Chapter 16 Flashcards
Sensation
Is the conscious or subconscious awareness of changes in the external or internal environment.
Perception
Is the conscious interpretation of sensations and is primarily a function of the cerebral cortex. If sensory information doesn’t reach the cerebral cortex, we have no perception of it.
Sensory modality
Each unique type of sensation – such as touch, pain, vision, or hearing. A given sensory neuron carries information for only one sensory modality.
What two classes can sensory modality be grouped into?
- General senses
- Special senses
General senses
Refer to both somatic senses and visceral senses.
Somatic senses
Include tactile sensations (touch, pressure, vibration, itch, and tickle), thermal sensations (warm and cold), pain sensations, and proprioceptive sensations. Proprioceptive sensations allow perception of both the static (nonmoving) positions of limbs and body parts (joint and muscle position sense) and movements of the limbs and head.
Visceral senses
Provide information about conditions within internal organs (Eg. Pressure, stretch, chemicals, nausea, hunger, and temperature).
Special senses
Include the sensory modalities of smell, taste, vision, hearing, and equilibrium or balance.
Sensory receptor
What the process of sensation begins at. Can either be a specialized cell or the dendrites of a sensory neuron. Responds to a particular kind of stimulus.
Stimulus
A change in the environment that can activate certain sensory receptors.
What four events take place for a sensation to arise?
- Stimulation of the sensory receptor
- Transduction of the stimulus (sensory receptor converting the energy in the stimulus into a graded potential)
- Generation of nerve impulses
- Integration of sensory input
What are the three classifications for a sensory receptors microscopic structure?
- Free nerve endings (nonencapsulated)
- Encapsulated nerve endings
- Seperate cells
Free nerve endings (nonencapsulated)
Bare dendrites associated with pain, thermal, tickle, itch, and some touch sensations.
Encapsulated nerve endings
Dendrites enclosed in connective tissue capsule for pressure, vibration, and some touch sensations.
Separate cells
Receptor cells that synapse with first-order sensory neurons; located in retina of eye (photoreceptors), inner ear (hair cells), and taste buds of tongue (gustatory receptor cells).
Receptor potential
A graded potential generated by a sensory receptor.
What are the three classifications for a sensory receptors location and activating stimuli?
- Exteroceptors
- Interoceptors
- Proprioceptors
Exteroceptors
Located at or near body surface; sensitive to stimuli originating outside body; provide information about external environment; convey visual, smell, taste, touch, pressure, vibration, thermal, and pain sensations.
Interoceptors
Located in blood vessels, visceral organs, and nervous system; provide information about internal environment; impulses usually are not consciously perceived but occasionally may be felt as pain or pressure.
Proprioceptors
Located in muscles, tendons, joints, and inner ear; provide information about body position, muscle length and tension, position and motion of joints, and equilibrium (balance).
What are the six classifications for a sensory receptors type of stimulus detected?
- Mechanoreceptors
- Thermoreceptors
- Nociceptors
- Photoreceptors
- Chemoreceptors
- Osmoreceptors
Mechanoreceptors
Detect mechanical stimuli; provide sensations of touch, pressure, vibration, proprioception, and hearing and equilibrium; also monitor stretching of blood vessels and internal organs.
Thermoreceptors
Detect changes in temperature.
Nociceptors
Respond to painful stimuli resulting from physical or chemical damage to tissue.
Photoreceptors
Detect light that strikes the retina of the eye.
Chemoreceptors
Detect chemicals in mouth (taste), nose (smell), and body fluids.
Osmoreceptors
Sense osmotic pressure of body fluids.
Adaptation
A characteristic of most sensory receptors in which the receptor potential decreases in amplitude during a maintained, constant stimulus. This causes the frequency of nerve impulses in the sensory neuron to decrease. Because of adaptation, the perception of a sensation may fade or disappear even though the stimulus persists.
Rapidly adapting receptors
Adapt very quickly. They are specialized for signaling changes in a stimulus. Receptors associated with vibration, touch, and smell are rapidly adapting.
Slowly adapting receptors
Adapt slowly and continue to trigger nerve impulses as long as the stimulus persists. Slowly adapting receptors monitor stimuli associated with pain, body position, and chemical composition of the blood.
Somatic sensations
Arise from stimulation of sensory receptors embedded in the skin or subcutaneous layer; in mucous membranes of the mouth, vagina, and anus; and in skeletal muscles, tendons, and joints. The sensory receptors for somatic sensations are distributed unevenly – the areas with the highest density of somatic sensory receptors are the tip of the tongue, the lips, and the fingertips.
Cutaneous sensations
Somatic sensations that arise from stimulating the skin surface.
What are the four modalities of somatic sensation?
- Tactile sensations
- Thermal sensations
- Pain sensations
- Proprioceptive sensations
Tactile sensations
Include touch, pressure, vibration, itch, and tickle. Although we perceive differences among these sensations, they arise by activation of some of the same types of receptors.
Touch
A sensation that results from stimulation of tactile receptors in the skin or subcutaneous layer. The receptors that contribute to sensations of touch are corpuscles of touch, hair root plexuses, type I cutaneous mechanoreceptors, and type II cutaneous mechanoreceptors.
What are the two rapidly adapting touch receptors?
- Corpuscles of touch
- Hair root plexus
Corpuscles of touch (Meissner corpuscle)
Composed of a capsule that surrounds a mass of dendrites in dermal papillae of hairless skin. Senses onset of touch and low-frequency vibrations. Adapts rapidly.
Hair root plexus
Composed of free nerve endings that wrap around hair follicles in skin. Senses movements on skin surface that disturb hairs. Adapts rapidly.
What are the two slowly adapting touch receptors?
- Type I cutaneous mechanoreceptors (tactile discs)
- Type II cutaneous mechanoreceptors (Ruffini corpuscles)
Type I cutaneous mechanoreceptors (tactile discs)
Composed of saucer-shaped free nerve endings that make contact with tactile epithelial cells in the epidermis. Senses continuous touch and pressure. Adapts slowly.
Type II cutaneous mechanoreceptors (Ruffini corpuscles)
Composed of an elongated capsule that surrounds dendrites deep in the dermis and in ligaments and tendons. Senses skin stretching and pressure. Adapts slowly.
Pressure
A sustained sensation that is felt over a larger area than touch and occurs with deeper deformation of the skin and subcutaneous layer. The receptors that contribute to sensations of pressure are type I and type II cutaneous mechanoreceptors.
Vibration
A sensation that results from rapidly repetitive sensory signals from tactile receptors. The receptors that contribute to sensations of vibration are lamellated corpuscles and corpuscles of touch.
Lamellated corpuscles
Composed of an oval, layered capsule that surrounds dendrites; present in dermis and subcutaneous layer, submucosal tissues, joints, periosteum, and some viscera. Senses high frequency vibrations. Adapts rapidly.
Itch and tickle receptors
Composed of free nerve endings in skin and mucous membranes. Senses itching and tickling. Adapts slowly and rapidly.
Thermoreceptors
Free nerve endings that have receptive fields about 1mm in diameter on the skin surface.
Warm and cold receptors
Composed of free nerve endings in skin and mucous membranes of mouth, vagina, and anus. Senses warmth and cold. Initially adapts rapidly then slowly.
Nociceptors
Composed of free nerve endings in every body tissue except brain. Senses pain. Adapts slowly.
Fast pain
Occurs very rapidly, usually within 0.1 second after a stimulus is applied, because the nerve impulses propagate along medium-diameter, myelinated A fibers. This type of pain is also known as acute, sharp, or pricking pain. Fast pain is not felt in deeper tissues of the body (Eg. The pain felt from a needle puncture or knife cut).
Slow pain
Begins a second or more after a stimulus is applied. It then gradually increases in intensity over a period of several seconds or minutes. Impulses for slow pain conduct along small-diameter, unmyelinated C fibers. This type of pain, which may be excruciating, is also referred to as chronic, burning, aching, or throbbing pain. Slow pain can occur both in the skin and in deeper tissues or internal organs (Eg. The pain associated with a toothache).
Superficial somatic pain
Pain that arises from stimulation of receptors in the skin.
Deep somatic pain
Pain that arises from stimulation of receptors in skeletal muscles, joints, tendons, and fascia.
Visceral pain
Pain that arises from stimulation of nociceptors in visceral organs.
Referred pain
When pain is felt in or just deep to the skin the overlies the stimulated organ, or in a surface area far from the stimulated organ. In general, the visceral organ involved and the area to which the pain is referred are served by the same segment of the spinal cord.
Analgesia
Pain relief.
Proprioceptive sensations
AKA proprioception; allow us to recognize that parts of our body belong to us (self). They also allow us to know where our head and limbs are located and how they are moving even if we are not looking at them.
Kinesthesia
The perception of body movements.
Proprioceptors
The receptors that proprioceptive sensations arise from. Are found embedded in muscles (especially postural muscles) and tendons. Inform us of the degree to which muscles are contracted, the amount of tension on tendons, and the positions of joints.
Weight discrimination
The ability to assess the weight of an object.