week 7 Movement Flashcards
What are the functions of muscles?
to create movement. movement are behaviours.
Understand the three categories of muscle.
Smooth muscle:gi system
Striated muscle; (skeletal muscle). Mix of fast-twitch fibres (fast contractions, fatigues rapidly,anaerobic) and slow-twitch fibres (less vigorous contractions, slow to fatigue, aerobic, uses oxygen).. Use slow-twitch for walking, talking etc, things we can do for hours. Anaerobic muscle use spares glucose for the brain but build up an oxygen debt and utilises fatty acids. Still fatigue in time. Training and genetics determines the ratio of fast and slow twitch fibres.
Each muscle fibre receives info from just 1 axon, but 1 axon may innervate many muscle fibres. The more axons, the finer the movement control. eg eye has approx 1 axon per 3 muscle fibres, cf biceps has 1 axon to more than 100 fibres.
Heart muscle;
What is a neuromuscular junction, and which neurotransmitter is most important at this junction?
a neuromuscular junction is the synapse b/n neuron axon and muscle fibre. In skeletal muscle neuromuscular junctions, it is always acetylcholine acting as neurotransmitter. Acetylcholine causes muscle contracture.
What is a motor unit?
A motor unit is a nerve and all the muscle fibres it innervates.
Know the difference between a flexor and extensor muscle, and how they act in concert to produce effective movements of limbs.
Flexor muscle brings limb closer to body or decreases angle between 2 bones and extensor further away (or increases angle between 2 bones).
If there is a flexor and an extensor muscle/s operating on the same joint, one will be relaxed when the other contracts. Contraction is determined by acetylcholine and relaxation is an absence of acetylcholine.
Understand the function of the muscle spindle organ. How does the muscle spindle achieve this function?
A proprioceptor is a receptor cell detecting movement or position. Muscle spindle receptor is a type of proprioceptor which is in parallel to muscle fibres and responds when the muscle is stretched MORE THAN THE ANTAGONISTIC muscle. This results in a message via the spinal cord, such that the muscle then contracts. This is an example of a STRETCH reflex and it helps to maintain balance. An example is the knee jerk.
Understand the function of the Golgi tendon organ. How does the Golgi tendon organ achieve this function?
Golgi tendon organs are also proprioceptors. These are located in the tendons, at the ends of muscles.They respond to muscle tension. They serve to prevent excessive contraction, via the spinal cord, resulting in some interneurons inhibiting some muscle fibre contraction.
Compare and contrast the actions of these two types of proprioceptor. How are they similar? How are they different?
Muscle spindle organ located mid muscle, acts to counterbalance antagonistic muscle. Golgi tendon organ at ends of muscle acts to prevent overexertion of individual muscle.
Proprioception is not necessarily a conscious exercise involving higher levels of the nervous system such as the brain. In fact, many of the most important functions are carried out at an unconscious level and involve spinal reflex arcs. What is a reflex? Understand several types of reflex and suggest reasons why these reflexes have evolved in us.
A reflex is a muscle movement which is not under conscious control, which is the same response, given the same stimulus. Examples include the stretch reflex, pupillary light response ,gag reflex etc.Reflexes are fast due to mimimal units involved. Have evolved as likely immediate-survival aids.
A reflex is a ballistic movement-once launched it is unalterable. Other movements such as threading a needle have many feedbacks checks and adjustments.
What is a central pattern generator?
Central pattern generator-neural mechanism within spinal cord which generates rhythmic patterns of motor output. eg wing flapping etc.
Locate the primary motor area and premotor area on the lateral surface of a sketch of the human cerebral hemisphere. Note the relationship between cortical representation and precision of motor activity.
11
Know the role of each of the following areas near the primary motor cortex (it is no accident that each of these movement- and body-relevant areas is nearby):
posterior parietal,
cortex, primary,
somatosensory,
cortex, prefrontal,
cortex,
premotor cortex,
supplementary,
motor cortex.
Posterior Parietal;planning of movement. Monitors body in relation to rest of world. Damage here and may have difficulty finding objects in space despite being able to describe them.
Primary somatosensory cortex; awareness of body parts.
Prefrontal cortex:complex movements such as writing. Also involved in inhibiting movements, which develop as mature.Complex goal planning etc. Stores sensory info re target. most active immediately prior to a movement.
Premotor cortex most active just prior to a movement.
Supplementary motor cortex-involved in organization of rapid sequence of movement.
Understand the role of the motor cortex in movement generation.
Main source of brain input into spinal cord which results in movement. Produces patterns which represent the intended outcome.
Understand the location of the cerebellum, its motor functions.
Cerebellum involved in smoothing out muscle movement, sensory perception of non moving areas,violations of sensory perceptions (ie unexpected feeling), vital for precise timing of short intervals.Damage here may result in intention tremor, jerky movements, ability to judge loudness of sound without ability to judge its duration, difficulty maintaining attention, takes longer to be able to shift attention.
Cells arranged in efficient arrays of parrallel fibres and purkinje cells. Purkinje cells are inhibitory on certain movements. The arrangement is perfect for efficient rapid flow of information which is utilised to perform predictive error correction by comparing goal movement with path movement.
Understand the role of the basal ganglia in modulating movement.
Basal ganglia are strongly involved in self-initiated movement. Caudate nucleus plus Putamen = Dorsal Striatum (or Striatum).
Striatum receives input from cerebral cortex and substantia nigra, and sends output toglobus pallidus. Globus pallidus sends output to thalamus and frontal cortex.
Direct Pathway from Striatum inhibits globus pallidus which inhibits thalamus (direct effect is to likely stimulate specific movement).
The Indirect Pathway has additional back and forth connections within the globus pallidus to the subthalamus andthe net effect is likely to be suppression of unwanted movement. The Indirect Pathway is important in learning (movements/behaviours).
Both the Direct and Indirect Pathways are very active just before a movement and both are inactive when the animal is at rest.
