MCAT Bio 5
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Integumentary system components
Hair, nails, skin, and oil and sweat glands.
Integumentary system functions
Thermoregulation, protection, environmental sensory input, excretion, innate immunity, blood reservoir, vitamin D synthesis.
Made of avascular, dead, keratinized cells.
Contains blood vessels, hair follicles, sebaceous glands (oil), sudoriferous glands (sweat), and nerve endings. The dermis is a connective tissue.
Musculoskeletal system functions
Body movement, support and stabilization, generation of heat, and maintenance of homeostasis.
Skeletal muscle characteristics
Voluntary, striated, and multinucleated.
Arrival of the Action Potential
The neuromuscular junction between a skeletal muscle and a motor nerve can ONLY USE ACETYLCHOLINE (ACh) AS THE NEUROTRANSMITTER. The action potential spreads along the sarcolemma and down specialized T-tubules that dive deep into the muscle cell, causing the release of Ca2+.
- -The default low-energy position for myosin heads is bent. ATP is used to force, or "cock", these myosin heads into a high-energy, straight position.
- -After the "power stroke", ATP binds to the mysoin head again, releasing it from the actin filament.
Ca2+ level for contraction
Ca2+ level for relaxation
Effect on sarcomere when no ATP is present
Myosin heads cannot detach from actin and the muscle will remain in a contracted position. (Rigor mortis)
Effect on sarcomere when no Ca2+ is present
We do not get rigor, but the inability to contract (a.k.a. "flaccidity")
The strength of a contraction depends on:
- 1) Number of motor units being used
- 2) Size of the motor units being used
- 3) Frequency of action potentials (i.e. stimulation)
Skeletal muscle important features
- Skeletal muscles store large amounts of glycogen; they also require a lot of oxygen and thus have their own oxygen storage molecule, myoglobin, which is capable of holding one O2 molecule.
- Also mature (differentiated) skeletal muscles are frozen in Go phase and do not divide (similar to neurons)
Cardiac muscle characteristics
- Involuntary, striated, one nucleus.
- Unlike skeletal muscles, cardiac cells continue dividing after differentiation.
Cardiac muscle contraction mech.
Does contain sarcomeres and uses the same sliding filament mechanism as skeletal muscle.
Smooth muscle characteristics
Involuntary, non-striated, one nucleus.
Smooth muscle contraction mech.
Smooth muscle is NOT arranged in sarcomeres. Therefore it does not contain troponin. Uses a calcium cascade mechanism instead.
Support, protection, movement, mineral storage (calcium and phosphate), energy storage (as fat in the marrow), and blood cell formation.
Mature bone cells surrounded by a mineral matrix.
Bone cells that break down and resorb bone matrix, releasing the component minerals (Ca2+ and P) back into the blood.
Immature bone cells that secrete collagen, organic compounds, and minerals forming a bone matrix around themselves. Once they are completely enclosed by matrix, they differentiate into osteocytes.
Anatomy of long bone
Two epiphyses (bulbous ends) cushioned by cartilage; the ends are filled with spongy bone and the shaft in between is made of compact bone; the center is a hollow cavity filled with yellow bone marrow.
A compound of calcium, phosphate, and hydroxide. It is the mineral matrix responsible for a bone's strength and is the form in which most all of the body's calcium is stored.
- A connective tissue made of collagen.
- No perfusion or innervation
- Found in appendages such as the nose and ears, at the ends of the long bones, between vertebrae, at the rib-sternum (sternocostal) joints, etc.
Types of joints
- 1) Fibrous (skull bones)
- 2) Cartilaginous (ribs and sternum)
- 3) Synovial (knee, elbow, etc.)
Spermatozoa are produced by the testicles in the seminiferous tubules and stored and nurtured in the epididymis. They are a SINGLE, HAPLOID cell consisting of a head (cell body) and tail (flagellum). They contain lots of mitochondria.
Sperm leave the epididymis via the vas deferens. The vas deferens arches back up into the pelvis and then back towards the penis. Along this path seminal vesicles, prostate gland and bulbourethral gland (a.k.a. Cowper's gland) all secrete various lubricants and nutrients into the ejaculate.
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