Structure And Function Flashcards
What is a myocyte?
A muscle fibre which which is a cell and makes up muscle.
What’s is the function of the muscular system?
Movement -muscular contraction and moving the bones, joints and muscles.
Posture - stabilising joints and balance
Heat production via thermogenesis. Shivering by muscular contractions
Glycogen store
Movement of substances such as sphincters, blood vessels, skeletal system, movement of food.
What does contractility mean?
The ability of muscles to contract or shorten
What does excitability mean?
The ability to generate an electrical current through action potentials.
What does extensibility mean?
Ability to stretch muscles without being damaged
What is elasticity?
The ability for something to return to its original length and shape after extension.
What are the three types of muscles?
Cardiac, smooth and skeletal
What does striated mean?
Cell aligned in parallel bundles so stripes are visible with a microscope
What does non striated mean?
Randomly arranged cell with no stripes visible.
What is skeletal muscle?
Voluntary movement which are striated and multi nucleated. Can not do mitosis but develop by hypertrophy.
What is cardiac muscle?
Involuntary heart muscle which is striated and single nucleus in the cells. It is intercalated discs - fibres that mean contraction can spread like a wave. More and larger mitochondria which mainly use aerobic respiration.
What does auto-rhythmic mean?
Contractions without nervous stimulation
What is smooth muscle?
Involuntary, form the walls of hollow organs and blood vessel. Single nucleus and non striated. Filaments attach to structures called dense bodies which are pulled closer when muscle shortens.
How are myocytes formed?
Embryonic fusion of myoblasts so each muscle skeletal fibre has many nuclei.
Hypertrophy
Enlargement of existing fibres
Atrophy
Wasting of muscles
Fascia
Connective tissue that organises muscle, secures it to skin and provides stability.
What is the skeletal muscle hierarchy?
Muscle is made of muscle fibre bundles which is made of muscle fibre which is made up of myofibrils. Myofibrils are made of myofilaments.
Sarcolemma
Plasma membrane of muscle cell
Transverse tubules
Tubes extending from sarcolemma into muscle cell
Sarcoplasm
Muscle cell cytoplasm
Sarcoplasmic reticulum
Tubular network that circulates cytoplasm and store terminal cisterns
Terminal cisterns
Store calcium and attach on the SR.
Myoglobin
Red coloured oxygen binding proteins in sarcoplasm
What are myofilaments?
Made up of actin (thin) and myosin (thick) which overlap to form sarcomeres.
A bands - dark area where myofilaments over lap
I bands - light area with only actin filaments.
What is epismyosium?
Wrapped around entire muscle.
What is perimyosium?
Surround groups or bundles of 10-100 muscle fibres forming fascicles
What is endomyosium?
Thing sheath around individual muscles.
Explain how a neuromuscular junctions works.
Action potential travels down the moron neuron. This causes Ca to be to enter the axon terminal. Ca causes ACh to be release by exocytosis. ACh diffuses across the synapse and binds to receptors on sarcolemma. ACh binds to sodium potassium pump receptors cause them to open. Na enter the muscle cell and k leave muscles cell cause end plate potential.
When ACh is broken down by acetylcholinesterase this ends the end plate potential.
Explain sliding filament theory
Action potential arrives as neuromuscular junctions.
Action potential spreads along sarcolemma and t tubules. Muscle cell releases Ca from storage (SR reticulum).
Ca and adenosine triphosohate (ATP) trigger myosin to bind to actin so filament slide over each other and this shortens the fibre.
What are the thee ways muscle fibres make ATP?
Creatine phosphate, aerobic and anaerobic respiration
What is creatine phosphate?
Store excess ATP as creatine phosphate. During muscle contraction ATP is used up so creatine phosphate is used to regenerate ATP to make contraction longer or more sustained
Occupitofrontalis
Raises eyebrows
What’s is the function of orbicularis oculi?
Closes eyes
What’s the function of orbicularis pro?
Closes or pouts lips
Masseter
Elevates and protrudes mandible/closes jaw for chewing
What is the temporalis?
For chewing
What is sternocleidomastoid?
Tilting your head and rotating your head
What is trapezium?
Pulls head backward, elevates, retracts and depressed shoulders
What is supraspinatus?
Initial abduction of shoulder
What is psoas?
Hip flexor: pull thigh towards trunk.
What is latissimus dorsi?
extends, adducts and medially/internally rotates arms.
What is quadrates lumborum?
bending backwards and sideways
What is erector spine?
extension of vertebral volume, keep spine upright
Pectoralis major
draws arms forward, shoulder flexion and adduction, medial rotation
rectus abdominis
vertebrae flexion: bending forward
transverse abdominis
compresses abdominal organs
internal and external obliques
rotation, bending sideways
deltoid
flexion, abduction and extension of shoulder joint.
bicep branchii
stabilizes shoulder joint, flexion and supination of forearm
tricep branchii
arm adduction and extends elbow
flexor carpi ulnaris
flexes the hand at the wrist joint
extensor carpi radialis
extend the hand at the wrist joint
gluteus maximum
external rotation, abduction and extension of the hip joint
gluteus medius
abducts leg, stabilises pelvis
hamstring
bend knee
rectus femoris
flexes hip, extends knee
thigh adductors
squeezes thighs together
tibialis anterior
dorsiflexion and inversion of foot
soleus
plantar flexion of food at ankle, stabilises ankle
gastrocnemius
flexes leg at the knee, plantar flexion of food
What are the two smooth muscle types?
visceral/single unit and multi unit.
What is a visceral/single unit of smooth muscle?
lines vessels and hollow viscera, auto-rhythmic, one stimulus causes contraction of many fibres together as a single unit.
What is a multi unit of smooth muscle?
in large arteries and airways, iris and ciliary body. Fibres are stimulated individually and operate independently.
What are the properties of smooth muscle?
slower and longer contractions, shorten and stretch more than skeletal muscle
