Lecture 1: Muscle Structure

Question 1

each muscle consists of _____ to ______ of individual contractile fibers

Answer 1

hundreds to thousands

Question 2

connective tissue:

Answer 2

mostly collagen some elastin

Question 3

epimysium

Answer 3

tough coat of tightly woven bundles of collagen which surround entire muscle, separating it from other muscles and structures

Question 4

myotendinous junction

Answer 4

ends of the muscle where epimysium connects with the sarcolemma

Question 5

why does the myotendinous junction have extensive folding of the epimysium and sarcolemma

Answer 5

to increase surface area

Question 6

perimysium

Answer 6

• also tough and thick
• divides muscle fibers into fascicles or bundles
• provides pathways for arteries, veins and nerves

Question 7

endomysium

Answer 7

surrounds each muscle fiber, connections to both the perimysium and the basement membrane

Question 8

sarcolemma

Answer 8

consists of basement membrane and the plasmalemma

Question 9

conduit arteries and veins

Answer 9

run in parallel along the surface of muscle

Question 10

perforating arteries and veins

Answer 10

periodically branch and dive into belly of muscle in parallel, with several generations of branching

Question 11

arterioles lead to capillaries which __________. note multiple branching within network

Answer 11

capillaries surround each fiber!!

Question 12

nerves usually run in _____ with the arteries and veins

Answer 12

parallel

Question 13

motor nerves make up ____% of the nervous innervation of skeletal muscle

Answer 13

60%

Question 14

motor nerves represent ….

Answer 14

the final nerve in the path from the motor centers in the cerebrum to the target muscle

Question 15

motor nerve impulses travel in an _____ direction

Answer 15

efferent (away from CNS)

Question 16

due to the ________, impulses travel very fast along the axon

Answer 16

myelin sheath

Question 17

near muscle fibers, the myelin sheath ends and the axon splits sending a _______ to each fiber

Answer 17

terminal branch

Question 18

motor end plate

Answer 18

the region of muscle plasmalemma under the terminal axon

Question 19

sensory nerves represent ____% of the nerves in skeletal muscle

Answer 19

40%

Question 20

sensory nerves impulses run in a ______ direction

Answer 20

afferent direction (toward the CNS)

Question 21

sensory nerve impulses rely on a variety of _____, ____, ____, ____

Answer 21

touch, pain, muscle tension, contraction information

Question 22

skeletal muscle cells appear ______.

Answer 22

striated

Question 23

sarcolemma

Answer 23

the cell membrane surrounding each cell

Question 24

sarcoplasmic reticulum

Answer 24

membranous network that surrounds each myofibril

Question 25

what is the primary role of the SR?

Answer 25

the release of Ca++ which initiates the contraction process

Question 26

transverse tubules

Answer 26

membranous channels that extend inward from the sarcolemma and pass completely through the fiber

Question 27

cisternae

Answer 27

enlarged portions of the SR that the t-tubules pass through

Question 28

motor end plate is the site where the _____ ends and transmits depolarization signal to the muscle

Answer 28

alpha-motorneuron

Question 29

does the alphamotorneuron touch the arcolemma?

Answer 29

no

Question 30

neuromuscular or synaptic cleft

Answer 30

the space where the sarcolemma invaginates around the alpha-motorneuron synapse

Question 31

steps in excitation contraction coupling

Answer 31

1 a-motorneuron depolarizes leads to release of ACh

2. ACh binds causing Na+ to enter the cell, leading to the depolarization of the muscle cell (end-plate potential)
3. depolarization wave on sarcolemma is transmitted down t-tubules
4. calcium released from SR
5. Ca++ binds to troponin initiating contraction process
6. Ca++ pumped back into SR by SR Ca++ ATPase
7. Ach is broken down by acetylcholinesterate

Question 32

sliding filament theory steps

Answer 32

1. rest
2. excitation coupling
3. active contraction
4. recharging system
5. subsequent response dependent on presence of Ca++

Question 33

why when animals or people die do their bodies go into rigor?

Answer 33

run out of ATP