Bio 168 chapter 13

3 ways to classify sensory receptors

1. by the type of stimulus they detect 2. by their body location 3. by their structural complexity

Which of the receptor types might function as a nociceptor?

A Nociceptors respond to potentially damaging stimuli, such as noxious chemicals or extremes of temperature or pH. Nociceptors are generally associated with free nerve endings of specialized neurons.

Spinal nerves are all classified as __________.

All 31 pairs of spinal nerves are mixed nerves; they carry both afferent (sensory) impulses toward the CNS and efferent (motor) impulses away from the CNS.

Which of these receptor types functions as an exteroceptor?

All of the structures illustrated are sensitive to stimuli arising outside the body.

Amber, your 2-year-old patient, has no pain receptors (a condition called congenital insensitivity to pain). What problems would you expect Amber to have over the course of her life?

Amber is likely to suffer from numerous undetected injuries. These could lead to infection (and possibly amputation)

Which type of sensory receptor allows us to feel an insect landing on our skin?

Mechanoreceptors respond to mechanical force such as pressure, vibration, stretch, and touch, allowing us to feel an insect landing on our skin.

What is a difference between tactile (Meissner's) corpuscles and tactile (Merkel) discs? Unlike Merkel discs, Meissner's corpuscles detect light touch. Unlike Merkel discs, Meissner's corpuscles are surrounded (encapsulated) by connective tissue and Schwann cells Meissner's corpuscles are classified as mechanoreceptors, while Merkel discs are classified as proprioceptors. Meissner's corpuscles are found in the skin. Merkel discs are found in muscles, ligaments, tendons, and joints.

Merkel discs are classified as unencapsulated. They lack a connective tissue capsule around the nerve ending.

Three main levels of neural integration operate in the somatosensory system. Which level involves the spinal cord?

Processing at the circuit level includes the transmission of action potentials along ascending spinal pathways. These pathways deliver impulses to the appropriate regions of the cerebral cortex for localization and perception of the stimulus.

How do proprioceptors help maintain body homeostasis?Proprioceptors detect pain so that the body can be alerted to dangerous stimuli, such as extreme temperatures or harmful chemicals. Proprioceptors help prevent prolonged exposure to harmful chemicals. Proprioceptors are able to detect temperature so that the body can sweat or shiver if necessary. Proprioceptors help prevent excessive stretching at the joints.

Proprioceptors are located in the muscles, joints, tendons, and ligaments to detect and monitor body position. They send signals to the brain to warn of extensive stretching or hyperextension of a joint.

Which of the receptor types shown here functions exclusively as a proprioceptor?

Proprioceptors are sensitive to stimuli associated with body movements. The muscle spindle shown in B is responsive to muscle stretch.

Which of the receptor types contributes to the sense of touch by responding to light pressure?

The epithelial tactile complex (Merkel cell and disc) shown in E would be located in the base of the epidermis and would detect light touch.

Which reflex is triggered when a stranger suddenly grasps your arm?

The grasped arm is withdrawn (via the flexor reflex) as the opposite arm pushes you away from the attacker (via crossed-extensor reflex). As in this scenario, the crossed-extensor reflex often accompanies the flexor reflex.

The knee-jerk reflex is an example of a __________.

The most familiar clinical example of a stretch reflex is the knee-jerk reflex. The overall goal of a stretch reflex is to maintain a muscle's length and in turn maintain body position. For example, the knee-jerk reflex, during which the knee extensors contract in response to being stretched, helps keep your knees from buckling when you are standing upright.

The phrenic nerve is a branch from the __________.

The phrenic nerve, which arises from the cervical plexus, supplies both motor and sensory fibers to the diaphragm, the main breathing muscle.

Gluteal muscle innervation comes from which plexus?

The sacral plexus innervates the gluteal muscles.

Which body locations typically lack proprioceptors? connective tissues covering bones and muscles skin surface tendons and ligaments skeletal muscles

The skin surface does not contain proprioceptors. Proprioceptors receive stimuli from deeper within the body than the skin surface.

Which cranial nerve innervates most of the visceral organs?

The vagus nerve has many targets in the thoracic and abdominal cavities and innervates many of the visceral organs.

Which cranial nerve transmits auditory information?

The vestibular branch of the vestibulocochlear nerve transmits afferent impulses for the sense of equilibrium. The cochlear branch transmits auditory information via afferent impulses for the sense of hearing.

Which connective tissue layer directly surrounds individual axons in a nerve?

Within a nerve, each axon is surrounded by endoneurium, a delicate layer of loose connective tissue that also encloses the fiber's associated Schwann cells.

intrafusal fibers

a bundle of modified skeletal muscle fibers in each muscle spindle

sensory receptors

a cell or part of a cell specialized to respond to a stimulus

Label the diagram

a-epithelial tactile complexes, which detect light pressure b-tactile corpuscle, which also detect light pressure c-lamellar corpuscle, detect deep pressure, stretch, and vibration d-bulbous corpuscle, detects deep pressure and stretch e-free nerve endings, detect pain and temp f-hair follicle receptor, detect hair movement

sensory receptors classified by location

according to either their location or location of the activating stimulus: exteroceptors, interoceptors, proprioceptors

sensation

awareness of changes in the internal and external environments

stimuli

change in the environment that evokes a response

perception

conscious interpretation of those stimuli

encapsulated nerve/dendtritic endings

consist of one or more fiber terminals of sensory neurons enclosed in a connective tissue capsule almost all are mechanoreceptors but vary greatly in shape, size, and distribution in the body. includes tactile (meissner's) corpuscles, lamellar (pacinian) corpuscles, bulbous corpuscles (ruffini endings), muscle spindles, tendon organ, and joint kinesthetic receptors

Which type of stimulus would activate nociceptors of the skin? moderate sunlight exposure extreme cold warm bathtub water a vibrating cell phone

extreme cold, Nociceptors respond to stimuli that might damage the body, experienced as pain. These stimuli might include extreme heat or cold, excessive pressure, or inflammatory chemicals.

Your PNS mostly consists of nerves. What else belongs to your PNS?

in addition to nerves, the PNS also consists of sensory receptors, motor endings, and ganglia

lamellar (pacinian) corpuscles

large receptors respond to deep pressure and vibration when first applied (then turn off) located deep in the dermis and in subcutaneous tissue

tactile (merkel) discs

lie at the junction of epidermis and dermis function as light pressure receptors

sensory receptors classified by stimulus type

mechanoreceptors, thermoreceptors, photoreceptors, chemoreceptors, nociceptors

simple receptors of the general senses

modified dendritic endings of sensory neurons, found throughout the body and monitor most types of general sensory info receptors have either nonencapsulated (free) nerve endings or encapsulated nerve endings

superficial dermis

nerve endings that respond to cold are located here

deeper in dermis

nerve endings that respond to heat are located here

You've cut your finger on a broken beaker in your A&P lab. Using stimulus type, location, and receptor structure, classify the sensory receptors that allow you to feel the pain.

nociceptors respond to painful stimulu. They are exteroceptors that are nonencapsulated (free) nerve endings

Nonencapsulated (free) nerve endings

particularly abundant in epithelia and connective tissues most are nonmyelinated, small-diameter group C fibers distal terminals have knoblike endings respond mainly to painful stimuli and changes in temp, but some respond to tissue movements caused by pressure as well consist of thermoreceptors, nociceptors, tactile (merkel) discs, hair follicle

tendon organs

proprioceptors located in tendons, close to the junction between the skeletal muscle and the tendon that detect stretch when muscle contraction stretches the tendon fibers, the resulting compression of the nerve fibers activates these which initiates a reflex that causes the contracting muscle to relax

joint kinesthetic receptors

proprioceptors that monitor joint position and motion monitor stretch in the articular capsules that enclose synovial joints

chemoreceptors

respond to chemicals in solution (molecules smelled or tasted, or changes in blood or interstitial fluid chemistry)

Bulbous corpuscles (Ruffini endings)

respond to deep and continuous pressure located in the dermis, subcutaneous tissue, and joint capsules

photoreceptors

respond to light, such as those of the retina of the eye

mechanoreceptors

respond to mechanical force such as touch, pressure (including blood pressure), vibration, and stretch

nociceptors

respond to potentially damaging stimuli that result in pain example: extreme cold

thermoreceptors

respond to temperature changes

proprioceptors

responds to internal stimuli occur in skeletal muscles, tendons, joints, and ligaments and in connective tissue coverings of bones and muscles constantly advise the brain of our body movements by monitoring how much the organs containing these receptors are stretched

interoceptors(visceroceptors)

responds to stimuli within the body, arising in internal viscera and blood vessels sensitive to chemical changes, tissue stretch, and temp changes sometimes cause discomfort but usually person is unaware of their workings

exteroceptors

sensitive to stimuli arising outside the body most are near or at the body surface include touch, pressure, pain, and temp receptors in skin and more receptors of the special senses (vision, hearing, equilibrium, smell, and taste)

classified by receptor structure

simple receptors of the general senses and receptors for special senses

Tactile (Meissner's) corpuscles

small receptors involved in discriminative touch Found just below skin, mostly in sensitive and hairless areas (fingertips) a few spiraling sensory terminals are surrounded by schwann cells and then by a thin egg-shaped connective tissue capsule

muscle spindles

spindle-shaped proprioceptors that respond to muscle stretch found throughout the perimysium detect muscle stretch and initiatie a reflex that resists the stretch

hair follicle receptors

wrap basket-like around hair follicles light tough receptors that detect bending of hairs