Muscle VI Flashcards
What is cachexia
Weakness and/or wasting due to chronic disease
Ex) cancer, ALS, muscular dystrophy
What are skeletal muscle reflexes
Changes in amount of force generated in skeletal muscle at level of spinal cord due to sensory input
Ex) adjust to stabilize movement, prevent damage
What are two ways receptors sense changes in joint movements, muscle tension, and muscle length and cause muscle reflex
- if muscle contraction needed CNS activates motor neurons to muscle fibers
- if relaxation needed sensory input activates inhibitory interneurons in CNS which inhibits motor neuron activity
What are the four components of skeletal muscle reflexes
- Sensory receptor (senses sitmulus)
- Integrating center (spinal cord)
- Efferent neurons
- Effectors (target tissue)
What is a monosynaptic reflex
Single synapse between afferent and efferent neurons (basic reflex)
What is a polysynaptic reflexes
Two or more synapses
- synaptic motor reflex have both synapses in CNS
- most reflexes
What are proprioceptors
Provide info into CNS about position of our limbs in space, movements, and effort exerted by skeletal muscles
What are 3 types of proprioceptors
- Muscle spindle
- Golgi tendon organ
- Joint receptors
What are joint receptors
Found in capsules and ligaments around joints and are stimulated by mechanical distortion that accompany changes in position of bones
What are muscle spindles
- Small elongated stretch receptors scattered among and arranged parallel to skeletal muscle fibers
- send info to CNS about muscle length + change in muscle length
What are muscle spindles made of
Sensory neuron wrapped around intrafusal muscle fibers innervated by gamma motor neurons
- extramural muscle fibers (regular) around and innervated by alpha motor neurons
- Toni ally active (always firing APs)
What is a muscle spindle reflex
Addition of load stretches the muscle and the spindles, creating reflex contraction (respond to change in length and increase force of contraction)
Wha this alpha-gamma Coactivation
Maintains spindle function even when alpha motor neurons fires and gamma motor neuron fires and muscle and intrafusal fibers both contract
What is a golgi tendon organ
Sensory neuron interwoven among collagen fibers inside a connective tissue capsule
- collagen fibers pull tights, pinch sensory neuron
- not tonic
What do Golgi tendon organs do
Respond to muscle tension (at junction of muscle and tendon)
- proposed to primarily control inhibitory reflexes to prevent muscle damage
- plays bigger role in controlling force within muscles and stability around joints
What is the Golgi tendon reflex
Protects muscle from excessively heavy loads by causing muscle to relax and drop load
What do stretch reflexes and reciprocal inhibition control
- movement around joint
- stimulus of sensory receptors promote contraction of one muscle but relaxation or inhibition of antagonist
What are flexion reflexes
Pull limbs away from painful stimuli
- ex) nociceptors sense pain and allow movement very rapidly
What is the crossed extensor reflex
Flexion reflex in one limb causes extension in opposite limb
- coordination of reflexes with postural adjustments is essential in maintaining balance
What happens in a crossed extensor reflex when painful stimulus is step on tack
- flexors contract, moving foot away from pain
- extensors contract in other leg as weight shifts to it
What is cardiac muscle made up of
- cardiac myocytes (myocardial muscle cells)
- interconnected by intercalated disks
