Lecture 6: Skeletal Muscle

Question 1

Skeletal Muscle Tissue

Answer 1

Moves the skeleton
- striated

Question 2

How does skeletal muscle connect to skeletal system? How are they organized?

Answer 2

Tendons and organized within layers of fasciae (contains several muscle fibers)

Question 3

Tendons

Answer 3

Narrow and/or round
Dense regular connective tissue

Question 4

Aponeuroses

Answer 4

Broad and flat sheet of dense regular connective tissue

Question 5

Muscle

Answer 5

Each individual muscle is an organ that consists of several tissue types

Question 6

Epimysium

Answer 6

Surrounds the whole muscle; connects to tendon Dense irregular connective tissue

Question 7

Perimysium

Answer 7

Surrounds a fascicle
Dense elastic connective tissue

Question 8

Endomysium

Answer 8

Surrounds each muscle fibre
Loose/areolar connective tissue

Question 9

Order of Muscle

Answer 9

Individual muscle > Muscle fascicle > Myofibre > Myofibril

Question 10

Myosatellite Cells

Answer 10

Stem cells for muscle tissue (within endomysium)

Question 11

Myofibre

Answer 11

Single cell that contains multiple nuclei and stretches from muscle origin to insertion

Question 12

How are myofibres produced?

Answer 12

By fusion of many myoblasts (stop after born)
Can be repaired in adulthood by myosatellite cells

Question 13

Myofibril

Answer 13

Specialized organelles found within myofibres

Question 14

Neuromuscular Junction

Answer 14

Each mature myofiber has one NMJ and is part of a motor unit

Question 15

Motor Neuron

Answer 15

A single motor neuron can make 1-1000 NMJs with myofibres

Question 16

Motor Unit

Answer 16

Combination of motor neuron and muscle cells

Question 17

What is a neuromuscular junction made up of?

Answer 17

An axon terminal, synaptic cleft, and motor end plate

Question 18

Sarcolemma

Answer 18

Cell membrane of myofibres

Question 19

Sarcoplasm

Answer 19

Cytoplasm

Question 20

Sarcoplasmic reticulum

Answer 20

Endoplasmic reticulum
Stores and releases calcium

Question 21

Transverse tubules (T-tubules)

Answer 21

At right angles to the cell surface; infolding of the sarcolemma

Question 22

Transverse tubules (T-tubules)

Answer 22

At right angles to the cell surface; infolding of the sarcolemma

Question 23

Contraction and Excitation

Answer 23

Contraction: Myofibres/myofibrils becoming shorter or producing tension

Excitation: The sarcolemma generating an electrical signal that precedes contraction

Excitation-contraction coupling refers to mechanisms by which excitation triggers contraction

Question 24

Steps of excitation of a muscle cell?

Answer 24

1. Electrochemical signal from a motor neuron down axon
2. Electrical excitation of NMJ
3. Propagation of the electrical signal down the myofibres

Question 25

Excitable Cells (muscle cells and neurons)

Answer 25

Can rapidly vary their transmembrane potential to send and receive signals
Arises from the unequal distribution of ions and unequal permeability if the membrane

Question 26

How does sodium enter into the myofibre?

Answer 26

Motor neurons releases a chemical neurotransmitter (acetylcholine) which causes opening of ion channels (receptors) that allow sodium into myofibres

Question 27

Acetylcholine

Answer 27

• Neurotransmitter
• Ligand
• Attaches to receptor (AChR that provides a path for sodium ions to cross the cell membrane)

Question 28

How does excitation propagate through the myofibre from the NMJ?

Answer 28

• voltage gated ion channels
• this spreading depolarization can cause extra voltage gated ion channels permeable to sodium to open, creating an action potential