Nervous System of the Frog

By:Group 636 Marjorie Polintan37 Miguel Quiambao38 Inna Karla Ramos

39 James Redulla40 Patricia Anne Reyes

41 Zyril Mae Reyes42 Claudine Roxas

Nervous System• Serves as reception of stimuli• Conduction of impulses• Coordination and integration of the various

functions of the organs

Three Divisions of the Frog’s Nervous System (according to morphology):

1. Central Nervous System– also known as the Cerebro-spinal Nervous System– includes the brain and the spinal cord– serves as the great center of communication between

the principal sense organs and the rest of the body– divided into five major parts, namely:

• Telencephalon• Diencephalon• Mesencephalon• Metencephalon• Myelencephalon

2. Peripheral Nervous System– includes the ten pairs of cranial nerves (from the

brain) and ten pairs of spinal nerves (from the spinal cord)

– connects the central nervous organs to the receptors and effectors of the body

3. Symphathetic Nervous System– consists of two slender nerve trunks or cord, each with

a chain of ganglia on either side of the spinal column– helps deliver information to the body about

impending danger– responsible for the fight-or-flight response

I. Central Nervous System (CNS)

Five Major Divisions of the Frog BrainA

DIVISION BODY PARTS FUNCTIONS

1.Telencephalon- located in the anterior portion of the brain and rostral to the midbrain •Paired olfactory lobes

- for the sense of smell•Cerebral hemispheres-seats of associative memory where the lateral (first and second)ventricles or cavities are located

•Determines Intelligence •Determines Personality •Interpretation of Sensory Impulses •Motor function (movement)•Planning and Organization •Memory•Sense of Smell •Touch Sensation •Emotion

2.Diencephalon (or Thalamencephalon)- located between the optic lobes behind and posterior to the cerebral hemispheres

• Optic chiasma • Infundibulum•Ventricle III•Posterior pituitary gland •Pineal body

•Directs Sense Impulses Throughout the Body •Equilibrium (balance)•Eye Movement; Vision •Hearing •Respiration •Salivation, Swallowing •Smell, Taste

FUNCTIONS BODY PARTS FUNCTIONS

3.Mesencephalon- also known as the “midbrain”, located between the forebrain and hindbrain

Optic lobes- contain the optic ventricles, which communicate with each other and with the third and fourth ventricles by a small aqueduct of Sylvius

Controlling Responses to Sight

Eye Movement Pupil Dilation Body Movement Reflex Activities of the

Spinal Cord

4.Metencephalon- located below the posterior portion of the cerebrum and above the medulla oblongata

Cerebellum- small dorsal transverse fold

Balance Cardiac Reflexes Circulation Fine Muscle Movement Muscle Tone

maintenance Sleep

5.Myelencephalon- inferior portion of the brainstem

Medulla oblongata- narrows posteriorly to become the spinal cord

Respiratory and Circulatory Functions

Breathing Conduction Pathway for

Nerve Tracts Digestion Heart Rate Swallowing Sneezing

Other parts of the CNS:• Choroid Plexuses- secretes the cerebro-spinal fluid

• Foramen of Monro- a narrow passage that joins the lateral ventricles with the 3rd ventricles

• Aqueduct of Sylvius- joins the 3rd ventricle with the 4th ventricle

• Cerebro-spinal Fluid- serves as a protective liquid cushion and

helps nourish the central nervous organs • Spinal Cord- short and somewhat flattened; posterior

prolongation of the brain; surrounded by meninges; extends from the medulla oblongata to the filum terminale

• Filum Terminale- posterior tapering portion located in the urostyle; presents two enlargements, namely:

• Brachial Enlargement- associated with the nerve supply to the forelimbs

• Lumbar Enlargement or Sciatic Enlargement- associated with the nerve supply to the hindlimbs

• Meninges- two connective tissue membranes which surrounds the spinal chord

• (Outer) Dura Mater- adhering to the bone• (Inner Vascular) Pia Mater- adhering to the nervous

tissue• Vascular Arachnoid- located beneath the dura mater;

forms the middle layer of the meninges (for higher vertebrates)

II. Peripheral Nervous System (PNS)

2 Divisions of the Peripheral Nervous System

A.Cranial Nerves – consists of 10 pairs of nerves (left,right)-extending from the lateral surfaces of the

brain to the parts of the body B.Spinal Nerves- consists of 10 pairs of nerves (left,right)

• Arise from the spinal cord• Distributes to the limbs and trunk.• emerge between vertebrae • each spinal nerve is attached to the spinal cord by 2

roots (dorsal sensory root and ventral motor root)

A. The 10 Paired Cranial Nerves 1. Olfactory

Function/Type: Sensory nerves for smellLocation: walls of nasal chambers

2. Optic Function/Type: Sensory nerves for visionLocation: retina of the eyes

3. Oculo-MotorFunction/Type: Motor nervesLocation: 4 muscles of the eye namely (superior

rectus,inferior rectus,medial rectus,inferior oblique muscles)

4. TrochlearFunction/Type: Motor nervesLocation: superior oblique muscle of the eye

5. TrigeminalFunction/Type: sensory and motor nervesLocation: muscles of the jaws, skin of the face,

mouth and the tongue6. Abducens

Function/Type: motor nervesLocation: lateral or external rectus muscle of the eye

7. FacialFunction/Type: motor and sensory (mostly motor)Location: muscles of the face and throat

8. AuditoryFunction/Type: Sensory nerves for hearing and equilibriumLocation: inner ear

9. GlossopharyngealFunction/Type: Sensory and motor nervesLocation: floor of the mouth,tongue and pharynx

10. Vagus or PneumogastricFunction/Type: Sensory and Motor nervesLocation: larynx,lungs,heart,esophagus,stomach and small

intestine.

*There are 2 additional cranial nerves in man namely the

accessory spinal and hypoglossal nerves

Some Mnemonics to help remember the names and order of the cranial nerves..

• On Old Olympus' Towering Top A Finn And German Viewed • Oliver the optimistic octopus trots triumphantly about facing

audiences glossily vaguely • OOO Truly There Are Five Absolutely Gorgeous Vixen

Some mnemonics to remember the types of cranial nerves..

• Some Say Money Matters, But My Brother Says Big Brains Matter More.

• Sally Sells Mega Monkeys, But My Brother Sells Bigger Better Mega Monkeys.

• Some Stars Make Money, But My Brother Says Bugs Bunny Makes More.

B. The 10 Paired Spinal Nerves

1st spinal nerve

2nd spinal nerve

3rd spinal nerve

4th spinal nerve5th spinal nerve6th spinal nerve

-Unite to form the Brachial Plexus to the shoulder and forelimb region

-Supply the skin and muscles of the abdominal wall

7th spinal nerve8th spinal nerve9th spinal nerve*

10th spinal nerve

-forms the Sciatic / lumbo-sacral plexus to the hindlimb

*the 9th spinal nerve is the largest and is known as the sciatic nerve

-Distributed to the urinary bladder, cloaca and oviducts

III Sympathetic Nervous System (SNS)• In man, Sympathetic and parasympathetic comprise

Autonomic Division.• It is branch of the autonomic nervous system• It is always active at a basal level ( sympathetic tone) • becomes more active during times of stress (fight-or-

flight response)• operates through a series of interconnected neurons. • frequently considered part of the peripheral nervous

system (PNS), although many lie within the central nervous system(CNS).

HISTOLOGY OF THE SPINAL CORD(mammalian)

• The spinal cords the reflex activities of the animals but which may be checked or modified by impulses from the brain.

• In the cross sections, the spinal cord shows 2 distinct areas:

1. Gray matter – made up of nerve cell bodies, portion of the dendrites and axons, and the unmyelinated fibers.

2.White matter- composed of myelinated fibers

• Neuroglia cells and their processes bind together and support the nervous elements in both areas.

• Canalis Centralis – located near the center of the gray matter -lined with a single layer of the Epithelial ependymal cells

• At the sides of the gray matter, dorsal and ventral horns or cornua are produced.

• Gray Commisures connects the gray matter on the two sides.• Oblique crossings of the medullated fibers form the white

commisures.• Ventral fissure separates the right and the left columns of the

white matter.

• Dorsal Septum, composed of Pial tissues, extends from the base of this sulcus almost to the gray matter

• The deep indentation at the bottom of the cord is the Ventral Fissure

Histology of the eye

• eye- organ of visionDivided in to 2 segments:a. aqueous humor-anterior segment-contains watery fluidb. vitreous humor-posterior segment (adapted to the

reception/transmission of images)-more viscuous/jelly like fluid

• Outer coat-opaque,no light can enter-separated from the anterior segment by the

crystalline lens and suspensory ligament.

The three coats of the eye..1.Sclera2.Choroid3.retina

1. Sclera –protective ,outer,thick fibrous coat-tendons of eye are attached to it-continuous with the transparent cornea

that permits light rays to enter

2. Choroid-vascular layer between the sclera and retina

-concerned with nutrition of ocular tissues-presence of numerous blood vessels-anterior portion:ciliary body and iris

(mechanism for the accomodation of the refraction of the eye,projects over the anterior portion of the lens)

• Pupil-central opening -Regulates the amt of light entering the

eye• Iris- colored porion of the eye

3. Retina- innermost photosensitive coat.-contains receptors (rods,cones)-first link of the nervous pathways

conveying impulses through the optic nerve of the brain.

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