with the medullary centers to control respiratory rate and depth - Contains nuclei of cranial of cranial nerves V-VII; contains projection fibers - **Medulla Oblongata** - Relays ascending sensory pathway impulses from skin and proprioceptors - Contains nuclei controlling heart rate, blood vessels diameter, respiratory rate, vomiting. Etc. - Relays sensory information to the cerebellum - Contains nuclei of cranial nerves VII-XII; contains projection fibers - Site of crossover of pyramids - **Reticular formation- A functional system:** - Maintains cerebral cortical alertness; filters out repetitive stimuli - Helps regulate skeletal and visceral muscle activity **Cerebellum** - Process information from cerebral motor cortex, proprioceptors and visual and equilibrium pathways - Provides "instructions" to cerebral motor cortex and subcortical motor centers, resulting in smooth, coordinated skeletal muscle movements - Responsible for proper balance and posture **Cerebrum** - Two hemispheres with convoluted surfaces - Outer cortex of gray matter and inner region of white matter - Controls balance - Provides precise timing for skeletal muscle activity and coordination of body movement **Cerebral Cortex** - Primary somatic sensory area - Located in parietal lobe posterior to central sulcus - Receives impulses from the body's sensory receptors ( pain, temperature, light touch ) - Sensory homunculus is a spatial map - Left side receives impulses from the right side - \- motor homunculus is a spatial map **Cerebral area involved in special senses** - Visual area (occipital lobe) - Auditory area (temporal lobe) - Olfactory area (temporal lobe) **Primary motor area of cerebral cortex** - Located anterior to the central sulcus in the frontal lobe - Allows us to consciously move skeletal muscles **Broca's area (motor speech area)** - Involved in our ability to speak - Usually in left hemisphere **Specialized area** - Anterior association area (frontal lobe) - Posterior association area (posterior cortex) - Speech area (for sounding out words) **Cerebral white matter** - Composed of fiber tracts deep to the gray matter - Corpus callosum connects hemispheres - Corpus callosum also knows as commissures - Association fibers tracts connect the hemisphere - Projection fiber connect the cerebrum with lower CNS centers **Basal nuclei** - **Islands** of gray matter buried deep within the white matter of the cerebrum - Regulate voluntary motor activities **Protection of the Central Nervous System** 1. Meninges 2. Cerebrospinal fluid (CSF) 3. Blood-brain barrier **Meninges** - **Dura mater** - Outermost leathery later - Double-layered External covering - Periosteum- attached to inner surface of the skull - Meningeal layer- outer covering of the brain - Folds inward in several area - Falx cerebri - Tentorium cerebelli - **Arachnoid layer** - Middle layer - Weblike extensions span the subarachnoid space to attach it to the pia matter - Subarachnoid space is filled with cerebrospinal fluid - Arachnoid granulations protrude through the dura mater and absorb cerebrospinal fluid into venous blood - **Pia mater** - Internal layer - Clings to the surface of the brain and spinal cord **Cerebrospinal fluid** - Similar to blood plasm in composition - Formed by choroid plexuses (**choroid plexuses-** capillaries in the ventricles of the brain) - Forms a watery cushion to protect the brain and spinal cord - Circulated in the arachnoid space, ventricles and central canal of the spinal cord Cerebrospinal fluid circulation 1. Produced by the choroid plexus of each ventricle 2. Flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord 3. Flows through the subarachnoid space 4. Is absorbed into the dural venous sinuses via the arachnoid villi Blood-brain barrier - Included the least permeable capillaries of the body - Allows water, glucose, and amino acids to pass through the capillary walls - Useless as a barrier against some substances Brain dysfunction Brain Injuries 1. Concussion - Slight brain injury - Typically little permanent brain damage occurs 2. Contusion - Marked nervous tissue destruction occurs - Coma may occur 3. Death may occur after head blows due to: - Intracranial hemorrhage - Cerebral edema Cerebrovascular accident (CVA), or stroke - Results when blood circulation to a brain area is blocked - Loss of some functions or death may results - Hemiplegia- one sided paralysis - Aphasia-damage to speech center in left hemisphere Transient ischemic attack (TIA) - Temporary brain ischemia (restriction of blood flow) - Numbness, temporary paralysis, impaired speech Spinal cord - Extends from the foramen magnum of the skull to the first or second lumbar vertebra - Cauda equina is a collection of spinal nerves at the inferior end - 31 pairs of spinal nerves arise from the spinal cord - Internal gray matter is mostly cell bodies - Dorsal (Posterior) horns house interneurons - Receive information from sensory neurons in the dorsal root; cell bodies housed in dorsal root ganglion - Anterior (ventral) horns house motor neurons of the somatic (voluntary) nervous system - Send information out ventral root - **Gray matter** surrounds the central canal, which is filled with cerebrospinal fluid - **White matter** of the spinal cord ( composed of myelinated fiber tracts) **THREE REGIONS:** dorsal, lateral, ventral columns Peripheral Nervous System (PNS) - Consist of nerves and ganglia outside the CNS Structure of nerve - Endoneurium -- connective tissue sheath that surround each fiber - Perineurium- wraps groups of fibers bound into a fascicle - Epineurium- binds groups of fascicle Mixed nerve - Contain both sensory and motor fibers - Carry impulses toward the CNS - Carry impulses away from the CNS Sensory nerves 1. Optic 2. Olfactory 3. Vesitabulocochlear CRANIAL NERVES 1. Olfactory - Fibers arise from olfactory receptors in the nasal - Purely sensory; carries impulses for the sense of smell - Subject is asked to sniff and identify aromatic substances 2. Optic - Fibers arises from the retina - Purely sensory; carries impulses from the vagina - Vision and visual field are tested with an eye 3. Oculomotor - Fibers run from the midbrain to the eye - Supplies motor fibers to four of the six muscles - Pupils are examined for size, shape and size equality 4. Trochlear - Fibers run from the midbrain of the eye - Supplies motor fibers for one external eye muscle - Tested in common with cranial nerve III for the ability to follow moving objects 5. Trigeminal - Fibers emerge from the pons - Conducts sensory impulses from the skin of the face and the mucosa - Sensation of pain,touch and temperature area 6. Abducens - Fibers leave the pons and run to the eye - Supplies motor fibers to the lateral rectus muscle - Tested in common with cranial nerve III 7. Facial - fibers leave the pons and run to the face - activates the muscles of facial expression and the lacrimal - anterior two thirds of tongue is tested for ability to taste sweet, salty and sour 8. Vestibulocochlear - Fibers run from the equilibrium and hearing receptors - Purely sensory; vestibular branch - Hearing is checked by air 9. Glossopharyngeal - Fibers emerge from the medulla and run to the throat - Supplies motors to the pharynx the promotor swallowing - Gag and swallowing reflexes are checked 4 10. Vagus - Fibers emerge from the medulla - Fibers carry sensory impulses from and the motor impulses - Tested in common with cranial nerves 11. Accessory - Fibers arise from the superior spinal cord - Mostly motor fibers that activates - Sternocleidomastoid and trapezius muscles are checked for strength 12. Hypoglossal - Fibers run from the medulla to the tongue - Motor fibers control tongue movements - Subject is asked to stick out tongue - 31 pairs - Formed by ventral and dorsal root - Ramus- brand of a spinal nerves contain both motor and sensory fibers - Dorsal rami- serve the skin and muscles of the posterior trunk - Ventral rami- form the intercostal nerves that supply muscles Plexus - Networks of nerves serving motor and sensory needs of limbs - Cervical, brachial,lumbar and Sacral Somatic nervous system - Motor neuron cell bodies originate inside the CNS - Axons extends to skeletal muscles that are served - Chain of two motor neurons - Preganglionic neuron -- in the brain or spinal cord - Postganglionic- neurons extend to the organs - "housekeeping" activities - - Smell - Taste - Sight - Hearing - Equilibrium - Extrinsic eye muscles - Eyelids - Conjunctiva - Lacrimal apparatus External and Accessory structures Eyelids - Meet at the medial and lateral commissure Eyelashes - Tarsal glands produce an oily secretion that lubricates the eye - Ciliary gland are located between the eyelash - Membrane that lines the eyelids and eyeball - Connects with the transparent cornea - Secrete mucus - Lacrimal gland- produces lacrimal fluids situated on lateral end of each eye - Tears drain across the ye 1. Dilute salt solution 2. Mucus 3. Antibodies 4. Lysozyme - Cleanse, protect, moisten and lubricate the eye - Three layers - Fibrous layer- outside layer - Vascular layer- middle layer - Sensory -- inside layer FIBROUS LAYER= sclera+cornea Sclera- white connective tissue layer and seen anteriorly as the "white of the eye" Cornea- transparent, central anterior portion and allows for light to pass through. The only human tissue that can be transplanted without fear of rejection VASCULAR LAYER - Choroid is a blood rich-nutritive layer that contains a pigment - Ciliary body and Iris- regulates amount of light entering eye SENSORY LAYER - Retina contains two layer 1. Outer pigmented layer that absorbs light and prevents it from scattering 2. Inner neural layer that contain rods and cones. - Rods- most are found toward the edges of the retina - Cones- allow for detailed color vision and densest in the center of the retina LENS - Flexible, biconvex crystal-like structure - Held in place by a suspensory ligament attached to the ciliary body - Two chambers: Anterior segment- contains aqueous humor, a clear, watery fluid - Posterior segment -- contains vitreous humor, a gel-like substances Aqueous humor - Watery fluid found between lens and cornea - Helps maintain intraocular pressure - Provides nutrients for the lens and cornea Vitreous humor - Gel-like substances posterior to the lens - Prevents the eye from collapsing - Helps maintain intraocular pressure Ophthalmoscope - Instrument used to illuminate the interior of the eyeball and fundus - Can detect diabetes, arteriosclerosis Optic nerve - Bundle of axons that exit the back of the eye carrying impulses from the retina Optic Chiasma - Location where the optic nerves cross - Fibers from the medial side of each eye cross over to the opposite side of the brain Optic tracts - Contain fibers from the lateral side of the eye - Synapse with neurons in the thalamus Optic radiation - Axons from the thalamus run to the occipital lobe Emmetropia- eye focuses images correctly on the retina Myopia- ( nearsightedness) - Distant objects appear blurry - Light from those objects fail to reach the retina - Results from an eyeball that is too long Hyperopia ( Farsightedness) - Near objects are blurry, distant objects are clear - Results from an eyeball that is too short or from a "lazy lens" Astigmatism - Images are blurry - Results from light focusing as lines, not points on the retina - Convergence: reflexive movement of the eyes - Photopupillary reflex: bright light causes pupil to constrict - Accommodation pupillary reflex: viewing close objects causes pupil to constricts - Auricle (pinna) - External acoustic meatus (auditory canal) -- narrow the chamber in the temporal lobe Middle ear - Air is filled, mucosa-lined cavity within the temporal lobe - Involved only in the sense of hearing - Located between tympanic membrane and oval window - Pharyngotympanic tube (auditory tube) -- links middle ear cavity with the throat Internal ear - Includes sense organs for hearing and balance - Bony labyrinth (osseaous labyrinth) consists of: cochlea, vestibule, semicircular canals Equilibrium ( vestibular apparatus ) - STATIC EQUILIBRIUM - Maculae- receptors in the vestibule. Report on the position of the head, help us keep our head erect - DYNAMIC EQUILIBRIUM - Crista ampullaris- responds to angular or rotational movements of the head - Located in the ampulla of each semicircular canal - Tuft of hair cells covered with cupula HEARING 1. Spiral organ of corti - Located within the cochlear duct - Receptors -- hair cells on the basilar membrane - Cochlear nerve attached to hair cells transmits nerve impulse - High pitched sounds- disturb the short, stiff fibers - Low pitched sounds- disturb the long, floppy fibers - Any degree of hearing loss - Results when the transmission of sound vibration through the external and middle ears is hindered - Results from the damage to the nervous system CHAPTER 9 ENDOCRINE SYSTEM - Second controlling system of the body Hormones that control - Reproduction - Growth and development - Mobilization of body defenses - Maintenance of much of homeostasis - Regulation of metabolism Hormones - Produced by specialized cells - Cells secrete hormone in extracellular fluids - Classified as: amino acids ( proteins, peptides, amines) , steroids ( made from cholesterol), Prostraglandis ( made from highly active lipids ) Endocrinology - Scientific study of hormones and endocrine glands