Anatomy and Physiology Final Exam PDF

ANATOMY AND ○ Functional Classification of PNS: PHYSIOLOGY Motor Efferent Division...

ANATOMY AND ○ Functional Classification of PNS: PHYSIOLOGY Motor Efferent Division Somatic Nervous FINAL EXAMINATION System 1st Term: 2nd Quarter Autonomic Nervous System ○ Developmental Aspects TOPIC OVERVIEW of the Nervous System 2. SPECIAL SENSES 1. THE NERVOUS SYSTEM The Eye and Vision Nervous System ○ Anatomy of the Eye Organization of the Nervous ○ Physiology of Vision System The Ear and Hearing ○ Structural Classification ○ Anatomy of The Ear ○ Functional ○ Hearing and Equilibrium Classification (Balance) Nervous Tissue: Structure and ○ Hearing and Equilibrium Function Deficits ○ Supporting Cells Chemical Senses: Smell and ○ Neurons (Nerve Cells) Taste Structural and Developmental Aspects of the Functional Special Senses Classification of 3. THE ENDOCRINE SYSTEM Neurons Endocrine System ○ Physiology Components and Physiology: Functions of The Nerve Impulse Endocrine System Physiology: Hormone Function Reflex Major Endocrine Organs Central Nervous System Other Hormone-Producing ○ Brain Tissues and Organs Functional Developmental Aspects of The Anatomy of The Endocrine System Brain 4. THE LYMPHATIC SYSTEM ○ Protection of The Central Nervous System ○ Spinal Cord Peripheral Nervous System LESSON 1: THE NERVOUS SYSTEM ○ Structure of a Nerve ○ Cranial Nerve ○ Spinal Nerve 01 NERVOUS SYSTEM  (effectors) via motor Major/master control and output. communication system of the body Effectors: structures Collects information (sensory neuron) such as the internal Brain is the integration center which organs, muscles, analyzes info and provides necessary different glands that controls hormone, response through efferent pathway heart, etc. (motor output) FUNCTIONS Sensory Uses millions of Input sensory receptors to (receives info monitor changes to send to the occurring both inside brain) and outside the body. These changes are called stimuli, and the gathered information is called sensory input. 02 ORGANIZATION OF THE NERVOUS SYSTEM Integration Processes and (integrate interprets the sensory information input and decides and decide what is the response appropbriate response at each moment Carried out by the brain and spinal cord Motor Output Initiate or activate the (activates effectors so it will carry effectors) out the instructions that were transmitted from the brain or STRUCTURAL CLASSIFICATION spinal cord. Causes a response, or Central - Act as the integrating effect, by activating Nervous and command centers muscles or glands System of the nervous system.  - Interpret incoming System is divided into: sensory information 1. Spinal nerves and issue instructions - carry impulses to and based on past from the spinal cord. experience and current conditions. 2. Cranial nerves - carry impulses to and The Central Nervous System is from the brain. divided into: 1. Brain: FUNCTIONAL CLASSIFICATION - Recelves and (concerns PNS only) processes sensory information, initiates Sensory - Nerve fibers that carry responses stores, Division information to the memories generates central nervous system thoughts and emotions. The one who receive the stimuli is further divided into: 2. Spinal cord 1. Somatic sensory (afferent) - Conducts signals to - Nerve fibers that and from the brain, receive info from our controls reflex skin, joints, skeletal activities. muscles. They carry these toward the CNS. Peripheral - includes all parts of the 2. Visceral sensory (afferent) System nervous system - Nerve fibers that outside the CNS. receive information - It consists mainly of from the internal the nerves that extend organs such as from the spinal cord stomach, heart, lungs, and brain. and glands. They carry - Serve as these toward the CNS. communication lines. - Link all parts of the Motor - Nerve fibers that carry body by carrying Division impulses away from impulses from the the central nervous sensory receptors to system organs to the CNS and from the effector organs CNS to the appropriate (muscle and glands) glands or muscles. The Peripheral Nervous The one who will send  - General functions: response is further divided into: - Support 1. Somatic nervous system - Insulate neurons (voluntary) - Protect delicate neurons from - Voluntarily controls damage and infection skeletal muscles - Even though it is THE NEUROGLIA IN THE CNS IS COMPOSED OF CNS involuntary, the actions GLIAL CELLS: are coordinated by skeletal muscles ASTROCYTES - Reflexes are included 2. Autonomic nervous system Astro: star ( involuntary) Neuroglia: neuro, glia - glue - Automatically controls Abundant versatile, star shaped cells smooth and cardiac They have numerous projections with muscles and glands swollen ends that attach to neurons and - Gives instructions in anchor them to blood capillaries. what responses our Serve as a living barrier between cardiac muscles will be capillaries and neurons. - Divided into the Help regulate capillary permeability and sympathetic and facilitate exchanges between blood and parasympathetic neurons. nervous system (bring Protect neurons from harmful about opposite effects, substances in the blood. what one stimulates, Control the chemical environment in the the other inhibits) brain by: ○ Absorbing leaked potassium ions, which are involved in nerve 03 NERVOUS TISSUE: STRUCTURE AND impulse generation. FUNCTION ○ Recapturing chemicals released for neural communication. A. SUPPORT CELLS MICROGLIA - Support cells in the CNS are Spiderlike phagocytes “lumped/grouped together” as They monitor the health of nearby neuroglia (also called as glia or glial neurons. cells)  Responsible for phagocitizing/disposing of debris, such as: ○ Dead brain cells ○ Bacteria Main function: Defend the central nervous system Resident/fixed macrophage of the CNS EPENDYMAL CELLS Line cavities of the brain and spinal cord Cilla assist with circulation of cerebrospinal fluid NERVE CELLS ○ CSF is produced by the colloid flexus of the hypothalamus; it Cells specialized to receive from the cushion the delicate brain and dendrites and transmit messages from spinal cord the axon (nerve impulses) Help the circulation of cerebrospinal fluid from the brain to the spinal cord Major regions of all neurons: and vice versa Despite that they have a different type or That's why it's helpful in giving a structure, they have 2 common regions protective watery cushion to the CNS. (1) all neuron have 1 cell body (2) all neurons have processes ○ Cell body - center; contains the OLIGODENDROCYTES nucleus & the different organelles, and metabolic center Myelinating cells of the CNS of the cell, atp generation Wrap flat extensions around nerve fibers ○ Processes - fibers that extend in the central nervous system from the cell body, projections Produce myelin sheaths (fatty from the cell body insulating coverings), which acts as the protective layer around the nerve fibers CELL BODY B. NEURONS Is the metabolic center of the neuron It has no centrioles, therefore, they are considered amitotic apparatus PARTS OF A NEURON  Nucleus with large nucleolus katawan, hindi talaga. They are Nissl bodies separated by a small gap called Rough endoplasmic reticulum synaptic cleft (responsible for protein synthesis) Abundant in the cell body MYELIN Neurofibrils ○ Intermediate filaments that White, fatty material covering axons maintain cell shape Protects and insulates fibers ○ abundant in the cell body Increasing the transmission of nerve impulse from one neuron to its target PROCESSES (FIBERS) cells Speeds nerve impulse transmission 1. Dendrites Produce for the CNS by the DendriTes (T - towards the body) oligodendrocytes conduct impulses toward the cell body Peripheral nervous system: produced by Neurons may have hundreds of the schwann cells dendrites depending on the neuron type Myelin sheet is rolled around the axon 2. Axons and know called as schwann cells. Axons (A - away the body) conduct impulses away from the cell body 1. Schwann cells Neurons have only one axon arising from wraps axons in a jelly roll - like fashion the cell body at the axon hillock (PNS) to form the myelin sheath Conduct impulses toward the target cell Neurilemma or away the cell body ○ part of the Schwann cell external It has a collateral branch along its length to the myelin sheath ; the plasma End in axon terminals, which contain membrane of the schwann cell; vesicles with neurotransmitters. ( dulo ng outermost layer ; more secured axon terminals can branch out to protective layer, projections, which connected to another Nodes of ranvier neuron or certain body cells) ○ gaps in myelin sheath along the Vesicles: Neurotransmitter which is axon; in between of different important for sending nerve impulses schwann cells Axon terminals are separated from the next neuron by a gap 2. Oligodendrocytes ○ Even though sinabi na produce myelin sheaths around axons of magkakaconnect yung nerves ng the CNS; it is bigger and mas marami  siya nababalot compare kay schwann SENSORY Carry impulses from cells. (AFFERENT) the sensory receptors DOWNSIDE: Lack a neurilemma NEURONS to the CNS- ○ Thus, the damage when the Transmits sensory nerve fibers/neurons situated in inputs to the CNS the CNS is also damaged NEURONS ARE EITHER MYELIN OR UNMYELINATED! Myelinated: presence of sheath around the fibers Unmyelinated: absence of sheath around the RECEPTORS: fibers 1. Cutaneous sense organs in skin TERMINOLOGIES - Common in our skin: Pain receptors/bare Nuclei nerve ending. Least ○ Clusters of cell bodies in the CNS specialized among Ganglia the cutaneous sense ○ Collections of cell bodies outside but they are the CNS in the PNS. Its a network abundant or relay station of information (sharing of info) Tracts ○ Bundles of nerve fibers in the CNS Nerves ○ Bundles of nerve fibers in the PNS 2. Proprioceptors in muscles White Matter and tendons ○ Collections of myelinated fibers( - Detect our muscle tracts) tone, tension and Gray Matter determine degree of ○ Mostly unmyelinated fibers and muscle stretch to cell bodies help maintain our posture and balance FUNCTIONAL CLASSIFICATION  - Carry impulses to the Most common spinal cord so we structural type can adjust our posture BIPOLAR One axon and one NEURONS dendrite Located in special sense organs, such as nose and eye MOTOR Carry impulses from Rare in adults (EFFERENT) the central nervous Found in some sense NEURONS system to viscera organs and/ or muscles and Acts as receptor cell glands. UNIPOLAR Single process INTERNEURON Cell bodies located in NEURONS emerging from the S the CNS cell body (ASSOCIATION ○ For both The axon conducts ) NEURONS motor nerve impulses both neurons and toward and away interneurons, from the cell body the cell bodies Sensory neurons are both found in PNS ganglia located in the are unipolar CNS Connect sensory and motor neurons in C PHYSIOLOGY: IMPULSES neural FUNCTIONAL PROPERTIES OF A NEURON STRUCTURAL CLASSIFICATION IRRITABILITY The ability to MULTIPOLAR Many extensions respond to a NEURONS from the cell body stimulus by All motor and producing a nerve interneurons are impulse. multipolar  Mechanism of Action Potential CONDUCTIVITY The ability to The permeability properties of the transmit the plasma membrane change impulse to other briefly upon stimulation, neurons, muscles, regardless of the type of stimulus. or glands. This leads to the generation of a nerve impulse, initiating the conduction process. ELECTRICAL CONDITIONS OF A RESTING NEURON'S MEMBRANE 1. POLARIZED Resting membrane is polarized. The plasma membrane of a resting In the resting state, the external (inactive) neuron is polarized, meaning face of the membrane is slightly there are fewer positive ions on the inner positive; its internal face is slightly face of the plasma membrane than on its outer face. negative. Ion distribution: The chief extracellular ion is ○ Inside the cell: Major positive ion sodium (Na*), whereas the chief is potassium (K⁺). intracellular ion is potassium (K*). ○ Outside the cell: Major positive ion The membrane is relatively is sodium (Na⁺). impermeable to both ions. The membrane is more permeable to K⁺ than to Na⁺, allowing K⁺ ions to exit the 2. STIMULUS INITIATE LOCAL cell. DEPOLARIZATION This creates a more negative charge inside the neuron compared to the A stimulus changes the outside, maintaining the neuron’s permeability of a local "patch" of resting state. the membrane, and sodium ions diffuse rapidly into the cell. ACTION POTENTIAL: INITIATION AND This changes the polarity of the GENERATION membrane (the inside becomes more positive; the outside Neurons are excited by various stimuli, becomes more negative) at that including: site. ○ Light: Activates eye receptors. ○ Sound: Activates ear receptors. ○ Pressure: Activates cutaneous 3. DEPOLARIZATION AND GENERATION OF (skin) receptors. AN ACTION POTENTIAL Most neurons in the body, however, are excited by neurotransmitter chemicals If the stimulus is strong enough, released by other neurons. depolarization causes  membrane polarity to be completely reversed, and an action D. PHYSIOLOGY: REFLEXES Reflexes are under the somatic response 4. PROPAGATION OF THE ACTION Reflexes are rapid, predictable, and POTENTIAL involuntary responses to stimuli. They are essential for daily bodily Depolarization of the first functions and occur along neural membrane patch causes pathways called reflex arcs, involving permeability changes in the both the central nervous system (CNS) adjacent membrane, and the and peripheral nervous system (PNS). events described in step 2) are Reflexes can be thought of as repeated. pre-programmed responses to stimuli Thus, the action potential that always follow the same pattern, propagates rapidly along the much like a one-way street. entire length of the membrane. TYPES OF REFLEXES 5. REPOLARIZATION SOMATIC Stimulate skeletal Potassium ions diffuse out of the REFLEXES muscles. These are cell as the membrane involuntary permeability changes again, reflexes, even restoring the negative charge on though skeletal the inside of the membrane and muscles are the positive charge on the typically under outside surface. Repolarization voluntary control. occurs in the same direction as Example: Pulling depolarization. your hand away from a hot object 6. INITIAL IONIC CONDITIONS is a somatic reflex The ionic conditions of the resting AUTONOMIC Regulate the state are restored later by the REFLEXES activity of smooth activity of the sodium-potassium muscles, the heart, pump. Three sodium ions are and glands. ejected for every two potassium ions carried back into the cell.  ○ Determine the general health of a Example: The patient, and if there is a problem salivary reflex with the nervous system. (secretion of ○ Takes faster than the latter reflex saliva) and the arc. pupillary reflex ○ The patellar reflex (knee-jerk) is a (change in pupil simple example of a two-neuron size). These reflex arc. It involves a stretch of reflexes control the quadriceps muscle and is body functions like typically tested during a physical digestion, exam to assess motor function in elimination, blood the nervous system. pressure, and 2. Three-Neuron Reflex Arc: sweating. ○ The flexor (withdrawal) reflex is more complex and involves three FIVE BASIC ELEMENTS OF A REFLEX ARC neurons: a sensory neuron, an interneuron in the CNS, and a All reflex arcs contain at least five elements: motor neuron. This reflex occurs 1. Receptor: when a limb withdraws from a Reacts to a stimulus. painful stimulus. 2. Sensory Neuron: ○ Reflex arcs with more synapses Carries the impulse to the CNS. take longer to occur due to the 3. Integration Center (Interneuron): delay at synapses where Located in the CNS, typically in neurotransmitters diffuse. the spinal cord or brain. 4. Motor Neuron: Carries the impulse from the CNS EXAGGERATED REFLEXES to the effector. 5. Effector: DISTORTED Can not be The muscle or gland that predicted responds to the stimulus. ABSCENNSE Can say something about TYPES OF REFLEX ARC the condition of our nervous 1. Two-Neuron Reflex Arc: system  3. Basal Nuclei 04 CENTRAL NERVOUS SYSTEM CEREBRAL CORTEX A. BRAIN Has superficial gray matter; external 2 good fistfuls of pinkish gray tissue, Function: Speech, memory, wrinkled like a walnut and with the logical and emotional responses, texture of cold oatmeal consciousness, interpretation of Weighs a little over 3lbs sensation, voluntary movements Divided into 4 major regions: 1. Cerebral Hemispheres LOBES WITHIN THE BRAIN (Cerebrum) 2. Diencephalon (Interbrain) FRONTAL LOBE Controls 3. Brain Stem voluntary motor 4. Cerebellum functions (primary motor CEREBRAL HEMISPHERES (Cerebrum) area), motivation, aggression, mood collectively called as cerebrum and olfaction. most superior part; larger than the other PARIETAL LOBE Primary 3 regions combined somatosensory Cerebral hemisphere is separated by a area single deep fissure called longitudinal fissure Location: posterior to the PURPOSE: anatomical landmarks central fissure/sulcus ○ Gyri: elevated ridges of tissue ○ Sulci: Functions: shallow grooves that Impulses from separates gyri body’s sensory Divides each cerebral area are hemisphere into lobes interpreted in this Fissures: deeper area grooves; lesser Allows you to Divided into 3 basic regions recognize pain, 1. Cerebral Cortex temperature 2. White Matter  differences, and Called psychic light touch cortex: for Reception and abstract thinking perception center for most sensory WHITE MATTER information Location: Deep to the cortex Sensory Speech Area Different from gray matter since 1. Wernick’s Area its myelinated Wernicke's area involved BASAL NUCLEI processing and understanding Location: buried deep within the language white matter of the cerebrum 2. Broca’s Area "Islands" of gray matter Any damage in Regulate voluntary motor the broca's area activities by modifying will prevent you instructions sent to skeletal from talking muscles by the primary motor cortex NOTE: Impulses from special sense organs DIENCEPHALON (Interbrain) are interpreted in other cortical areas Location: Sits atop of the brain stem and OCCIPITAL LOBE Visual area: is enclosed by the cerebral hemispheres posterior of Major structures occipital lobe 1. Thalamus 2. Hypothalamus: below the TEMPORAL LOBE Auditory: thalamus temporal lobe 3. Epithalamus: above the bordering the thalamus lateral sulcus & olfactory area THALAMUS deep inside the Complex Location: Encloses the shallow memories third ventricle of the brain  ○ Relay station for sensory ○ Hypothalamus also regulates the impulses passing upward to the pituitary gland (endocrine sensory cortex system) ○ Site for localization and Pituitary gland hangs from interpretation of the impulses the anterior floor of the As impulses surge through hypothalamus by a here, we get a sensation slender stalk called whether we are about to “infundibulum” have pleasant or responsible for the release unpleasant sensations. of hormones (Neurons of sensory cortex ○ Houses mammillary bodies will transfer impulses to Reflex center involved in the correct part of the olfaction, associating cortex) those things to past experiences and HYPOTHALAMUS emotional response Location: Under the thalamus EPITHALAMUS ○ Makes up the floor of the diencephalon Location: Above or upon the ○ An important autonomic center: thalamus, forms the root of the Regulates body 3rd ventricle temperature, water Houses the following important balance, and metabolism structure: Center for many drives ○ Pineal gland/body and emotions An endocrine gland ○ Also a part of the limbic system Responsible for the or emotional-visceral brain release of melatonin The following centers are ○ Choroid plexus of the 3rd in the hypothalamus: ventricle Thirst Knots of capillaries within Appetite each of the 4 ventricles Sex Important for Pain Cerebrospinal Fluid Pleasure production BRAIN STEM  Size of a thumb in diameter and approx. ○ Regulates breathing, 3 inches long chewing, swallowing, Functions salivation, and balance ○ Has small gray matter areas Pyramids: ○ Nuclei produce behaviors ○ Prominent enlargements necessary for survival anterior to the medulla ○ Control vital activities like ○ Involved in voluntary breathing and blood pressure control of skeletal muscles Divided into 3 parts/structure: 1. Midbrain MEDULLA OBLONGATA 2. Pons 3. Medulla Oblongata Most inferior part of the brain stem MIDBRAIN Merges into the spinal cord Has many nuclei that regulate Smallest portion of the brain vital visceral functions stem Contains important centers that Dorsally located to that area are control: the 4 colliculus/corpora ○ Heart rate quadrigemina ○ Blood pressure ○ For hearing and balance ○ Breathing Auditory and visual reflex center ○ Swallowing Anteriorly located will be the ○ Vomiting cerebral peduncles (little feet) ○ For impulse transmission ADDITIONAL: RETICULAR FORMATION Substantia nigra: A black mass which regulates general body Diffused mass of gray matter movements along the brain stem Responsible for cyclical motor PONS functions, like walking and chewing, and control over the Pons are called bridge because it internal organs connects the cerebellum and Reticular activating system cerebrum (RAS) Location: Above the medulla ○ Plays a role in Function: awake/sleep cycles and consciousness  ○ Filter for incoming sensory DURA MATER information CEREBELLUM “Dura” meaning hard (matter) Outermost leathery layer Large & cauliflower-like mass Double-layered external Has gyri (elevations) and sulci covering. (grooves) Consists of: Has an outer cortex made of gray matter ○ Periosteum and inner region of white matter attached to inner Function: surface of the skull ○ For balance, muscle tone (state ○ Meningeal layer of being ready), coordinated outer covering of movement, and learning a motor the brain skill (e.g. playing a piano) Folds inward in several areas ○ Provides precise timing for ○ Falx cerebri skeletal muscle activity ○ Tentorium cerebeli ○ Body movements are smooth and coordinated ARACHNOID LAYER Plays its role less if sedated by alcohol Middle layer Any damage to this area Weblike extensions span the would result to ataxia, subarachnoid space to attach it clumsy drunken-like to the pia mater movement Subarachnoid space is filled with cerebrospinal fluid Arachnoid granulations protrude B. PROTECTION OF THE CENTRAL NERVOUS through the dura mater and SYSTEM absorb cerebrospinal fluid into venous blood Meninges Cerebrospinal fluid (CSF) PIA MATER MENINGES Internal layer Clings to the surface of the brain Three connective tissue membranes and spinal cord covering and protecting the CNS structures CEREBROSPINAL FLUID  Similar to the blood plasma in 31 pairs of spinal nerves arise from the composition spinal cord CSF forms a watery cushion to protect The spinal cord is consist of: the brain and spinal cord ○ Central mass of gray matter Circulated in the arachnoid space, ○ Peripheral gray matter ventricles, and central canal of the ○ Peripheral array of white matter spinal cord Any back blockage in the passageway GRAY MATTER will cause hydrocephalus Gray matter: looks like a butterfly or the CSF CIRCULATION letter “H”. 1. Produced by choroid plexus of DORSAL/POSTERIOR HORNS each ventricle 2. CSF flows through the ventricles consist of central processes of and into the subarachnoid space sensory and association neurons via the median and lateral that enter the dorsal root. apertures. Some CSF flows through the central canal of the VENTRAL/ANTERIOR HORNS spinal cord two anterior projection with cell 3. CSF flows through the bodies of motor and association subarachnoid space neurons that leave the ventral 4. CSF is absorbed into the dural root. venous sinuses via the arachnoid Together, the dorsal and ventral granulations root, will form the spinal nerves C. SPINAL CORD Damaged to the ventral root will result to flaccid paralysis, the Extends from the foramen magnum of impulses cannot go the effects the skull to the first or second lumbar because it cannot go out of the vertebra spinal cord ○ Foramen magnum is found in the At the center is a Central Canal posterior part of the skull containing CSF Cauda equina is a collection of spinal nerves at the inferior end WHITE MATTER Provides a two-way conduction pathway to and from the brain  with myelinated fiber tracts, divided into columns/funiculus. Components: ○ Temperature, pressure, POSTERIOR COLUMN and pain receptors in the skin. contains ascending tracts ○ Proprioceptors in muscles (sensory/afferent tracts) carrying and joints. input to the brain SPECIAL SENSE RECEPTORS LATERAL AND ANTERIOR COLUMN Structure: contain both ascending and ○ Either large, complex sensory descending motor tracts carrying organs (e.g., eyes and ears). impulses from the brain to the ○ Or localized clusters of receptors skeletal muscles (e.g., taste buds and olfactory epithelium. LESSON 2: SPECIAL SENSES Humans are highly responsive to stimuli 01 THE EYE AND VISION in their environment: ○ Example 1: Freshly baked bread Of all the senses, vision has been studied stimulates salivation. most. ○ Example 2: Sudden thunder elicits ○ Nearly 70% of all sensory a startle response. receptors in the body are in the These stimuli are continuously eyes. interpreted by our nervous system. The optic tracts that carry information from the eyes to the brain are massive SPECIAL SENSES bundles, containing over a million nerve fibers. The other four traditional senses—smell, We rely heavily on our sight and often taste, sight, and hearing—are classified have to "see it to believe it" as special senses. Additional Special Sense: A. ANATOMY OF THE EYE ○ Equilibrium: Housed in the ear alongside the organ of hearing. Sphere measuring approximately 1 inch (2.5 cm) in diameter. TOUCH: A GENERAL SENSE  Only the anterior one-sixth of the eye's ○ Located on the medial surface is visible; the rest is enclosed aspect of each eye. and protected by: ○ Contains sebaceous and ○ A cushion of fat. sweat glands that ○ The walls of the bony orbit. produce an oily, whitish secretion for lubrication. CONJUNCTIVA EXTERNAL AND ACCESSORY STRUCTURES Accessory Structures includes: A delicate membrane that: ○ Extrinsic eye muscles Lines the eyelids. ○ Eyelids Covers part of the outer ○ Conjunctiva eyeball surface. ○ Lacrimal apparatus ○ Ends at the edge of the EYELIDS transparent cornea, fusing with corneal epithelium. ○ Eyelids meet at: Secretes mucus to lubricate and Medial commissure moisten the eyeball. (canthus). Lateral commissure LACRIMAL APPARATUS (canthus). ○ Space between open eyelids: Lacrimal gland: Located above Palpebral fissure. the lateral end of each eye, Eyelashes and Glands: producing tears (a dilute salt ○ Eyelashes: Project from solution). eyelid borders. Ducts: Drain tears into the nasal ○ Tarsal glands: Modified cavity. sebaceous glands Tear Pathway: producing an oily ○ Lacrimal glands → secretion to lubricate the Anterior eyeball surface → eye. Lacrimal canaliculi → ○ Ciliary glands: Modified Lacrimal sac → sweat glands located Nasolacrimal duct → between eyelashes, with Inferior meatus of the ducts opening at eyelash nasal cavity. follicles. Tear Composition and Function: Lacrimal Caruncle:  ○ Contain mucus, INTERNAL STRUCTURES: THE EYEBALL antibodies, and lysozyme (an enzyme that destroys The eyeball is a hollow sphere. bacteria). Wall Composition: Three tunics (layers). ○ Function: Interior: Filled with fluids called humors to Cleanse and maintain shape. protect the eye Lens: surface. ○ Acts as the main focusing Moisten and apparatus of the eye. lubricate the eye. ○ Held upright by a suspensory Increased Lacrimal Secretion: ligament (ciliary zonule). ○ Causes: ○ Divides the eye into two Emotional upset. chambers. Irritation by foreign objects or FIBROUS LAYER chemicals. ○ Results: Tears spill over Sclera: eyelids. ○ Thick, white connective Nasal cavities fill, tissue; the “white of the leading to "sniffles". eye.” ○ Enhanced tearing helps Cornea: wash away irritants or ○ Transparent, crystal-clear dilute substances. “window” that allows light Emotional Tears: to enter.: ○ Poorly understood but ○ Supplied with nerve suspected to reduce endings (mostly pain stress. fibers). ○ Triggers blinking and tear EXTRINSIC EYE MUSCLES production when touched. ○ Highly exposed yet exceptionally Six muscles are attached to the self-repairing. outer surface of each eye. ○ Lacks blood vessels, Responsible for gross eye making it ideal for movements and tracking moving transplants without objects. rejection.  Acts as VASCULAR LAYER phagocytes for damaged receptor Choroid: cells. ○ Blood-rich, nutritive layer. Stores vitamin A ○ Contains dark pigment to (essential for prevent light scattering. vision). Ciliary Body: ○ Inner Neural Layer: ○ Smooth muscle structure Contains millions attached to the lens via of photoreceptors the ciliary zonule. (rods and cones). Iris: Photoreceptor ○ Pigmented structure with Function: Respond a central opening, the to light. pupil, through which light Signal Pathway: enters. Photoreceptors → ○ Circular muscles: Bipolar cells → Constrict the pupil in Ganglion cells → bright light or for close Optic nerve → vision. Optic cortex (result: ○ Radial fibers: Dilate the vision). pupil in dim light or for ○ Optic Disc: distant vision. Location where the ○ Controlled by Cranial optic nerve exits Nerve III (oculomotor the eye. nerve). Lacks photoreceptors, SENSORY LAYER creating a blind spot. ○ Rods: Retina: Densest at the ○ Delicate, two-layered retina’s periphery; structure: fewer near the ○ Outer Pigmented Layer: center. Absorbs light and Enable vision in prevents scattering dim light and gray (similar to choroid tones; responsible cells).  for peripheral Maintains vision. intraocular ○ Cones: pressure (pressure Densest in the inside the eye). retina's center, Provides nutrients decreasing toward to the avascular the edge. lens and cornea. Allow color vision ○ Production and and sharp detail in Reabsorption: bright light. Secreted by a ○ Fovea Centralis: special area of the Tiny pit lateral to choroid. the blind spot. Reabsorbed into Contains only the venous blood cones and via the scleral provides greatest venous sinus visual acuity (canal of (sharpest vision). Schlemm), located at the junction of LENS the sclera and cornea. A flexible biconvex crystal-like Posterior Segment (Vitreous structure. Segment): Held upright by the ciliary zonule, ○ Location: Posterior to the which is attached to the ciliary lens. body. ○ Contents: Filled with Divides the eye into two vitreous humor (gel-like segments (chambers). substance, also called the Anterior Segment (Aqueous vitreous body). Segment): ○ Vitreous Humor: ○ Location: Anterior to the Prevents the lens. eyeball from ○ Contents: Filled with collapsing inward aqueous humor (clear, by reinforcing it watery fluid). internally. ○ Aqueous Humor: Similar role to how water keeps a  water balloon Light is bent, or refracted by the cornea, inflated. aqueous humor, lens, and vitreous humor ○ The refractive power of the ADDITIONAL: cornea and humors are content. The lens can be changed to less Ophthalmoscope or more convex. An instrument used to illuminate the More convex = the more it bends the light. The flatter interior of the eyeball. the lens, the less it bends Allows examination of: the light The eye is set for distant vision (over 20 ○ Retina feet away) ○ Optic disc ○ Our eyes are made for distant ○ Internal blood vessels (at the visions wherein the lens does not fundus or posterior wall of the need to change to focus on the eye). retina Detects pathological conditions such Accommodation: The lens must change shape to focus on closer objects (less as: than 20 feet away) ○ Diabetes ○ If light comes from a close object, ○ Arteriosclerosis the light will scatter and diverge ○ Degeneration of the optic nerve making the lens bulge more in and retina order to make close vision possible. This change is called accommodation B. PHYSIOLOGY OF VISION Image formed on the retina is a real image Real images are PATHWAY OF LIGHT THROUGH THE EYE AND ○ Reversed from left to right LIGHT REFRACTION ○ Upside down ○ Smaller than the object Light must be focused to point on the retina for optimal vision VISUAL FIELDS AND VISUAL PATHWAYS TO ○ That is why as light passes THE BRAIN through the pupil of the iris it is focused on the retina by the corneal lens and humors ○ When light passes from VISUAL FIELDS AND VISUAL substances with different PATHWAYS TO THE BRAIN densities, the light becomes refracted or bent OPTIC NERVE Bundle of axons The optic tracts that exit the back will synapse with of the eye neurons in the carrying impulses thalamus whose from the retina axons form optic will be bundled at radiation the back of the eye and will then OPTIC RADIATION Axons from the leave as optic thalamus run to nerves through the occipital lobe the optic disc. Axons will Then, the will synapse with move towards cortical cells and the brain vision OPTIC CHIASMA Location where interpretation the optic nerve (seeing occurs) crosses Fibers from the medial side of VISUAL FIELDS each eye will cross over to the ○ Each eye “sees” a slightly opposite side of different view called visual fields the brain ○ Field of view overlaps for each eye BINOCULAR VISION OPTIC TRACTS Tracts formed from the cross Results and provides depth over are called perception (3D vision) optic tracts It contain fibers EYE REFLEXES from the lateral side of the eye on Convergence: Reflexive movement of the same side the eyes medially when we focus on a and the medial close object Photopupillary reflex: Bright light causes side of the pupils to constrict opposite eye Accommodation pupillary reflex:  Viewing close objects causes pupils to auditory canal, but in humans, constrict this function is largely reduced. External Acoustic Meatus (Auditory 02 THE EAR AND HEARING Canal): ○ A short, narrow channel (about 1 inch long and ¼ inch wide) Ear houses two senses carved into the temporal bone of ○ Hearing the skull. ○ Equilibrium or balance ○ It is lined with skin that contains Within our ears we have the ceruminous glands, which Mechanoreceptors secrete cerumen (earwax). This ○ receptors involved in hearing sticky substance traps foreign and detection of equilibrium. bodies and repels insects. This is in comparison with the Tympanic Membrane (Eardrum): photoreceptors in the eyes. ○ At the end of the auditory canal, Furthermore, there are more specific sound waves cause this mechanoreceptors in the ears membrane to vibrate, separating the external ear from the middle A. ANATOMY OF THE EAR ear. The ear is anatomically divided into MIDDLE EAR three major parts: the external ear, the middle ear, and the internal ear. ○ The external and middle ear are Tympanic Cavity: involved only with hearing. ○ A small, air-filled, mucosa-lined ○ The internal ear functions in both cavity within the temporal bone. equilibrium and hearing. ○ It is bordered by the eardrum laterally and by a bony wall with EXTERNAL EAR two openings (oval window and round window) medially. Auricle (Pinna): Pharyngotympanic Tube (Auditory ○ The shell-shaped structure most Tube): people recognize as the "ear." It ○ Connects the middle ear cavity to surrounds the opening of the the throat (pharynx). auditory canal. ○ It typically remains closed but ○ In many animals, the auricle can be briefly opened by funnels sound waves into the swallowing or yawning to  equalize pressure between the bone behind the eye socket. It middle ear and the external consists of three parts: environment. This helps the ○ Cochlea: eardrum vibrate freely, improving A spiraling, pea-sized hearing. structure responsible for ○ When the pressures are unequal, hearing. it can cause ear discomfort and ○ Vestibule: difficulty hearing. Positioned between the ○ In infants, the horizontal semicircular canals and orientation of the tube makes it cochlea, involved in more susceptible to infection if balance. they are lying flat while feeding. ○ Semicircular Canals: Ossicles: Responsible for balance ○ Three tiny bones (the smallest in and detecting head the body) span the tympanic movement. cavity and amplify vibrations Membranous Labyrinth: from the eardrum. ○ A system of membrane sacs ○ Malleus (Hammer): suspended within the bony First bone that vibrates labyrinth. The membranous with the eardrum. labyrinth follows the shape of the ○ Incus (Anvil): bony labyrinth and contains: The second bone that ○ Endolymph: transfers vibration from A thicker fluid found inside the malleus to the stapes. the membranous ○ Stapes (Stirrup): labyrinth. The third bone that Perilymph: transmits vibrations to the ○ A plasma-like fluid that fills the oval window, starting the bony labyrinth and suspends the fluid motion in the inner membranous labyrinth. ear. B. HEARING AND EQUILIBRIUM (BALANCE) INTERNAL EAR Bony Labyrinth: HEARING ○ A maze of bony chambers located deep within the temporal Spiral organ of corti  ○ Located within the cochlear duct Equilibrium receptors of equilibrium are ○ Receptors = hair cells on the found in the inner ear and are basilar membrane collectively called vestibular apparatus ○ Gel-like tectorial membrane is Vestibular has two functional parts capable of bending hair cells ○ Static equilibrium ○ Cochlear nerve attached to hair Has maculae that acts as cell transmits nerve impulses to the receptor auditory cortex on the temporal ○ Dynamic equilibrium lobe Has crista ampullaris that ○ Once the hair cells are acts as receptors stimulated, they send impulses ○ Both static and dynamic along the cochlear nerve (a equilibrium has hair cells that division of cranial nerve VIII—the acts as a specific receptor for vestibulocochlear nerve) to the both hearing and equilibrium auditory cortex in the temporal lobe, where the sound is STATIC EQUILIBRIUM interpreted. ○ Stereophonic (stereo) hearing Maculae occurs because sound usually ○ Receptors found in the reaches each ear at slightly membranous sacs of the different times. This helps the vestibule brain determine the direction ○ Report on the position of the from which sounds are coming. head with respect to gravity ○ High-pitched sounds when the body is at rest Disturb the short, stiff ○ Helps us keep our head erect fibers of the basilar ○ Sends information via the membrane vestibular nerve (division of Stimulates the receptor cranial nerve VIII) to the cells close to the oval cerebellum of the brain window ○ Low-pitched sounds Disturb the long, floppy ANATOMY OF THE MACULAE fibers of the basilar membrane Hair cells are embedded in the Stimulates Specific hair otolithic membrane cells further along the The otolithic membrane are cochlea studded with the otholiths or tiny crystal-like structure composed EQUILIBRIUM of protein and calcium carbonate Otholits (tiny crystal-like stones) float in a gel around hair cells Equilibrium responds to different head Movements in the head cause movements otoliths to roll and pulls the  otolithic membrane causing the B. HEARING AND EQUILIBRIUM DEFICITS hairs to bend activating the hair cells sending impulses via the Deafness is any degree of hearing loss vestibular nerves towards the cerebellum of the brain HEARING AND EQUILIBRIUM DEFICITS DYNAMIC EQUILIBRIUM CONDUCTION Results when the DEAFNESS transmission of Crista ampullaris sound vibrations ○ Located in the ampulla of each of through the the bases of semicircular canal external and There are 3 semicircular middle ears is canals that are lying hindered nearly at a right angle of Something each other. One ayt the interferes with the transverse plane, one at conduction of the coronal plane, and sound vibrations one at the sagittal plane to the fluids of the This arrangement allows inner ear detection of direction by a May be person permanent of the crista consists a ridge temporary of crest of epithelium will a Caused by curve gelatinous mass mechanical called the cupula factors ○ Tuft of the hair cells covered with Ex. Build up of the cupula (gelatinous cap) earwax, fusion of Cupula does not contain ossicles, ruptured otoliths therefore, it does eardrum, not respond to inflammation in gravitational pull. It only the middle ear responds to rotational movements of the head Movement of the SENSORINEURAL Results from endolymph moves the DEAFNESS degeneration or cupula bending the hair damage to the and causing hair cells to receptor cell in be stimulated causing the spiral organ impulses to travel from of corti, cochlear the vestibular nerve to the nerve, or to the cerebellum neurons of the auditory corte