BMSC11002 Lecture Notes - Lecture 10: Active Transport, Loose Connective Tissue, Hemoglobin
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CHAPTER 10: MUSCLE TISSUE
10.1 Skeletal, cardiac, and smooth muscle tissues differ in location, structure, and function
• There are 3 types of muscle tissues:
1. Skeletal
▪ Because the function of most skeletal muscles is to move the bones of the skeleton
▪ Skeletal muscle tissues are referred to as striated because alternating light and
dark protein bands (striations) are visible
▪ Skeletal muscle tissue works primarily in a voluntary manner, it’s activity can be
consciously (voluntarily) controlled by the somatic (voluntary)divisions of the
nervous system
▪ Most skeletal muscles can be controlled subconsciously to an extent
2. Cardiac
▪ Found only in the heart where it forms most of the heart wall
▪ Cardiac muscle is also striated, but its action is involuntary
• It’s alternating contraction and relaxation cannot be consciously controlled
▪ The heart beats because it has a pacemaker that initiates each contraction – this
built in intrinsic rhythm is called autorhythmicity
3. Smooth
▪ Is in the walls of hollow internal structures, such as blood vessels, airways, and
most organs in the abdominopelvic cavity
▪ Also, attached to hair follicles in the skin
▪ Smooth muscle tissue gets its name because it lacks striations
▪ The action of smooth muscle is usually involuntary, and some muscles have
autorhythmicity
• Both cardiac and smooth muscle are regulated but the autonomic (involuntary) division of the
nervous system and by hormones released by endocrine glands
• They all share the same properties, but they differ from one another in their microscope anatomy,
location and how the nervous and endocrine system controls them.
10.2 Muscle tissue performs 4 functions and possesses 4 properties
Functions of Muscle tissue
1. Produces body movements
• Movements of the whole body, such
as walking, running
• Localised movements, such as
grasping a pencil, keyboarding, or
nodding a head
• Rely on the integrated functioning of
skeletal muscles, bones, and joints
2. Stabilises body positions
• Skeletal muscle contractions, stabilise
joints and help maintain body
positions, such as standing or sitting
• Postural muscles contract
continuously when you are awake
3. Moves substances within the body
• Sustained contractions of ringlike
bands of smooth muscle called
sphincters prevent outflow of the
contents of a hollow organ
• Temporary storage of food in the
stomach or urine in the urinary
bladder is possible because smooth
muscles close off the outlets of these
organs
• Cardiac muscles contractions of the
heart pump blood through blood
vessels
• Contraction and relaxation of smooth
muscle in the walls of blood vessels
hep adjust their diameter and thus
regulate the rate of blood flow
• Smooth muscle contractions also
move food and substances such as
bile and enzymes through the
gastrointestinal tract
• Skeletal muscle contractions promote
the flow of lymph and aid the return
of blood to the heart
4. Generates heat
• As muscle tissue contracts, it
produces heat
• Much of the heat generated by muscle
tissue is used to maintain normal body
temperature
• Involuntary contraction of skeletal
muscles is known as shivering, and
can drastically increase the rate of
heat production
Proper
ties of Muscle Tissue 1. Electrical excitability
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• A property of both muscle cells and
neurons, and is the ability to respond
to certain stimuli y producing
electrical signals called action
potentials (impulses)
• The stimuli that trigger action
potentials in muscle cells may be
electrical signals arising in:
o the muscle tissue itself, such
as what occurs in the heart’s
pacemaker,
o chemical stimuli, such as
neurotransmitters released by
neurons,
o hormones distributed by the
blood,
o local changes in pH
2. Contractibility
• The ability of muscle tissue to shorten
forcefully when stimulated by an
action potential.
• When skeletal muscle contracts it
generates tension (force of
contraction) while pulling on its
attachment points
o If the tension generated is
great enough to overcome the
resistance of the object to be
moves, the muscle shortens
and movement occurs
3. Extensibility
• The ability of muscle tissue to stretch
within limits without being damaged
• Normally smooth muscle is subject to
the greatest amount of stretching
4. Elasticity
• Is the ability of muscle tissue to return
to its original length and shape after
contraction or extension?
10.3 Skeletal muscles are surrounded by connective tissues and are well supplied with nerves
and blood vessels.
Connective tissue components:
• The hypodermis separates muscle from skin
o Composed of areolar connective tissue and adipose tissue, provides a pathway for
nerves, blood, and lymphatic vessels to enter and exit muscles
▪ Serves as an insulating layer that reduces heat loss, and protects muscles from
physical trauma
• Fascia is a sheet or broad band of dense connective tissue that supports and surrounds
muscles and other organs of
the body
o Fascia holds together
muscles with similar
functions:
▪ Allows free
movement of
muscles
▪ Carries nerves,
blood, and
lymphatic
vessels
▪ Fills spaces
between
muscles
• 3 layers of connective tissue
extend from the fascia to
further protect and strengthen
skeletal muscle
1. Epimysium – the
outermost layer of dense
connective tissue, enriches
the entire muscle
2. Perimysium – also a layer
of dense irregular
connective tissue, but surrounds groups of 10 to 100 or more muscle fibres separating
them into bundles called fascicles
▪ Fascicles are large enough to be seen by the naked eye (grainy appearance)
▪ Meat is ripped along it’s fascicles
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3. Endomysium – penetrates the interior of each fascicle and separates individual muscle
fibres from one another. It is a thin sheath of areolar connective tissue
• The epimysium, perimysium and endomysium may extend together beyond the muscle fibres
to form a rope-like tendon
o A tendon attaches muscle to bone
• When the connective tissue layers extend as a broad, flat sheet, it is called an aponeurosis
Nerve and Blood supply:
• Skeletal msucles are well supplied with blood vessels
o Generally an artery and two veins accompany each nerve that penetrates a skeletal
muscle
• The neurons that stimulate muscle fibres to contract are called motor neurons
o Each motor neuron has a threadlike process, called an axon, that extends fromm the
brain or spinal cord to a group of skeletal muscle fibres
▪ The axon of a motor neuron typically branches many times, each branch
extending to a different skeletal muscle fibre.
• The blood capillaries bring in oxygen and nutrients and remove heat and waste products of
muscle metabolism
o Especially during contraction, a muscle fibre synthesises and uses considerate ATP
(adenosine triphosphate
o The generation of ATP requires oxygen, glucose, fatty acids and other substances that
are deliverd to the muscle fibre in the blood
10.4 Each skeletal muscle fibre is covered by a sarcolemma; each of its myofibrils is
surrounded by sarcoplasmic reticulum and contains sarcomeres
• Muscular hytrophy is the major enlargemetn of existing muscle fibres
o Due to the increased production of myofibrils and other organelles resulting from forceful,
repetitive muscular activity, such as strength training
o Because hypertrophied muscles contain more myofibrils, they are capable of more forceful
contractions
• Muscular hyperplasia is an increase in the number of fibres
• Muscular atrophy is the decrease in the size, and therfore the strength of the muscles
o Result of the progressive loss of myofibrils when muscles are not used or the nerve supply
to a muscle is disrupted
• A few myoblasts exist in mature skeletal muscles as satellite cells
o They retain the capacity to fuse with one another or with damaged muscle fibres to
regenerate functional muscle fibres
o The number of new skeletal muscle fibres formed is not enough to compensate for
significant muscle damage or degeneration
• Fibrosis is the replacement of muscle fibres by fibrous scar tissue
Sarcolemma, transverse tubules, and sarcoplasm
• The multiple nuclei of a skeletal muscle fibre are located just beneath the sarcolemma, the plasma
membrane of a muscle fibre
• Thousands of tiny tubule-like investigations of the sarcolemma, called transverse tubules, extend
toward the centre of each muscle fibre
o T-tubules are open to the outside of the fibre, and thus are filled with interstitial fluid
o Muscle action potentials travel along the sarcolemma and through the T tubules, spreading
throughout the muscle fibre
o This ensures that action potentials excite all parts of the muscle fibre at essentially the
same instant
• The sarcolemma surrounds the sarcoplasm, the cytoplasm of the muscle fibre
o Sarcoplasm includes a substantial amount of glycogen, which is large molecule composed
of many glucose molecule
▪ Glycogen can be used for the synthesis of ATP
o The sarcoplasm contains a red coloured protein called myoglobin.
▪ Found only in muscle and binds oxygen molecules that diffuse into muscle fibres
from interstitial fluid
▪ Releases oxygen when mitochondria need it for ATP production
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Document Summary
It"s alternating contraction and relaxation cannot be consciously controlled: the heart beats because it has a pacemaker that initiates each contraction this built in intrinsic rhythm is called autorhythmicity, smooth. 10. 2 muscle tissue performs 4 functions and possesses 4 properties. Involuntary contraction of skeletal muscles is known as shivering, and can drastically increase the rate of heat production: electrical excitability. 10. 3 skeletal muscles are surrounded by connective tissues and are well supplied with nerves and blood vessels. 2 | p a g e: endomysium penetrates the interior of each fascicle and separates individual muscle fibres from one another. 3 | p a g e: the mitochondria lie in rows throughout the muscle fibre, strategically close to the muscle proteins that use atp during contraction so that atp can be produced quickly as needed. In a relaxed muscle fibre the sarcoplasmic reticulum stores calcium ions (ca2+: release ca2+ from the terminal cisterns of the sarcoplasmic reticulum triggers muscle contraction.
