muscular system Flashcards
cell body of neuron
rough ER
synthesizes neurotransmitters
tracts
neural processes in the CNS
nerves
neural processes in the PNS
dendrites
receives input
increases SA
axon terminal
receives neurotransmitters
lacks ER and golgi
aka axolema
antrograde
away from cell body
retrograde
towards cell body
myelin sheaths
provide insulation
increases conduction speed
axons have long or large diameter (less resistance)
conduction is 150 m/s
formed by schwann cells in PNS and oligodendricytes CNS
nodes of ranvier
action potential jumps from node-node
aka saltatory conduction
white matter
myelinated axon
gray matter
unmyelinated axon
multipolar neurons
3 or more processes
bipolar neurons
2 processes
special senses (5-includes proprioception)
unipolar neurons
1 short process
afferent
sensory
towards CNS
unipolar
in PNS
efferent
motor
multipolar
towards PNS
in CNS
interneurons
most in the CNS
both motor and sensory
99% of the body’s neurons
voltage
measure of potential energy generated by separated charge (v or mv)
current
flow of electrical charge (ions) b/w 2 points (amps)
equals voltage
resistance
hindrance to charge flow
inversely proportional to current and voltage (membrane provides resistance)
insulator
high electrical resistance
conductor
low electrical resistance
chemically gated ion channels
chemical binds to ion channel, opening it
voltage gated channels
open in response to change in membrane potential
located at myelin sheath gaps (nodes of ranvier)
mechanically gated channels
open in response to physical stimuli
RMP
-70 mv
polarized
inside of membrane more negative than positive
active transport (ATP)
leak channels
more permeable to K+
ECF
higher Na+ conc. (flows in)
ICF
higher K+ conc. (flows out)
depolarization
Na+ goes in
reduction in membrane potential
repolarization
K+ goes out
increases in membrane potential
graded potentials
incoming signals operating over short distances
depolarization or hyperpolarization
chemical and mechanical channels (decay)
occurs in cell body
action potential
long-distance signals of axons
voltage channels (do not decay)
occur only in muscle cells and axons of neurons
propagated in one direction due to inactive Na+ channels
generated only at nodes of ranvier
all-or-none response
the presence or no presence of an action potential
threshold
positive feedback system
stimulus intensity
strong stimuli cause action potential to occur more frequently
absolute refractory period
when voltage-gated Na+ channels open neuron cannot respond to another stimulus
relative refractory period
threshold for action potential generation is elevated
conduction velocity
depends on axon diameter and degree of myelination
multiple sclerosis
myelin sheaths in CNS destroyed (missing Na+ channels)
demyelinated axons increase Na+ channels (causes cycles of relapse and remission)
autoimmune
symptoms= visual disturbances, weakness, loss of muscular control, sleep disturbances, urinary incontinence
synapes
junctions that mediate info transfer (neuron->neuron/neuron->effector cell)
presynaptic neuron
neuron conduction impulses towards synapse
postsynaptic neuron
neurons transmitting electrical signal away from synapse
neurotransmitter receptor region
synaptic vesicles
filled w/ neurotransmitter
synaptic cleft
fluid-filled space
prozac
enhances stimulation of neuron
SSRI
sarin gas
blocks AchE (inhibition of skeleton muscle contraction)
enhances skeletal muscle contraction
respiratory arrest (tetni of diaphragm)
chloride channels
inhibitory postsynaptic potential
farther from threshold
hyperpolarization (action potential does not occur)
Cl- move into cell, K+ moves out (becomes more neg.)
EPSP
closer to threshold
triggers action potential
promotes depolarization (more positive)
ex: glutamate
summation
EPSP and IPSP summate
only if EPSP predominates and brings to threshold, action potential occurs
neurons receive both excitatory and inhibitory inputs
temporal summation
one presynaptic neuron transmits impulses in rapid-fire order
action potentials add up
spatial summation
postsynaptic neuron stimulated simultaneously by large number of terminals at the same time
lidocaine
treats pain
local analgesic
activates graded potentials
blocks Na+ channels (no depolarization)
alcohol and barbituates
open Cl- channels (hyperpolarize)
threshold stimulus
produces graded potentials that lead up to an action potential
sub-threshold stimulus
stimulus is too small in magnitude to produce an action potential, but will depolarize
CNS
brain and spinal cord
PNS
cranial and spinal nerves
somatic
voluntary
part of PNS
autonomic
involuntary
part of PNS
sympathetic
fight/flight response
autonomic
parasympathetic
rest/digest response
autonomic
IPSP
prevents depolarization (more negative)
hyperpolarization
ex: GABA
astrocytes
in CNS
most abundant
support and brace neuron
exchange b/w capillaries and neurons
guide migration of young neurons
control chemical environment around neurons respond to nerve impulses and neurotransmitters
information processing in brain
microglial cells
in CNS
defensive cells
touch and monitor neurons
migrate towards injured neuron
phagocytize microorganism and neuronal debris
ependymal cells
in CNS
forms barrier b/w CSF in cavities and tissue fluid bathing CNS cells
line central cavities of the brain and spinal column
cilia beat to circulate CSF
oligodendrocytes
in CNS
forms insulation myelin sheaths
satellite cells
in PNS
function similar to astrocytes
schwann cells
in PNS
aka neurolemmocytes
form myelin sheaths in thicker nerve fibers
function similar to oligodendrocytes
nuclei
cell bodies in the CNS
ganglia
cell bodies in the PNS
chromatophilic substance
aka nissi bodies
found in cell bodies
terminal boutons
aka axon terminals
found in axons
the outer collar of the perinuclear cytoplasm is found on the
axons of the PNS
fascicles
bundle of muscle cells
sarcolemma
plasma membrane of muscle cells
sarcoplasm
cytoplasm of muscle cell
glycosomes
glycogen storage
myoglobin
O2 storage
myofibrils
contain sarcomeres
A band
dark band
length stays the same during muscle shortening
I band
light band
myosin
thick filament
forms crossbridges
produces power stroke (lose ADP+Pi)
actin
thin filament
pulled towards M line
sarcomere
smallest contractable unit of muscle fiber
composed of actin and myosin
SR
network of smooth ER surrounding each myofibril
stores and releases Ca2+
T-tubules
propagate AP that stimulate Ca2+ release from the SR
an extension of the sarcolemma
triad
T-tubules+SR
muscle contraction
initiated by Ach to membrane receptors on the sarcolemma
ECC
events that transmit AP along sarcolemma
lead to sliding of myofilaments
increases intracellular Ca2+
decreased Ca2+
tropomyosin blocks active sites on actin
myosin heads cannot bind to actin
muscle fiber is relaxed
increased Ca2+
Ca2+ binds to troponin
movers tropomyosin from myosin-binding sites
myosin head binds to actin
Ca2+ pumped back into SR at the end of contraction
rigor mortis
dying cells take in Ca2+->crossbridge formation, but no ATP is generated to break them
epimysium
dense irregular CT
surrounds entire muscle
separates muscles from organs
perimysium
CT surrounding fascicles
endomysium
areolar CT
surrounds individual fiber
size principle
load stimulates smaller muscle fiber activation first
motor unit
motor neuron and all muscle fibers it supplies
smaller=fine control
recruitment
controls force of contraction
multiple motor unit summation
works via the size principle
all-or-none
subthreshold stimuli
no observable contractions
threshold stimuli
stimulus strength causing 1st observable muscle contraction
maximal stimulus
strongest stimulus that increases contractile force
oxidative fibers
use aerobic pathways
glycolytic fibers
use anaerobic glycolysis
aerobic exercise
convert fast glycolytic fibers into fast oxidative fibers
hypertrophy
due to resistant exercise (anaerobic)
atrophy
result of immobilization
fibrous CT replaces lost muscle tissue
rehabilitation impossible
smooth muscle
most Ca2+ influx from outside cell
no sarcomeres, myofibrils, or T-tubules
contains dense bodies (like Z discs)
no troponin complex (calmodulin binds to Ca2+)
peristalsis
due to longitudinal and circular layers of smooth muscle and gap junctions
varicosities
bulbous swellings of nerve fibers
store and release neurotransmitters into diffuse junctions
hyperplasia
smooth muscle cells can divide and increase in numbers
Ex: estrogen’s affect on the uterus during pregnancy
stress-relaxation response
respond to stretch
retains ability to contract on demand
allows for temporary storage of contents
Ex: bladder
unitary smooth muscle
aka visceral smooth muscle
found in hollow organs
innervated by varicosities
exhibit AP’s often
coupled by gap junctions
multiunit smooth muscle
found in airways, arteries, arrector pilli, and iris of eye
AP’s are rare
contain little to none gap junctions
independent
responds to hormones
has motor units
DMD
x-linked disorder caused by the deletion of a segment of DNA coding for the AA dystrophin (cytoplasmic protein stabilizing sarcolemma)-> fragile sarcolemma tears
interstitial CT and fat replace muscle fibers
death caused by respiratory failure
cam result in hypertrophy of calf muscles
tested via checking creatine levels or EMG
can potentially be treated by gene therapy
functions of muscle
movement
posture
stability
heat generation
characteristics of muscles
extensibility
elasticity
excitability
contractility
AchE
enzyme that breaks down Ach
satellite cells
regenerate muscle cells
striations
formed by line up of sarcomeres of myofibrils
help muscle generate force and contract
sliding filament theory
actin pulled by myosin towards center (z-line closer together)
sarcomere shortens, but not myofilaments
direct phosphorylation
anaerobic
1 ATP per CP= creatine
short duration
uses creatine phosphate stored in muscles to reattach a phosphate group to ADP left behind after ATP used for energy
anaerobic metabolism
glycolysis
glucose->2 pyruvic acid
pyruvic acid converted to lactic acid
occurs in cytoplasm
produces 2 ATP
short duration
aerobic metabolism
requires O2
occurs in the mitochondria
breaks glucose into CO2, H2O, and large amounts of ATP (~32)
long duration
consists the krebs cycle and ETC
latent period
events of the ECC
no muscle tension
contraction period
cross bridge formation
increased tension
relaxation period
Ca2+ re-entry into SR
tension declines to 0
wave summation
occurs if another stimulus is applied before the muscle relaxes completely
results in unfused tetnus (partial relaxation)
fused tetnus
occurs if stimulus are given quickly enough
muscle reached maximal tension
no muscle relaxation-> prone to muscle fatigue
treppe
incomplete removal of Ca2+ from SR
muscle tension increases in a graded manner
contractions become more efficient
found in cardiac muscle
long refractory period
slow twitch red muscle
aka slow oxidative fibers
aerobic
high myoglobin content
low glycogen stores
1st to be activated
slow speed and myosin ATPase activity
fatigue resistant
Ex: running a marathon
small fiber diameter
many mitochondria
many capillaries
fast twitch red muscle
aka fast oxidative fibers
fast speed and myosin ATPase activity
aerobic (some anaerobic glycolysis)
high myoglobin content
intermediate glycogen storage
2nd to be activated
moderately fatigue resistant
Ex: sprinting
intermediate fiber diameter
many mitochondria
fast twitch white muscle
aka glycolytic fibers
fast speed and myosin ATPase activity
anaerobic
low myoglobin content
high glycogen storage
3rd to be activated
fatigable
Ex: hitting a baseball
large fiber diameter
few mitochondria
few capillaries
isometric contraction
muscle neither shortens or lengthens
cross bridge generates force, but do not move actin filaments
Ex: holding a stack of books
isotonic contraction
muscle changes length and moves in load
eccentric or concentric
eccentric contraction
muscle lengthens
Ex: extending dumbell at triceps
concentric contraction
muscle shortens
Ex: flexing dumbell at biceps
steps in smooth muscle contraction
- Ca2+ enters cytosol from ECF via voltage gated channels of SR
- Ca2+ binds to calmodulin, activating it
- activated calmodulins activates myosin light chain kinase
- the enzymes then catalyzes the transfer of phosphate to myosin, activating the myosin ATPases
- activated myosin form crossbridges w/ actin->muscle shortens/contracts
twitch
a single contraction in response to a single threshold stimulus
muscle tension
the force exerted by a contracting muscle
factors that affect muscle contraction
relative size of muscle fibers
number of muscle fibers stimulated
degree of muscle stretch
frequency of stimulation
aerobic endurance
the length of time a muscle can continue to contract using aerobic pathways
longitudinal layer of smooth muscle
results in dilation and shortening
circular layer of smooth muscle
results in constriction and elongation
terminal cisternae
part of SR
release Ca2+ into the sarcoplasm
end plate potential
voltages which cause depolarization of skeletal muscle fibers
ATP hydrolysis
ADP+Pi
dehydration synthesis
formation of ATP
agonist
aka prime mover
major responsibility for producing specific movement
antagonist
opposes or reverses particular movement
synergist
adds extra force to the same movement
reduces undesirable or unnecessary movements
fixator
synergist that immobilizes bone or muscle
origin
gives prime mover stable base on which to act
ex: maintain upright position
rectus
parallel
tranversus
fibers run at right angles
oblique
fibers run at angles to imaginary defined axis
epicranius
consists of frontal (raises eyebrows) and occipital (pulls scalp backwards) belly
aka occipitofrontalis
orbicularis oculi
closes eye
orbicularis oris
purses and protudes lips
aids in speech formation
zygomaticus
pulls lips upwards
aka smiling muscle
masster and temporalis
closes mouth
elevates mandible
buccinator
helps w/ chewing
sucking motions
lateral pterygoid
allows grinding and sliding of mandible
medial pterygoid
synergist to masseter and temporalis
closes jaw
sternocleidomastoid
major head flexor
allows for flexing, tilting, and rotating of head
platysma
depresses jaw
splenius capitis
extends and rotates head
semipiralis and longissimus capitis
extends and rotates head
erector spinae
holds spine upright
pectoralis minor
stabilizes and depresses shoulders
serratus anterior
punching motion
trapezius
extends head
shrugs shoulders
levator scapule
elevates scapula
rhomboid major and minor
adduction of scapula
latissimus dorsi
extension of arm at shoulder
teres major
synergist w/ lats
extension of arm at shoulder
rotator cuff muscles
supraspinatus, infraspinatus, subscapularis, teres minor
originates on scapula
biceps brachii
flexion of arm at elbow
brachialis
flexion of arm at elbow
corcabrachialis
flexion of arm at elbow
adduction of shoulder
pectoralis major
flexion of arm at shoulder (90 degrees)
adduction of arm at shoulder
medial rotation of arm at shoulder
deltoid
flexion of arm at shoulder
extension of arm at shoulder
abduction of arm at shoulder
adduction of arm at shoulder
medial and lateral rotation of arm at shoulder
triceps brachii
adduction of arm at shoulder
extension of arm at elbow
teres minor
adduction of arm at shoulder
lateral rotation of arm at shoulder
anconeus
extension of arm at elbow
pronator teres
pronation of arm at elbow
supinator
supination of arm at elbow
pronator quadratus
main pronation muscle of arm at elbow
flexor pollicis
flexes thumb
flexors
anterior
extensors
posterior
anterior leg muscles
flex femur at hip
extend leg
posterior leg muscles
extend thigh
flex leg
medial leg muscles
adduct thigh
iliopoas
prime mover of flexion at hip
tensor fascia latae
flexion at hip
medial rotation of thigh
sartorius
flexion at hip
weakly abducts thigh
rotates thigh laterally
longest muscle in the body
“tailor’s muscle”
hamstrings
prime movers of extension of thigh at knee
antagonists to quads
gluteus maximus
thigh extension
abducts and medially rotates thigh
thigh extensors
biceps femoris, semitendinous, semimembranous, gluteus maximus
adductors of thigh
adductor magnus, adductor longus, gracilis
abductors of thigh
gluteus medius and minimus (medially rotate thigh)
rectus femoris
sole extensor of knee
flexes thigh at hip
muscles of thigh that move the knee joint
rectus femoris, vatus lateralis, medialis, and intermedius (extend leg at knee)
tibialis anterior
dorsiflexes foot
fibularis longus
plantar flexion
eversion of foot
triceps surae
gastrocnemius, soleus, tibialis posterior (plantar flexes ankle)
muscles of the abdominal wall
rectus abdominus, external obliques, internal obliques, transverse abdominis
semitendinosus
extend at hip
flex at knee
semimembranosus
flexes and medially rotates leg at knee
gluteus medius
abduction at hip
internal oblique
flexes and bends the trunk
aids in forced expiration
external oblique
twisting trunk left and right
bending trunk side to side
contracts abdomen
“love-handles”
rectus abdominis
flexes the trunk
compresses abdominal viscera
transverse abdominis
protects internal organs
biceps femoris
extension of thigh at hips
flexion at knee
adductor magnus
adducts thigh at hips
adductor longus
adducts thigh at hips
Ach
muscarinic (visceral receptors in the CNS)-> excitatory or inhibitory
CNS or PNS-> neuromuscular junction
nicotinic (skeletal muscles, autonomic ganglia, and in the CNS)-> excitatory
NE
excitatory or inhibitory
CNS or PNS-> main neurotransmitter of postganglionic neurons in the SNS
“feel good” neurotransmitter
catecholamine
dopamine
excitatory or inhibitory
CNS or PNS-> sympathetic ganglia
“feel good” neurotransmitter
deficient in Parkinson’s DE
catecholamine
serotonin
inhibitory
CNS
role in sleep, appetite, nausea, migraines, and mood
catecholamine
histamine
excitatory or inhibitory
CNS
role in wakefulness, appetite, control, learning and memory, inflammation and vasodilation, acid secretion
catecholamine
GABA
inhibitory
CNS
principal inhibitory neurotransmitter in the brain
AA
glutamate
excitatory
CNS
“stroke neurotransmitter”
important in learning and memory
AA
glycine
inhibitory
CNS
principal inhibitory neurotransmitter of the spinal cord
AA
diverging circuit
1 input, many outputs
amplifying circuit
converging circuit
many inputs, 1 output
concentrating circuit
Ex: diff stimuli, triggering 1 memory
ionotrophic receptors
ligand-gated ion channels
action is immediate and brief
excitatory receptors are channels for cations (Na+ influx= depolarization)
inhibitory receptors allow Cl- influx (hyperpolarization)
channel-linked
Ex: Ach and AA’s
metabotrophic receptors
indirect, complex, slow, prolonged
transmembrane protein complex
Ex: catecholamines
G-protein linked
facilitation
results in a stronger signal in the postsynaptic cell due to the increase in neurotransmitters that are released
muscle atrophy is the result of loss of
actin
myosin
mitochondria
SR
extensibility
the ability of a muscle to be stretched without being damaged
excitability
ability to respond to stimuli
contractibility
ability to contract
elasticity
ability to return to normal shape
multipolar neurons
motor and interneurons
