__________ gives the orders, and the ___________ carries them out
refers to muscle generally
specifically refers to muscle cells
Study of muscles
Inflammation of muscle tissue
Cytoplasm of a muscle cell at the cellular level
The cell shrinks
Increase in size due to an increase in the size of the cell.
Increase due to an increase in the number of cells
Cells change shape
Type of muscle that usually comes to mind when we hear the word muscle
Skeletal muscle is often referred to as
voluntary striated muscle
Well-defined organs composed of groups of skeletal muscle cells surrounded by a layer of fibrous connective tissue
Most muscles attach to bones at both ends by tough, fibrous connective tissue bands called
Broad sheets of fibrous connective tissue attach muscles to bones or to other muscles
The prominent aponeurosis that runs lengthwise between the muscles on the animal’s ventral midline. It connects muscle to muscle
linea alba (white line)
Muscle‘s attachment sites that is generally more stable than the other is called the _____ of the muscle.
The muscles attachment site that undergoes most of the movement when a muscle contracts is called the ________ of the muscle and is more distal on the appendage.
Used to describe a muscle or muscle group that directly produces a desire movement.
Prime Mover (agonist)
long head of the triceps and deep head of the triceps
a muscle or muscle group that directly opposes the action of a prime mover.
Biceps flexes the elbow and the Triceps extends the elbow
Muscle that contracts at the same time as a prime mover and assists it in carrying out its action.
Flexor muscle deep digital flexes digits of front limb and superficial digital flexor muscles aids in the movement
Muscle that stabilizes joints to allow other movements to take place.
muscle that flex the digits also can flex the carpus
6 Muscle Naming
Direction of fibers
Number of heads or divisions
A portion of the name is often related to its functions. Muscles that flex a joint are often called flexor muscles.
Reflects its distinctive shape such as the deltoid muscle. The term means triangular shaped and it is located in the shoulder region
Its physical location in the body.
biceps brachii muscle is located in the brachial region
Direction of fibers
The term rectus means straight. The rectus abdominis muscle are two strap like muscles on either side of the linea alba.
Number of heads or divisions:
The number of heads refers to the number of attachment sites that a muscle has to its origin.
bicep brachii muscle has 2heads, triceps brachii muscle has 3 heads.
Origin and insertion sites are used to name muscles.
sternocephalicus– origin is sternum insertion is back of the head (cephal)
Occur in the superficial fascia between the skin and the deep fascia covering the skeletal muscles. These muscles attach to the skin and are responsible for movement of the skin.
These muscles are thin and just serve to _____________
twitch the skin
Function of the abdominal muscles is to:
support the abdominal organs.
help flex (arch) the back
assist in various functions of straining
expulsion of feces (defecation)
expulsion of urine (urination)
expulsion of the newborn (parturition)
process of vomiting and regurgitation
Arrangement of Abdominal Muscles form the outside in:
A. external abdominal oblique muscle
B. internal abdominal oblique muscle
C. transversus abdominis muscle
D. rectus abdominis muscle
Fibers run in a caudo-ventral oblique direction
External Abdominal Muscle
Fibers run in a cranio-ventral oblique direction
Internal Abdominal Muscle
Form the floor of the muscular abdominal wall. It consist of two strap-like muscles on either side of the linea alba that run from the ribs and sternum back to the brim of the pubis.
Rectus Abdominis Muscle
Deepest of the abdominal muscles as its fibers run directly downward in a ventral direction to insert on the linea alba
Origin: 7-8 thoracic vertebrae and lumbar vertebrae
Action: Draws limb caudally; Flexes shoulder joint
4 Pectoral Muscles – involved that extend from the sternum to the humerus and act as adductors of the front leg, helping to keep the legs under the animals.
a. Descending superficial pectoralis
b. Transverse superficial pectoralis
c. Deep pectoral
Action: adductors of the front leg
2 heads of Deltoids
Spinodeltoid and Acromiodeltoid or deltoid muscle (acromial portion and spinous portion) – are triangular shaped and extends from the lateral portion of the scapula down to the humerus. These muscles abduct and flexes the shoulder joint.
Brachiocephalicus – this muscle has two heads:
a. cleidocephalicus – skull (origin) to clavicle tendon (insertion)
b. cleidobrachialis – clavicle tendon (origin) to humerus (insertion)
Action is to pull the limb forward and extend the shoulder
Origin: wing of atlas
Insertion: spine and scapula
Action: advance the limb
Which extrinsic thoracic muscle is not present in the horse
Trapezius – a very thin triangular muscle
Heads: Cervical and Thoracic part
Origin: Cervical = atlas Thoracic = thorax.
Insertion: Spine of scapula
Action: Elevates and abduct the forelimb
Rhomboideus – holds the dorsal border of the scapula close to the body. This muscle has three heads with a common insertion.
a. Rhomboideus capitis – origin occipital bone
b. Rhomboideus cervicis – origin spinous process of cervical vertebrae
c. Rhomboideus thoracis – origin spinous process of thoracic vertebrae
Action: elevate forelimb
Serratus ventralis – this muscle acts like a sling to support the body between the forelegs. This muscle has two heads.
Origin: cervical vertebrae
Action: support the trunk
The most powerful of the chewing muscles in the cheek area?
Two of the main muscles that extend the head and neck are the
splenius and trapezius
Muscle that extends the head and neck and also pulls the front leg forward is the
The sternocephalic muscle is a smaller, straplike muscle that extends from the sternum to the base of the skull and acts to
flex the head and neck
Masseter muscle – This muscle makes up the cheek region of the cat and consists of three layers whose layers run in three different directions.
Origin: zygomatic arch
Insertion: lateral side of mandible
Action: elevate mandible when chewing
Temporalis muscle - This muscle is the largest muscle on the head and is found on the lateral and dorsal aspects of the skull.
Origin: parietal bone, temporal, frontal and occipital.
Insertion: coronoid process of mandible
Action: elevate mandible for chewing and moves the mandible laterally
Sternocephalicus - this muscle has two heads & the major importance of this muscle is that it forms along with the brachiocephalicus and borders the jugular groove.
Insertion: occipital bone
Action: flex and draws the head and the neck to the side
Platysma – the major cutaneous muscle of the neck and head.
Origin: tissue on the spinous process of the cervical vertebrae
Insertion: fibers around the lips
Action: to draw the commissures of the lips caudally.
Contracting of the platysma at the point of euthanasia is called
What muscle is important for the horse to be able to quiver to get fly’s off neck.
2 Heads: acromiodeltoid and spinodeltoid join and act together. The spinodeltoid portion covers a majority of the infraspinatus muscle located below it. The two heads fuse before insertion.
Origin: spine and acromion of scapula
Insertion: deltoid tuberosity of the humerus
Action: flexes the shoulder
Origin: infraspinous fossa of scapula
Insertion: greater tuberosity of the humerus
Action: flexes the shoulder joint and abducts the limb at the shoulder
Supraspinatus muscle – A large part of this muscle is covered by the trapezius and the omotransversarius.
Origin: supraspinous fossa
Insertion: greater tuberosity of the humerus
Action: extends the shoulder joint
Subscapularis muscle –
Origin: subscapular fossa of the scapula
Insertion: lesser tuberosity of the humerus
Action: adducts the limb at the shoulder and rotates the leg medially
Teres major muscle – lies caudal to the Subscapularis muscle, and its tendon of insertion joins that of the latissimus dorsi muscle.
Origin: caudal border of the scapula
Insertion: Teres major tuberosity of the humerus
Action: flexes the shoulder
Biceps Brachii muscle – this muscle is located on the craniomedial aspect of the humerus. It has only one head in animals.
Origin: supraglenoid tubercle of scapula
Insertion: ulnar and radial tuberosities
Action: flexes the elbow and extends the shoulder
Brachialis muscle – is located on the lateral side of the humerus. It twists laterally and cranially toward its insertion site.
Insertion: ulnar and radial tuberosities
Action: flexes the elbow
Triceps Brachii muscle – this mass is on the caudal aspect of the humerus. It is made up of three heads (long, medial, and lateral)
Origin: long from scapula and the others from the proximal border of the humerus
Insertion: all four on the olecranon of the ulna
Action: extends the elbow and flexes the shoulder
Muscles distal to the elbow joint are an important collection of carpal and digital _____ and ___________ that play important roles in locomotion.
The two primary antagonistic and most common antagonist are a set of muscles in the pelvic limb is the
Quads and the Hamstrings
The large gluteal muscles (gluteus medius and gluteus maximus) and the hamstring muscle group are ________ muscles of the hip joint.
The largest peripheral nerve in the body serves the entire back leg
Hamstring Muscles – name the three muscles located on the back of the thigh region:
Note: these extend the hip joint and are also the main __________ of the stifle joint.
Biceps femoris muscle
Quadriceps Femoris Muscle name the four muscles. This Group of muscles are located on the front of the hind legs.
Tensor Fasciae Latae – this is a triangular muscle that aponeurosis into a long – thin but wide tendon (the fasciae latae)
Origin: wing of the ilium
Insertion: lateral femoral fascia
Action: flexes the hip joint and extends stifle
Commonly used by surgeons to make cuts and strips to replace the anterior cruciate ligaments during repair.
Superficial Gluteal muscle – this small triangular muscle lies over the middle gluteal muscle.
Origin: sacrum and coccygeal vertebrae
Insertion: greater trochanter of femur
Action: abducts the limb and extends the hip
Middle Gluteal muscle – a large egg-shaped muscle lies cranial to the superficial and caudal to the tensor fascia latae.
Origin: lateral ilium
Insertion: greater trochanter of femur
Action: abducts the limb and extends hip
Deep Gluteal muscle – the fan-shaped muscle is totally covered by the middle gluteal.
Origin: body of ilium and ischiatic spine
Insertion: greater trochanter
Action: abducts and extends hip
Biceps Femoris muscle – the longest and widest muscle of the thigh and covers its entire caudolateral aspect.
Origin: ischiatic tuberosity of the pelvis
Insertion: patella, proximal tibia, and tuber calcanei
Action: extends hip & tarsal joint, flexes stifle
Semitendinosus muscle – lies medial to the Biceps femoris and lateral to the Semimembranosus.
Origin: ischiatic tuberosity
Insertion: tibia and tuber calcanei
Action: extends the hip & tarsal joint, flexes the stifle
A thin, dome-shaped sheet of muscle that separates the thoracic cavity from the abdominal cavity. The convex surface of its dome shape protrudes into the thoracic cavity. When it contracts, it flattens out somewhat. This pushes the abdominal organs caudally
The fibers are directed in an oblique direction so that they contract, they rotate the ribs upward and forward. This increases the size of the thoracic cavity and causes air to be drawn into the lungs.
External Intercostal Muscle
Two sets of expiratory muscles that aid the process are
Internal Intercostal Muscles
Fibers of these muscles run at right angles to those of the external intercostal muscles. When these contract, they rotate the ribs backward, which decreases the size of the thorax and pushes air out of the lungs
Internal Intercostal Muscles
Four heads simply contract reducing the space of the peritoneal cavity
What is the sequence of muscle contraction
Muscle, muscle fiber, myofibril, myofilament, sarcomeres, Z bands, actin and myosin filaments.
A system common to skeletal muscles only allow for the transport of impulses and nutrients from outside the muscle down to the protein filaments. ___________ extend from the sarcolemma down to the protein filaments
Transverse or T tubules
The myofibrils that make up the muscle fiber (cell) are composed of thousands of tiny, contractile protein filaments known as
the actin filaments and myosin filaments
The area from one Z Line to the next Z Line is called a ________ and is the basic contraction unit of skeletal muscle
When all the sarcomeres of each myofibril is stimulated to contract, they will contract to
½ their normal length
Atrophy of the supraspinous and infraspinous muscles due to trauma to the suprascapular nerve. Common injury due to cowboy spurs
The sites where the ends of motor nerve fibers connect to muscle fibers are called
When an animal is starving and no longer has carbohydrates to break down polysaccharides, disaccharides monosaccharides etc. it goes to fat. Causes the body to breakdown fat and
muscle to glucose 6 phosphate for energy. This is referred to as __________. When you breakdown muscle and fat down, the by product is called ________.
Nerves that stimulate the spinal muscles and use acetylcholine are
cranial nerves, spinal nerves, and parasympathetic nerves
Within the end of the nerve fiber in a neuromuscular junction are tiny sacs called _________ that contain the chemical neurotransmitter acetylcholine. When a nerve impulse comes down the fiber, it causes the release of acetylcholine, which diffuses across the synaptic space and binds (attaches) to receptors on the _________. This ultimately starts the process that leads to the contraction of the muscle fiber.
Term to describe one nerve fiber and all the muscle fibers it innervates.
Each individual skeletal muscle fiber is surrounded by a delicate connective tissue layer composed of fine, reticular fibers called the
Groups of skeletal muscle fibers, called
fascicles, are bound together by a tougher connective tissue layer, called the _______, which is composed of reticular fibers and thick collagen fibers.
Groups of muscle fascicles are surrounded by ___________, a fibrous connective tissue layer composed largely of tough collagen fibers
The impulse travels along the sarcolemma and through the T tubules to the interior of the cell. When the impulse reaches the _______, it causes the release of stored calcium ions into the ________. As the Ca++ diffuses into the myofibrils, it turns on the contraction process, which is powered by high-energy molecules of __________.
adenosine triphosphate (ATP).
ATP when it is released becomes _____ and must pick up a phosphate. ADP in the presence of ______ and with ________ will convert ADP to ATP. Glucose and oxygen are necessary for the production of __________.
adenosine diphosphate (ADP)
glucose and oxygen
A catalyst which assists in the reconstitution of ATP
The presence of ATP is required for
1. relaxation, or detachment of the myosin from the actin
2. for the return of calcium ions to the sarcoplasmic reticulum
When the fiber is stimulated to contract, small levers on the myosin filaments, called _____________, ratchet back and forth and pull the actin filaments on both sides toward the center of the myosin filaments
cross bridges or ratchets
An individual muscle fiber either contracts completely when it receives a nerve impulse or it does not contract at all. This is known as the ___________. The number of muscle fibers stimulated to contract is controlled by the _________.
A single muscle fiber contraction is called a
A single muscle fiber contraction/a twitch contraction can be divided into three phases:
Latent phase is the brief hesitation between the nerve stimulus and the beginning of the actual contraction. It lasts 0.01 seconds
Contraction phase = 0.04 seconds
Relaxation phase = 0.05 seconds
Muscle shortening can occur in the absence of action potentials is referred to as
rigor or physiologic contracture
Contracture that occurs after death is referred to as
Contraction strength varies and is achieved by
1. multiple motor unit summation or
2. wave summation
The summation of one motor unit causes a weak contraction, whereas the stimulation of a large number of motor units develops a strong contraction. This is known as motor unit summation. All gradations of contraction strength are possible, depending on the number of motor units stimulated
Multiple Motor Unit Summation
Increasing the strength of contraction by this summation occurs when the frequency of contraction is increased. When a muscle is stimulated to contract before the muscle has relaxed, the strength of the subsequent contraction is increased
When the frequency is sufficient such that the individual muscle twitches become fused into a single prolonged contraction, the strength is at a maximum; this condition is known as
Tetanus is a _____ disease caused by a potent neurotoxin known as ______ elaborated by the organism ________. The neurotoxin reaches the CNS and prevents release of an inhibitory transmitter (glycine). The resulting sensitivity to excitatory impulses, unchecked by inhibitory impulses, produces generalized muscular spasms (tetany).
Soliped that is most susceptible to Clostridium?
Animal least susceptible is the
Muscle seems to “warm up” to a maximum contraction state. This can be shown by applying stimuli of equal intensity a few seconds apart to muscle. Each successive muscle twitch has slightly more strength that the previous one, until optimal contraction strength is reached. Successive stimulations are believed to provide for an increasing concentration of calcium ions in the sarcoplasm during the beginning contractions of rested muscles
Treppe or the staircase phenomenon
The immediate energy source that powers the sliding of the actin and myosin filaments is the compound ATP, which is produced by the many ___________in muscle fibers
Glucose is stored in the Muscle fibers in the form of glycogen, and oxygen is stored attached to large protein molecules called
Glucose is stored as
Oxygen attaches to large protein molecules called
As long as the oxygen supply is adequate to keep up with the energy needs of the muscle
During periods of strenuous activity, the need for oxygen exceeds the available supply and muscle fibers must shift to what is called _______ to produce energy required for continued activities. It should be mentioned that this type of metabolism is not as efficient as aerobic metabolism and results in ___________ as a byproduct of incomplete glucose breakdown.
lactic acid formation
A considerable amount of the energy produced in muscles is lost in the form of
If heat production exceeds body needs, the excess must be eliminated by mechanisms such as
panting or sweating
Under cold conditions, the body may need to increase the production of heat to avoid hypothermia. It often does this by producing the small, spasmodic muscle contractions we know as
Cardiac Muscle - Also known as
Involuntary Striated Muscle
cardiac muscle cells form elaborate networks around the
The firm end-to-end attachments sites between cardiac muscle cells are called
2 unique and important things about cardiac muscle:
1. It contracts without the external stimulation
2. Groups of cardiac muscle cells adopt the contraction rate of the most rapid cell in the group
The impulse that starts each heart beat begins
in the ________ (Common name heart’s ________), located in the ___________.
sinoatrial (SA) node
wall of the right atrium
The sympathetic fibers stimulate the heart to
beat harder and faster as part of the “fight or flight response” that kicks in when an animal fells threatened
The parasympathetics fibers
inhibit cardiac function, thereby causing the heart to beat more slowly and with less force when the body is relaxed and resting.
Smooth Muscle - also called
Non-striated involuntary muscle
smooth muscle is found in two main forms:
1. Visceral smooth muscle
2. multiunit smooth muscle
Because their contractile units are not organized into regular, parallel sarcomeres, individual smooth muscle cells can shorten to
a greater extent than skeletal or cardiac muscle cells
Visceral smooth muscle is found in the walls of many soft, internal organs, which are also known by the general name _______. Its cells are linked to form large sheets in the walls of organs such as the
stomach, intestine, uterus, and urinary bladder
Sympathetic stimulation _______ visceral smooth muscle activity, and parasympathetic stimulation ______ it
Small and delicate, this muscle is made up of individual smooth muscle cells or small
groups of cells. They require impulses from _______ nerves to contract
multiunit smooth muscle
Pupil is contacted
Pupil is dilatated
E & G
External Abdominal Oblique
Hamstring Group - Semimembranosus, Semitendinosus
Name 2 heads of the sternocephalicus muscle
What 2 muscles form along the jugular groove?
When you give an injection it is between what two muscles
What muscle is located over the radius and is used to extend the carpus?
Extensor Carpi Radialis
When does the cardiac muscle start contracting?
early in the embryonic period
What is the difference between cardiac and skeletal muscle?
Cardiac muscle is smaller than skeletal and have only one nucleus per cell.
Origin: Occipital and temporal bone
Insertion: Ventral mandible
Action: Opens the mouth
Origin: Medial surface of mandible
Insertion: Ventral median raphe between bones of mandible
Action: Raises the floor of the mouth.