Chapter 16,17: General Senses & Special Senses

The conscious or subconscious awareness of changes in the external or internal environment.

Sensation

The conscious interpretation of sensations

Perception

Are all sensations perceived?

No

Perceived vs Non-Perceived Sensations

Perceived: Things that happen on the outside of the body

Ex- All 5 senses

Non-Perceived: Things that happen inside of the body involuntary

Ex- Blood Pressure & Digestive Systems

What are the two sensory modalities

General and Special Senses

Somatic and Visceral senses are considered

General Senses

The Process of Sensation

1) Stimulation of the sensory receptor

2) Transduction of the stimulus

3) Generation of nerve impulses

4) Integration of sensory input

What type of nerve is used to detect pain, temperature, tickle, itch and some touch

Free Nerve Endings

What type of nerve is used to detect pressure, vibration, and some touch

Encapsulated Nerve Endings

Exteroceptors are located where and include what

Located: Near the body’s surface

Include- Hearing, vision, smell, taste, touch.

Interoceptors are located where

Located: Inside blood vessels, visceral organs, and nervous system.

Proprioceptors are located where and include

Located: Inside muscles, tendons, and inner ear.

Includes body position, muscle length, tension, position, movement of joints, and equilibrium

Mechanoreceptors detect what

Deformation, stretching or bending of cells.

Thermoreceptors detect what

Changes in temperatures

Nociceptors detect what

Painful stimuli resulting from physical or chemical damage.

Photoreceptors detect what

Changes in light

Chemoreceptors detect what

Chemicals in the mouth, nose, and body fluid

Osmoreceptors detect what

Osmotic pressure of body fluids

Are sensory receptors for somatic senses distributed unevenly throughout the body?

Yes

3 Locations of Somatic Sensations

1) Skin/Subcutaneous

2) Mucous membrane of mouth, vagina, and anus

3) Skeletal muscles, tendons, and joints

What are the 4 modalities of somatic sensations

1) Proprioceptive

2) Pain

3) Thermal

4) Tactile

Two types of RAPIDLY adapting touch receptors

1) Corpuscles of Touch (Meissner’s)

2) Hair Root Plexus

Encapsulated nerve endings located in the dermal papillae of hairless skin

Corpuscles of Touch (Meissner’s)

Free nerve endings wrapped around hair follicles

Hair Root Plexuses

Two types of SLOWLY adapting touch & pressure receptors

1) Type I Cutaneous Mechanreceptors (Merkel Discs)

2) Type II Cutaneous Mechanrecptors (Ruffini Corpuscles)

Flattened, free nerve endings that make contact with tactile epithelial cells of the stratum basale.

Ex- Holding an object for a longtime

Type I Cutaneous Mechanreceptors (Merkel Discs)

Encapsulated receptors located in the dermis, subcutaneous layer, and other tissues in the body.

Highly sensitive to skin stretching

Type II Cutaneous Mechanoreceptors (Ruffini Corpuscles)

Two types of vibration sensory receptors

1) Lamellated Corpuscles

2) Corpuscles of Touch

Nerve ending that respond to low-frequency vibrations

Nerve endings surrounded by a multilayered connective tissue capsule

Lamellated Corpuscles (Pacinian Corpuscles)

Nerve endings that respond to low-frequency vibrations

Corpuscles of Touch

Tickle and Itch sensations are a result of what type of nerve being stimulated

Free nerve endings

Where are cold receptors located?

Stratum Basale of epidermis

What type of temperatures are cold receptors stimulated by

50-95 F

Where are warm receptors located?

Deeper Dermis

What type of temperatures warm receptors activated by?

86-113

What type of temperatures stimulate pain receptors

Below 50 and above 113 F

Pain sensations utilize nociceptors which are found everywhere except the

Brain

Pain that occurs rapidly and is typically found just on the skin

Fast Pain

Pain that gradually increase intensity over seconds or minutes

Ex- Chronic, aching, or throbbing

Slow Pain

Sensations that allow us to know where our head and limbs are located and how they are moving

Proprioceptive Sensations

3 Types of proprioceptors

1) Muscle Spindles

2) Tendon Organs

3) Joint Kinesthetic Receptors

Proprioceptors that monitor the changes in skeletal muscle length and participate in stretch reflexes

Muscle Spindles

Proprioceptors that prevent muscle/tendon damage due to excessive tension.

Tendon Organs

Proprioceptors that are located within and around articular capsules of synovial joints.

Include- Free nerve endings, Type II Cutaneous Mechanoreceptors, & Small Lamellated Corpuscles

Joint Kinesthetic Receptors

Where is the primary somatosensory area located

The cerebral cortex

Sensory neurons that conduct impulses from somatic sensory receptors into the brain stem or spinal cord

First Order Neurons

Axons that conduct impulses from the brainstem or spinal cord of the thalamus.

Axons typically decussate (crossover)

Secondary Order Neurons

Conduct impulses from the thalamus to the primary somatosensory area of the cerebral cortex

Third Order Nuerons

What are the 3 main Somatic Sensory Pathways

1) Posterior Column-Medial Leminscus

2) Anterolateral

3) Trigenimothalamic

Primary somatosensory area of the parietal lobe is called

Postcenteral Gyrus

What areas of the postcentral gyrus have the most sensory receptors

Hands and face

Motor neurons that extend out of the spinal cord and brainstem and innervate skeletal muscles

Lower motor neurons

Motor neurons that

-Control lower motor neurons

-Control primary motor area

-Contain two motor pathways

1) Corticospinal pathways

2) Corticobulbar pathways

Upper motor neurons

What are the 5 special senses

1) Olfaction (Smell)

2) Gustation (Taste)

3) Vision

4) Hearing

5) Equilibrium

Smell and taste are both

Chemical senses

Where are all of the the olfaction sensory receptors located

Olfactory Epithelium

What are the the three kind of cells associated with olfaction

1) Olfactory receptor cells

2) Supporting cells

3) Basal cells

What are the first order neurons of the olfactory pathway

Olfactory receptor cells

Cells that provide physcial support, nourishment, and electrical insulation for olfactory receptor cells

Supporting cells

Stem cells that undergo mitosis to replace olfactory receptor cells

Basal Cells

Produce mucus

Olfactory (Bowman’s) Glands

Olfactory Neural Pathway

Nerves → Bulbs → Tracts → Area

Olfactory sensations are the only sensation that reach the cortex without first synapsing in the thalamus

Yes

What are some other tracts that olfactory axons project too

Limbic system and Hypothalamus

What are the 5 primary tastes

1) Sour

2) Sweet

3) Bitter

4) Salty

5) Umami

Where are gustatory receptors found

Taste buds

What are the three types of cells pertaining to gustation

1) Gustatory receptor cells

2) Supporting cells

3) Basal cells

The gustaroy receptors contain gustatory microvilli in the

Taste pore

What is the gustatory receptor’s cell’s lifespan

10 days

Why are papillae so important

They increase surface area and provide texture

Form of a V-shape row at the back of the tongue

Vallate Papillae

Mushroom shaped elevations found all over the toungue

Fungiform papillae

Grooves along the lateral edges of the tongue

Foliate papillae

Contain tactile receptors instead of taste buds. This increases the friction between tongue and food.

Filiform papillae

What 3 cranial nerves are involved with the sense of taste

-Facial (7)

-Glossopharyngeal (9)

-Vagus (10)

Facial Nerve (7)

Anterior 2/3 of the tongue

Glossopharyngeal Nerve (9)

Posterior 1/3 of the tongue

Vagus Nerve (10)

Epiglottis and pharynx

More than half of the sensory receptors in the human body are located in the eyes

Vision

Accessory Structure

-Shade the eyes during sleep

-Protect the eyes from excessive light

-Spread lubricating secretions over the eyeballs

Eyelids

Accessory Structures of the Eye

-Mucus membrane that lines the anterior part of the eye and the inner parts of the eyelids

-Protect and clean the eye

Conjunctiva

Accessory Structure of the Eye

-Produces and secretes tears

-Tears clean, moisten, and lubricate the eyeball

-Tears contain lysozymes

Lacrimal Apparatus

Accessory Eye Muscles

-Move the eyes in all directions

Extraocular Eye Muscles

Fibrous tunic (outer), Vascular tunic (middle), & Retina (inner) are the

3 layers of the eyeball

The fibrous layer consists of the

Cornea & Sclera

Clear, curved outer part that helps focus light on the retina. Mostly made up of epithelium.

-Anterior

Cornea

White, tough outer part that provides attachment for extraocular muscles. Mostly made up of dense connective tissue.

Sclera

What is the area called where the cornea and sclera meet up and drains the aqueous humor

Scleral Venous Sinus

The Vascular layer consists of the

-Choroid

-Ciliary body

-Iris

The highly vascularized layer that lines most of the internal surface of the sclera. Provides nutrients & melanin.

Choroid

Contains muscles that alter the shape of the lens

Ciliary Body

Colored portion of the eyeball suspended between the cornea and the lens

Iris

What do the muscles of the iris control the diameter of

Pupil

-Regulates the amount of light that enter the eyeball.

The Retina layer consists of

Pigmented & Neural layer

Melanin-containing epithelial cells that help absorb stray light rays.

Pigmented Layer

Contains photoreceptors (Rods & Cones)

-Rods → Night vision, black, white, and gray

-Cones → Colored and bright light vision

Neural Layer

Site where the optic nerve (CN II) exits the eyeball.

Optic disc

A small yellow spot located in the exact center of the posterior portion of the retina, at the visual axis of the eye.

Macula

A small depression in the center of the macula contains only cones. Area of highest visual acuity.

Fovea Centralis

Aqueous humor that nourishes the cornea and lens is stored in the

Anterior Segment