Nat Sci 3 Human Anatomy and Physiology PDF

NAT SCI 3- HUMAN ANATOMY AND PHYSIOLOGY THE NERVOUS SYSTEM OCTOBER 2024 ○ Action potentials/ Nerve impulses...

NAT SCI 3- HUMAN ANATOMY AND PHYSIOLOGY THE NERVOUS SYSTEM OCTOBER 2024 ○ Action potentials/ Nerve impulses Language of neurons OUTLINE: Electrical signals carried along neurons I. GENERAL STRUCTURE AND FUNCTION to the brain a. General Structures b. Functions of the Nervous System Depolarization: Voltage-gated sodium II. TYPES AND STRUCTURE (Na+) channel opening in the nerve cell a. Central Nervous System membrane. Inside is more positive than b. Peripheral Nervous System the outside of the membrane. III. DIVISION OF THE NERVOUS SYSTEM Repolarization: Voltage-gated a. Somatic Nervous System potassium (K+) channels open in the b. Autonomic Nervous System membrane. Negatively charged inside, c. Enteric Nervous System IV. SENSES while being positively charged outside. a. Sensation Hyperpolarization: Membrane potential b. Sensory Receptors becomes more negative than its start. c. General Senses d. Pain e. Olfaction f. Taste g. Vision h. Hearing and Balance i. Balance V. REFERENCES GENERAL STRUCTURE AND FUNCTION Nervous System - regulates and coordinates functions of the body to maintain homeostasis. It is a communication system, receiving signals from and sending commands to different areas of the body. It helps to coordinate the body functions to maintain Nerves - send electrical signals for sensations, movement, homeostasis. and control of body functions. ○ Fibers of sensory and motor neurons General Structures Glial Cells - supports the neurons and their activities. Brain - receives and interprets all sensory information, stores memory, and controls movement. Functions of the Nervous System ○ Perception and processing of sensory stimuli 1. Maintaining homeostasis ○ Execution of voluntary responses - Depends on the nervous system’s ability to detect, ○ Regulation of homeostatic mechanisms interpret, and respond to changes in internal and Spinal Cord - contains nerve bundles and cells that carry external conditions. messages from your brain to the rest of your body. - Can stimulate or inhibit the activities of other ○ Initiation of reflexes systems to help maintain a constant internal ○ Pathways for sensory and motor functions environment. between periphery and brain 2. Receiving sensory input Neurons - excitable cells of the nervous system - Sensory receptors monitor numerous external and internal stimuli. - Vision, hearing, taste, smell, touch, pain, body position, and temperature. - Blood pH, blood gasses, and blood pressure, are processed at a subconscious level. 3. Integrating information - The brain and spinal cord are the major organs for processing sensory input and initiating responses 4. Controlling muscles and glands - Skeletal muscles contract when stimulated by the nervous system. - Controls the major movements of the body. - Also participates in controlling cardiac muscle, smooth muscle, and many glands. 5. Establishing and maintaining mental activity - Center of mental activity, including consciousness, memory, and thinking. ○ Structure TYPES AND STRUCTURE Cell body/Soma- contains the nucleus that dictates the cell’s function The nervous system is divided into two major regions: Dendrites- short, branching extensions ○ Central Nervous System (CNS) - consists of the of the cell that usually receive brain and the spinal cord. information from other neurons or from ○ Peripheral Nervous System (PNS) - consists of sensory receptors and transmit the all the nervous tissue outside the CNS, including information toward the neuron cell body. nerves and ganglia. Axon-single long cell process that either conduct action potentials towards the Central Nervous System CNS (sensory neurons) or away from Spinal Cord the CNS (motor neurons) ○ It extends from the foramen magnum at the base ○ Receive stimuli, transmit signals to other neurons of the skull to the second lumbar vertebra. or effector organs, and conduct action potentials. Group 5- Aguilos, Casimpan, Garcia and Osit Page 1 of 5  NAT SCI 3- HUMAN ANATOMY AND PHYSIOLOGY THE NERVOUS SYSTEM OCTOBER 2024 Hypothalamus - a collection of nuclei ○ Spinal nerves communicate between the spinal that are largely involved in regulating cord and the body. homeostasis. It connects the CNS to the ○ Cauda Equina - the inferior end of the spinal cord endocrine system. and the spinal nerves exiting there that resembles Epithalamus - consists of a few small a horse’s tail. nuclei, which are involved in the ○ It consists of a superficial white matter portion and emotional and visceral response to a deep gray matter portion. odors, and the pineal gland. White Matter - tissue consists of Pineal Gland - an endocrine myelinated axons. gland that may influence the In the spinal cord, it has three onset of puberty and may play columns: a role in controlling some long ○ Dorsal (Posterior) term cycles that are influenced Column by the light-dark cycle. ○ Ventral (Anterior) ○ Cerebrum - the largest part of the brain. Column It is divided into left and right ○ Lateral Column hemispheres by a longitudinal fissure. Consists the ascending and Corpus Callosum - provides the major descending tracts. pathway for communication between the ○ Ascending Tract - carry two hemispheres of the cerebral cortex. sensory information up Cerebral Cortex - thin, extensive region to the brain of wrinkled gray matter that is ○ Descending Tract - responsible for the higher functions of carry motor commands the nervous system such as thinking and from the brain. other mental processes. Gray Matter - tissue that is a collection Gyrus (plural: gyri) - numerous of neuron cell bodies and dendrites. folds or ridges of the brain In the spinal cord, it is shaped Sulcus (plural:sulci) - the like the letter H. groove between two gyri. Has three horns: Has four lobes: ○ Posterior Horn ○ Frontal Lobe - ○ Anterior Horn important in the control ○ Lateral Horn of voluntary motor functions, motivation, Brain aggression, mood, and ○ The major regions of the brain are the brainstem, olfactory (smell) the cerebellum, the diencephalon, and the reception. cerebrum. ○ Parietal Lobe - the ○ Brainstem - connects the brain and the spinal principal center for cord. It consists of the medulla oblongata, pons, receiving and and the midbrain, which works together to control consciously perceiving and coordinate messages going in and out of the most sensory brain. information (ex. touch) Medulla Oblongata - located at the ○ Temporal Lobe - is bottom of the brainstem. It is responsible involved in olfactory for autonomic functions (e.g. blood (smell) and auditory pressure, breathing). (hearing) sensations and Pons - responsible for relaying signals plays an important role from the motor cortex to the cerebellum, in memory. medulla oblongata, and thalamus. ○ Occipital Lobe - Midbrain - the smallest region of the functions in receiving brainstem. It helps to control eye and perceiving visual movement and coordination. input. Reticular Formation - group of nuclei Central Sulcus - separates the scattered throughout the brainstem that frontal and parietal lobe regulates important functions such as Lateral Fissure - separates the motor control and consciousness. temporal lobe from the rest of It is a major component of the the cerebrum reticular activating system Protective Structures of the CNS (RAS), which plays an ○ Meninges - these are three connective tissue important role in arousing and membranes that surround and protect the brain maintaining consciousness, and spinal cord. and in regulating the Dura Mater - the most superficial and sleep-wake cycle. thickest of the meninges. ○ Cerebellum - also known as “little brain”. It is Its name comes from the Latin responsible for balance, movement, and for “tough mother” to represent coordination. its physically protective role. ○ Diencephalon - is the connection between the It encloses the entire CNS and cerebrum and the rest of the nervous system the major blood vessels that except for the system associated with olfaction or enter the cranium and vertebral the sense of smell. cavity. Thalamus - the brain’s relay center. It Arachnoid Mater - the middle layer of relays incoming sensory information the meninges. through groups of neurons that project to It is named for its the appropriate region in the cerebral spider-web-like trabeculae, a cortex. delicate strand of connective Group 5- Aguilos, Casimpan, Garcia and Osit Page 2 of 5  NAT SCI 3- HUMAN ANATOMY AND PHYSIOLOGY THE NERVOUS SYSTEM OCTOBER 2024 tissues between the arachnoid and the pia mater. DIVISION OF THE NERVOUS SYSTEM It is a sac-like enclosure around the CNS. Somatic Nervous System Pia Mater - thin fibrous membrane that Controls voluntary movements covers the outer surface of the CNS. transmits action potentials from CNS to skeletal muscles Its name comes from the Latin Voluntary movement occur due to stimulation of neural for “tender mother” suggesting circuits that consist of two motor neurons: upper and lower its gentle covering of the brain. motor neurons ○ Cerebrospinal Fluid (CSF) - bathes the brain and ○ Upper Motor Neurons spinal cord, providing a protective cushion around Cell bodies are in the cerebral the CNS. cortex Choroid Plexus - produces the CSF. Axons form descending tracts ○ Ventricles - open spaces within the brain where that connect to lower motor CSF circulates. neurons ○ Lower Motor Neurons Peripheral Nervous System Cell bodies are in the anterior Ganglia (singular: ganglion) - group of neuron cell bodies. horn of spinal cord gray matter or ○ It forms connections with the different parts of the cranial nerve nuclei brain, allowing them to send signals back and Axons leave the CNS and extend forth. through spinal or cranial nerves ○ Can be categorized as either sensory ganglia or to skeletal muscles. autonomic ganglia. Motor Areas of the Cerebral Cortex Nerves Primary Motor Cortex - Action potentials in this region ○ The nerves of the PNS can be divided into two control voluntary movement of skeletal muscles groups: 12 pairs of cranial nerves and 31 pairs Premotor Area - Motor functions are organized here of spinal nerves. before initiated in the Primary Motor Cortex ○ Cranial Nerves - nerves attached to the brain, Prefrontal Area - Motivation and foresight to initiate which are primarily responsible for the sensory movements as well as regulation of emotional behavior and motor functions of the head and neck. and mood. Each nerve is designated using Roman Descending Tracts numerals from 1 to 12. Direct Lateral Corticospinal - Muscle tone and skilled movements especially of hands Anterior Corticospinal - Muscle tone and movement trunk muscles Indirect Rubrospinal - Movement coordination Retuculospinal - Posture adjustment, especially during movement Vetibulospinal - Posture and balance Tectospinal - Movement in response to visual reflexes Basal Nuclei - Group of functionally related nuclei - Responsible for planning, organizing, and coordinating ○ Spinal Nerves motor movements and posture All the spinal nerves contain axons of - Disorders here cause difficulty in rising and walking and both sensory and somatic motor causes increased muscle tone and exaggerated neurons and thus are called mixed uncontrolled movements at rest nerves. Two Primary Nuclei: They are categorized by the region of Corpus Striatum - found deep within cerebrum the vertebral column from which they Substantia Nigra - dark pigmented cells in the midbrain emerge: Feedback Loops: Cervical (C) - C1 through C8 Stimulatory - facilitates muscle activity especially at the Thoracic (T) - T1 through T12 beginning of a voluntary movement Lumbar (L) - L1 through L5 Inhibitory - facilitates the actions of the stimulatory Sacral (S) - S1 through S5 circuits by inhibiting muscle activity in antagonist Coccygeal (Co) muscles. Also inhibits random movements of the trunk Dermatome - the area of skin supplied and limbs as well as decrease muscle tone when the with sensory innervation by a pair of body, limbs, and head are at rest spinal nerves. Cerebellum Most of the spinal nerves are organized - Attached by cerebellar peduncles to the brainstem into three major plexuses, where - Consists of gray nuclei and white nerve tracts neurons of several spinal nerves come - Involved in maintaining balance, muscle tone, and in together and intermingle. coordinating fine motor movement Three Major Plexuses - Compares motor cortex and sensory information from ○ Cervical Plexus - the moving structures originates from spinal nerves C1 to C4. Autonomic Nervous System ○ Brachial Plexus - Involved in involuntary movements originates from spinal Comprises of motor neurons that carry action potentials from nerves C5 to T1 CNS to the periphery. ○ Lumbosacral Plexus - Innervate smooth and cardiac muscles, as well as glands originates from spinal nerves L1 to S4. Two Neurons: Preganglionic Neuron Group 5- Aguilos, Casimpan, Garcia and Osit Page 3 of 5  NAT SCI 3- HUMAN ANATOMY AND PHYSIOLOGY THE NERVOUS SYSTEM OCTOBER 2024 - All preganglionic neurons of both sympathetic ○ Ruffini Corpuscles: Detect continuous pressure. and parasympathetic division secrete the ○ Pacinian Corpuscles: Detect deep pressure, neurotransmitter acetylochine vibration, and proprioception. Postganglionic Neuron - Most postganglionic neurons of the Pain sympathetic division secrete the Types of Pain Sensations: neurotransmitter norepinephrine ○ Localized pain: Sharp, pricking pain (fast Two Divisions: transmission). Sympathetic Division ○ Diffuse pain: Burning, aching pain (slow - “Fight or Flight” transmission). - prepares the body for physical activity ○ Referred Pain: Pain perceived in a different Parasympathetic Division location than the stimulus, e.g., pain from a heart - “Rest and Digest” attack felt in the left shoulder. - Stimulates involuntary activities of the body at rest Olfaction (Smell) Dual Innervation Olfactory Neurons: Located in the olfactory epithelium, - Organs that receive autonomic neurons have specialized cilia that interact with odorants. innervated by both the sympathetic and Pathways for Olfaction: Action potentials travel from parasympathetic division. olfactory neurons to the olfactory cortex for perception. Enteric Nervous System Taste Consists of plexuses within the wall of the digestive tract Taste Buds: Located on the tongue and other parts of the Enteric Neurons mouth, consisting of epithelial cells and taste cells. - capable of monitoring and controlling the digestive tract Taste Types: Sour, salty, bitter, sweet, and umami (savory). independently of the CNS through local reflexes Neuronal Pathways for Taste: Sensory information is - The enteric interneurons stimulate enteric motor carried by the facial, glossopharyngeal, and vagus nerves to neurons, which stimulate glands to secrete. the brain. Plexuses include: sensory neurons that connect the digestive tract to the Vision CNS; Accessory Structures of the Eye sympathetic and parasympathetic neurons that ○ Eyebrows connect the CNS to the digestive tract; ○ Eyelids enteric neurons, located entirely within the enteric ○ Conjunctiva plexuses. ○ Lacrimal Apparatus ○ Extrinsic Eye Muscles. - CNS control of parasympathetic branches of the vagus Structure of the Eye: nerve and sympathetic nerves (primarily, the splanchnic ○ Fibrous Tunic: Includes the sclera and cornea. nerves) can override the actions of enteric neurons. ○ Vascular Tunic: Includes the choroid, ciliary body, Hence, the ENS is an independent subdivision of the and iris. PNS that is integrated with the ANS ○ Nervous Tunic: The retina, which includes rods and cones for light perception. SENSES Hearing and Balance Anatomy of the Ear Sensation ○ External Ear: Auricle and external auditory canal. General Senses vs. Special Senses: ○ Middle Ear: Tympanic membrane, auditory ○ General senses have receptors distributed ossicles (malleus, incus, stapes). throughout the body and are divided into somatic ○ Inner Ear: Cochlea (for hearing) and vestibular senses (providing information about the body and system (for balance). environment) and visceral senses (providing Hearing Mechanism: information about internal organs, mainly pain and ○ Sound waves travel through the auditory canal to pressure). the tympanic membrane, causing vibrations that ○ Special senses are more localized and include are transferred to the cochlea for sound smell, taste, sight, hearing, and balance. perception. Sensory Receptors Balance Types of Sensory Receptors: Static Equilibrium: Detected by the vestibule. ○ Mechanoreceptors: Respond to mechanical Dynamic Equilibrium: Detected by the semicircular canals. stimuli like bending/stretching. ○ Chemoreceptors: Respond to chemicals, e.g., odor molecules for smell. REFERENCES ○ Photoreceptors: Respond to light (vision). Vanputte, C. L., Regan, J. L., & Russo, A. F. (2019). ○ Thermoreceptors: Respond to temperature Seeley’s Essentials of Anatomy & Physiology (10th ed.). changes. Mcgraw-Hill Education. ○ Nociceptors: Respond to pain stimuli. OpenStax | Free Textbooks Online with No Catch. (n.d.). @Openstax/Os-webview. General Senses https://openstax.org/details/books/anatomy-and-physiolo General Sensory Receptors gy-2e ○ Free Nerve Endings: Respond to painful stimuli, Central nervous system: the brain and spinal cord (for temperature, and movement. parents). (n.d.-b). ○ Merkel Disks: Detect light touch and superficial https://kidshealth.org/en/parents/central-nervous-system pressure..html ○ Hair Follicle Receptors: Detect light touch Thau, L., Reddy, V., & Singh, P. (2022, October 10). associated with hair movement. Anatomy, central nervous system. StatPearls - NCBI ○ Meissner Corpuscles: Provide fine, discriminative Bookshelf. touch. https://www.ncbi.nlm.nih.gov/books/NBK542179/#:~:text Group 5- Aguilos, Casimpan, Garcia and Osit Page 4 of 5  NAT SCI 3- HUMAN ANATOMY AND PHYSIOLOGY THE NERVOUS SYSTEM OCTOBER 2024 =The%20CNS%20includes%20the%20brain,Peripheral %20and%20Central%20Nervous%20Systems). Sternberg, R. J., & Sternberg, K. (2016). Cognitive psychology (7th ed.). Boston, Ma, Usa Cengage Learning Canada. Group 5- Aguilos, Casimpan, Garcia and Osit Page 5 of 5