Introduction to the Nervous System

• The nervous system controls and coordinates all bodily activities

Composition of the Nervous System

• The nervous system comprises nerve cells/neurons, neuroglia, and loose connective tissue

Functions of the Nervous System

• The nervous system gathers sensory input, integrates data, and forms motor output

Classification of the Nervous System

• The central nervous system (CNS) includes the brain and spinal cord
• The peripheral nervous system (PNS) consists of nerves outside the brain and spinal cord

Peripheral Nervous System

• PNS includes cranial nerves, spinal nerves, ganglia, and parts of receptor organs

Central Nervous System

• CNS consists of the brain and spinal cord

Peripheral nervous system

• PNS consists of cranial nerves, spinal nerves, and the autonomic nervous system

Protection of the Central Nervous System

• The CNS is protected by the skull, vertebral column, meninges, and cerebrospinal fluid

Meninges

• Meninges are membranes surrounding the brain and spinal cord

Dura Mater

• The outer dura mater is a strong layer of two fibrous connective tissue layers
• These two layers separate to form dural sinuses in certain areas

Arachnoid Mater

• The middle arachnoid mater is a loose membrane
• It is separated from the dura mater by the subdural space
• A wide subarachnoid space filled with CSF and large blood vessels separates it from pia mater
• Arachnoid villi protrude superiorly, permitting CSF to be absorbed into venous blood

Pia Mater

• The inner pia mater has internal fine fibrous connective tissue layers with many minute blood vessels
• It adheres to the surface of the brain, dipping into each fissure

Meningeal Spaces

• The subdural space lies between the arachnoid mater and dura mater
• The subarachnoid space lies between the arachnoid mater and pia mater and is filled with CSF
• The epidural space lies between the dura mater and vertebral wall and contains fat and small blood vessels

Cerebrospinal Fluid (CSF)

• CSF is a watery solution similar to blood plasma
• The choroid plexus forms it
• CSF forms a watery cushion to protect the brain and spinal cord
• It circulates in the arachnoid space, ventricles, and central canal of the spinal cord

Functions of CSF

• CSF provides resistance to CNS organs, protects the CNS from blows and other trauma, and nourishes the brain while carrying chemical signals

Brain Divisions

• The brain is divided into the forebrain, midbrain, and hindbrain

Forebrain

• The forebrain includes the cerebrum and diencephalon

Hindbrain

• The hindbrain consists of the pons, medulla oblongata, and cerebellum

Cerebrum

• The cerebrum is the largest part of the brain
• It consists of the outer gray matter and inner white matter
• There are two cerebral hemispheres connected by the corpus callosum
• Each hemisphere has four lobes: frontal, parietal, temporal, and occipital

Sulci and Gyri

• The surface of the brain includes sulci and gyri, each lobe is separated from others by sulci
• Main sulci include central, lateral, and parietooccipital sulci

Functions of Lobes

• The frontal lobe is responsible for motor, intellectual, and personality functions
• The parietal lobe is for sensation
• The temporal lobe is for hearing and memory
• The occipital lobe is for vision

Diencephalon

• It sits on top of the brain stem and is enclosed by the cerebral hemispheres.
• Its four parts consist of the thalamus, hypothalamus, subthalamus, and epithalamus

Brain Stem

• Directly attaches to the brain and spinal cord.
• Consists of nerve fibers and nerve cells.
• Its parts consist of the midbrain, pons, and medulla oblongata

Midbrain

• An integral part of auditory pathways in the CNS
• It controls involuntary functions

Pons

• Located below the midbrain
• Contains sleep and respiratory centers, which regulate the rate and depth of breathing
• Controls consciousness and concentration levels

Medulla Oblongata

• The medulla has a cardiac center which regulates heart rate
• Contains a vasomotor center and is for blood vessel diameter
• Acts as a respiration center for coughing and sneezing
• It controls swallowing and vomiting

Cerebellum

• Lies posterior to the pons and medulla oblongata
• It has two cerebellar hemispheres, connected by the vermis

Cerebellum Functions

• Coordination of movement
• Control posture and equilibrium

Ventricles

• Four connected cavities within the cerebrum and brain stem are continuous with the central canal of the spinal cord

Fluid

• The brain ventricles are filled with CSF

Brain Ventricles

• Right and left lateral ventricles within the cerebral hemisphere
• The 3rd ventricle is in the cavity of the diencephalon
• The 4th ventricle is in the cavity of the brainstem

Lateral Ventricles

• Lateral ventricles are in the cerebral hemispheres
• They are shaped like a horseshoe from the hemispheres bending
• The third ventricle is in the diencephalon. It is connected with the lateral ventricles by the interventricular foramen

Cerebral Aqueduct

• The cerebral aqueduct connects the 3rd and 4th ventricles

Fourth Ventricle

• The fourth ventricle lies in the hindbrain and connects to the central canal of the spinal cord

Spinal Cord

• The spinal cord is a long cylindrical part of the lower brain
• It is present in the vertebral canal
• It extends from the C1-L1 vertebra
• It passes through the foramen magnum
• The spinal cord continues as the medulla oblongata
• The lower part of the spinal cord is called the conus

Gross Anatomy of the Spinal Cord

• Atlas, Cervical plexus, Cervical enlargment, Brachial plexus, Thoracic, Lumbosacral enlargement, Lumbar, Sacral plexus, Filum terminale

Dimensions of Spinal Cord

• Spinal cord length is 42-45 cm
• Two enlargements happen in the cervical and lumbar regions

Spinal Cord Anatomy

• Meninges cover the spinal cord
• There are 31 pairs of spinal nerves, present in intervertebral foramina
• The spinal nerves have dorsal and ventral roots

Spinal Cord Sections

• Exterior white matter is for conduction tracts
• Internal gray matter contains cell bodies
• There are dorsal (posterior) and anterior (ventral) horns

Spinal Cord Structures

• Central canal is filleld with the cerebrospinal fluid

Peripheral Nervous System: Spinal Nerves

• Contains spinal nerves that arise and originate from the spinal cord
• The nerves are attached by an anterior(motor) and posterior(sensory) root connect together form trunk of the spinal nerve mix then give two rami anterior and posterior also mix.

Division of Nerves

• The nerves are divided into Cervical (8), Thoracic (12), Lumbar (5), Sacral (5), Coccygeal (1)

Cranial Nerves

• There are twelve cranial nerves in total
• Olfactory nerve (CN I) and optic nerve (CN II) originate from the cerebrum

Brainstem Cranial Nerves

• Cranial III – XII arise from the brainstem
• The oculomotor (III) and trochlear (IV) cranial nerves originate from the midbrain

Facial Nerves Origin

• Trigeminal (V), abducent (VI), and facial nerves (VII) vestibulocochlear (VIII) start in the pons
• Glossopharyngeal (IX), vagus (X), accessory (XI) and hypoglossal nerves (XII) connect and attach to the medulla oblongata

Olfactory Nerve

• Cranial Nerve I
• Smell (sensory)

Optic Nerve

• Cranial Nerve II
• Vision (Sensory)

Oculomotor Nerve

• Cranial nerve III
• Eye muscles(motor)

Trochlear Nerve

• CN IV
• Eye muscles (motor)

Trigeminal Nerve

• CN V
• Facial(sensory), chewing muscles(motor)

Abducens Nerve

• CN VI
• Eye muscles(motor)

Facial Nerve

• CN VII
• Taste(sensory), facial muscles (motor)

Vestibulocochlear Nerve

• CN VIII
• Balance and hearing(sensory)

Glossopharyngeal Nerve

• CN IX
• Taste(sensory), swallowing (motor)

Vagus Nerve

• CN X
• Sensory and motor neurons and is responsible for effects on sweating, peristalsis, heart rate, opening the larynx for speech, and breathing
• It has branches in the ear

Accessory Nerve

• CN XI
• Neck & upper back muscles (motor)

Hypoglossal Nerve

• CN XII
• Tongue (motor)

Sympathetic Nervous System

• The sympathetic system is active in a "fight or flight" response
• It increases heart rate, blood pressure, and increases the respiratory rate
• Causes bronchodilation
• Decreases intestinal motility, urination, and sweating

Parasympathetic Nervous System

• The parasympathetic system is active during occur at rest
• It lowers rate, breathing rate
• Stimulates intestinal motility and increases the secretion of the glands
• Causes bronchoconstriction

Special Senses

• The special senses include taste, smell, sight, hearing, and touch

General Senses of Touch

• The general senses of touch include temperature, pressure, and pain

Taste Buds

• Taste buds are sensory organs on the tongue that send taste messages to the brain
• They are found in the papillae of the tongue mucosa, specifically fungiform and circumvallate papillae
• An 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
• 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

Fibrous Tunic

• Outermost coat of the eye
• Composed of an opaque sclera (posteriorly) and a clear cornea (anteriorly)
• Sclera protects the eye while the cornea lets in ligt

Vascular Tunic (Uvea)

• Choroid region supplies blood to all eye tunics
• Is composed of smooth muscles (ciliary muscles) that anchor the lens in place
• The Iris(colored part of the eye) regulates the amount of light entering the eye

Neural Layer (Retina)

• The delicate two-layered membrane
• It contains photoreceptors that transduce light energy
• Rods respond to dim light
• Cones responds bright light and have high-acuity color vision

Eye Chambers & Fluids

• The eyeball has two chambers
• The anterior chamber lies between the cornea and the iris
• The posterior chamber lies between the iris and the lens

The Ear Parts

• The three parts of the ear are the inner, outer, and middle ear
• The outer and middle ear participate in hearing
• The inner ear is in charge of hearing and equilibrium

Outer Eat

• Its part auricle (pinna) assists the ear

Exterior Auditory Canal

• Short, curved tube filled with ceruminous glands
• Transfers sound to the middle ear ossicles

Middle Ear

• Small, air-filled, mucosa-lined cavity
• Has Eustachian tube that connects it and the nasopharynx
• Equalizes pressure in the middle ear cavity with the external air pressure

Ear Ossicles

• The tympanic cavity contains three small bones knowns as :malleus, incus, and stapes
• The bones Transmit vibratory motion of the eardrum to the oval window

Inner Ear Containment

• Contains the vestibule, the cochlea, and the semicircular canals
• Contains perilymph - a watery sac

Membranous Labyrinth Containment

• Contains series of membranous sacs within the bony labyrinth that connects to each other
• Contains potassium-rich fluid

Overview of the nervous system, its composition, and functions. Includes classification into central and peripheral nervous systems, and protection of the central nervous system by meninges.