Skeletal muscle and nerve Flashcards
3 types of muscle tissue
-Skeletal
-Cardiac
-Smooth
3 characteristics of muscles
-Voluntary vs Involuntary
-With striation vs Without striation
-Somatic (body wall and limbs) vs Visceral (organs)
Skeletal muscle features
-Voluntary somatic muscle
-Long, slender with peripheral nuclei
-Cross striations (actin and myosin filaments)
Cardiac muscle features
Similarities to skeletal muscles
-Show cross striations because of the myofilaments
Differences to skeletal muscles
-Intercalated discs (black arrows)
-Only 1 or 2 centrally located nuclei
-Branching
Smooth muscle features
-Non-striated
-Spindle shaped and small fibres
-Single elongated central nucleus
-Longitudinal: linear bundles
-Cross section: polygonal profiles
Tendon features
-Provide attachment sites - proximal and distal
-Usually tendons attach to bone, but can also attach to skin, fascia, other muscles
-Tendons can be found as a broad, flat, compressed aponeurosis (scalp and abdominal wall)
Muscle shapes
-Bipennate
-Unipennate
-Multipennate
-Fusiform
-Parallel
-Convergent
-Circular
Microarchitecture of muscle tissue
muscle > fascicles > muscle fibres > myofibrils
-Epimysium covers perimysium
-Perimysium covers fascicles
-Endomysium covers muscle fibres
-Sarcolemma covers myofibrils
Actin and myosin
Actin
-thin filament
-anchored to Z line
-Light staining I band
Myosin
-thick filament
-anchored to M line
-Dark staining A band
What is a sarcomere?
-Contractile functional unit
-From Z line to Z line
What happens during skeletal muscle contraction?
-Sarcomere shortens, myofilaments remain same length
-I bands (actin) shortens, A bands (myosin) remain same length
-H bands narrow - more overlapping as actin slides into myosin
3 types of muscle contraction
Reflexive contraction
-Regulated by ANS so not voluntary (e.g. diaphragm)
Tonic contraction
-Muscles of a conscious individual are always slightly contracted to maintain joint stability and posture
Phasic contraction
-Active muscle contractions producing movement or active resistance
Isotonic vs isometric muscle contraction
Isotonic
-muscle changes length in relation to production of movement (concentric/eccentric)
Isometric
-Muscle length remains the same (no movement)
-Muscle tension is increased above tonic levels to resist a force
Agonists vs Antagonists
Agonists (prime movers)
-Contract actively to produce a desired movement
Antagonists
-Oppose the action of the prime movers
-Relax whilst the prime mover contracts
What are synergists and fixators?
Synergist
-A muscle with a similar action to a prime mover
-Cancels out unwanted movements to increase efficiency of prime mover
Fixator
-Steadies proximal part of limb while movements are happening more distally
Structure of a neurone
Cell body - contains the nucleus and other organelles
Dendrites - processes branching from the cell body that transmit impulses toward the cell body
Axon (nerve fibre) - a long process extending from the cell body which carries information toward synapses
Types of neurone based on branching pattern
Multipolar - one axon and a number of dendrites from the cell body (most common)
Bipolar - Centrally placed cell body from which extend a single dendrite and a single axon (rare)
Pseudounipolar - a single process emerging from the cell body which divides into dendritic and axonal branches
Neuroglia
Relationship between motor neurones and skeletal muscle
1) Motor signals are carried by upper motor neurones (UMNs)
-These originate in the brain stem or motor cortex
-They affect the excitability and thus the output of LMNs
2) The UMNs synapse with LMS
-LMNs are found in the ventral horn in spinal cord grey matter
-Or the cranial nerve nuclei of the brain stem and cranial nerves
3) The LMNs leave the CNS and bring motor signals to the muscles
