PHYSIOLOGY Flashcards
what are the three types of muscle
skeletal
cardiac
smooth
what is the function of each type
skeletal-attached to the bone, supports and moves the skeleton
cardiac-muscle of the heart, propels blood through the circulatory system
smooth-surrounds hollow organs of the body, controls the movement of contents through the organ
breakdown of the muscle structure
muscle ( epimysium )
fascicle (perimysium)
muscle fibre (plasma membrane -sarcolemma )
myofibril (sacromere)
myofilament (actin and myosin )
what are the two types of fibres
long fibre- large movements, high velocity eg hamstrings
short fibre- short movement, high force eg quadriceps
what is a motor unit
a single motor neurone and the muscle fibre it innervates
which chemical is used in contraction
ATP
what are three systems of generating ATP
ATP phosphocreatine (PCr) oxidative system (aerobic) glycolytic system (anaerobic )
explain the need for ATP PCr system
ATP direct energy needs 2 seconds to exhaustion
PCr restores ATP level to 3-15 seconds to exhaustion ( as in it will be finished in about 15s)
explain the need for the glycolytic and oxidative system
they use aerobic and anaerobic methods to generate more ATP
what are the three types of muscle fibres
type I - slow twitch/oxidative
type IIa - fast twitch/oxidative
type IIb - fast twitch/glycolytic
are all muscle fibres of one motor unit the same type
yes
how to differentiate between the muscle fibre types
type I- dark
type IIa - lighter
type IIb - translucent
how to differentiate between muscle fibre types
type II stains metachromatic and type I stains dark blue
what is the function of a satellite cell
it is attached to the mature muscle fibre and it repairs it if its damaged
what are the functions of two regulatory proteins
tropomyosin-bocks myosin binding site
troponin-binds calcium
explain excitation contraction coupling
action potential in nerve-release of neurotransmitter at N/M junction-action potential in muscle-AP transferre to T tubule- SR releases calcium-muscle contracts
what holds the myosin and actin filaments together
titin filament
what is the function of nebulin
provides rigidity and ensures the actin filaments stay in place
what are the layers of cardiac muscle called
myocardium
what is the function of the sympatheitic system
releases noradrenaline
increases heart rate and force of contraction
what is the function of parasympathetic system
vagus nerve
releases acetylcholine
dominant effect at rest
depresses heart rate and force #
whats th structure of a cardiac muscle
- striated muscle
- uninucleate
- cells act as a syncytium - connected in series with intercalated discs, which are gap juctions and desosomes
how does excitation-contraction coupling work
initial depolarisation in sinoatrial node- action potentialin muscle-AP transmitted to T tubule-calcium influx from extracellular space-SR releases calcium CICR(calcium induced calcium release)- muscle contracts
how to ensure that the cardiac muscles relax
an extended refractory period by the calcium VGC slowly opening which keeps the membrane depolarised for longer
what is the structure of smooth muscle cells
long spindle shaped cells
uninucleate
no neuromuscular junctions-it has nerve branches with small swellings called varicositites
it has no sarcomere
what are the functions of myosin filaments
site of ATPase activity but very slow rate
low energy consumption so very fatigue resistant
allows muscle tone eg bladder
what are the functions of actin filaments
consists of actin molecules but longer
no troponin- function replaced by calmodulin in cytoplasm
what are the functions of calmodulin
involved in calcium binding
activates contraction
where does the actin bind insmooth muscle
to dense bodies
what is another word for transverse tubules in the smooth muscle
caveolae
what does smooth muscle respond to
neurotransmitters hormones local chemical changes eg pH stretch spontaneous electrical activity
what are the two types of smooth muscle
multiunit- discreet cells, richly innervated by nerves, contract indpendently of neighbour
single unit/visceral - cells linked by gap junctions, respond to a variety of signals, many cells respond as a single unit, spontaneously active
what is the excitation contraction coupling
stimulus-muscle membrane depolarises-calcium influx from extracellular space CICR-calcium binds to calmodulin- ATPase activated- muscle contracts
what are the different charcaterisitics of smooth muscle
very versatile very fatigue resistant low energy consumption allows muscle tone contract over much greater lengths
what are the main functions of the skeletal system
support-provides rigid structure protection of internal organs reservoir for calcium,, inorganic phosphate and other minerals storage of lipids (yellow marrow) blood cell production (red marrow)
what is the end of bone/growth plate called
epiphysis
what is the bone shaft called
diaphysis
what is the yellow marrow called
medullary (triglyceride store)
what is the red marrow called
spongy/cancellous bone (blood cell production)
what is the membrane with osteoblasts and osteoclasts on inner layer called
periosteum/ endosteum
what is the lamellae
rings of hard calcified bone matrix
what is lacunae
spaces which hold osteocytes
what is osteon
circular column of concentric lamellae
what is Haversian canal
central space containing blood vessels and nerves
what is canaliculi
small channel with osteocyte processes
what are osteoprogenitor cells
- mesenchymal bone stem cells
- produce osteoblasts
- proliferative, involved in growth and repair
what do osteoblasts do
secrete collagen to create a matrix (scaffold) which will become calcifies (osteogenesis )
-mature into osteocytes when surrounded by calcified matrix
what are osteocytes
- do not divide
- help maintain protein and mineral content of the matrix
- help repair damaged bone
what are osteoclasts
- giant multi nucleated cells
- secrete acids and proteases to dissolve bone (osteolysis)
- come from the same lineage as white blood cells
where are osteoclasts, osteoblasts and osteoprogenitor cells found
osteoblasts- lacunae
osteoclasts -line medullary cavity
osteoprogenitor-on the inside of the periosteum
what is bone composed of (organic matrix)
- collagen matrix(osteoid), gives elasticity and resistance-95%
- ground substance, extracellular fluid and proteoglycans chondroitin sulfate and hyaluronic acid
- mineral deposited on matrix (calcification), contributes strength and resistance
what is the formula for hydroxyapatite
calcium phosphate+calcium hydroxide
Ca3(PO4)2+Ca(OH)2 –>Ca10(PO4)6(OH)2
what stops the hydroxyapatite from forming
inhibitors such as pyrophosphate
what regulates pyrophosphateand how
alkaline phosphatase
- breaks down pyrophosphates
- collagen fibres then develop hydroxyapatite crystals for calcification
where does alkaline phosphatase come from
released by osteoblasts
what happens as a result o deficiency in alkaline phosphatase
soft bones
how does calcium level disruption lead neuromuscular excitability (twitching)
binding to plasma proteins acting as ion channels
low levels- hypocalcaemic tetany (muscle spasms)
high levels- hypercalcaemia and cardiac arrhythmia (rapid changes)
what is bone resorption
breakdown of bone which results in the release of calcium into the bloodstream
which hormones are responsible for increasing and inhibiting bone resorption
Parathyroid hormone (PTH) increases and Calcitonin inhibits controlled by negative feedback
where is parathyroid hormone released from
by parathyroid gland
where is calcitonin released from
by prarfollicular cells in the thyroid gland
give an example of the negative feedback cycle in calcium homeostasis
calcitonin released- osteoclast activity decreases- ca+ in the bone increases- plasma ca+ decreases- calcitonin release decreases-plasma ca+ increases
where is bone marrow found in infants and adults
infants-medullary cavity and all areas of spongy bone
adults-in the diploe of flat bones and the head of the femur and humerus
what happens to the amount of yellow marrow in the bone as we age
increases starting at the centre of the bone
function of red marrow
supplies nutrients to the osteocytes
forms red and white blood cells
function of yellow bone marrow
stores fat
may convert back to red marrow if there is severe bleeding
what is ossification/osteogenesis
process of bone formation
when do bones form
- during development
- during childhood growth
- to remodel bone e.g. response to stress
- repair
what does the bone replace
cartilage and chondrocytes deposition create a model which is replaced
what are dietary requirements for bone growth
- minerals such as calcium, phosphorus, magnesium, fluoride
- vitamins D(collagen), A(osteoblast activity and K
- protein
what factors affect growth
- sex-males taller than females
- sex hormones- end of puberty ceases growth
- stress- cortisol inhibits growth and increases breakdown
- nutrition
how does structure of the bone change as we age
deposition of bone by osteoblasts from the outside ( periosteal layer)
resorption of bone by osteoclasts on the inside ( endosteal layer)
what does physical stress and illness do to bone structure
physical stress increases deposition and illness decreases deposition
how do osteocytes regulate bone remodeling and repair
- support osteoclastogenesis
- secrete growth factors to support bone formation
- secrete sclerostin to inhibit bone formation
what happen during the breakdown of bone
osteoclasts form grooves called resorption bays as they break down bone matrix
hydrogen ions and hydrolytic enzymes are released to dissolve the bone ( osteolysis)
the products of bone breakdown end up in the blood plasma thus increasing plasma calcium levels
what affects bone density
exercise can increase bone density
what are the different types of fractures
open-skin is broken
greenstick-more common in children
comminuted-fracture splintering/ crushing
impacted-fracture pushes bone into interior
what are the phases of bone healing
reactive, reparative, callus formation, bone remodeling
what happens in the reactive phase of bone healing
- blood vessels crossing the line of the fracture are broken
- a blood clot (fracture hematoma) rapidly forms around the fracture site
- surrounding bone cells die due o lack of vascularisation
- cell death and inflammation
- clean up operation-immune system
what happens in the reparative phase of bone healing
- vasculogenesis of the hematoma-removal of dead cells by phagocytes
- fibroblasts move into the fracture site and start to build new collagen fibre
- cells from the periosteum develop into chondroblasts and produce fibrocatilaginous callus
- the ends of the bone are being to stabilize usually takes 3 weeks
what happens during callus formation
- osteoprogenitor cells from the periosteum develop into osteoblasts and produce spongy bone trabeculae
- trabaculae join up living and dead bone fragments
- fibrocartilage is converted to spongy bone, the callus is now a bony callus
- the bony callus lasts 3-4 months
what happens during bone remodeling
- osteoclasts resorb dead bone
- spongy bone is replaced by compact bone
- a thickened area may remain on the surface of the bone
what is the approximate blood pressure in the pulmonary circuit
28/8 mmHg
what is the approximate blood pressure in the systemic circuit
120/80 mmHg
what is heart failure
the pathological state in which the heart is unable to pump blood at a rate required by metabolizing tissues or can do so only with an elevated filling pressure
what is the relaxation of the atria and ventricles called
diastole
what is the contraction of the atria and ventricles called
systole
which node initiates the electrical signal
the SA node ( sinoatrial)
what is atriole systole and what wave is it
when the atria contract and blood fills the ventricles and this is the P wave
what is the first part ventricular systole and what part of the wave is it
when the ventricles contract and the AV valves close called the QRS complex
what is the second part of systole and what part of the wave is it
semilunar valves open and blood is ejected this is the T wave
what is the first part of ventricular diastole
the semilunar valves close and blood flows into the atria
what is the second part of ventricular diastole
chambers relax and the blood refills the ventricles passively
what is the function of desmosomes
hold the muscle cells together tightly
what is the function of the intercalated disks
link muscle cells together and contain the desmosomes and gap junctions
what is the function of gap junctions
allow passage of action potentials from one cell to the next very quickly
what is a feature of myocardial cells
can simultaneously depolarize and this means an electric current can be automatically produced so the SAN cells dont need neighbor cells to depolarize first
what is the importance of fibrous tissue between the atria and ventricles
it lacks gap junctions and electrically isolates atria from ventricles and so provides a border
what is the transmembrane potential, TMP
the electrical potential difference between the inside and outside of a cell
what is the difference between chemical and electrical potential
chemical is ions moving down its concentration gradient and electrical is ions moving away from ions/molecules of like charge
what are cardiomyoctes
the cells responsible for generating contractile force in the intact heart.
what are the properties of cardiac ion channels
selectivity- only permeable to a single type of ion based on their physical configuration
voltage-sensitive gating- dependent on a specific TMP range
time dependance- some are configured to close either slower or faster than others
what is the pacemaker potential
when the cells of the SAN depolarize over time with the movement of ions causing the resting membrane potential to decrease
what happens once the membrane potential exceeds the threshold and after how many seconds does this happen appproximately
an action potential is generated and this happens automatically every 0.8s
why does AVN depolarize more slowly than the SAN and how slowly approximately
because this allows for a very short delay so that the blood can fill the ventricles before they contract usually about 0.09s
what is excitation contraction coupling
the process by which an electrical action potential leads to contraction of cardiac muscle cells.
how is excitation contraction coupling achieved
converting a chemical signal into mechanical energy via contractile proteins
what mediator is important in convert the electrical excitation into physical contraction
calcium by cycling in and out of the monocytes cystol during an action potential
what causes the pacemaker potential/ plateu in cardiac potential
funny channels in the SAN open and sodium ions enters which causes depolarization which opens gated calcium channels and they enter the membrane slowly and so it gradually depolarizes another type of voltage gated channel opens and calcium enters the cell rapidly and this leads to rapid depolarization which is the cardiac action potential
what is an example of transient channel and at what potential does it open
T type Ca++ open briefly at -50mV
what is an example of a long lasting channel and at what potential does it open
ca++ open at -40mv full depolarization
