anatomy & physiology - exam 2

Curare

drug that competitively blocks ACh receptors at the NMJ, leading to muscle paralysis

Eserine

ACh receptor inhibitor

Succinylcholine

ACh receptor agonist that is used to paralyze muscles before surgery

Myasthenia gravis

autoimmune disorder that destroys the postsynaptic ACh receptors

Lambert-Eaton Myasthenic Syndrome (LEMS)

caused by defect in voltage-gated Calcium channels leading to insufficient ACh release (not enough Ca2+v channels in neuron)

Guillain-Barre Syndrome

autoimmune demyelinating disorder resulting in paralysis

muscle tension

force created by muscle

load

weight that opposes contraction

contraction

creation of tension in the muscle

relaxation

release of tension in the muscle

muscle tone

continued steady, low level of contraction that stabilizes joins and maintains general muscle health

recruitment

more motor units stimulated (can generate more force)

dystonia

involuntary sustained muscle contractions resulting in twitching and repetitive movements or abnormal postures

blepharospasm

spasm of muscle surrounding tear duct

Parkinson’s disease

severe dystonia (originates in brain), some motor units work properly and others don’t

isotonic muscle contraction

creates movement force > load (results in a change in muscle fiber size)

isometric muscle contraction

creates tension load > force

hydrostatic force

the pressure required to block osmosis

membrane potential

created by the uneven distribution of electrical charge across the membrane

how cells create membrane potential

1 - ions are not distributed equally across the cell membrane

2 - membranes are unequally permeable to various ions

Potassium (K+)

which ion(s) are present at a higher concentration INSIDE the cell?

Sodium (Na+), Chlorine (Cl-)

which ion(s) are present at a higher concentration OUTSIDE the cell?

number of positive or negative charges inside the cell - number of positive or negative charges outside the cell

gradient (equation)

equilibrium potential for an ion

the membrane potential at which the concentration gradient and electrical potential forces are equal and opposite

nernst equation

used to calculate membrane potential if the cell is permeable to a SINGLE ion

steady state

when the net movement of an ion is 0

sarcolemma

plasma membrane of a muscle cell that has a series of tunnels called T-tubules where muscle actional potentials travel

sarcoplasm

the cytoplasm in muscle cells

motor unit

one motor neuron and all the muscle fibers it innervates

characteristics of neurons

high metabolic rate, extreme longevity, noon-mitotic

dendrites

branches processes protruding from the cell body that receive signals using receptors

axon

action potentials are sent through this

axon hillock

the region where the axon connects to the cell body

axon terminal

the distal part of the axon that forms a synapse with another cell

synapse

point of communication and connection between two different cells

synaptic potentials

they are passive and primarily by ligand gated ion channels

Excitatory (EPSP)

depolarization if the membrane potential is more positive than resting membrane potential

Inhibitory (IPSP)

hyperpolarization if membrane potential is more negative than resting membrane potential

spatial summation

channels close together on membrane activated at exact same time

temporal summation

channels open at exact same time if stimulated with high frequency

myelin

coating on internodes that increases speed of conduction of action potential

Type I skeletal muscle

slow twitch fibers, aerobic oxidative

Type IIa skeletal muscle

fast twitch fibers, anaerobic glycolytic

Type IIb skeletal muscle

fast twitch fibers, anaerobic CP

myosin

thick filament, has tail and head regions

actin

thin filament, has G-actin (monomer) and F-actin (polymer)

rigor mortis

stiffening of muscles once a person dies

neuromuscular junction (NMJ)

the synapse between a muscle fiber and a motor neuron