Ch. 18 - General Senses

Sensation

Process of stimulating a sensory neuron

Perception

Conscious awareness of the stimulus

General Sense(s)

When the receptor also functions as the sensory neuron

Special Sense(s)

When the receptor separate the neuron; exist in specialized sense organs

Receptor Field

Area of tissue where the receptor can detect a stimulus

Mechanoreceptors

Respond to physical distortion (pressure, bending, stretching)

Tactile Receptors

Mechanoreceptors in the skin; generally speaking deal with sense of touch

Unencapsulated

Dendrites are uncovered

Free Nerve Endings

Extend into the epidermis and detect fine touch

Root Hair Plexus

Dendrites wrap around hair follicle within the dermis and detect hair movement

Tactile Disc

Dendrites broaden into a disc where they contact Merkel cells; found in areas that we use to feel the environment

Encapsulated

Dendrites are associated with a protein capsule

Tactile Corpuscles

Coiled dendrites within a fibrous capsule; sensitive to light touch and vibrations

Lamellated Corpuscle

Large dendrite in a multilayer collagen capsule; found in the dermis; responds to string vibrations and deep pressure

Bulbous Corpuscle

Dendrites weave into parallel collagen fibers in a capsule; found deep in the dermis where they respond to stretching and distortion

Baroreceptors

Mechanoreceptors that monitor tension in tissue walls; free nerve endings branch into elastic fibers to detect degree of stretching

Proprioceptors

Mechanoreceptors that monitor position of components in the musculoskeletal system

Muscle Spindle

Dendrites of free nerve endings wrap around fascicles and monitor how much the muscle stretched

Golgi Tendon Organ

Dendrites of free nerve endings weave between the collagen of tendons to monitor how much the tendon stretched

Chemoreceptors

Respond to changes in pH level

Central Chemoreceptors

Found in medulla oblongata; detects pH changes within the cerebrospinal fluid

Peripheral Chemoreceptors

Found in aorta and carotids; detect pH changes in blood; use CN IX/X to send signal to medulla

Thermoreceptors

Free nerve endings in skin that detect temperature

Hot Receptors

Send more frequent impulses as temperature increases

Cold Receptors

Send more frequent impulses as temperature decreases

Nociceptors

Sense tissue damage which is perceived as pain; free nerve ending with a large receptor field

Mechanical Nociceptors

Sensitive to extreme deformation or mechanical stimulation

Thermal Nociceptors

Sensitive to very high/low temperatures

Chemical Nociceptors

Sensitive to the chemicals released by injured cells

Primary Somatosensory Cortex

Where all general senses are consciously perceived