Download presentation
1
Muscles &Muscle Tissue
Chapter 9
2
Function of Muscles Movement Posture Stabilization of Joints
Thermogenesis (heat production)
3
Functional Characteristics of Muscle
Excitability (irritability) Can receive and respond to stimuli. Stimuli can include nerve impulses, stretch, hormones or changes in the chemical environment. Contractility – the ability to shorten with increasing tension. Extensibility – the ability to stretch. Elasticity – the ability to snap back (recoil) to their resting length after being stretched.
4
Three types of muscle Skeletal Smooth Cardiac
5
Characteristics of Skeletal Muscle
Striated Multinucleate (it is a syncytium) Voluntary Parallel fibers
6
Arrangement of connective tissue in skeletal muscle
7
Muscle microstructure
8
Myosin
9
A thick myofilament
10
A thin myofilament Made of actin, troponin and tropomyosin
11
Arrangement of myofilaments
12
The sarcomere: the functional unit of skeletal muscle
13
Anatomy of a myofibril
14
Summary of skeletal muscle anatomy: muscles are made of fascicles
15
Fascicles are made of fibers, fibers are made of myofibrils
16
Fibrils are divided into sarcomeres, sarcomeres are made of myofilaments
17
Myofilaments are made of protein molecules
18
Muscle Contraction: the Sliding Filament Theory
Muscle contraction requires: Stimulus – the generation of an action potential. Crossbridge formation – interaction between the thick and thin myofilaments. This is triggered by Ca++ ions released from the sarcoplasmic reticulum. Energy – ATP to energize the myosin molecules.
19
T- tubules supply the stimulus, Sarcoplasmic Reticulum supplies the Ca++, Mitochondria supply the ATP.
20
The role of Calcium ions
21
Muscle contraction
22
Show the animation
23
Excitation-Contraction coupling
Stimulus or excitation is required for muscles to contract. In skeletal muscle, the stimulus is from a motor neuron. The stimulus is in the form of an action potential. This action potential starts at the neuromuscular junction (NMJ).
24
A neuromuscular junction (NMJ).
25
acetylcholine The actual synapse
26
Excitation-contraction coupling
27
Show NMJ animation
28
Motor units
29
Micrograph of an NMJ
30
A Synapse Synaptic vesicles
31
Myogram of a single muscle twitch
32
Comparative speed of different muscles
33
Graded Muscle Responses
The “twitch” describes just one fiber, it really isn’t how muscles normally work. Muscles contract smoothly and respond to different levels of demand. This is accomplished through “graded responses”. There are two ways muscle responses are “graded”
34
Wave Summation Wave summation is accomplished by repeated stimuli.
As the rate of stimulus delivery increases, there is less and less time for the fiber to relax between stimuli. If the stimuli are rapid enough, the muscle fiber will contract completely and remain contracted until the stimulus stops of the muscle fatigues. This is called tetanus (or tetany).
35
Recruitment Since action potentials are “all-or-none” responses, when a fiber is stimulated to tetany, it exerts maximum tension. To respond to stronger stimuli and thus increase the amount of tension, muscles will recruit more motor units until they reach maximal stimulus and all the motor units are recruited This continues until they either accomplish their task or fatigue.
36
Treppe
37
Types of contractions Isometric – means “same length”. Force is developed without measurable movement. Isotonic – means “same tension” movement is achieved with force or “tension” remaining constant.
38
Isotonic contraction: Concentric
39
Eccentric Contraction
This refers to the tension that is applied on a muscle as it lengthens. Example: When you lower the dumbbell you just lifted, you don’t do so by allowing the muscle to just relax. Think about the consequences of that! Eccentric contractions are about 50% more forceful than concentric ones.
40
Isometric Contraction
41
Energy physiology in skeletal muscle
42
Anaerobic Metabolism: a losing proposition
43
Aerobic endurance
44
Anaerobic endurance
45
Fiber Types Fast Glycolytic (fast twitch a or type IIB)
few mitochondria, adapted for fast, powerful contraction, large diameter, little myoglobin (white fibers), few capillaries, fatigues rapidly Fast Oxidative (fast twitch b or type IIA) many mitochondria, fast contraction, intermediate diameter, lots of myoglobin & capillaries (pink fibers), moderately fatigue resistant Slow Oxidative (slow twitch or type I) many mitochondria, slow contraction, smallest in diameter, don’t hypertrophy, lots of myoglobin & capillaries, very fatigue resistant, red fibers
46
Stretch and tension
47
Stretch/Tension
48
The Effect of Load on Contraction
49
Smooth Muscle
50
Varicosities
51
Contraction of smooth muscle
52
Skeletal Smooth Diameter 10 - 100 m 3 - 8 m Connective tissue
Epi-, Peri- & Endomysium Endomysium only SR Yes, complex Barely, simple T - tubules yes no Sarcomeres Gap Junctions voluntary Neurotransmitters Acetylcholine (Ach) Ach, epinephrine, norepinephrine, et al Regeneration Very little Lots, for muscle
53
Future governors of Califorina?
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.