CNS Motor Flashcards
What is consciousness?
The level of arousal (awake, sleep)
What are the 2 ways of measuring consciousness?
With behaviour and brain activity
What is conscious experience?
Thoughts, feelings, desires, ideas, etc
Brain activity to determine consciousness is measured using […]
EEG
What does the EEG measure specifically?
The neuronal activities of neurons located near the scalp in the grey matter of the cortex
In an EEG, frequency is related to […] and amplitude is related to […]
Levels of responsiveness (state of concsiousness)
Synchronous neural activity
How can you tell when a seizure is occurring from an EEG?
The activity is VERY synchronized (Big amplitude)
How will an EEG differ between when an individual is relaxed and when an individual is alert?
When relaxed, an EEG will have slow frequencies and higher amplitudes Whereas an alert individual will have fast frequencies and lower amplitudes
When an individual is awake, their EEGs have a […] amplitude and a […] frequency.
low
fast
When an individual is relaxed with their eyes closed, the EEG pattern produced is called […]
Alpha rythm
When an individual is alert, the EEG pattern produced is called […]
Beta rythm
Describe how EEGs change as you go through different stages of sleep.
You start with an awake state (low amplitudes, high frequencies) and slowly, the amplitudes get higher and the frequencies slower. Until you reach the REM which is equivelant to being awake
Describe the sequence of a sleep cycle.
Stages: 1 -> 2 -> 3 -> 4 -> 3 -> 2 -> 1 -> REM -> 1…
In REM sleep, name 4 physiological differences from the rest of the sleep cycles.
- Increased eye movement
- Increased inhibition of skeletal muscles
- Increased heart rate
- increased respiration
What is sleep apnea? Describe its cause.
when there is a sudden reduction of respiration during sleep. often cause by relaxed skeletal muscles of the tongue that block the airways
What are the 3 major regions of the brain responsible for circadian rhythm?
Hypothalamus (preoptic area and Suprachiasmic nucleus)
Reticular activationg system
When you are awake, […] neurons are active.
Aminergic
When you are asleep, […] neurons are active.
Cholinergic
When you’re awake, describe the activity of the reticular activating system and the hypothalamus.
- There is a release of Neurotransmitters (norepinephrine and serotonin) by the reticular activation system which decreases acetylcholine
- There is less GABA so more histamine is released which activates the thalamus and cortex by the Hypothalamus
When you’re asleep, describe the activity of the reticular activating system and the hypothalamus.
- There is an increase in GABA release by the hypothalamus which reduces histamine release and decreases thalamus and cortex activity
- There is less norepinephrine and serotonin released by the reticular activating system which increases acetylcholine
What is motivation?
it produces goal directed behaviours
The motivational pathway is called the […]
Mesolimbic dopamine pathway
What is the major neurotransmitter involved in motivation?
Dopamine
How do drugs take advantage of the mesolimbic dopamine pathway?
They activate the pathway and make the behaviour enjoyable
Describe the major components of the mesolimbic dopamine pathway.
Dopamine goes in the locus ceruleus in the reticular activating system. It activates the midbrain and then the prefrontal cortex
What is the amygdala responsible for?
It modulates emotional response
What is the hippocampus responsible for?
Memory
Give two examples of altered states of consciousness.
Schizophrenia and mood disorders (depression, bipolar disoder)
What are the two types of memories? Explain the difference between them.
Declarative: conscious experience that can be put into words
Procedural: Skilled behaviour
What is consolidation?
The movement of information from short-term memory to long-term memory
When does consolidation occur?
During sleep
What parts of the brain are involved in short-term vs long-term declarative memory?
Short: Hippocampus and temporal lobe
Long: Associated cortex
What parts of the brain are involved in short term vs long term procedural memory?
Short: Widely distributed
long: Basal nuclei, cerebellum, premotor cortex
Where are the brain structures involved in language mainly located?
Usually in the left hemisphere, in the frontal cortex (Broca’s area) and the temporal lobe (Wernicke’s area)
What are the two regions of the brain involved in language? State their function.
Broca: articulation
Wernicke: comprehension
Someone with a language deficit has […]
Aphasia
What is the cause of sensory neglect? How does it manifest?
Usually a stroke in the parietal lobe. People don’t comprehend that the contralateral side (damaged side) exists
What are the two types of motor behaviour?
Volontary and reflexive
What is the difference between extension and flexion?
Increase the angle of the joint for flexion and decrease the angle of the joint for extension
During extension, how do the flexor and extensor muscles behave?
Extensor: contracts –> agonist
Flexor: relaxes –> antagonist
During flexion, how do the extensor and flexor muscles behave?
Extensor: relaxes –> Antagonist
Flexor: contracts –> agonist
Are motor neurons excitatory or inhibitory?
Excitatory
The neurotransmitter released by motor neurons is […]
Acetylcholine
What are the two types of motor neurons? What part of the muscle do they innervate?
Alpha: Skeletal (extrafusal) muscle
Gamma: Muscle spindles (infrafusal
Where are the cell bodies of motor neurons found?
In the ventral horn of the spinal cord or the brain stem (cranial nerves)
Describe the relationship between the spinal afferent pathways and the motor efferent pathways.
When a sensory afferent neuron makes its way the spinal cord, it splits in two:
1. It goes to the dorsal column to reach the brain
2. It activates an interneuron that will then activate a motor efferent
NOTE: the interneuron will also receive input from descending motor commands
Name the 4 types of input that interneurons respond to/are involved in.
- Proprioceptive feedback
- Pain
- Voluntary movements from descending pathways
- Coordinates complex movements with info from other spinal levels
Name 2 types of monitoring done by the spinal interneurons.
- Tension monitoring
- Length monitoring
What are the 3 types of spinal reflexes?
withdrawal reflex
stretch reflex
Inverse stretch reflex
What is the function of the withdrawal reflex?
Protects limbs from injury
What is the function of the stretch reflex?
Controls muscle length
What is the function of the inverse stretch reflex?
Controls muscle tension
Do reflexes respond quickly or slowly? Why?
Fast. The information stay in the spinal cord and doesn’t require any input from the brain
Describe the pathway of the flexion withdrawal reflex on the ipsilateral side.
If there is pain in the foot, the sensory neurons will activate
1. the extensor’s interneuron –>inhibits the ipsilateral neuron extensor
2. the flexor’s interneuron –> excites the ipsilateral flexor
3. the anterolateral afferent –> information to the brain for processing
Describe the pathway of the flexion withdrawal reflex on the contralateral side.
In addition to ipsilateral activation, a contralateral interneuron will be activated which will then
1. Activate the contralateral extensor
2. Inhib the contralateral flexor
What is irradiation?
Increase on rate and magnitude of withdrawal response with incrtease stimulus strength because more neurons are recruited
What determines the length of the afterdischarge period?
The positive feedback loops
What is the cause of afterdischarge?
The feedback loops in the spinal cord determine the time the response if going to be maintained
Is the withdrawal reflex monosynaptic or polysynaptic?
it is polysynaptic meaning that interneurons are between the afferent and the efferent to transfer the sensory input into motor output
The knee jerk is an example of which reflex?
The strech reflex
Name the 3 steps of the monosynaptic and polysynaptic stretch reflex at the knee.
- The extensor muscle of the thigh is stretched
- The stretch receptors are activated
3.1. Excitation of the motor neurons innervating the ipsilateral extensor (M)
3.2. Inhibition of motor neurons innervating the ipsilateral flexor (P)
3.3. Afferent goes up the dorsal column
What part of the monosynaptic stretch reflex produces a kick in the case of the knee jerk reflex?
the excitation of the ipsilateral extensor
Is the stretch reflex monosynaptic or polysynaptic? Explain.
Both: the excitation of the extensor neurons is monosynaptic while the inhibition of the flexor neurons is polysynaptic
What is the Golgi tendon organ and where is it found?
It response to tension in the tendon of a muscle
The Golgi tendon organ is [in parallel/in series] with muscle fibers.
series
What are the two types of muscle fibers and where are they located?
Intrafusal: in the muscle spindles
Extrafusal: Muscle
Extrafusal muscle fibers are activated by […] and intrafusal muscle fibers are activated by […]
Alpha motor neurons
Gamma motor neurons
Muscle spindles are [in parallel/in series] with muscle fibers.
Parallel
What are stretch receptors and where are they located?
Stretch receptors are in the muscle spindle
What types of afferents surround muscle spindles?
Ia primary and II secondary
Describe how Ia and II afferents respond to a linear stretch.
Since Ia are adapting neurons, they will have more frequent action potentials during a linear stretch
Since II are not adapting, they will only detect a change in stretch once the muscle is more stretched
Describe how Ia and II afferents respond to a tap/stretch reflex.
Ia have more frequent action potentials
II don’t have any change since the stretch is too fast to be detected
II afferents signal […]
static muscle length
Ia afferents signal […]
Dynamic muscle length
During extension, muscles are lengthened, and there is an [increase/decrease] in […] afferent activity.
increase
muscle spindle afferent activity
During extension, are alpha or gamma neurons active (or both)?
Alpha
During flexion, muscles are shortened, and there is an [increase/decrease] in […]
decrease
muscle afferent activity
During voluntary flexion, are alpha or gamma neurons active (or both)? Why?
Both
When the muscle shortens, the extrafusal receptors (alpha) are too relaxed to detect change. To avoid this, the intrafusal fibers contract so the spindles stay sensitive. In this moment, Gamma afferents are activated
During voluntary flexion, the neuronal activity is referred to as the phenomenon […]
alpha-gamma coactication
What is the function of gamma neurons?
they aim to maintain the sensitivity of the stretch receptor in the muscle spindle when muscle fibers shorten during contraction.
Is the stretch reflex considered monosynaptic or polysynaptic?
It is considered to have both mono- and polysynaptic components. The primary afferent part is considered monosynaptic, while the secondary afferent part is considered polysynaptic.
Muscle spindles report […]. What is their purpose in the strech reflex?
muscle length
Feedback the muscle length for the reflex
Do muscle spindles contribute to the force of muscle contraction?
No
What is the purpose of the stretch reflex.
resist changes in muscle length
What is the purpose of the inverse stretch reflex?
Control muscle tension
What organ primarily responds to muscle tension?
The Golgi apparatus.
Is the Golgi tendon more active when the muscle stretches or contracts? Why?
It will send more action potentials for both, but will be more active during muscle contraction, as this is when tension is the highest. It will send fewer action potentials during stretching.
Describe the structure of the Golgi tendon orgon.
It connects the tendons to the muscle fibers. It consists of collagen fibers wrapped around free nerve endings, all wrapped in a capsule. The nerve endings form 1b afferents.
How does transduction take place in the golgi tendon?
When a muscle contracts and pulls the golgi tendon, this causes the collagen fibers to mechanically deform the nerve endings of the 1b afferents, mechanically opening ion channels.
Describe the 4 steps of the inverse stretch reflex (Golgi tendon organ reflex).
- Increased tension in extensor muscle due to contraction
- Activation of Golgi tendon organ
- Increased afferent activity from Golgi organ tendon
4.1. Inhibition of motor neurons innervating the ipsilateral extensor.
4.2. Excitation of motor neurons innvervating the ipsilateral flexor.
The inverse stretch reflex contains a […] feedback. Explain how.
Negative. This is because when the muscle contracts and activates the Golgi tendon, this causes an inhibition of the same extensor, stopping it from generating force
The Golgi tendon organ has what kind of afferents?
Ib
Is the inverse stretch reflex considered monosynaptic or polysynaptic?
Polysynaptic
The pathways involved in motor control are [ascending/descending]
descending
What are the two motor control pathways? What do they control?
Corticospinal: skilled movements
Extrapyramidal: trunk and posture
What are the 3 levels of the motor control hierarchy? Describe the major components of each.
Highest level: higher centers
Middle level: sensorimotor cortex, basal nuclei, thalamus, brainstem, cerebellum
Local level: brainstem and spinal cord
What are the two major functions of the middle level in motor control?
- Executes the individual muscle contractions
- Makes corrections based on sensory information.
The corticospinal pathway goes from the […] to the […]
Sensorimotor cortex to the brain stem and spinal cord
The extrapyramidal pathway goes from the […] to the […]
Brainstem to the brainstem and spinal cord
Name the major parts of the brain involved in voluntary control of movement and the order in which they get activated.
- There’s a conscious initiation of the movement in the prefrontal lobe
- The premotor cortex organises the movement
- The primary motor cortex initiates the movement
(4). somatosensory interests with the motor cortex to adjust (proprioception)
Where are the primary motor cortex and the somatosensory (primary sensory) cortex relative to one another?
They are right next to one another. The Primary motor cortex is infront of the central gyrus whereas the primary sensory sortex is behind the central gyrus
What parts of the body take up more space in the primary motor cortex? What does this imply about them?
The hands and the mouth meaning that those two parts have highly acute movements (more skills and more neuron recruited for a movement)
The size of body structures in the primary motor cortex is proportional to […]
- the number of neurons dedicated to their motor control
- the degree of skill required to operate that area of the body
Describe the corticospinal pathway.
It starts at the motor cortex, goes down the ipsilateral side to the medulla to cross to the contralateral side and then the axon directly synapses with the alpha and gamma motor neurons of skeletal muscles
Is the corticospinal pathway ipsilateral or contralateral?
contralateral to the part it controls
What parts of the body does the corticospinal pathway control?
predominantly extremities (hands and feet)
What kinds of movements does the corticospinal pathway control?
Skilled voluntary movements
What types of neurons are involved in the corticospinal pathway?
Compact and discrete fibers direct to the spinal cord
Describe the extrapyramidal pathway.
It originates in the brainstem and goes down to innervate different interneurons
What parts of the body does the extrapyramidal pathway control?
The trunk and postural muscles
What types of movements does the extrapyramidal pathway control?
Upright posture, balance and walking
What is muscle tone?
the amount of tension in a muscle
Muscle tone in normal individuals can be described as […]
slight and uniform across the body
How does damage to descending pathways affect muscle tone?
It can cause hypertonia, spasticity and rigidity below the lesion because of less inhibition from the descending pathways
What are the symptoms of hypertonia?
Abnormally high muscle tone
How does damage to motor neurons affect muscle tone?
it can cause hypotonia, atrophy and decreased/ missing reflexes
What are the symptoms of hypotonia?
Abnormally low muscle tone
What is the function of the basal nuclei in motor control?
They help to determine the specific sequence of movements needed to accomplish a desired action
Give 2 examples of disorders related to the basal nuclei.
Parkinson disease
Huntington disease
What is the cause of Parkinson disease?
Reduced dopamine input to the basal nuclei
What are the 4 symptoms of Parkinson’s disease?
Akinesia: reduced movement
Bradykinesia: slow movement
Muscular rigidity
Resting tremor
How is Parkinson’s disease treated?
increasing dopamine concentrations in the brain
What is the cause of Huntington’s disease?
a genetic mutation that causes widespread loss of neurons in the brain (more often in the basal nuclei)
What are the two symptoms of Huntington’s disease?
What is it
Hyperkinetic disorder: excessive motor movements
Choreiform movements: jerky, random involuntary movements of the limbs and face
What is the role of the cerebellum in motor control?
Movement timing, planning and error correction as well as learning new skills
How does the cerebellum regulate movement?
They receive sensory information from: the vestibular, visual, auditory, somatosensory and proprioception cortexes and coordinate everything
Name the 5 symptoms of cerebellar deficits.
Asynergia: smooth movements are subdivided into separate components
Dynmetria: Unable to target movements correctly past pointing
Ataxia: Incoordination of muscle groups (awkward gait)
Intention tremor: during voluntary movements
** There is no paralysis or weakness
