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NERVOUS SYSTEM & SENSE ORGANS. Mrs. Ofelia Solano Saludar Department of Natural Sciences University of St. La Salle Bacolod City.

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slide1

NERVOUS SYSTEM & SENSE ORGANS

Mrs. Ofelia Solano Saludar

Department of Natural Sciences University of St. La Salle Bacolod City

slide2

ORIGIN: ectoderm gives rise to the nervous system and nervous parts of sense organs

  • FUNCTIONS:
    • Regulates behavior by integrating incoming sensory information with stored information & translating that into action by way of effectors
    • Receives stimuli from receptors & transmits information to effectors that respond to stimulation 
slide3

COMPONENTS:

Billions of neurons, each of which establishes thousands of contacts with other nerve cells

Neurogliacells that support, nourish, & insulate neurons

Sensory receptors- integrates & stores information as memory

Motor receptors- response effectors

slide10

CLASSIFICATION:

  • Central Nervous System - brain & spinal cord
  • Peripheral Nervous System - cranial nerves, spinal nerves, & all their branches
  • Autonomic Nervous System- system of ganglia, cords & plexi controlling involuntary functions:
    • Sympathetic- for fight or flight response
    • Parasympathetic- for rest and relaxation response
slide14

ORGANIZATION (arranged dorsal to ventral in spinal cord & medulla):

  • Somatic sensory- sensory impulses from skin & other layers of body wall
  • Visceral sensory- sensations from the viscera
  • Visceral motor- motor impulses from smooth & branchial muscles (ANS)
  • Somatic motor- impulses to voluntary muscles
slide16

NERVE CELL or NEURON

  • Parts:
    • Cell body- ganglion, nucleus
    • Cytoplasmic processes:
      • Axon- also called nerve fiber, fiber tracts in CNS, nerve in PNS (sensory, motor, or mixed nerve cell processes)
      • Dendrite
  • Types: Multipolar, Bipolar, Unipolar
slide20

Parkinson’s Disease in humans is known to be caused by a decrease in dopamine (neurotransmitter) in the brain. Why not just inject patients with IV dopamine?

slide21

NEUROGLIA: supportive cells to neurons

Ependymal cells – line the neurocoel and provide nutrients

Oligodendroglia – produce myelin in CNS which is white and speeds up nerve impulse transmission

Astrocytes – maintain blood brain barrier

slide22
Microglia – function as phagocytes
  • Schwann Cells – produce myelin in PNS
slide23

DEVELOPMENT OF NERVOUS SYSTEM

  • Neurulation
  • Neural tube layers:
    • Germinal layer – medial; with mitosis
    • Mantle layer – gray; cell bodies of neurons
    • Marginal layer – white; cytoplasmic processes without nuclei
      • Neuroblasts form neurons
      • Spongioblasts form neuroglia
      • Alar plate is dorsal gray matter (nuclei)
      • Basal plate is ventral gray matter
slide26

SUBDIVISIONS OF EMBRYONIC BRAIN

  • Prosencephalon (forebrain) - divides into the telencephalon & diencephalon
slide27

Mesencephalon(midbrain)- forms the tectum which includes the optic lobes (receive fibers from retina) & auditory lobes (receive fibers from inner ear)

  • Rhombencephalon (hindbrain) - subdivides into the metencephalon and myelencephalon
slide28

All vertebrates have a cerebrum based on the same basic plan

  • Major phylogenetic changes are due to loss, fusion, or enlargement of the various regions.
  • Phylogenetictrend in vertebrate brains is for enlargement of forebrain due to:
      • increasingly complex behaviors & muscle control:
      • coordination of limb movements more complicated (e.g., bipedal dinosaurs & birds)
      • increased input of sensory information & increased output of motor responses
slide30

TELENCEPHALON

  • Differentiates into the olfactory bulbs, tracts, lobes & cerebral hemispheres; olfactory part later becomes subordinated by cerebral hemispheres
  • Regions of Cerebrum:
  • PALLIUMhas 3 divisions:
    • medial (receives olfactory information)
    • dorsal & lateral divisions (receive other sensory input including information relayed from the thalamus)
slide31

SUBPALLIUM- consists of:

  • Septum - important part of the limbic system (regulates emotions & plays vital role in short-term memory)
  • Striatum - also called basal ganglia; present in all vertebrates & controls sequence of actions in complex movements
slide32

Agnathans, fish, & amphibians - pallia are similar

  • Reptiles- pallium also has a large dorsal ventricular ridge (DVR), derived from lateral pallium; DVR may be higher association area
  • Birds- DVR expands further; dorsal part increases in size & is called the wulst; as in reptiles, the DVR appears to serve as a higher association area
  • Mammals- do not have enlarged DVR but the dorsal pallium is enlarged & is called the CEREBRAL CORTEX; cortex receives & analyzes sensory information & initiates motor activity
slide34

CEREBRAL STRIATUM COMPLEX:

  • Paleostriatum– primary region in fish, primarily involved with olfactory reflexes
  • Neostriatum – beginning with reptiles, more complex and paleostriatum becomes buried
  • Hyperstriatum – primarily in birds responsible for stereotypical behavior (migration, courting, nesting)
    • Corpus striatum or basal nuclei – paleostriatum buried in mammalian brain, responsible for stereotyped & repetitive movements
    • Primitive pallium displaced by expansion of NEOCORTEX
slide36

CEREBRAL CORTEX

  • Becomes increasingly folded to fit in skull starting with reptiles up to mammals
  • Functions: voluntary movement (motor), conscious sensations (sensory), memory, integration (decisions)
  • 4 lobes according to skull bones
slide37

DIENCEPHALON- differentiates into:

  • Hypothalamus– optic chiasma, infundubular stalk for pituitary gland & mammmilary bodies particularly well developed in fishes
  • Ventral part of infundibulum unites with Rathke’s pouch to form the pituitary
  • In fishes, infundibulum also includes the inferior lobes & vascular sac
  • functions as endocrine organ, regulates ANS, sexual & emotional behavior, water balance, thermostat, hunger, satiety
  • Thalamus – relay center for sensory impulses from all parts of the body
slide39

Epithalamus- dorsal part of diencephalon; gives rise to the pineal body (epiphyses) which functions as:

  • A light receptor in agnathans & affects skin pigmentation in lower vertebrates
  • An endocrine organ in gnathostomes; plays a role in regulating biological rhythms
slide40

MESENCEPHALONcomposed of:

  • Optic lobes – 2 in most vertebrates, 4 in mammals, especially well developed in birds
  • Auditory lobes – auditory reflexes
  • Corpora Quadrigemina
  • Cerebral Peduncles – motor tracts
  • Cerebral Aqueduct – for CSF
slide41

METENCEPHALON

  • Small in cyclostomes & amphibians but increases in size & importance in amniotes
  • Consists of:
    • Pons - pathway for ascending & descending fiber tracts & origin of cranial nerves V, VI, & VII
    • Cerebellum - modifies & monitors motor output; important in maintaining equilibrium
slide42

MYELENCEPHALON

  • Undergoes little change in the vertebrate series
  • Connection between brain & spinal cord for ascending & descending pathways
  • Consists of the medulla oblongata & its major functions include:
    • origin of cranial nerves (VII - X or VII - XII)
    • contains centers important in regulating respiration, heartbeat, & intestinal motility
slide44

VENTRICLES- cavities containing cerebrospinal fluid (CSF) providing cushion, protection, nutrients

  • Formed from blood vessels called choroid plexus
  • Telachoroidea- covers the ventricles & from which choroid plexi project into ventricles
  • Location: 1st & 2nd lateral ventricles- cerebrum; 3rd ventricle- diencephalon; 4th ventricle- medulla
slide50

CRANIAL NERVES

  • Most fishes, amphibians have 10 cranial nerves; crossopterygians & amniotes have 12
  • Sensory fibers have their cells of origin in external ganglia on the nerve roots.
  • Sensory & motor roots do not unite; cranial nerves are irregular as to their functional components.
slide52

Olfactory nerve (I) - sensory nerve; sense of smell

Optic nerve (II) - sensory ‘nerve’; sense of vision; a tract of the brain & not a true nerve

slide53

Oculomotor nerve (III) - motor nerve to extrinsic eye muscles

  • Trochlear nerve (IV) - motor nerve to superior oblique eye muscles
  • Abducens (VI) - motor nerve to external rectus eyeball muscles
slide54

Trigeminal (V) - mixed nerve; sensory from skin of head & mouth (including teeth) & motor to muscles of 1st pharyngeal arch (muscles of jaw)

slide55

Facial (VII) - mixed nerve; sensory from lateral line of head, ampullae of Lorenzini, & taste buds; motor to muscles of hyoid arch

slide57

Glossopharyngeal (IX) - mixed nerve; sensory from taste buds & lateral line; motor to muscles of 3rd arch

slide58

Vagus (X) - mixed nerve; sensory from & motor to heart, anterior digestive system, mouth, gill pouches 2 - 5, & lateral line

slide59

Accessory nerve (XI) - motor to derivatives of cucullaris muscle (cleidomastoid, sternomastoid, & trapezius); amniotes only

slide62

Mnemonics to aid in memorization of cranial nerves:

“Oh, Once One Takes The Anatomy Finals, AGood Vacation Appears Heavenly.”

slide63

SPINAL CORD

Length varies among vertebrates:

  • in vertebrates with abundant tail musculature, the spinal cord extends to the caudal end of the vertebral column
  • in those without tails, the spinal cord extends to about the lumbar region of the vertebral column
slide64

REGIONS OF SPINAL CORD

  • WHITE MATTER
    • Peripheral, consists of myelinated nerve cell processes (axons).
    • Processes make up ascending (sensory) & descending (motor) fiber tracts
slide65

GRAY MATTER

  • Central; consists of nerve cell bodies (nuclei) of nonmyelinated neurons
  • Sensory dorsally, receiving the somatic & visceral impulses
  • Ventral half is motor, containing the cells of origin of the somatic & visceral motor impulses.
  • The cells of origin of the sensory impulses are always outside the CNS ganglia.
slide67

MENINGES:protective covering of brain & spinal cord

  • MeninxPrimitiva- fishes
  • Leptomeninx-thin inner membrane in higher vertebrates
  • Dura Mater- outer thick membrane in higher vertebrates
slide68

In mammals, leptomeninx splits into:

  • Piamater – innermost layer
  • Arachnoid– middle layer
  • Subarachnoidspace contains cerebrospinal fluid (CSF)
slide69

SPINAL NERVES

  • Arise from the spinal cord at segmental intervals by way of 2 roots: a dorsal or sensory root, & a ventral or motor root
  • The sensory root bears the dorsal or spinal ganglion, which contains the cell bodies of the sensory fibers
slide70

Primitively, the dorsal & ventral roots remain separate, but in gnathostomes, they unite to form a spinal nerve

  • This soon divides into:
    • Dorsal ramus - supplies epaxial muscles & skin of the dorsal part of the body
    • Ventral ramus - supplies hypaxial muscles & skin of the side & ventral part of the body
    • Communicating ramus- connects with the ANS
slide72

The ventral rami are united by cross-connections to form plexi from which the nerves to the appendicular muscles arise: Brachial plexus (anterior appendages), & the lumbosacral plexus (posterior appendages)

  • These plexi indicate that:
  • Limb muscles come from the hypaxial parts of the myotomes
  • Several myotomes contribute to the limb musculature
  • Limb muscles must have undergone torsion & change of position
slide73

Functional types of neurons in spinal nerves:

  • Somatic afferent - sensory from general cutaneous receptors & proprioceptors (tendons, & joints)
  • Somatic efferent - motor to skeletal muscles
  • Visceral afferent - sensory from receptors in the viscera
  • Visceral efferent - motor to involuntary muscles, glands
slide75

AUTONOMIC NERVOUS SYSTEM

  • Consists of: ganglia in the head region; a pair of ganglionated cords in the cervical, thoracic, & lumbar regions; sacral nerves; and a set of ganglia & ganglionatedplexi in the viscera
  • The somatic & visceral sensory fibers have similar relations, having their cells of origin in the spinal ganglia
  • Visceral motor fibers have a chain of neurones involved in innervation: The 1st sends a preganglionic fiber to a collateral or peripheral ganglion, & from this the 2nd postganglionic fiber proceeds to visceral organ.
slide76

SENSORY ORGANS

  • Sensory receptors monitor the external & internal environment by responding to selected stimuli, & translate those into nerve impulses
  • Types of sensory organs:
    • Somatic sensory - provide information about the external environment
    • Visceral sensory - provide information about the organism's internal environment
    • General sensory- widely distributed over the surface & interior of the body
    • Special sensory- confined to the head (amniotes & terrestrial amphibians)
slide77

HEARING- the ear consists of:

INNER EAR-invagination from the ectoderm

  • In all vertebrates, this membranous labyrinth is fluid-filled & embedded in skull lateral to hindbrain
  • It differentiates into the 3 semicircular ducts, sacculus, utriculus, & the endolymphatic duct.
slide78

Functions of the labyrinth:

  • Dynamic equilibrium - when head moves, inertia causes a slight relative movement of fluid in at least one semicircular canal ---> deflects cupula (in ampulla) ---> nervous impulses
  • Static equilibrium - maculae (in sacculus & utriculus) tilt when head moves ---> nervous impulses
  • Hearing – a function of organ of Corti located in lagena (enlargement of sacculus)
    • lagena tends to be longer in terrestrial vertebrates
    • in most mammals, it’s coiled into the cochlea.
    • The organ of Corti contains a specialized strip of neuromasts connected to the nervous system via the auditory nerve.
slide79

1-Inner hair cell, 2-Outer hair cells, 3-Tunnel of Corti, 4-Basilar membrane, 5-Reticular lamina, 6-Tectorial membrane, 7-Deiters' cells, 8-Space of Nuel, 9-Hensen's cells, & 10-Inner spiral sulcus

slide80

Beginning with amphibians, the MIDDLE EAR is added to inner ear, consisting of a chamber developed from the 1st gill pouch.

  • The outer wall of chamber comes in contact with skin, producing a double-walled membrane, the eardrum (tympanic membrane)
  • Within the ear is a chain of bones: incus, malleus, & stirrup, mostly derived from the gill arches
  • In amphibians & most reptiles, the eardrum is on surface of the head
  • Beginning with reptiles, the eardrum sinks into the skull, leaving a passage, the external auditory meatus.
  • This passage is deepened in birds & mammals, creating a fold of skin around the meatus, the pinna.
  • The pinna & meatus constitute the OUTER EAR.
slide81

PHOTORECEPTORS- light receptors: epiphyses & eyes

  • Vertebrates can perceive only a narrow band of electromagnetic radiation between about 350 & 760 nm
  • The nervous part of the eye is formed as an evagination from the brain; the lens is an invagination from the ectoderm; the sclera & the choroid are formed from the surrounding mesenchyme
  • The eye is moved by muscles constant in arrangement in vertebrate classes
slide82

Accommodation is the process of focusing light on the retina:

  • Lamprey - contraction of corneal muscle pulls cornea against the lens & moves the lens
  • Teleosts- retractor muscle attached to lens moves lens posteriorly
  • Amphibians & cartilaginous fishes - protractor muscle attached to lens pulls the lens forward
  • Snakes - increased pressure in the vitreous humor generated by muscles near the iris pushes the lens forward
  • Reptiles, birds, & mammals - curvature of lens is altered by ciliary (annular) muscles
slide84

General Somatic Receptors - two categories:

  • Cutaneous receptors (for touch,pressure, pain, temperature)
    • naked endings - in skin of all vertebrates; stimulated by contact
    • encapsulated endings - present in tetrapods; nerve endings wrapped in a connective tissue capsule
    • Herbst corpuscles - on beak, tongue, & palate of water birds
    • end bulbs & Ruffini corpuscles - thermal receptors in mammals
    • Pacinian corpuscles - touch & pressure receptors
  • Proprioceptors - located in skeletal muscles, joints, and tendons & provide information about body position
slide85

General Visceral Receptors:

  • Mostly naked endings in mucosa of organs, in smooth & cardiac muscles
  • Chiefly stretch & chemoreceptors
  • Monitoring functions:
    • O2 & CO2 content of blood
    • blood pressure
    • concentration of solutes in blood
slide86

Special Somatic Receptors

NEUROMAST ORGANS- receptors in skin of fishes & aquatic amphibians that detect water currents & ‘hear’ sounds

  • Occur singly, in groups, or in a linear series e.g., lateral lines
  • Modified to detect electricity (ampullae of Lorenzini)
slide87

Neuromast (groove) organs have 2 types of cells:

  • Hair cells (receptor cells) - each hair cell has several short cilia & kinocilia that project into fluid or a cupula (displacement of cupula & cilia generates nervous impulses)
  • Supporting cells
slide88

INFRARED PIT RECEPTORS of REPTILES

  • Labial pits
  • Found in pythons (Family Boidae); nerve endings lie at the bottom of several recessed labial pits
    • Permit detection of a mouse about 15 cm away
  • Loreal pits
  • Also called facial pits; can detect temperature changes of as little as 0.001 0C so it can detect prey several feet away
  • Present in snakes in the family Crotalidae (pit vipers)
slide89

Special visceral receptors

  • OLFACTION - involves receptors located in nasal passages; olfactory epithelium contains basal cells (replacement cells), supporting cells (secrete mucus), & olfactory receptor cells

Vomeronasal organs

  • Only in tetrapods but absent in most turtles, crocodiles, birds, some bats, primates, & aquatic mammals
  • Amphibians - recessed area off the main nasal cavity
  • Reptiles - separate pit to which tongue & oral membranes deliver chemicals
  • Mammals: isolated area of olfactory membrane within nasal cavity; well-developed in monotremes, marsupials, insectivores, & carnivores
slide90

2. GUSTATION- taste buds detect chemical stimuli

  • Consist of supportive & taste cells
  • Fish - widely distributed in roof, walls, & floor of pharynx; bottom feeders & scavengers (catfish & carp) have taste buds distributed over entire surface of head & body, especially on the barbels (‘whiskers’)
  • Tetrapods- taste buds restricted to tongue, posterior palate, & oral pharynx