Histology Flashcards

Question

involuntary: Smooth muscle

Answer 1

Made up of sheets of muscle cells Location: many internal organs walls of arteries and veins digestive tract urinary bladder reproductive organs myosin and actin filaments – not regularly arrayed along the length of the cell smooth muscle cells contracted when they are stimulated by neurons of the ANS (autonomic nervous system) contract and relax more slowly than skeletal muscles Muscle activity is a response to input from the nervous system

Answer 2

Involuntary muscle that needs no conscious control Small uninucleate cells Fibres are striated – branched Intercalated discs: the gap junctions hold the cells together Electrical impulses are thus allowed to cross the gap junctions Allows synchronizes the heart beat and creates rhythmic pumping

Answer 3

``` Attached to bones by tendons They are controlled by the consciousness Multinucleated cells Made up of bundles of skeletal muscle fibres Fusion of many cells Therefore, there are many nuclei in a single muscle fiber ``` Myofibrils Myofilaments of actin and myosin Striated because they are divided into contractile units that have thick and thin fibres Sarcomeres = contractile units along a muscle fiber The arrangement gives the muscle a striated appearance Skeletal muscle → muscle fascicle → muscle fiber → myofibril (arranged longitudinally) → myofilament → (light and dark bads alternating) → actin and myosin Each individual fiber is a single cell Each fiber has multiple nuclei that are derived from the embryonic cells that fused together and they run parallel to the length of the muscle Move the bones and the body

Answer 4

Thin filaments Consist of two strands of actin and two strands of a regulatory protein Thick filaments Staggered arrays of myosin molecules Striated = regular arrangement of myofilaments S Patel Creates a regular arrangement of myofilaments creates a pattern of light and dark bands

Answer 5

A functional unit of a muscle Bordered by Z lines Where thin, actin filaments attach Basic contractile units of a muscle The borders of the sarcomere line up in adjacent myofibrils Forms light and dark bands Thick filaments are anchored in the middle – M line Relaxed myofibril Thick and thin filaments partially overlap Edge of the sarcomere there are only thin filaments Centre there are only thick filaments

Answer 6

``` Net like structure around the myofibrils Contains the cytoplasm of muscle cells Specialised endoplasmic reticulum The cytoplasm is outside of the cell Ease of contraction of muscles – faster ``` There are a lot of mitochondria – ATP provided for muscle contraction

Answer 7

Filaments slide past each other longitudinally Produce more and more overlap between thick and thin filaments The Z zones move more and more closer together Sarcomere length decreases Actin filaments move closer and closer together

Answer 8

*Myosin: has a long tail and a globular head Head can bind to ATP and this is when it is in its low energy configuration When the ATP is hydrolyzed then the myosin coverts to a high energy configuration 1. The myosin head is in its low-energy configuration. This is because it is bound to the ATP molecule 2. The myosin head hydrolyzes ATP to ADP and P and it is in its high-energy configuration 3. The myosin head binds to actin (myosin binding site), forming a cross-bridge with the thin filament S Patel 4. The myosin couples release the ADP and P and there is a power stroke that slides the thin filament along the myosin and returns the myosin head to a low- energy state The thin filament moves towards the center of the sarcomere The myosin head returns to low-energy configuration 5. A new molecule of ATP releases the myosin head from the actin and a new cycle begins

Answer 9

- The regulatory protein tropomyosin and troponin complex bind to actin strands on thin filaments when the muscle fiber is rest - this prevents the actin and myosin from interacting covers the myosin binding sites - the troponin complex has Ca2+ binding sites for muscle fibres to contract, myosin-binding sites must be uncovered -this occurs when the calcium ions bind to the troponin complex and exposes the myosin-binding sites - contraction occurs when the concentration of calcium ions is high and stops when the concentration is low

Answer 10

1. The synaptic terminal of the motor neuron releases the neurotransmitter, acetylcholine (ACh) 2. ACh depolarizes the muscle and causes it to produce an action potential 3. the action potential travels through the plasma membrane down the T(transverse)- tubules 4. this causes the Ca2+ to be released from the SR 5. Ca2+ binds onto the troponin and this causes the tropomyosin to shift from the position over the myosin binding sites 6. Muscle contraction is allowed as the myosin forms cross bridges with the actin 7. After the action potential ends, cytosolic Ca2+ is removed by active transport into the SR 8. Once all the calcium ions are removed the tropomyosin returns to its original position and blocks the myosin binding sites on the actin 9. Contraction ends 10. Muscle fiber relaxes

Histology Flashcards

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