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
Joint Kinesthetic Receptors
Receptors that deal with joint position
Location: lamellated corpuscles, type II cutaneous Mechanoreceptors, tendon organs and free nerve endings.
Sensation: Joint position and movement
Rate: rapid
Found within and around articular capsule of synovial joints.
Intrafusal Fibers
Adapting sensory muscle found in muscle fibers that are nerve endings wrapped around 3-10 specialized muscle fiber.
Gamma Motor Neurons
Contained in muscle spindle. A motor neuron that terminates near both ends of the intrafusal fibers and adjust the muscle spindle to variations in the length of the muscle.
Cell bodies are located in the anterior gray horn of the spinal cord.
Extramural Muscle Fibers
Ordinary skeletal muscle fibers that surrounds muscle spindles.
Alpha Motor Neurons
Large diameter A fibers that supply supply extramural muscle fibers.
Located in the anterior gray horn of the spinal cord.
Tendon Facicles
Bundles of collagen fibers that are enclosed by thin connective tissue in tendon organs.
Somatic Sensory (Somatosensory) Pathway
Pathway that relay information to the post central gurus.
Relay information from somatic sensory receptors to the primary somatosensory area in the parietal lobe of the cerebral cortex and to the cerebellum.
Consists of 3 types of neurons.
3 Neurons of the Somatic Sensory (somatosensory) Pathway
- First Order (primary) Neuron: conduct impulses from somatic sensory receptors into the brain stem or spinal cord.
- Second Order (secondary) Neurons: conduct impulses from the brainstem or spinal cord to the thalamus. These decussate (cross over to other side) as they move.
- Third Order (tertiary) Neurons: conduct impulses from the thalamus to the primary somatosensory area on the same side. When they reach primary area, perception of the sensation occurs.
Relay Station
Regions within the CNS where neurons synapse with other neurons that are a part of a particular sensory or motor pathway. Neural signals are being relayed from one region of the CNS to another.
Posterior Column Medial Lemniscus Pathway
Contains posterior columns that contain tracts cuneate fasciculus and gracile fasciculus.
Where nerve impulses from touch, pressure, vibration, and proprioception from the limbs, trunk, neck and posterior head ascend to the cerebral cortex.
Posterior (Dorsal) Columns
Consists with fine touch sensations, vibrations and conscious proprioception.
Formed by axons of first order neurons in the spinal cord.
Consists of 2 tracts:
1. gracile fasciculus
2. cuneate fasciculus
Medial Lemniscus
A thin ribbon like projections that extends from the medulla to the ventral posterior nucleus of the thalamus.
Axons of the second order neurons cross to the opposite aide of the medulla to enter this structure.
Spinothalamic Pathway
Cell bodies of first order neurons are located in posterior (dorsal) root ganglia connect receptors of the limbs, trunk, neck and posterior head with the spinal cord.
Where nerve impulses for pain, temp, itch, and tickle from the limbs, trunk, neck and poster head ascend to the cerebral cortex.
Spinothalamic Tract
Convey impulses that are consciously perceived.
Upward pathway to the brain. Axon of the second order neurons cross to the opposite side of the cord and pass through this tract.
Trigeminothalamic Pathway
Where nerve impulses for most somatic sensations from the face, nasal cavity, oral cavity and teeth ascend to the cerebral cortex along this path.
Trigeminothalamic Tract
Convey impulses that are consciously perceived.
Tract to the ventral posterior nucleus. Axons of second order neurons cross to the opposite side of the pons and medulla and ascend through this tract.
Mapping of Primary Somatosensory Area
Specific ares of the cerebral cortex receive somatic sensory input from particular parts of the body.
The somatic sensory map and somatic motor map relate body parts to these cortical areas.
Primary Somatosensory Area
Occupies the post central gyri of the parietal lobes of the cerebral cortex.
Precise localization of somatic sensations occurs when nerve impulses arrive at this area.
Each region in this area receives sensory input from a different part of the body.
Sensory Homunculus
The distorted somatic sensory map of the body where there are many sensory receptors in the skin of the lips but few in the skin of the trunk.
2 Tracts of the Spinal Cord
- Anterior Spinocerebellar Tract
- Posterior Spinocerebellar Tract
The two major routes for proprioceptive impulses take to reach the cerebellum.
These pathways are critical for posture, balance and coordination of skilled movements.
Neural Circuits
Circuits in the brain and spinal cord. Orchestrate all voluntary movements.
Lower Motor Neurons
Motor neurons that extend out of the brainstem and spinal cord to innervate skeletal muscles.
There cell bodies are in the lower parts of the CNS (brainstem and spinal cord).
Premotor Area
Pathway that begin in motor area of cerebral cortex (frontal lobe). Stores procedural memory.
Where motor plan is developed when the idea or desire to move a body part is generated.
The info is sent to basal nuclei, it processes the info, sends to thalamus then to promoter area. From the promoter area, the plan is transmitted to the primary motor area for execution.
Primary Motor Area
Is the major control region for the execution of voluntary movements.
Electrical stimulation in this area causes contraction of specific muscles on the opposite side of the body.
Controls muscles by forming descending pathways that extend to the spinal cord and brainstem.
Motor Homunculus
Distorted muscle map of the body where muscles in the thumb, fingers, lips, tongue and vocal cords have large representations whereas the trunk has a much smaller representation.
Direct Motor Pathways
(Pyramidal Pathways)
Provide input to lower motor neurons via axons that extend directly from the cerebral cortex. The axons descend from the pyramidal cells of the primary motor area/premotor area.
Also, action potentials for voluntary movements prograde from the cerebral cortex to lower motor neurons via this path.
Pyramidal Cells
Are upper motor neurons that have pyramid shaped bodies.
The main output cells of cerebral cortex.
Corticospinal Pathway
A direct motor pathway.
Conduct impulses for the control of muscles of the limbs and trunk.
Corticospinal Tract
Formed by axons of the upper motor neurons in the cerebral cortex. These tracts descend through the internal capsule of the cerebrum and the cerebral peduncle of the midbrain.
Lateral Corticospinal Tracts
Formed by axons that decussate in the medulla in the lateral white column of the spinal cord.
Axons synapse with local circuit neurons/lower motor neurons in anterior gray horn of spinal cord. Axon terminate in muscles that control distal muscles of limbs. These muscle are responsible for: precise, agile and highly skilled movements of the hands and feet.
Anterior Corticospinal Tract
Formed by axons that do not decussate in the medulla in the anterior white column of the spinal cord.
Axons decussate via the anterior shite commissure then synapse with local circuit neurons/lower motor neurons of anterior gray horn.
Axons exit spinal cord and terminate in skeletal muscles that control trunk and proximal parts of the limbs.
Corticobulbar Pathway
Conducts impulses for the control of skeletal muscles in the head.
Corticobulbar Tract
Descends along with the corticospinal tracts through the internal capsule of the cerebrum and cerebral peduncle of the midbrain.
Control of Movement by the Brain
4 Major Motor Centers
- Vestibular nuclei in medulla and pons
- Reticular formation located throughout the brainstem
- Superior colliculi in the midbrain
- Red nucleus in the midbrain
Indirect Motor Pathway
(Or extrapyramidal pathway)
Brainstem motor centers give rise to this pathway. Include all somatic motor tracts other than the corticospinal and Corticobulbar tracts.
Axons descend from the brainstem motor centers into 5 major tracts of the spinal cord:
1. rubrospinal
2. Tectospinal
3. vestibulospinal
4. Lateral reticule spinal
5. Medical reticulospinal tracts
Convey AP that regulate posture, balance, muscle tone, reflexive movements of head and trunk.
Postural Reflexes
Keep the body in an upright and balanced position.
Input comes from 3 sources:
1. Eyes, provide visual information about the position of the body in space
2. Vestibular apparatus of inner ear, provides info about position of the head.
3. Proprioceptors in muscles and joints, which provide info about position of the limbs.
Vestibulospinal Tract
Vestibular nuclei generate action potentials along the axons of this tract. Conveys signals to skeletal muscles of the trunk and proximal part of the limbs causes contractions in order to maintain posture in response to changing equilibrium.
Reticular Formation
Helps control posture and alter muscle tone.
Receives input from several sources, eyes, ear, cerebellum, and basal nuclei.
Medical Reticulospinal Tract
Convey signals to skeletal muscles of the trunk and proximal limbs to help control posture and maintain muscle tone.
This tract excites the skeletal muscles of the trunk and extensor muscles of the proximal limbs.
Lateral Reticulospinal Tract
Convey signals to skeletal muscles of the trunk and proximal limbs. Inhibits the skeletal muscles of the trunk and extensor muscles of the proximal limbs.
Superior Colliculus
Receives visual input from the eyes and auditory input from the ears via connections with the inferior colliculus.
Tectospinal Tract
When input occurs in a sudden, unexpected manner, the superior colliculus produces an action potential along this tract.
Conveys neural signals that activate skeletal muscles in the head and trunk.
Saccades
Small rapid jerking movements of the eyes that occurs as a person looks at different points in the visual field.
Superior colliculus is the integrating center for the saccades.
Red Nucleus
Receives input from the cerebral cortex and the cerebellum.
Rubrospinal Tracts
In response to input recieved from the red nucleus, the nucleus generates action potential along the axons of this tract.
Conveys neural signals that activate skeletal muscles that cause fine, precise, voluntary movements of the distal parts of the upper limbs.
Integration
Function of cerebrum.
The processing of sensory information by analyzing and storing it and making decisions for various responses.
Integrative Functions
Include activities such as sleep and wakefulness, learning, memory and language.
Circadian Rhythm
Where human sleep and awaken in a 24 hour cycle. This is established by the suprachiasmatic nucleus of the hypothalamus.
Reticular Activating System
Where the nervous system makes the transition between sleep and awake. Stimulation of some parts of nervous system increase activity of the cerebral cortex. When this area is active the effector is generalized increase in cortical activity.
Arousal
Awakening from sleep. RAS must be stimulated, by pain, touch, pressure, movement etc, once activated cerebral cortex is also activated, arousal occurs.
Consciousness
A state of wakefulness.
REM Sleep Centers
Promoted by centers in pons and midbrain
NREM Sleep Centers
Non Rapid Eye Movement
NREM sleep is inducted in the hypothalamus and basal forebrain.
Associative Learning
Occurs when a connection is made between two stimuli.
Nonassociative Learning
Occurs when repeated exposure to a single stimulus causes a change in behavior.
2 types
1. Habituation: repeated exposure causes a decreased behavior response
2. Sensitization: repeated exposure to a noxious stimulus causes increase behavioral response.
Declarative (Explicit) Memory
Memory of experiences that can be verbalized such as facts, events, objects, names and places.
Requires recall and is stored association of the cerebral cortex.
Procedural (Implicit) Memory
Is the memory of motor skills, procedures, and rules.
Stored in: cerebellum, promotor area and basal nuclei
Does not require conscious recall.
Memory Consolidation
The process by which a short term memory is transformed into a long term memory.
Hippocampus plays a major role in this consolidation.
Plasticity
The capability for change associated with learning. THe capability of the brain to structurally and functionally change in order to create long term memories.
With increased use the neurons grow new synapse end bulbs and synaptic connections strengthen.
Language Areas of Cerebral Cortex
Only present in the left cerebral hemisphere
1. Wernicke’s Area: an association areas in temporal lobe. Interprets the meaning of written or spoken words.
2. Brocs’a Area: a motor area located in frontal lobe. Is active as you translate thoughts into speech.
Conscious Awareness
Sensation occurs when sensory receptors reach the cerebral cortex.
The cerebral cortex is most active when the person is awake.
Free Nerve Endings
Type of Joint kinesthetic
Belong to first order neurons with no apparent structural specialization.
Gracile Fasciculus
Nerve impulses for touch, pressure, vibration and conscious proprioception for the lower limbs and lower trunk propagate along this tract to the gracile nucleus of the medulla where fist order neurons synapse with second order neurons.
Spinocerebellar Tract
Posterior and anterior tract utilized by propioceptor impulses travel from the trunk to the lower limbs on one side of the body.
The sensory impulses are not consciously perceived.
Vital for coordination of skilled movements, maintaining posterior and balance.
Basal Nuclei
Stores: procedural memory
Components:
globes pallidus, caudate nucleus and put amen
Function:
Suppressing unwanted movements
Initiating and terminating movements
Reducing muscle tone
Short Term Memory
The ability to remember a few pieces of information for seconds to minutes. Relies more one electrical and chemical changes int he body.
Long Term Memory
Relies on synaptic structural changes
REM Sleep
Approximately 25% of sleep in adults is REM sleep.
50% of sleep in infants
35% in 2 year olds.
