Movement (Chapter 3) Flashcards
muscles that bedn a joint to bring the bones closer together are called…
flexors
muscles that straighten the joint, increasing the angle between the bones are…
extensors
flexors and extensors work in opposition.l what does this mean
when one of them contracts, the other relaxes
agonists
muscles that promote the movements required for motions such as the bending
of an elbow
anatgonists
muscles that oppose or inhibit the movement
are agonists or anatgonists required for skilled rapid movements (like throwing a dart)
- movements are started by agonsists and stopped by antagonists
- allows limb to accelerate and halt with speed+precision
co-contracion
for some movements, both muscles (anta, an) contract at the same time, which stabilizes or controls a movement such as holding an object at arm’s length
what are skeletal muscles made up of
thousands of individual muscle cells called musle fibers.
muscle fibres
each is controlled by a single alpha motor neruon that origniates in the spinal cord or brain
- each aloha motor neuron controls multiple muscles fibers (few-100)
motor unit
- alpha motor neruon plus all the muscle fibers it controls
- it is the critical link between the central nervous system and skeletal muscles
amyotrophic lateral scelerosis (ALS)
when motor neurons die.
- people lose the ability to move
two divisions of the nervous system
central, and peripheral
peripheral
nerves, and small concentrations of gray matter called ganglia. The brain sends messages to the peripheral nerves which control the muscles and internal organs
central nerovus syte,
brain and spinal cord
reflex movements
ocur without involvement of the brain or conscious attention. They instead depend on circuits of neurons located in or near the spinal cord itself
knee jerk
- stretch/myotatic reflex
- tao of thge tendon below kneww produces a slight stretch of the knee extensor muscle
-this stretch is sensed by receptors within the muscle (spindles)
-
what happens when spindles sense the extent and speed of the stretch
they sense the extent and speed of the stretch
- stimulate sensroy sensory neruons that send a barrage of impulses into the spinal cord
- in the spinal cord, the singles activate the alpha motor neruons that cause the stretched extensor muscle to contract which triggers the reflex
- antagonist flexor muscle has to relax at same time for the leg to kick forward
flexion crossed extension reflex
extensors of the opposite leg are activated (ex. when sharp object and bare foot)
what kind of info do muscle spindles provide?
- supply info about the changes in muscle length or stretch
- as a result, the brain will adjust the sensitivity of the system by a separate set of motor neruons
- these motor neruons keep the muscle spindles taut
- they re called gamma motor neurons
where do neurons communicate with muscles
neuro-muscular junctions
motor neruons
- carry instructions from the brain along long axons
- these long axons stretch from spinal cord to he muscles in hands and feet
Golgi tendon organs
- located where the muscle fibers connect to the tendon
- they detect how much force or retnsion is applied to a muscle during ongoing movement
- this increse’s the movement’s precision
central pattern generators (neruonal circuits)
- when they are activated, they produce the rhythmic patterns that occur in many movements.
evolved in primitive vertebrates. - the rhtyhmic patterns of muscle activation are generated by neurons within the spinal cord and brainstem circuits. They produce locomotion
what do all complex movments require
- input from the brain
- the higher brain regions involved in things like conscious planning initiate:
- voluntary motion
- coordinate complex sequences of movement
- tailor behavioural output to a given situation
THIS REQUIRES THAT THE BRAIN RELAYS COMMANDS TO THE APPROPRIATE SPINAL CIRCUITS
motor cortex
- essential for voluntary movement
- send signals that directly control the activation of alpha motor neurons in the spine
- some of the neurons in the cortex control the movement of functionally related muscles in an individual body part such as hand or arm. They are important for finely-tuned motor skills
- other neurons will direct the coordinated movement of a limb to a particular point in space (ex. hand delivering food to mouth)
several other brain regions particpate in parallel circuits or “loops” to modulate motor control. What regions do these include?
- the basal ganglia, thalamus, cerebellum, large number of neuron groups in midbrain and brainstem
two paths that the basal ganglia ecnompasses:
- one path appears to facilitate the desired motor program
- another path will suppress unwanted, competing actions
parkinson’s disease
- dysfunction of the basal ganglia.
- they experience degeneration of neurons in a brain region called the substantial nigra
substantia ngira
- the neurons relay signals to the basal ganglia using the neurotransmitter dopamine
dopamine
key chemical inovled in motor control
what happens when there is a depletion of dopamine ni the brain
- it gives rise to the hallmark symptoms of Parkinson’s
sympotoms of Parkinson’s
- tremor, rigidiity,
- sometimes akineseia (inability to move)
Huntington’s disease
- often display uncontrolled jerking or twicthich movements (part. in the face or extremities)
from wehre do the Huntington’s symptoms stem
- selective loss of ihnbitory neurons in the basal ganglia
- this eliminates the suppressionof random involuntary movements
cerebellum
crucial for coordinating and fine-tuning skilled movement
- receives direct input from sensory receptors in the limbs and head as well as most areas of the cerebral cortex
- neruons in cerebellum integrate this sensory info to ensure proper timing and integration of muscle action
- enables us to produce fluid movment
other important roles of cerebellu
- essential to a wide range of motor learning and coordination
- allows u to adapt to the unexpected
- allows u to perform motor tasks with increasing accuracy and skill (through regined and shapened memory programs)
- helps us recalibrate our movements as our own bodies change,
what happens when the function of the cerebellum is disturbed
poor coordination, disor-ders of balance, and even difficulties in speech, one of the most intricate forms of movement control.
common cause of acquired cerebellar degeneration
- long-term alchohol abuse
- sympotoms incld
symptoms of cerebellar degeneration
- l symptoms are poor coordina-tion, an unsteady walk or stumbling gait, changes in speech, and difficulty with fine motor skills including eating, writing, and dressing.
