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Muscle Basics
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Lecture notes of 6 pages for the course ANAT100 at QU (Muscle Basics)
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ANAT 100 – module 3 Muscle BasicsSECTION 1: Types of Muscle
Intro: muscles are contractile organs. Through muscle contraction, these organs can perform a
number of important functions such as movement from the gross physical movements of our
skeleton (walking) to the more finely tuned intricate movements such as beating of the heart,
breathing, digestion and constriction of blood vessels.
Three types of muscle:
1. skeletal muscle
- help the human body move. Most skeletal is attached to bones via tendons
2. cardiac muscle
- found in heart. It contracts rhythmically and is modulated by neural activity and hormones.
3. smooth muscle
- controlled by the nervous system or hormones. It may be either generally inactive and then
respond to stimulation, or it may be rhythmic.
Characterization of muscle – characterized by morphology (form) or how they function
MORPHOLOGICAL CHARACTERIZATION – either striated or smooth
Striated
- Marked by both light and dark bands (striations)
- Found in the heart and skeletal muscles
- Characterized by long muscle fibres (cells) with multiple nuclei which are located
peripherally for skeletal muscle or centrally for cardiac muscle. Cardiac muscle also
features intercalated discs.
Smooth
- Found in blood vessels, the digestive system, and other viscera
- Unlike striated, each smooth muscle fibre (cell) contains a single centrally located
nucleus.
- Note: smooth muscle has fusiform-shaped cells without striations
FUNCTIONAL CHARACTERIZATION – voluntary or involuntary
Voluntary
- Consciously controlled in order to perform a specific function, such as the muscles that
move the skeleton for walking, reaching, talking etc.
- Type of muscle that s voluntarily controlled is skeletal muscles (muscles of the upper
limb)
Involuntary
- Not consciously controlled
- Consists of smooth muscle and cardiac muscle (e.g. muscles of the intestines (smooth)
and the heart (cardiac)
, Summary of muscle cell
Skeletal Cardiac Smooth
Appearance Striated Striated Not striated
Multinucleated Uni/binucleated Unnucleated
Long, cylindrical/rod branching Fusiform (wide in
middle, tapers off on
ends)
Location Attached to bone Heart Walls on hollow
organs (stomach,
esophagus, blood
vesicles)
Regulation Voluntary Involuntary Involuntary
(pacemaker (peristalsis)
How do muscles function? Two basic properties: excitability and contractility
Excitability – the ability of muscle tissue to receive and respond to electrical signals from nerves
or stimulation from hormones
Contractility – when a muscle cell is excited by a nerve or hormone, this causes the muscles to
shorten, resulting in contraction
SECTION 2: SKELETAL MUSCLE
Intro: attached to the bones of the skeletal system are about 700 named muscles that account
for roughly half of a person’s body weight. Each of these muscles is a discrete organ composed
of skeletal muscle tissue, epithelial, connective and nervous tissue.
Skeletal muscle contracts to move parts of the body. Most skeletal muscles are attached to two
bones across a joint, such that when contradicted the muscle brings parts of those two bones
closer to each other. Skeletal muscle functions to:
- Produce movement
- Maintain posture and stabilize joints
- Control excretion (elimination of urine and feces) and swallowing
- Produce heat
- Support and protect internal organs
Organization of skeletal muscle tissue
Consists of muscle tissues and connective tissue. Connective tissue surrounds the muscle tissue
and attaches the ends of each muscle to bone.
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