Muscle And Nerve Flashcards
What is muscle ?
It is a tissue specialised for contraction
What are the functions of muscles ?
- force generation
- movement
- posture
- heat generation
- control of diameter of tubes
- heart beat
What are the 2 types of muscle ?
- striated muscle
- smooth muscle
What are the 2 types of striated muscle ?
- cardiac muscle
- skeletal muscle
Where is smooth muscle found ?
It is widespread
Found in the viscera, blood vessels, skin and eye
What is a fasicle ?
A bundle of muscle fibres
What is endomysium ?
Connective tissue found around muscle fibres
What is perimysium ?
Connective tissue which wraps around bundles of muscle fibres
What is epimysium ?
Connective tissue which wraps around the whole muscle (around the perimysium)
What are muscle fibres ?
They are very large and multinucleate cells
- may extend from 1 end of a muscle to the other
What is the basal lamina ?
It is an extracellular matrix layer made by muscle fibres and it blends into the endomysium
All muscle cells are surrounded by a basal lamina
What is a satellite cell ?
It is a muscle stem cell which is positioned against a muscle fibre membrane under the basal lamina
Why is striated muscle striated ?
The contractile units are organised and in alignment with each other
What is a sarcomere ?
It is a unit of contraction within a muscle fibre
What is a myofibril ?
A collection of sarcomeres
What happens when a muscle contracts ?
The sarcomere shortens and the actin filaments slide in between the myosin filaments
What is the cytoplasm of a muscle cell known as ?
Sarcoplasm
Describe the structure of the sarcoplasm
- contains many mitochondria
- contains a lot of glycogen
- contains myoglobin
- has a highly specialised endoplasmic reticulum
- contains many myofibrils
What is a sarcoplasmic reticulum ?
A highly specialised endoplasmic reticulum
What is a muscle plasma membrane known as ?
Sarcolemma
Is cardiac muscle voluntary or involuntary ?
It is an involuntary muscle
Describe the structure of cardiac muscle
- striated
- very different fibre structure from skeletal muscle
- branched fibres and the spaces are filled with connective tissue
- no epimysium or perimysium
How do heart muscle fibres link together ?
The cells contain 1 or 2 centrally located nuclei and are linked end to end via intercalated discs
Why can heart muscle not be repaired ?
Heart muscle doesn’t contain any satellite cells and so damaged heart muscle dies and is replaced with scarred connective tissue
Describe the structure of smooth muscle
- long and thin spindle shaped fibres
- fibres are linked by desmosomes, adherens junctions and gap junctions
- not striated because the myofibrils are not parallel and in alignment
Describe the innervation of smooth muscle
- most smooth muscle is poorly innervated
- contractile signals spread from cell to cell via gap junctions
How is smooth muscle repaired ?
Smooth muscle cells can divide and enlarge allowing generation of new smooth muscle so it can be repaired
What is a peripheral nerve ?
Carries large numbers of axons
Describe the structure of peripheral nerves
- structurally similar to skeletal muscle
- epineurium, perineurium and endoneurium protects the nerve fibres
What is epineurium made from ?
Collagen and fat
What is perineurium made from ?
Dense collagenous layer
Describe the properties of endoneurium
It is delicate and highly vascular
What is the function of the smooth muscle in the small intestine ?
Allows for peristalsis so the gut contents can be moved along
What are the general features of the skeletal muscle connective tissues ?
- allows for voluntary movement
- harness for muscle contraction force
- allows blood vessels and nerves in and out of the muscle at all levels
What is the major difference in the cellular organisation of heart muscle and skeletal muscle fibres ?
- in heart muscle, the individual muscle fibres are linked end to end
- in skeletal muscle, there is a fusion of thousands of cells to make multinucleate fibres
What is the function of the connective tissue in a peripheral nerve ?
Protects the nerve and is also important in nerve regeneration
