Responsible for voluntary movement
The cells in skeletal muscle
Have multiple nuclei as the result of the fusing of multiple cells.
Also contain high levels of mitochondria to provide ATP needed for contraction and the protein myoglobin that acts as an oxygen reserve for muscles.
Designed for a fast rate of contraction, but they lack stamina and fatigue easily because their primary energy source is anaerobic cellular respiration. They have less myoglobin and fewer mitochondria
Contain more myoglobin and mitochondria. This gives them longer endurance as they obtain most of their ATP from aerobic cellular respiration
What can serve as a short-term energy reserve for either type of muscle fiber when ATP levels are low?
What do muscle cells have?
Sarcoplasm (cytoplasm), a modified endoplasmic reticulum called the sarcoplasmic reticulum, and a cell membrane called the sarcolemma
How does the sarcolemma interact with the nervous system and what does this system provide?
It interacts with the nervous system via the transverse tubule system (T tubule). This system provides channels for ion flow through the muscle and has anchor points for sarcomeres
Within the muscle cells. These are made of the proteins actin, troponin, tropomyosin, and myosin
Have a thin diameter and associate with the proteins troponin and tropomyosin to produce filaments
Have a thick diameter with protruding heads and are called thick filaments
In skeletal muscles, the actin and myosin fibers overlap each other in these highly organized, repeating units
What does the overlapping of the fibers cause?
This causes striation of the muscle
What causes muscle contraction?
The shortening of the sarcomeres
Shortening of the sarcomere occurs when actin filaments move toward the center of the sarcomere. This shortening of the sarcomere is responsible for skeletal muscle contraction
What are the 5 major regions of the sarcomere?
The line that marks the center of the sarcomere
The line that separates one sarcomere from the next
The area where only thick filaments are present; it shortens during contraction
The area where only thin filaments are present; it shortens during contraction
The area where thick and thin filaments overlap
Regions in muscle tissues where the sarcolemma is in contact (via a synapse) with the synaptic knobs of a motor neuron from the somatic branch of the peripheral nervous system
Which neurotransmitter is released from the motor neuron and binds to receptors on the sarcolemma? What does this cause?
Acetylcholine. This causes an action potential that initiates shortening of the sarcomeres.
The muscle fibers influenced by a single neuromuscular junction
The action potential that occurs based on stimulation from the motor neuron releases what from where and into where?
Causes the release of calcium from the sarcoplasmic reticulum into the sarcoplasm
Where does the calcium bind? What does this cause?
It binds to the troponin in the filaments. This causes a conformational shift in the tropomyosin protein in the thin filament
What does this change in shape allow for?
It allows for the exposure of myosin binding sites on the actin
What can the myosin heads now bind to?
They can now bind to the myosin binding sites on the actin, formin cross-bridges
What allows the stroke to occur and what does this do?
Hydrolysis of ATP allows the power stroke to occur, which pulls the thin filaments toward the center of the sarcomere
When does the release of the actin myosin heads from the actin occur?
This occurs when another ATP binds to the myosin heads
What happens when the sarcolemma is no longer stimulated by the motor neuron?
The process of contraction occurs
What happens when contraction ends?
ATP bind to myosin heads, causing them to dissociate from actin. The calcium is collected and transported back to the sarcoplasmic reticulum. Without calcium, the myosin binding sites are blocked by troponin and tropomyosin, and the sarcomere returns to the original length
Why is smooth muscle not striated?
Although it contains actin and myosin, it is not organized as sarcomeres
Sympathetic response of smooth muscle
Uses the neurotransmitter epinephrine (adrenaline) and norepinephrine (noradrenaline) to prepare the body for physical activity
Responds to acetylcholine and uses it to return the body and muscles to a relaxation state
Smooth muscle can perform this; this means it can also contract without stimulation from the nervous system
Where is cardiac muscle only found?
In the myocardium of the heart
Is striated but it is not multinucleated like skeletal muscle
What is a disadvantage of an exoskeleton?
It does not grow with the organism, making it necessary to shed the skeleton and produce a new one to accommodate growth
What are the two major parts of the human exoskeleton?
The axial skeleton and the appendicular skeleton
Composed of the skull, the vertebral column, the sternum, and the rib cage
The pelvic and shoulder girdles and limbs of the body
The matrix is termed chondrin and the primary cell type is the chondrocyte
What happens to cartilage during development; it is turned into bone by a calcification process
Less dense and contains marrow cavities
What is within marrow?
Yellow and red bone marrow
Red bone marrow
Contains the stem cells that differentiate into red blood cells, white blood cells, and platelets
Yellow bone marrow
Primarily a reserve for adipose tissue
Spongy bone tissue contains red bone marrow and is located at the ends of long bones. The hollow marrow cavity located in the shaft of the bone contains yellow bone marrow
The ends of the bone that are typically covered in cartilage
The shaft of the bone that is made of compact bone surrounding a marrow cavity
A disc of cartilage that separates the diaphysis from each epiphysis, and this is where bone lengthening and growth occurs
Surrounds the bone in a fibrous sheath and acts as a site for the attachment of muscles via tendons
In the microscopic structure of bone, where is the matrix found?
Within the osteons
Within each osteon; contains blood vessels, nerves, and lymphatic vessels
Surrounds the canal; concentric circles of hard matrix
Within the matrix of the lamellae; small spaces where mature bone cells reside
Small bridges that connect the lacunae within an osteon and merge into the Haversian canal in order to distribute nutrients and wastes
What are the 3 major cell types within bone?
Osteocytes, osteoblasts, and osteoclasts
Found within the lacunae of osteons. They are mature bone cells involved in the maintenance of bone tissue
Osteoblasts and osteoclasts
Found within bone tissue as wells, and are immature cells
Osteoblasts in bone remodeling
Osteoblasts build bone by producing components of the matrix; they are responsible for bone growth and ossification during development
Osteoclasts in bone remodeling
Break down bone in the process of bone reabsorption
What eventually happens to osteoblasts and osteoclasts?
They become trapped within matrix of bone tissue and become osteocytes
What two hormones are responsible for bone remodeling?
Calcitonin from the thyroid gland and parathyroid hormone from the parathyroid glands
What happens when blood levels are high?
Calcium is stored in the matrix, thus building bone
What happens when blood levels are low?
Calcium is released from the matrix by the breakdown of bone tissues
Hip or knee; have a larger range of motion and have a fluid-filled joint cavity
Made of dense connective tissue and attach one bone to another within a synovial joint