L5 - Muscle & Nervous tissue

Question 1

Explain the appearance of striated muscle, and where it is found

Answer 1

Striations are a result of sarcomere organisation. The arrangement of actin and myosin in regular arrays results in a light band where there is no overlap between actin and myosin (I band), and a dark band where there is overlap between the two (A band)
Seen in skeletal muscle and cardiac muscle

Question 2

Describe a Sarcomere

Answer 2

From Z-line to Z line, is made up of 8 actin filaments and 3 myosin filaments.
Actin is connected to the Z line by alpha-actinin protein filaments, myosin is anchored by titin filaments.
The myosin filaments ‘hover’ between the actin filaments.
The area of myosin that does not overlap with actin is called the H band

Question 3

Compare skeletal and cardiac muscle cells

Answer 3

Skeletal muscle cells can be larger than cardiac cells and have multiple peripheral nuclei. They are fast contracting
Cardiac muscle cells are short and branched, and have a single central nuclei and intercalated disks

Question 4

What is a fascicle?

Answer 4

A bundle of muscle cells, wrapped in connective tissue

Question 5

What is a motor unit?

Answer 5

A motor neuron and all the muscle fibres it innervates

Question 6

Describe smooth muscle

Answer 6

Spindle shaped cells, much shorter than those in skeletal muscle, which have a single, central nuclei. It is nerve regulated and can hold contractions

Question 7

Describe a neuron

Answer 7

Soma is the cell body
Dendrites are short, branched extensions of the cell body and receive chemical messages from other neurons
An axon is a very long extension that is involved in transmission of electrochemical signals to other neurons. These are normally myelinated.
Nodes of Ranvier are non-myelinated areas