Name ______
Muscle Rules - 60 Informal Points
Introduction
All movement in the human body, from wiggling a toe or swimming a mile to eating and digesting a sandwich, is the result of muscle action. In previous lessons, you have learned about connective and nervous tissue. In this unit, you will explore the structure and function of another incredible tissue-- themuscle.
When we think of muscles, we usually focus on the muscles that move our bones and allow us to move about the Earth; the tissues we see from the outside. But inside the amazing human, you will find other types of muscle tissue that work silently to move substances around the body. Your heart keeps beating and your food continues to digest even when you fall fast asleep and close your conscious mind for the day. Without muscle moving blood or distributing nutrients from food, the human machine would power down.
There are 206 bones in the human body, but over 600 skeletal musclesallow our bodies to move in different directions. Over sixty of these muscles are found in your face alone. You use forty of these muscles every time you frown, but only twenty muscles when you smile. The human body is even built to make it easier to be happy than to be sad.
Skeletal muscles are attached to bones with tough cords or sheets called tendons and these bones meet other bones at junctions called joints. The contraction or shortening of muscles pulls on bone and moves the body.
In this activity, you will observe and compare the structure and function of the three types of muscle tissue.You will explore the structure of skeletal muscle both by looking at slides and by creating a model of a muscle unit. Before you move on to building actual muscle groups, a series of demonstrations will help you see that the placement of muscles on bones follows specific patterns and rules. These rules will later help you construct specific muscle groups on your Maniken®.
Procedure
Part I- Types of Muscle Tissue
- Research the three types of muscle tissue:skeletal muscle, smooth muscle and cardiac muscle. Fill in the table below.
Muscle Type / Description
Skeletal / A form of striatedmuscletissue which is under the voluntary control of the somatic nervous system. Mostskeletal musclesare attached to bones by tendons.
Smooth / Smooth musclegenerally forms the supporting tissue of blood vessels and hollow internal organs, such as the stomach, intestine, and bladder.
Smooth muscle is involuntary not striated.
Cardiac / Cardiac muscle(heartmuscle) is involuntary and striated.
- Fill in the table below to describe what it means if a muscle is striated and what it means if a muscle is said to be under voluntary control.
Striated Muscle / Voluntary Control
Skeletalorvoluntarymuscleinwhichcross-striationsoccurinthefibersasaresultof
regularoverlappingofthickandthinmyofilaments
Musclesare composed of two major protein filaments: a thick filament composed of the protein myosin and a thin filament composed of the protein actin.Musclecontraction occurs when these filaments slide over one another in a series of repetitive events. / Musclewhose action is normally controlled by an individual's will; mainly skeletalmuscle, composed of parallel bundles of striated, multinucleate fibers.
- Use information from your research to fill in the chart below.Leave the histology box blank until you begin your microscope work.
Type of muscle / Striations?
(Y/N) / Voluntary?
(Y/N) / Location in
Body / Function in
Body / Histology
Skeletal Muscle / yes / yes / Attached to
bones / Movement,
Heat,
Posture / See pic below
Smooth Muscle / no / no / Lines blood
vessels and
hollow
internal
organs,
such
as the
stomach,
intestine,
and bladder / Movement of
Blood
Through
Vessels,
Food through
Digestive
system
Cardiac Muscle / yes / no / heart / Heart
contractions
- Use a microscope to viewa prepared slide of each type of muscle tissue under both high and low power. Using colored pencils, draw what you see under high power in the histology column of your table. Use a reliable website to help you label what you see.
Part II: Building Muscle
In Lesson 1 of this unit, you looked at the function of joints. Joints work together with skeletal muscle to move the human body. In the remainder of Lesson 2, you will focus on the structure of skeletal muscles, build these muscles on your Maniken®, and visualize the amazing ability of skeletal muscle to contact and shorten. But before we look at function, let’s explore structure.
- Follow your teacher’s instructions to build a pencil muscle.
- As you unwrap the muscle and return a fascicle, or group of muscle fibers to each group, review key vocabulary words.
- In the space below, draw a diagram of a skeletal muscle. The following components should be labeled and identified.
Things to Label / Muscle Drawing
-Endomysium
-Epimysium
-Perimysium
-Fascicle
-Tendon
-Muscle Fiber(Myofibril) /
Part III: Muscle Rules
Now that you have learned about muscle structure, let’s start to think about function.
- We know what muscles help our skeletal system move, but how are these tissues oriented on our bodies?
- What are the rules that muscle live by?
Rule #1: Muscles must have at least two attachments and must cross at least one joint.
Rule #2: Muscles always “pull” and get shorter.
Rule #3: The attachment that moves is known as the insertion and the attachment that remains stationary is known as the origin.
Rule #4: Muscles that decrease the angle between ventral surfaces of the body are known as flexors. Muscles that increase the angle between ventral surfaces of the body are known as extensors.
Rule #5: Muscles work in opposing pairs.
Rule #6: Muscle striations point to the attachments and show the direction of pull.
- Follow your teacher’s instruction to build two simple muscles on the arm of your model.
- As you work through each step of the process, write each muscle rule in the space below. Add notes or examples to help you remember the concept.
(BE SURE TO STUDY THE MANIKEN BUILD PACKET BECAUSE YOU WILL NEED TO KNOW ALL INFORMATION ABOUT BOTH BRACHIALIS AND BRACHII.)
Rule #1: Muscles must have at least two attachments and must cross at least one joint.
Ex. Brachialis Muscle
- Origin = halfway down the humerus (both medial and lateral of the radial groove)
- Insertion = proximal ulna
- Crosses the elbow joint
Rule #2: Muscles always “pull” and get shorter.
Ex. As you flex your arm, the brachialis muscle pulls you lower arm up as the muscle contracts and gets shorter.
Rule #3: The attachment that moves is known as the insertion and the attachment that remains stationary is known as the origin.
Ex. Brachialis Muscle
- Origin = halfway down the humerus (both medial and lateral of the radial groove) [Stationary]
- Insertion = proximal ulna [Movable]
Rule #4: Muscles that decrease the angle between ventral surfaces of the body are known as flexors. Muscles that increase the angle between ventral surfaces of the body are known as extensors.
As you flex your arm you use your brachialis muscle, which is a flexor. A straight arm starts at 180o, but as you flex it the angle gets smaller and smaller. As you extend your arm you use your brachii muscle, which is an extensor. A flexed arm has small angle, but as you extend it, it straightens out to 180o.
Rule #5: Muscles work in opposing pairs.
Brachialis and Brachii are an opposing pair since Brachialis is a flexor and brachii is an extensor. They are opposing pairs since they cause the arm to move in opposite directions.
Rule #6: Muscle striations point to the attachments and show the direction of pull.
Long stringy lines that extend from one point of attachment to the other, but become narrower near the point of origin since the bone will be pulled towards the point of origin.
- Note that the name of a muscle gives you clues about the makeup of that muscle. Each muscle is given a Latin name based on one or more of its features. Take a look at the following muscle names and brainstorm what you can tell about these muscles simply by their names. Analyze specific words in the name, roots in the name and relationships to bones you have already studied. Each pair of muscles represents a different way in which muscles can be named. Describe the muscle feature that is being used in each naming scenario. For example, you have probably figured out that trapezius and rhomboids are named for their shapes. The trapezius muscle is shaped like a trapezoid and the rhomboids are shaped like rhombuses. See if you can find a pattern in the remaining pairs.
Muscles / Feature used in naming these muscles / Pictures
Trapezius and Rhomboid minor / Classification by Shape:
Trapezius is shaped like a trapezoid
A rhomboid is shaped like a rhombus
Gluteus maximus and Gluteus minimus / Classification by Size:
Gluteus maximus is the largest muscle in the group
Gluteus minimus is the smallest in the group
Frontalis and Temporalis / Classification by location in the body:
Frontalis is located on the frontal bone of the skull
Temporalis is located on the temporal bone of the skull
Orbicularis Oculi and Transverse abdominis / Classification by direction of fibers:
Fibers in orbicularis oculi form a circle
Fibers in transverse abdominis “traverse” or go across the
abdomen
Flexor Carpi Ulnaris and Extensor digitorum longus / Classification by action:
Flexor carpi ulnaris flexes the hand at the wrist
Extensor digitorium longus extends the foot and toes upward
SternoCleidomastoid and Brachioradialis / Classification by origin and insertion:
Sternocleidomastoid has origins on the breastbone (sternum)
and the collare bone (clavicle or “cleido”) and insertions of the
mastoid process of the skull’s temporal bone
Brachioradialus has an origin on the brachium or arm and an insertion on the radius
Biceps Brachii and TricpsBrachii / Classification by number of origins:
Biceps brachii has two origins on the scapula
Triceps brachii has three origins on the humerus
Conclusion Questions
- Describe the differences you see in the three types of muscle tissues.
Skeletal muscle is striated and looks like long fibers. Cardiac muscle is striated and has visible nuclei. Smooth muscle is non-striated and has a wave type structure with visible nuclei.
- What does it mean when we say a muscle contracts involuntarily? Describe one body function that is linked to an involuntary muscle contraction.
Involuntary muscle contraction is when muscles contract without a conscious effort, like the heart beating or digestion of food for example.
- Describe how the structural makeup of a muscle contributes to the muscle’s ability to do its job.
A muscles structure consists of connective tissue and muscle fibers, which work like a rope or rubber band to stretch and contract. The connective tissues’ elasticity helps to ensure that the tension developed by the muscle is smoothly transmitted and that a muscle will return to its original shape after being stretched.
- Using your knowledge of tissues, what type of tissue do you think makes up the three layers of membrane you encountered in your muscle?
They are made of smooth muscle connective tissue because its function is to surrounds muscle fibers and fascicles, connecting them and helpingthem retain shape.
- Explain how you know which attachment of a muscle is the origin and which attachment is the insertion.
The insertion of the muscle is the end of the muscle attaching to the freely moving bone. The origin of the muscle is the end of the muscle attaching to the fixed, non-moving bone.
- Your mom comes back from the doctor and says she has pulled her tibialis anterior. She knows you are taking Human Body Systems and asks you to tell her about her injury. Based on the classroom discussion, what can you deduce about this muscle?
She has injured the muscle on the backside of her tibia. This muscle acts to dorsiflex and invert the foot.
- When you are cold, your muscles begin to contract involuntarily and cause you to shiver. Why do you think this occurs? How does the contraction of muscles help the body maintain homeostasis?
Shivering causes you to involuntary contract and relaxes your muscles which will increase heat production, keeping the body at a stable 98.6oF.