The Nervous System PDF

The Nervous System JESSIAH JOY E. SEGISMUNDO, RMT INSTRUCTOR Introduction q 3% of the total body weight. q includes the brain, spinal cord, and a complex of network nerves. q FUNCTIONS: SENSORY INPUT- gathers information to monitor changes occurring inside and outside of the...

The Nervous System JESSIAH JOY E. SEGISMUNDO, RMT INSTRUCTOR Introduction q 3% of the total body weight. q includes the brain, spinal cord, and a complex of network nerves. q FUNCTIONS: SENSORY INPUT- gathers information to monitor changes occurring inside and outside of the body. INTEGRATION- to process and interpret sensory input to decide if action is needed. MOTOR OUTPUT- response to integrated stimuli and this response activates muscles and glands. JJES, RMT Classifications of Nervous system NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM BRAIN SPINAL CORD MOTOR DIVISION SENSORY DIVISION SOMATIC NS AUTONOMIC NS VOLUNTARY MOVEMENT VIA INVOLUNTARY MOVEMENT SKELETAL SYSTEM SYMPATHETIC PARASYMPATHETIC “Flight-or-fight” response - maintenance JJES, RMT Classifications of Nervous system JJES, RMT Nervous tissues PRESENT IN BOTH CNS AND PNS GLIAL CELL- provides a framework of tissue that supports the neurons and their activities. NEURONS- the more functionally important of the two, in terms of the communicative function of the nervous system. SUPPORT CELLS (NEUROGLIA OR GLIA) ASTROCYTES- a subtype of glial cells that is abundant, star-shaped cells Braces neurons Form barrier between capillaries and neurons Control the chemical environment of the brain (CNS) JJES, RMT Nervous tissues SUPPORTS CELLS: MICROGLIA(CNS)- Spider-like phagocytes They remove damaged neurons and infections and are important for maintaining the health of the CNS. EPENDYMAL CELLS (CNS)- Line cavities of the brain and spinal cord Circulates the Cerebrospinal Fluid (CSF) OLIGODENDROCYTES (CNS)- Produce myelin sheath around nerve fibers in the central nervous system. JJES, RMT JJES, RMT Neurons Possess electrical excitability- the ability to respond to a stimulus and convert it into an action potential. Responsible for the computation and communication that the nervous system provides. Electrically active and release chemical signals to target cells Neurons are important, but without glial support, they would not be able to perform their function. JJES, RMT Anatomy of neuron SOMA- aka cell body or perikaryom, contains a nucleus surrounded by a cytoplasm that includes typical cellular organelles such as the lysosomes, mitochondria, and Golgi complex. DENDRITES- receiving or input portion of the neuron; usually short, tapering, and highly branched. AXON- responsible for generating and transmitting impulses typically away from the cell body. propagates nerve impulse toward the other neuron, a muscle fiber, or a gland cell. Wrapped by an insulating substance called myelin which is made from glial cells. JJES, RMT Anatomy of neuron MYELIN- an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. allows electrical impulses to transmit quickly and efficiently along the nerve cells. NODE OF RANVIER- Gaps in the myelin sheath, appear at intervals along the axon. AXON SEGMENT- wrapped in a myelin sheath. AXON TERMINAL- end of axon where there are usually several branches extending toward the target cell, each of which ends in an enlargement called a synaptic bulb- These bulbs are what make the connection with the target cell at the synapse- The junction between two neurons where information is transmitted from one neuron to another JJES, RMT JJES, RMT Classifications of Neuron STRUCTURAL CLASSIFICATION: Multipolar neurons- usually have several dendrites and one axon. Most neurons in the brain and spinal cord are of this type, as well as the motor neurons. Bipolar neurons- have one main dendrite and one axon. It is found in the retina of the eye, the inner ear, and the olfactory (olfact = to smell) area of the brain. Unipolar neurons- have dendrites ,one that are fused together to form a continuous process that emerges from the cell body. The neurons are appropriately called psuedounipolar neurons because they begin in the embryo as bipolar neurons. JJES, RMT Structural Classification of neuron JJES, RMT Classifications of Neuron FUNCTIONAL CLASSIFICATION: Sensory or afferent neurons- either contain sensory receptors at their distal ends or are located just after sensory receptors that are separate cells. most are unipolar in structure. Motor or efferent neurons- convey action potentials away from the CNS to effectors (muscles and glands) in the periphery (PNS) through cranial or spinal nerves. Multipolar in structure Interneurons or association neurons- mainly located within the CNS between sensory and motor neurons; integrate (process) incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate neurons. Multipolar in structure JJES, RMT  Bundles of axons differ depending on the location TERMINOLOGIES USED: TRACT- when it is located in the Central Nervous System. NERVE- when it is located in the Peripheral Nervous System. JJES, RMT How neurons function IRRITABILITY- an ability to respond to stimuli CONDUCTIVITY- an ability to transmit an impulse. JJES, RMT  Central Nervous System Develops from the embryonic neural tube- becomes the brain and spinal cord The opening of the neural tube becomes the ventricles. Consists of the brain and spinal cord. JJES, RMT The brain It lies within the skull and is shaped like a mushroom CONSISTS OF FOUR (4) PRINCIPAL PARTS: The brain stem- continuous with the spinal cord and consists of the medulla oblongata, pons, and midbrain Cerebrum- largest part of the brain Cerebellum- supported on the diencephalon and brain stem; posterior to the brain stem Diencephalon- superior to the brain stem which consists of the thalamus, hypothalamus and epithalamus. The brain weighs approximately 1.3 to 1.4kg JJES, RMT The brain JJES, RMT The brain JJES, RMT Protective coverings of the brain CRANIAL MENINGES- together with the cranium, surrounds and protects the brain. Continuous with the spinal meninges, have the same basic structure, and bear the same names: Dura mater- outer Arachnoid mater- middle Pia mater- inner TWO (2) TYPES OF MATTER IN BRAIN: GRAY MATTER- Receives and stores impulses. Cell bodies of neurons and neuroglia are in the gray matter; the regions with many cell bodies and dendrites WHITE MATTER- carries impulses to and from gray matter. It consists of the nerve fibers (axons). The regions with many axons. JJES, RMT Gray matter vs. white matter JJES, RMT Major parts (regions) of the brain CEREBRUM CEREBRAL HEMISPHERES Paired (left and right) superior parts of the brain Includes more than half of the brain The surface is made up of: Gyri or gyrus- ridges between the sulci or sulcus Sulci or Sulcus- shallow grooves that surrounds the gyrus Each hemisphere further subdivides into lobes by fissures, such as: Frontal lobe Parietal lobe Occipital lobe Temporal lobe FISSURES- deep grooves that divide cerebrum into lobes. JJES, RMT JJES, RMT Specialized areas of the cerebrum SOMATIC SENSORY AREA- aka somatosensory area; receives impulses from the body’s sensory receptors. Receives nerve impulses for touch, pressure, vibration, itch, tickle, temperature (coldness and warmth), pain, and proprioception (joint and muscle position) and is involved in the perception of these somatic sensations. PRIMARY MOTOR AREA- located in the precentral gyrus of the frontal lobe, sends impulses to the skeletal muscles. BROCHA’S SPEECH AREA- located in the frontal lobe close to the lateral cerebral sulcus that is linked to speech production. JJES, RMT JJES, RMT Specialized areas of the cerebrum CEREBRAL AREAS INVOLVED IN SPECIAL SENSES: PRIMARY VISUAL AREA- receives visual information and is involved in visual perception. PRIMARY AUDITORY AREA- receives information for sound and is involved in auditory perception. PRIMARY GUSTATORY AREA- receives impulses for taste and is involved in gustatory perception and taste discrimination. PRIMARY OLFACTORY AREA- receives impulses for smell and is involved in olfactory perception. JJES, RMT JJES, RMT Major parts (regions) of the brain DIENCEPHALON Sits on the top of the brain stem Enclosed by cerebral hemispheres. Acts as a primary relay and processing center for sensory information and autonomic control. Made up of three (3) parts: Thalamus Hypothalamus Epithalamus JJES, RMT Thalamus Surrounds the third ventricle. The relay station for sensory impulses. All information from your body's senses (except smell) must be processed through your thalamus before being sent to your brain's cerebral cortex for interpretation. Transfers impulses to the correct part of the cortex for localization and interpretation. Also plays a role in sleep, wakefulness, consciousness, learning, and memory. JJES, RMT Hypothalamus Located under the thalamus. Controls and integrates activities of the autonomic nervous system. Helps regulate body temperature. Controls water balance Regulates metabolism The hypothalamus is an important part of the limbic system (regulates emotional and behavioral patterns). Produces hormones, including releasing hormones, inhibiting hormones, oxytocin, and antidiuretic hormone (ADH) JJES, RMT Hypothalamus The pituitary gland- aka hypophysis, is attached to the hypothalamus which acts as your body’s ”Master gland” that regulates growth, metabolism, and reproduction through the hormones that it produces. JJES, RMT Epithalamus Forms the roof of the third ventricle. Consists of the pineal gland that secretes melatonin and habenular nuclei. Also connects the limbic system to other parts of the brain. JJES, RMT Major parts (regions) of the brain BRAIN STEM Attached to the spinal cord. Regulates vital cardiac and respiratory functions and acts as a vehicle for sensory information. Associated with vision, hearing, motor control, sleep, and wake-up cycles, alertness, and temperature regulations. COMPOSED OF THREE (3) PARTS: Midbrain Pons Medulla oblongata JJES, RMT Midbrain Contains sensory and motor tracts. COLLICULUS- located at the top of the midbrain, consists of two (2) pairs of bulging, layered bundles of neurons called: Superior colliculi- coordinate movements of head, eyes, and trunk in response to visual stimuli. Inferior colliculi- coordinate movements of head, eyes, and trunk in response to auditory stimuli. JJES, RMT Pons Contains sensory and motor tracts. The bulging part of the brain stem Helps regulate breathing together with the medulla. JJES, RMT Medulla oblongata The lowest part of the brainstem; is considered the connection between the brainstem and spinal cord. Contains sensory (ascending) and motor (descending) tracts. Contains important control centers: Heart rate control Blood pressure regulation Breathing Swallowing Vomiting JJES, RMT Major parts (regions) of the brain CEREBELLUM also called “little brain” Coordinates contraction of skeletal smooth muscle Regulates posture and balance May have a role in cognition and language processing. Has two lateral hemispheres with convoluted surfaces JJES, RMT JJES, RMT Cranial nerves Each cranial nerve has both a number, designated by a Roman numeral, and a name. The numbers indicate the order, from anterior to posterior, in which the nerves arise from the brain. The names designate a nerve’s distribution or function. Three cranial nerves (I, II, and VIII) carry axons of sensory neurons and thus are called special sensory nerves. Five cranial nerves (III, IV, VI, XI, and XII) are classified as motor nerves because they contain only axons of motor neurons as they leave the brain stem. The remaining four cranial nerves (V, VII, IX, and X) are mixed nerves—they contain axons of both sensory neurons entering the brain stem and motor neurons leaving the brain stem JJES, RMT JJES, RMT JJES, RMT JJES, RMT Protection of the CNS Scalp and skin Skull and vertebral column Meninges Cerebrospinal fluid (CSF) Blood Brain Barrier (BBB) JJES, RMT Meninges Protect and anchor your brain and provide a support system for blood vessels, nerves, lymphatics, and the cerebrospinal fluid that surrounds your central nervous system. THREE (3) LAYERS: DURA MATER- The most superficial of the three spinal meninges is a thick strong layer composed of dense, irregular connective tissue. ARACHNOID MATER- the middle layer of meningeal membranes, thin, web-like projections, avascular covering comprised of cells, and thin, loosely arranged collagen and elastic fibers. PIA MATER- this innermost meninx is a thin transparent connective tissue layer that adheres to the surface of the spinal cord and brain. JJES, RMT Cerebrospinal Fluid A clear, colorless liquid composed primarily of water that protects the brain and spinal cord from chemical and physical injuries. CSF continuously circulates through the cavities in the brain and spinal cord and around the brain and spinal cord in the subarachnoid space (space between arachnoid mater and pia mater) Total volume in adults: 80 to 150 mL Contains a small amount of glucose, proteins, lactic acid, urea, cations (Na+, K+, Ca2+, Mg2+) and anions (Cl- and HCO3-), and some WBCs. Secreted by choroid plexus. JJES, RMT Blood-Brain Barrier Excludes many potentially harmful substances ALLOWS THE PASSAGE OF: Water-soluble substances such as glucose by active transport. Other substances such as creatinine, urea, and most ions but very slowly. DOES NOT ALLOW THE PASSAGE OF: Proteins and most antibiotic drugs SUBSTANCES THAT CAN PASS FREELY IN BBB: Oxygen Carbon dioxide Alcohol Most anesthetic agents Trauma, certain toxins, and inflammation can cause a breakdown of the blood–brain barrier. JJES, RMT Spinal cord In adults, Extends from the medulla oblongata, the inferior part of the brain, to the superior border of the second lumbar vertebra. Below the T12 is the cauda equina- a collection of spinal nerves. Enlargements occur in the cervical and lumbar regions. JJES, RMT Anatomy of Spinal Cord EXTERIOR WHITE MATER- sometimes called superficial tissue, it conduct, process, and send nerve signals up and down the spinal cord. INTERIOR GRAY MATER- contains cell bodies that are responsible for receiving information that must travel to the brain and send information to elicit responses in the body. The information is highly organized in the Dorsal (posterior) and Anterior (ventral) horns. CENTRAL CANAL- filled with cerebrospinal fluid MENINGES- covers and protects the spinal cord NERVES- leave at the level of each vertebrae JJES, RMT Anatomy of Spinal Cord DORSAL ROOT- associated with dorsal root ganglia; collections of cell bodies outside the central nervous system VENTRAL ROOT- contains axons of motor neurons, which conduct nerve impulses from CNS to the effectors (muscles and glands) JJES, RMT Peripheral Nervous System Contains the nerves and ganglia outside the CNS Nerves = bindles of neurons Neuron fibers are bundled by connective tissues. FUNCTIONAL CLASSIFICATION OF THE PNS: SENSORY (AFFERENT) DIVISION- nerve fibers carry information TO the CNS JJES, RMT Peripheral Nervous System MOTOR (EFFERENT) DIVISION- nerve impulses that carry AWAY FROM the CNS TWO (2) SUBDIVISIONS: Somatic NS- voluntary Autonomic NS- involuntary JJES, RMT Somatic NS vs. Autonomic NS SOMATIC NERVOUS SYSTEM: Carries information directly from somatic senses and special senses. Voluntary control. Effectors: skeletal muscle Resposes: contraction of the skeletal muscle AUTONOMIC NERVOUS SYSTEM: Carries information mainly from interoceptors and some from somatic and special senses Involuntary control Effectors: smooth muscle, cardiac muscle, and glands Responses: contraction or relaxation of smooth muscle; inc. or dec. force of contraction of cardiac muscle, inc. or dec. secretion of glands. JJES, RMT Autonomic Nervous System TWO (2) SUBDIVISIONS: 1. SYMPATHETIC- “fight-or-flight” Response to unusual stimulus Takes over to increase activities It is remembered as the “E” division = exercise, excitement, emergency, and embarrassment. 2. PARASYMPATHETIC a network of nerves that relaxes your body after periods of stress or danger. Conserves energy Maintains daily necessary body functions It is remembered as the ”D” division – digestion, defacation, and diuresis. JJES, RMT Special Senses JJES, RMT Olfaction Sense of smell detects and discriminates odors as well as social cues which influence our innate responses. Human has the ability to recognize about 10,000 different odors probably depending on patterns of activity in the brain and arise from the activation of many different combination of olfactory receptors. ANATOMY OF OLFACTORY RECEPTORS: Olfactory epithelium- occupies the superior part of the nasal cavity. Consists of three (3) kinds of cells: olfactory receptors, basal cells, and supporting cells. Olfactory (Bowman’s) glands- support the olfactory epithelium which produces mucus that is carried to the surface of the epithelium by ducts. JJES, RMT Olfaction Olfactory receptors- are the first-order neurons of the olfactory pathway. Each receptor is a bipolar neuron. Capable of binding odor molecules and plays a central role in the sense of smell. Olfactory hairs- part of olfactory receptors that respond to inhaled chemicals. Supporting cells- provide physical support, nourishment, and electrical insulation for the olfactory receptors, and help detoxify chemicals that come in contact with the olfactory epithelium.\ Basal cells- stem cells located between the bases of supporting cells. Continually dividing to produce more olfactory receptors which live only a month or so before being replaced. JJES, RMT Gustation Sense of taste Only five (5) primary tastes can be distinguished: sour, sweet, bitter, salty, and umami. Umami taste- more recently discovered and is described as “meaty” or “savory”. Chemicals that stimulate gustatory receptor cells are known as tastants. ANATOMY OF TASTE BUDS AND PAPILLAE: Taste buds- an oval body consisting of three (3) kinds of cells: supporting cells, gustatory receptor cells, and basal cells. Papillae- an area where tastebuds are found, which increases the surface area and provides a rough texture to the upper surface of the tongue. JJES, RMT Gustation THREE (3) TYPES OF PAPILLAE: Vallate (Circumvallate) papillae- form an inverted V-shaped row at the back of the tongue. Each of these papillae houses 100– 300 taste buds. Fungiform papillae- are mushroom-shaped elevations scattered over the entire surface of the tongue that contain about five taste buds each. Foliate papillae- are located in small trenches on the lateral margins of the tongue, but most of their taste buds degenerate in early childhood. JJES, RMT Vision Act of seeing More than half the sensory receptors in the human body are located in the eyes, and a large part of the cerebral cortex is devoted to processing visual information. ACCESSORY STRUCTURES OF THE EYE: EYELIDS (UPPER AND LOWER)- shades the eye during sleep, protects the eye from excessive light and foreign objects, and spreads lubricating secretions over the eyeballs. Upper eyelid is move movable than the lower. EYELASHES AND EYEBROWS- the eyelashes which project from the border of each eyelid and the eyebrows, which arch transversely above the upper eyelids, helps protect the eyeballs from foreign objects, perspiration, and the direct rays of the sun. JJES, RMT Vision LACRIMAL APPARATUS- a group of EXTRINSIC EYE MUSCLES- The eyes sit structures that produces and drains in the bony depressions of the skull called lacrimal fluid or tears. the orbits- which help protect the eyes, Lacrimal glands- secretes lacrimal stabilize them in three-dimensional fluid which drains into 6-12 excretory space, and anchor them to the muscles lacrimal ducts that empty tears onto that produce their essential movements. the surface of the conjunctiva of the Six extrinsic eye muscles move each eye: upper lid. the superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, and inferior oblique JJES, RMT Vision EYEBALLS: VASCULAR TUNIC- aka uvea; middle Adult eyeball measures about 2.5cm in layer of the eyeball. It is composed of diameter. three (3) layers: choroid, ciliary body, and iris. THREE (3) LAYERS: CHOROID- highly vascularized; lined FIBROUS TUNIC- the superficial layer of the eyeball and consists of the anterior most f the internal surface of sclera. cornea and posterior sclera. CILIARY BODY- produces fluids in the Cornea- a transparent coat that eye. covers the colored iris; helps focus IRIS- the colored portion of the light onto the retina. eyeball, is shaped like a flattened Sclera- the “white” of the eye, a layer donut; A principal function of the iris is of dense connective tissue made up to regulate the amount of light mostly of collagen fibers and fibroblasts; covers the entire eyeball entering the eyeball through the pupil- except the cornea. hole in the center of iris. JJES, RMT Vision RETINA- the third and inner layer of the eyeball; consists of a pigmented layer of a neural layer. The pigmented layer is a sheet of melanin- containing epithelial cells located between the choroid and the neural part of the retina. LENS- Behind the pupil and iris, within the cavity of the eyeball, is the lens. JJES, RMT Auditory Hearing- is the ability to perceive sounds. Auditory receptors are located in the inner ear and identify loud, soft, high, low near, and far noises in the environment. ANATOMY OF THE EAR: EXTERNAL (OUTER) EAR- consists of the auricle, external auditory canal, and eardrum. AURICLE- aka pinna; a flap of elastic cartilage shaped like the flared end of a trumpet and covered by skin. EXTERNAL AUDITORY- lies in the temporal bone and leads to the eardrum EARDRUM- is a thin, semitransparent partition between the external auditory canal and middle ear. JJES, RMT Auditory MIDDLE EAR- connect the sound waves from the external environment and transfer them to the inner ear for auditory transduction. The auditory ossicles (malleus, incus, and stapes) play a key role in this function. Malleus- attaches to the internal surface of the tympanic membrane Incus- the middle bone in the series, articulates with the head of the stapes. Stapes- fits into the oval window; amplify sound vibrations. JJES, RMT Auditory INTERNAL (INNER) EAR- The internal (inner) ear is also called the labyrinth because of its complicated series of canals. TWO (2) MAIN DIVISIONS: Bony labyrinth- The bony labyrinth inside the petrous portion of the temporal bone houses the sense organs of hearing and balance. Membranous labyrinth- houses the receptors for hearing and balance. JJES, RMT Thank you! 🧡 JJES, RMT