Chapter 11 Flashcards
1
Q
simple motor control
A
- spinal connections between dorsal (sensory) and ventral (motor) roots provide basis for simple movements
- REFLEX: basic unit of movement; simple, unvarying, unlearned response to sensory stimuli
2
Q
complex motor control
A
- complex set of commands to muscles that is established before behavior starts; present in both humans and animals
- feedback from movements modifies, fine-tune, and regulates motor sequence
- involves coordination with different parts of cortex areas (emotions, planning, decision-making)
- mechanism of closed-loop feedback control system:
+ regulates and controls movement:
+ control signal -> ERROR DETECTOR -> error signal -> CONTROLLER -> command -> CONTROLLED SYSTEM -> output -> TRANSDUER -> feedback signal -> ERROR DETECTOR
3
Q
hierarchy of motor control systems
A
- SKELETAL SYSTEM: allow for movement via attached muscles
- SPINAL CORD: controls skeletal muscles
- BRAINSTEM: integrates motor commands
- PRIMARY MOTOR CORTEX: initiates commands for action
- NONPRIMARY MOTOR CORTEX: provides an additional source of motor commands
+ CEREBELLUM and BASAL GANGLIA modulate activities of these control systems, sometimes via THALAMUS
4
Q
skeletal system
A
some behavioral properties arise from physical characteristics of the skeleton:
- limbs shape an animal’s stride
- type of joint determines direction of movement
5
Q
muscle
A
- composed of MUSCLE FIBERS, each containing 2 kinds of regularly arranged, overlapping filaments:
+ THICK filaments made of MYOSIN
+ THIN filaments made of ACTIN - filaments overlap -> muscle’s striped appearance (STRIATED MUSCLE)
- contraction shortens fibers’ length
- TENDONS connect muscle to bone
- ANTAGONISTS: muscles that contract when others extend/relax
- SYNERGISTS: muscles that act together
6
Q
motoneurons
A
nerve cells in the spinal cord that send their axons to innervate muscles
- FINAL COMMON PATHWAY through which brain and spinal cord control muscles
- firing patterns determine the onset, coordination, and termination of muscle activity
- release only ACh -> muscle contractions BUT respond to a variety of synaptic transmitters (excitatory - glutamate, induces movement, and inhibitory - GABA, prevents firing) released by diverse inputs that motoneurons receive
+ running -> see stop sign -> visual cortex signals stop -> muscles stop
- action potentials travel down motoneuron, which branches into many terminal near its target
- NEUROMUSCULAR JUNCTION (NMJ): where motoneuron terminal and muscle fiber meet -> effective synapse, almost every action potential elicits a contraction
7
Q
feedback control of muscle movement
A
- proprioception: collection of information about body movements and positions; perception system in peripheral system) -> inputs feedback and prevents damage + injury
- receptors:
+ MUSCLE SPINDLES
+ GOLGI TENDON ORGANS
8
Q
proprioceptive receptors: muscle spindles and Golgi tendon organs
A
- MUSCLE SPINDLES: responsive to STRETCH, consist of afferent (move toward) and efferent (move away from) elements
+ muscle stretches -> spindle stretches -> afferent nerve impulses to inform brain of stretch
+ e.g. stretching -> sense tension -> sen signal to brain “stop, you’re gonna hurt yourself” -> brain sends signal to stop -> muscles stop - GOLGI TENDON ORGANS: responsive to muscle CONTRACTION
+ stimulation inhibits motoneurons acting on muscles -> relax tension and prevent damage
9
Q
muscle control: spinal cord vs. brain
A
- STRETCH REFLEX: controlled at SPINAL level
+ example: hold heavy book -> muscle stretches first (can’t hold) -> excitation of muscle spindle afferents (SNa) -> excitatio of motoneurons -> muscles oppose stretch (lift up -> contract + control) - BRAIN level: CRANIAL MOTOR NUCLEI in the BRAINSTEM innervate muscles of head and neck -> does not go through spinal cord
10
Q
major motor pathways
A
- send signals from brain to spinal cord to control muscles
- PYRAMIDAL SYSTEM (or CORTICOSPINAL SYSTEM): directly innervate motoneurons of spinal cord or brainstem
+ consists of:
+ neuronal cell bodies in cerebral cortex
+ axons, which pass through brainstem to spinal cord -> form PYRAMIDAL TRACT
+ right cortical regions -> left side of body, vice versa - EXTRAPYRAMIDAL SYSTEM: modulate and regulate motor control (indirect)
11
Q
primary motor cortex (M1)
A
- many axons in pyramidal tract originate from neurons here
- initiate and control body movements directly
- very large regions are devoted to body parts involved in complex movements -> different parts of M1 correspond to different parts of body -> highly organized, allow for specific control of movement
+ disproportionately large regions in M1 map (hand, lips) = devoted to most elaborate and complex movements - many neurons rest when certain muscles contracted -> M1 correspond to muscle
+ e.g. move finger -> many groups of neurons fire simultaneously -> flexible system - signals from neurons in motor cortex of monkeys and paralyzed humans can be used to control robotic arms in 3D
12
Q
nonprimary motor cortex
A
- lies in frontal lobe and anterior to M1, has 2 regions:
+ SUPPLEMENTARY MOTOR AREA (SMA): modulates activity of primary motor cortex -> important for planning movement sequence that is generated internally
+ e.g. planning what to say net -> planning sequence of motor movements (lip contractions)
+ SMA also activated by mental rehearsal of a complex movement
+ e.g. “singing” in your head but not out loud
+ PREMOTOR CORTEX: contains neurons that fire when motor sequences are guided externally by stimuli (e.g. auditory/visual cues)
+ e.g. want to lift table -> as for help
13
Q
mirror neurons
A
- become active when an individual makes a particular movement (monkey picks up a ball) OR when an individual sees another individual make that same movement (monkey sees someone pick up a ball)
- important in the understanding of other individuals’ actions and in attempts to imitate those actions (empathy, understanding intention, self-awareness, imitation - language, autism - difficulty talking to people and maintaining eye contact comes from not being able to copy others?)
- many vertebrates have mirror neurons but only those with high cognitive functions have a lot
- females have more mirror neurons than males -> show more empathy
- e.g. yawning -> if you yawn or see others do -> trigger yawn
- e.g. musicians vs. non-musicians (NM)
+ when musicians just listen w/o playing: motoneurons still fire
+ NM don’t show same action, because they haven’t been exposed to the same experience before
+ experiment: use electrodes to observe neural activity when engage in a physical one (pick up ball) -> see if same circuit light up
14
Q
extrapyramidal system
A
- includes motor tracts that do not run through medulla
+ system = “extrapyramidal” -> distinguish from tracts of motor cortex that reach targets by traveling through pyramids of medulla - most important components:
+ BASAL GANGLIA: forebrain nuclei that modulates movement -> determine attitude/direction of movement, initiation of movement
+ important for memory-based motor movement/learning -> reinforcement learning/conditioning
+ has complex feedback loop connecting to cortex, mediated by dopamine produced by substantia nigra
+ CEREBELLUM: receives information from sensory systems, spiral cord, other parts of brain -> regulates and coordinates voluntary motor movements (posture, balance, coordination, speech)
+ in vertebrates, size varies according to range and complexity of movements
+ CEREBELLAR CORTEX: contains PURKINJE cells, only end inhibitory messages -> guide movement through inhibition
15
Q
muscular dystrophy (MD)
A
- disorders that lead to degeneration and changes in muscle structure
+ caused by gene mutation in X chromosome -> more likely in males
+ DYSTROPHIN: protein needed for normal muscle function, produced by gene on X chromosome
