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57 Cards in this Set

  • Front
  • Back
myasthenia gravis
cause and treatment
Auto-immune disease in which antibodies attack neuromuscular junctions that bind ACh receptors together in clusters. Fiber becomes less sensitive to ACh.

Treatments are:
cholinesterase inhibiters
immunosuppressive agents
thymus removal
myosin and actin
contractile proteins and occur in all cells
triceps surae
gastrocnemius and soleus
basic unit of contraction in muscle
sacromere: components
z band: provides anchorage for thin filaments and elastic filaments

sacromers is z disc to z disc

I band - gap between thick filaments (light)

A band - where thick and thin filaments overlap (dark)

H band - gap of only thick filaments
most common type of neuron
multipolar neuron
neuron structure
can have multiple dendrites but no more than 1 axon
axonal transport
retrograde vs anterograde
anterograde - movement down the axon away from the soma

retrograde - movement up the axon toward the soma
neuroglia more numerous than neurons in the brain
action potential from axon
more dramatic change produced by voltage-regulated ion gates in the plasma membrane

only occur where there is enough density of high voltage gates

action potential is generated in the Trigger Zone

rapid up and down change in membrane voltage
functions of muscles
Movement - move from place to place, movement of body parts and body contents in breathing, circulation, feeding and digestion, defecation, urination, and childbirth
role in communication – speech, writing, and nonverbal communications

Stability - maintain posture by preventing unwanted movements
antigravity muscles – resist the pull of gravity and prevent us from falling or slumping over
stabilize joints

Control of openings and passageways - sphincters – internal muscular rings that control the movement of food, bile, blood, and other materials

Heat production by skeletal muscles as much as 85% of our body heat
deepest abdominal muscle
transverse abdominal
This muscle has parallel fibers
Rectus Abdominus
This is a bi-pennate muscle
Rectus Femoris
Phrenic nerve
supplies the diaphragm
antagonist vs synergist
synergist - muscle that aids the prime mover
stabilizes the nearby joint
modifies the direction of movement

antagonist - opposes the prime mover
relaxes to give prime mover control over an action
preventing excessive movement and injury
antagonistic pairs – muscles that act on opposite sides of a joint
carpal tunnel--what causes it?
prolonged, repetitive motions of wrist and fingers can cause tissues in the carpal tunnel to become inflamed, swollen, or fibrotic

puts pressure on the median nerve of the wrist that passes through the carpal tunnel along with the flexor tendons

tingling and muscular weakness in the palm and medial side of the hand
pain may radiate to arm and shoulder

treatment – anti-inflammatory drugs, immobilization of the wrist, and sometimes surgery to remove part or all of flexor retinaculum
rotator cuff muscles
“SITS” muscles

teres minor
characteristics of skeletal muscle
voluntary, striated muscle attached to one or more bones

striations - alternating light and dark transverse bands
results from an overlapping of internal contractile proteins

voluntary – usually subject to conscious control

muscle cell, muscle fiber, (myofiber) as long as 30 cm
characteristics of cardiac muscle
striated like skeletal muscle, but myocytes (cardiocytes) are shorter and thicker

each myocyte is joined to several others at the uneven, notched linkages – intercalated discs
appear as thick dark lines in stained tissue sections
electrical gap junctions allow each myocyte to directly stimulate its neighbors
mechanical junctions that keep the myocytes from pulling apart

sarcoplasmic reticulum less developed, but T tubules are larger and admit supplemental Ca2+ from the extracellular fluid

damaged cardiac muscle cells repair by fibrosis
a little mitosis observed following heart attacks
not in significant amounts to regenerate functional muscle
characteristics of smooth muscle
composed of myocytes that have a fusiform shape

one nucleus, located near the middle of the cell

no visible striations
reason for the name ‘smooth muscle’

thick and thin filaments are present, but not aligned with each other

z discs are absent and replaced by dense bodies
well ordered array of protein masses in cytoplasm
protein plaques on the inner face of the plasma membrane

cytoplasm contains extensive cytoskeleton of intermediate filament

attach to the membrane plaques and dense bodies
provide mechanical linkages between the thin myofilaments and the plasma membrane

sarcoplasmic reticulum is scanty and there are no T tubules
Muscular Dystrophy
muscular dystrophy - group of hereditary diseases in which skeletal muscles degenerate and weaken, and are replaced with fat and fibrous scar tissue

Duchenne muscular dystrophy is caused by a sex-linked recessive trait (1 of 3500 live-born boys)
most common form
disease of males – diagnosed between 2 and 10 years of age
mutation in gene for muscle protein dystrophin
isotonic muscle contraction
muscle changes in length with no change in tension

concentric contraction – muscle shortens while maintains tension

eccentric contraction – muscle lengthens as it maintains tension
isometric muscle contraction
muscle is producing internal tension while an external resistance causes it to stay the same length or become longer
can be a prelude to movement when tension is absorbed by elastic component of muscle
important in postural muscle function and antagonistic muscle joint stabilization
Red Fibers
slow oxidative (SO), slow-twitch, red, or type I fibers
abundant mitochondria, myoglobin and capillaries - deep red color
adapted for aerobic respiration and fatigue resistance
relative long twitch lasting about 100 msec
soleus of calf and postural muscles of the back
White Fibers
fast glycolytic (FG), fast-twitch, white, or type II fibers
fibers are well adapted for quick responses, but not for fatigue resistance
rich in enzymes of phosphagen and glycogen-lactic acid systems generate lactic acid causing fatigue
poor in mitochondria, myoglobin, and blood capillaries which gives pale appearance
SR releases & reabsorbs Ca+2 quickly so contractions are quicker
(7.5 msec/twitch)
extrinsic eye muscles, gastrocnemius and biceps brachii
the minimum voltage necessary to generate an action potential in the muscle fiber and produce a contraction
synaptic knob
little swelling that forms a junction (synapse) with the next cell
synaptic cleft
gap between neurons was discovered by Ramón y Cajal through histological observations
a state of sustained muscle contraction produced by temporal summation as a normal part of contraction

40-50 stimuli per second produces complete tetanus
protein that makes up thin muscle filaments

block the active sites to prevent binding of myosin
calcium binding protein, bound to tropomysoin molecules of thin filaments
Resting Membrane Potential

RMP exists because of unequal electrolyte distribution between extracellular fluid (ECF) and intracellular fluid (ICF)

RMP results from the combined effect of three factors:
ions diffuse down their concentration gradient through the membrane

plasma membrane is selectively permeable and allows some ions to pass easier than others

electrical attraction of cations and anions to each other
somatic sensory division
carries signals from receptors in the skin, muscles, bones, and joints
visceral sensory division
carries signals from the viscera of the thoracic and abdominal cavities
heart, lungs, stomach, and urinary bladder
somatic motor division
– carries signals to skeletal muscles
output produces muscular contraction as well as somatic reflexes – involuntary muscle contractions
visceral motor division
carries signals to glands, cardiac muscle, and smooth muscle involuntary, and responses of this system and its receptors are visceral reflexes
tends to arouse body for action
accelerating heart beat and respiration, while inhibiting digestive and urinary systems
tends to have calming effect
slows heart rate and breathing
stimulates digestive and urinary systems
efferent vs afferent
efferent - motor

afferent - sensory
cells and organs that respond to commands from the CNS
Glial cells of CNS
oligodendrocytes -form myelin sheaths in CNS each arm-like process wraps around a nerve fiber forming an insulating layer that speeds up signal conduction

ependymal cells - lines internal cavities of the brain
cuboidal epithelium with cilia on apical surface
secretes and circulates cerebrospinal fluid (CSF)
clear liquid that bathes the CNS

microglia - small, wandering macrophages formed white blood cell called monocytes
thought to perform a complete checkup on the brain tissue several times a day
wander in search of cellular debris to phagocytize

most abundant glial cell in CNS
cover entire brain surface and most nonsynaptic regions of the neurons in the gray matter of the CNS
Glial cells of PNS
Schwann cells
envelope nerve fibers in PNS
wind repeatedly around a nerve fiber
produces a myelin sheath similar to the ones produced by oligodendrocytes in CNS
assist in the regeneration of damaged fibers

satellite cells
surround the neurosomas in ganglia of the PNS
provide electrical insulation around the soma
regulate the chemical environment of the neurons
myelin sheath
composed mostly of lipids
conduction speed
fastest in large myelinated fiber
Regeneration of Peripheral Nerves
regeneration of a damaged peripheral nerve fiber can occur if:
its soma is intact
at least some neurilemma remains

fiber distal to the injury cannot survive and degenerates
macrophages clean up tissue debris at the point of injury and beyond

soma swells, ER breaks up, and nucleus moves off center
due to loss of nerve growth factor from neuron’s target cell

axon stump sprouts multiple growth processes
severed distal end continues to degenerate

regeneration tube – formed by Schwann cells, basal lamina, and the neurilemma near the injury
regeneration tube guides the growing sprout back to the original target cells and reestablishes synaptic contact

nucleus returns to normal shape
case in which membrane voltage shifts to a less negative value
shifts the voltage back to negative numbers returning toward RMP
membrane voltage 1 or 2 mV more negative than the original RMP – negative overshoot
Local Potentials
disturbances in membrane potential when a neuron is stimulated
Refractory Period
refractory period – the period of resistance to stimulation
two phases of the refractory period
absolute refractory period
no stimulus of any strength will trigger AP
as long as Na+ gates are open
from action potential to RMP
relative refractory period
only especially strong stimulus will trigger new AP
they are synthesized by the presynaptic neuron

they are released in response to stimulation

they bind to specific receptors on the postsynaptic cell

they alter the physiology of that cell
spatial summation
net effect of postsynaptic potentials
a process in which one neuron enhances the effect of another one
combined effort of several neurons facilitates firing of postsynaptic neuron
temporal summation
occurs when a single synapse generates EPSPs so quickly that each is generated before the previous one fades
spatial summation
occurs when EPSPs from several different synapses add up to threshold at an axon hillock
neural coding
the way in which the nervous system converts information to a meaningful pattern of action potentials

qualitative information depends upon which neurons fire
labeled line code – each nerve fiber to the brain leads from a receptor that specifically recognizes a particular stimulus type

quantitative information – information about the intensity of a stimulus is encoded in two ways:
one depends on the fact that different neurons have different thresholds of excitation
stronger stimuli causes a more rapid firing rate
excitement of sensitive, low threshold fibers gives way to excitement of less sensitive, high-threshold fibers as intensity of stimuli increases
other way depends on the fact that the more strongly a neuron is stimulated, the more frequently it fires