1 - skeletal muscle physiology

Question 1

what are 3 types of muscle?

Answer 1

1. skeletal
2. cardiac
3. smooth

Question 2

which types of muscle are striated?

Answer 2

cardiac and skeletal

Question 3

what nervous system innervates skeletal muscles?

Answer 3

somatic nervous system - allows voluntary movement

Question 4

what nervous system innervates cardiac & smooth muscle?

Answer 4

autonomic nervous system, both muscle types are involuntary

Question 5

is skeletal muscle contraction neurogenic or myogenic?

Answer 5

neurogenic = means that contraction is initiated & controlled by signals in nervous system (acetylcholine etc)

Question 6

is cardiac muscle contraction neurogenic or myogenic?

Answer 6

myogenic = means that contraction is initiated by hearts own pacemaker cells like SA node

Question 7

what junctions are present in
a) skeletal muscle?
b) cardiac muscle?

Answer 7

a) neuromuscular junction
b) gap junctions

Question 8

what muscle type is organised into motor units?

Answer 8

skeletal muscle

Question 9

what is a motor unit?

Answer 9

a motor unit is a section of muscle fibres all innervated by a single alpha motor neuron

muscle = the organ. made up of muscle fibres. each muscle fibre = 1 muscle cell

Question 10

how many muscle fibres per motor unit?

Answer 10

varies depending on function
- muscles which serve fine movements have fewer fibres per motor unit

Question 11

what are the thick & thin filaments in skeletal muscle?

Answer 11

myocin (thick & dark) & actin (thin & light)
- they are alternating in myofibrils

Question 12

what is a sarcomere?

Answer 12

functional unit of skeletal muscle (smallest components capable of performing all functions of that organ)
- it’s found between 2 Z lines that connect thin filaments of adjoining sarcomeres

Question 13

what are the 4 zones of sarcomeres?

Answer 13

• A band = thick (myocin) w small overlap of ends of actin
• H zone = area in middle of A band where only myocin and no ends of actin
• M line = vertical line down middle of A band and H zone
• I band = remaining portion of actin that don’t project into A band

Question 14

what is the process of skeletal muscle contraction?

Answer 14

1. Ach released and AP generated along T-tubule
2. Ca2+ release from lateral sacs of sarcoplasmic reticulum
3. ATP binds to troponin C changing confirmation of tropomyosin complex exposing binding site to allow cross bridging of actin & myosin so overlap and ocntraction can occur

*Ca2+ taken up by SR when no longer AP