Musculoskeletal System (copy)

What are the 2 types of skeletons?

Exoskeletons and endoskeletons

What are endoskeletons and exoskeletons?

Endoskeletons are internal skeletons

Exoskeletons are external skeletons

What are the 3 functions of the skeleton?

Locomotion

Protection of vital organs

Ensuring the appropriate size and shape of the organism

What are exoskeletons made of?

Chitin, which is extremely resistant to tear

What are endoskeletons made of and how does the composition differ by age?

Roughly 50/50 mix of Ca3(PO4)2 - calcium phosphate - and proteins

Kids —> More flexible (more protein)

Elderly —> Hard, brittle (more calcium phosphate)

How many bones do newborn babies have, and what happens to them during childhood?

Newborn babies have 270 bones, but during childhood many bones fuse together

How many bones do adults have and what does it mean for flexibility?

Approximately 210 bones

Naturally, there is less flexibility than young children

What is osteoporosis?

Bones become weak, brittle, and porous

Lack of calcium phosphate

Caused by an increase in bone resorption and/or a decrease in bone formation

What is locomotion?

The ability to move from place to place

What are 5 reasons for animal locomotion?

Foraging for food

Escaping danger

Searching for a mate

Migration

Dispersal

What is an example of foraging for food?

Honey bees flying from flower to flower to collect nectar and pollen (which is converted into honey)

What is an example of escaping danger?

Flying fish escape predators by swimming fast and extending long pectoral fins to glide over the water

What is an example of searching for a mate?

Loggerhead sea turtle - both males and females swim back to the beach where they were hatched to mate and lay eggs

What is an example of migration?

Arctic tern migrating from their Arctic breeding grounds to the Antarctic regions and back each year, to take advantage of available food

What is an example of dispersal?

Hoary bat - North American populations have established permanent colonies on the Hawaiian islands

How is movement universal to both motile and sessile organisms?

Motile organisms have adaptations allowing movement

Sessile organisms alter body form in response to environmental stimuli

What is an example of a sessile organism?

Venus flytrap, which waits for an insect to crawl or fly inside its paired leaves, triggering the hairs, which closes the leaves around the prey animal

What is an example of a motile organism?

Brown-throated three-toed sloth,, very slow-moving mammal. Three long toes on each foot that, in combination with their bone structure and musculatures, are adapted to hanging from branches and moving using a pulling motion (movement on ground is impossible)

What is the difference between vertebrates and arthropods (endoskeletons vs exoskeletons)?

Vertebrates attach muscles to the outside of the bones of their endoskeleton

Arthropods attach muscle to the inside of their chitinous exoskeleton

What is a lever and what is its purpose?

A rod (bone) able to rotate about a fixed point known as a fulcrum (a joint)

How does the nodding motion of your head work?

Attachment point of the cranium to the vertebrae acts as a fulcrum

One set of muscles contracts to bring the head down from the fulcrum point and another set brings it back up

How do muscles and bones of the arm use the elbow as a fulcrum when the forearm is used to lift objects? (DIAGRAM)

Bicep contracts and triceps relaxes — forearm moves up

Triceps contracts and biceps relaxes, arm straightens

What does it mean for muscles to work as antagonistic pairs?

As one muscle contracts, the other muscle relaxes or lengthens

One muscle of the pair contracts to move the body part, while the other muscle in the pair contracts to return the body part back to the original position

How do arthropods, with their exoskeletons, take full advantage of leverage?

Arthropods have jointed body parts

The muscles that attach to the inside of chitin are in antagonistic pairs, just as in animals with endoskeletons

Diagrams of bones of the endoskeleton of ahuman vs segments of the exoskeleton of an insect

Similar in function and even share some anatomical names

What are synovial joints and some examples?

Synovial joints occur in the body where 2 bones need to move against each other

Notable for the wide range of motions that they allow

Common examples: joints at your elbow, knee, shoulder, and hips

What is the function of the pelvis and femur?

Bones forming the ball-and-socket joint of the hip

What is the function of cartilage?

Smooth protective connective tissue that lines both the pelvis and femur within the hip joint

What is the function of synovial fluid?

Lubricating fluid within the hip joint that reduces friction

What is the function of ligaments?

Tough connective tissue that holds the bones of the hip joint in place

What is the function of tendons?

Generally, connective tissue that attach muscles to two bones, one at each end of the muscle

What is the function of muscles?

Muscle tissues that contract and relax to enable movement of the femur within the socket of the pelvis

What is a goniometer?

Measure range of motion of a joint (the distance and direction a joint can move, usually measured in degrees)

What is the origin?

One bone that acts as an immovable anchor

What is the insertion?

One bone that moves as a result of muscle contraction

What is the insertion of the biceps vs triceps?

Biceps - Radius

Triceps - ulna

Why are two muscles required for a movement?

A muscle can only exert a force when it contracts

So, once a bone have been moved, the opposite movement requires a different muscle

What is titin and what is its function?

Largest known protein in the human body

Has multiple folds that allows it to act as a spring

Its spring-like action helps with relaxation

Diagram of a relaxed sarcomere

• Actin

• Myosin

• Titin

• Z line

What happens to a sarcomere during contraction?

Sarcomeres shorten during contraction

The two sides of each sarcomere move towards the centre (Z lines)

What happens to titin during contraction?

Contraction creates a spring-like tension in titin, that is released when the muscle relaxes

Allows each sarcomere of the muscle to undergo a contraction once again

What is the structural function of titin?

Holds myosin fibres in place in the sarcomere and prevents muscle fibres from overstretching

What is an example of an antagonistic pair of muscles in the respiratory system?

The paired muscles known as the intercostals located between the ribs

What are the origin and insertion points of the intercostal muscles?

Intercostal muscles lie between each pair of ribs and use the ribs as their origin and insertion points

Describe the location of external intercostal muscles and their origin and insertion points.

Outermost intercostal muscles are the external intercostal muscles

Origin and insertion points on each pair of ribs lie at an angle

Origin - the rib above

Insertion - the rib below

Describe the location of internal intercostal muscles and their origin and insertion

Beneath are the internal intercostal muscles

They lie at an angle almost opposite that of the external set

Origin - the rib below

Insertion - the rib above

Orientation of the muscle fibres of the external and intercostal muscles (DIAGRAM)

Why do the orientations of the internal and external intercostal muscles differ?

Different orientations encourage stretching of the titin fibres in the layer not currently contracting

For example, when the external intercostal muscles contract, the expansion of the ribcage results in stretching of the internal intercostal muscles

This stretches the titin fibres in each sarcomere of this muscle layer, creating potential energy that will be used for the next contraction of the internal intercostal muscles

What is the fulcrum point of both sets of muscles?

The attachment of the ribs to the vertebrae

What happens when the external intercostal muscles contract?

The rib cage is pulled upwards and out, which happens during inspiration

What happens when the antagonistic internal intercostal muscles contract?

Move the ribcage down and inwards during expiration

How are skeletal muscle contractions controlled?

The control of the nervous system

What are neuromuscular junctions?

This is a type of synapse where a chemical message is sent into the muscular tissue to stimulate a contraction

What are motor neurons?

Neurons that carry the messages to the muscular tissue to stimulate a contraction

What does the intensity of contraction of a muscle depend on?

Depends on how many of the total muscle fibres within the muscle receive a nervous system impulse to contract

What is a motor unit?

A set number of muscle fibres that is controlled by a single motor neuron + the motor neuron

What happens if a low intensity contraction is needed, versus when a high intensity contraction is needed

Low intensity - a relatively low number of motor units is activated by the brain

High intensity - more motor units receive impulses

What is the ratio of motor neurons to muscle fibres? (DIAGRAM)

Varies from about 1:10 to 1:200

What happens when your brain predicts a greater force of contraction than is necessary for a particular motion?

More motor units were activated than you really needed. Until you feel the mass of the object you are moving, lifting motion is awkward.

How many sarcomeres are in a bicep?

The bicep contains hundreds of thousands of sarcomeres

What is each muscle composed of?

Thousands of cells called muscle fibres because of their elongated shape

Why are muscle fibres multinucleate?

Each fibre represents several cells that have merged together

What are myofibrils?

Protein filaments that compose muscle fibres

Run parallel to each other

Sequentially placed along each myofibril are contracting units called sarcomeres

Diagram of myofibril

DIAGRAM: Muscle tissue showing an extended myofibril running parallel to several others

Z lines are located in the centre of the longer, lighter shaded areas of a sarcomere (lighter because it only has one protein, actin present)

Centrally located between Z lines are a shorter, lighter area, where only myosin is located

Dark areas represent the presence of both actina nd myosin

Why are skeletal muscles sometimes referred to as striated muscle?

Each myofibril shows the striations typical of a skeletal muscle

The striations are the result of alternating fibres of two proteins called myosin and actin

What happens since all sarcomeres are attached to each other end to end? (DIAGRAM)

When one sarcomere contracts, all the sarcomeres in the same muscle contract

The resulting action makes the muscle fibre and the entire muscle shorter

How many sarcomeres share each Z line, and what is the significance of this?

Each Z line is shared by 2 sarcomeres, one to the right of the Z line and one to the left

This allows muscle fibres to contract as a unit and shorten the entire muscle

What is the sliding filament theory?

When sarcomeres contract, the actin filaments slide over the myosin fibres

This results in each sarcomere shortening

What is the process of neuron signalling (sodium and calcium) on muscle cells?

When action potential reaches the axon, acetylcholine is released

Acetylcholine binds to postsynaptic receptors, which opens sodium channels

Influx of sodium depolarizes the muscle fibre

Release of calcium ions from sarcoplasmic reticulum of muscle cells

Calcium uncovers the binding sites on actin

What are the steps of sliding filament theory? (DIAGRAM)

1. Myosin heads are activated by splitting ATP (HYDROLYSIS). This causes a change in the position of the heads

2. Myosin heads are attracted to and attached to exposed binding sites of actin to form cross-bridges. Inorganic phosphate is released

3. As myosin forms cross-bridges, ADP is released and the myosin bends due to loss of energy. The bending is towards the centre of the sarcomere and the actin is moved inwards

   1. Compresses the titin

4. Myosin binds to ATP and this allows detachment of the myosin heads from the actin attachment sites

What does a sarcomere look like relaxed vs contracted?

Z lines in the contracted sarcomere are close together after contraction

What is rigor mortis?

Animal bodies, including humans, become very rigid a few hours after death

Why does rigor mortis occur?

Result of no new ATP being generated after death, and thus the myosin heads cannot detach from the actin-binding sites

Rigor mortis starts to decrease about 36 hours after death as the proteins degenerate

What are 3 adaptations of marine mammals for swimming?

Streamlined body, allowing animal to move through viscous water with ease

Adaptations of limbs to form flippers and of the tail to form a fluke with up-and-down movement

Changes to airways to allow periodic breathing between dives (ex. blowhole)