Muscle excitable tissue L2 Flashcards
What are the 4 tissue types?
Epithelial, Muscle (excitable), Nervous (excitable), Connective (cells, fibres, matrix)
How much of the total body weight does muscle form?
50%: 40% skeletal muscle and 10% smooth and cardiac muscle
What functions do muscles preform. Hint there should be 5 functions.
They contract, they generate heat, they generate motion, they generate force, and they provide support
What type of muscle is skeletal?
Striated, voluntary muscle
What type of muscle is cardiac?
Striated, involuntary muscle
What type of muscle is smooth?
Unstriated, involuntary muscle
Where are the nuclei located on skeletal muscle?
Peripheral nuclei
Is skeletal muscle strong or weak?
strong
What type of contractions occurs with skeletal muscle?
Short contractions
What type of contractions occurs with cardiac muscle?
Continuous contractions
Where are the nuclei located on cardiac muscle?
Centrally
Is cardiac muscle strong or weak?
Strong
Is smooth muscle stronger or weaker?
weaker
What type of contractions are associated with smooth muscle?
Continuous contractions
Where are the nuclei located with smooth muscle?
Centrally
What can a single skeletal muscle cell also be called and why?
A single skeletal muscle cell is also called a muscle fibre because of its greater length than width
What is the chemical composition of skeletal muscle?
Proteins (20%) (either as enzymes or for muscle Control) Lactic Acid (in muscle that has undergone fatigue)
ATP, ADP
Myoglobin (stores O2 & gives colour to the muscle)
What is the length of skeletal muscle cells?
Up to 75,000 µm or 2.5 feet
What is the diameter of skeletal muscle cells?
From 10-100 micrometres
What is the shape of skeletal muscle cells?
Elongated and cylindrical
Do skeletal muscle cells have an outer membrane?
Yes it is called sarcolemma
Are there nuclei and organelles in skeletal muscle cells?
Yes they are present. Mitochondria and E.R
What is the myoneural junction?
It is the synapse between motor neuron and muscle fibre
What neurotransmitter is associated with the myoneural junction?
Acetylcholine
What is a motor unit?
It is all the muscle fibres innervated by a single neuron
What is the innervation ratio of motor neuron : muscle fibres?
1:100 to 1:2000
What are the innervation ratios of eye motor neurons and gastrocnemius?
Eye motor neurons 1:23, Gastrocnemius 1:1000
What is the motor end plate of the myoneural junction?
It is a specialised area of sarcolemma under the axon terminal
What is the sarcolemma?
The plasmalemma of muscle cells. External to this cell
membrane is a well developed basement membrane
What is the sarcoplasm?
It is the cytoplasm of muscle cells excluding the myofibrils.
What is the epimysium?
A thick layer of collagenous connective tissue that
separates large bundles of muscle.
What is the perimysium?
A collagenous connective tissue that separates
smaller bundles of muscle cells called fascicles.
What is a fasicle?
It is a bundle of muscle cells bounded by perimysium.
What is the endomysium?
It is a thinner layer of connective tissue that separates
individual muscle cells.
How do muscle fibers develop?
They develop through the fusion of mesodermal cells called myoblasts
What do collagen fibres do in skeletal muscle organisation?
They blend to form tendon at end muscle
What do tendons do in skeletal muscle organisation?
Tendons attaches skeletal muscle to bone
What type of muscle are muscle fibres found?
In skeletal and cardiac muscle
What are muscle cells. Hint Fibres
Muscle cells make individual muscle fibers which are cells that are large and elongated and have multiple peripheral
nuclei that produce voluntary contractions
What are myofibril’s made up of?
Myofilaments
What are myofilaments/sarcomeres composed of?
Thick filament called myosin and thin filaments called actin
Why are striations formed?
Due to alignment of filaments of myofibrils
What happens during contraction?
The sarcomere shortens and myosin binding protein C binds myosin and actin
What is G-actin?
G-actin is the monomer which will form the thin
filament (actin). It is a protein with a molecular weight of
43 KDa. It has a prominent site for cross-linkage with
myosin.
How are actin - thin filaments formed?
G-actin goes to F-actin which is a long polymerised G-actin that is 6-7nm long and double stranded in structure and that goes to thin filaments.
What are 2 regulatory proteins of the muscles?
Tropomyosin and Troponin
What is troponin?
It is a globular protein complex that is made up of 3 polypeptides: Troponin C,I,T which forms part of thin filaments.
What does troponin C do?
Binds to Ca^2+
What is the function of troponin I?
It is inhibitory in function
What is Troponin T?
It is attached to tropomyosin
What is tropomyosin?
A rod like protein with a molecular weight of 70kDa. It has 2 chains of alpha and beta chains. It forms part of thin filaments of muscle
What does tropomyosin do under resting conditions?
It covers the site for myosin attachment on F-actin molecule
What does the protein Nebulin do in regards to thin filaments?
Nebulin provides elasticity to the sarcomere
What does the protein Titin do in regards to thin filaments?
Titin is the largest known protein in the body. It contributes to the contraction of skeletal muscle
What length are thin filaments?
1 µm
What is the diameter of thin filaments?
5-8nm
What is the number of G-actin mol?
300-400
What are thick filaments consistent of?
2 symmetrical halves that are mirror images of each other. The chief constituent is myosin.
What is the molecular weight of myosin?
480 KDa
Describe the molecule myosin?
Its molecule has 2 ends, a globular end having 2 heads and a rod like tail. It has 6 peptide chains: 2 identical heavy chains with 200 KDa each and 4 light chains with 20 KDa each
What are the 2 binding sites on the myosin molecule?
Binding site for actin and ATPase site
3 things about the innervation of cardiac muscle?
The innervation is involuntary, the pacemaker cells coordinate contraction of tissue and there is electrical conduction (Purkinje fibres and gap junctions)
Is cardiac muscle resistant to fatigue?
Yes
Does cardiac muscle have an all or none feature?
Yes (“twitch”)
What is the name for cardiac muscle cells?
Cardiocytes
What do cardiocytes contain?
Myofibrils which are striated
Where do cardiocytes cells contact each other?
At intercalated disks
What do cardiocytes cells bind together by?
Gap junctions and desmosomes
Where is the body location of skeletal muscle?
Attached to bones or, for some facial muscles to skin
What is the cell shape and appearance of skeletal muscle?
Single, very long, cylindrical, multinucleate cells with very obvious striations
Where is the body location of cardiac muscle?
Walls of the heart
Where is the body location of smooth muscle?
Mostly in walls of hollow visceral organs (other than the heart)
What is the cell shape and appearance of cardiac muscle?
Branching chains of cells; uninucleate, striations; intercalated disks
What is the cell shape and appearance of smooth muscle?
Single, fusiform, uninucleate; no striations
Is the innervation of smooth muscle involuntary?
Yes, autonomic innervation
Is the innervation of smooth muscle stimulatory or inhibitory?
It is dual, both stimulatory and inhibitory
Is the smooth muscle innervation graded?
Yes it is graded and spreading and continuous contraction
Describe multi-units of smooth muscle:
Each cell is innervated with variable force for example in the airways, and large arteries
Describe single-units of smooth muscle:
Very few cells are innervated. There is synchronous contraction which is myogenic. For example in the gut and uterus
Smooth muscle is located in the organs of….
Cardiovascular system (vessel walls), respiratory system, digestive system, urinary system, reproductive system and inside the eyes
What are the function and features of smooth muscle?
Little/weak contractile apparatus, long, slender, spindle shaped cells with single central nucleus and is nonstriated
What is the speed of contraction of skeletal muscle?
Slow to fast
What is the regulation of contraction in skeletal muscle?
Voluntary via nervous system controls
What is the regulation of contraction in cardiac muscle?
Involuntary, the heart has a pacemaker and also nervous system controls and hormones
What is the speed contraction of cardiac muscle?
slow
What is the regulation of contraction in smooth muscle?
Involuntary with nervous system controls, hormones, chemicals, stretch
What is the speed of contraction like in smooth muscle?
Very slow
What are the connective tissue components of skeletal muscle?
Epimysium, perimysium and endomysium
What are the connective tissue components of smooth muscle?
Endomysium
What are the connective tissue components of cardiac muscle?
Endomysium attached to the fibrous skeleton of the heart
