Chapter 16: Sensory, Motor, and Integrative Systems

Question 1

Differentiate between sensation and perception

Answer 1

Sensation is the conscious or subconscious awareness of changes in the external or internal environment

Perception is the conscious interpretation of sensations and is primarily a function of the cortex

Question 2

Describe the two groups of sensory modalities

Answer 2

Sensory modality is a unique type of sensation (touch, pain, etc.

1. General senses refers to both somatic senses and visceral senses
2. Special senses refers to smell, taste, vision, hearing, and equilbrium

Question 3

Define somatic senses

Answer 3

Tactile sensations, thermal sensations, pain sensations, and proprioceptive sensations

Question 4

Define visceral sensations

Answer 4

Provide info about the conditions within internal organs

Question 5

A sensory receptor responds only weakly or not at all to other stimuli. What is this characteristic called?

Answer 5

selectivity

Question 6

List the 3 ways sensory receptors can be grouped into called

Answer 6

1. microscopic structure
2. location of receptors and origin of stimuli that activate them
3. type of stimulus detected

Question 7

On a microscopic level, sensory receptors may be one of which types? (3)

Answer 7

1. Free nerve endings of first-order sensory neurons
2. Encapsulated nerve endings of first-order sensory neurons
3. Separate cells that synapse with first-order sensory neurons

Question 8

Define free nerve endings

Answer 8

Bare dendrites; they lack any structural specialization that can be seen under a light microscope

Ex. receptors for pain, temp, tickle, itch, and some touch sensations

Question 9

Define encapsulated nerve endings

Answer 9

Dendrites are enclosed in a connective tissue capsule that has a distinctive microscopic structure

the different type of capsules enhance the sensitivity or specificity of the receptor

Ex. pressure, vibration, and some touch sensations

Question 10

Define separate cells

Answer 10

Sensory receptors for some special senses are separate cells that synapse with sensory neurons

Ex. hair cells in inner ear, gustatory cells in taste buds, photoreceptors in retina

Question 11

Define generator potential

Answer 11

Stimulated free or encapsulated endings generate a potential and when large enough to reach threshold, it triggers one or more nerve impulse in the axon of a first-order sensory neuron that propagates to CNS

Question 12

Define receptor potential

Answer 12

Sensory receptors that are separate cells produce graded potential that triggers release of NT through exocytosis which then produce a PSP int he first0order neuron that may trigger one more more impulses to CNS

Question 13

Describe the 3 ways sensory receptors are classified based on their receptor location and activating stimuli

Answer 13

Exoreceptors - located at or near body surface; sensitive to stimuli originating outside the body provide info about external environment

Interoceptors - located in blood vessels, visceral organs, and nervous system; provide info about internal environment; impsules usually not consciously perceived

Proprioceptors - located in muscles, tendons, joint, and inner ear; provide info about body positions, muscle length and tension, position and motion of joints, and equilibrium

Question 14

Describe the 6 way sensory receptors are classified based on the type of stimulus detected

Answer 14

Mechanoreceptors - detect mechanical stimuli (touch, pressure, vibration, proprioception, hearing, equilibrium, and stretching of internal organs)
Thermoreceptors - detect changes in temp
Nocioceptors - respond to painful stimuli resulting from physical or chemical damage
Photoreceptors - detect light that stringed the retina
Chemoreceptors - detect chemicals in the mouth, nose, and body fluids
Osmoreceptors - detect osmotic pressure of the body

Question 15

Describe adaptation characteristic in sensory receptors

Answer 15

Generator or receptor potential decreases in amplitude during a maintaining, constant stimulus causning frequency of impulses to decrease

Ex. A hot shower sensation decreases as you become comfortable with the warmth even though the temp has not changes

Question 16

What is the difference between rapidly adapting and slowly adapting receptors?

Answer 16

Rapidly adapting receptors adapt quickly - they are specialized for signalling changes in a stimulus (pressure, touch, smell)

Slowly adapting receptors adapt slowly and continue to trigger nerve impulses as long as the stimulus persist (pain, body position, chemical composition of the blood)

Question 17

What is the difference between somatic sensations and cutaneous sensations?

Answer 17

Somatic sensations arise from stimulation of sensory receptors embedded ni the skin of subQ layer; in mucous membranes; in muscles, tendons, joints; and inner ear

Somatic sensations that arise from stimulating the skin surface are cutaneous sensations

Question 18

List the 4 modalities of somatic sensation?

Answer 18

tactile
thermal
pain
proprocepttive

Question 19

Describe Corpuscles of touch (meissner corpuscles)

Answer 19

A tactile receptor (touch)

Capsule surrounds mass of dendrites in dermal papillae of hairless skin

Sensations: touch, pressure, slow vibrations

Adaptation rate: rapid

Question 20

Describe hair root plexuses

Answer 20

A tactile receptor (touch)

Free nerve endings wrapped around hair follicles in skin

Sensations: touch

Adaptation rate: rapid

Question 21

Describe Type I cutaneous mechoreceptors (Merkel discs)

Answer 21

A tactile receptor (touch)

Saucer-shaped free nerve endings make contact with tactile epithelial cells in epidermis

Sensations: touch, pressure

Adaptation rate: slow

Question 22

Describe type II cutaneous mechoreceptors (Ruffini corpuscles)

Answer 22

A tactile receptor (touch)

Elongated capsule surrounds dendrites deep in dermis and in ligaments and tendons

Sensations: touch, stretching of the skin

Adaptation rate: slow

Question 23

Describe lamellate for Pacinian corpuscle

Answer 23

A tactile receptor (pressure)

Oval, layered capsule surrounded dendrites; present in dermis and subQ layer, submucosal tissues, joints, periosteum, and some viscera

Sensations: pressure and fast vibrations

Adaptation rate: rapid

Question 24

Describe itch and tickle receptors

Answer 24

A tactile receptor

Free nerve endings in skin and mucous membrane

Sensations: itching and tickling

Adaptation rate: rapid and slow

Question 25

Describe vibration sensations

Answer 25

Receptors for vibrations are corpuscles of touch (low freq vibrations) and lamellate corpuscles (high freq vibrations)

Question 26

Describe phantom limb sensation

Answer 26

After amputation, person may still experience sensations as if the limb were still there Severed endings of sensory axons are still present in the remaining stump and if activated the cortex interpret the sensation

Question 27

Describe theroreceptors and the two distinct thermal sensations - coldness and warmth

Answer 27

Thermoreceptors are free nerve endings that have receptive fields on the surface of the skin Cold receptors are located in the stratum basal of the epidermis and are attached to myelinated A fibers and a few unmyelinated C fibers (10-40C) Warm receptors are not as abundant and are located in the dermis and are attached to unmyelinated C fibers (32-48C) Temperatures below 10C primarily stimulate pain receptors rather than thermorecepotrs

Question 28

Describe nocioceptors

Answer 28

Pain receptors Free nerve endings in every body tissue except the brain Adaption: slow

Question 29

Differentiate between fast and slow pain

Answer 29

Fast pain occurs rapidly (~0.1s) because the nerve impsulses propagate along myelinated A fibers - sharp, acute pain Slow pain begins +1 sec after and gradually increases in intensity as impulses are conducted along unmyelinated C fibers - chronic, burning, aching

Question 30

Describe superficial and deep somatic pain

Answer 30

Superficial - pain that arises from stimulation of receptors in the skin Deep - stimulation of receptors in skeletal muscles, joints, tendons, and fascia

Question 31

Describe visceral pain

Answer 31

Results from stimulation of nociceptors in visceral organs

Question 32

Define referred pain

Answer 32

In instances of visceral pain, the pain is often felt in or just deep to the skin that overlies the stimulated organ or in a surface area far from the stimlated organ

Question 33

Define kinestheisa

Answer 33

The perception of body movements

Question 34

Define proprioceptors

Answer 34

Embedded in muscles (especially postural muskies) and teens andimform us of the degree to which muscles are contracted, the amount of tension, and the position of joints

Question 35

Describe muscle spindles

Answer 35

Receptor type: proprioceptor Sensory nerve endings wrap around central area of encapsulated intramural muscle fibers within most skeletal muscles Sensations: muscle length Adaptation: slow

Question 36

Describe tendon organs

Answer 36

Receptor type: proprioceptor Capsule encloses collagen fibers and sensory nerve ending at junction of tendon and muscle Sensations: muscle tension Adaptation: slow When a muscle contracts, it exerts a force that pulls the point s of attachment at either end toward each other to protect from excessive tension

Question 37

Describe joint kinaesthetic receptor

Answer 37

Several types are present within and around the articular capsules of joins Free nerve endings and type II cretinous mechanoreceptors respond to pressure Small lamellated corpuscles in connective tissue respond to acceleration/deceleration of joints during movement

Question 38

Define intrafusal fibers

Answer 38

Each muscle spindle consists of several slowly adapting sensory nerve endings that wrap around 3-10 specialized muscle fibers, called intrafusal fibers Connective tissue incomes this and anchors the spindle to the endomysium and perimysium

Question 39

Define gamma motor neurons

Answer 39

These terminate near both ends of the intrafusal fibers and adjust the tension in a muscle spindle to variations in the length of the muscle This maintains sensitivity of the muscle spindle to stretching

Question 40

Define extrafusal muscle fibers and alpha motor neurons

Answer 40

Extrafusal muscle fibers are ordinary skeletal muscle fibers that surround muscle sponges They are supplied by large diameter A fibers called alpha motor neurons During a stretch reflex alpha motor neurons are activates that connect to extrafusal muscle fibers int he same muscle, causing contraction which receives the stretching

Question 41

How is a muscle spindle activated?

Answer 41

When the central areas of the intrafusal fibers are stretched

Question 42

Describe the sets of of 3 neurons (1st, 2nd, 3rd) in a somatic sensory pathway

Answer 42

First-order neuron - conduct impulses from somatic receptors into the brainstem or spinal cord Second-order neuron - conduct impulses form the brainstem and spinal cord to thalamus; axons decussate in the brainstem or spinal cord before ascending to thalamus Third order neuron - conduct impulses from thalamus to primary somatosensory area of the cortex on same side

Question 43

Define relay stations

Answer 43

Regions within the CNS where neurons synapse with other neurons that are part of a particular sensory or motor pathway Names as such because neuronal signal are being relayed from one region to another

Question 44

Describe the posterior column-medial lemniscus pathway

Answer 44

Consists of 2 tracts: - cuneate fasiculus: conveys impulses for touch, pressure, vibration and conscious proprioception from limbs, trunk, neck, and posterior head ascend along this pathway - Gracile fasiculus: covers nerve impulses for touch, pressure, and vibration for lower limbs and lower trunk Axons of first-order neurons from one side of body form posterior column on same side and end in medulla, where they synapse with dendrites and cell bodies of second-order neurons. Axons of second-order neurons decussate, enter medial lemniscus on opposite side, and extend to thalamus Third-order neurons transmit nerve impulses from thalamus to primary somatosensory cortex on side opposite the site of stimulation.

Question 45

Describe the anterolateral (spintothalamic) pathway

Answer 45

Conveys nerve impulses for pain, cold, warmth, itch, and tickle from limbs, trunk, neck, and posterior head. Axons of first-order neurons from one side of body synapse with dendrites and cell bodies of second-order neurons in posterior gray horn on same side of body. Axons of second-order neurons decussate, enter spinothalamic tract on opposite side, and extend to thalamus. Third-order neurons transmit nerve impulses from thalamus to primary somatosensory cortex on side opposite the site of stimulation.

Question 46

Describe the trigenimothalamic pathway

Answer 46

Conveys nerve impulses for touch, pressure, vibration, pain, cold, warmth, itch, and tickle from face, nasal cavity, oral cavity, and teeth. Axons of first-order neurons from one side of head synapse with dendrites and cell bodies of second-order neurons in pons and medulla on same side of head. Axons of second-order neurons decussate, enter trigeminothalamic tract on opposite side, and extend to thalamus. Third-order neurons transmit nerve impulses from thalamus to primary somatosensory cortex on side opposite the site of stimulation.

Question 47

Where is the primary somatosensory area located?

Answer 47

The postcentral gyri of the parietal lobes of the cerebral cortex Each region receives sensory input from a different part of the body Some parts of the body (lips, face, tongue, hand) provide input to large regions in the somatosensory area

Question 48

How do the somatosensory and motor representations compare for the hand, and what does this difference imply?

Answer 48

Hand has a larger representation in the motor area which implies greater precision in the hands movement control than fine ability in its sensation

Question 49

Describe the posterior and anterior spinocerebellar tract

Answer 49

Convey nerve impulses from proprioceptors in trunk and lower limb of one side of body to same side of cerebellum. Proprioceptive input informs cerebellum of actual movements, allowing it to coordinate, smooth, and refine skilled movements and maintain posture and balance.

Question 50

Define lower motor neurons

Answer 50

Have their cell bodies in the brainstem and spinal cord and extend through cranial nerves to innervate skeletal muscles of the face and head and extend through spinal nerves to innervate muscles of the limbs and trunk

Question 51

Describe local circuit nuerons

Answer 51

Interneurons which receive their input from sensory receptors and innervate lower motor neurons Located in the brainstem and spinal cord They help coordinate rhymes activity in specific muscle groups (ex. flexion and extension during walking)

Question 52

Describe upper motor neurons

Answer 52

Innervate local circuit neurons and lower motor neurons - mostly synapse with local circuit neurons UMNs from cortex are essential for execution of voluntary movements and other UMNs originate in motor center of the brain stem which help regulate muscle tone, control posture, and help balance the head and body

Question 53

Describe the function of basal nuclei neurones - how are they connected to the somatic motor pathway?

Answer 53

Assist movement by providing input to UMNs They are interconnected with the motor areas of the cortex via the thalamus and the brainstem and thus help initiate and terminate movements and establish muscle tone

Question 54

Where is the primary motor area located?

Answer 54

The precentral gyrus of the frontal lobe

Question 55

Compare the locations and functions of the direct and indirect motor pathways

Answer 55

Direct - provide input to LMNs from motor neurons via axons that extend directly from the cerebral cortex; consist of axons that descend from pyramidal cells which are UMNs with pyramidal shaped cell bodies located in the primary motor area and premotor area Indirect - provide input to LMNs from motor centres in the basal ganglia, cerebellum and cerebral cortex Both govern generation of impulses in LMNs which stimulate contraction of skeletal muscles

Question 56

What is the final common pathway?

Answer 56

LMNS as they provide all output to skeletal muscles

Question 57

Explain how the basal ganglia contributes to movement

Answer 57

Initiation and termination of movement - receives input from sensory, association, and motor areas of the cortex and from substania nigra and sends feedback to UMNs via thalamus Suppression of unwanted movements - inhibitory effects on thalamus and superior colliculus Muscle tone - globus pallidus sends input to reticular formation that reduces muscle tone

Question 58

Explain how the cerebellum contributes to movement

Answer 58

Monitoring intentions for movement - receives input from cortex and basal nuclei regarding planned movements Monitoring actual movement - receives input from propricentors in joints/muscles that reveals what is happening Compares command & sensory signals Sends corrective feedback - if there is a discrepancy it sends signal to UMNs via thalamus

Question 59

What structure is responsible for the circadian rhythm?

Answer 59

Established by the suprachiasmatic nucleus of the hypothalamus

Question 60

How does the reticular activating system (RAS) influence awakening?

Answer 60

When the RAS is activated many impulses are transmitted to widespread areas of the cortex, both directly and via the thalamus increasing cortical activity For arousal to occur RAS must be stimulated which can be from many somatic stimuli - the result of arousal is the state of consciousness Certain senses such as olfactory are hard to activate RAS

Question 61

Define neural plasticity

Answer 61

The capability for change - associated with learning and injury repair

Question 62

# Define the following types of memory: Immediate Short term Long term

Answer 62

Immediate - ability to recall ongoing experineces for a few seconds; provides perspective to the present time that allows us to know where we are and what were doing Short term - temporary ability to recall a few pieces of information for second to minutes Long term - information that is remembered fro days to years that can be retrieved when needed

Question 63

Define memory consolidation

Answer 63

Reinforcement that results from the frequent retrial of a piece of information

Question 64

Define long term potentiation (LTP)

Answer 64

Transmission at some synapses within the hippocampus is enhanced (potentiated) for horus or weeks after a brief period of high-frequency stimulation Glutamate is released that acts of NMDA receptors on postsynaptic neurons

Question 65

Describe the staages of sleep

Answer 65

NREM consists of 4 stages that people go through ~1hr - stage 1: transition between wakefulness and sleep - stage 2: light sleep, the first stage of true sleep, fragments of dreams, eyes roll slowly - stage 3: moderate sleep; body temp and BP decrease - stage 4: deep sleep brain metabolism and body temp decreases; sleep walking REM (usually 3-5 episodes per night) - eyes move rapidly back and forth under closed eyelids - stages gradually lengthen as the night progresses - total REM decreases as a person ages - neuronal activity is high and oxygen use and brain flow is higher than during intensive mental or physical activity - when most dreaming occurs

Question 66

Describe narcolepsy

Answer 66

condition in which REM sleep cannot be inhibited during waking periods and thus involuntary periods of sleep that last ~15 min occur throughout the day - deficiency of orexin which has a role in prompting wakefulness

Question 67

Describe Parkinson's disease

Answer 67

A progressive disorder of the CNS characterized by degeneration of DA in the substania nigra which causes involuntary skeletal muscle contractions

Question 68

Describe cerebral palsy

Answer 68

A motor disorder the results in the loss of muscle control and coordination; caused by damage to the motor areas of the brain during fetal life, birth, or infancy

Question 69

Describe a coma

Answer 69

State of unconsciousness in which a persons responses to stimuli are reduced or absent Caused by brain trauma

Question 70

Describe pain threshold

Answer 70

The smallest intensity of a painful stimulus at which a person perceives pain All individuals have the same pain threshold, however they differ in their pain tolerance