phys review session #2 Flashcards
ALS (Leu gherings)
-state physiologic cause
-caused by the degeneration of upper and lower motor neurons
-descending tracts become physically hardened
ascending pathways
go to spinal chord > synapse in 1st, 2nd, 3rd order neurons > post central gyri is final destination
what is the primary somatosensory cortex?
post central gyri
descending pathways
*talking motor
go to 2 neurons > then precentral gyrus > then to affected tissue
isotonic muscle contractions
-load remains constant as muscle changes
*eccentric and concentric
concentric= muscle shortens
eccentric= muscle lengthens
isokinetic contractions
-constant motion
-velocity remains constant as the muscle fibers shorten
isometric muscle contraction
-constant length
-muscle length remains constant as tension increases
what do bones function as
levers
what do joints function as
fulcrums
skeletal muscles provide _____ to _____ bones
force, move
what do muscle receptors do?
they provide afferent info needed to control skeletal muscle activity
function of muscle spindles
monitor muscle LENGTH
what do golgi tendon organs do?
detect changes in TENSION- found in tendons of muscle
stretch reflex
local negative feedback mechanism to sense and resist changes in muscle length when an additional load is applied
muscle spindle structures
-distributed throughout skeletal muscle
-each spindle innervated by efferent neuron
*intrafusal-y motor neuron
*extrafusal-a motor neuron
-afferent sensory endings
*annulospiral endings=central portion of INTRAFUSAL fibers
*secondary (flower spray) endings= ends of INTRAFUSAL fibers
hemiplegia
one side of motor cortex damaged
paraplegia
thoracic spinal chord damaged
decebrate and decorticate posturing (rigidity) caused by?
severe brain injuries
-descending motor tracts that control flexor muscles = destroyed
-descending motor tracts that control extensor muscles = spared
where will sensory info terminate?
post central gyrus
where will appropriate motor response originate?
pre central gyrus
NT released by pregang neurons of ANS
ACh to stimulate post gang neuron
what NT do sympathetic post gang neurons release?
norepinephrine
what NT do parasympathetic post gang neurons release?
Ach
nitric oxide
released by parasympathetic fibers in the penis, causes vasodilation and allows for erection
*binds to g coupled protein receptor
cholinergic receptors
bind to ach
muscarinic receptors
-Cardiac, smooth muscle, glands
-Bind ACh from parasympathetic postganglionic fibers
-GPCR’s that activate 2nd messenger pathways
-Excitatory or inhibitory
what is the motor unit of muscle contraction?
motor neuron and all the fibers it innervates
patellar tendon reflex
Stretching of muscle spindle of the quadriceps femoris results in contraction
cross extensor reflex
*type of withdrawal reflex
The crossed extensor reflex is a withdrawal reflex. The reflex occurs when the flexors in the withdrawing limb contract and the extensors relax, while in the other limb, the opposite occurs.
flexor withdrawal reflex
The flexor reflex is initiated by cutaneous receptors, involving an entire limb. This is exemplified by pulling the hand back from a hot object, via flexing of the arm
Parkinson’s disease
a progressive disorder that is caused by degeneration of nerve cells (dopaminergice fibers) in the part of the brain called the substantia nigra, which controls movement.
smooth muscle cross bridge cycle
-thin filaments lack troponin
-contraction relies on thick filaments (myosin-linked regulation)
-activation occurs when calcium binds to calmodulin
-this activates myosin light chain kinase (phosphorylates myosin)
-calcium is reduced and kinase is inactivated and myosin dephosphorylated
-smooth muscle relaxes
skeletal muscle contraction
-actin= where binding sites for myosin are; when tropomyosin blocks these sites the muscle is relaxed
-When Ca2+ binds to troponin, tropomyosin shifts away from binding site
-Once complex shifts, actin/myosin bind at cross-bridges
-Myosin heads “move” and muscle contracts results
nicotinic receptors
-on postganglionic cell bodies of all autonomic ganglia
-Receptors are Na+ & K+ channels
-Results in net depolarization and action potential.
-Excitatory
adrenergic receptors
Alpha (α) receptors:
α1 – excitatory
α2 -inhibitory
Beta (β) receptors:
β1 – excitatory
b2-inhibitory
*bind to epi and norepinephrine
propranolol- beta blockers
Competitive antagonists that block the receptor sites for epinephrine (adrenaline) and NE on adrenergic beta receptors.
atropine (anatagonist)
-Blocks effects of ACh at muscarinic receptors but not nicotinic receptors.
-Muscarinic junctions are parasympathetic (for this example, glands)
-Use to suppress salivary and bronchiole secretions before surgery without interfering with sympathetic activities (e.g., heart rate).