bio psych week 6: motor control, balance, plasticity

reflex

fast, unlearned response to a stimuli

motor plan

complex set of commands to muscles BEFORE behavior acts

Electromyography (EMG)

records electrical activity of muscles to understand muscle activation patterns.

closed-loop control mechanism

maximizes accuracy, information flows back to the controller to guide 

open-loop control mechanism

maximizes speed, utilizing already known action with no form of feedback

The Skeletal System

determines which movement is possible (tendons, joint muscles)

Myosin (filament of a muscle fiber)

made of thick filamenta

Actin (filament of a muscle fiber) 

made of thin filament 

Fast-twitch muscle fibers

contracts rapidly but fatigues quickly (ex. eye or leg movement)

Slow-twitch muscle fibers

contracts slowly but does not fatigue readily (ex. maintaining posture)

Neuromuscular junction

point where motor neurons and muscle fiber meets

Acetylcholine (excitatory neurotransmitter)

used to create muscle contractions

Steps in Neuromuscular Junction

1) Muscle has K+ and NA+ ligand gated channels.

2) These channels are activated by a ligand or a binding molecule (Acetylcholine in this case).

3) Then, causes an Action Potential in the muscle (contraction in the muscle).

4) Alpha Motor Neuron: releasing and causing this 

Latrotoxin (can hijack the motor system)

black widow spider venom that causes a lot of acetylcholine in the neuromuscular junction at once (influx of CA+ at axon terminal, causing spontaneous muscle contractions)

BOTOX (can also hijack motor system)

release of Acetylcholine in neuromuscular junction and cuts protein needed for the NT release (ends up in flaccid paralysis or smoothening skin)

Proprioception 

information about position and movement which is crucial for coordinating movements 

Muscle Spindles (proprioception receptor)

monitors muscle length (stretching far)

Primary Sensory Ending (in muscle spindle)

axon that transmits information from the central portion (velocity of muscle stretch)

Secondary Sensory Ending (in muscle spindle)

axon that transmits information from the ends (static/stillness of muscle length)

Golgi Tendon Organs (proprioception receptor)

monitors muscle tension (pulling too hard)

The Spinal Cord 

spinal reflexes that controls autonomic responses (ex. hot hand stove)

Flaccid Paralysis (injury to spinal cord)

loss of reflexes below the level that the cut happens in the spinal cord

Polioviruses (injury to spinal cord)

destroys motor neurons in the spinal cord and cranial motor neurons in the brainstem (injures muscles needed for breathing)

The Brainstem

some muscles controlled directly by the brain (does not go through the spinal cord)

Cranial Motor Neurons (8)

send axons to muscles of head and neck

Primary Motor Cortex

region for initiation of movement that has the same “homunculus” structure as the primary sensory cortex

Homunculus

represents/controls the same body parts but sensory and motor neurons travelling differently

Pyramidal System (corticospinal system in PMC)

projects from the cortex, through the brainstem, and then to the spinal cord

Primary Motor Cortex (learning)

motor representations in certain areas are stronger as a result of training

Non-Primary Motor Cortex

contributes to motor control and modules activity

Supplementary motor area (SMA, in NPMC)

receives input from the basal ganglia and modules activity in the primary motor cortex (internally generated)

Premotor Cortex (in NPMC)

just before the PMC, the plan right before a movement is made (external cues)

Mirror Neurons (in prefrontal cortex)

active when an individual makes a certain movement and they see another individual making the same movement

Extrapyramidal System (in PMC)

runs from the forebrain to the brainstem to the spinal cord, outside of pyramids of the medulla (indirect movements like smoothness) 

Basal Ganglia

modulates movements such as smoothness and control

Substantia Nigra (one of the two midbrain nuclei)

brainstem that innervates the basal ganglia (helps smoothen and start the movements)

Subthalamic Nucleus (two of the two midbrain nuclei)

below the thalamus and interacts with the basal ganglia (helps control and stop movements)

Muscle Memory/Habit feedback

1) basal ganglia stores the habit/movement patterns

2) thalamus relays that information along

3) orbitofrontal cortext (OFC) checks if the action matches your goal and detects errors

Habit Memory and OCD

includes compulsions used to relieve anxiety related to obsessions and can result in a misfiring in habit pathway

Cerebellum

involved in the control of skilled (learned) movements and contains about half the neurons in the nervous system 

Cerebellar cortex (outer layer of cerebellum)

dominated by multipolar neurons called the Purkinje cells

Spinocerebellum (1 major functional division)

central part involved in muscle tone and coordinations

Cerebrocerebellum

lateral part involved in motor planning, learning, and memory

Vestibulocerebellum

next to the brain stem and involved in balance and coordination of eye movements

Hypokinetic (disorder of movement)

paucity of movements - little and slowed movements

Parkinson’s disease (Hypokinetic)

gradual onset starting with a tremor, leading to slow, stiff movements and loss of balance

L-DORA (treatment for Parkinson’s disease)

increase in postural sway (PS) over time and usually used to treat paralytic symptom

Deep Brain Stimulation (treatment for Parkinson’s disease)

sends electrical impulses to area responsible for that movement and shows a decrease in postural sway to smoothen even slow movement 

Hyperkinetic (disorder of movement)

excess of movement

Tourette Syndrome (Hyperkinetic)

uncontrollable repetitive movements due to overactive dopamine in the basal ganglia

Huntington’s Disease (Hyperkinetic)

progressive brain disorder that causes uncontrollable movements, emotional problems, and less of thinking ability due to a mutation in a single gene called the HIT

HIT (mutation gene in Huntington’s disease)

provides instructions for making the protein Huntington and makes it extremely lengthened