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PERIPHERAL NERVOUS SYSTEM
- Includes all neurons except those in brain or cord
- Pathways of fibers and between CNS and periphery of body
- Includes:
- Cranial nerves arise from brain
- Spinal nerves arise from cord
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PNS
- Afferent fibers TO
- Carry sensory information from periphery to CNS
- Efferent fibers FROM
- Somatic –motor cranial/spinal fibers connect CNS to skeletal muscle
- Autonomic- motor fibers can see in this two part smooth muscle and glands
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CRANIAL NERVES (12 PAIRS)
- S I Olfactory sense olfaction cribriform plate
- S II Optic sense of vision optic foramen
- M III Oculomotor move eye superior orbital fissure
- M IV Trochlear move eye superior orbital fissure
- MXV Trigeminal ** senses cornea, forehead, brows, eyelids, nose, palate, gums, etc. jaw move mastication muscles
- **(S--ophthalmic branch-superior orbital fissure) (S--maxillary branch-foramen rotundum) (MX--mandibular branch-foramen ovale)
- M VI Abducens move eye Superior orbital fissure
- MX VII Facial since taste, facial muscles move facial muscles, lacrimal and salivary secretion internal auditory canal TO exit stylomastoid foramen
- S VII Vestibulocochlear Cochlear branch –sense of hearing
- Vestibular branch- sense balance and equilibrium internal auditory canal
- MXIX Glossopharyngeal sense tongue, move pharyngeal muscles, salivary secretion jugular foramen
- MXX Vagus sends pharynx, auricle, external acoustic meatus, diaphragm, viscera in thoracic and abdominopelvic cavities motor to repiratory, digestive, and cardio vascular organs
- M XI Accessory Move muscles of head & neck and swallowing Jugular foramen
- M XII Hypoglossal Move muscles of tongue Hypoglossal canal
- Sensory
- Motor
- MiX
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SPINAL NERVES
- • 31 pairs of spinal nerves
- • Leave vertebral canal via intervetebral foramina
- • (except 1st pair which exit between occipital/atlas)
- • Spinal nerves are formed by union of dorsal/ventral roots (mixed)
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VENTRAL (ANTERIOR) ROOT
- Consist of axons of motor neurons
- Cell bodies of these motor axons in ventral and lateral columns of gray matter of cord
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DORSAL (POSTERIOR) ROOT
- Consists of axons of sensory neurons entering dorsal column matter
- Cell bodies of theses sensory axons are outside cord in dorsal rood ganglia
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AFTER LEAVING THE INTERVETEBRAL FORAMEN THE SPINAL NERVE SPLITS INTO BRANCHES CALLED RAMI
- Posterior ramus innervates the deep muscles of the back and skin of the back
- Anterior ramus innervates the anterior and lateral portions of the trunk and the upper and lower limbs
- Anterior ramus splits into other rami (branches)
- Anterior rami form nerve plexuses
- Rami communicates branch from anterior rami to sympathetic trunk ganglion
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A NERVE PLEXUS IS A NETWORK OF INTERWEAVING ANTERIOR RAMI OF SUCCESSIVE SPINAL NERVES.
- Anterior rami of most spinal nerves form nerve plexuses on both side of the body
- Plexuses split into named nerves and go on to innervate body structures
- The principle plexuses are the:
- Cervical plexus
- Brachial plexus
- Lumbar plexus
- Sacral plexus
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AUTONOMIC NERVOUS SYSTEM
- The autonomic nervous system (ANS) is a complex system if nerves that governs involuntary actions
- Motor (efferent) neurons that innervate cardiac muscle, smooth muscle and glands
- 1. Regulates heart rate
- 2. Regulates blood pressure
- 3. Regulates breathing rate
- 4. Regulates body temperature
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Functions below conscious level (autonomously)
- Autonomic activities originates from sensory signals in viscera or skin
- 2 motor (efferent) neurons are needed to carry impulses to effector organ
- 1. Preganglionic neuron-located in CNS (cell body)
- 2. Postganglionic neuron-located in ganglion (cell body)
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DIVISION OF ANS
- • Parasympathetic division-conservation of energy and replenishment of nutrient stores (“rest and digest”)
- • Sympathetic division-preparation of body for emergency (“fight or flight”). Increased alertness and metabolic activity
- • Divisions differ both structurally and functionally
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SYMPATHETIC (THORACOLUMBAR)
- • Cell bodies of preganglion neurons located in . . . lateral column of gray matter of cord
- • Axons of preganglion neurons leaves cord via ventral root alonf with somatic motor axons and enter posterior/ anterior rami
- • After a short distance in anterior rami fibers enter a chain of sympathetic (paravertebral) ganglia along vertebral column
- • Since preganglion acons are myelinated they look white, are called …white rami
- • Sympathetic system predominates during strenuous exercise, stress or emergencies
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PREGANGLIONIC AXON MAY DO ONE OF 3 THINGS
- 1. Synapse. . .
- • With cell body of ganglionic cell then postganglionic fiber leaves ganglion via pathway called gray ramus and returns to spinal nerve (ventral ramus) and goes on to innervate effector
- 2. Travel up/down . . .
- • Sympathetic trunk before synapsing with a ganglionic cell
- 3. Pass thru. . .
- • The sympathetic ganglion without synapsing and continues as splanching nerves which pass thru diaphragm and synapse in collateral ganglia near aotra. Postganglionic fiber leave ganglia and innervate viscera in abdominopelvic cavity
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PARASYMPATHETIC (CRANIOSACRAL)
- • Cell bodies of parasympathetic ganglionic fibers neurons are located in the . . .brain or the lateral column of gray matter of cord s2-4
- • Parasympathetic fibers do not travels thru rami of spinal nerves these fibers travel with cranial/spinal nerves to ganglia in (intramural ganglia)_ or near (terminal ganglia) effecter
- • Antagonistic
- • Dual innervations
- • On set of fiber activate other inhibits
- • Predominate during resting conditions
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SYMPATHETIC RESPONDS TO STRESS
- • Increase
- o Heart rate
- o Blood floow to muscles
- o Respiratory rate
- o Blood glucose l
- o Secretion of sweet
- • Dialate
- o Pupil
- o bronchi
- • Decrease
- o blood flow to GI tract
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PARASYMPATHETIC
- works in opposition
- (returns body to normal after stress)
- • Decrease
- o Heart rate
- o flow to muscles
- o Respiratory rate
- • Constrict
- o Pupil
- o bronchi
- • Increase
- o Activity of glands
- o Contract smooth muscle of GI tract
- o Production of tears
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MANY DRUGS EFFECT THE ANS. . .
- Sympathomimetic drugs mimic sympathetic ANS
- (Ex: Amphetamine)
- Some drugs inhibits Parasympathetic ANS
- (Ex: atropine)
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DISORDERS
- Cerebral palsy
- a condition of motor disorder characterized by muscle weakness and lack of function caused by damage to the brain during prenatal development, birth, or infancy
- Meningitis
- Infection of meninges
- Cocci, bacilli, viral
- Often respiratory entry
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Poliomyelitis
Virus destroys nerve cells of anterior (ventral) horn of spinal cord
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SENSATION
- We are constantly exposed to sensory information . . . stimuli
- Our conscious awareness to stimuli is . . . sensation
- Stimuli are detected by . . . receptors
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Receptors can be classified according to location:
- 1. Somatic receptor—in the body wall (receptors for chemical, tempature, pain, touch, proprioception and pressure)
- 2. Visceral receptor—in walls of the viscera (receptors for chemical, temperature and pressure)
- 3. Special senses—in the head (receptors for gustation (taste), olfaction, vision, equilibrium and hearing)
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RECEPTORS CAN ALSO BE CLASSIFIED ACCORDING TO THE TYPE OF STIMULATING AGENT
- 1. Chemoreceptor—detect specific molecule dissolved in fluid
- 2. Thermoreceptor—detect changes in tempature
- 3. Photoreceptor—detect changes in light intensity, color and movement of light
- 4. Mechanoreceptor—detect physical deformation due to touch, pressure, vibration and stretch
- 5. Baroreceptor—detect pressure changes within body structures (vessels)
- 6. Nocioreceptor—detect tissue damage and pain
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EYE
- • Special sense organ that contains photoreceptors for vision
- • These photoreceptors are capable of detecting light, color and movement
- • There are accessory structures that prevent foreign objects from coming in contact with the eye and insure that the surface of the eye remain clean and moist
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ACCESSORY STRUCTURE
- EYEBROWS short hairs on superior orbital ridge that prevent sweat dripping
- EYELASHES prevent foreign objects from entering eyes
- EYELIDS (PALPEBRAE) protect from sun/foreign particles
- CONJUNCTIVA stratified squamous epithelium lines lids and covers anterior surface eyeball (not cornea) prevents objects access behind eyeball
- TARSAL GLANDS
- (MEIBOMAIN GLANDS) Sebaceous glands within both eyelids prevent tear overflow and lids from sticking together
- LACRIMAL APPARATUS Lacrimal glands and ducts located on superior/lateral region of orbit. Produces, collects and drains lacrimal fluid from eye. Lubricates and helps prevent infection. Contains lyosomes (bacteriocidal)
- EXTRINSIC MUSCLES Move eye
- 4 RECTUS MUSCLES (lateral/medial/superior/inferior)
- 2 OBLIQUE MUSCLES (Inferior/superior)
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EYE
- Three principle layers form the wall of the eye :
- 1. Fibrous tunic
- 2. Vascular tunic
- 3. Nervous tunic (retina)
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FIBROUS TUNIC (OUTER)
- CORNEA
- • On anterior 1/6 of eye
- • Transparent, refractive, convex, avascular
- • Dense connective tissue
- • Outer layer of stratified squamous epithelium (continuous with conjunctiva)
- • Receives oxygen and nutrients from lacrimal fluid and aqueous humor
- SCLERA
- • On posterior 5/6 of eye
- • White, opaque
- • Dense connective tissue
- • Protects/maintains shape
- • Optic nerve exits thru
- • Extrinsic muscle attach
- VASCULAR TUNIC (MIDDLE)
- CHOROID
- • Vascular, darkly pigmented
- • Contains net work of capillaries which supply nutrients and oxygen to retina
- • Prevents light from being reflected
- CILLIARY BODY (MUSCLE/ PROCESSES)
- • Continuous with choroid
- • Form ring of smooth muscle
- • Attaches to suspensory ligaments (zonule fibers)
- IRIS
- • Continuous with cilliary body
- • Contains hole called pupil
- • Pigmented portion of the eyeball
- • Smooth muscle fibers (circular/radial
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NERVOUS TUNIC (INNER)
- RETINA
- • Innermost layer in posterior portion if eye
- • 2 layers of retina
- o Thin/outer pigmented layer
- o Inner neural tissue layer
- Photoreceptors (rod/cones)
- Bipolar cells
- Ganglion cells (axons from optic nerve)
- MACULA LUTEA
- • Yellow area at exact posterior pole
- FOVEA CENTRALIS
- • Depression in center of macula lutea
- • cones most concentrated
- • no rods area of sharpest vision
- BLIND SPOT (OPTIC DISC)
- • Where optic nerve (axons) leaves retina
- • No rods/cones
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LENS
- • Transparent, deformable structure suspended behind the pupil by suspensory ligaments (zonule fibers)
- • Suspensory ligaments are attached to the outer capsule of the lens
- • Relaxing or tensing ligaments causes change in shape of lens
- • Tension is caused by the cilliary muscles
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ACCOMONDATIONS . . . shape of lense changes for near or far vision
- Cilliary muscles relax (pulled posterior)/suspensory ligaments contract . . .lens flattens for FAR vision
- Cilliary muscles contract (pulled forward)/suspensory ligaments relax . . . Lens rounded for CLOSE vision
- Pupil (in iris) changes size to adjust to light entering
- • pupillary radial muscles contracts. . . . . . . . . . . . pupil dilates
- • pupilary sphincter contracts . . . . . . . . . . . . . . . . . pupil condtricts
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CAVITIES OF THE EYE
- ANTERIOR CAVITY
- • Lens to cornea
- • Filled with aqueous humor
- • Cilliary body produces 5-6ml daily
- • Maintains intraocular pressure, nutrients, oxygen
- • Drains into sclera venous sinus (canal of Schlemm)
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POSTERIOR CAVITY
- • Lens to retina
- • Vitreous humor
- • Formed prenatally
- • Transparent, gel-like, support
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VISUAL PATHWAYS
- • Light enters the pupil, thru aqueous humor, lens, vitreous humor, and is detected by photoreceptors in the retina
- • Electrical stimuli is then passed to the bipolar cells and then to the ganglion cells of the retina
- • Axons of the ganglion cells leave the retina forming the optic nerve
- • Optic nerve converge at the optic chasm and ganglion axons from the medial retinas of both eyes cross over (decussate) to the opposite side of the brain
- • Ganglion axons will enter an optic tract. Some will project to the superior colliculi and the remainder will project to the thalamus
- • Neurons from the thalamus project to the visual cortex of the occipital lobe
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EAR
- Organ of hearing and equilibrium
- 3 REGIONS
- 1. External
- 2. Middle
- 3. Inner
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EXTERNAL
- Auricle (pinna)
- External acoustic (auditory) meatus
- Tympanic membrane
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MIDDLE
- Contains 3 ossicles
- 1. Malleus
- 2. Incus
- 3. Stapes
- Middle ear ossicles are contained in the tympantic membrane cavity in the temporal bone
- Tympanic cavity communicates with nasopharynx via auditory tube (euxtachain tube) to equalize pressure on either side of the tympanic membrane
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INNER (osseous and membranous labyrinth)
- Osseous (bony) labyrinth
- • In pertrous potion of temporal bone
- • Series of passageways hollowed out
- • Within osseous labyrinth is contains the membranous labyrinth
- Vestibules
- • Contains oval/round window
- Semiscircular canals
- • 3 bony canals
- Cochlea
- Snail chaped
- 3 scala (chambers)
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3 SCALA OF THE COCHLEA
- 1. Scala vestibuli. . . . . . . . . . . . . . . . . . . . begins at oval window
- 2. Scala tympani. . . . . . . . . . . . . . . . . . . .terminates at round window
- 3. Scala media (cochlea duct)
- . . . . . . . . . . . . . . .which is part of membranous labyrinth
- . . . . . . . . . . . . . . .contains the organ of corti (spiral organ)
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MEMBRANOUS LABYRINTH
- Saccule and utricle
- • Which have receptor cells for orientation and linear head movement
- • Maculae
- Membraneous semicircular canals
- • Which have receptors cells for rotational head movment
- • Crista amullaris
- Cochlear duct (scala media)
- • Conatins spiral organ (organ corti) hair cells (sound receptors) which transforms mechanical vibrations into nerve impulses
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CONDUCTING MEDIA OF EAR
- Endolymph inside membranous labyrinth
- Perilymph between membranous and osseous labyrinth
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EQUILIBRIUM PATHWAY
- 1. Hair cells in the vestibule and the semicircular canals detect movement of endolymph
- 2. Vestibular axons project to vestibular nuclei in the medulla
- 3. Impulses from these nuclei go to:
- • Spinal cord for muscle tone and balance
- • Brainstem for reflexive motor activities associated with eye movement and head and neck functions
- 4. Cerebellum, thalamus, and cerebral cortex
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HEARING
- Sound waves arrive at tympanic membrane
- Movement of tympanic membrane causes displacement of auditory ossicles
- Movement of stapes at oval window establishes pressure waves in perilymph of vestibular duct
- Pressure waves distort the basilar membrane
- Vibration of basilar membrane causes vibration of hair cells resulting in stimulation
- Stimulation relayed to CNS via cochlear branch VIII
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DISORDERS IF THE EYE AND EAR
- Myopia elongation of the eyeball which causes light waves to focus in front of the retina
- Hyperopia shortness of the eyeball which causes light to focus behind the retina
- Presbyopia lens loses its ability to accomondate
- Amblyopia “lazy-eye” muscle weakness in one eye so eyes don’t converge
- Astigmatism irregular curvature of the cornea or lens
- Glaucoma aqueous humor accumulates in the anterior cavity
- Cataracts chemical change within the protein of the lens
- Otosclerosis bones in the middle ear fuse (conduction)
- Sensineural deafness damage to neural structures of hearing
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ENDOCRINE SYSTEM
- One of the two control systems of the body
- The endocrine system and the nervous system both function to communicate signals throughout the body to maintain homeostasis
- A system of ductless glands
- Endocrine glands secrete hormones into the bloodstream
- Target organs have receptors which bind the hormone
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HORMONE SECRETION IS REGULATED A SELF-ADJUSTING MECHANISIM CALLED . . . . NEGATIVE FEEDBACK
- Example of negative feedback
- • Eat a meal
- • Causes increase in blood glucose
- • Elevated glucose causes pancreas to secrete insulin
- • Which decrease blood glucose
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HYPOTHALAMUS
- • The hypothalamus is the link between the nervous system and the endocrine system
- • It controls the most endocrine functions
- • It is located inferior to the diencephalon and superior to the pituitary gland
- The hypothalamus controls endocrine activity because:
- 1. It produces releasing and inhibitory hormones that control secretion of anterior pituitary gland hormones
- 2. It produces oxytocin (OT) and antidiuretic hormone (ADH) that are released from the posterior pituitary gland
- 3. It controls the stimulation and secretion activities of the adrenal medulla
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PITUITARY GLAND (hypophysis)
- Located in sella turcica
- Connected to hypothalamus by infundibulum
- 2 lobes:
- Anterior lobe adenohypophysis
- Posterior lobe neurohypophysis
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HORMONES OF THE ANTERIOR PITUITARY
- There are seven major hormone secretion from the anterior pituitary:
- 1. Thyroid stimulating hormone (TSH) Stimulating thyroid to secrete thyroxine
- 2. Prolactin (PRL) Stimulates milk production
- 3. Adrenocorticotropic (ACTH) Stimulates adrenal cortex to secrete steroids
- 4. Growth hormone (GH) also called somatotrophin/ Stimulates growth and metabolism
- 5. Follicle stimulating hormone (FSH) Stimulates follicle production/spermatogenesis
- 6. Luteinizing hormone (LH) Stimulates ovulation/androgen synthesis
- 7. Melanocyte stimulating hormone(MSH) stimulates production of melanin
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POSTERIOR PITUITARY (neurohypophysis)
- ******DOES NOT PRODUCE ANY HORMONES******
- STORES and RELEASES
- (2 hormones produced by the hypothalamus)
- 1. Oxytocin
- • Produced in paraventricle cells of hypothalamus
- • In female stimulates smooth muscle contractions in uterus
- • In female stimulated milk “let-down”
- • In male stimulates smooth muscle contraction in prostate gland
- 2. Antidiuretic hormone (ADH, vasopressin)
- • Produced by supraoptic nucleus of the hypothalamus
- • Increase water reabsorption in kidney tubules
- • Constriction of arteriorles (increase blood pressure)
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ADRENAL GLAND
- Divided functionally into an outer adrenal cortex and an inner adrenal medulla
- Adrenal cortex is made up of three regions
- 1. Zona glomerulosa—produce mineralocorticoids main one being aldosterone (regulates electrolyte/fluids)
- 2. Zona fasciulata—produce glucocorticoids, the main one being corticosterone (stimulates lipid/protein metabolism)
- 3. Zona reticularis—produce the sex hormones, estrogen and testosterone related hormones (stimulates protein synthesis in sex organs)
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ADRENAL MEDULA
- • Inner region of gland
- • Chromaffin cells are modified cells of sympathetic division autonomic nervous system
- • Secrete norepinepherine and epinephrine
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PANCREAS
- • Located between the duodenum and stomach
- • Both an exocrine (ducted) gland and an endocrine (ductless) gland
- • About 98-99% of pancreatic cells are pancreatic acini that produce enzymes into ducts
- • The remaining 1-2% of cells are small clusters of endocrine cells called pancreatic islets (islets of langerhands) that produce the hormones
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PANCREATIC ISLETS
- Are comprised of four different types of endocrine cells that secrete different hormones that secrete different hormone
- Alpha cells –secrete glucagon (increase blood glucose)
- Beta cells –secrete insulin (decrease blood glucose)
- Also,
- Delta cells—secrete somatostatin (inhibits insulin and glucagon)
- F cells—secrete pancreatic polypeptide (suppresses somatostatin)
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THYROID GLAND
- • Largest entirely endocrine gland
- • Located just below thyroid cartilage of larynx
- 2 cell types:
- Follicle cells
- • Produce iodinated hormones
- • Thyroxine (T4), thriiofothyornine (T3)
- • Stored in gland as thyroglobulin
- • Increase metabolic rate, protein synthesis and catabolism
- Parafollicular cells
- • Between follicles
- • Produce calcitonin
- • Decrease blood Ca++
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PARATHYROID GLANDS
- • Four small glands embedded in the posterior surface of the thyroid gland
- • Secrete parathyroid hormone which increased blood calcium level
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PINEAL GLAND
- • Located in the posterior portion of the epithalamus
- • Secretes melatonin which is involved in maintain the 24 hour circadian cycle and sexual maturation
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THYMUS
- • Superior to the heart and deep to the sternum
- • Larger in infants and children than in adults
- • Functions with the lymphatic system to regulate and maintain body immunity
- • Thymosin
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DISORDERS
- Hypersecretion—over secretion of hormone
- Hyposecretion—under secretion of hormone
- Adrenalgenital syndrome—over secretion adrenal cortex (testosterone)
- Diabetes insipidus—under secretion posterior pituitary (ADH)
- Diabetes mellitus—under secretion of pancreas (insulin)
- Hyperglycemia—over secretion pancreas (glucagon)
- Seasonal affective disorder—over secretion pineal gland (melatonin)
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