Muscular System Flashcards
three types of muscular tissue
skeletal, cardiac, and smooth
the scientific study of muscles
myology
skeletal muscle tissue
- move the bones of the skeleton
- striated (alternating light and dark protein bands called striations)
- works in a voluntary manner (controlled by neurons/nerve cells that are part of the somatic/voluntary division of the nervous system)
cardiac muscle tissue
- contained only in the heart (heart wall)
- striated but involuntary
- alternating contraction and relaxation of the heart is not consciously controlled; heart beats because it has a natural pacemaker that initiates contraction (autorhythmicity)
autorhythmicity
built-in rhythm that makes the heart beat because of its natural pacemaker that initiates the contraction
several hormones and neurotransmitters can adjust heart rate by speeding or slowing the pacemaker
smooth muscle tissue
- located in the walls of hollow internal structures (i.e. blood vessels, airways, and most organs in the abdominopelvic cavity)
- nonstriated = smooth
- usually involuntary; some smooth muscle tissue like muscles that propel food through GI tract has autorhythmicity
TRUE OR FALSE: both cardiac muscle and smooth muscle are regulated by neurons that are part of the somatic voluntary division of the nervous system and by hormones released by endocrine glands.
FALSE. Cardiac and smooth muscles are regulated by neurons in the AUTONOMIC INVOLUNTARY DIVISION of the nervous system.
four functions of muscular tissue
- producing body movements
- stabilizing body positions
- storing and moving substances within the body
- generating heat
a function of the muscular tissue that allows movement of the whole body using the integrated functioning of skeletal muscles, bones, and joints
producing body movements
a function of the muscular tissue that stabilizes joints and helps maintain body positions (sitting or standing)
stabilizing body positions
e.g. postural muscles that contract continuously when one is awake
a function of the muscular tissue that sustains the contractions of ringlike bands of smooth muscles called sphincters, which prevent the outflow of the contents of a hollow organ
storing and moving substances within the body
examples of the muscle tissue storing and moving substances within the body
- temporary storage of food in the stomach or urine in the urinary bladder due to smooth muscle sphincters closing off the outlets of the organs
- cardiac muscle contractions of the heart pump blood through the blood vessels of the body (contraction and relaxation of smooth muscle in the walls of blood vessels help adjust blood vessel diameter and thus regulate the rate of blood flow)
- smooth muscle contractions also move food and substances such as bile and enzymes through the GI tract
- push gametes (sperm and oocytes) through passageways of the reproductive system
- propel urine through the urinary system
- skeletal muscle contractions also promote the flow of lymph and aid the return of blood in veins to the heart
a function of the muscular tissue that involves the process of thermogenesis to maintain normal body temperature
generating heat
involuntary contractions of skeletal muscles that can increase the rate of heat production
shivering
four properties of muscular tissue that contributes to homeostasis
- electrical excitability
- contractility
- extensibility
- elasticity
a property of the muscular tissue (and nerve cells) that enables them to respond to certain stimuli through the production of electrical signals called action potentials (impulses)
electrical excitability
term for action potentials in the muscles; term for action potentials in the nerve cells
muscle action potential; nerve action potentials
two types of stimuli trigger action potentials in muscle cells
- autorhythmic electrical signals arising in the muscular tissue itself, as in the heart’s pacemaker
- chemical stimuli, such as neurotransmitters released by neurones, hormones distributed by the blood, or even local changes in pH
a property of the muscular tissue that involves the ability to contract forcefully when stimulated by an action potential
contractility
when a skeletal muscle contracts, it generates tension (force of contraction) while pulling on its attachment points
what indicates that the tension generated in a contraction is great enough to overcome the resistance of the object to be moved?
when the muscle shortens and movement occurs
a property of the muscular tissue that involves the ability to stretch, within limits, without being damaged
extensibility
what tissue limits the range of extensibility and keeps muscle within the contractile range of the muscle cells?
the connective tissue within the muscle limits
examples of extensibility
- each time your stomach fills with food, the smooth muscle in the wall is stretched
- cardiac muscle being stretched each time the heart fills with blood
a property of the muscular tissue to return to its original length and shape after contraction and extension
elasticity
what is the separate organ in the skeletal muscles that is composed of hundreds to thousands of cells?
muscle fibers or muscle cell
two terms for the same structure
subcutaneous layer or hypodermis
- separates muscle from skin
- composed of areolar connective tissue and adipose tissue
- provides a pathway for nerves, blood vessels, and lymphatic vessels to enter and exit muscles
adipose tissue of the subcutaneous layer
- stores most of the body’s triglycerides
- serves as an insulating layer that reduces heat loss
- protects muscles from physical trauma
fascia
- dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs of the body
- hold muscles with similar functions together
- allows free movement of muscles
- carries nerves, blood vessels, and lymphatic vessels
- fills spaces between muscles
three layers of connective tissue extend from the fascia to protect and strengthen skeletal muscle
- epimysium
- outer layer encircling the entire muscle
- consists of dense irregular connective tissue - perimysium
- dense irregular connective tissue
- surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles - endomysium
- penetrates the interior of each fascicle and separates individual muscle fibers from one another
- mostly reticular fibers
TRUE OR FALSE: Many fascicles are large enough to be seen with the naked eye.
TRUE. They give a cut of meat its characteristic “grain” - if you tear a piece of meat, it rips apart along the fascicles.
tendons
attaches a muscle to the periosteum of a bone
all three connective tissue layers may extend beyond the muscle fibers to form a ropelike tendon
example is the calcaneal (Achilles) tendon of the gastrocnemius (calf) muscle, which attaches the muscle to the calcaneus (heel bone)
fibromyalgia
- chronic, painful, nonarticular rheumatic disorder that affects the fibrous connective tissue components of muscles, tendons, and ligaments
- pain results from gentle pressure at specific “tender points”; even without pressure, there is pain, tenderness, and stiffness of muscles, tendons, and surrounding soft tissues
reports:
- severe fatigue, poor sleep, headaches, depression, irritable bowel syndrome, and inability to carry out their daily activities
- no specific identifiable cause
treatment:
- stress reduction, regular exercise
- application of heat, gentle massage
- physical therapy
- medication for pain, and a low-dose antidepressant to help improve sleep
TRUE OR FALSE: Generally, an artery and two or three veins accompany each nerve that penetrates a skeletal muscle.
FALSE. Generally, an artery and ONE OR TWO veins accompany each nerve that penetrates a skeletal muscle.
somatic motor neurons
- neurons that stimulate the skeletal muscle to contract
- has a threadlike axon that extends from the brain or spinal cord to a group of skeletal muscle fibers
TRUE OR FALSE: Microscopic blood vessels called capillaries are barely found in muscular tissue.
FALSE. Microscopic blood vessels called capillaries are PLENTIFUL in muscular tissue. Each muscle fibers n close contact with one or more capillaries.
what brings in oxygen and nutrients and removes heat and the waste products of muscle metabolism?
blood capillaries
what does the muscle fiber do to ATP during contraction?
muscle fibers synthesize and use considerable ATP
these reactions require oxygen, glucose, fatty acids, and other substances that are delivered to the muscle fiber in the blood
what is the most important component of the skeletal muscle?
muscle fibers
where does the muscle fiber arise during embryonic development?
from the fusion of a hundred or more small mesodermal cells called myoblasts
what is the result of the fusion of myoblasts?
each mature skeletal muscle fiber will have a hundred or more nuclei
what happens to the muscle fiber when the fusion has occurred?
muscle fiber loses its ability to undergo cell division; thus the number of skeletal muscle fibers is set before you are born and most of these cells last a lifetime
where are the multiple nuclei of a skeletal muscle fiber located?
beneath the sarcolemma