- Frontal Lobes
- What is it?
- Home to personality?
- Lesions: wide variety symptoms
- More than any part of brain
- Involved in:
- motor function
- problem solving
- spontaneity
- memory
- language
- initiation
- Extremely vulnerable to injury
- Large in size
- Located up front
- Most common brain injury
- Mild to moderate trauma
- 1. Primary Motor Cortex
- M1
- Pre-central gyrus
- Directs motor coordination
- Voluntary movement
- Input
- Pre-Motor area
- Plan and execute movements
- Posterior Parietal Cortex
- Visual information
- Supplementary Motor Area
- planning & coordinating complex movements
- (requiring two hands)
- Cerebellum
- Balance
- Output
- contains Betz cells
- large neurons
- long axons down spinal cord
- synapse directly to motor neurons of muscles
- Sends info to
- Cranial nerves
- Lower motor neurons
- Functions
- Elicits movements
- Not directly connected to muscles
- Axons go to brainstem & spine
- Central pattern generators control actual muscle move
- Homunculus
- Organized by body region
- Top-down
- Toes
- Knee
- Hip
- Trunk
- Stomach
- Arm
- Elbow
- Wrist
- Hand
- Fingers
- Thumb
- Organized by body region
- Important for complex actions
- Writing
- Less important for coughing, sneezing, laughing, or crying
- 2 major actions
- Elicit complex movement patterns
- Also $ when imagine movement
- Note:
- Causes movements, doesn’t plan them
- Movement needs Muscles
- M1
- *********************
- Muscles
- 1. Smooth muscles
- Digestive sys. & internal organs
- Long, thin cells
- 2. Striated
- Skeletal muscles
- Acetlycholine causes contraction
- With no acetlycholine, relaxes
- 3. Cardiac muscles
- Smooth & skeletal combo
- Looks striated
- Acts like smooth
- Many individual fibers
- Fibers fuse together at points
- One axon may innervate more than one muscle fiber
- Distinctive Firing Rhythm
- They just beat
- 1. Smooth muscles
- Principles
- One movement per muscle
- Contraction; relaxation
- Antagonistic muscles
- Two in opposite directions
- Flexor muscles
- limbs flexed or raised
- Extensor muscles
- extend or straighten limbs
- Fast and Slow Muscles
- Contractions are chemical
- Affected by temperature
- Fish use more muscles in cold, fewer muscles in warmer water
- Fish muscles:
- Red : slow move, no fatigue
- White : fast move, quick fatigue
- Pink : intermediate on both
- Human Muscles
- Muscle fibers are mixed
- Fast-twitch fibers: fast contractions, fast fatigue
- Slow-twitch fibers: slower contraction, less fatigue
- Aerobic: use oxygen during movement
- Walking, swimming, running
- Anaerobic = don’t use oxygen
- Short burst
- Less that 2 min.
- Fast-twitch fibers fatigue quickly
- oxygen is needed for recovery
- produce lactate and phosphate
- give sensation of fatigue
- People vary in amounts of fast- and slow-twitch
- can increase one or the other
- depending on which use
- Proprioceptors
- receptor that detects position
- indicates movement of body part
- detect stretch & tension of muscle
- Stretch reflex
- Also called myotatic reflex
- Monosynaptic reflex
- Muscle lengthens, spindle stretches
- Increases nerve activity
- Contracts muscle, resist stretch
- Muscle spindle
- Kind of proprioceptor
- Inside muscle
- Detect changes in length
- Also activates stretch reflex
- Resist muscle stretch
- Golgi tendon organ
- Located in tendons
- At ends of muscles
- Inhibit contraction when too intense
- Involuntary Movements
- Reflexes
- Consistent
- Automatic responses
- Not affected by reinforcements, punishments, and motivations
- Pupil constricting to bright light
- Infantile Reflexes
- Infants have more
- Grasp reflex = put object in hand, grasp tightly
- Babinski reflex
- Stroke sole of foot
- Extend big toe, fan others
- Rooting Reflex
- Touch cheek, turn head & suck
- Not pure reflex
- Intensity increase when hungry
- Infantile reflexes fade with time
- suppressed by maturing brain
- sometimes reappear when brain damaged
- Life-long Reflexes
- Knee jerk reflex
- Lengthen muscle fibers
- Monosynaptic reflex
- Not involve brain
- When muscles lengthen
- reflexively contract
- Helps in posture
- Sneezing
- Coughing
- Movements
- Most behaviors are not purely voluntary or involuntary
- Most are sensitive to feedback
- Ballistic movements
- Once initiated, can’t be altered
- Completely ballistic are rare
- Behavior Sequences
- Central pattern generators
- Generate rhythmic patterns of motor output
- wings flapping
- fin movements
- Motor programs
- Fixed sequence of movements
- Can be learned or built in
- *************
- 1. Primary Motor Cortex (con’t)
- Posterior parietal cortex
- Planning a movement
- Keeps track of body position
- Intention to move
- Damage causes
- trouble converting visual perceptions into actions
- trouble finding objects in space
- Supplemental Motor Region
- Plan-organize rapid sequences
- pushing, pulling, and then…
- Mirror Neurons
- Function
- Preparing to do movement
- Watching someone else do it
- Type of cell or function?
- Some innate
- Some acquired by experience
- Imitating & understanding others
- Modeling
- Plan-organize rapid sequences
- Posterior parietal cortex
- 2. Pre-Motor Cortex
- Preparing for movement
- Somewhat active during move
- Receives info about
- Where target is in space
- Current position of your body
- Damage
- Poorly planned movements
- Cerebellum
- Balance and coordination
- More neurons than rest of brain combined
- Damage
- Problems making rapid move
- Anything require aim & timing
- Point at moving object
- Clapping hands
- Writing, typing
- Not good at discrete tasks
- Good at continuous tasks
- Drawing continuous circle
- Functions
- Saccades:
- Ballistic eye movements
- From one fixed point to next
- Gaze following moving objects
- Finger to nose test
- Alcohol
- 1st brain area impacted
- Clumsiness
- Slurred speech
- Inaccurate eye move
- Saccades:
- Other Functions
- Feel things with both hands
- Decide if two objects same
- Habit formation
- Timing
- Attention
- Cellular Organization
- Input from
- spinal cord
- sensory systems (eyes, ears…)
- cerebral cortex
- Neurons characteristics:
- Precisely arranged
- Geometrical patterns
- Multiple copies of same unit
- Parallel fibers
- Parallel to each other
- Perpendicular to Purkinje cells
- Purkinje cells
- Flat cells in sequential planes
- Inhibit cells in cerebellum nuclei
- Inhibit vestibular nuclei too
- Controls timing of movement including onset & offset
- Motor coordination
- Integration of auditory-visual info
- Skilled movements
- Dancing
- Throwing
- Modular structure
- Coordinates movements, not cause them
- Regulator or timing mechanism
- Timing of skilled movements
- Posture and balance
- Highly impacted by alcohol
- Speaking rhythm (slur)
- Can’t walk straight
- Finger to nose test
- Cells highly organized
- Repeating geometrical patterns
- Basal Ganglia
- The Basal Ganglia
- Group of subcortical structures
- includes caudate nucleus, putamen & globus pallidus
- Multiple connections
- with cerebral cortex & thalamus
- Regulates (inhibits) thalamus
- Uninhibited movements become actions
- Important for things can’t put into words
- Learning movements
- Movement patterns more consistent from trial to trial
- Inhibition of Movement
- Antisaccade task
- Task: Look in opposite direction of moving object on periphery of visual field
- Very hard to do
- Very strong tendency to watch moving object
- Almost impossible for kids 5-7
- Ability develops slowly
- prefrontal cortex is one of slowest brain areas to reach maturity
- Conscious Decisions
- Readiness Potential?
- Motor cortex activity may proceed decision to move
- Decisions to make movement unconscious?
- Connects To Spinal Cord
- Two tracts
- Lateral corticospinal tract
- Medial corticospinal tract
- Two tracts
- 1. Lateral corticospinal tract
- Axons from
- primary motor cortex
- red nucleus of midbrain
- Path downward
- Down thru white matter
- Get closer together as they go
- Go to medulla oblongata
- Medulla Pyramids
- Lateral tract crosses contralateral
- Controls move of distal limbs
- Hands, fingers, feet & toes
- Dorsolateral (pyramidal tract)
- Clumsiness of cerebral palsy is from competition of contralateral and ipsilateral paths
- Controls movement of fingers
- Controls many cranial nerves
- Controls facial muscles
- 2. Medial corticospinal tract
- Axons from
- primary motor cortex
- supplementary motor cortex
- midbrain tectum
- reticular formation
- vestibular nucleus
- Go to both sides of spinal cord
- Largely responsible for
- Neck, shoulder & trunk move
- Control posture
- Vestibulospinal: vestibular information
- Tectospinal: visual information
- Reticularspinal: controls muscles
- Axons from
- Motor Problems
- Parkinson’s Disease
- Symptoms
- First symptom is loss of smell
- Slow movements
- Resting tremor
- Rigidity
- Difficulty initiating movement
- Cognitive deficits
- Depression (no outbursts)
- Can still do
- Follow visual cues
- Follow parade
- Climb stairs
- “Step on the cracks” (sidewalk)
- Incidence
- 1–2% of those over 65
- 50% more men than women
- Progression
- Gradual progressive death of neurons
- Especially in substantia nigra
- Substantia nigra
- Less $ of motor cortex
- Slower onset of movements
- When over 45
- Neuron loss of 1% per year
- Most have enough to spare
- Early onset
- Probably genetic
- Late onset
- More common
- Not genetic
- Chances decrease if
- Drink coffee
- Smoke
- Decaffeinated coffee and nicotine free cigarettes work just as well
- Reduce damage to mitochondria
- Progressive death of neurons
- Gradual
- Decrease in dopamine
- Decreased neural activity
- Atrophy
- Cell death
- L-Dopa Treatment
- Precursor to dopamine
- Crosses BBB
- Hope it converts to dopamine
- Not prevent continued loss
- may contribute to neuron death
- Harmful side effects
- Effective in early stages?
- Could do harm?
- Doesn’t stop the disease
- Other Therapies
- Antioxidant drugs
- Dopamine agonists
- Glutamate antagonists
- Symptoms
- Huntington’s Disease
- Genetic disease
- 1:10k
- Symptoms
- Can’t learn new movements
- Restless, fidgeting
- Tremors spread
- Jerky arm movements
- Facial twitch
- Hallucinations & delusions
- Alcoholism & drug abuse
- Depression & anxiety
- Memory deficits
- Onset at any age
- Mostly 30-50
- Early onset, worse symptoms
- Can occur in kids and teens
- Excessive movement (chorea)
- Gradual brain damage
- Inevitably fatal
- Misdiagnosed as schizophrenia
- Genetic disease
- Myasthenia Gravis
- Immune system anti-bodies
- Attack acetylcholine receptors
- Symptoms
- Weakness
- Rapid fatigue
- Motor neurons can’t produce enough acetylcholine
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