Bone & Biomechanics 4 Flashcards
What do soft cells need to do?
Maintain their shape as it is needed for their function
How do soft cells maintain their shape?
Water moves into cells by osmosis and osmotic pressure gives soft tissue cells their shape
What is the Intercellular fluid?
Cytoplasm or cytosol
What must be balanced between the ICF and ECF?
Water
How is water lost?
By water vapour at the skin and lungs, faeces, sweat glands and urine
How much water is lost by water vapour at the skin and lungs based on an intake of 2200mL?
1150mL
How much water is lost in faeces based on an intake of 2200mL?
150mL
How much water is lost at sweat glands based on an intake of 2200mL?
variable
How much water is lost through urine based on an intake of 2200mL?
1200mL
What is also found alongside water in the ICF and ECF?
Solutes and ions
What is isotonic?
Occurs when the ICF and ECF solutions are balanced
What is the benefit of the ICF having a larger volume and water content?
If damage occurs to the ECF then it can be fixed by the extra ICF which is present
Which fluid has the larger volume and water content?
Intracellular Fluid
What is hypertonic?
Occurs when water is lost from the ECF and volume is decreased therefore making the solute concentration higher.
What happens when the ECF becomes hypertonic?
An osmotic water shift from the ICF to the ECF restores osmotic equilibrium but decreases the volume of the ICF.
How can dehydration occur?
If continual loss of water from the ECF occurs
What is hypotonic?
When there is too much water in the ECF
What happens when the ECF becomes hypotonic?
Water moves from a low concentration of solutes into the ICF to restore the osmotic equilibrium. This makes the intracellular environment bigger and the cell swells.
Where are ions and electrolytes absorbed?
Across the epithelial lining of the small intestine and colon
Where are reserves of ions found?
Primarily in the skeleton but also in the ICF and ECF
Where does excretion of ions occur?
At the kidneys(primary site) and the sweat glands (secondary site)
What are the main ions needed in the body?
Potassium, Sodium and Calcium
What are examples of excitable cells?
Neurons and muscles
What do excitable cells have?
A membrane potential
What cells also have membrane potential?
Epithelial cells
What does membrane potential rely on?
The distribution of sodium and potassium ions which are obtained from the diet
Where are cations and anions present?
Inside and outside all cells
What is the function of the lipid bilayer with regard to ions?
It is an insulator to prevent the free flow of cations and anions
What does the distribution of ions create and why?
Membrane potential because they are charged
What is the concentration of sodium ions in the ECF?
High
What is the concentration of potassium ions in the ECF?
Low
What is the concentration of sodium ions in the ICF?
Low
What is the concentration of potassium ions in the ICF?
High
What is the average resting membrane potential and what does it mean?
-70mV which means there is a slight negative change inside the cell
Want is the function of the sodium-potassium exchange pump?
It moves and exchanges sodium and potassium against their concentration gradient and therefore uses energy
What is the chemical gradient?
The concentration gradient
What is the electrical gradient?
Gradient formed by distribution of the charge
What is the electrochemical gradient?
The combination of the electrical and chemical gradients
Where does the sodium chemical gradient point?
Into the cell
Where does the sodium electrical gradient point?
Into the cell
Where does the sodium electrochemical gradient point?
Largely into the cell
Where does the potassium chemical gradient point?
Out of the cell
Where does the potassium electrical gradient point?
Into the cell
Where does the potassium electrochemical gradient point?
Out of the cell slightly
Why does the membrane potential change sometimes?
Because of chemical stimuli initiating changes
What happens when the membrane potential changes?
Depolarisation or Hyperpolarisation
What happens during depolarisation?
The stimulus opens the sodium channel causing it to move into the cell and therefor the membrane potential becomes less negative
What happens during hyperpolarisation?
The stimulus opens the potassium channel causing it to move out of the cell and therefore the membrane potential becomes more negative
How many muscles are in the body?
Around 600
How many different types of muscles are there?
3
What are the 3 types of muscles?
Smooth, cardiac and skeletal
Where is smooth muscle found?
Lining hollow organs such as the gut and blood vessels
Where is cardiac muscle found and what is its function?
In the heart only and it generates force to pump blood around the body
What is the function of skeletal muscle?
To apply force to the bones to control posture and movement
What muscles are voluntary?
Skeletal muscles
Which muscles aren’t voluntary?
Smooth muscle and cardiac muscle
What does voluntary control mean?
We can choose when to activate them
What is the primary job of skeletal muscles?
To develop tension and force for contraction and movement
Describe the force in muscles
It is generated in one direction only and developed by shortening
What is the secondary jobs of skeletal muscle?
Providing support and protection for soft internal organs, converting energy to heat so that core temperature can be maintained and providing major storage for energy and protein
What does skeletal muscle provide voluntary control for?
Major openings such as the mouth to allow the passage of substances into and out of the body
What is the shape of skeletal muscle cells?
Long and thin
What do skeletal muscles contain large amounts of?
Protein and nuclei
What ensheaths muscle fibres and what is its function
Connective tissue which connects the muscle fibres to the bone
What is skeletal muscle richly supplied with?
Blood vessels which are needed to bring glucose and oxygen when exercising. Also nerve endings
What are fascicles?
Muscle fibres gathered into bundles
What forms muscles?
Bundles of fascicles
What does connective tissue ensheath?
Muscle fibres, fascicles and whole muscles
What does the epimysium ensheath?
The whole muscle
What does the perimysium ensheath?
The fascicles
How are tendons formed?
By the gathering of connective tissue which then connects the muscle to bone
What is the typical width of muscle fibres?
20-40 micrometres
What is the range in length of muscle fibres?
Up to 36cm long
What is a muscle fibre comprised of?
Bundles of myofibrils
What are myofibrils made of?
Repeating units called sarcomeres
What is the sarcomere contained between?
Z lines
What indicates the middle of a sarcomere?
The m line
What are sarcomeres made of?
Contractile proteins called myofilaments
What are the two myofilaments in sarcomeres?
Actin and myosin
What is the thin myofilament?
Actin
What is the thick myofilament?
Myosin
What gives muscle its striped(striated) appearance?
The interlacing of actin and myosin
What is the sarcolemma?
The plasma membrane of muscle
What are transverse tubules?
Tubular extensions of the surface membrane which penetrate down into muscles
What is the functions of t-tubules?
To conduct electrical signals (action potentials) deep into the core of the fibre
What is the sarcoplasmic reticulum?
an extensive membranous tubular network which wraps around all of the myofibrils and is associated with the t-tubules at regular intervals
what is the terminal cisternae?
The bulgy part of the sarcoplasmic reticulum which holds calcium
What is a triad?
Includes the terminal cistern, the t-tubule and another terminal cisternae
What is the role of the sarcoplasmic reticulum?
To take up and store calcium, then to release calcium ions into the cytoplasm upon receiving an action potential conducted along the t-tubules
What is also found in muscle fibres?
Large mitochondria because muscles need lots of energy
What is actin?
A globular protein (g-actin) and the globules assemble to form filamentous protein structures (f-actin)
What is the structure of f-actin?
Each filament is a twisted strand of 2 rows of f-actin terminating at one end of the z line
What is myosin molecules structure?
Myosin molecules have a long thin tail and a globular head which can move
What is the structure of a myosin filament?
The thick filament is formed from pairs of myosin molecules arranged with the tails pointing towards the m line and forming a complex double headed structure
How do contractile proteins develop force?
by triggered molecular interaction that allows association of the myosin head with the nearby thin actin filament followed by the flexing of the myosin head to allow it to walk along the thin filament. This causes thick and thin filaments to slide past each other
What does the arrangement of myosin heads in a sarcomere mean?
The ends of the sarcomere are drawn closer together when flexing of the myosin heads occurs so that the x lines are now closer to the m line
What is the process of muscle shortening?
Sarcomeric shortening, myofibril shortens, muscle fibre shortens, whole muscle shortens to produce force and tension
What are muscle contractions triggered by?
Electrical events called action potentials
What is the path of action potentials?
They arise in the brain and are conducted down the spinal cord to motor neurons in the spinal cord and then conducted out of the CNS along motor axons to muscle fibres
What is a neuromuscular junction?
Where the electrical impulse from the brain meets the muscle- the axon of a motor neurone terminates at a single point on the muscle fibre
What is a motor unit?
A motor neuron and the muscles it controls
What does action potential do?
Cause change in the membrane potential of muscle fibre and these events cause contraction
What does each muscle fibre receive?
Contact from one motor neurone at one site
