Ch.9-Muscular System

Question 1

Briefly describe the muscle types.

Answer 1

Skeletal muscle is voluntary striated muscle that is usually attached to bones. It has long, slender cells called muscle fibers.

Cardiac muscle is involuntary striated muscle.

Smooth muscle is similar but not identical to skeletal muscle. It is not under voluntary control and has slow sustained contractions.

Question 2

What is muscle tissue used for?

Answer 2

Movement and stability of the body

Control of body passages and openings

Heat production

Muscle cells are able to carry out: excitability, conductivity, contractility, extensibility and elasticity

Question 3

Describe composition of skeletal muscle.

Answer 3

Skeletal muscle is composed of:

Muscular tissue

Connective tissue

Nervous tissue

Blood vessels

The muscle attachment at the stationary end is called its origin, and at the moving end is called the insertion.

Skeletal muscle contracts only when stimulated by a somatic motor neuron(this is known as contractility).

Question 4

Describe a muscle fiber.

Answer 4

A muscle fibre is a long, slender cell with multiple nuclei just inside the sarcolemma.
The sarcoplasm is occupied mainly by myofibrils, which are thread-like bundles of protein filaments.
Each myofibril is a bundle of protein myofilaments.
The thick filaments are made up mostly of myosin, and the thin filaments are made up mostly of actin.

Question 5

Describe contractility.

Answer 5

Nerves and muscle fibre meet at a complex of synapses called a neuromuscular junction.
Each tip of a nerve fibre ends in the synaptic knob.
A narrow gap, the synaptic cleft, separates the synaptic knob from the sarcolemma.
The synaptic knob contains synaptic vesicles filled with the chemical ACh.
An enzyme called acetylcholinesterase, found in the synaptic cleft and as part of the sarcolemma, breaks down ACh to terminate stimulation of the muscle fibre.

Question 6

Describe smooth muscle.

Answer 6

Smooth muscle fibres are much smaller than skeletal muscle fibres, and does not have striations like skeletal muscle.

A different type of myosin exists in smooth muscle.

There are 2 types of smooth muscle:
Multiunit(found in the eyes and blood vessels)
Visceral(found in hollow organs) - the wave-like motion of many tubular organs, known as peristalsis, is caused by visceral smooth muscles.

Smooth muscle, unlike skeletal muscle, is affected by the neurotransmitter called norepinephrine.

Smooth muscle takes approx. 30 times longer than skeletal muscle to contract and relax, but uses much less energy.

Smooth muscle contraction is regulated by nerves, hormones and local chemical changes.

Question 7

Name the large superficial muscles of the body.

Answer 7

Muscle pdf