Anatomy - muscular system Flashcards
how many muscles are there int he human body
about 600
how are muscles classified
Skeletal
Cardiac
Smooth
What do muscles do
They convert energy ATP into mechanical energy (movement)
What are the four functions of the muscular system
Movement
Stability
Control of body opening and passages
Heat production
1st Muscular system function
Movement - muscles enable us to move from place to place and to move individual parts of our bodies.
Muscular contractions also serve to move body contents in the course of breathing, blood circulation, feeding and digestion, defecation, urination, and childbirth. Also serves roles in communication: speech, writing, facial expressions.
2nd Muscular system function
Stability - muscles maintain posture by preventing unwanted movements. Some are called antigravity muscles because they resists the pull of gravity. Many also stabilise the joints by maintaining tension in tendons and bones.
3rd Muscular system function
Control of body openings and passages - Muscles encircling mouth serve in food intake and retention while chewing. Muscles in eyelid and pupil regulate the admission of light. Internal muscular rings control the movement of food, vile, blood. Muscles encircling the urethra and anus control the elimination of waste.
(Some of these muscles are called sphincters)
4th Muscular system function
Heat production - Skeletal muscles produce 85% of the body heat (vital for the functioning of enzymes and metabolism)
What are the tissue components of muscles
Muscle fibre Muscle fascicle Endomysium Perimysium Epimysium Fascia
What is a muscle fibre
muscle cell
What is a muscle fascicle
bundle of muscle fibres
What is the endomysium
Connective tissue that surrounds each fibre and carries capillaries/nerves and chemical exchange during excitation.
What is the perimysium
Connective tissue that surrounds each fascicle and carries larger blood vessels and nerves and stretch receptors.
Epimysium
Fibrous sheath around entire muscle
Fascia
connective tissue that surrounds and separates muscle
What are the 7 types of muscle
Fusiform Parallel Triangular Unipennate Bipennate Multipennate Circular
Example of fusiform
Biceps brachii
Example of parallel
Rectus abdominis
Example of Triangular
Pectoralis major
Example of Unipennate
Palmar interosseous
Example of Bipennate
Rectus femoris
Example of Multipennate
Deltoid
Example of Circular muscle
Orbicularis oculi
How are muscles attached to bone
Skeletal muscles are attached to bone through extensions of their connective tissue.
This can be directly or indirectly.
Indirect
There is a large gap between muscle and bone bridge: a tendon, aponeurosis or retinaculum.
What is a tendon
collagen fibres of a muscle that continue into the periosteum and matrix of the bone
What is an aponeurosis
a broad sheet of tendon
What is a retinaculum
a band that serves as a guide for tendon, e.g. flexors
Direct
There are just short collagen fibres between muscle and bone
Origin of a muscle
bony site of attachment at the relatively stationery end of a muscle
Insertion of a muscle
bony site of attachment at the more mobile end of a muscle
What is the relation between the origin and the insertion of a muscle
They can be reversed depending on how the muscle functions during a particular movement
What is innervation
the identity of the nerve that stimulates the muscle
What two kind of nerves interact with muscle
Spinal nerves - referred by adjacent vertebra e.g. T2
Cranial nerves - referred to as Roman numerals e.g. ENX
What is the action
the mechanical effect of a muslce
What are the functional groups of muscles
Prime mover
Synergist
Antagonist
Fixator
Which is the prime mover
The muscle that produces the majority of the force during a movement.
e.g. brachialis during elbow flexion
Which is the Synergist
The muscle that provides and aid to the prime mover by adding force and stability.
e.g. biceps brachii during elbow flexion
Which is the antagonist
The muscle that opposes the prime mover, it completely relaxes or maintains some tension to control movement
e.g. triceps brachii for elbow flexion
Which is the Fixator
The muscle that prevents a bone from moving
e.g. rhomboids during movement of radius
What are the components of a lever system
Resistance
Fulcrum
Effort
Which are the first class lever systems
The ones with the fulcrum in the center with resistance and effort on the outside
What is an example of first class lever system in the body
the anatomical disposition while NODDING
Which are the seconds class lever systems
The ones with the resistance at the centre
What is an example of second class lever system in the body
Opening the mouth
Which are the third class lever systems
The ones with the effort at the centre
What is an example of third class lever system in the body
Elbow flexion
Which is the most common class of lever system in the body
effort in the middle - third class
What is the mechanical advantage
The ratio between the length of the effort arm and the resistance arm.
What are the particularities of a less than one MA
Low power and high precision
movement
What are the particularities of a higher than one MA
High power and low precision
Force
Why is skeletal muscle striated
because of the arrangement of the contractile proteins
What size are myofibres
100 - 500 nu meters thik and 3 - 30 cm long
Why are myofibres poly nucleated
Because they are made by the fusion of multiple myoblasts, they are derived from myoblast.
What organelle is very common in myofibres and why
The mitochondria, because muscle contraction uses ATP
What is the Sarcoplasmic reticulum
The muscle’s variation of an endoplasmic reticulum
What is a Sarcolema
The plasma membrane of the myofibre
What is the Sarcoplasm
The cytoplasm of the muscle cell
What are Myofilaments
Fibrous proteins that make up the contractile element of the muscle fibre
What are the three categories of myofilaments
Thick filaments
Thin filaments
Elastic filaments
Thick filaments
they are 15nm in diameter and are made up of myosin proteins.
(los moraditos con cabeza y cola que se envuelven en helice)
Thin filaments
they are 7nm in diameter and are made out of Fibrous F actin, tropomyosin and troponin.
When troponin binds with calcium the tropomyosin rotates, revealing the binding sites for myosin.
F actin
made of globular G actin, each has a binding site for a myosin head
tropomyosin
placed on top of F actin blocking the myosin binding sites
troponin
placed at regular intervals on the tropomyosin and capable of binding with calcium
Elastic filaments
they are 1nm in diameter, they help muscle return to their normal uncontracted shape
Titin protein
Which are the contractile proteins
myosin and titin
What happens to myofilaments when muscle contraction happens
The thick filaments slide into the thin filaments
Why are linking proteins important
The sliding movement of the thin and thick protein needs to be transduced into the sacolema and posteriorily to the connective tissue (endomysium), to the perimysium, to the epimysium, to the fascia and then to however the fascia connects to the target (tendon).
Which are the linking proteins
dystrophin and linking proteins
What is a motor unit
A motor unit consists of one nerve and all myofibres innervated by it.
If a neuron activates few muscle fibres…
we get fine control
e.g. eye muscle
If a neuron activates many muscle fibres…
we get gross control
e.g. muscles in thigh
What is another name of a motor and plate
synapse
What is a motor and plate
the interface between the neuron and it’s target cell, it includes part belonging to the neuron and part belonging to the cell.
What is the name for the synapse of the muscle cells
Neuromuscular junction
What happens at the neuromuscular synapse
When an electrical signal reaches the synaptic knob, it causes the opening of calcium channels in the membrane of the synaptic knob, which triggers the exocytosis of the synaptic vesicles.
This synaptic vesicles contain the neurotransmitter acetylecholine and the fusion of the vesicles with the pre-synaptic membrane will lead to the acetylecholine entering to the space between the synaptic knob and postsynaptic membrane, the synaptic cleft.
The neurotransmitter will impinge on receptors present in the postsynaptic membrane, this membrane has many folds to increase the surface area and allow the muscle fibre to be highly responsive to the acetylecholine.
Which is the neurotransmitter of the neuromuscular junction
acetylecholine
What kind of receptor is the Acetyle receptor
The acetylecholine receptor is a ligand-gated ion channel. This means that when a ligand binds to it, it will open and allow particular ions to cross the sarcolemma.
Which ions are the ones that activate the acetylecholine receptors and how do they work
sodium ions, a negative voltage difference between the inside and the outside rises when the sodium ions enter. (transmembrane voltage)
What is the increase in the transmembrane voltage called
depolarisation
What is the action potential
a sequence of events that take place when enough depolarisation happens, it is mediated by voltage-gated ion channels of sodium and potassium channel, which cause an electrical event.
What happens when a muscle fibre is activated
The action potential occurs, the action potential propagates into the muscle fibre via the T-tubules into the sarcolema, which allows a very rapid depolarization or activation of the entire muscle fibre. The action potential traveling along the T-tubules causes calcium ions in the sarcoplasmic reticulum to be released to the area surrounding the myoibrils and myofilaments.
Mechanical contraction
Once calcium is present around the myofilaments, it binds to troponin, causing the tropomyosin to change shape, revealing the binding sites of the F-actin for the myosin heads.
The myosin head is able to bind ATP when this happens it is hydrolysed, releasing ADP, phosphate and energy.
That energy is used to change the shape of the myosin head (this movement is called cocking).
Once it is cocked it binds with the binding site of the F-actin. When it binds, it releases ADP and phosphate and return to its low energy or uncork state. THis causes the sliding of the thin filament relative to the thick filament. This process repeats to coninue the sliding for as long as calcium is present.
What is the order of mechanical contracion
Binding of new ATP, breaking of cross-bridge
Hydrolysis of ATP to ADP, activation and cocking of myosin head.
Formation of myosin-actin cross-brige
Power stroke, sliding of thin filament over thick filament
Muscle relaxation
Once the electrical signal has stopped, the whole muscle contraction process will stop.
The acetylcholine in the synaptic cleft is quickly removed by enzymes degradation which destroy the chemical and degradation products return to the synaptic knob.
With no electrical signal present in the T-tubules, the sarcoplasmic reticulum will no longer be releasing calcium ions but taking them up instead, to store them again.
This causes calcium to unbind from troponin and make tropomyosin return to its ground shape, covering the binding sites on the F-actin.
The cycle is broken and muscle contraction begins.
