Chapter 16 Flashcards
How to understand spinal nerves?
First part of pathway name tells you where it starts
If it ends at spinal cord and begins at cortex it MUST be motor bc it’s descending
Sensation
Awareness of an internal or external stimulus
Perception
Conscience awareness and interpretation of stimulus (involving the cortex
Visceral
Internal
- Sensory Modality
- Every single stimulus (touch, pressure, vibration, pain)is a unique sensory modality, carried on a unique nerve and will go to a specific location on the posterior cortex
Categories of sensory modality
- General senses (somatic and visceral)
Special senses
Special senses
Taste, smell, sight, hearing, equillibrium
Process of sensation
Same for every modality
- Stimulation of sensory receptor (very specific stimulation for specific receptor)
- Transduction of stimulus – (mech. stim. into electric graded potential)
3.Generation of impulse (if GP strong enough)
- Transduction of stimulus – (mech. stim. into electric graded potential)
- Integration of sensory input in CNS (awareness/interpretaiton of stimulus)
Receptor Feel
Every receptor is only sensitive in very particular receptor area
How are sensroy receptors clssified?
- Location of receptor (internal, external or visceral)
- Type of stimulus detected (see below 1-6)
- Type of receptor (structure)
- Exteroceptors
Receptors near or at surface
- Interoceptors (visceroceptors)
Receptors deep in the body
Proprioreceptors
Within muscles tendons or joints
Types of stimuli detected by receptors
- Mechanoreceptors – bending, stretching = mechanical stimulus
- Thermoreceptors
- Nociceptors (pain receptor)
- Photoreceptors (light receptor)
- Chemoreceptors – taste, smell, fluids (recepotrs in blood, moniter pH, blood chem.)
- Osmoreceptors
(measure osmotic pressure in different chambers of body
Type of receptors (by structurs
Free nerve ending of first order neuron - dendrite sticks into tissue or fluid
- Encapsulated nerve ending of first order neurons – pressure, vibration
- Dendrite that is encapsulated in connective tissue (Graded or generator potential)
eparate cells that synapse with first order neuron (eg. Hair cells fir hearing and equilibrium, taste, sight – produce RP_
Sensory receptor adaptation
- Receptor potential and generator potential decreases in amplitude during a constant stimulus resulting in decreased AP’s in sensory neuron, leads to decrease perception
- Receptor gets bored
- Less and less first order response
Fast: vibration, touch and smell
How long does sensory recepotr adaptation take to occur
45 s -1 min
How do somatic sensations occur?
receptors embedded in skin, subcutaneous layer, mucous membranes, muscles, tendons, joints and inner ea
- Punctuate distribution
- Sensory receptors in body are in different conc. In different locations resulting in differeing levels of sensitiivity across body
cutaneous sensations – arise from skin
4 Modalities of somatic sensations
- Tactile (touch, pressure, vibration, itch, tickle)
- Thermal –Temperature (hot, cold)
- Pain (nociceptors)
- Proprioceptive (spindles, tendosn organs, joint receptors)
Phantom limb sensation
- A person is aware or senses that pain is coming from a portion of body that is no longer there
Describe thermal sensation temperatures
Fast sensation
- Cold
10-40° C (50-105° F)
Stratum basale - Warm
32-48°C (90-118°F)
Dermis
< 10°C & >48°C = pain no temperature sensation
Cold and warm different sensations carried on different nerves.
Only place nociceptors NOT located on?
Brain
Process of feeling pain
Tissue damage or irritation (chemical, hot water, etc.) → chemical releases kinins, prostaglandins (type of kinin) → stimulate nociceptors (pain receptor)
Types of pain
- Fast – “stab” very localized
- Slow – “ache”
- Superficial Somatic Pain
- Deep Somatic Pain – Skeletal muscles, tendons, joints & fascia
- Visceral – “deep” (internal)
- Referred Pain – visceral pain (Heart attack)
- Analgesics
- Over the counter tablets
- Block the formation of prostaglandins
20 minutes for pain to go away bc it initially it does not allow the formation of prostaglandins.
Pain management
- Anesthetics (eg. Novocaine)
Analgesics - Opiates (eg. Morphine and oxine ) - tells brain i’s no longer a painful stimulus
- Acupuncture
Derivative of marijuana
Icing
muscle spindle
- Monitors rate of stretch (how fast/slow and steady) and amount of stretch (too much for that joint?)
Normally in a capsule - Receptor buried within muscle fibers
- As fibers in muscle stretch so too do fibers in spindle
- Sends info to cerebrum
- If over stretched it sends signal to contract
Muscle fibers
- Muscle fibers INSIDE spindle
- 3-10 muscle fibers inside spindle
- Same fibers, actin and mission
- Central portion wrapped in nerves but NO actin and myosin
- Ends of spindle HAVE actin and myosin
Intrafusal
Extrafusal neuron goes to muscle fibers (outside spindle) have capacity for contraction
Most muscles have at least a couple muscle spindles
Gamma motor neurons
Motor neurons contained within muscle spindles
- Adjust the tension in muscle spindle
-Terminate near both ends of intrafusal fiber
What surrounds muscle fibres?
Extrafusal muscle fibres
- Supplied by Alpha motor neurons
(Golgi) Tendon Organs
Sensory structure
Nerves distributed throught tendon
GTO moniters how much force is being produced
- If force is too great, tendon organ causes relaxation of muscle (opposite of stretch reflex)
- Athletes have high tolerance
c) Joint Kinesthetic Receptors
In/around synovial joints
- A group/cluster
- Several different types of receptors inside/around synovial joints
- Monitor acceleration/deceleration.
- Monitor pressure inside synovial joint
Somatic Sensory Pathways
relay information from somatic sensory receptors to primary somatosensory cortex to cerebellum
Commonly 3 neurons in sequence
1st order (Neuron): From receptor to CNS
2nd Order: CNS to thalamus
3rd Order: THalamus to specific somatosensory area
Where is the somatosensory area
Just behind central sulcus
Posterior column-medial lemniscus pathway
From spinal cord to brain stem – touch, pressure, vibration and proprioception from limbs, trunk, neck and posterior head
Two divisions of posterior column (pathways)
o Gracile fasciculus
o Cuneate fasciculus
Anterolatera
Spinothalmac
impulses for pain, temp, itch and tickle from limbs, trunk, neck and posterior head
Trigeminothalamc Pathway
tactile, thermal and pain from the face, nasal cavity, oral cavity and teeth
How does the amount of space in the cortex correlate with the muscles affect?
The greater fine motor control required, the greater amount of space required on cortex
Sensory homunculus
Distorted sensory map of the body
Any sensory pathway that travels to the cerebellum implies …
Some element of motor control
Two major tracts in spinal cord assisting in balance, posture and skliled movement?
Posterior spinocerebellar tract
Anterior spinocerebellar tract
What is the significance of the LMN in a somatic motor pathway?
All info converges here - last stop before AP goes out to muscle
Facts abt somatic motor pathways
All converge in LMN
All have cell bodies in CNS
Extend out of CNS to control skeltal muscles
All end up at final common pathway
Four distinct pathways that supply LMN
Local circuit neurons’
UMN
Basal nuclei neurons
cerebellar neurons
Local circuit neurons’
- Neural motor pathway
Circuits in a very small, localized area of spinal cord - Typically involve interneurons.
Upper Motor Neuron
- Somatic motor pathway that ends in LMN
Cell bodies in upper CNS - Decide on final action
Basal Nuclei neurons
Converge in LMN
- Connect brain stem to cortex to cerebellum
- Help initiate and terminate movement
Cerebellar neurons
- Neural motor pathway
Leaving from cerebellum, connect to brain stem get info from cortex - Eventually also send info to the common pathway
What does syphilis do?
attack cell bodies of UMN pathways
Flaccid paralysis
no voluntary or reflexive control
- Muscle is loose and elastic
- If LMN damage
Spastic Paralysis
– increase muscle tone, reflexes exaggerated (eg..Babinski)
- Typically when damage to UMN (primarily cortex)
sensory homunculus
The distorted somatic
sensory map of the body
Lateral corticospinal tract controls
distal muscles of limbs: precise movements of hands and feet (eg. Play piano)
- Limbs and trunk
- Anterior corticospinal
muscles of trunk and proximal limbs
Corticobulbar tract
muscles of head (face, chewing, swallowing)
Amyotrophic lateral sclerosis
motor area of cortex is attacked and UMN’s and LMN’s
- Corticalspinal track Aren’t sending info to LMN (also can have LMN problems)
- No cognitive detrement
Role of: Vestibular nuclei , Reticular Formation, Superior Colliculus, Red Nucleus
Parts of brainstem, All of them are very significant for Involuntary motor control correct movement correct sequence.
Indirect motor pathways
- Typically begin at brainstem
- Terminate in LMN
- Regulate involuntary actions (Postuter, muscel tone)
- Impulses follow complex, polysynaptic routes that include motor cortex, basal ganglia, thalamus, cerebellum, reticular formation and brain stem nuclei.
- Regulate involuntary actions: balance, posture, muscle tone, reflexes
5 Major tracts of the spinal cord
Rubrospinal tract, tectospinal tract
Vestibulospinal tract
Medial and lateral spinal tracts
Role of basal nuclei (with cerebellum) in movement
- Initiate and terminate movements –caudate and putamen
- Suppression of unwanted movement
- Maintain Muscle tone (For blood vessels)
- Cortical function influence (non- motor processes)
- Basal nuclei influence UMN for things like cognition & limbic system
Disorders of the basal nuclei
- Parkinson Disease
- Progressive CNS particular midbrain (substantinaigra)
- Not enough dopamine released
- Huntington Disease
- Genetic
- Problem with NT
- No control of unwanted movements
- 30-40 years (10-20 years of age)
- Tourette Syndrome
- Imbalance of NTs
- Inappropriate outbursts/muscle tics
- Schizophrenia/Obsessive-Compulsive Disorder (OCD)
- Problem associated with basal nuclei (could be serotonin uptake)
Cerebellum in movement
Posture, balance, movement, learning new skills
Monitor intended movements (red)
- Monitor actual movements.
- Compare intended with actual (movement)
4 Send out corrective feedback.
- Ideally next time movement is attempted feedback allows for more efficient are effective technique takes place.
Cerebrum Integrative Functions
- Circadian Rhythm (sleep and awake pattern)
- Cortex (reticular formation and RAS) drives and controls awake sleep cycle
Name the stages of sleep
1NREM: Transition from awake to sleep (not technichally asleep) - eyes closed + relaxed
2NREM: Light sleep (7-20 minutes)
3NREM: Around 20 minutes
- Moderate sleep
- BP, temp, and metabolic rate drops
4REM: Deep sleep (predominant for sleep walking)
- metabolic rate lowest
REM phase occurs every 90 minures
Cycles occur every few hours
How often does REM phase occur
Every 90 minutes
What is a REM phase
Deepest phase of sleep
- Most dreaming occurs herer
- Newborns have more REM sleep
- Adults have less
Narcolepsy is a problem with
- Individual falls asleep any time during day
- Remain asleep for 15 minutes or so
- Problem with neuropeptides and hypothalamus
Sleep apnea
- Stops breathing 10-20 seconds then starts again during sleep
- Deprives constant blood and O2 flow
- Dementia could be more likely
What is associative memory
- Linking two events together
- Bell ringing dog salivates
What is non associative memory
- Repeated exposure to same stimulus (repetition)
o Habituation: Repeated exposure to irrelevant stimulus (eventually learn to ignore it)
o Sensitization: Repeated exposure to noxious stimulus, over time u increase response (Avoiding pain or discomfort)
What is a declarative memory
Memory of event that has been spoken out or written down (association area of cortex for conscious recall)
What is a procedural memory
Learning and now memorizing (motor skills)
Premotor area, cerebellum, basal nuclei
To be successful the info must be the correct information
Immediate memory (know the present state)
- Short term
What is short term memory
- Seconds or minutes
- Dementia: Forgetting why they went into a room
Long term memory
Info that’s been introduced is accessible for weeks, months, years
- Learned through repeition
- Recall ability increased by highlighting, study, colour
Describe route of CSF
Choroid plexus in lat V
Interventricular foramina
3rd V
Aqueduct of Midbrain
4th V
Three openings in roof
Subarachnoid space
Central canal
Rest of space around CSF
Reabsorbed by arachnoid villas
medulla
Voluntary movement of limbs and trunk
Cardiac and respiratory centers
vomiting, swallowing, sneezing, coughing, and hiccupping reflexes
Instruct cerebellum in skill learning
Pons
efficiency and coordination of voluntary motor neurons
controlling breathing, chewing, eye movement, taste and salivation, facial movement, and balance and equilibrium
Midbrain
Eye tracking and scanning
Movement of eys, head and trunk in response to visual stimuli and auditory stimuli
cerebellum
Smoothing out skeletal muscle contractions and directing complex muscle movements
subconscious parts of skeletal muscle movements and contributes to equilibrium and balance
Thalamus
relays most sensory input to the cerebrum and transmits info from the cerebellum to the primary motor cortex to aid in motor functions
Keeps person conscious
Hypothalamus
control ANS activities, it produces and inhibits hormones and regulates emotional and behavioural patterns alongside the limbic system. This organ of the brain regulates eating and drinking, circadian rhythms, and acts as the thermostat for the body
Where do all second-order sensory neurons go first?
Thalamus
First-order neurons are always
Sensory neurons
Where is a second-order sense neuron synapse
Posterior grey horn
