Nervous System PDF

NERVOUS SYSTEM YOUSRA LIAQAT MIT 2A DIVISIONS OF NERVOUS SYSTEM  Nervous system controls all the activities of the body. It is quicker than other control system in the body, namely endocrine system. Primarily, nervous system is divided into two parts:  1. Central nervous system  2....

NERVOUS SYSTEM YOUSRA LIAQAT MIT 2A DIVISIONS OF NERVOUS SYSTEM  Nervous system controls all the activities of the body. It is quicker than other control system in the body, namely endocrine system. Primarily, nervous system is divided into two parts:  1. Central nervous system  2. Peripheral nervous system CENTRAL NERVOUS SYSTEM  Central nervous system (CNS) includes brain and spinal cord. It is formed by neurons and supporting cells called neuroglia. Structures of brain and spinal cord are arranged in two layers, namely gray matter and white matter.  Brain is situated in the skull. It is continued as spinal cord in the vertebral canal through the foramen magnum of the skull bone. Brain and spinal cord are surrounded by three layers of meninges called the outer dura mater, middle arachnoid mater and inner pia mater.  The space between arachnoid mater and pia mater is known as subarachnoid space. This space is filled with a fluid called cerebrospinal fluid. Brain and spinal cord are actually suspended in the cerebrospinal fluid. Parts of Brain PERIPHERAL NERVOUS SYSTEM  It consists of cranial nerves, arising from brain and spinal nerves, arising from the spinal cord. It is again divided into two subdivisions:  1. Somatic nervous system  2. Autonomic nervous system Continued….. Somatic Nervous System Autonomic Nervous System  Somatic nervous system is  Autonomic nervous system is concerned with somatic functions. concerned with regulation of visceral  or vegetative functions. It includes the nerves supplying the skeletal muscles.  So, it is otherwise called vegetative  or involuntary nervous system. Somatic nervous system is responsible for muscular activities  Autonomic nervous system consists and movements of the body. of two divisions, sympathetic division and parasympathetic division FUNCTIONS OF ALL PARTS OF CENTRAL NERVOUS SYSTEM  Central Nervous System (CNS)  The CNS consists of the brain and spinal cord, serving as the body’s control center. Brain: The brain processes sensory information, makes decisions, and coordinates actions. It consists of different regions, each with specific functions: Cerebrum: Responsible for higher cognitive functions, like reasoning, problem- solving, and planning. It also controls voluntary movement, sensory processing, and language. Cerebellum: Coordinates fine motor movements, balance, and posture. It ensures smooth and precise muscle activity Continued….. Brainstem: Connects the brain to the spinal cord and regulates basic life functions: Midbrain: Controls visual and auditory processing and motor movement. Pons: Assists in regulating breathing and communication between brain parts. Medulla Oblongata: Controls autonomic functions like heart rate, blood pressure, and digestion. Thalamus: Acts as a relay station for sensory information, directing it to the cerebral cortex Continued…  Hypothalamus: Regulates bodily functions, including hunger,thirst, body temperature, and sleep. It links the nervous system to the endocrine system.  Spinal Cord: Connects the brain to the peripheral nervous system, relaying messages between them.  It also coordinates reflexes through spinal reflex arcs, allowing the body to react quickly without direct brain involvement. Peripheral Nervous System (PNS)  The PNS connects the CNS to limbs and organs, facilitating communication between the body and brain. It has two main subdivisions: the somatic nervous system and the autonomic nervous system.  Somatic Nervous System  The somatic nervous system controls voluntary movements and transmits sensory information. Sensory (Afferent) Neurons: Carry information from sensory organs (like skin, eyes, and ears) to the CNS, allowing us to perceive stimuli. Motor (Efferent) Neurons: Transmit signals from the CNS to skeletal muscles, enabling voluntary movements. Autonomic Nervous System (ANS)  The ANS regulates involuntary bodily functions (e.g., heart rate, digestion, and respiratory rate) and has two further subdivisions: Sympathetic Nervous System: Activates the “fight-or-flight” response during stressful situations, increasing heart rate, dilating pupils, and redirecting blood flow to muscles. Parasympathetic Nervous System: Activates the “rest-and-digest” response, slowing heart rate, stimulating digestion, and promoting relaxation. Enteric Nervous System (ENS): Sometimes considered a part of the ANS, it governs the gastrointestinal system, controlling digestion and bowel movements independently of the brain. SUMMARY OF FUNCTIONS Nervous System Part Function Brain (Cerebrum, Cerebellum, Cognitive processing, balance, Brainstem) posture, autonomic functions. Spinal Cord Relay signals; control reflexes Somatic Nervous System Voluntary movement, sensory processing Sympathetic Nervous System “Fight-or-flight” responses during stress. Parasympathetic Nervous System Rest-and-digest” responses for relaxation Enteric Nervous System Manages gastrointestinal functions FUNCTIONS OF CRANIAL SYSTEM  Cranial nerves are a set of twelve paired nerves that originate in the brain and primarily serve the head and neck region, with some also influencing organs in the thorax and abdomen.  Each cranial nerve has unique sensory, motor, or mixed functions.  Here’s a detailed look at each cranial nerve and its functions: Continued…  Olfactory Nerve (Cranial Nerve I) Type: Sensory Function: Responsible for the sense of smell. Pathway: Carries information from the nasal mucosa to the olfactory bulbs in the brain. Clinical Note: Damage to this nerve can lead to anosmia (loss of smell). Continued…  Optic Nerve (Cranial Nerve II) Type: Sensory Function: Responsible for vision. Pathway: Transmits visual information from the retina to the occipital lobe of the brain for processing. Clinical Note: Damage can result in vision loss or blindness. Continued….  Oculomotor Nerve (Cranial Nerve III) Type: Motor Function: Controls most of the eye’s movements, including eyelid elevation, and pupil constriction. Pathway: Innervates four of the six extraocular muscles (superior, medial, inferior recti, and inferior oblique) and the levator palpebrae superioris muscle. Clinical Note: Injury can cause ptosis (drooping eyelid), diplopia (double vision), and pupil dilation. Continued….  Trochlear Nerve (Cranial Nerve IV) Type: Motor Function: Controls the superior oblique muscle, allowing downward and inward eye movement. Pathway: Arises from the midbrain and innervates the superior oblique muscle. Clinical Note: Damage can cause difficulty moving the eye downward and outward, leading to vertical diplopia. Continued….  Trigeminal Nerve (Cranial Nerve V) Type: Mixed (Sensory and Motor) Function: Sensory for the face and motor for the muscles of mastication (chewing). V1 (Ophthalmic): Sensory from the forehead, scalp, and upper eyelids. V2 (Maxillary): Sensory from the cheeks, upper lip, and nasal cavity. V3 (Mandibular): Sensory from the lower lip, chin, and motor for chewing muscles. Pathway: Divides into three branches (ophthalmic, maxillary, and mandibular). Clinical Note: Damage can cause trigeminal neuralgia, a condition of severe facial pain. Continued…  Abducens Nerve (Cranial Nerve VI) Type: Motor Function: Controls the lateral rectus muscle, enabling lateral (outward) eye movement. Pathway: Arises from the pons and innervates the lateral rectus muscle. Clinical Note: Damage can cause the affected eye to turn inward, leading to horizontal diplopia Continued….  Facial Nerve (Cranial Nerve VII) Type: Mixed Function: Controls facial expressions, lacrimation (tear production), salivation, and taste on the anterior two-thirds of the tongue. Pathway: Exits the brainstem and divides into five major branches across the face. Clinical Note: Damage can lead to Bell’s palsy, which causes paralysis of facial muscles on one side. Continued…  Vestibulocochlear Nerve (Cranial Nerve VIII) Type: Sensory Function: Responsible for hearing and balance. Cochlear branch: Transmits sound information. Vestibular branch: Provides information about head position and movement for balance. Pathway: Arises from the inner ear and connects to the brainstem. Clinical Note: Damage can lead to hearing loss, tinnitus (ringing in the ears), and balance issues, such as vertigo. Continued….  Glossopharyngeal Nerve (Cranial Nerve IX) Type: Mixed Function: Controls taste from the posterior one-third of the tongue, monitors blood pressure in the carotid arteries, and plays a role in swallowing. Pathway: Arises from the medulla oblongata and innervates the tongue and pharynx. Clinical Note: Damage can cause loss of taste, difficulty swallowing, and reduced saliva production. Continued….  Vagus Nerve (Cranial Nerve X) Type: Mixed Function: Controls the muscles for voice, swallowing, and regulating heart rate, digestion, and respiratory rate. It’s the main parasympathetic nerve. Pathway: Extends from the medulla and travels widely, affecting the thoracic and abdominal organs. Clinical Note: Damage can cause difficulty swallowing, hoarseness, and autonomic dysfunction affecting the heart and digestive system. Continued….  Accessory Nerve (Cranial Nerve XI) Type: Motor Function: Controls the trapezius and sternocleidomastoid muscles, responsible for shoulder elevation and head rotation. Pathway: Arises from both the medulla and the upper spinal cord, entering the skull before exiting again. Clinical Note: Damage can lead to difficulty in head rotation and shoulder movement, causing shoulder drooping Continued….  Hypoglossal Nerve (Cranial Nerve XII) Type: Motor Function: Controls tongue movements for speech and swallowing. Pathway: Arises from the medulla and innervates muscles of the tongue. Clinical Note: Damage can result in weakness or paralysis of the tongue on one side, causing speech and swallowing difficulties