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Terms in this set (54)
Two types of muscle
Striated muscle (2 types)
Smooth muscles are found in...
- the walls of blood vessels such as in the aorta and small arteries, arterioles and veins.
- lymphatic vessels
- the urinary bladder
- uterus, male and female reproductive tracts
- gastrointestinal tract
- respiratory tract
- iris of the eye
Skeletal muscles contract upon command
Cardiac and smooth muscles contract without conscious thought and are termed involuntary.
individual muscle cell formed of myofibrils.
Long strands of protein that run the length of the muscle
- Sarcomere: single segment of myofibril
- Z line: boundary of each sarcomere
- Thin filaments are made of actin (blue)
- Thick filaments are made of myosin
Overall structure of a muscle cell and neuromuscular junction (4 parts)
2. Neuromuscular junction
3. Muscle fiber
Overall structure of a Neuromuscular junction (5 parts)
1. Presynaptic terminal
3. Synaptic vesicle
4. Nicotinic acetylcholine receptor
Each action potential produces single contraction of muscle fiber.
Muscle fibers express...
In the resting muscle, troponin prevents...
interactions between actin and myosin.
Action potential—and Na+ influx—leads to internal release of
calcium in muscle fiber
Type I myosin filament
- efficient in using oxygen
- delayed muscle firing
- Do not fatigue easily
Type IIa and IIb myosin filaments
- Do not burn oxygen to create energy
- Fast to fire; best for explosive body movements
- Tire out quickly
Skeletal muscle contraction controlled by
motor neurons in the spinal cord or in nuclei of the cranial nerves
Spinal motor neurons =
alpha motor neurons
A motor unit consists of...
an alpha motor neuron and all the muscle fibers it controls
Slow twitch fibers:
neurons have small cell bodies, innervate few fibers and produce little force
Fast twitch fibers:
neurons have larger cell bodies, innervate more fibers and produce greater force.
Control of the force of our movement: 2 ways
1- varying the firing rate of motor neurons
2- recruitment: gradual activation of more motor units
Summative effect on the intracellular calcium concentration =
facilitation of the release of more troponin from actin to allow more contraction.
Activation of 1 motor neuron =
weak but distributed muscle contraction.
Activation of more motor neurons =
more muscle fibers being activated, and therefore a stronger muscle contraction
How is muscle movement sensed and controlled?
Alpha motor neurons receive input from:
-neurons from muscle spindles and Golgi tendons organs
-neurons of the brainstem and motor cortex spinal interneurons
Control of Alpha Motor Neurons
1- The muscle spindle
2- The Golgi tendon organs
Muscle spindles =
detect changes in the length of this muscle.
Alpha motor neuron innervates muscle at...
Neuro muscular junction
Extrafusal fibers are outside of the spindle and responsible for...
contracting the muscle
Gamma motor neuron innervates...
the muscle spindle
intrafusal fibers and Ia sensory fibers; relay stretch information
Muscle contraction, or force, is controlled by...
the Golgi tendon organs
A reflex is..
An involuntary and instantaneous movement in response to a stimulus: spinal control without high conscious control.
In the adult nervous system there are 2 types of reflexes
All reflexes have one thing in common...
the reflex arc is a neural pathway that controls an action reflex
5 basic components of reflexes...
reflex that requires the action of only ONE synapse between sensory and motor neurons (e.g. patellar tendon reflex)
reflex that requires interaction at more than one synapse.
the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements.
Primary motor cortex
main contributor to generating neural impulses
motor control (sensory/spatial guidance of movement)
Supplementary motor area
= planning of movement, coordination of the two sides of the body (bi-manual coordination)
Posterior parietal cortex
= transforming multisensory information into motor commands
Motor commands are/ are not initiated in the cerebellum ?
are not initiated in the cerebellum
The cerebellum ______ the motor commands of the descending pathways to make...
modifies...movements more adaptive and accurate
The basal ganglia is associated with a variety of functions, including...
voluntary motor control and eye movements
The basal ganglia exert an...
inhibitory influence on a number of motor systems.
Initiation of voluntary movement (4 steps)
1. Decision to make movement starts in prefrontal cortex and parietal lobe
2. Movement is planned in SMA (Supplementary motor area) and PMA (premotor cortex), with input from thalamus and basal ganglia
3. Primary cortex sends signals via lateral pathway
4. Lateral pathway sends signals to spinal motor neurons, which makes muscle contract.
fine voluntary motor control of the limbs.
involuntary adjustment of arm position in response to balance information; support of the body.
The ventromedial tracts control...
automatic movements such as posture and muscle tone
Amyotrophic Lateral Sclerosis (ALS)
Motor neuron disease (degeneration of neurons)
Degenerative disorder of the central nervous system
Neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and psychiatric problems
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