Study guides › B/B › Biology
Muscle, Skeleton & Skin
Muscle moves the body, bone supports it, and skin protects it. You will learn the three muscle types, the sliding filament model, the neuromuscular junction, bone remodeling and calcium control, joints, and skin layers with thermoregulation.
Study this chapter in PrepMed (free)
What this chapter covers
- Muscle Types & Energy Use. The MCAT loves comparing skeletal, cardiac, and smooth muscle, and asking how muscle makes ATP during exercise.
- The Sarcomere & Sliding Filament Model. Which sarcomere bands shrink and which stay constant is one of the most tested facts in muscle physiology.
- Neuromuscular Junction & Excitation-Contraction Coupling. From motor neuron action potential to Ca²⁺ release, every step is testable. Learn the order and the clinical failures.
- Bone, Cartilage & Joints. Bone is living tissue that constantly remodels, and its calcium is tied to hormones you must know.
- Skin & Thermoregulation. Skin is the body's largest organ. Layers and the heat-loss responses of dermal blood vessels appear regularly.
Key points to know
- Skeletal and cardiac are striated; smooth is not
- Smooth muscle uses calmodulin and MLCK instead of troponin
- Thick filaments = myosin (A band); thin filaments = actin (I band and part of A)
- During contraction: I band, H zone, sarcomere shorten; A band unchanged
- ACh at the NMJ binds nicotinic receptors (ligand-gated Na⁺ channels)
- T-tubules carry the action potential to the SR, which releases Ca²⁺
- Osteoblasts build, osteoclasts resorb, osteocytes maintain
- PTH raises blood Ca²⁺; calcitonin lowers it; vitamin D boosts gut absorption
Try a practice question
Which muscle type is striated, has one or two nuclei per cell, and has intercalated discs with gap junctions?
- Cardiac muscle
- Skeletal muscle
- Single-unit smooth muscle
- Multi-unit smooth muscle
Show the answer
A. Only cardiac muscle combines striations with intercalated discs. Skeletal fibers are multinucleate and lack gap junctions, and smooth muscle is not striated.
Common questions
What does this chapter cover?
Muscle, Skeleton & Skin covers Muscle Types & Energy Use, The Sarcomere & Sliding Filament Model, Neuromuscular Junction & Excitation-Contraction Coupling, Bone, Cartilage & Joints, Skin & Thermoregulation.
What should I know first?
Skeletal and cardiac are striated; smooth is not Smooth muscle uses calmodulin and MLCK instead of troponin Thick filaments = myosin (A band); thin filaments = actin (I band and part of A)
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.