Gross I Unit I exam

myology

the branch of anatomy that deals with the skeletal muscular system

skeletal muscle comprises what percent of total body weight?

40-50%

what is the specific function of skeletal muscle?

contractility, the production of voluntary movement

functions of skeletal muscle

movement, stability, communication, control of body openings/passages, heat production

movement function of skeletal muscle

moves air in/out of lungs
moves body content during digestion

stability function of skeletal muscle

maintains posture
holds articulated bones in place

communication function of skeletal muscle

speech, facial expression, writing/typing/texting

control of body openings functions in skeletal muscle

sphincter muscles around eyelids, pupils and mouth control admission of food, drink, and light
those that encircle urethral and anal orifices control elimination of waste

function of heat production in skeletal muscle

produce as much as 85% of body heat

musculoskeletal system

how body movements occur
bones and joints form this system

respiratory, digestive, and circulatory system

works with these for sources of energy ad nourishment

integumentary system (skin)

depends on this system for protection and elimination of heat which is produced by muscular contractions

nervous system

muscle depends on this, WHEN NORMALLY FUNCTIONING, for the stimuli other muscles could not contract

basic structural unit of a muscle

muscle fiber (cell)

fasciculi

bundles of muscle fiber

muscle fibers and fasciculi are bound together by what?

connective tissue

3 layers of connective tissue

endomysium, perimysium, epimysium

endomysium

delicate connective sheath that surrounds each individual muscle fiber, connects it to adjacent muscle fibers

perimysium

denser layer that surrounds each fasciculi and divides the muscle into a series of separate compartments

epimysium

dense layer of connective tissue that surrounds entire muscle from surrounding tissue, organs, and other muscles

the epimysium is continuous with __ and will continue on as the ___.

deep fascia; tendon

myofibril

contractile unit of a muscle
each fiber contains dozens to hundreds
formed from myofilaments actin and myosin

sarcolemma

a tough, specialized cell membrane each fiber is contained in

adult muscle may be as much as ___ the __ they were at birth

10x; diameter

hypertrophy

an increase in the size of a muscle due to an increase in the size of each muscle fiber

under most circumstances the increase in the size of a muscle is due to...

hypertrophy - an increase in the size of the individual fibers

hyperplasia

increase in the size of a muscle due to an increase in the number of muscle fibers
done through high resistance exercise and regenerative process

sarcoplasm

the cytoplasm of a muscle fiber
the amount of sarcoplasm present classifies cells as white (light) or red (dark)

sarco means

flesh

type I fibers (dark)

found in muscles where long, sustained/continuous contraction is required, endurance activities
aerobic metabolism, higher levels of continuous metabolic activity
slow twitch, extensive capillary beds, lots of sarcoplasm and myoglobin, fatigue resistant, numerous mitochondria, more fatty acids, less glycogen, atrophy with immobilization

type II fibers (white)

found in muscles used for quick, more powerful activities, sprinting/weightlifting
associated with anaerobic metabolism
less sarcoplasm and myoglobin, few capillary beds, fast twitch, fatigue easily, few mitochondria, more glycogen, less fatty acids, atrophy with aging

which muscles atrophy with immobilization?

type I

which muscles have fewer capillary beds?

Type II

which muscle type has more fatty acids

type I

which muscle type has a lesser amount of sarcoplasm and myoglobin?

type II

type I muscles are _ twitch while type II are _ twitch

slow; fast

intermediate fibers

exhibit characteristics somewhere between types I and II
contract faster than type I but slower than type II
have greater resistance to fatigue but histologically resemble type II

sarcoplasmic reticulum

elaborate, tubular network that stores and transports calcium ions to the myofibrils

transverse tubules (t-system)

allow electrical impulses to enter the muscle fiber and make their way to the myofibrils

myoglobin

red protein pigment found in sarcoplasm of the fiber
almost indistinguishable from hemoglobin of rbcs
gives color to the muscle and stores needed oxygen fibers need to utilize for its metabolism

sarcomere

smallest functional unit of the muscle and makes up myofibrils

contractile proteins

main proteins of skeletal muscle
actin in i-bands and myosin in a-bands
both interact with each other causing movement

regulatory proteins

inhibit interaction of actin and myosin preventing movement
2 most common are troponin and tropomyosin

How do troponin and tropomyosin work/

they recognize calcium as the signal to allow actin and myosin to interact with one another

calcium

eliminates the inhibition caused by regulatory proteins allowing muscles to contract
release from ER is triggered by nerve impulse from transverse tubules
once released it binds with troponin molecules on actin filaments
binding with troponin changes the shape of tropomyosin exposing myosin binding site on actin molecule

ATP (adenotriphosphate)

fuel/energy source of the muscle
allows myosin to interact with actin
requires just as much ATP to relax a muscle as it does to contract
energy is provided through breakdown of atp into adp+
aerobic and anaerobic metabolic pathways to get atp

movement of a muscle is the result of...

continuous breakdown and reconstitution of atp

aerobic metabolism pathway

takes place in mitochondria
more efficient way to produce atp, not speediest
creates more energy than is needed, excess released as heat
prefers fatty acids which are stored in body as triglycerides and released during exercise

anaerobic metabolic pathway

depends on creatine phosphate and glycogen to produce atp
1. creatine used first, allows muscle to contract immediately via storage of phosphate in muscle fibers
2. glycogen used in glycolysis to produce atp, glycogen stored in muscle fibers or liver cells
pathway works very quickly, can't go very long without lactic acid inhibiting process

lactic acid

by-product of glycolysis

metabolic pathway via exercise

phase 1- lasts for a few minutes, creatine phosphate and glycogen main energy source via glycolysis(anaerobic pathway) up to 20% of glycogen stored in muscle can be used
phase 2- shift in metabolism to aerobic pathway, using fatty acids to produce atp
phase 3- occurs as exercise intensifies, muscle fibers go back to anaerobic production of atp to utilize remainder of stored glycogen, when lactic acid builds up

ergogenic aids

techniques or substances used for enhancing performance
glycogen/carbohydrate loading
caffeine
blood doping
anabolic steroids

carbohydrate loading process

day 1- work until exhaustion to deplete glycogen stored in muscles
day 2-4- continue to exercise but eat diet high in fats/proteins
day 5-7- no exercise and diet high in carbohydrates
theory says by end of day 4 body will assume theres a problem storing glycogen so it will create more
when that is added to all the glycogen taken in through the diet there will be more glycogen available to turn into atp
effects phase 3

side effects of carbohydrate loading

light headed, dizzy, lethargic- hormonal imbalance, increased blood pressure
mental acuity suffers, judgement impaired- hypoglycemia
1:3 ratio of glycogen:water - increases weight

using caffeine

the caffeine in 2 cups of coffee after ~1 hour can help burn fatty acids more efficiently and increase calcium permeability - delays use of glycogen giving advantage in endurance activities
side effect is being a diuretic

blood doping/induced erythrocythemia

procedure to increase the oxygen carrying capacity of RBCs
theory of increasing concentration of RBCs will increase endurance threshold
1. athletes "donates" blood, blood placed in centrifuge, red blood cells separated and stored, injected back into athlete day(s) before competition boosting number of RBCs
2. using a synthetic erythropoietin (EPO) - hormone travels to blood marrow to produce RBCs, produced for anemia, can thicken blood so much it leads to cardiovascular problems and even death

risks associated with blood doping

rashes, fevers, acute hemolysis (breakdown of RBCs), transmission of viruses (needles), fluid overload leading to kidney damage and intravascular clotting of blood

anabolic steroids

can be injectable or pills
synthetic forms of testosterone, developed to try to separate its anabolic effect from its androgenic effect
work by increasing secretions of growth hormone, activating protein synthesis and preventing protein breakdown

legitimate reasons to have anabolic steroids prescribed

to restore hormonal levels in males with low testosterone
to improve mood and alleviate depression
patients who are chronically ill and become debilitated because of a lack of appetite- drugs enhance appetite, body weight and muscle mass

anabolic

growth spurt

androgenic

secondary sexual characteristics

forms of anabolic steroids

oil- injected and have fewer side effects, detectable for several months
water based- pill form, more side effects, clear system in 3-4 weeks
patches/gels- also available
stacking- when several forms are taken
pyramiding- starts with low dosage, raises to a peak, then tapers down
taken in cycles of 6-8 weeks, up to 500x therapeutic dosage

short-term side effects of anabolic steroids

headaches, dizziness, nausea
acne, especially on back
shrinkage of testicles - body thinks enough testosterone is present, can't tell the difference
increased aggressiveness
gynecomastia- development of breast tissue in males
tendon damage- can inhibit collagen formation
growth plates can close prematurely in adolescents

long-term side effects of anabolic steroids cause problems with

cardiovascular system
digestive system, liver especially
reproductive system, prostate
endocrine system

female-specific short-term side effects of anabolic steroids

increase in size of clitoris
decrease in size of mammary glands
development of facial hair
deepening of voice
tendon damage

chemical composition of muscle

mostly water
75% water
20% protein
5% others

each muscle is provided with a __ __ __ and a __ __ __

motor nerve fiber; sensory nerve fiber

nerve fibers enter and leave a muscle through the _____

connective tissue components of the muscle

motor neurons transmit...

efferent/motor impulses from the CNS to each individual muscle fiber resulting in a motor response (contraction)

motor unit

single motor neuron and the group of muscle fibers it suppliesthe

strength of a muscle contraction depends on what?

the amount of motor units being recruited

muscles that carry out precision type activities (movement of eyes, moving fingertips) contain motor units with __

fewer fibers

precision and motor units

the size of the motor unit is an indication of how much fine control (precision) that the muscle carries out muscles that carry out non-precision activities (locomotion) have motor units with thousands of fibers

neuromuscular junction

presynaptic portion- nerve ending
postsynaptic portion- sarcolemma of muscle fiber
synaptic cleft- space between pre and post synaptic portions
physiologically, biochemically, and clinically complex portion of the motor unit

anatomy/path of motor unit

originates in motor neuron in ventral horn of grey mater of CNS (spinal cord/brain stem)
continues as spinal nerves and peripheral nerves (PNS)
neuromuscular junction
sarcolemma of the muscle fiber (terminal end of unit)

how nerve impulse goes from presynaptic portion to postsynaptic portion of neuromuscular junction

nerve impulse reaches presynaptic portion of junction and ACH is released
ACH will diffuse across synaptic cleft and bind to specific receptor site on sarcolemma of muscle fiber
binding sets off action potential down transverse tubules, leading to interaction between actin and myosin thus a muscle contraction
after ACH completes its task it is broken down by enzyme ACHe into acetate and choline

myasthenia gravis

most common neuromuscular junction disorder, autoimmune disorder, inherited, not contagious
almost always starts by affecting muscles supplied by cranial nerves and progresses to extremities
many patients suffer from hyperplasia or tumor of thymus gland (thymoma)
pregnant mother has 25% chance of passing it to child
cause atrophy of skeletal muscle

nicotine

example of a drug that is able to compete with ACH molecules in binding to ACH receptor sites, actions are more prolonged than ACH
does not inhibit binding like snake venom just competes

snake venom

contains both cytotoxins and neurotoxins
prevents ACH from binding to ACH receptor sites, but do not cause action potential like nicotine

organophosphates

parathion and malathion are examples found in insecticides and are able to inactivate ACH
ACH can non longer be rapidly degraded resulting in an accumulation of ACH at postsynaptic portion of junction

botulin toxin

released from bacteria clostridium botulinum that cause botulism (severe type of food poisoning)
toxin blocks release of ACH from presynaptic portion of junction
first affects muscle supplied by cranial nerves then progresses to limb and respiratory muscles

ALL muscle fibers of a single motor unit have what?

the same histochemical composition (either type I or II)

muscle fiber of a single motor unit are considerably __ throughout the __ and __ of the muscle

scattered; length; width

sensory nerve fibers

convey to the CNS afferent/sensory impulses which originate within the muscle as a result of contraction

practically all movement require the coordination of a number of individual muscles which of which must contract at the exist proper moment with exact the proper force

in addition to coordination of muscle function, sensory nerve fibers are involved with

coordination, pain, and proprioception

proprioceptors

category of muscle sense organs that are found within the musculoskeletal system
muscle spindles are an example

muscle spindles

fluid filled sacs which contain specialized muscle fibers known as intrafusal muscle fibers
extrafusal muscle fibers are found outside the spindles
considered 3rd most complicated sense organ

intrafusal muscle fibers

have both efferent and afferent nerve fibers
helo spindles detect stretch in a muscle

extrafusal muscle fibers

have only efferent nerve fibers

golgi tendon organs

are located in tendons and detect stretch of the tendons, this triggers a reflex to inhibit muscle contractions and thus avoid injury to the muscles and its tendons

loss of proprioception

causes loss of both conscious and unconscious information as to what muscles are doing and what the position of the limbs are in
results in clumsy and uncoordinated movement, movement must be guided by vision

origin of muscle

the end of the muscle which attaches to the more or less stationary part of the skeleton
does not move when muscle contracts, its the anchor

insertion of muscle

the end attached to the portion of skeleton that moves when the muscle contracts
moves toward the origin bone

belly of muscle

the term for the flesh of the muscle that is surrounded by epimysium

tendon

connective tissue portion of muscle (continuation of epimysium) that attaches to bone
composed of collagen fibers, the layout of which gives muscle tensile strength
innervation is strictly afferent (sensory)
vascular supply varies from rich to nearly avascular since it's not as vascularized as the muscle- those with good supply will heal quicker and with better results

sharpey's fissures

collagen fibers that penetrate deep into the cortical portion of the bone

t/f traction injuries can "pull out" the tendon from the bone

f- tendon(and ligament) attachments are so strong that it cannot be "pulled out", but it can tear or an avulsion fracture can occur

avulsion fracture

when a fragment of bone is pulled out with the collagen fibers

tensile strength

the load necessary to rupture a given material when pulled in the direction of its length and allows muscle to withstand considerable amounts of pressure