Chapter 16: Sensory, Motor And Integrative Systems Flashcards
Sensation
Is the conscious or subconscious awareness of changes in external or internal environment.
Perception
Is the conscious interpretation of sensations and is primary a function of the cerebral cortex.
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.
Sensory Modalities Classes
- General Senses: refer to both somatic and visceral senses.
Somatic: tactile, thermal, pain and proprioceptive sensations.
Visceral: Provide info about conditions within internal organs like pressure, stretch, nausea - Special Senses: include the sensory modalities of smell, taste, vision, hearing, and equilibrium or balance.
Sensory Receptor
Can be either a specialized cell or the dendrites of a sensory neuron.
The process of sensation begins with a sensory neuron.
Stimulus
A change in environment that can activate certain sensory receptors.
Selectivity
Characteristic of sensory receptors. A sensory receptor responds only weakly or not at all to other stimuli.
4 Events that Occur for a Sensation to Arise
- Stimulation of the sensory receptor; an appropriate stimulus must occurs within the sensory receptors receptive filed.
- Transduction of the stimulus: a sensory receptor converts the energy ions stimulus into a graded potential, process known as transduction. It can transducer (convert) only one kind of stimulus.
- Generation of Nerve impulses: when a graded potential in sensory receptor reaches threshold, it triggers one or more nerve impulses, which then propagate toward the CNS.
- Integration of sensory input: a particular region of the CNS receives and integrates (processes) the sensory nerve impulses.
Types of Sensory Receptors
- Microscopic structure
- Location of the receptor and the origin of stimuli that activate them.
- Type of stimulus detected.
Microscopic Structure
- Free nerve endings: bare dendrites associated with pain, thermal, tickle, itch and some touch
- Encapsulated nerve endings: dendrites enclosed in connective tissue capsule for pressure, vibration and touch.
- Separate cells that synapse with first order sensory neurons: receptors cells synapse with first order sensory neurons, located in retina eyes.
Receptor Location and Activating Stimuli
- Exteroceptors: Located at or near body surfaces, sensitive to stimuli originating outside the body.
- Interoceptor: located in blood vessels, visceral organs, and nervous system
- Proprioceptors: located in the muscles, tendons and inner ear
Type Of Stimulus Detected
- Mechanoreceptors: detect mechanical stimuli, provide sensation of touch, pressure, vibration, proprioception and hearing.
- 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 chemical in mouth, nose and body fluids.
- Osmoreceptors: Sense osmotic pressure of body fluids.
Separate Cells
Sensory receptors for some special senses that are specialized. They synapses with sensory neurons.
Include: hair cells for hearing and equilibrium in the inner ear, gustatory receptors in taste buds, and photoreceptors in the retina of the eye for vision.
Receptor Potential
A graded potential generated by a sensory neuron when responding to a stimulus.
Adaptation
A characteristic of most sensory receptors in which receptors potential decreases in amplitude during a maintained, constant stimulus.
Rapidly Adapting Receptors
Adapt very quickly. They rate specialized for changes in a stimulus.
Rapidly adapting receptors: are associated with vibration, touch, and smell.
Somatic Sensation
Arise from stimulation of sensory receptors embedded in the skin or SC layer, mucous membranes of the mouth, vagina, anus, skeletal muscle, tendons and joints.
Highest density: tip of tongue, the lips, and finger tips
4 modalities: tactile, thermal, pain, proprioceptive.
Cutaneous Sensations
Somatic sensations that arise from stimulating the skin surface.
Tactile Sensation
Include touch, pressure, vibration, itch and tickle.
Touch Sensations
Generally result from stimulation of tactile receptors in the skin or SC layer.
Corpuscles Of Touch
Location: capsule surrounds mass of dendrites in dermal papilla of hairless skin.
Sensations: onset of touch and low frequency vibrations.
Rate: Rapid
Hair Root Plexuses
Location: free nerve endings wrapped around hair follicles in skin
Sensations: movement on skin surface that disturbs hairs
Rate: Rapid
Type I Cutaneous Mechanoreceptors
Location: saucer shaped free nerve endings make contact with tactile epithelial cells in epidermis
Sensations: continuous touch and pressure
Rate: slow
Type II Cutaneous Mechanoreceptors
Type of joint kinesthetic receptors
Location: Elongated capsule surrounds dendrites deep in dermis and in ligaments and tendons.
Sensations: skin stretching and pressure.
Rate: Slow
Lamellated (pacinian) Corpuscles
Type of Joint kinesthetic that responds to acceleration and deceleration of joints during movements.
Location: oval, layers capsule surround dendrites, present in dermis and SC layer, submucosal tissue, joints, periosteum and viscera.
Sensations: high frequency vibrations
Rate: Rapid
Pressure Sensation
A sustained sensation that is over a larger area than touch. Occurs with deeper deformation of the skin and SC layer.
Vibration Sensation
Result from rapidly repetitive sensory signal from tactile receptors.
Itch Sensation
Results from stimulation of free nerve endings by certain chemical, such as bradykinn, histamine or antigens. Often because of a local inflammatory response.
Tickle Sensation
Free nerve ending mediate the tickle sensation. This sensation arises only when someone else’s touches you, not when you touch yourself.
Thermoreceptors
Free nerve ending that have receptive fields about 1 mm in diameter on the skins surface.
Thermal Sensations
Two distinct sensations:
1. Cold Receptors: found in stratum basale, attached to medium diameter, myelinated A fibers. Activated temp 10-35 C.
2. Warm Recptors: found in dermis, attached to small diameter, unmyelinated C fibers. Activated temp 30-45 C
Location: Free nerve endings are found in skin,mucous membranes of mouth,m vagina and anus.
Sensation: cold and warm
Rate: initially rapid then slow.
Pain Sensation
Serves as a protection function by signaling the presence of noxious, tissue damaging conditions.
Nociceptors
Location: free nerve endings in every body tissue except the brain.
Sensations: pain
Rate: slow
Activation: intense thermal, mechanical or chemical stimuli
Types of Pain
- Fast Pain: (acute) occurs rapidly, 0.1 seconds after stimulus applied due to nerve impulses that propagate alone medium diameter, myelinated A fibers.
This type of pain is like a prick and is not felt deep in the tissue. - Slow Pain: (chronic) occurs in 1 sec - up to 1 min. Impulses conduct along a small diameter, unmylinated C fibers. This type of pain is itching, burning or throbbing and is felt in both skin and deep tissue.
Superficial Somatic Pain
Pain that arises from stimulation of receptors in the skin.
Deep Somatic Pain
Stimulation of receptors in skeletal muslce, joints, tendons and fascia muslces.
Visceral Pain
Results from stimulation of Nociceptors in visceral organs. If stimulation is diffuse (large area) this type of pain can be severe.
Referred Pain
Pain that is felt in or just deep to the skin that overlies the stimulated organ or in a surface areas far from the stimulated organ.
Proprioceptive Sensations
Allow us to recognize that parts of our body belongs to self. Also allows us to know where our head and limbs are located and they are moving even if we are not looking at them.
Kinesthesia
Is the perception of body movements.
proprioceptors
Where Proprioceptors sensation arise. They are embedded in muscles (esp in postural muscles) and tendons inform up of the degree to which muscle contract.
Also allow for weight discrimination: ability to assess the wight of an object.
Muscle Spindle
Found in varies amounts throughout the body
Most abundant in fingers muscles as they produce coarser movements.
Proprioceptors that monitor changes in length of skeletal muscles and participate in stretch reflexes.
Location: sensory nerve ending wrap around central area of encapsulated intramural muscle with most skelteal muscles.
Sensation: muslce length
Rate: slow
Muscle Tone
Small degree of contraction that is present while the muscle is at rest. The brain will set the tone bases on the muscle spindle response to stretching of a skeletal muscle.
Tendon Organs
Proprioceptors
Receptor that controls the force of muscle contraction.
Location: capsule enclosed collagen fibers and sensory nerve endings at junction of tendon and muscle.
Sensation: Muscle tension
Rate: slow
Contains: Tendon fascicles