Movement Flashcards
All animal movement depends on the contractions of muscles. Vertebrate muscles fall into three categories:
a. Smooth muscles: Control movements of the digestive system and other internal organs.
c. Skeletal, or striated, muscles: Control movements of body in relation to the environment.
d. Cardiac muscles: The heart muscles have properties intermediate between those of smooth and skeletal muscles.
Neuromuscular junction:
A synapse between a motor neuron axon and muscle fiber.
- In skeletal muscles, acetylcholine is released at all axon terminals at the neuromuscular junction.
Antagonistic muscles:
Are necessary for moving limbs in opposite directions.
a. Flexor muscles:
b. Extensor muscles:
a. allow limbs to be flexed or raised.
b. extend or straighten limbs.
Fast-twitch fibres and slow twitch fibres (humans):
Humans have muscle fibers that are mixed together.
- Fast-twitch fibers produce fast contractions but fatigue rapidly; slow-twitch fibers produce less vigorous contractions without fatiguing.
slow twitch fibres do not fatigue because:
they are aerobic—they use oxygen during their movements.
Fast-twitch fibers fatigue after vigorous use, because:
the process is anaerobic (reactions that do not require oxygen, although oxygen is necessary for recovery). Anaerobic muscles produce lactate and phosphate, which gives the sensation of muscle fatigue.
Proprioceptor:
A receptor that detects the position or movement of a part of the body. Muscle proprioceptors detect the stretch and tension of a muscle.
Stretch reflex:
After a muscle is stretched, the spinal cord sends a signal to contract the muscle. This reaction is caused by a stretch.
Muscle spindle:
A kind of proprioceptor. When stretched, its sensory nerve sends a message to a motor neuron in the spinal cord, which sends a message back to the muscles surrounding the spindle, causing a contraction.
Golgi tendon organ:
Located in the tendons at opposite ends of muscles, these proprioceptors inhibit muscle contraction when it is too intense.
Reflexes:
Consistent automatic responses to stimuli that are generally thought to be involuntary because they are not affected by reinforcements, punishments, and motivations e.g., a pupil constricting to bright light.
b. Humans have very few purely voluntary or involuntary, reflexive or non reflexive behaviours
Ballistic movements:
Once initiated, this movement cannot be altered or corrected (e.g., reflexes).
d. Completely ballistic movements are rare, as most behaviors are subject to feedback correction.
Central pattern generators:
Neural mechanisms in the spinal cord or elsewhere that generate rhythmic patterns of motor output (e.g., wings flapping in birds, fin movements in fish, etc.).
Motor programs:
Fixed sequence of movements.
- Motor programs can be learned or built into the central nervous system.
- Examples of human built-in motor program is yawning, smiles, frowns and raised eyebrow greeting
Primary motor cortex (precentral gyrus of the frontal cortex):
Stimulation of this area elicits movements, although it is not directly connected to the muscles.
- Axons from the primary motor cortex go to the brainstem and spinal cord (which have the central pattern generators to control actual muscle movement).
- The cerebral cortex is particularly important for complex actions such as talking and writing, and less important for coughing, sneezing, gagging, laughing, or crying.
The primary motor cortex is important for making movements, not:
planning them
Posterior parietal cortex:
One of the first areas to become active in planning a movement.
- Keeps track of the position of the body relative to the environment.
- When surgeons stimulate parts of the posterior parietal cortex during surgery, patients report an intention to move.
Supplementary motor cortex:
Important for planning and organizing a rapid sequence of movements (e.g., pushing, pulling, and then turning a stick in a particular order).
Premotor cortex:
Active during preparations for a movement and somewhat active during the movement itself.
- The premotor cortex receives information about the target in space and information about the current position and posture of the body itself.
Prefrontal cortex:
Responds to sensory signals that lead to movements. Damage to this area leads to poorly planned movements (showering with clothes on for example).
Antisaccade task:
A task in which you are supposed to look in the opposite direction of a moving object on the periphery of your visual field. This is difficult because people have a strong tendency to look toward the moving object.
b. Children aged 5-7 find the task almost impossible.
c. The ability to perform the antisaccade task develops slowly because the prefrontal cortex is one of the slowest brain areas to reach maturity.
Corticospinal tracts:
Paths from the cerebral cortex to the spinal cord. We have two such tracts that nearly all movements rely on (lateral and medial corticospinal tracts)
Lateral corticospinal tract:
Axons from the primary motor cortex and from the red nucleus of the midbrain synapse in the spinal cord. In the medulla lie the pyramids, where the lateral tract crosses to the opposite (contralateral) side of the spinal cord.
- This tract controls movements of the distal limbs (e.g., hands, fingers, and toes).