exam 4 Flashcards
What are the 3 types of muscles?
smooth, cardiac, & skeletal
What is smooth muscle?
found in the walls of hollow organs; made of spindle-shaped cells with 1 nucleus per cell
What is cardiac muscle?
found in the walls of the heart; made of branched, interwoven cells with 1 nucleus per cell
What are intercalated disks?
a special type of gap junction that joins cardiac muscle cells together & coordinate contraction
What is skeletal muscle?
for body movement; cylinder-shaped & can be very long; multinucleate cells with the nuclei located barely deep to the sarcolemma
What can all muscle types do?
contract, relax, & extend
Each skeletal muscle cell is covered in connective tissue called what?
endomysium
Groups of skeletal muscle cells (fascicles) are bound together by connective tissue called what?
perimysium
Bundles of fascicles are wrapped by connective tissue called what?
epimysium
The connective tissue coverings for skeletal muscle can fuse to make what structures?
tendons & aponeuroses
What is a tendon?
tough band of connective tissue that holds muscle to bone’s periosteum; holds 1 muscle to another or into skin
What is an aponeurosis?
tough, flat sheet of connective tissue
What is a fascia?
fibrous connective tissue that acts to compartmentalize muscles or separate them into groups
What are the 2 types of fascia?
superficial & deep
What is superficial fascia?
found between muscles & skin
What is a deep fascia?
found between muscles & organs & bones
Muscles attach to the body in at least 2 points which are what?
the origin & insertion
What is the origin?
the less movable point of attachment
What is the insertion?
the more movable point of attachment
What is the muscle’s action?
pulling the insertion closer to the origin; occurs when a muscle contracts
What is the prime mover?
the muscle in the group that completes most of the action
What are synergists?
“helper muscles” that aid the prime mover
What are antagonists?
muscles that perform an action opposite of the prime mover’s action
What can skeletal muscle cells also be called?
muscle fibers
What is a sarcolemma?
the cell membrane surrounding muscle cells
What is sarcoplasm?
the cytoplasm inside muscle cells; contains organelles & special protein fibers called myofibrils
What is sarcoplasmic reticulum?
special ER found in the sarcoplasm; stores Ca++ & pumps it into the sarcoplasm as needed
What are t-tubules (transverse tubules)?
hollow tubes that connect to the sarcolemma; when the muscle is stimulated, these tubes open for Na+ to rush in
What are myofibrils?
proteins used for muscle contraction; made of actin & myosin
What is actin?
thin filament made of g-actin which is globs of protein twisted around a threadlike core called nebulin (like beads on a string)
What is myosin?
thick filament that looks like 2 headed golf clubs bound together which interact with actin at myosin binding sites
What is a sarcomere?
sections in which myosin is arranged; it is the smallest contractile unit of muscle
What happens to Z-lines as muscle contracts?
they move closer together (Z-lines are the borders of a sarcomere)
What is anchored onto Z-lines? What happens to this structure when the muscle is stimulated?
actin; when stimulated, actin & myosin form cross bridges pulling the Z-lines closer together making the muscle shorten
What is tropomyosin?
a slick protein that blocks the actin’s myosin binding sites in a muscle at rest; it is held in place by another protein called troponin
What is the motor end plate?
the point in the muscle cell that acetylcholine goes to after diffusing across the synapse; then it is quickly broken down by acetylcholinesterase
What happens to the sarcolemma due to the presence of acetylcholine?
holes open & Na+ enters from the ECF; Na+ travels through the t-tubules to the SR
What does the SR do once Na+ enters it?
it responds by pumping Ca++ onto myofibrils
What does Ca++ do once it is released onto myofibrils?
it binds to troponin making it unstable; troponin falls away pulling tropomyosin off of actin’s myosin binding sites
What is step 6 of the sliding filament theory?
myosin’s heads attach to the newly exposed binding sites on the actin
What is step 7 of the sliding filament theory?
myosin’s heads pivot & pull actin which causes the sarcomere (Z-line to Z-line) to shorten
What is step 8 in the sliding filament theory?
steps 6 & 7 only give a tiny bit of contraction so they must be repeated many times; this occurs through ATP which is used to break existing crossbridges so new ones can form
What is rigor mortis?
occurs at death; if no ATP is available to break the crossbridges, the muscle is “frozen” in its contracted state
What is the final step of the sliding filament theory?
when the desired contraction is complete, Ca++ is pumped back into the SR & troponin + tropomyosin return to actin, blocking the myosin binding sites until next time
What is ATP?
provides the cell with lots of energy; adenosine triphosphate
What is ADP?
adenosine diphosphate; formed through a chemical reaction called hydrolysis in which 1 phosphate molecule is broken away from ATP
What are the 3 ways in which ATP is generated in muscles?
creatine phosphate, anaerobic, & aerobic pathways
What is the creatine phosphate pathway?
a phosphate is broken from creatine phosphate, releasing a little bit of energy which provides about 8-10 seconds of muscle contraction; helps to maintain muscle tone
What is the anaerobic pathway?
occurs without oxygen; glucose is rapidly broken down when oxygen is NOT present & its energy is transferred to ADP to form ATP
In the anaerobic pathway, how much ATP is formed from 1 glucose molecule?
2 units of ATP; this is enough for high intensity contractions of a short duration
What acid does the anaerobic pathway generate?
lactic acid
Lactic acid diffuses into the blood which decreases the blood pH. What does this do?
stimulates respiratory centers in the brain, increasing breathing rates & depths
What happens when lactic acid enters additional metabolic pathways?
it ultimately forms ATP & other molecules
What contributes to muscle soreness & fatigue?
lactic acid
What color are anaerobic cells?
light colored
Why are anaerobic cells light colored?
they have a low concentration of mitochondria, a small amount of blood vessels in their fascicles, & a lack of myoglobin
What is the aerobic pathway?
glucose is broken down inside mitochondria through chemical reactions that require oxygen which produce lots of ATP
In the aerobic pathway, how much ATP is formed from 1 glucose molecule?
about 38 units of ATP but the reactions occur slowly, providing lots of energy for long-sustained contractions
What acid does the aerobic pathway generate?
pyruvic acid which joins other metabolic pathways
What color are aerobic cells?
dark colored
Why are aerobic cells dark colored?
they have a high concentration of mitochondria, many blood vessels in their fascicles, & abundant myoglobin
What is myoglobin?
similar to hemoglobin; a red pigment that transports oxygen within the cell
What are myoblasts?
very mitotically active cells that form skeletal muscle; formed from stem cells in fetal development
How do myoblasts form skeletal muscle cells?
they slow down their cell division & align in units where the new muscle will eventually be
Is the new skeletal muscle cell formed from myoblasts mitotically active?
no; in order for muscle size to increase, the cells themselves must grow instead of dividing
How can the new skeletal muscle grow in size?
by increasing the amount of myofibrils; this is controlled hormonally by growth hormones & androgens
What are growth hormones?
produced by the pituitary gland; they cause growth of many tissues including muscle cells; these are the most active in children
What are androgens?
sex hormones such as testosterone; increase the size of a muscle cell by increasing the amount of myofibrils; occurs in adults & teens past puberty
What is fibrosis?
a process when connective tissue will fill in a damaged area of a skeletal muscle if it is cut/torn
Is muscle that is repaired through fibrosis strong?
no; it is weaker than before the damage because connective tissue can’t contract
Are myoblasts still active in adults?
a few; these could be useful to help repair skeletal muscle damage
What is the ANS?
a component of the efferent (motor) pathway; controls smooth muscle, cardiac muscle, & glands; divided into the sympathetic & parasympathetic divisions
What is the sympathetic division?
speeds up the action of the tissues that spend energy & slows down the ones that acquire energy
What is the parasympathetic division?
speeds up the action of tissues that acquire energy & slows down the ones that spend energy
What is dual innervation?
the ANS effectors are innervated by both sympathetic & parasympathetic neurons; this provides precise control
What are the 3 components of the ANS divisions (sympathetic & parasympathetic)?
preganglionic neuron, ganglion, & postganglionic neuron
What is the preganglionic neuron?
it has dendrites & cell bodies in the brain & spinal cord; their axons exit the brain & cord to travel to a ganglion
What is the ganglion?
clumps of cells bodies where preganglionic neurons synapse with postganglionic neurons
What is the postganglionic neuron?
have cell bodies in ganglia & their axons end in effectors
What is another term for the parasympathetic division?
the craniosacral division
Why is the parasympathetic division also called the craniosacral division?
the cell bodies & dendrites of the preganglionic neurons are located in cranial nerves 3,7,9,10 & in the sacral regions of the spinal cord; their axons travel to ganglia & release acetylcholine
What is another term for the ganglia in the craniosacral/parasympathetic division?
terminal ganglia; they are located near or inside effector tissues; this is the site of synapse between pre & post ganglionic neurons
What are characteristics of the postganglionic neurons in the craniosacral/parasympathetic division?
the cell bodies & dendrites are located in terminal ganglia; they have very short axons that travel to effectors to release acetylcholine
What is another term for the sympathetic division?
thoracolumbar division
Why is the sympathetic division called the thoracolumbar division?
the cell bodies & dendrites of the preganglionic neurons are located in the lateral gray horns of the thoracic & lumbar sections of the spinal cord
Where are the axons of the preganglionic neurons for the sympathetic division?
they exit as part of the ventral roots & travel a short distance to ganglia where they release acetylcholine
What are the 2 types of ganglia in the sympathetic division?
prevertebral & sympathetic trunk/chain
What are the prevertebral ganglia?
part of the sympathetic division; located anterior to vertebrae
What is the sympathetic trunk/chain ganglia?
part of the sympathetic division; located lateral to vertebrae; these house postganglionic neurons
Where can the axons of postganglionic neurons in the sympathetic division be found?
they are very long & they exit ganglia & travel to effectors where they release norepinephrine
What are cholinergic neurons?
neurons of the ANS that release acetylcholine
Do the effects of acetylcholine last long?
no; it is quickly broken down by acetylcholinesterase
What are adrenergic neurons?
neurons of the ANS that release norepinephrine
Do the effects of norepinephrine last long?
yes; it is broken down by a lot of enzymes so it happens slowly
What is unique about norepinephrine effectors?
they have alpha & beta receptors
What is sympathetic stimulation?
“fight or flight” response
What can sympathetic stimulation increase?
heart rate, contraction force, blood pressure, breathing rates/depths, & blood sugar levels (ensures adequate ATP generation)
What is epinephrine?
adrenaline; causes beta receptors to be more sensitive to norepinephrine; released by the adrenal glands which are activated from sympathetic stimulation
What happens to blood vessels during sympathetic stimulation?
blood vessels in the skin, digestive system, & urinary system constrict; blood vessels that go to skeletal muscle, heart, & brain relax
What else occurs from sympathetic stimulation?
the smooth muscle of bronchial tubes relaxes & pupils dilate
What are the parasympathetic effects?
“rest & digest” response; the reverse of sympathetic effects
Which effects last longer, sympathetic or parasympathetic?
sympathetic lasts longer because norepinephrine is broken down slower; parasympathetic is short-lived because acetylcholine is broken down faster to easily shift into sympathetic mode
