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Human Anatomy and Physiology with Pathophysiology: Peripheral Nervous System, Study notes of Anatomy

Our Lady of Fatima University (OLFU)Anatomy

A comprehensive overview of the peripheral nervous system, covering its structure, function, and associated disorders. It delves into the anatomy and physiology of nerves, cranial nerves, spinal nerves, and nerve plexuses, explaining their roles in transmitting sensory and motor impulses. The document also explores the somatic and autonomic nervous systems, highlighting their differences in effector organs and neurotransmitters. Additionally, it discusses common disorders of the nervous system, such as cerebral palsy, and provides insights into the special senses, including smell, taste, sight, hearing, and equilibrium.

Typology: Study notes

2023/2024

Available from 01/02/2025

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HUMAN ANATOMY AND PHYSIOLOGY WITH PATHOPHYSIOLOGY
1ST YEAR – 1ST SEMESTER
BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE
V
PERIPHERAL NERVOUS SYSTEM
NERVE
• A nerve is a bundle of neuron fibers
found outside the CNS.
• Each fiber is surrounded by a delicate
connective tissue sheath called
endoneurium.
• Groups of fibers are bound by the
perineurium to form fiber bundles
called fascicles.
• All the fascicles are bound together by
the epineurium to form the nerve.
• The nerves are classified according to
the direction in which they transmit
impulses.
• Sensory/afferent nerves
- carry impulses towards the CNS.
• Motor/efferent nerves
- carry only motor fibers.
• Mixed nerves
- carry both sensory and motor
fibers.
CRANIAL NERVES
• The 12 pairs of cranial nerves serve
the head and neck.
• The numbering of the cranial nerves
is based on the order in which they
emerge from the brain, front to back.
1
Olfactory
Purely sensory;
carries impulses
for the sense of
smell
2
Optic
Purely sensory;
carries impulses
for vision
3
Oculomotor
Supplies motor
fibers to four of
the six muscles
that direct the
eyeball
4
Trochlear
Supplies motor
fibers for one
external eye
muscle
5
Trigeminal
Conducts sensory
impulses from the
skin of the face,
nose, mouth. To
activate chewing
muscles.
6
Abducens
Supplies motor
fibers to the lateral
rectus muscle,
which rolls the eye
laterally
7
Facial
Activates the
muscles of facial
expression and the
lacrimal and
salivary glands;
carries sensory
impulses from the
taste buds of
anterior tongue
8
Vestibulocochle
ar
Purely sensory;
vestibular branch
transmits impulses
for the sense of
balance, and
cochlear branch
transmits impulses
for the sense of
hearing
9
Glossopharynge
al
Supplies motor
fibers to the
pharynx (throat)
that promote
swallowing and
saliva production;
carries sensory
impulses from
pf3
pf4
pf5
pf8
pf9

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1 ST^ YEAR – 1 ST^ SEMESTER BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE V PERIPHERAL NERVOUS SYSTEM NERVE

  • A nerve is a bundle of neuron fibers found outside the CNS.
  • Each fiber is surrounded by a delicate connective tissue sheath called endoneurium.
  • Groups of fibers are bound by the perineurium to form fiber bundles called fascicles.
  • All the fascicles are bound together by the epineurium to form the nerve.
  • The nerves are classified according to the direction in which they transmit impulses.
  • Sensory/afferent nerves
    • carry impulses towards the CNS.
  • Motor/efferent nerves
    • carry only motor fibers.
  • Mixed nerves
    • carry both sensory and motor fibers. CRANIAL NERVES
  • The 12 pairs of cranial nerves serve the head and neck.
  • The numbering of the cranial nerves is based on the order in which they emerge from the brain, front to back. 1 Olfactory Purely sensory; carries impulses for the sense of smell 2 Optic Purely sensory; carries impulses for vision 3 Oculomotor Supplies motor fibers to four of the six muscles that direct the eyeball 4 Trochlear Supplies motor fibers for one external eye muscle 5 Trigeminal Conducts sensory impulses from the skin of the face, nose, mouth. To activate chewing muscles. 6 Abducens Supplies motor fibers to the lateral rectus muscle, which rolls the eye laterally 7 Facial Activates the muscles of facial expression and the lacrimal and salivary glands; carries sensory impulses from the taste buds of anterior tongue 8 Vestibulocochle ar Purely sensory; vestibular branch transmits impulses for the sense of balance, and cochlear branch transmits impulses for the sense of hearing 9 Glossopharynge al Supplies motor fibers to the pharynx (throat) that promote swallowing and saliva production; carries sensory impulses from

1 ST^ YEAR – 1 ST^ SEMESTER BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE V taste buds of the posterior tongue and from pressure receptors of the carotid artery 1 0 Vagus Fibers carry sensory impulses from and motor impulses to the pharynx, larynx, and the abdominal and thoracic viscera; most motor fibers are parasympathetic fibers that promote digestive activity and help regulate heart activity 1 1 Accessory Mostly motor fibers that activate the sternocleidomasto id and trapezius muscles 1 2 Hypoglossal Motor fibers control tongue movements: sensory fibers carry impulses from the tongue SPINAL NERVES AND NERVE PLEXUSES

  • The 31 pairs of spinal nerves are formed by the combination of ventral and dorsal roots of the spinal cord.
  • The spinal nerves then divide into dorsal and ventral rami (which contains both motor and sensory fibers).
  • The smaller dorsal rami serve the skin and muscles of the posterior body trunk.
  • The ventral rami of spinal nerves T1 to T12 form the intercostal nerves.
  • Intercostal Nerves
  • supply the muscles between the ribs and the skin and muscles of the anterior and lateral trunk.
  • The ventral rami of all other spinal nerves form plexuses.
  • Plexuses
  • serve the motor and sensory needs of the limbs. AUTONOMIC NERVOUS SYSTEM
  • The motor subdivision of the PNS that controls body activities automatically.
  • Composed of group of neurons that regulate cardiac muscle, smooth muscles, and the glands. SOMATIC VS AUTONOMIC NERVOUS SYSTEM
  • Difference in effector organs and neurotransmitters released.
  • The Autonomic Nervous System has two arms that serve the same organs but cause opposite effects that counterbalance each other’s activities.
  • Sympathetic division mobilizes the body during extreme situations.
  • Parasympathetic division allows us to “unwind” and conserve energy. MOTORS PATHWAY
  • Somatic nervous system
  • The cell bodies are inside the CNS , and their axons extend all

1 ST^ YEAR – 1 ST^ SEMESTER BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE V SPECIAL SENSES

  • Includes the senses of smell, taste, sight, hearing, and equilibrium.
  • Touch is a mixture of general senses (temperature, pressure and pain receptors of the skin and the proprioceptors of muscles and joints). THE EYE AND VISION EXTERNAL AND ACCESSORY STRUCTURE
  • The eyes are protected by the eyelids , which meet at the medial and lateral canthus.
  • The eyelashes project from the border of each eyelid.
  • Tarsal glands associated with the eyelid edges produce an oily secretion that lubricates the eye.
  • The conjunctiva lines the eyelids and covers part of the outer surface of the eyeball, secreting mucus to lubricate the eyeball.
  • The lacrimal apparatus consists of lacrimal gland and a number of ducts that drain the lacrimal secretions into the nasal cavity.
  • Lacrimal glands continually release a dilute salt solution (tears) onto the anterior surface of the eyeball.
  • Tears / Dilute Salt Solution
  • Cleanses
  • Protects the eye surface.
  • Moistens
  • Lubricates
  • The tears flush
  • across the eyeball
  • into the lacrimal canaliculi
  • medially then into the lacrimal sac,
  • and finally, into the nasolacrimal duct
  • which empties into the nasal cavity.
  • Six extrinsic/external eye muscles are attached to the outer surface of each eye that produces gross eye movements and make it possible for the eyes to follow a moving object. INTERNAL STRUCTURES: THE EYEBALL
  • The eye / eyeball is a hollow sphere.
  • Its wall is composed of tunics or layers.
  • The interior is filled with fluids called humors.
  • The lens (main focusing apparatus of the eye) divides the eyes into two chambers. LAYERS FORMING THE WALL OF THE EYEBALL FIBROUS LAYER
  • Sclera
  • is a thick white connective tissue.
  • It is seen anteriorly as the “white of the eye”.
  • The central anterior portion of the sclera is modified so that it is crystal clear.
  • This transparent “window” is the cornea through which light enters the eye. VASCULAR LAYER
  • The middle coat of the eyeball.
  • The choroid, which is the most posterior region of the vascular tunic , is a blood-rich nutritive tunic that contains a dark pigment.

1 ST^ YEAR – 1 ST^ SEMESTER BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE V

  • This pigment prevents light from scattering inside the eye.
  • The anterior part of the choroid is modified to form two smooth muscles structures :
  • the ciliary body
  • the iris.
  • Ciliary Zonule
  • a suspensory ligament which attached the lens to the ciliary body.
  • Pupils
  • Rounded Opening in the pigmented iris.
  • Where light passes through.
  • Iris
  • Is formed from circularly and radially arranged smooth muscles.
  • It regulates the amount of light entering the eye so that one can see as clearly as possible in the available light.
  • Cranial nerve III (oculomotor)
  • controls the muscles of the iris. SENSORY LAYER
  • The innermost sensory tunic of the eye is the delicate two-layered Retina.
  • Pigmented layer – outer layer of retina; composed of pigmented cells.
  • Neural layer – inner layer of retina; contains millions of receptor cells, the rods, and cones, which are called photoreceptors.
  • The result is vision.
  • The photoreceptor cells are distributed over the entire retina, except where the optic nerve leaves the eyeball. This site is called the optic disc.
  • When light from an object is focused on the optic disc, it disappears from view. SENSORY LAYER: Rods
  • The rods and cones are not evenly distributed in the retina.
  • The rods are most dense at the periphery or edge of the retina and decrease in number as the center of the retina is approached.
  • The rods allow us to see in gray tones in dim light and provide for our peripheral vision. SENSORY LAYER: Cones
  • Cones are most dense in the center of the retina and decrease in number toward the retinal edge.
  • Cones allow us to see the world in color under bright light conditions.
  • Lateral to each blind spot is the fovea centralis, a tiny pit that contains only cones. This is the area of greatest visual acuity or point of sharpest vision. SENSORY LAYER: Varieties of Cones
  • There are three varieties of cones:
  • One responds most vigorously to blue light, another to green light. The third responds to a range including both green and red wavelengths of light.
  • Impulses received at the same time from more than one type of cone by the visual cortex are interpreted as intermediate colors.

1 ST^ YEAR – 1 ST^ SEMESTER BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE V chamber carved into the temporal bone.

  • Ceruminous glands can be found in its skin-lined walls, which secrete a waxy yellow substance called cerumen or earwax.
  • Sound waves entering the external auditory canal eventually hit the tympanic membrane, or eardrum and cause it to vibrate. MIDDLE EAR
  • The middle ear or tympanic cavity is an air-filled cavity within the temporal bone.
  • It is flanked laterally by the eardrum and medially by a bony wall with two openings: the oval window and the round window.
  • The pharyngotympanic (auditory) tube runs obliquely downward to link the middle ear with the throat.
  • The pharyngotympanic tube is flattened and closed, but swallowing or yawning can open it briefly to equalize the pressure in the middle ear cavity with the external or atmospheric pressure.
  • This is an important function because the eardrum will not vibrate freely unless pressure on both of its surface is the same.
  • The tympanic cavity is spanned by the three smallest bones in the body, the ossicles, which transmit vibratory motion of the eardrum to the fluids of the inner ear.
  • These bones are the hammer (malleus), anvil (incus), and stirrup (stapes).
  • When the eardrum moves, the hammer moves with it and transfers the vibrations to the anvil. The anvil in turn, passes it on the stirrup which presses on the oval window of the inner ear. INNER/INTERNAL EAR
  • The inner ear is a maze of bony chambers called the osseous labyrinth or bony labyrinth.
  • It is subdivided into three:
  • the cochlea
  • vestibule
  • semicircular canals.
  • The bony labyrinth is filled with a plasmalike fluid called perilymph. MECHANISMS OF EQUILIBRIUM
  • The equilibrium receptors of the inner ear, sometimes called the vestibular apparatus, can be divided into two branches. One responsible for monitoring static equilibrium, and the other involved with dynamic equilibrium. STATIC EQUILIBRIUM
  • Within the vestibule are receptors called maculae that is essential for the sense of static equilibrium. The maculae report on the position of the head with respect to the pull of gravity when the body is not moving.

1 ST^ YEAR – 1 ST^ SEMESTER BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE V

  • Since they provide information on which way is up or down, they help keep our head erect.
  • Each macula is a patch of receptor cells with their “hairs” embedded in the otolithic membrane, a gel or jellylike material containing otoliths, tiny stones made of calcium salts.
  • As the head moves, the otoliths roll in response to changes in the pull of gravity. DYNAMIC EQUILIBRIUM
  • The dynamic equilibrium receptors, found in semicircular canals, respond to angular or rotatory movement of the head.
  • Within each membranous semicircular canal is a receptor region called a crista ampullarids.
  • The crista ampullaris consists of a tuft of hair cells covered with gelatinous cap called the cupula. MECHANISM OF HEARING
  • Within the cochlear duct is the organ of Corti, which contains the hearing receptors or hair cells.
  • Sound waves that reach the cochlea through vibrations of the eardrum, ossicles, and oval window set the cochlear fluids into motion.
  • As the sound waves are transmitted, their force is increased by the activity of the ossicles. These pressure waves set up vibrations in the basilar membrane.
  • The receptor cells, positioned on the basilar membrane in the organ of Corti, are stimulated when their hairs are bend or tweaked by the movement of the gel-like tectorial membrane that lies over them.
  • Once stimulated, hair cells transmit impulses along the cochlear nerve to the auditory cortex in the temporal lobe, where interpretation of sound occurs. CHEMICAL SENSES: TASTE AND SMELL
  • The receptors for taste and olfaction are classified as chemoreceptors because they respond to chemicals in solution. OLFACTORY RECEPTOR AND THE SENSE OF SMELL
  • Olfactory receptors occupy an area in the roof of each nasal cavity.
  • The olfactory receptor cells are neurons with olfactory hairs, long cilia that protrude from the nasal epithelium and are continually bathed by a layer of mucus secreted by underlying glands. MECHANISM OF OLFACTORY RECEPTOR AND THE SENSE OF SMELL
  • When the receptors are stimulated by chemical dissolved in the mucus, they transmit impulses along the olfactory filaments, which collectively make up the olfactory nerve. TASTE BUDS AND THE SENSE OF TASTE
  • The taste buds are widely scattered in the oral cavity, and most are located on the tongue.