Muscular Tissue Flashcards
(20 cards)
Functions of Muscular tissue are?
Functions:
Producing Body Movements
* Walking and running
Stabilizing Body Positions
* Posture
Moving Substances Within the Body
* Heart muscle pumping blood
* Moving substances in the digestive tract
Generating heat
* Contracting muscle produces heat
* Shivering increases heat production
Talk about the properties of muscular tissue
Types of muscular tissue?
Properties:
Excitability
* Ability to respond to stimuli
Contractility
* Ability to contract forcefully when stimulated
Extensibility
* Ability to stretch without being damaged
Elasticity
* Ability to return to an original length
Types of muscular Tissue
Skeletal, Smooth, Cardiac (walls of the heart)
Define: Striated, Voluntary
Striated
Alternating light and dark bands
(striations) as seen when examined
with a microscope (protein filaments)
Voluntary
Skeletal muscle tissue works
primarily in a voluntary manner,
meaning its activity is consciously
controlled
* To some extent, most skeletal
muscles are also controlled
subconsciously. ex) Diaphragm
Talk about Skeletal Muscle Tissue
How does muscle growth occur?
Define Satellite cells
-
Myocyte: mature muscle cell.
Skeletal muscle cells are multinucleated, long and threadlike. Myocyte = muscle fibre = muscle cell. - The number of skeletal muscle fibres is set before birth and most of these cells last a lifetime
- Muscle growth occurs by hypertrophy: an enlargement of existing muscle fibers
-
Satellite cells are quiescent cells located next to a
muscle fibre and become active when regeneration or
repair is necessary.
A muscle fiber is surrounded by?
A muscle fibre (myocyte) is surrounded by a cell membrane called a sarcolemma and contains sarcoplasm and cell organelles, including myofibrils, nuclei, mitochondria, and T tubules.
A muscle is surrounded by?
Each fascile is surrounded by?
Each muscle fiber contains?
A muscle is surrounded by a CT sheath called a(n) epymysium This sheath wraps around a bundle of muscle fascicles, blood vessels and nerves.
Each fascicle is surrounded by a CT sheath called a perimysium This CT sheath contains bundles of muscle fibres. Each muscle fibre contains myofibrils which contain filaments, the contractile organelles of a muscle cell.
Connective Tissue Components
Connective Tissue Components
Fascia
* Dense sheet or broad band of irregular connective tissue that surrounds muscles
* Epimysium, Perimysium, Endomysium
Tendon
* Cord that attaches a muscle to a bone
Aponeurosis
* Broad, flattened tendon (sheet like, also attaches muscle to bone)
Nerve and Blood Supply
- Neurons that stimulate skeletal muscle to contract are called somatic motor neurons
- The axon of a somatic motor neuron typically branches many times
- Each branch extending to a different skeletal muscle fiber
- Each muscle fiber is in close contact with one or more capillaries
Excitation-Contraction Coupling
- Somatic motor neurons of the nervous system stimulate
muscle fibers to contract - The point of synapse between the ending of a somatic motor neuron and the muscle fibre is known as the neuromuscular junction
Excitation-Contraction Coupling 2
- Acetylcholine (ACh) (Somatic motor neuron) is the neurochemical released from the motor neuron end bulb, into the synaptic cleft.
- ACh binds to a receptor on the muscle at the motor end
plate which depolarizes the motor end plate and causes
an action potential (AP) along the sarcolemma of the
muscle fibre. - The AP triggers the release of calcium into the
sarcoplasm of the muscle fibre. Calcium binds to the
contractile proteins, actin and myosin, also called
filaments. - Sliding filament theory describes the cross bridge
formation and power stroking between myosin and actin, that produce shortening of myofibrils resulting in muscle contraction - Acetylcholinesterase degrades fuction of (ACh) enabling the muscle to relax
Aerobic VS Anaerobic
Aerobic
* Inputs
Glucose and Oxygen
- Outputs
ATP, water, CO2 - Stages
Glycolysis, Kreb’s Cycle, Oxidative phosphorylation - Location
Cytoplasm (glycolysis), Mitochondria (Kreb’s cycle) - ATP Produced
Large amount (30-38 ATP)
Anaerobic
- Inputs
Glucose - Outputs
ATP, lactic acid - Stages
Glycolysis - Location
Cytoplasm (glycolysis) - ATP produced
Small amount (2 ATP)
Muscle Fatigue
Muscle fatigue is the inability of muscle to maintain force of
contraction after prolonged activity
Factors that contribute to muscle fatigue:
* Inadequate release of calcium ions from the SR
* Depletion of creatine phosphate
* Insufficient oxygen
* Depletion of glycogen and other nutrients
* Buildup of lactic acid and ADP
* Failure of the motor neuron to release enough
acetylcholine
Types of Skeletal Muscle Fibres
Muscle fibers vary in their content of myoglobin:
Red muscle fibers
* Have a high myoglobin content
* Appear darker (dark meat in chicken legs and thighs)
* Contain more mitochondria
* Supplied by more blood capillaries
* produce slow and weak contractions
White muscle fibers
* Have a low content of myoglobin
* Appear lighter (white meat in chicken breasts)
* Produce fast and strong contractions
Control of Muscle Tension
Muscle Tone
* a small amount of tension in the muscle due to weak contractions of motor units
* small groups of motor units are alternatively active and inactive in a constantly shifting pattern to sustain muscle tone
* muscle tone keeps skeletal muscles firm
* For example, muscle tone keeps the head from
slumping forward on the chest
Pharmacology
Botulinum toxin
* Blocks release of ACh from synaptic vesicles, which essentially blocks muscle contraction
* May be found in improperly canned foods
* A tiny amount can cause death by paralyzing respiratory
muscles
* Used as a medicine (Botox®)
Curare
* Causes muscle paralysis by blocking ACh receptors on Na+ ion channels along the motor end plate
* A plant poison used by South American Indians on arrows and blowgun darts
* Derivatives of curare are used during surgery to relax skeletal muscles
Anticholinesterase
* Slow actions of acetylcholinesterase and removal of ACh
* Can strengthen weak muscle contractions
Cardiac Muscle Tissue
- Found only in the walls of the heart
- Striated like skeletal muscle
Heart contraction:
* Involuntary, not consciously controlled
* Contraction of the heart is initiated automatically by a
node of tissue called the “pacemaker”
* Continuous, rhythmic activity is a major physiological
difference between cardiac and skeletal muscle tissue
* Contractions lasts longer than a skeletal muscle twitch
* Depends on aerobic respiration to generate ATP, with
large and numerous mitochondria that require a constant
supply of oxygen
Smooth Muscle Tissue
- Located in the walls of hollow internal structures
- Blood vessels, airways, and many hollow organs
- Lacks the striations of skeletal and cardiac muscle tissue
- Usually involuntary
- Contraction lasts longer than skeletal muscles and hence
able to sustain long-term muscle tone
Regeneration or Growth of Muscular Tissue
- Skeletal muscle has limited regenerative abilities
- Satellite cells assiste skeletal muscle cells if needed.
They divide slowly and fuse with existing fibres. Assist in muscle growth Repair damaged fibers. - Skeletal muscle grows via hypertrophy
- Cardiac muscle can undergo hypertrophy in response to
increased workload - Many athletes have enlarged hearts
- Smooth muscle cells have the greatest capacity to
regenerate because they retain their ability to divide.
Aging and Muscular Tissue
- With aging, there is a slow, progressive loss of skeletal muscle mass
- A decrease in muscle strength
- A slowing of muscle reflexes
- A loss of flexibility
- The relative number of red muscle fibers appears
to increase - Aerobic activities and strength training can slow
the decline in muscular performance
Summary
- Filament -> myofibril -> muscle fibre -> fascicle -> muscle
- Connective tissue (Epimysium, perimysium, endomysium contains the 3 levels of bundles of fibres.
- The neuromuscular junction requires ACh to depolarize the sarcolemma, and muscle contractions require Ca++ to occur.
- Anaerobic metabolism occurs in the cytosol and produces very little ATP. Aerobic cellular respiration occurs in the mitochondria and produces a lot of energy.
- There are 2 types of skeletal muscle fibres: Red and White. Skeletal muscle is striated and under voluntary control. Somatic motor nerves depolarize muscle fibres which cause contractions.
