A&P Muscle Anatomy & Muscle Physiology w/ 3 Short Answers Associated

List the functions of the muscular system.

Movement, posture, joint stability, heat production (shivering/contract)

Identify the three different types of muscles there are, where they are found, and their functions.

Skeletal (atched to bones; voluntary movement, posture, heat) /// Cardiac (heart walls; involuntary pumping of blood) /// Smooth (Walls of hollow organs; involuntary control of digestion, blood flow etc)

Describe the microscopic similarities and differences between the three muscle types.

Skeletal: Striations, Multinucleated, Voluntary, No intercalated discs, long cylindrical cell shape

Cardiac: Striations, one (sometimes two) nuclei, involuntary, has intercalated discs, branched cell shape

Smooth: No striations, one nuclei, involuntary, no intercalated discs, spindle-shaped cells

Be able to diagram and describe the gross anatomical arrangement of skeletal muscle from whole muscle down to muscle fiber, including coverings.

Muscle is covered by epimysium, contains fasicles, fasicles are bundles of muscle fibers covered by perimysium, muscle fibers (cell) are surrounded by endomysium.

Be able to diagram and describe the micro-anatomical arrangement of skeletal muscle from sarcolemma to the components that make up the sarcomere.

Muscle fiber: cell membrane = sarcolemma.

Cytoplasm = sarcoplasm, contains myofibrils

Myofibrils contain repeating units = sarcomeres (contractile unit)

Sarcomeres contain thick filaments (myosin) and thin filaments (actin)

Explain why the actin and myosin proteins are arranged as they are in the sarcomere and how their arrangement relate to contraction.

Myosin (thick) pulls on actin (thin) during contraction. They’re organized in overlapping pattern which = striations. Pulling at the actin inward shortens the sarcomere = muscle contraction.

Explain the role of tropomyosin and troponin on actin filaments.

Tropomyosin: Covers actin’s binding sites at rest

Troponin: Binds to calcium, moves tropomyosin, exposes actin binding sites so myosin can bind = contraction begins

Be able to identify major muscles and muscle groups on a diagram

Deltoid, biceps brachii, triceps brachii, pectoralis major, latissimus dorsi, rectus absominis, obliques, quadriceps, hamstrings, gluteus maximus, gastrocnemius, tibialis

Diagram and describe the structure of the sarcomere.

Bound by z -discs. Contain:

A band: Length of myosin

I band: Actin only

H zone: Myosin only (no actin)

M line: Center of sacromere

Describe the process of neuronal excitation to the level of detail discussed in lecture.

Motor neuron releases acetrylcholine (Ach) at the neuromuscular junction

AcH binds receptors, opens Na+ channels, depolarizes sarcolemma

Describe the process of excitation-contraction coupling to the level of detail discussed in lecture.

T-tubules stimulate sarcoplasmic reticulum (SR) to release Ca2+

Ca2+ binds troponin, shifts tropomyosin, expses actin binding sites

Myosin heads bind, contraction begins

Describe the process of sliding filament theory to the level of detail discussed in lecture.

Myosin heads attach to actin, perform power stroke

Actin slides over myosin, sarcomere shortens

Atp is required for detachment and resetting of myosin head

Explain the role of calcium has in the process of muscle contraction.

Ca2+ binds to troponin

Enables actin-myosin interaction

When Ca²⁺ is removed (pumped back into SR), muscle relaxes

Explain why ATP is required to complete a muscle contraction at the level of the sarcomere.

It allows myosin to detahc from actin, myosin heads to reset, and the active pumping of Ca2+ back into sarcoplasmic reticulm (SR)

Describe the process of how muscles relax to the level of detail discussed in lecture.

ACh is broken down by acetylcholinesterase. Ca2+ pumped back into SR. Troponin/tropomyosi block actin. Cross-bridges detach, muscle returns to rest length.

Define and explain the following terms: a. Twitch b. Summation c. Incomplete tetanus d. Complete tetanus e. Treppe

Twitch: Single contraction from one stimulus

Summation: Repeated stimuli before full relaxation = stronger contraction

Imcomplete tetanus: Rapid stimuli, partial relaxing

Complete tetanus: No relaxation, smooth sustained contraction

Treppe: Step-wise increase in contraction strength due to warming up

Describe the types of muscle contractions listed below: a. Isotonic contraction i. Concentric contraction ii. Eccentric contraction b. Isometric contraction

Isotonic: Muscle length changes

Concentric: Shortening

Eccentric: Lengthening

Isometric; Muscle cotracts but doesn’t change length

Graph and explain the length-tension relationship in a contracting muscle.

Optimal sarcomere length = maximum cross-bridge overlap = strongest contraction

Too short or too stretched = reduced force

What is the lactate threshold or lactic acid threshold?

The point where lactic acid accumulates faster than it can be cleared.

Sign of shift to aanerobic metabolism

What is the relationship between the lactate threshold and the rate of ATP production?

Below threshold: aerobic atp production

above threshold: anaerobic glycolysis, less efficient, builds lactate

What role does phosphocreatine play in muscle metabolism?

Rapid regeneration of atp, transfers phosphate to ADP → ATP

Used in first 10-15 sec of intense activity

Compare and contrast the Type I, Type IIX, and Type IIA muscle fibers.

Type 1 (Slow-twitch): Slow, fatique resistant, high mitochrondia, low power, red color, endurance

Type IIA (Fast oxidative): Fast, moderate fatigue, medium mitochondria, medium power, pink color, mixed endur/explosive

Type IIX (Fast glycolytic): Very fast, fast fatigue, low mitochrondia, high power, white color, explosive

(Short Answer) Describe the Neuronal Excitation phase of muscle contraction. This phase includes how a signal arriving at the axon terminal results in calcium ions being released from the sarcoplasmic reticulum.

Motor neutron AP reaches axon terminal, opens voltage gated Ca2+ channels so Ca2+ ca enter.

Ca2+ triggers ACh release into synaptic cleft

ACh binds nicotinic receptors on sarcolemma, Na+ influx, end-plate potential, muscle AP.

(Short Answer) Describe the Neuronal Excitation – Contraction Coupling phase of muscle contraction. This phase includes the release of calcium ions from the sarcoplasmic reticulum until the binding of the myosin heads to the actin filaments.

Muscle AP travels down T-tubules, DHP receptors change shape, ope RyR channels on SR.

Ca2+ floods from SR ito sarcoplasm. Ca2+ binds troponin, tropomyosi shifts off actin’s binding sites → myosin heads can attach.

(Short Answer) Describe the Sliding Filament Theory phase of muscle contraction. This phase includes the repeated binding, power stroke, and unbinding of the myosin heads from the actin filaments.

Cross bridge formation: cocked myosin head binds actin

Power stroke: Pi release triggers head pivot → pulls actin inward → ADP leaves.

Detachment: ATP binds mysoin → head releases actin

Re-cocking: ATP hydrolysis (to ADP+Pi) re-energizes myosin head

Cycle repeats while Ca2+ and ATP are available