Muscular system Flashcards
(32 cards)
1
Q
Types of Muscles
A
- Smooth Involuntary muscle; controlled by the autonomic nervous system
1) Located in the walls of blood vessels and throughout internal organs - Cardiac Controlled by the autonomic nervous and endocrine systems
1) Located only in the heart - Skeletal Voluntary muscle; controlled consciously by the somatic nervous system
1) More than 600 different skeletal muscles located throughout the body
2
Q
Functions of the Muscular System?
A
- Movement of the body
- Maintenance of posture
- Respiration
- Production of body heat
- Communication
- Constriction of organs and vessels (Smooth muscle)
- Contraction of the heart (Cardiac muscle)
3
Q
The Basic Structure of Skeletal Muscle
A
Tendon:
- Attaches to the muscle providing anchorage for
attachment to skeletal system
- Provide stability but also have elastic properties that allow for force generation
Muscle Belly:
- Recognisable region of
muscle where fibres are
located
- Epimysium (within the muscle) is fibrous tissue envelope that surrounds
skeletal muscle - Perimysium is a
sheath of connective
tissue that groups
muscle fibres into
bundles (10-100) called
fascicles - Endomysium
(within the muscle), is
connective tissue that
ensheaths each
individual myocyte
(muscle fibre, or
muscle cell)
4
Q
Parts of a Muscle
A
- Myofibrils = bundles of protein filaments; contain the protein filaments
(myofilaments) that cause contraction - Myofilaments - Actin (thin) myofilaments
- Myosin (thick) myofilaments
- Myofilaments arranged into orderly units called
sarcomeres - Sarcomere = basic functional unit of muscle fiber; smallest part that can contract
- Sarcolemma = plasma membrane; surrounds sarcoplasm (cytoplasm) and other contents of cell
- Transverse tubules (T tubules) = inward folds of sarcolemma; project into interior of muscle cell
- Sarcoplasmic reticulum (SR) = specialized smooth endoplasmic reticulum; stores calcium
5
Q
Sarcomeres
A
Regions of sarcomere:
1) A bands: central dark-staining region; overlapping actin and myosin myofilaments (except at center).
2) I bands: lighter-staining regions, each containing a Z disk and extend to ends
of myosin myofilaments
3) H zone: region in A band where actin and myosin do not overlap.
4) M line: middle of H zone; delicate filaments holding myosin in place
- In muscle fibers, A and I bands of parallel myofibrils are aligned and so produce
striated appearance
6
Q
How do we describe where parts of the body are in relation to each other?
A
Is the hand below the elbow?
What if you raise your arm?
The hand is distal to the elbow
Distal = further from the trunk
7
Q
What is the anatomical reference position?
A
- The basic anatomical
position that health &
medical professionals
use when describing
the human body:
1) Standing erect, facing
forwards
2) Legs together with the
feet parallel, so that the
toes point forwards
3) Arms hang loosely by
the sides with the palm
of the hand facing
forward - Why do we need an
‘anatomical position’?:
1) Considered the starting
point for all body segment
movements
2) Allows clear description of
position of body parts
relative to each other
3) Most movements are
described in their relation
to the anatomical position
8
Q
Alternatives to upright
A
Terms for a reclining (recumbent i.e.
laying down) body:
1) Prone position
2) Body is lying face down
3) Supine position
4) Body is lying face up
9
Q
Directional Terms
A
- Anterior (Ventral) vs. Posterior (Dorsal). Anterior is forward; posterior is toward the back
- Superior (Cephalic) vs. Inferior (Caudal) toward or away from the head
- Medial vs. Lateral relative to the midline (closer or further from midline)
- Proximal vs. Distal used to describe linear structures (nearer or further to the attachment of a limb to the trunk)
- Superficial vs. Deep relative to the surface of the body (external or internal)
10
Q
Reference planes
A
- Human movement occurs:
1) in a plane
2) around an axis - What is a plane?
1) ‘An imaginary flat surface that passes through the body’
2) Akin to a perpendicular ‘cross-section’ - What is an axis?
1) ‘A straight line around which an object rotates’ - Most planes are perpendicular, except Oblique planes
1) Passes through the body or an organ at an angle
11
Q
There are 3 planes of the body
A
Frontal plane:
- side-to-side (lateral) movements
Horizontal (transverse) plane
- rotational movements
Sagittal (median) plane
- forward and backward
movements
12
Q
Location terms
A
- Superficial: closer to the
surface of the body or skin - Deep: inside the body and away from the surface or skin
- Dorsum: of the foot/hand
- Plantar: surface of the foot
- Palmar: surface of the hand
- Cephalic: towards the head
13
Q
Less common locational terms
A
- Dorsum/Dorsal: upper side of animals/backside of humans to the back of the body
- Contralateral: the other or opposite side
- Ipsilateral: on the same side
- Ventrum/Ventral: meaning ‘belly’ - pertaining to the front of the body
14
Q
Anatomical terms of movement
A
- Right and left (C)
-Flexion and Extension (S) - Abduction and Adduction (C)
- Rotation (H)
- Elevation and Depression (C)
- Pronation and Supination (H)
- Inversion and Eversion (C)
- Dorsiflexion and Plantar Flexion (S)
- Circumduction (S) (C)
Coronal (frontal) plane
Sagittal (median) plane
Horizontal (transverse) plane
15
Q
Flexion - Extension
A
- Flexion + decreases angle of the joint
- Extension = increases angle of the joint
- Hyperextension = increasing angle of the joint beyond 180
16
Q
Lateral flexion
A
- Bending at the waist to one side
17
Q
Dorsiflexion – Plantar Flexion
A
- Plantar flexion = movement of the foot towards plantar surface
- Dorsiflexion = movement of foot towards the shin
18
Q
Abduction – Adduction
A
- Abduction = movement away from the midline
- Adduction = movement towards the midline
19
Q
Elevation and Depression
A
- Elevation = moving a structure superiorly
- Depression = moving a structure inferiorly
20
Q
Rotation
A
- Turning of a structure around it’s axis
- Medial (internal) = rotation towards the axis of the body
- Lateral (external rotation) rotation away from the axis of the body
21
Q
Pronation – Supination;
Inversion - Eversion
A
- Pronation – rotation of forearm to face palms posteriorly (from
anatomical position) - Supination = rotation of
forearm to face palms
anteriorly (from anatomical position) - Inversion = turning the ankle so that the plantar surface of the foot faces medially
- Eversion = turning the ankle so that the plantar surface of the foot faces laterally
22
Q
Circumduction
A
- Combination of flexion, extension, abduction and adduction
- Occurs at freely moveable joints
23
Q
Others
A
- Protraction and Retraction
- Lateral excursion and Medial excursion
- Opposition and Reposition
24
Q
Sliding Filament Model
A
- Actin myofilaments sliding over myosin to shorten sarcomeres
- During relaxation, sarcomeres lengthen because of some external force, like contraction of antagonistic muscles
25
Sarcomere Shortening
- In a relaxed muscle, the actin and myosin myofilaments overlap
slightly, and the H zone is visible. The sarcomere length is at its normal resting length
- As a muscle contraction is
initiated, actin myofilaments slide
past the myosin myofilaments, the z disks are brought closer together, and the sarcomere begins to shorten
- In a contracted muscle, the A bands do not narrow because the length of the myosin myofilaments does
not change
- The ends of the actin
myofilaments are pulled to and overlap in the center of the sarcomere, shortening it and the H zone disappears
26
Excitation-Contraction Coupling
- Nervous system controls
muscle contractions through action potentials at Motor Units
- Phrase used to describe
links between electrical and mechanical components of contraction
27
Motor Units
Motor units: a single
motor neuron and all muscle fibers innervated by it
28
Neuromuscular Junction Structure
- Motor neurons carry electrical signals called action potentials, which stimulate muscle fiber action potentials followed by muscle contraction
- Points of contact between motor neuron and muscle fiber is the neuromuscular junction, or synapse. This consists of:
1) Presynaptic terminal
2) Synaptic cleft
3) Postsynaptic membrane or motor end-plate
29
Function of the Neuromuscular Junction
1) Action potential reaches the presynaptic terminal, opening voltage-gated Ca²⁺ channels.
2) Ca²⁺ enters and triggers ACh release from synaptic vesicles.
3) ACh is released into the synaptic cleft via exocytosis.
4) ACh binds to ligand-gated Na⁺ channels on the postsynaptic membrane.
5) Na⁺ enters, depolarizing the membrane; if threshold is reached, a new action potential is generated.
6) ACh unbinds, and Na⁺ channels close.
7) Acetylcholinesterase breaks down ACh into acetic acid and choline.
8) Choline is reabsorbed with Na⁺ into the presynaptic terminal.
9) ACh is resynthesized and stored in vesicles.
30
Resting membrane potentials
- Membrane voltage
difference across
membranes (polarized)
1) inside: more negative due to large proteins and high K⁺.
2) K⁺ leaks out, but negative proteins hold some back.
3) Outside: more positive with more Na⁺.
4) Na⁺/K⁺ pump maintains this balance.
- Must exist for action
potential to occur
31
Action Potentials
- Phases:
1) Depolarization: Inside becomes less negative; if threshold is reached, it triggers an action potential
2) Repolarization: Membrane returns to resting state, briefly dips below normal, then stabilizes via the Na⁺/K⁺ pump
- All-or-none principle: like camera flash system
- Propagate: Spread from one location to another. Action potential does not move along the membrane
- Frequency: number of action potential produced
per unit of time
32
Action Potentials (AP) and Muscle Contraction
- An action potential is propagated along the sarcolemma and T tubules
- Depolarization of the T tubule causes gated Ca2+ channels in the sarcoplasmic reticulum to open
- Calcium ions bind to troponin molecules. The troponin molecules bound to G actin molecules are released, causing tropomyosin to move
- Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind to them to form cross-bridges
