DHUBS1 - week 6

Question 1

major organs of the muscular system

Answer 1

skeletal muscles
tendons

Question 2

functions of the muscular system?

Answer 2

body movement
maintenance of posture
respiration
protect and support other tissues
generate heat that helps to maintain body temperature
communication
control of blood flow in vessels

Question 3

three types of muscle tissue

Answer 3

Skeletal muscle:
Contraction produces body movement
Striated muscles that move bones around joints
Smooth muscle:
Contraction pushes fluids and/or solids through internal organs and passageways
Located in the walls of hollow organs, blood vessels and glands
Cardiac muscle:
Contraction pumps blood through the cardiovascular system
Striated muscle cells that make up the walls of the heart

Question 4

describe the functino the skeletal muscles

Answer 4

Produce movement by pulling on tendons and bones
Maintain posture and body position
Support soft tissues
Guard body entrances and exits
Maintain body heat
Store nutrients

Question 5

skeletal muscle characteristics

Answer 5

cytoplasm: called sacroplasm
plasma membrane: called sacrolemma
myofibrils
myofilaments
sacroplasmic reticulum
transverse tubules (T tubules)
sacromere
thin and thick filaments

Question 6

what happens when a muscle is contracting?

Answer 6

interaction occurs between thin and thick filaments within the sacromere. thin filaments slide towards the centre of each sacromere

Question 7

how does the muscle stop contracting?

Answer 7

interaction ceases between thin and thick filaments wihtin the sacromere. muscle returns to relaxing state.

Question 8

what are the 5 steps that initiate muscle contraction

Answer 8

1. Ach release
   Ach is released at the neuromuscular junction and binds to Ach receptors on the sarcolemma
2. Action potential reaches T tubule
   An action potential is generated and spreads across the membrane surface of the muscle fibre and along the T tubules.
3. Sarcoplasmic reticulum releases CA2+
   The sarcoplasmic reticulum releases stored calcium ions
4. Active site exposure and cross-bridge formation
   Calcium ions bind to troponin, exposing the active sites on the thin filaments. Cross-bridges from when myosin heads bind to those active sites
5. Contraction cycle begins
   The contraction cycle begins as repeated cycles of cross-bridge binding, pivoting and detachment occur – all powered by ATP

Question 9

what are the 5 steps that end muscle contraction?

Answer 9

6. Ach is broken down
   Ach is broken down by acetylcholinesterase (AChE), ending action potential generation
7. Sarcoplasmic reticulum reabsorbs CA2+
   As the calcium ions are reabsorbed, their concentration in the cytosol decreases
8. Active sites covered, and cross-bridge formation ends
   Without calcium ions, the tropomyosin returns to it’s normal position and the active sites are covered again
9. Contraction ends
   Without cross-bridge formation, contraction ends
   Muscle relaxation occurs
   The muscle returns passively to it’s resting length

Question 10

facts about energy for muscle contraction

Answer 10

the muscle fibre must make more ATP during the contraction to sustain the contraction for longer than 2 seconds

Question 11

smooth muscle characteristics

Answer 11

has no striations
involuntary - no concious control
found in walls of hollow organs
actin and myosin filament arrangements is more plastic, allowing greater adaptability

Question 12

cardiac muscle characteristics

Answer 12

has striations
involuntary

Question 13

the effect of exercise on muscle

Answer 13

1. increased endurance
2. increased strength of muscle