Chapter 19: Senses General and Speacial

What is the relationship b/w the size of a receptive field and the ability to identify the exact location of a stimulus?

An inverse relationship.

If the receptive field is small, precise location of stimulus/sensitivity is easily determined.

BIG receptive field makes localization of stimulus/sensitivity harder to determine.

Tonic Receptors

Charateristics

• Limited adaptation

• Continuously generate nerve impulses

• Slowly decrease the number of impulses relayed to the CNS

Examples of Tonic Receptors

• Inner Ear (head position)

• Proprioceptors in joints and muscles (provide info of where your body is in space)

• ALL pain receptors

Phasic Receptors

Characteristics

• rapid adaptation to constant stimulus

• Only generate nerve impulses in response to new/changing stimulus

• Quickly decrease the number of nerve impulses relayed to CNS

Phasic Receptors (Examples)

• Deep pressure receptors that sense the increased pressure (when we first sit down on a chair, put ring back on after not using it, putting glasses on for the first time)

• Tactile Receptors in skin

Special Senses (5)

Olfaction

Gustation

Vision

Hearing

Equilibrium

Somatic receptors (location)

Skin and mucous membranes

Visceral Receptors (location)

Within walls of viscera and blood vessels

Stimulus Origin Receptors

1. Proprioceptors

2. Interoceptors

3. Exteroceptors

Exteroceptors

Detect stimuli in external environment

Interoceptors

Detect stimuli within the body

Proprioceptors

Detect stimuli within joint, skeletal muscles, and tendons that sense body or limb movement

Receptors based on MODALITY

1. Chemoreceptors

2. Mechanoreceptors

3. Thermoreceptors

4. Phororeceptors

5. Nociceptors

Chemoreceptors

Detect chemicals dissolved in fluid

• taste receptors

• Receptors in blood vessels that monitor hydrogen ions

• Inhaled chemicals in air

Mechanoreceptors

Detect physical deformation of the plasma membrane due to touch, pressure, vibration stretch

Subtypes

• Baroreceptors

• Proprioceptors

• other specialized cells (hair in cochlea of the ear)

• Tactile receptors in skin

Thermoreceptors

Detect change in temperature

• sensory receptors w/i skin and hypothalamus

Photoreceptors

Detect change in light intensity, color, movement

• eye

Nociceptors

Detect painful stimuli

• pain receptors in almost all organs

Referred Pain

Occurs when impulses from visceral are perceived as originating not from the organ but in dermatomes of the skin.

Numerous cutaneous and visceral sensory neurons conduct nerve impulses through the same ascending tracts

Examples of Referred Pain

• Appendix pain may be felt in umbilical region of the skin

• Heart attack may feel pain along the medial side of the left arm

• Kidney and ureter pain may feel pain in he groin region

• Urinary bladder may be felt in medial buttocks region

List the 3 unencapsulated tactile receptors.

1. Free Nerve Ending

2. Root Hair Plexus

3. Tactile Disc

Free Nerve Endings

Where: found in deep epidermus and papillary layer of the dermis

Function: Detect temp, pain, some detect light touch and pressure

Phasic or Tonic

Root Hair Plexus

Where: Reticular Layer of the dermis

Function: detects movement of the hair

Phasic

Tactile (Merkel) Disc

Where: stratum basale of epidermis (small receptive fields)

Funct: detects light touch, texture, shape

Tonic

4 Encapsulated Tactile receptors

1. Bulbous Corpuscle (Ruffini)

2. End Bulb (Krause)

3. Lamellated Corpuscle (Pacinian)

4. Tactile Corpuscle (Meissner)

Bulbous Corpuscle (Meissner)

Where: found in dermis and subcutaneous layer and in joint capsules

Function: detects continuous deep pressure and skin distortion

Tonic

End Bulb

Where: mucous membranes of oral cavity, nasal cavity, vagina, and anal canal

Function: detects light pressure and low frequency vibration

Tonic

Lamellated Corpuscle (Pacinian)

where: found in dermis, subcutaneous tissue, synovial membranes and some viscera

Functions: coarse touch, detects deep pressure and high frequency vibrations

Phasic

Tactile Corpuscle (Meissner)

where: found in dermal papillae especially in lips, palms, eyelids, nipples, genitals

Function: detects discriminative touch to determine textures and shapes, light touch

Phasic

What do gustoru cells detect?

Taste

Describe the 3 tunic of the eye

Fibrous

• cornea

• Sclera

Vascular

• choroid

• Ciliary body

• Iris

Retina

• pigmented layer

• Neural layer (photoreceptors, rods, cones, bipolar cells, ganglion cells)

Describe how the ciliary muscles cause he lens to change shape

When ciliary muscles RELAX, the ciliary body moves away from the lens, so the tension on the suspensory ligaments increases

→ causes the lens to flatted → necessary for far vision

When the ciliary muscles CONTRACT, the ciliary body moved closer to the lens, tension in ligaments decrease

→ cause the lens to become more spherical → necessary for close vision (accommodation)

Pathway of light through the eye

Cornea, anterior cavity, pupil, posterior cavity, retina, optic nerve

Pathway of sound waves through the ear

Auricle

External Acoustic meatus

Tympanic Membrane

Malleus

Incus

Stapes

Oval Window

Cochlea

Cochlear portion of Vestibulocochlear nerve