Chapter 16 - Sensory, Motor & Integrative Systems Flashcards
What is sensation?
The conscious or subconscious awareness of changes in the external or internal environment
What is perception?
The conscious awareness & interpretation of sensations
- function of cerebral cortex
What is sensory modality?
Each unique type of sensation
- touch, pain, vision, hearing
If a neuron relays impulses for touch, will it also relay for pain?
NO!
- a given sensory neuron carries information for only one sensory modality
What are general senses?
Refer to both somatic senses & visceral senses
What are somatic senses?
Tactile sensations (touch, pressure, vibration, itch & tickle) Thermal sensations (warm/cold) Pain sensations Proprioceptive sensations
What information do visceral senses provide?
Provide information about conditions within internal organs
pressure, stretch, chemicals, nausea, hunger, temperature
What are the special senses?
Smell, taste, hearing, vision, equilibrium/balance
How does a sensation arise?
- Stimulation of the sensory receptor
- Transduction of the stimulus
- Generation of nerve impulse
- Integration of sensory input
What is a sensory receptor?
A specialized cell or the dendrites of a sensory neuron
What is a stimulus?
A change in the environment that can activate certain sensory receptors
What is selectivity?
How a sensory receptor will react to one stimulus and weakly or not at all to other stimuli
What is the receptive field?
The body region where stimulation activates the receptor and produces a response
What are first-order neurons?
Sensory neurons that conduct impulses from the PNS into the CNS
What are the classification types of sensory receptors?
- Microscopic structure
- Location of the receptors & their origin of stimuli that activate them
- Type of stimulus detected
What are the three types of microscopic structures of 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 dendrites
- lack any structural specializations
What are some examples of free nerve endings?
Receptors for pain, temperature, tickle, itch, and some touch sensations
What are encapsulated nerve endings?
Dendrites that are enclosed in a connective tissue capsule
What are some examples of encapsulated nerve endings?
Receptors for pressure, vibration, and some touch sensations
What are separate cells? (sensory receptors)
Sensory receptors for specialized senses that are specialized
- synapse with sensory neurons
What are some example of separate cells? (sensory receptors)
Hair cells - for hearing & equilibrium in ear
Gustatory receptor cells - taste buds
Photoreceptors - for vision in the eye
Sensory receptors produce what two kinds of graded potentials?
- Generator potentials
2. Receptor potentials
What is a generator potential?
Dendrites of free & encapsulated nerve endings
- when a generator potential is large enough to reach threshold, it triggers one or more nerve impulses in the axon of the first-order sensory neuron
What do generator potentials generate?
Action potentials
What is a receptor potential?
Separate cells produce receptor potentials
- trigger release of neurotransmitter though exocytosis of synaptic vesicles
What are the three location types of sensory receptors?
- Exteroceptors
- Interoceptors
- Proprioceptors
What are exteroceptors sensitive to?
Where are they located?
Located at or near the external surface of the body
- sensitive to stimuli originating outside the body
- provide information on external environment
What are examples of exteroceptors?
Sensations for hearing, vision, smell, taste, touch, pressure, vibration, temperature, and pain
What do interoceptors monitor?
Where are they located?
Located in blood vessels, visceral organs, muscles, and the nervous system
- monitor conditions on the internal environment
- not usually consciously perceived
What information do proprioceptors provide?
Where are they located?
Located in muscles, tendons, joints, and inner ear
- provide information about body position, muscle length and tension, and position and movement of joints
What are the 6 Stimulus Detected types of sensory receptors?
- Mechanoreceptors
- Thermoreceptors
- Nociceptors
- Photoreceptors
- Chemoreceptors
- Osmoreceptors
What are mechanoreceptors sensitive to?
Mechanical stimuli
- deformation, stretching, bending
What sensations do mechanoreceptors provide?
Touch, pressure, vibration, proprioception, hearing, equilibrium
- monitor stretching of blood vessels & internal organs
What do themoreceptors detect?
Changes in temperature
What are nociceptors responsive to?
Respond to painful stimuli resulting from physical or chemical damage
What do photoreceptors detect?
Light that strikes the retina of the eye
What do chemoreceptors detect?
Chemicals in the mouth (taste), nose (smell) and body fluids
What do osmoreceptors detect?
Osmotic pressure of body fluids
What is a characteristic of most sensory receptors?
Adaptation
What is adaptation?
The generator potential or receptor potential decreases in amplitude during a maintained, constant stimulus
What causes the perception of a sensation to fade/dissappear even though the stimulus persists?
Adaptation
What are rapidly adapting receptors?
Adapt very quickly
- specialized for signaling CHANGES in a stimulus
Give some examples of rapidly adapting receptors.
Pressure, touch, and smell
What are slowly adapting receptors?
Adapt slowly
- Continue to trigger nerve impulses as long as the stimulus persists
Give some example of slowly adapting receptors.
Receptors that monitor stimuli associated with pain, body position, and chemical composition of the blood
What is a phasic receptor?
A rapidly adapting receptor
What is a tonic receptor?
A slowly adapting receptor
What are cutaneous sensations?
Somatic sensations that arise from stimulating the skin surface
What are the 4 modalities of somatic sensation?
- Tactile
- Thermal
- Pain
- Proprioceptive
Where do somatic sensations arise?
Arise from stimulation of sensory receptors embedded in the skin or subcutaneous layer, mucous membranes (mouth, vagina, anus), muscles, tendons, joints, inner ear
What are the tactile sensations?
Touch, pressure, vibration, itch & tickle
What are some examples of tactile receptors in the skin/subcutaneous layer? (6)
Meissner corpuscles Hair root plexuses Merkel discs Ruffini corpuscles Pacinian corpuscles Free nerve endings
How does the sensation of touch arise?
Generally from stimulation of tactile receptors in the skin or subcutaneous layer
What are the two types of rapidly adapting touch receptors?
- Meissner corpuscles
2. Hair root plexuses
What are meissner corpuscles?
Where are they located?
Touch receptors (rapidly adapting)
- mass of dendrites enclosed by a capsule of connective tissue
- located in the dermal papillae of hairless skin
Where are meissner corpuscles abundant?
Fingertips, hands, eyelids, tip of tongue, lips, nipples, soles, clitoris, tip of penis
What are hair root plexuses?
Touch receptors (rapidly adapting)
- found in hairy skin
- free nerve endings wrapped around hair follicles
What are the two types of slowly adapting touch receptors?
- Merkel discs
2. Ruffini corpuscles
What are Merkel discs?
Where are they located?
Tactile discs (Type I)
- saucer-shaped, flattened free nerve endings
- make contact with merkel cells in stratum basale
Where are merkel discs abundant?
Fingertips, hands, lips, external genitalia
What are Ruffini corpuscles?
Where are they located?
Type II
- elongated, encapsulated receptors
- located deep in the dermis & in ligaments & tendons
Where are Ruffini corpusces abundant?
Where are they absent?
Present in hands
Absent in soles
What are Ruffini corpuscles most sensitive to?
Stretching that occurs as digits or limbs are moved
What is pressure?
A sustained sensation that is felt over a larger area than touch
- occurs with deformation of deeper tissues
What are the receptors that contribute to sensations of pressure?
- Meissner corpuscles
- Merkel discs
- Pacinian corpuscles
What are pacinian corpuscles composed of? (lamellated)
Large oval structure composed of multilayered connective tissue capsule that encloses a dendrite
Are Pacinian corpuscles rapidly or slowly adapting?
Rapidly
Where are Pacinian corpuscles located?
Dermis & subcutaneous layer Submucosal tissues (under mucous & serous membranes) Joints, tendons & muscles Periosteum Mammary glands External genitalia Pancreas & urinary bladder
How do sensations of vibrations arise?
Result from rapidly repetitive sensory signals from tactile receptors
What are the receptors for vibration?
- Meissner corpuscles - lower frequency vibrations
2. Pacinian corpuscles - higher frequency vibrations
How does the itch sensation arise?
Results from stimulation of free nerve endings by certain chemicals
- often b/c of local inflammatory reponse
What is an example of an itch sensation?
Anitgens in mosquito bites
What mediates the tickle sensation?
Free nerve endings
What is the phantom limb sensation?
Individuals who still perceive sensations (itching, pressure, tingling or pain) in an amputated limb
How is the phantom limb sensation activated?
Severed endings of sensory axons are still present in the remaining stump
- if they are activated, the cerebral cortex interprets the sensation as coming from the sensory receptors in the non-existing limb
What is the other explanation for phantom limb sensation?
The cerebral cortex undergoes extensive functional reorganization that allows it to respond to stimuli from another body part
- gives rise to false sensory perceptions
What are themoreceptors?
Free nerve endings, sense hot & cold
- adapt rapidly at the onset of a stimulus
- receptive fields about 1 mm in diameter on the skin surface
What are the two kinds of themoreceptors?
- Cold receptors
2. Warm receptors
Where are cold receptors located?
In the stratum basale of the epidermis
- connected to myelinated A fibres
- few connected to unmyelinated C fibres
What temperatures activate cold receptors?
10 - 40 degrees Celsius
Where are warm receptors located?
In the dermis
- connected to unmyelinated C fibres
What temperatures activate warm receptors?
32 - 48 degrees Celsius
What happens at temperatures below 10 and above 48 degrees celsius?
Pain receptors are stimulated
What is the function of pain receptors?
Protective function
- signals the presence of noxious, tissue-damaging conditions
What are nociceptors?
Pain receptors
- free nerve endings
Where are nociceptors located?
In every tissue, except brain tissue
What can activate nociceptors?
Intense thermal, mechanical or chemical stimuli
Why can pain persist even after a pain-producing stimulus is removed?
B/c pain-mediating chemicals linger
B/c nociceptors exhibit very little adaptation
What are the two kinds of pain?
- Fast
2. Slow
Describe fast pain.
how fast it occurs, type of fibre
Occurs very rapidly, within 0.1 seconds after a stimulus is applied
- nerve impulses propagate along myelinated A fibres
How can fast pain be described?
Acute, sharp, pricking pain
- needle prick, knife cut
Describe slow pain.
how fast it occurs, type of fibre
Begins a second or more after the stimulus is applied
- gradually increases in intestity over seconds/minutes
- along unmyelinated C fibres
How can slow pain be described?
Chronic, burning, aching, throbbing
- skin deep or within organs
What is superficial somatic pain?
Pain that arises from stimulation of receptors in the skin
What is deep somatic pain?
Pain that arises from stimulation in skeletal muscles, joints, tendons, & fascia
What is visceral pain?
Pain that arises from stimulation of nociceptors in visceral organs
What does diffuse mean?
Involves large areas
True or false?
Fast pain is more diffuse.
False!
Fast pain is very precisely localized to the stimulated area
What is referred pain?
Pain is felt in or just deep to the skin that overlies the stimulated organ
- visceral pain
What do proprioceptive sensations allow us to do?
Know where our head and limbs are located and how they are moving without looking at them
What is kinesthesia?
The perception of body movements
What are proprioceptors?
Receptors for proprioceptive sensations
Do proprioceptors adapt rapidly or slowly?
Slowly!
- Slowly and only slightly
- brain continually receives nerve impulses related to the position of different body parts and makes adjustments to ensure coordination
What are muscle spindles?
What do they monitor?
Proprioceptors in skeletal muscles
- monitor changes in the length of skeletal muscles & participate in stretch reflexes
What is muscle tone?
Small degree of constraction that is present while the muscle is at rest
What are intrafusal muscle fibres?
Skeletal muscle fibers that serve as specialized sensory organs (proprioceptors) that detect the amount and rate of change in length of a muscle.
What does each muscle spindle consist of?
Several slowly adapting sensory nerve endings that wrap around 3 - 10 specialized muscle fibers
Where are muscle spindles abundant?
In muscles that produce finely controlled movements
What are gamma motor neurons?
Motor neurons that terminate near both ends of the intrafusal fibers and adjust the tension in a muscle spindle to variations in the length of the muscle
- receive input from CNS
What are extrafusal muscle fibers?
Ordinary skeletal muscle fibers that surround muscle spindles
What are alpha motor neurons?
Innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their contraction.
- receive input from CNS
Where are tendon organs located?
At the junction of a tendon & a muscle
What is the function of tendon organs?
Protect tendons & their associated muscles from damage due to excessive tension
- slow adaptation
What are joint kinesthetic receptors?
Free nerve endings & Ruffini corpuscles
- respond to pressure
Pacinian corpuscles
- respond to acceleration and deceleration of joints during movement
Tendon organs
- adjust reflex inhibition of adjacent muscles when excessive strain is placed on the joint
Where are joint kinesthetic receptors located?
Within and around the articular cartilage of synovial joints
What do somatic sensory pathways relay?
Information from the somatic sensory receptors to the primary somatosensory area in the cerebral cortex & cerebellum
What are the set of three neurons?
- First-order
- Second-order
- Third-order
What do first-order neurons do?
Conduct impulses from somatic receptors into the brain stem or spinal cord
- cranial nerves: face, mouth, teeth, eyes
- spinal nerves: neck, trunk, limbs, posterior aspect of head
What is the function of second-order neurons?
Conduct impulses from the brain stem & spinal cord to the thalamus
Which order of neurons decussate?
Second-order
- cross over to the opposite side in the brain stem or spinal cord before ascending to thalamus
What is the function of third-order neurons?
Conduct impulses from the thalamus to the primary somatosensory area of the cortex on the same side
What are the three ways that somatic sensory impulses ascend to the cerebral cortex?
- Posterior column - medial lemniscus pathway
- Anterolateral (spinothalamic)
- Trigeminothalamic
Which nerve impulses ascend along the posterior column - medial lemniscus pathway?
Nerve impulses for touch, pressure, vibration, and conscious proprioception
- all three orders of neurons
Which nerve impulses ascend along the anterlater (spinothalamic) pathway?
Nerve impulses for pain, temperature, itch & tickle from the limbs, trunk, neck & posterior head ascend to cerebral cortex
- all three orders of neurons
Which nerve impulses ascend along the trigeminothalamic pathways?
Nerve impulses for somatic sensations (tactile, thermal, pain) from the face, nasal cavity, oral cavity and teeth
Where is the primary somatosensory area located?
Occupies the postcentral gyri of the parietal lobes of the cerebral cortex
What does each region of the primary somatosensory area receive?
Sensory input from a different part of the body
- left side of body = right cerebral hemisphere
Which parts of the body provide input to large regions of the primary somatosensory area?
Lips, face, tongue and hand
What is sensory homunculus?
Distorted sensory map of the body
- large regions for lips
- small regions for trunk
What are the two routes that proprioceptive impulses take to reach the cerebellum?
- Posterior spinocerebellar tract
2. Anterior spinocerebellar tract
What sensory impulses are conveyed along the posterior and anterior spinocerebellar tracts?
Critical for posture, balance, and coordination of skilled movements
What are lower motor neurons? (LMN)
- cell bodies in the brain stem & spinal cord
- axons extend through CRANIAL nerves to innervate skeletal muscles of the face & head
- axons extend through SPINAL nerves to innervate skeletal muscles of limbs & trunk
Which type of motor neuron provides output from the CNS to skeletal muscle fibers?
Lower motor neurons
What are upper motor neurons? (UMN)
- Essential for the execution of voluntary movements of the body (UMN from cerebral cortex)
- Regulate muscle tone, control postural muscles, & help maintain balance (UMN from brain stem)
What are the 4 neural circuits that participate in control of movement by providing input to lower motor neurons?
Somatic motor pathways
- Local circuit neurons
- Upper motor neurons
- Basal nuclei neurons
- Cerebellar neurons
What are the two kinds of somatic motor pathways?
- Direct motor pathways
2. Indirect motor pathways
What do direct motor pathways provide input to?
To lower motor neurons via axons that extend directly from the cerebral cortex
What do indirect motor pathways provide input to?
To lower motor neurons from motor centers in the basal nuclei, cerebellum & cerebral cortex
Where is the primary motor area located and what is it’s function?
- Located in the precentral gyrus of the frontal lobe
- Major control region for the execution of voluntary movements
What do direct motor pathways consist of?
Corticospinal pathway & corticobulbar pathway
What are the pathway functions of the lateral corticospinal pathway?
Conveys nerve impulses from motor cortex to skeletal muscles on opposite side of body
- precise, voluntary movements of distal parts of limbs
What are the pathway functions of the anterior corticospinal pathway?
Conveys nerve impulses from motor cortex to skeletal muscles on opposite side of body
- movements of trunk, and proximal parts of limbs
What are the pathway functions of the corticobulbar pathway?
Conveys nerve impulses from motor cortex to skeletal muscles of head & neck
- coordinate precise, voluntary movements
What are the 4 indirect pathways?
What are their pathway functions?
- Rubrospinal - precise, voluntary movements of distal parts of upper limbs
- Tectospinal - move head, eyes & trunk in response to visual & auditory stimuli
- Vestibulospinal - maintains posture & balance, in response to head movements
- Medial & lateral reticulospinal - maintains posture & regulates muscle tone
What are the functions of the basal ganglia?
- Major role in the initiation & termination of movements
- Suppress unwanted movements by their inhibitory effects
- Influence muscle tone
- Help initiate & terminate some cognitive processes (attention, memory, & planning)
- Regulate emotional behaviours
The cerebellum function involves which 4 activities?
- monitoring intentions for movement
- monitoring actual movement
- comparing command signals with sensory information
- sending out corrective feedback
What are the integrative functions of the cerebrum?
- sleep & wakefulness
- learning & memory
- emotional responses
What is the circadian rhythm and how is it established?
24 hour cycle (sleep & wakefulness)
- established by the suprachiasmatic nucleus of the hypothalamus
What is the reticular activating system (RAS) responsible for?
Responsible for regulating wakefulness and sleep-wake transitions
What is arousal and what does it involve?
Awakening from sleep
- involves increased activity in the RAS
In order for arousal to occur, what must be stimulated?
The RAS
- once the RAS is activated, the cerebral cortex is activated and then arousal occurs
What is consciousness?
State of wakefulness
Which sense does not result in the stimulation of the RAS?
Olfactory receptors
- strong odors may fail to cause arousal
What is sleep?
A state of altered consciousness or partial unconsciousness from which an individual can be aroused
What does sleep deprivation impair?
Attention, learning, & performance
What are the 4 stages of NREM?
non-rapid eye movement
- Transition stage between wakfulness & sleep
- Light sleep - person is more difficult to awaken
- Moderate deep sleep - body temperature & blood pressure decreases
- Deep sleep -brain metabolism decreases, reflexes are intact
During a typical 7 or 8 hour sleep period, how many episodes of REM sleep are there?
3-5
What is REM sleep?
Rapid eye movement
- eyes move rapidly back and forth under closed eyelids
When dos REM sleep occur?
A person will ascend through stages 3 and 2 before entering REM sleep
How much REM sleep does an adult have in a typical night?
90-120 minutes
Do dreams occur in NREM or REM sleep?
REM sleep
When does sleep walking occur?
NREM - stage 4 (deep sleep)
What is learning?
The ability to acquire new information or skills through instruction or experience
What is memory?
The process by which information acquired through learning is stored & received
What is plasticity?
Ability to change our behaviors in response to stimuli from the external & internal environments
What is immediate memory?
The ability to recall ongoing experiences for a few seconds
- allows us to know where we are & what we are doing
What is short term memory?
Temporary ability to recall a few pieces of information for seconds to minutes
What is long term memory?
A more permanent type of memory
- can last days to years
What is memory consolidation?
Reinforcement that results from the frequent retrieval of a piece of information
What is long-term potentiation (LTP)?
Believed to underlie 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
What is parkinson disease?
Progressive disorder of CNS
- involuntary skeletal muscle contractions oftern interfere with voluntary movements
- slowness of movements
- decreased range of motion
What is cerebral palsy?
Motor disorder that results in the loss of muscle control and coordination
- caused by damage of the motor areas of the brain during fetal life, birth or infancy
What is insomnia?
Difficulty in falling asleep or staying asleep
- causes: stress, caffeine, disruption of circadian rhythms, depression
What is narcolepsy?
REM sleep cannot be inhibited during waking periods
- involuntary periods of sleep that last about 15 minutes occur throughout the day
What is sleep apnea?
A disorder in which a person repeatedly stops breathing for 10 or more seconds while sleeping
- occurs b/c a loss of muscle tone in pharyngeal muscles allows the airways to collapse
