Exam 2: Muscle Flashcards
1
Q
Characteristics of Muscle
1.
2.
3.
4.
A
- Excitability (responsiveness) – muscles can be stimulated by electrical, chemical, and physical means.
- Contractility – muscle responds to stimuli by contracting.
- Elasticity – muscles tend to recoil to their resting length.
- Extensibility – muscles can be stretched beyond their resting length.
2
Q
What kind of muscle is this?
A
skeletal
- attached to the bones for movement
- long, cylindrical cells; multinucleated, striated
- voluntary
3
Q
What kind of muscle is this?
A
cardiac
- one nucleus per cell
- also striated, but branching
- intercalated disc: like gap junctions, for communication. Only found in the heart
4
Q
What kind of muscle is this?
A
smooth muscle
5
Q
Is the esophogas smooth or skeletal muscle?
A
skeletal
6
Q
A single motor unit consists of:
A
a motor neuron and all of the muscle fibers it controls.
7
Q
A
Structure tells about function
- looks similar to a rope or fiber → good for STRENGTH.
8
Q
storage place of a very key ion involved in muscle contractions: calcum
A
sarcoplasmic reticulum
9
Q
plasma membrane that encloses the muscle cells
A
sarcolemma
10
Q
cytoplasm of muscle cells and contains myoglobin (red pigment that stores oxygen)
A
sarcoplasm
11
Q
sarcolemma has invaginations that penetrate through the cell called transverse tubules
A
T-tubule
12
Q
area between 2 Z discs - smallest contractile unit
A
Sarcomere
13
Q
chain of sarcomeres
A
myofibril
14
Q
a zipper like structure in midline of I band - anchors thin filaments & connects each myofibril to next
A
Z disc
15
Q
light colored bands on myofibrils
A
I band
16
Q
dark colored bands on myofibrils
A
A band
17
Q
A
connectins (crossbridge attachments) form between myosin heads and actin
18
Q
- blocks the crossbridge attachment sites on actin.
- shifts to move tropomyosin and expose the active sites.
A
- Tropomyosin
- Troponin
19
Q
Sliding of the actin and myosin myofilaments against one another produces:
1.
2.
3.
A
1) myosin pulls actin along
2) shortening of sarcomeres
3) resultant muscle contraction
20
Q
Understand the Neuromuscular Junction
A
21
Q
Transmission of Nerve Impulse to Muscle:
The neurotransmitter for skeletal muscle is
A
acetylcholine (ACh)
22
Q
Acetylcholine attaches to receptors on the , which becomes permeable to sodium (Na+), which allows the nerve impulse to continue into the muscle cell.
A
sarcolemma
23
Q
The Sliding Filament Theory
of Muscle Contraction:
- Activation by nerve causes:
- Myosin heads then:
- This continued action causes:
- The result is that:
A
- myosin heads (cross bridges) to attach to binding sites on the thin filament
- bind to the next site of the thin filament and pull them toward the center of the sarcomere
- a sliding of the myosin along the actin
- the muscle is shortened (contracted)
24
Q
- impulse…
- enters…
- triggers the release of…
- pumped into…
A
- impulse travels along the sarcolemma
- enters the T-tubules
- triggers the release of Ca2+ from the S.R. → crossbridges
- Ca2+ pumped into the S.R. as the crossbridges unattach
25
The T-tubules and SR are connected with junctions. These junctions involve:
two integral membrane proteins,
* one in the T-tubule membrane,
* the other in the membrane of the sarcoplasmic reticulum.
26
The T-tubule protein is a known as the dihydropyridine (DHP) receptor, which acts as .
1. modified voltage-sensitive Ca2+ channel
2. a voltage sensor
27
The protein embedded in the SR membrane is known as , which forms a Ca2+channel.
the ryanodine receptor
28
ATP is also integral for relaxation of our muscles. Why is this?
29
Organization of Muscle Structure, from largest to smallest (starting with muscle)
30
Case study:
Upon death, the body remains in a state of muscular rigidity (Rigor Mortis) for a couple days. Based on what you have learned, explain what might be going on.
* detachment of muscles needs ATP - when you aren't producing ATP (because you are dead) you can't detach your muscles and they remain rigid!
* Acetylcholesterase is also needed to break down acetylcholine to be able to relax.
31
Contraction strength is a function of:
* the number of crossbridges that can be made per myofibril
* the number of myofibrils per muscle fiber
* the number of contracting muscle fibers
32
So as animals get larger, their relative strength because their weight increases at a faster rate, a cubic function, than their muscular strength, a square function.
1. diminishes
33
motor neuron + all muscle cells/fibers it stimulates -- attaches to muscles spread throughout the muscle
Motor unit
34
\< 10 cells per motor unit (e.g. extraocular muscles)
Very Precise Control
35
= 10 to 100 cells per unit (most muscles)
Average Control
36
\>100 cells per unit (e.g. postural muscles)
Gross Control
37
muscle force exerted on object - E.g., muscle of hand holding a 30 lb ball above the head
Muscle Tension
38
tension develops & the object or load is moved
Isotonic Contraction
39
* tension develops but the object doesn’t move
* Myofilaments try to slide but can’t
Isomeric contraction
40
* continuous partial contractions
* So body is in constant readiness for movement
Muscle Tone
41
recording of muscle contraction
myogram
42
single, brief stimulus causes short muscle contraction
Muscle Twitch
43
1st few ms when excitation-contraction coupling is happening (pre-contraction of muscle fibers) - muscle tension is beginning to increases
Latent Period
44
crossbridges are actively contracting the muscle - muscle tension peaks
Contraction Period
45
muscle tension is decreasing -- Ca2+ is reinterring sarcoplasmic reticulum
Relaxation Period
46
The latent period between excitation and development
of tension in a skeletal muscle includes the time
needed to release Ca++ from sarcoplasmic reticulum,
move tropomyosin, and cycle the cross-bridges.
47
Twitch Lengths
48
minimum stimulus for contraction
threshold stimulus
49
strongest stimulus that makes all motor units contract
maximal stimulus
50
a term that refers to the additional force produced as a result of an increase in stimulation frequency
summation
51
a state where maximum force generation is produced using both maximum stimulation intensity and a frequency of stimulation that produces no further increase in force
Tetanus
52
Definition of Incomplete Tetanus:
quivering contraction - almost smooth
53
Definition of Complete Tetanus:
high frequency stimuli don’t permit the muscle to relax, producing a sustained contraction - a smooth contraction - leads to muscle fatigue
54
Whole muscles typically consist of mixtures of different types of fibers
55
Muscle Metabolism
* Very little ATP is stored in muscle (only ~5 seconds worth)
* 3 Pathways for generating ATP:
* 1
* 2
* 3
1. Creatine Phosphate
2. Anaerobic Glycolysis
3. Aerobic Respiration
56
57
Creatine Phosphate
* Aka: phosphagene system
* CP (creatine phosphate) is stored in muscle in high quantities
* CP + ADP make ATP
* provides ~ 15 seconds worth of energy
* CP reserve is quickly used but quickly replenished
* short-lived strenuous activity (15 seconds)
58
Anaerobic Glycolysis
* Glycolysis: conversion of either glucose (bloodborne) or glycogen (stored in muscle)
* Results: 2 pyruvic acid molecules & small amount of ATP energy
* most of pyruvic acid is converted to lactic acid
* contraction of muscles cut off blood flow, cutting off oxygen
* does not use oxygen
* produces only 5% of ATP of aerobic respiration but does it 2 1/2 times faster
* Moderate, strenuous activity (30 - 40 seconds)
59
Aerobic Respiration
* 95% of muscular ATP
* occurs in mitochondria w/ aid of oxygen
* Glucose + Oxygen are completely broken down
* water, CO2, lots of ATP (~36 units)
* works slowly - requires continuous source of oxygen & nutrients
* high endurance activities (many hours)
60
Slow-oxidative skeletal muscle responds well to repetitive stimulation without becoming fatigued; muscles of body posture are examples.
61
Fast-oxidative skeletal muscle responds quickly and to repetitive stimulation without becoming fatigued; muscles used in walking are examples.
62
Fast-glycolytic skeletal muscle is used for quick bursts of
strong activation, such as muscles used to jump or to run a short sprint.
63
All three types of muscle fibers are represented in a typical skeletal muscle, and, under tetanic stimulation, make the predicted contributions to the development of muscle tension.
64
65
* When ATP production \< ATP usage
* contractions are increasingly less efficient
* eventually will refuse to contract even though still receiving stimuli due to relative deficit not absence of ATP
* When no ATP present → crossbridges won’t detach
Muscle Fatigue
66
Force of muscle contraction depends on...
* # of muscle fibers contracting
* the more that are contracting, the greater the force
* size of the muscle
* larger = greater contraction
* degree of muscle stretch
* optimal length at rest = length where get most force
* length-tension relationship = ideal is when the muscle is slightly stretched & the actin & myosin filaments barely overlap
