Chapter 16 Flashcards
Sensation definition
Conscious or subconscious awareness of changes in the internal or external environment
Perception definition
Conscious interpretation of sensations and primarily functions from the cerebral cortex
Sensory modality definition
The unique type of sensation examples: touch, pain, vision, or hearing
What are the two classes of sensory modalities?
- General senses
- Special senses
What are the two general senses and what they do?
- Somatic senses: include tactile sensations, thermal sensation, pain sensations, and proprioceptive sensations
- Visceral senses: conditions within internal organs example: pressure, stretch, chemicals, nausea, hunger, and temperature
What is proprioceptive Sensation’s?
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
What are the special senses?
Sensory modalities of smell, taste, vision, hearing, and equilibrium or balance
Sensory receptor in terms of sensation?
- Either a specialized cell or dendrites of a sensory neuron
- Responds well to one particular stimulus
- Response weekly or not at all to other stimuli
Selectivity in sensory receptors?
When a receptor responds well to one particular stimuli and only weakly or not at all to other stimuli
What are the four events that need to occur for sensation to arise?
- Stimulation of the sensory receptor
- Transduction of the stimulus
- Generation of nerve impulses
- Integration of sensory input
What is transduction in a sensory receptor?
When a sensory receptor converts the energy in the stimulus into a graded potential
What are the three classes sensory receptors can be grouped into?
- Microscopic structures
- Location of the receptors and the origin of stimuli that activate them
- Type of stimulus detected
What are the three labels of microscopic structures in sensory receptors?
- Free nerve endings of first order sensory neurons
- Encapsulated nerve endings of first order sensory neurons
- Separate cells that synapse with first order sensory neurons
What are free nerve endings?
Bare (not encapsulated) dendrites that lack any structural specialization that can be seen under a light microscope
these are receptors for pain, temperature, tickle, itch, and some touch sensations
What are encapsulated nerve endings?
Dendrites are enclosed in a connective tissue capsule that has a distinctive microscopic structure these capsules enhance sensitivity or specificity of the receptor
examples: pressure, vibration, and some touch sensations
Separate cells?
Sensory receptors for special senses can be specialized separate cells that synapse with sensory neurons
including hair cells for hearing and equilibrium in the inner ear, gustatory receptors in taste buds, and photo receptors in the retina of the eye for vision
What is a receptor potential?
A graded potential generated by the sensory receptor responding to a stimulus
What are the three groups of sensory receptors based on location of the receptors and the origin of the stimuli that activate them?
- Exteroceptors: Located at or near the external surface sensitive to stimuli originating outside the body: hearing, vision, smell, taste, touch, pressure, vibration, temperature and pain
- Interoceptors or visceroceptors: Located in blood vessels, visceral organs, muscles, and nervous system. monitoring internal environment conditions not consciously perceived
- Proprioceptors: Located in muscles, tendons, joints, and the inner ear. provide information about body position, muscle length and tension, and the position and movement of your joints
What are the six groups of sensory receptors distinguished by the type of stimulus they detect?
- Mechanoceptors
- Thermoreceptors
- Nociceptors
- Photoreceptors
- Chemoreceptors
- Osmoreceptors
What is a characteristic of most sensory receptors?
Adaptation - where the receptor potential decreases in amplitude during a maintained constant stimulus
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 skeletal muscles tendons and joints
The most somatic sensory receptors are found at the tip of the tongue, the lips, and the fingertips
What’s it called when somatic sensations arise from stimulating the skin surface?
Cutaneous sensations
What are the four modalities of somatic sensation?
- Tactile
- Thermal
- Pain
- Proprioceptive
What are the tactile sensation’s?
Touch, pressure, vibration, itch, and tickle
What mediate sensations of touch, pressure, and vibration?
Encapsulated Mechanoreceptors attached to large diameter myelinated A fibres mediate sensations of touch, pressure, and vibration
Which tactile sensations are detected by free nerve endings attached to small diameter, unmylenated C fibers?
Itch and tickle
What are the two types of rapidly detecting touch receptors?
- Corpuscles of touch - Located in the dermal papillae of hairless skin. generate nerve impulses at onset of touch. abundant in fingertips, hands, eyelids, tip of the tongue, lips, nipples, soles, clitoris, and tip of the penis
- Hair route plexuses - Found in hairy skin. detect movement on the skin surface the disturb hairs
What are the two types of slowly adapting touch receptors?
- Type one cutaneous Mechanoreceptors - Plentiful in fingertips, hands, lips, and external genitalia. respond to continuous touch such as holding an object
- Type two cutaneous mechanoreceptors - Highly sensitive to skin stretching
Pressure
Sustained sensation that is felt over a larger area than touch occurs with deeper deformation of the skin and subcutaneous layer
uses type one and type two mechano receptors
Vibration
Results from rapidly repetitive sensory signals from tactile receptors
Lamellated corpuscles and corpuscals of touch
Lamellated corpuscle
Consist of a nerve ending surrounded by a multilayered connective tissue capsule the resembles a sliced onion, adapt rapidly
Itch
Stimulation of free nerve endings by certain chemicals such as bradykinin, histamine, or antigens in mosquito saliva injected from a bite often because of local inflammatory response
Tickle
Free nerve endings are thought to mediate the tickle sensation this intriguing sensation typically arises only when someone else touches you
Thermal sensation
Free nerve endings that have receptive fields about 1 mm in diameter on the skin surface that detect cold and warmth
Cold receptors
Located in the stratum basal of the epidermis attach to medium diameter myelinated A fibres
temperatures between 10° and 35°C activate cold receptors
Warm receptors
Not as abundant is cold
Located in the dermis and are attached to small diameter unmyelinated C fibres
activated by temperatures between 30° and 45°C
Pain sensations
Protective function by signalling the presence of noxious tissue damaging conditions
Nociceptors
Receptors for pain free nerve endings found in every tissue of the body except the brain. intense thermal, mechanical, or chemical stimuli can activate them
What are the two types of pain?
- Fast pain
- Slow pain
Fast pain
Occurs very rapidly usually within .1 second after stimulus is applied also known as acute pain
Slow pain
Begins a second or more after a stimulus is applied then gradually increases in intensity over a period of several seconds or minutes also known as chronic, burning, aching, or throbbing pain
Superficial somatic pain
Arises from stimulation of receptors in the skin
Deep somatic pain
Arises from stimulation of receptors in skeletal muscles, joints, tendons, and Fascia
Visceral pain
Results from stimulation of nociceptors in visceral organs, if it involves large areas it can be quite severe
Weight discrimination
The ability to assess the weight of an object to help determine the muscular effort necessary to perform the task
Proprioceptive sensations
Allow us to recognize that parts of our body belong to us, to know where our head and limbs are located and how they are moving even when not looking at them
Kinesthesia
Perception of body movements
Proprioceptors
Receptors that give rise to proprioceptive sensations they are in bedded in muscles and tendons to inform us of the degree to which muscles are contracted the amount of tension on tendons and the position of joints, Provide information for maintaining balance and equilibrium and receive nerve impulses related to the position of different body parts in order to ensure coordination
Muscle spindles
Proprioceptor’s that monitor changes in the length of skeletal muscles and participate in stretch reflexes
Consist of several slowly adapting sensory nerve endings that wrap around 3 to 10 specialized muscle fibres
Intrafusal fibers
Specialize muscle fibre
Gamma motor neurons
Motor neurons in muscle spindles Terminate near both ends of the intra-fusil fibres and adjust the tension in a muscle spindle to variations in the length of the muscle
Extrafusal muscle fibres
Ordinary skeletal muscle fibres that surround the spindles and are supplied by large diameter a fibres called Alpha motor neurons.
Where are the cell bodies of both gamma and Alpha motor neurons located?
Anterior gray horn of the spinal cord
Tendon organs
Slowly adapting receptors
located at the junction of a tendon and a muscle
by initiating tendon reflexes tendon organs protect tendons and their associated muscles from damage due to excessive tension
each tendon organ consists of a thin capsule of connective tissue that encloses a few tendon fascicles that are penetrated by sensory nerve endings
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
Joint kinaesthetic receptors
Free nerve endings and type two cutaneous Mechanoreceptors in the capsules of joints respond to pressure
Small lamellated corpuscles in the connective tissue outside articular capsule respond to acceleration and deceleration of joints during movement
Joint ligaments containing receptors similar to tendon organs that adjust reflex inhibition of the Adjacent muscles when excessive strain is placed on the joint
Somatic sensory ( somatosensory) pathways
Relay information from somatic sensory receptors to the primary somatosensory area in the parietal lobe of the cerebral cortex and to the cerebellum
What are the three neurons in the somatic sensory pathway?
- First order neuron
- Second order neuron
- Third order neuron
First-order (primary) neuron
Sensory neurons that conduct impulses from somatic sensory receptors into the brainstem or spinal cord
from the face, nasal cavity, oral cavity, teeth and eyes propagate along the cranial nerves in the brainstem
from the neck, trunk, limbs, and posterior aspect of the head Somatic sensory impulses propagate along spinal nerves into the spinal cord
Second-order (secondary) neurons
Conduct impulses from the brain stem or spinal cord to the thalamus these axons decussate (cross over to the opposite side) as they course through the brain stem or spinal cord before sending to the thalamus
Third order (tertiary) neurons
Conduct impulses from the thalamus to the primary somatosensory area on the same side as the impulses reach the primary somatosensory area perception of the sensation occurs
Relay station
Regions within the central nervous system where neuronsenops with other neurons that are part of a particular sensory or motor pathway
What are the three somatic sensory pathways that impulses ascend to the cerebral cortex?
- Posterior column-medial lemniscus pathway
- Anterolateral (spinothalamic) pathway
- Trigeminothalamic pathway
Posterior column-medial lemniscus pathway
Nerve impulses for touch, pressure, vibration, and proprioception, from the limbs trunk neck and posterior head ascend to the cerebral cortex along this pathway
First order neurons are in the posterior column medial lemniscus pathway
Anterolateral (spinothalamic) pathway
Nerve impulses for pain, temperature, itch, and tickle from the limbs trunk neck and posterior head ascend to the cerebral cortex along this pathway
What does the somatic sensory map and the somatic motor map do?
Relate body parts to these cortical areas
Trigeminothalamic pathway to cerebral cortex
Nerve impulses for most somatic sensations (tactile, thermal, pain) from the face, nasal cavity, oral cavity, and teeth ascend the cerebral cortex along the Trigeminothalamic pathway
Primary somatosensory area
Occupies the postcentral gyri of the parietal lobes of the cerebral cortex
receives sensory input from different parts of the body and maps the destination of somatic sensory signals from different parts of the left side of the body in the somatosensory area of the right cerebral hemisphere
the left cerebral hemisphere does a similar thing
Sensory homunculus
The distorted somatic sensory map of the body
the size of the cortical region that represents a body part may expand or shrink depending on the quantity of sensory impulses received from that body part
What are the major routes that the proprioceptive impulses take to reach the cerebellum?
- Anterior spinocerebellar tract
- Posterior spinocerebellar tract
Lower motor neurons
All excitatory and inhibitory signals that control movement converge on the motor neurons that extend out of the brainstem and spinal cord to innervate skeletal muscles in the body
Local circuit neurons
Located close to lower motor neuron cell bodies in brainstem and spinal cord
coordinate rhythmic activity in specific muscle groups
Upper motor neuron
An interneuron and not a true motor neuron it is so named because the cell originate in the upper part of the central nervous system regulates activity of lower motor neurons
Basal nuclei neurons
Initiate and terminate movements, suppress unwanted movements, and establish normal level of muscle tone
Cerebellar neurons
Monitors differences between intended movements and movements actually performed
then it issues commands to upper motor neurons to reduce errors in movement thus coordinating body movements and
helping maintain normal posture and balance
Premotor Area of the cerebral cortex
Is where a motor plan is developed identifying which muscles should contract how much they need to contract and in what order and then transmitted to the primary motor area for execution
Primary motor area of the cerebral cortex
The major control region for the execution of voluntary movement electrical stimulation of any point in the primary motor area causes contraction of a specific muscle on the opposite side of the body this area controls muscles by forming descending pathways that extend the spinal cord and brain stem
Direct motor pathways
Provide input to lower motor neuron sphere axons that extend directly from the cerebral cortex
Also called Pyramidal pathways
Consist of Axons that descend from the Pyramidal cells of the primary motor area and premotor area
Consist of corticospinal pathways in corticobulbar pathway is
Indirect motor pathways
Provide input to lower motor neurons from motor centres in the brain stem
Pyramidal cells
Upper motor neurons that have pyramid shaped cell bodies they are the main output cells of the cerebral cortex
Corticospinal pathways
Conduct impulses for the control of muscles of the limbs and trunk
What is the lateral corticospinal tract function?
Precise agile and highly skilled movements of hands and feet
What is the function of the anterior corticospinal tract?
Controls movement of trunk and proximal part of the limbs
What’s the function of the corticobulbar pathway?
Controls precise voluntary movements of the eyes, tongue, and neck, plus chewing, facial expressions, speech, and swallowing
What are the four major motor centres that help regulate body movement in the brainstem?
- Vestibular nuclei in the medulla and pons
- Reticular formation located throughout the brain stem
- Superior colliculus in the midbrain
- Red nucleus also present in the midbrain
Indirect motor pathways
Extrapyramidal pathways
Include all somatic motor tracks other than the corticospinal and corticobulbar tracks
Located in brainstem
- Rubrospinal tract
- Tectospinal tract
- Vestibulospinal tract
- Lateral reticulospinal tract
- Medial reticulospinal tract
What is the function of the indirect motor pathways of the brainstem?
Cause involuntary movements that regulate posture, balance, muscle tone, and reflexive movements of the head and trunk other than the rubrospinal tract which plays an ancillary role to the lateral corticospinal tract in the regulation of voluntary movements of the upper limbs
What are the three sources of input for postural reflexes?
- The eyes; which provide visual information about the position of the body in space
- The vestibular apparatus of the inner ear; which provides information about the position of the head
- Proprioceptors in muscles and joints; which provide information about the position of the limbs
What is the function of the reticular formation?
Helps control posture and alters muscle tone
receives input from eyes, ears, cerebellum, and basal nuclei
What’s the function of the Tectospinal track?
Allows the body to turn in the direction of a sudden visual or auditory stimulus; protecting from potentially dangerous stimuli
Saccades
Small rapid jerking movements of the eyes that occur as a person looks at different points in the visual field
Red nucleus
Receives input from the cerebral cortex and the cerebellum
generates action potentials along the rubrospinal tract
which activate skeletal muscles that cause fine, precise, voluntary, movements of the distal parts of the upper limbs
What are the functions of the basal nuclei?
- Initiation of movement
- Suppression of unwanted movements
- Regulation of muscle tone
- Regulation of nonmotor processes
What are the four activities of cerebellar function?
- Monitoring intentions for movement
- Monitoring actual movement
- Comparing command signals with sensory information
- Sending out corrective feedback
Integration
Function of the cerebrum
The processing of sensory information by analyzing and storing it and making decisions for various responses
What are the integrative functions?
- Sleep and wakefulness
- Learning and memory
- Language
During REM sleep does blood pressure respiratory and heart rate increase or decrease?
Increase
During NREM sleep does respiratory, heart rate, and blood pressure increase or decrease?
Decrease
Does most dreaming occur in REM sleep or NREM sleep?
REM
Where is the NREM sleep centres located?
In the hypothalamus and basal forebrain
Where is the REM sleep centre located?
Ponds and mid brain
What are the proposed functions of sleep?
- Restoration; providing time for the body to repair it self
- Consolidation of memories
- Enhancement of immune system function
- Maturation of the brain
Coma definition
A state of unconsciousness in which an individual has little or no response to stimuli
Causes of comas
Head injuries, damages to the reticular activating system, brain infection, alcohol intoxication, and drug overdoses
Persistent vegetative state
Patient has normal sleep wake cycles but does not have an awareness of the surroundings
can smile, laugh, or cry but do not understand the meaning of these actions
EEG still exhibit waveform activity
Learning
The ability to acquire new information or skills through instruction or experience
two main categories being associative learning and non-associative learning
Associative learning
Occurs when a connection is made between two stimuli
Non-associative learning
Occurs when repeated exposure to a single stimulus causes a change in behaviour
Habituation
Repeated exposure to an irrelevant stimulus causes a decreased behavioural response
Sensitization
Repeated exposure to a noxious stimulus causes an increase behavioural response
Memory
The process by which information acquired through learning is stored and retrieved
Declarative (explicit) memory
Is the memory of experiences that can be verbalized such as facts, events, objects, names, and places
requires conscious recall and is stored in the association areas of the cerebral cortex
Procedural (implicit) memory
The memory of motor skills procedures and rules
does not require conscious recall and it is stored in the basal nuclei, cerebellum, and Premotor area
Short term memory
The temporary ability to recall a few pieces of information for seconds to minutes
Long-term memory
Last from days to years
Memory consolidation
The process by which a short term memory is transformed into a long-term memory
a major role is played by the hippocampus
Plasticity
For an experience to become part of a long-term memory it must produce persistent structural and functional changes that represent the experience in the brain
it involves changes of individual neurons as well as changes in the strengths of synaptic connections among neurons
Long-term potentiation (LTP)
Underlies some aspects of memory transmission at some synapses within the hippocampus is enhanced for hours or weeks after a brief period of high frequency stimulation
Language
A system of vocal sounds and symbols that conveys information most commonly it is spoken and or written
What are the two language areas of the cerebral cortex?
Wernick’s area and Brocas area
Wernick’s area
An association area found in the temporal lobe interprets the meaning of written or spoken words
translate words into thoughts
Brocas area
A motor area located in the frontal lobe is active as you translate thoughts into speech
Brocas area receives input from Wernicks area and then generates a motor pattern for activation of muscles needed for the words that you want to say
What are the neural pathways used when you see or hear a particular word and then say that word?
- Information about the word is conveyed to the Wernick’s area
- Wernicks’s area translates the written or spoken word into the appropriate thought
- To speak the word Wernick’s area transmits information about the word to Brocas area
- Brocas area receives input and then develops a motor pattern for activation of the muscles needed to say the word
- Motor pattern is conveyed from Brokas area to the primary motor area which subsequently activates the appropriate muscles of speech, contraction of the speech muscles allows the word to be spoken
