Anatomy: The Nervous System - Lecture 3 (PDF)

The Nervous System A system that controls and coordinating all activities of the body. Nervous system is made up of:- Nerve cells or Neurons. Neuroglia. Loose connective tissue.  For Reading Functions of the Nervous System The nervous sys...

The Nervous System A system that controls and coordinating all activities of the body. Nervous system is made up of:- Nerve cells or Neurons. Neuroglia. Loose connective tissue.  For Reading Functions of the Nervous System The nervous system has three main functions: 1. Gathering sensory input. 2. Integrating data. 3. Forming motor output. Divisions of Nervous System  Central nervous system (CNS) consist of : Brain Spinal cord Peripheral nervous system (PNS)consist of : Cranial nerve spinal nerves autonomic nervous system  Protection of the central nervous system Skull ,vertebral column Meninges Cerebrospinal fluid  Protection of the Brain and spinal cord Skull and vertebral column Meninges Cerebrospinal fluid (Watery cushion ) Blood-brain barrier Meninges  Meninges Membranes surrounding the brain and spinal cord Dura Mater - outer Strong layer composed of two fibrous connective tissue layers. The two layers separate in certain areas and form dural sinuses. Arachnoid Mater - middle The middle layer, which forms a loose membrane It is separated from the dura mater by the subdural space and from the pia mater by a wide subarachnoid space filled with CSF and large blood vessels Arachnoid villi protrude superiorly and permit CSF to be absorbed into venous blood Pia Mater - inner Internal fine fibrous connective tissue layers with many minute blood vessels Adheres to the surface of the brain and dipping into each fissure  Meningeal spaces Subdural space: Area between arachnoid mater and dura mater. Subarachnoid space: Area between arachnoid mater and pia mater. Filled with CSF Epidural space: Area between the dura mater and vertebral wall, containing fat and small blood vessels.  Cerebrospinal Fluid · Watery solution Similar to blood plasma. · Formed by the choroid plexus. · Forms a watery cushion to protect the brain and spinal cord. · Circulated in arachnoid space, ventricles, and central canal of the spinal cord.  Cerebrospinal Fluid (CSF) Functions:- – Gives resistance to the CNS organs. – Protects the CNS from blows and other trauma. – Nourishes the brain and carries chemical signals.  Brain is divided into three parts : Forebrain include: 1. Cerebrum 2. Diencephalon Midbrain Hindbrain consist of : 3. pons 4. medulla oblongata 5. cerebellum.  Cerebrum Is the largest part of the brain Consist of gray matter outer and white matter inner. consist of two cerebral hemispheres connect by white matter called corpus callosum. Each hemisphere composed of four lobes -Frontal -Parietal -Temporal -occipital  Each lobe separate from other by sulcus The surface of the brain include sulci and gyri. Name of the main sulci in the brain: Central sulcus Lateral sulcus Parietooccipital sulcus  For Reading Function of the lobes Frontal lobe responsible for motor and intellectual and personality. Pareital lobe for sensation Temporal lobe for hearing and memory Occipital lobe for vision For Reading  Diencephalon · Sits on top of the brain stem. · Enclosed by the cerebral hemispheres. Subdivided into 4 parts: – Thalamus – Hypothalamus – Subthalamus – Epithalamus  Brain Stem · Directly attaches to the brain and spinal cord. · It consists of nerve fibers and nerve cells. · Parts of the brain stem. · Midbrain · Pons · Medulla oblongata  For Reading Brainstem Midbrain – Integral part of auditory pathways in CNS – control involuntary functions Pons – Below the mid brain – Sleep and respiratory centers (regulation of rate & depth of breathing) – Control of consciousness – Control level of concentration Medulla oblongata or medulla – has : – Cardiac center: regulates heart rate – Vasomotor center : blood vessel diameter – Respiration center : coughing, and sneezing – Control swallowing & vomiting  Cerebellum Lies posterior to the pons and the medulla oblongata. It consists of two cerebellar hemispheres connected by the vermis. Functions of the cerebellum Co-ordination of movement control of posture Equilibrium  For Reading Functions of the cerebellum Co-ordination of movement control of posture Equilibrium  Ventricles and Cerebrospinal fluid (CSF) Four connecting cavities within the cerebrum and brain stem and continuous with the central canal of spinal cord. Filled with CSF. The Brain Ventricles 1. Right & left lateral ventricles- In cerebral hemisphere 2. 3rd ventricle - cavity of diencephalon. 3. 4th ventricle - cavity of brainstem. The ventricular system  Ventricles of the Brain Lateral ventricles – located in cerebral hemispheres. Horseshoe-shaped from bending of the cerebral hemispheres. Third ventricle – lies in diencephalon Connected with lateral ventricles by interventricular foramen.  Ventricles of the Brain Cerebral aqueduct – connects 3rd and 4th ventricles. Fourth ventricle – lies in hindbrain. – Connects to the central canal of the spinal cord.  Spinal Cord · It is long cylindrical part of lower part of brain. · It is present in vertebral canal. · Extends from C1-L1 vertebra. · It passes through foramen magnum. · It is the continuation of medulla oblongata. · Lower part of spinal cord is called conus medullaris. Gross Anatomy of the Spinal Cord  Dimensions of spinal cord Length is 42-45 cm. Two Enlargements occur in the cervical and lumbar regions.  Spinal Cord Anatomy · Meninges cover the spinal cord. · There are 31 pairs of spinal nerves. Present in the intervertebral foramina. · The spinal nerves has two roots:- · Dorsal root · Ventral root  Cross section of Spinal Cord · Exterior white mater – conduction tracts · Internal gray matter - mostly cell bodies · Dorsal (posterior) horns · Anterior (ventral) horns  Cross section of Spinal Cord · Central canal:- filled with cerebrospinal fluid Figure 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.53c  Peripheral Nervous System 1- Spinal Nerves Spinal nerves arise from the spinal cord and attach to it by anterior root which is motor and posterior root which is sensory connect together form trunk of the spinal nerve mix then give two rami anterior and posterior also mix 31 pairs spinal nerve 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal Spinal Nerves  2- Cranial Nerves Cranial nerves Origin of the Cranial Nerves There are twelve cranial nerves in total. - The olfactory nerve (CN I) and optic nerve (CN II) originate from the cerebrum - Cranial nerves III – XII arise from the brain stem (midbrain, pons or medulla), They can arise from a specific part of the brain stem. - The oculomotor (III) and trochlear (IV) cranial nerves stem from the midbrain - Trigeminal (V), abducent (VI), and facial nerves (VII) vestibulocochlear (VIII) arise in the pons. - The glossopharyngeal (IX) , vagus (X) , accessory (XI) and hypoglossal nerves (XII) are attached to the medulla oblongata.  Cranial Nerves I. Olfactory – Smell (sensory) II. Optic – Vision (sensory) III. Oculomotor – Eye muscles (motor) IV. Trochlear – Eye muscles (motor) V. Trigeminal – Facial (sensory) , chewing muscles (motor)  Cranial Nerves VI. Abducens – Eye muscles (motor) I. Facial – Taste (sensory), facial muscles (motor) II. Vestibulocochlear – Balance and hearing (sensory) III. Glossopharyngeal – Taste (sensory), swallowing (motor)  Cranial Nerves X. Vagus – Sensory and motor neurons that affect sweating, peristalsis, heart rate, opening the larynx for speech and breathing. – Has branches in the ear canal – cotton swab cough. I. Accessory Nerve – Neck and upper back muscles (motor) II. Hypoglossal – Tongue (motor)  For Reading Sympathetic Brai SYMPATHETI C n Dilates pupil Stimulates Salivar salivation y Relaxes glands “ Fight or flight” response Spinal bronchi cord Lung Increases heart rate and blood s pressure,and respiratory rate. Accelerates heartbeat Hear Bronchodilatation ,decrease t Inhibits Stomac intestinal motility,urination activity h.sweating Pancrea s Stimulates Live glucose r Secretion of Adren adrenaline, al gland nonadrenaline Kidne Relaxes y bladder Sympatheti Stimulates c ejaculation ganglia in male  For Reading Parasympathetic Brai n Parasympathe tic Dilates pupil Stimulates Salivar salivation y occur at Rest Relaxes bronchi glands Spinal Lowers rate , breathing rate cord Lung s Stimulate intestinal motility Accelerates heartbeat Hea ,increase the secretion of rt gland Inhibits Stomac activity h Bronchoconstriction Pancre ,vasodiltation. Stimulates as Live glucose r Secretion of Adren adrenaline, al gland nonadrenaline Kidne Relaxes y bladder Sympathet Stimulates ic ejaculation ganglia in male  The Special Senses Special senses 1. Taste 2. Smell 3. Sight 4. Hearing 5. Touch General senses of touch 6. Temperature 7. Pressure 8. Pain  Taste Buds Taste buds are tiny sensory organs on your tongue that send taste messages to your brain. These organs have nerve endings that have chemical reactions to the food you eat. Taste buds are found in papillae of the tongue mucosa Fungiform and circumvallate papillae contain taste buds. The adult human tongue contains between 2,000 and 8,000 taste buds  Sense of Smell The organ of smell is the olfactory epithelium, which covers the superior nasal concha Olfactory receptor cells are bipolar neurons with radiating olfactory cilia  Vision 70% of all sensory receptors are in the eye Most of the eye is protected by a cushion of fat and the bony orbit Accessory structures include eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles Structure of the Eyeball  1. Fibrous Tunic Forms the outermost coat of the eye and is composed of: – Opaque sclera (posteriorly) – Clear cornea (anteriorly) The sclera protects the eye and anchors extrinsic muscles The cornea lets light enter the eye  2. Vascular Tunic (Uvea) Choroid region – Supplies blood to all eye tunics Ciliary body - Composed of smooth muscles (ciliary muscles) that anchor the lens in place Iris – The colored part of the eye Pupil – central opening of the iris – Regulates the amount of light entering the eye  3. Sensory Tunic: Retina A delicate two-layered membrane Neural layer, which contains photoreceptors that transduce light energy 1. Rods: Respond to dim light 2. Cones: Respond to bright light and have high-acuity color vision  Eye Chambers and Fluids Eyeball is composed of two chambers: – Anterior: between the cornea and the iris – Posterior: between the iris and the lens  The Ear: Hearing and Balance The three parts of the ear are the inner, outer, and middle ear The outer and middle ear are involved with hearing The inner ear functions in both hearing and equilibrium  Outer Ear The auricle (pinna) External auditory canal – Short, curved tube filled with ceruminous glands Tympanic membrane (eardrum) – Thin connective tissue membrane that vibrates in response to sound – Transfers sound to the middle ear ossicles – Boundary between outer and middle ears  Middle Ear (Tympanic Cavity) A small, air-filled, mucosa-lined cavity Eustachian tube – connects the middle ear to the nasopharynx – Equalizes pressure in the middle ear cavity with the external air pressure  Ear Ossicles The tympanic cavity contains three small bones: the malleus, incus, and stapes – Transmit vibratory motion of the eardrum to the oval window  Inner Ear Bony labyrinth – Contains the vestibule, the cochlea, and the semicircular canals – Filled with perilymph Membranous labyrinth – Series of membranous sacs within the bony labyrinth – Filled with a potassium-rich fluid  For Reading How we hear sounds. From ear to neurons and brain Sound waves enter the outer ear and travel through the ear canal, which leads to the eardrum. The eardrum vibrates from the incoming sound waves and sends these vibrations to three tiny bones in the middle ear. The bones in the middle ear amplify the sound vibrations and send them to the cochlea, a snail-shaped structure filled with fluid. Once the vibrations cause the fluid inside the cochlea to ripple, they make hair cells move up and down. When that happens, chemicals rush into the cells, creating an electrical signal. The auditory nerve carries this electrical signal to the brain, which turns it into a sound that we recognize.