Chapter 16 - Sensory, Motor & Integrative Systems Flashcards
1
Q
Sensation
A
Awareness of body conditions
2
Q
Perception
A
Conscious awareness of sensation
3
Q
Modality
A
Any specific sensory entity
4
Q
4 Components of Sensation
A
- Stimulation
- Transduction
- Conduction
- Integration
5
Q
Stimulation
A
- Events caused by a stimulus
- Stimulus = environmental change which activates sensory neurons
6
Q
Transduction
A
- When a sensory receptor/sensory organ converts one kind of signal/stimulus into another
- Can be caused by a generator potential or a receptor potential
- Can result in either depolarization or hyperpolarization
7
Q
Generator Potential
A
Depolarization of dendrites of 1st order sensory neuron
8
Q
Receptor Potential
A
Graded change in membrane potential due to receptor stimulation
9
Q
Conduction
A
When an action potential (caused by generator/receptor potential) travels towards the CNS
10
Q
Integration
A
When action potentials are translated into sensations in the CNS
11
Q
Sensory Coding
A
When a type of sensation is identified by which fiber carries the incoming message to the CNS
12
Q
Sensory Receptors
A
- Only respond well to one type of stimulus (due to selectivity)
- Receptive field = area monitored by receptor cell
13
Q
Adaptation
A
- Decreased receptor sensitivity caused by constant stimulus
- 2 mechanisms: peripheral adaptation & central adaptation
14
Q
2 Receptor Types Based on Adaptation
A
- Tonic Receptors = Slow adapting; always sending signals to CNS for as long as they’re being stimulated
- Phasic Receptors = Fast adapting; Only activated when their monitored signals change, then quickly adapt
15
Q
2 Receptor Types Based on Complexity
A
- Simple Receptors
2. Complex Receptors
16
Q
Simple Receptors
A
- Associated w/ general senses: temperature, pain, tactile sense & proprioception
- 2 Types: Free nerve endings (sense pain, temperature, & touch) & Encapsulated nerve endings (sense touch & vibration)
- Distributed throughout body
- Cutaneous sensations = Combo of temperature, pain, & tactile sense
17
Q
Complex Receptors
A
- Associated w/ special senses: olfaction, gustation, vision, equilibrium & audition
- All utilize special sensory receptor cells (except olfaction)
- Olfactory receptors = bipolar neurons w/ olfactory hairs
18
Q
3 Receptor Types Based on Location
A
- Exteroceptors
- Interoceptors
- Proprioceptors
19
Q
Exteroceptors
A
Receptors that receive stimuli from outside the body
20
Q
Interoceptors
A
- Receptors that receive stimuli from inside the body (not usually conscious)
- Examples: baroreceptors & chemoreceptors
21
Q
Proprioceptors
A
- Receive info from muscles, tendons, joints & inner ear labyrinth
- Are tonic receptors
- Send brain info on muscle tension, weight discrimination, movements & position of body + body parts
- 3 different types
22
Q
3 Types of Proprioceptors
A
- Muscle Spindles
- Golgi Tendon Organs
- Joint Kinesthetic Receptors
23
Q
Muscle Spindles
A
- Intrafusal fibers wrapped by sensory neuron’s dendrites
- Functions: monitor muscle length, perform stretch reflexes & set muscle tone
24
Q
Golgi Tendon Organs
A
- Protect tendons & muscles from excessive stretch
- Capsule w/ CT fibers wrapped by dendrites of sensory neuron
- Located in tendons
25
Joint Kinsethetic Receptors
Cause joint muscles to relax under excessive stress
26
6 Receptor Types Based on Stimulus
1. Mechanoreceptors
2. Thermoreceptors
3. Nociceptors
4. Photoreceptors
5. Chemoreceptors
6. Osmoreceptors
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Mechanoreceptors
- Respond to physical distortion of their cell membranes
| - 3 subtypes
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3 Subtypes of Mechanoreceptors
1. Tactile Receptors
2. Baroreceptors
3. Proprioceptors
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Tactile Receptors
- Receptors that detect touch, pressure &/or vibration
| - 4 different examples
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5 Examples of Tactile Receptors
1. Hair Root Plexus
2. Meissner's Corpuscle
3. Merkel's Tactile Disc
4. Ruffini's Corpuscle
5. Pacinian Corpuscles
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Hair Root Plexus
- Found around hair follicles
| - Detect movement of hair strands
32
Meissner's Corpuscle
- Located in dermal papillae
- Detects discriminative touch & vibration
- Rapidly-adapting/phasic
33
Merkel's Tactile Disc
- Contact Merkel cells of stratum basale
- Detect discriminative touch & pressure
- Slowly-adapting/tonic
- AKA "Type 1 Cutaneous Mechanoreceptors"
34
Ruffini's Corpuscle
- Found in palms & soles
- Detect heavy touch & pressure
- Slowly-adapting/tonic
- AKA "Type 2 Cutaneous Mechanoreceptors"
35
Pacinian Corpuscles
- Located in various body parts
| - Detect pressure & vibration
36
Itch & Tickle Receptors
- Free nerve endings
| - Function as inflammatory mediators (e.g., histamine & bradykinin)
37
Baroreceptors
- Respond to pressure changes in walls of hollow organs
- Rapidly-adapting/phasic in blood vessels
- Help coordinate reflex activities in visceral organs (e.g., reflex peristalsis in GI Tract)
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Thermoreceptors
- Free nerve endings
- Rapidly-adapting/phasic
- Separate receptors for warm & cold. Cold (10-40 C) in stratum basale; warm (32-48 C) in dermis.
39
Nociceptors
- Respond to painful stimuli
- Damaged tissues release of prostaglandins, kinins &/ or K+ (Non-steroidal Anti-inflammatory Drugs; NSAIDs)
- Located everywhere in the body except the brain
- Slowly-adapting/tonic
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4 Different Types of Pain
1. Fast Pain
2. Slow Pain
3. Somatic Pain
4. Visceral Pain
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Fast Pain
- Carried by myelinated A fibers
- Occurs only in skin
- Generally localized
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Slow Pain
- Carried by unmyelinated C fibers
- Tends to increase in intensity over time
- Occurs typically in deeper tissues
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Somatic Pain
- Found superficially in the skin
| - Also found in skeletal muscles, joints, tendons & fascia
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Visceral Pain
-Pain exclusively found in visceral organs
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Referred Pain
Visceral pain felt in a site other than the place of origin
| *Mechanism: The same spinal cord segment(s) serves place of origin & site where pain referred
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Photoreceptors
- Receptors stimulated by light
| - Examples: rods & cones found in the retinae of eyes
47
Chemoreceptors
- Found in mouth & nose
- Also found in carotid & aortic bodies
- Info goes to respiratory control centers
- Monitor chemical composition of body fluid
48
Osmoreceptors
Monitor solute/solvent ratio of biological fluids
49
Posterior column-Medial lemniscus (PCML) pathway
- Conducts sensory info for tactile sensation (discriminative touch, pressure & vibration) & proprioception
- Origin of sensations include limbs, trunk, neck & posterior head
50
Route of PCML
1. 1st order relay neuron travels along Posterior root ganglion -> Posterior white column (Gracile fasciculus & cuneate fasciculus) -> Medulla (Gracile & cuneate nuclei)
2. 2nd order relay neuron decussates, then ascends via medial lemniscus -> Ventral posterior nucleus
3. 3rd order relay neuron (ventral nucleus) -> Primary somatosensory cortex
* Gracile tract conducts sensory info from lower limbs & trunk to cuneate tract
* Cuneate tract conducts sensory info from upper limbs, trunk, neck & posterior head
51
Anterolateral (AKA "Spinothalamic") Pathways
- Conducts sensory info fro pain, temperature, tickle, itch, crude touch & deep pressure
- Origins of sensation include limbs, trunk, neck & posterior head
52
Route of Spinothalamic Pathway
1. 1st order sensory neuron travels along posterior root ganglion -> Spinal cord (Posterior gray horn)
2. 2nd order relay neuron decussates, then ascends spinal cord in spinothalamic tracts -> Ventral posterior nucleus
3. 3rd order relay neuron (Ventral posterior nucleus) -> Primary somatosensory cortex
53
Trigeminothalamic Pathway
- Conducts sensory info for tactile sensations, pain & temperature
- Origin of sensations include face, oral & nasal cavities & teeth
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Route of Trigeminothalamic Pathway
1. 1st order sensory neuron travels via trigeminal nerve -> cell body in trigeminal ganglion, which projects -> Nuclei of pons/ medulla
2. 2nd order relay neuron from pons/ medulla nuclei decussates, then ascends via trigeminothalamic tract -> Ventral posterior nucleus
3. 3rd order relay neuron from ventral posterior nucleus -> Primary somatosensory cortex
55
Sensory Pathways to the Cerebellum
- Anterior & Posterior Spinocerebellar tracts are responsible for conduction
- Travel to lateral white columns in spinal cord
- Conducts sensory info on unconscious proprioception from muscles, joints & tendons of lower limbs & trunk required by cerebellum
56
Simple & Complex Motor Pathways
- Simple Pathways: Upper Motor Neuron & Lower Motor Neuron
- Complex Pathways: UMNs + interneurons + LMNs
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Upper Motor Nuerons (UMNs)
- UMNs arising from motor cortex initiate voluntary skeletal muscle activity
- UMNs arising from red nucleus, vestibular nucleus, superior colliculus/ reticular formation control muscle tone, posture & balance
- Receives inputs from basal nuclei & cerebellum
- Most UMNs synapse indirectly w/ LMNs via local circuit nuerons
58
Lower Motor Neorons (LMNs)
- LMNs arising from brainstem extend axons via cranial nerves to skeletal muscles of face & head
- LMNs arising from spinal cord extend axons via a spinal nerve to skeletal muscles of limbs & trunk
59
Spastic Paralysis
- Occurs due to UMN injury
| - Symptoms include exaggerated reflexes & increased muscle tone
60
Flaccid Paralysis
- Occurs due to LMN injury
| - Symptoms include absent reflexes & decreased/absent muscle tone
61
Pyramidal Cells
UMNs of motor cortex
62
3 Parts of the Motor Cortex
1. Primary Motor Cortex
2. Premotor Cortex (Includes premotor area, Broca's motor speech area & frontal eyefield area)
3. Supplementary Motor Area (Found midline atnerior to precentral gyrus; involved in planning & coordination)
*Pyramidal cell axons form tracts that project to nuclei of brainstem & spinal cord where they synapse w/ LMNs, either directly/ via local circuit neurons
63
Function of the Motor Cortex
To regulate muscle tone & coordinate skilled movements
64
2 Types of Direct (AKA "Pyramidal") Motor Pathways
1. Corticobulbar Pathway
| 2. Corticospinal Pathway
65
Corticbulbar Pathway
- Location of UMNs: Motor Cortex (Pyramidal Cells)
- Destination: Motor nuclei of cranial nerves 3-7 & 9-12 in the brainstem
- Site of cross-over: Brainstem
- Actions: Voluntary control over skeletal muscles of eye, jaw, tongue, face, pharynx & some neck muscles
66
Corticospinal Pathway (Lateral & Anterior)
- Location of UMNs: Motor Cortex (Pyramidal Cells)
- Destination: Anterior gray horns of spinal cord
- Site of decussation: Inferior end of medulla (forms LATERAL corticospinal tracts) OR passing through the medulla (forms ANTERIOR corticospinal tracts; crosses over via anterior white commissure)
- Actions: Voluntary control over skeletal muscles of contra-lateral limbs & trunk (Lateral -> Controls distal limb parts; Anterior -> Controls trunk & proximal limb parts)
67
Indirect (AKA "Extrapyramidal") Motor Pathways
- Axons of UMNs w/ cell bodies in brainstem nuclei
| - Location: Anterior & lateral white columns
68
4 Types of Indirect (AKA "Extrapyramidal") Motor Pathways
1. Rubrospinal Tracts
2. Tectospinal Tracts
3. Vestibulospinal Tracts
4. Lateral & Medial Reticulospinal Tracts
69
Rubrospinal Tracts
- Location of UMNs cell bodies: Red nucleus
- Destination of UMN axons: Anterior gray horns of spinal cord
- Site of decussation: Brainstem
- Actions: Voluntary movements of distal upper limb muscles
70
Tectospinal Tracts
- Location of UMNs cell bodies: Superior colliculus
- Destination: Anterior gray horns of cervical spinal cord
- Site of decussation: Brainstem
- Actions: Involuntary regulation of contralateral skeletal muscle activity (Moves eyes, head neck + trunk in response to visual & auditory stimuli)
71
Vestibulospinal Tracts
- Location of UMNs cell bodies: Vestibular nuclei of pons & medulla
- Destination: Anterior gray horns of spinal cord
- Site of decussation: None
- Actions: Involuntary control of ipsilateral trunk & proximal limb skeletal muscles (Balance + posture in response to head movements)
72
Lateral & Medial Reticulospinal Tracts
- Location of UMNs cell bodies: Reticular formation
- Destination: Anterior gray horns of spinal cord
- Site of decussation: None
- Actions: Involuntary control of ipsilateral trunk & proximal limb skeletal muscles (Responsible for posture + muscle tone in response to ongoing movement)
73
2 Integrative Functions of the Cerebrum
1. Sleep
| 2. Learning + Memory
74
Sleep
- Arousable state of partial unconsciousness
- Functions to maintain mental health, memory & learing
- Dominated by the parasympathetic division of the ANS
75
Mechanism of Sleep
- Blockade of ACh-releasing neurons of the Reticular Activating System
- May be caused by adenosine binding to A1 receptors
- Methylxanthines (Caffeine & thephylline) prevent adenosine binding to A1 receptors
- RAS blockade also by melatonin
76
2 Components of Sleep
1. Non-Rapid Eye Movement (NREM) Sleep
| 2. Rapid Eye Movement (REM) Sleep
77
NREM Sleep
- Stage 1: Transition between wakefulness & sleep (Possible hypnagogic hallucinations
- Stage 2: Light sleep
- Stage 3: Moderately deep sleep, growth hormone released (+Delta waves emitted)
- Stage 4: Deep sleep; growth hormone released; body repairs; possible sleepwalking, night-terrors
78
3 Parts that Control NREM Sleep
1. Pre-optic Area
2. Basal forebrain
3. Medulla
79
REM Sleep
- Occurs about every 90 mins.
- 3 to 5 times/night
- REM sleep duration lengthens w/ each cycle
- Dreaming also occurs
- Eyeballs move rapidly back & forth w/ eyelids closed
- High brain blood flow & O2 yse
- Function: To help w/ brain development
80
Typical Sleep Cycle
NREM1 -> NREM2 -> NREM3 -> NREM4 -> NREM3 -> NREM2 -> REM -> NREM1 -> Wake or repeat
81
Learning
Acquisition of new information, behaviors, or skills
82
Memory
Ability to store, retain & retreive learned info
83
4 Brain Parts Contributing to Memory
1. Frontal, parietal, temporal + occipital lobes
2. Limbic system
- A. Hippocampus stores spatial + explicit memory
- B. Amygdala stores emotional memory
3. Cerebellum & basal nuclei store procedural + implicit memory
4. Anterior & Medial thalamic nuclei
84
3 Types of Memory
1. Immediate (AKA "Sensory") Memory
2. Short-term Memory
3. Long-term Memory
85
Immediate (AKA "Sensory") Memory
- Very short-term retention of sensory input received by brain
- Electro-chemical events occurring in the hippocampus, mammillary bodies, and thalamic nuclei
86
Short-term Memory
- Info retained for a few minutes
- Limited capacity
- Electro-chemical events occurring in the hippocampus, mammillary bodies, and thalamic nuclei
- Converted to long-term memories by reinforcement
87
Long-term Memory
- More permanent memory
- Frequent memory retrieval will reinforce it ("Memory consolidation")
- If memory not consolidated, eventually lost
- Newly-formed long-term memory lost following general anaesthesia, brain hypoxia, and ECT
88
Mechanism of Long-term Memory
- Structural/functional changes occur in neural circuitry due to plasticity of the brain
- Changes include increased:
1. Protein synthesis
2. No. of Pre-synap. terminals
3. Size of synaptic end bulbs
4. Quantity of neurotransmitter stored
5. No. of dendritic branches + "spines"
6. No. of synaptic connections
89
Calpain
Proteolytic enzyme; degrades spines of dendrites, thus, leading to memory loss
90
Long-term Potentiation (LTP)
- Persistent enhancement of neural transmission caused by high-frequency stimulation of chemical synapses in hippocampus
- Glutamate causes N.O. release from post-synaptic neuron
- N.O. diffuses into pre-synap. neuron -> circuitry changes
- LTP important for learning & memory
