HL Human Physiology: 11.2 Movement Flashcards
The ability to move is controlled by a number of interacting body systems, including:
Skeletal system – consists of bones that act as levers and provide a structure for the muscles to pull
Muscular system – muscles deliver the force required to move one bone in relation to another
Nervous system – delivers signals to the muscles which cause them to contract and create movement
What are skeletons and outlines the types
Skeletons are a rigid framework that function to provide support and protection for body organs
Skeletons can be internal (endoskeletons) to support their bodies from the inside with tissues surrounding the bone
Skeletons can be external (exoskeletons) which are found on the outside of the organism to protect the internal tissues
Endoskeletons typically consist of numerous bones, while exoskeletons are comprised of connected segments
What do skeletons facilitate and mention the connections involved
Skeletons provide a surface for muscle attachment and thus facilitate the movement of an organism
Bones and exoskeletons act as levers, moving in response to muscular contraction
Bones are connected to other bones by ligaments, and bones are connected to muscles by tendons
What are synovial joints?
Synovial joints are capsules that surround the articulating surfaces of two bones (i.e. where the bones connect)
Joints function to maintain structural stability by allowing certain movements but not others
Synovial joints consist of three main components:
Joint capsule – Seals the joint space and provides stability by restricting the range of possible movements
Cartilage – Lines the bone surface to facilitate smoother movement, as well as absorbing shock and distributing load
Synovial fluid – Provides oxygen and nutrition to the cartilage, as well as lubrication (reduces friction)
How many types of synovial joints are there
There are six main types of synovial joints that allow for different ranges of movement, which are (in order of mobility):
Plane joints (least mobility), hinge joints, pivot joints, condyloid joints, saddle joints, ball and socket joints (most mobility)
Discuss the human elbow as an example of hinge joint
Cartilage- Reduces friction and absorbs compression
Synovial fluid- Lubricates to reduce friction and provides nutrients to the cells of the cartilage
Joint capsule- Surrounds the joint, encloses the synovial cavity, and unites the connecting bones
Tendons- Attach muscle to bone
Ligaments -Connect bone to bone
Biceps muscle- Contracts to bring about flexion (bending) of the arm
Triceps muscle- Contracts to cause extension (straightening) of the arm
Humerus- Acts as a lever that allows anchorage of the muscles of the elbow
Radius- Acts as a lever for the biceps muscle
Ulna- Acts as a lever for the triceps muscle
Explain the antagonistic pair of muscle as mechanism for movement
Muscles connect to bones (via tendons) and contract to provide the force required to produce movement
The muscle connects a static bone (point of origin) to a moving bone (point of insertion)
Skeletal muscles exist in antagonistic pairs (when one contracts, the other relaxes) to enable opposing movements
Explain the role of antagonistic pair of muscles in insects
Many types of insects (including grasshoppers and praying mantises) have hind legs that are specialised for jumping
The jointed exoskeleton of the hind leg is divided into three parts: femur (upper leg), tibia (middle leg) and tarsus (lower leg)
The femur and tibia are connected by two antagonistic muscles: flexor tibiae muscle and extensor tibiae muscle
When the flexor muscle contracts, the extensor muscle relaxes and the tibia and femur are brought closer together
This retracts the hind quarters in preparation for pushing off the ground
When the extensor muscle contracts, the flexor muscle relaxes and the tibia is pushed away from the femur
This extends the hind quarters and causes the insect to jump
Outline the organisation of skeletal muscles
Skeletal muscles consist of tightly packaged muscular bundles (fascicles) surrounded by connective tissue (perimysium)
Each bundle contains multiple muscle fibres, which are formed when individual muscle cells fuse together
Muscle fibres contain tubular myofibrils that run the length of the fibre and are responsible for muscular contraction
The myofibrils can be divided into repeating sections called sarcomeres, each of which represent a single contractile unit
Outline the structure of myofibrils (5 points)
Each individual muscle fibre has the following specialised features designed to facilitate muscle contraction:
They are multinucleate (fibres form from the fusion of individual muscle cells and hence have many nuclei)
They have a large number of mitochondria (muscle contraction requires ATP hydrolysis)
They have a specialised endoplasmic reticulum (it is called the sarcoplasmic reticulum and stores calcium ions)
They contain tubular myofibrils made up of two different myofilaments – thin filament (actin) and thick filament (myosin)
The continuous membrane surrounding the muscle fibre is called the sarcolemma and contains invaginations called T tubules
Outline the components of myofibrils and their functioning
Myofibrils consist of repeating contractile units called sarcomeres, which are made of two protein myofilaments
The thick filament (myosin) contains small protruding heads which bind to regions of the thin filament (actin)
Movement of these two filaments relative to one another causes the lengthening and shortening of the sarcomere
Each individual sarcomere is flanked by dense protein discs called Z lines, which hold the myofilaments in place
The actin filaments radiate out from the Z discs and help to anchor the central myosin filaments in place
Explain what is the cause of a striated (striped) pattern along the length of the skeletal muscle fibres
The recurring sarcomeres produce a striated (striped) pattern along the length of the skeletal muscle fibres
The centre of the sarcomere appears darker due to the overlap of both actin and myosin filaments (A band)
The peripheries of the sarcomere appear lighter as only actin is present in this region (I band)
The dark A band may also contain a slightly lighter central region where only the myosin is present (H zone)
Explain the first step of muscle contraction
Depolarisation and Calcium Ion Release
An action potential from a motor neuron triggers the release of acetylcholine into the motor end plate
Acetylcholine initiates depolarisation within the sarcolemma, which is spread through the muscle fibre via T tubules
Depolarisation causes the sarcoplasmic reticulum to release stores of calcium ions (Ca2+)
Calcium ions play a pivotal role in initiating muscular contractions
Outline the second stage of muscle contraction
- Actin and Myosin Cross-Bridge Formation
On actin, the binding sites for the myosin heads are covered by a blocking complex (troponin and tropomyosin)
Calcium ions bind to troponin and reconfigure the complex, displacing tropomyosin along the myofilaments, exposing the binding sites for the myosin heads
The myosin heads then form a cross-bridge with the actin filaments
