Administration



Somatic and Special Senses

Communicating with the world around us

The two major groups

Somatic senses

Touch, pressure, temperature and pain

Found in the skin and the deeper tissues

Structurally simple

special senses (sensory)

Smell, taste, hearing, vision, and equilibrium

Found in specialized organs for that sense

Structurally complex

Receptors

Types of receptors

Chemoreceptors

Stimulated by changes in the chemical concentration of substance

Pain receptors

Stimulated by tissue damage

Thermoreceptors

Stimulated by changes in temperature

Mechanoreceptors

Stimulated by changes in pressure and movement

Photoreceptors

Stimulated by light

The sensation

Sensation occurs when the brain interprets the sensory impulses.

Different sections of the brain interpret the signals, dependent on what type of receptor they come from

The cerebral cortex then causes the feeling to seem to come from the area of the stimulated receptor.

This is called projection

This allows us to know what hurts in most cases

Did you adjust?

There is noise all around you, things pressing against you... do you always feel or hear them?

The ability for you mind to ignore unimportant stimuli is called sensory adaptation

Receptors become unresponsive – peripheral adaptation

Inhibition along the CNS leading to the sensory regions of the cerebral cortex - central adaptation

Somatic Sense

Associated with the skin, muscles, joints, and the viscera

Three main types

Touch and pressure

Temperature

Pain

Touch and pressure

Comes from three different types of receptors

They detect mechanical forces that deform or displace tissue

They are:

Free nerve endings – extend between the epithelial cells

Meissner's corpuscles – small oval masses of flattened connective tissue

Abundant in the hairless regions of the body

Respond to light touch

Pacinian corpuscles – large structures in the deeper subcutaneous fissures and muscles tendons and ligaments

Respond toe heavy pressure and deep pressure

Temperature Senses

Depends on two types of free nerve endings in the skin

Warm receptors

Sensitive to temps above 25˚C (77˚F) and are unresponsive with temps more than 45˚C (113˚ F)

Then the pain receptors kick in and you feel a burning sensation

Cold receptors

Sensitive to temps between 10˚C(50˚ F) and 20˚ C (68˚ F)

Below 10˚ C produces a freezing sensation and pain

Pain

Free nerve endings

Spread through the skin and internal tissues

Exception – the brain, it has none

Protect the body

Is stimulated by tissue damage

How this does it is not well understood

Don't adapt well, so pain can be persistent

Visceral Pain

In the vicera, you typically need a widespread stimulation to get a response.

So, a small cut in a region of the intestines = no pain

Intestinal cramping = pain

Visceral pain feel like it is coming from some other part of the body

Called referred pain

Tends to be caused by the sharing of neural pathways that go to the skin as well as the viscera

Pain nerve fibers

Two main types

Acute

Thin and myelinated , fast impulses

Sensation of sharp pain that seldom continues after the stimuli has gone. Easy to pin point location

Typically only from skin

Chronic

Thin and unmyelinated, slow impulses

Dull aching sensation, difficult to pinpoint, continuous

From both skin and deeper tissues

Special Senses

Have large complex sensory organs in the head

Smell – olfactory organs

Taste – taste buds

Hearing – ears

Equilibrium – ears

Sight – eyes

Sense of smell

Olfactory organs

Are located in small patches

Covers the upper nasal cavity, nasal conchea, and portions of the nasal septum

Yellowish brown masses of epithelium

Composed of olfactory receptors

a type of chemoreceptors

Chemicals dissolved in liquids stimulate them

Neurons surrounded by columnar epithelial cells

Have cilia like ending that harbor 400 types of protein receptors

Detects odorant molecules

Smell and taste are closely related

Sense of taste

Taste buds - chemoreceptors

Where are they

Approx 10,000 are located on the tongue

Located on papillae

1,000 are scattered about the roof of the mouth and the walls of the throat.

Composed of

modified epithelial cells called taste cells (gustatory cells)- the receptors

50-150 of these/ taste bud

Taste pore – hole at the top of the spherical shaped bud

Taste hair – protrude from taste cell into the the taste pore

Nerve fibers woven about the cells

Taste sensations

The tastes

4 primary

Sweet, Sour, Salty, Bitter

All taste all of these, but at different levels

Therefore there are areas of concentration of the flavors

Others sometimes recognized

Alkaline, metallic, umami (MSG)

Some taste stimulate other nerves

Chile peppers and ginger – pain receptors

Chile peppers (capsaicin)– warm receptors

Taste is a combination of the different nerves stimulated, texture, temperature, and smell

Sense of hearing

Three zones

Outer ear

Middle ear

Inner ear

Outer ear

Three parts

Auricle (pinna)– outer funnel-like structure

Collects sound waves

External ascoustic meatus (external auditory canal) – s-shaped tube that leads inwards for about 2.5 cm

Tunnels/ directs to the eardrum

Tympanic membrane (eardrum) – semitransparent membrane covered by a thin layer of skin on the outside and a mucous membrane on the inside.

Oval margin and cone-shaped that attaches to the malleus (mallet)

Vibrates when sound waves hit it causing the malleus to move

Middle Ear

AKA Tympanic Caviry

Air filled space in the temporal bone

Contains 3 small bones (auditory ossicles)

Malleus (mallet), Incus(anvil) ,Stapes (stirup)

Attached to the cavity by small ligaments and the oval window (stapes)

Covered by a mucous membrane

The bones transmits the sound waves from the eardrum to the oval window

Also help to amplify the sound waves because the size of the eardrum (larger) and the oval window (smaller)

Middle Ear connection

Auditory tube (Eustachian tube)

Connects the middle ear with the nasopharynx

Helps to regulate the air pressure in the middle ear.

Must be the same as on the outside of the eardrum

If a sudden change happens in external pressure, the adjustment will sound like a pop

Inner ear

Entire region is called the Labyrinth

Divided into two main areas

3 semicircular canals – used in equilbrium

Cochlea – used to hear

Two main parts

Osseous labyrinth – tunnel through the temporal bone

Secrets a fluid called perilymph

Membranous labyrinth – membrane inside of the bone tunnel

Secrets endolymph

Cochlea

The oval window allows sound vibrations into the cochlea. The stapes pulls and pushes on the oval causing the lymphs to move

This movement causes waves through out the cochlea

Has a bony core with the bony shelf that winds about the core in a spiral

The organ of Corti – where the hearing receptors stretches from the apex to the base of the cochlea

Hair like cells detect the changes in the lymph

Two levels of sensitivity

Equilibrium

2 types

Static equilibrium

Sense the head and maintain stability and posture when head and body are still

Dynamic equilibrium

Detects motion and aids in maintaining balance when head and/or body moves or rotates

Static Equilibrium

Organs are located in the vestibule

A bony chamber in between the cochlea and the semicircular canals has two chambers

Utricle and saccule

Macule – structures in the chambers that contain the sensory receptors (hairs) and gelatinous material, and otoliths (CaCO4)

Hairs project into a mass of gelatinous material. When the gelatinous material moves and bends the hairs, the brain is told of the change of position of the head

Dynamic Equilibrium

Organs are in the semicircular canals

Lie at right angles to each other, corresponding to a different anatomical plane

Crista ampullaris

Contains sensory hair cells and supporting cells

Inside a gelatinous mass called cupula

Responds to rapid turns of head or body

Gelatinous material doesn't move, but hair cells do.

Sense of sight

Organs

Eyes – has the visual receptors

Accessory organs to help out

The Accessories

The orbital cavity

Pear shaped cavity in the skull

Has fat, blood vessels, nerves, and connective tissues

Eyelid

4 layers

Skin, Muscle, Connective tissue, conjuntiva

The conjunctive is a mucous membrane that lines the inner surface of the eyelid and the fold to cover the anterior surface of the eyeball, except the center section

Another accessory

Lacrimal apparatus

Lacrimal gland - produces tears

Located in the orbit (eye socket)

Contains lysozyme – an antibacterial agent

Series of ducts-

Lateral and medial ducts empty into the lacrimal sac which then goes to the nasolacrimal duct

Last one

Extrinsic Muscles

6 of them, moves the eyes in specific directions

Superior rectus – upward, towards midline

Inferior rectus- downward, towards midline

Medial rectus- towards midline

Lateral rectus- away from midline

Superior oblique- downwards, away from midline

Inferior oblique – upward, away from midline

The eye

Three layers

Outer layer

Sclera – white of the eye

Optic nerve – attached to the back of eye

Cornea – clear window

Middle layer

Choroid coat -honeycombed, lots of blood vessels, melanocytes to absorb excess light

Ciliary body – extends from choroid coat to the front of the eye, forming an internal ring

Lens – transparent, focus light on retina

Iris – extends form ciliary body to the pupil, muscle

Aqueous humor – liquid from the ciliary body to the cornea

Pupil – hole in the eye that lets light in.

Last layer

Inner layer

Retina – contains the visual receptors

Coats inner surface of the eye, end just behind the ciliary body

Rods- see in greyscale

Cones – see color; three types – red, green , blue

Fovea centralis and Macula Lutea

Macual is the central region of the retina

Fovea – depression in the middle that provides the clearest images

Optic Disc

Where the nerve fibers go in the optic nerve

The blind spot in the eye

Vitreous humor

Jelly like fluid inside the eye

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