Endocrine and nervous system · neuron is stimulated by another neuron or by the sense organs. •The impulse travels down the axons of Sensory neurons to the brain cells called Interneurons

Main Function:

This communication system controls and

coordinates functions throughout the body and responds to internal and

external stimuli.

Our nervous system

allows us to feel pain.

Consists of: brain, spinal cord, nerves and sense organs

Sense Organs: Eyes, Skin, Ears, Nose & Tongue

A nerve is an organ

containing a bundle

of nerve cells called

neurons.

Neurons carry

electrical messages

called impulses

throughout the

body. Picture shows hundreds of

severed neuron axons

cell

body

muscle

tissue

TYPICAL MOTOR

NEURON

Axon dendrite

synapse

cell body

Because neurons never touch, chemical signalers called neurotransmitters must travel through the space called synapse between two neurons.

Neurotransmitters

Synapse (gap)

The message

is transferred

when RECEPTORS receive neurotrans-mitters.

(pink

spheres)

Parts of a Neuron 1. Cell body: contains nucleus & most of the

cytoplasm

2. Dendrites: projections that bring impulses into the neuron to the cell body.

3. Axon: long projection that carries impulses away from cell body

1

3 2

Sensory Neuron

Interneuron

Motor Neuron

Sensory Neuron

Interneuron

Motor Neuron

Muscle Contracts

Synapse

Synapse

Synapse

Sensory

Neuron

carry impulses from

sense organs to

spinal cord & brain

Fun Fact:

Where can the

largest cells in the

world be found?

The giraffe’s sensory and

motor neurons! Some

must bring impulses from

the bottom of their legs

to their spinal cord

several meters away!!

Interneuron

-processes impulses

in brain and spinal

cord

- connect sensory and

motor neurons

Motor Neurons

carry impulses from the

brain & spinal cord to

muscles & glands

Axon End

Axons branching out

to muscle fibers

• Nerves work together with muscles for

movement. An impulse begins when one

neuron is stimulated by another neuron or

by the sense organs.

• The impulse travels down the axons of

Sensory neurons to the brain cells called

Interneurons.

• The brain will then send an impulse

through motor neurons to the necessary

muscle or organs, telling it to contract.

A reflex is an

involuntary

response that is

processed in the

spinal cord not

the brain.

Reflexes protect

the body before

the brain knows

what is going on.

Reflex Arc

brain

Spinal Cord

Cerebellum

Cerebrum

Medulla Oblongata

Consists of: Brain and Spinal Cord

Cerebrum Voluntary or conscious activities of

the body-learning, judgment

Cerebellum Coordinates and balances the

actions of the muscles

Medulla Oblongata

(Brain Stem)

Controls involuntary actions like

blood pressure, heart rate,

breathing, and swallowing

Spinal Cord

The main communications link

between the brain and the rest of

the body

Consists of:

Sensory division

and Motor

division

-includes all

sensory neurons,

motor neurons,

and sense organs

Anatomy and Physiology

• Ophthalmology (Ophth) is study of the eye

• Eyeball

– Organ of sight

– Transmits external image using sensory

impulses via optic nerve to brain

– Brain translates sensory impulses into image


• External structures important for vision

– In addition to eyeball

– Eye muscles

– Eyelids

– Conjunctiva

– Lacrimal apparatus

Click here to view an animation on the anatomy of the eye. Back to Directory

Eye Anatomy Animation

http://cite.nwmissouri.edu/ic/medterm/ch13/media/3d_eye.htm

The Eyeball

• Composed of three layers:

– Sclera

– Choroid

– Retina

Sclera

• Outermost layer

• Tough protective

layer

• Another term for

sclera is white of

eye

• Anterior portion is

cornea

Medical Terminology: A Living Language, Fourth Edition Bonnie F. Fremgen and Suzanne S. Frucht

Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458

All rights reserved.

Figure 13.1 – The internal structures of the eye.

Cornea

• Anterior portion of

sclera

• Clear, transparent

• Allows light to

enter

• Bends, or refracts,

light rays





Choroid

• Middle layer

• Provides blood

supply for eye

• Anterior portion:

– Iris

– Pupil

– Ciliary body





Iris and Pupil

• Iris

– Colored portion of

eye

– Smooth muscle that

changes size of

pupil

• Pupil

– Opening in center

of iris

– Allows light to

enter into eyeball

Ciliary Body and Lens

• Lens

– Behind iris

– Not actually part of

choroid layer

– Attached to ciliary

body

• Ciliary body

– Pulls on edge of

lens

– Changes shape of

lens so it can focus

light onto retina





Retina

• Contains sensory

receptor cells that

detect light rays

• Rods

– Active in dim light

– See gray tones

• Cones

– Active only in

bright light

– Color vision





Retina

• Macula lutea

– Area of retina

where image forms

• Fovea centralis

– Depression in

center of macula

lutea

– High number of

cones

– Point of clearest

vision





Optic Disk

• Point where the optic nerve leaves eyeball

• Retinal blood vessels enter and leave

through optic disk

• No rods or cones

– Results in blind spot in each eye’s field of

vision




Figure 13.2 – Photograph of the retina of the eye. The optic disk appears yellow and the retinal arteries radiate out from it.

Eye Fluids

• Aqueous humor

– Watery fluid

– Located between cornea and lens

• Vitreous humor

– Semi-solid gel

– Located between lens and retina

Muscles of the Eye

• Six muscles that connect eyeball to skull

– 4 rectus muscles pull straight

– 2 oblique muscles pull on an angle

• Contract in combination to change direction

in which each eye is looking




Figure 13.3 – The external eye muscles.

Eyelids

• A pair cover each eyeball

• Provide protection from foreign particles,

injury, sun, and trauma

• Both upper and lower edges have eyelashes

or cilia that protect eye from foreign

particles

• Sebaceous glands located in eyelids secrete

a lubricating oil onto surface of eyeball





Conjunctiva

• A mucous membrane

• Forms continuous covering on underside of

each eyelid and across anterior surface of

each eyeball

• Protects eyeball





Lacrimal Apparatus

• Lacrimal gland

– Located under outer upper corner of each eyelid

– Produces tears

– Tears wash and lubricate anterior surface of eyeball

• Lacrimal ducts

– Located in inner corner of eye socket

– Collect tears

– Drain into nasolacrimal duct

– Ultimately drain into nasal cavity




Figure 13.5 – The structure of the lacrimal apparatus.

How We See

• Light rays pass

through:

– Cornea

– Pupil

– Aqueous humor

– Lens

– Vitreous humor

• Then strike retina

– Stimulating rods

and cones




Figure 13.6 – The path of light through the cornea, pupil, lens, and striking the retina.

How We See

• Upside-down

image forms on

retina

• Optic nerve

transmits this image

to brain

• Brain turns upside-

down image into

right-side up image




Figure 13.7 – The image formed on the retina is inverted. The brain rights

the image as part of the interpretation process.

Vision

• Vision requires four mechanisms:

– Coordination of external eye muscles so that

both eyes move together

– Correct amount of light admitted by pupil

– Correct focus of light upon retina by lens

– Optic nerve transmitting sensory images to

brain




Figure 13.9 – Hyperopia (farsightedness). In the uncorrected top figure, the image would come into focus behind the retina, making the image on

the retina blurry. The bottom image shows how a biconvex lens corrects this condition.




Figure 13.10 – Myopia (nearsightedness). In the uncorrected top figure, the image comes into focus in front of the lens, making the image on the retina blurry. The bottom image shows how a biconcave lens corrects

this condition.

Eyeball Pathology

cataract damage to lens causing it to become

cloudy

glaucoma chronic increase in intraocular pressure;

results in atrophy of optic nerve

macular

degeneration

deterioration of macula lutea area of

retina

The Ear at a Glance

• Function of the Ear

– Contains sensory receptors for hearing and

equilibrium (balance)

The Ear at a Glance

• Structures of the Ear

– Auricle

– External ear

– Middle ear

– Inner ear





• Otology (Oto) is study of the ear

• Audiology is study of hearing disorders

• Ear responsible for two senses:

– Hearing

– Equilibrium or sense of balance

• Sensory information carried to brain by

vestibulocochlear nerve

– Cochlear nerve – hearing information

– Vestibular nerve – balance information

Click here to view a video on audiology. Back to Directory

Audiology Video

http://cite.nwmissouri.edu/ic/medterm/ch13/media/no_intro_Audiology.htm

The Ear

• Ear is subdivided into three regions:

– External ear

– Middle ear

– Inner ear

Click here to view an animation on the anatomy of the ear. Back to Directory

Ear Anatomy Animation

http://cite.nwmissouri.edu/ic/medterm/ch13/media/3d_ear.htm

External Ear

• Auricle or pinna

– Only portion visible

– Captures sound

waves

– Directs them

through external

auditory meatus

External Ear

• Auditory canal

– Sound moves along canal

• Cerumen

– Produced by oil glands in auditory canal

– Oily wax slowly flows out of ear canal removing dirt that has stuck to it

External Ear

• Tympanic

membrane

– Commonly called

eardrum

– Sound waves strike

membrane

– Causes it to vibrate

• Tympanic

membrane

separates external

ear from middle ear




Figure 13.14 – The internal structures of the outer, middle, and inner ear.

The Middle Ear

• Small cavity

• Located in temporal

bone of skull

• Contains three tiny

bones called

ossicles

– Malleus

– Incus

– Stapes





Ossicles

• Tympanic

membrane vibrates

incus

• Vibrations amplify

as they move from

one ossicle to next

• Stapes transmits

vibration to oval

window

– Start of inner ear




Figure 13.15 – Close-up view of the ossicles within the middle ear.

Eustachian Tube

• Also called auditory tube

• Connects nasopharynx with middle ear

• Opens with each swallow

• Equalizes pressure between middle ear

cavity and atmospheric pressure





The Inner Ear

• Labyrinth

– Cavity within

temporal bone

– Houses inner ear

• Contains sensory

organs

Sensory Organs of Inner Ear

• Hearing

– Cochlea

– Organs of Corti

• Equilibrium

– Semicircular

canals

– Utricle

– Saccule





How We Hear

• Sound waves travel down external auditory

canal, strike eardrum

• Eardrum vibrates

How We Hear

• Ossicles conduct vibrations across middle

ear from eardrum to oval window

• Oval window movements initiate vibrations

in fluid that fills cochlea

How We Hear

• Fluid vibrations strike hair cells, bending

small hairs and stimulating nerve endings

• Nerve ending sends electrical impulse to

brain on cochlear portion of

vestibulocochlear nerve




Figure 13.16 – The path of sound waves through the outer, middle, and inner ear.

Click here to view an animation on inner ear anatomy. Back to Directory

Inner Ear Anatomy Animation

http://cite.nwmissouri.edu/ic/medterm/ch13/media/ear.htm

• Main Function:

It releases hormones into the blood to

signal other cells to behave in certain

ways. It is a slow but widespread form

of communication.

Endocrine glands

Release hormones into

the bloodstream.

Hormones are chemicals

released in one part of the

body that travel through

the bloodstream and

affect the activities of cells

in other parts of the body.

Consists of:

Pituitary Gland

Function: It secretes nine hormones that directly regulate many body functions and controls functions of other glands.

Disorders: To much growth hormones (GH) in early childhood can result in a condition called gigantism. To little GH can result in Pituitary Dwarfism.

Robert Wadlow

http://www.gigantism.com/david-goliath.html

Thyroid Gland • Function: plays a major role in

regulation the body’s metabolism.

• Disorders: If the Thyroid Gland produces to much Thyroxin, it can cause a condition known as Hyperthyroidism. If to little thyroxin produces it is called Hypothyroidism.

Pancreas • Function: The Insulin

and Glycogen in the Pancreas help to keep the level of glucose in the blood stable.

• Disorders: When the Pancreas fails to produce or properly use Insulin, it can cause a condition known as Diabetes Mellitus.

Adrenal Gland

• Functions:

-The adrenal glands release Adrenaline in the body that helps prepare for and deal with stress.

-Also regulates kidney function.

Ovaries

• Functions:

– Pair of reproductive organs found in women that produce eggs.

– Also secrete estrogen and progesterone, which control ovulation and menstruation.

Testes

• Functions:

– Pair of reproductive glands that

produces sperm.

– Also secrete Testosterone to give

the body its masculine

characteristics.

Interaction of Glands

The hypothalamus is located in the brain and controls the release of hormones from the pituitary gland. It is an important link between the endocrine and nervous systems.

http://www.biocfarm.unibo.it/aunsnc/images/3D%20Obje

cts/Hypothalamus.gif

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Documents

Endocrine and nervous system · neuron is stimulated by another neuron or by the sense organs. •The impulse travels down the axons of Sensory neurons to the brain cells called Interneurons