Unit 4: Sensory, motor, and integrative system Flashcards
Define sensation.
The conscious or subconscious awareness of changes in the external or internal environment.
Define perception.
The conscious interpretation of sensations and is primarily a function of the cerebral cortex.
Explain what sensory modality is.
Each unique type of sensation (touch, pain, vision, or hearing) is called a sensory modality.
A given sensory neuron carries information for only ONE sensory modality.
What are the two different sensory modality classes?
- General senses
- Special senses
Explain what general senses are.
Refers to both somatic senses and visceral senses. Somatic senses are muscular and the external environment, it includes tactile sensations, thermal sensations, pain sensations, and proprioceptors.
Visceral senses are felt internally an in the organs, provides information about conditions within internal organs.
Explain what special senses are.
Includes the modalities of smell, taste, vision, hearing, equilibrium and balance.
Where does the process of sensation begin?
The process of sensations begins in a sensory receptors, which can either be a specialized cell or its dendrites of a sensory neuron.
Explain what stimulus is.
A change in the environment that can activate certain sensory receptors.
Explain what selectivity is for sensory receptors.
A sensory receptor responds only weakly or not at all to other stimuli. This characteristic of sensory receptors is known as selectivity.
What are the four events that typically occur for a sensation to arise?
- Stimulation of the sensory receptor
- Transduction of the stimulus
- Generation of nerve impulses
- Integration of sensory input
Explain what transduction is. What do they mean by transduce?
A sensory receptor converts the energy in the stimulus into a graded potential, a process known as transduction. It can transduce (convert) only one kind of stimulus.
Explain what a receptor potential is.
A sensory receptor responds to a stimulus by generating a graded potential known as a receptor potential.
What are the three sensory receptors based on the location of the receptors and the origin of the stimuli that activate them?
- Exteroceptors: Located at or near the external surface of the body; they are sensitive to stimuli originating outside the body and provide information about the external environment. The sensations of hearing, vision, smell, taste, touch, pressure, vibration, temperature, and pain are conveyed by exteroceptors.
- Interoceptors: Or visceroceptors, are located in blood vessels, visceral organs, muscles, and the nervous system and monitor conditions in the internal environment. The nerve impulses produced by interoceptors usually are not consciously perceived.
- Proprioceptors: Located in muscle, tendons, joints, and the inner ear. They provide information about body positions, muscle length and tension, and the position and movements of your joints.
What are the six types of stimulus detected?
- Mechanoreceptors: Sensitive to mechanical stimuli such as the deformation, stretching, or bending of cells. Mechanoreceptors provide sensations of touch, pressure, vibration, proprioception, hearing and equilibrium. They also monitor the stretching of blood vessels and internal organs.
- Thermoreceptors: Detect changes in temperature.
- Nociceptors: Responds to painful stimuli resulting from physical or chemical damage to tissue.
- Photoreceptors: Detect light that strikes the retina of the eye.
- Chemoreceptors: Detects chemicals in the mouth, nose, and body fluids.
- Osmoreceptors: Detects the osmotic pressure of body fluids.
Explain what adaptation is in sensory receptors.
A characteristics of muscle sensory receptors is adaptation, in which the receptor potential decreases in amplitude during a maintained, constant stimulus. Because of adaptation, the perception of a sensation may fade or disappear even though the stimulus persists.
Differentiate between rapidly adapting receptors and slowly adapting receptors.
Rapidly adapting receptors adapt really quickly. They are specialized for signalling changes in a stimulus.
Slowly adapting receptors adapt slowly and continue to trigger nerve impulses as long as the stimulus persists. Slowly adapting receptors maintain stimuli associated with pain, body position, and chemical composition of the blood.
Explain what somatic sensations are.
They 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 areas with the highest density of somatic sensory receptors are the tip of the tongue, the lips, and the fingertips.
Explain what cutaneous sensations are.
Somatic sensations that from from simulating the skin surface are cutaneous sensations. There are four modalities of somatic sensations: tactile, thermal, pain, and proprioceptive.
Explain what tactile sensations are.
They include touch, pressure, vibration, itch, and tickle. Several types of encapsulated mechanoreceptors attached to large diameter myelinated A fibers mediate sensations of touch, pressure, and vibration. Other tactile sensations, such as itch and tickle sensations, are detected by free endings attached to small diameter, unmyelinated C fibers.
Explain the touch sensations.
Sensations of touch generally results from stimulation of tactile receptors in the skin or subcutaneous layer.
What are the two types of rapidly adapting touch receptors?
- Corpuscles of touch: or Meissner corpuscles, are touch receptors that are located in the dermal papillae of hairless skin. Because corpuscles of touch are rapidly adapting receptors, they generate nerve impulse mainly at the onset of touch.
- Hair root plexus: are rapidly adapting touch receptors found in hairy skin, they consists of free nerve endings wrapped around hair follicles.
What are the slowly rapidly adapting touch?
- Type 1 cutaneous mechanoreceptors: or tactile (merkel) discs, are saucer shaped, flattened nerve endings that make contact with tactile epithelial cells of the stratum basale. These receptors responds to continues touch, such as holding an object in your hand for an extended period of time.
- Type 2 cutaneous mechanoreceptors: or ruffini corpuscles, are elongated, encapsulated receptors located in the dermis, subcutaneous layer, and other tissues of the body. They are highly sensitive to skin stretching.
Explain the sensation of pressure. What receptors are involved?
A sustained sensation that is felt over a larger area than touch, occurs with deeper deformation of the skin and subcutaneous layer.
The receptors that contribute to sensations of pressure are type 1 and type 2 mechanoreceptors. These receptors are able to responds to a steady pressure stimulus because they are slowly adapting.
Explain what the sensation of vibration is.
Sensations of vibration result from rapidly repetative sensory signals form tactile receptors. The receptors for vibration sensations are lamellated corpuscles and corpuscles of touch.
Explain what a lamellated corpuscles are.
Also called pacinian corpuscle, consists of nerve ending surrounded by a multilayered connective tissue capsule. Lamellated corpuscle adapt rapidly. They are found in the dermis, subcutaneous layer, and other body tissues.
They respond to high frequency vibrations.
Explain what the sensation of itch is.
The itch sensations result from stimulation of free nerve endings by certain chemicals, often because of a local inflammatory response.
Stretching usually alleviates itching by activating a pathway that blocks transmission of the itch signals though the spinal cord.
Explain what the tickle sensation is.
Free nerve endings are though to mediate the tickle sensation. This intriguing sensations typically arises only when someone else touches you, not when you touch yourself.
Explain what thermoreceptors are.
They are free nerve endings that have receptive fields about 1mm in diameter on the skins surface.
Explain what the cold receptors are in the thermal sensation.
Two distinct thermal sensations are detected by different receptors. Cold receptors are located in the stratum basale of the epidermis and are attached to medium – diameter, myelinated A fibers, although a few connection to small diameter, unmyelinated C fibers.
Explain what the warm receptors are in the thermal sensation.
They are located in the dermis and are attached to small receptors, unmyelinated C fibers. Cold and warm receptors both adapt rapidly at the onset of a stimulus, but they continue to generate impulses at a lower frequency throughout a prolonged stimulus.
Explain what the pain sensation is. What are nociceptors?
Pain is indispensable for survival. It serves a protective function by signalling the presence of noxious, tissue damaging conditions.
Nociceptors are free nerve endings found in every tissue of the body except the brain. Intense thermal, mechanical, or chemical stimuli can activate nociceptors. Tissue irritation or injury releases chemicals such as prostaglandins, kinins, and potassium ion that stimulate nociceptors.
Differentiate between fast pain and slow pain.
The perception of fast pain occurs very rapidly, because the nerve impulses propagate along medium diameter, myelinated A fibers. Fast pain is not felt in deeper tissues of the body.
The perception of 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.
Differentiate between superficial somatic pain and deep somatic pain.
Pain that arises from stimulation of receptors in the skin is called superficial somatic pain.
Stimulation of receptors in skeletal muscles, joints, tendons, and fascia causes deep somatic pain.
Explain what the visceral pain is.
Visceral pain results from stimulation of nociceptors in visceral organs. If stimulation is diffuse, visceral pain can be severe.
Explain what localization of pain is.
Fast pain is very precisely localized to the stimulated area. Somatic slow pain also is well localized but more diffuse. In some instances of visceral slow pain, the affected area is where the pain is felt.
Explain what referred pain is.
In some instances of visceral pain, the pain is felt in or just deep to the skin that overlies the stimulated organs, or in a surface area far from the stimulated organs. This phenomenon is called referred pain.
The visceral organ involved and the area to which the pain is referred are served by the same segment of the spinal cord.
Explain what proprioceptive sensations are.
Also called proprioception. Proprioceptive sensations allow us to recognize that part of our body belongs to us.
Explain what kinaesthesia is.
It is the perception of body movements.
How does proprioceptors work?
Proprioceptive sensations arise in the receptors termed proprioceptors. Because most proprioceptors adapt slowly and only slightly, the brain continually receives nerve impulses related to the position of different body parts and making adjustments to ensure coordination.
Explain what weight distribution is.
Proprioceptors also allow weight discrimination, the ability to asses the weight of an object. This type of information helps you to determine the muscular effort necessary to perform a task.
Explain what muscle spindles are.
They are the proprioceptors that monitor changes in the length of skeletal muscles and participate in stretch reflex.
Explain what muscle tone is.
By adjusting how vigorously a muscle spindle responds to stretching of a skeletal muscle, the brain sets an overall level of muscle tone, the small degree of contraction that is present while the muscle is at risk.
Explain what intrafusal fibers are.
Each muscle spindles consists of several slowly adapting sensory nerve endings that wrap around 3 to 10 specialized muscle fibers, called intrafusal fibers.
What is the main function of muscle spindles?
The main function of muscle spindles is to measure muscle length. Either sudden or prolonged stretching of the central area of the intrafusal muscles.
Explain what gamma motor neurons are.
Muscle spindles contain motor neurons called gamma motor neurons. These motor neurons terminate near both ends of the intrafusal fibers and adjust the tension in a muscle spindle to variations in the length of the muscle.
Explain what extrafusal muscle fibers and alpha motor neurons are.
Surrounding muscle spindles are ordinary skeletal muscle fibers, called extrafusal muscle fibers, which are supplied by large diameter A fibers called alpha motor neurons.
Explain what tendon organs are.
Tendon organs are slowly adapting receptors located at the junctions of a tendon and a muscle. By initiating tendon reflexes, tendon organs protect tendons and their associated muscles from damage due to excessive tension.
When tension is applied to a muscle, the tendon organs generate nerve impulses that propagate into the CNS, providing information about changes in muscle tension.
The resulting tendon reflexes decrease muscle tension by causing muscle relaxation.
Explain what joint kinesthetics receptors are.
Several types of joint kinesthetics receptors are present within and around the articular capsules of synovial joints. Free nerve endings and type 2 cutaneous mechanoreceptors in the capsule of joints responds to pressure.
Explain what somatic sensory (somatosensory) pathways are.
They relay information form somatic sensory receptors to the primary somatosensory area in the parietal lobe of the cerebral cortex and to the cerebellum.
A somatic sensory pathway to the cerebral cortex consists of thousands of sets of three neurons
- First order neuron
- Second order neuron
- Third order neuron
Explain what first order (primary) neurons are.
They are sensory neurons that conduct impulses from somatic sensory receptors into the brainstem or spinal cords. From the face, nasal cavity, oral cavity, teeth, and eyes, somatic sensory impulses propagate along the cranial nerves into the brainstem.
From the neck, trunk, limbs, and posterior aspect of the head somatic sensory impulses propagates along spinal nerves into the spinal cords.
Explain what second order (secondary) neurons are.
They conduct impulses from the brainstem or spinal cord to the thalamus. Axons of the second - order neurons decussate as they course through the brainstem or spinal cord before ascending to the thalamus.
Explain what decussate mean.
To cross over to the opposite sides.
Explain what third order (tertiary) neurons are.
They conduct impulses from the thalamus to the primary somatosensory area on the same side. As the impulses reach the primarily somatosensory area, perception of the sensation occurs. Because the axons of second order neurons decussate as they pass through the brainstem or spinal cord, somatic sensory information on one side of the body is perceived by the primary somatosensory area on the opposite side of the brain.
Explain what relay stations are in the CNS.
Regions within the CNS where neurons synapse with other neurons that are a part of a particular sensory or motor pathway are known as relay stations because neural signals are being relayed from one region of the CNS to another.
What are the three general pathways of the somatic sensory impulses?
- The posterior column - medial leminiscuss pathway
- The anterolateral (spinothalamic) pathway
- The trigeminothalamic pathway
