chapter 9 - muscular system; part 1

Question 1

what are some of the functions of the muscular system?

Answer 1

1. movement of the body
2. maintenance of posture
3. respiration
4. production of body heat
5. communication
6. constriction of organs and vessels
7. contraction of the heart

Question 2

what are the 3 types of muscle tissue?

Answer 2

skeletal, smooth, cardiac

Question 3

skeletal muscle

Answer 3

responsible for most body movements; voluntary

Question 4

smooth muscle

Answer 4

found in the walls of hollow organs and tubes and moves substances through them; involuntary by endocrine and autonomic nervous system

Question 5

cardiac muscle

Answer 5

it is in the heart and pumps blood; involuntary by endocrine and autonomic nervous system

Question 6

the muscle exhibits what?

Answer 6

they exhibits contractility (shortens forcefully), excitability (responds to stimuli), extensibility (can be stretched and still contract), and elasticity (recoils to resting length); muscle tissue shortens forcefully but lengthens passively

Question 7

what are skeletal muscle fibers associated with?

Answer 7

they are associated with connective tissue, blood vessels, and nerves

Question 8

what is a muscle fasciculi?

Answer 8

bundles of muscle fibers, are covered by the connective tissue layer called the perimysium

Question 9

what is the muscle surrounded by?

Answer 9

the entire muscle is surrounded by a connective tissue layer called the epimysium; motor neurons extend together with arteries and veins through the connective tissue of skeletal muscles

Question 10

what is going on at the level of the perimysium?

Answer 10

at the level of the perimysium, axons of motor neurons branch and each branch projects to a muscle fiber to form a neuromuscular junction

Question 11

what is a muscle fiber?

Answer 11

it is a single cell consisting of a plasma membrane (sarcolemma), cytoplasm (sarcoplasm), several nuclei, and myofibrils

Question 12

what 2 major protein fibers make up myofibrils?

Answer 12

actin and myosin

Question 13

what do actin myofilaments consists of?

Answer 13

they consist of a double helix of F actin (composed of G actin monomers), tropomyosin, and troponin

Question 14

what do myosin molecules consist of?

Answer 14

they consist of two globular heads and a rod-like portion, constitute myosin myofilaments

Question 15

when does a crossbridge form?

Answer 15

it forms when the myosin binds to the actin

Question 16

what are actin and myosin organized to form?

Answer 16

they are organized to form sarcomeres; sarcomeres are bound by z disks that hold actin myofilaments

Question 17

why does the membrane become polarized?

Answer 17

because there is a charge difference, called the resting membrane potential, exists across the plasma membrane

Question 18

when a plasma membrane is polarized it means what?

Answer 18

that the tendency for K+ to diffuse out of the cell is resisted by the negative charges of ions and molecules inside the cell

Question 19

what are 2 types of channels that produce action potentials?

Answer 19

ligand-gated and voltage-gated channels