Anatomy + Physiology 2 Flashcards
Universal characteristics of Muscles
- Excitablity / responsiveness (chemical signals, stretch, electrical changes)
- Conductivity )Electrical excitation initiate waves of excitations
- Contractility (Shortens when stimulated)
- Extensibility (Stretched between contractions)
- Elasticity ( Returns to original rest lengths)
Skeletal muscle
Attached to bone via tendons. Contraction brings movement across Joints
Voluntary striated muscles
Voluntary - usually subjected to conscious control
Striated - alternating light and dark bands due to internal contractile protiens
Structural hierachy of skeletal muscle w/ definitions
- Muscle↔Contractile organ - attached to bones with tendons. Separated from other muscles with fibrous epimysium
- Fasicle↔bundle of muscle fibres within a muscle. supplied by nerves and blood vessles and enclosed in bibrous perimysium that separates it from neighbouring fascicles
- Muscle fibre↔single muscle cell - slender, elongated enclosed in specialized plasma membrane (sarcolemma) . Contains densely packed bundles - myofibrils - of contractile protien filaments, multiple nuclei immediately beneath the sarcolemma and extensive network of specalized smooth endoplasmic reticulum.
- Myofibril↔Bundle of protien myofilaments within muscle fibre. Conenctively fill most of cytoplasm. Surrounde by sarcoplasmic reticulum and mitochondria. Banded (striated) appearance due to overlap of protien myofilaments
- Sarcomere↔Segment of myofibril from one Z disk to the next in striation pattern. Hundreds end to end to compose a myofibril. Functional, contractile unit of muscle fibre
- Myofilaments↔fibrous protien strands that carry out contraction process - thick filaments (Myosin) and thin filaments (Actin). Thick and thin side over one another to shorten each sacromere - shortening end to end shortens entire muscle
Skeletal muscle cells (fibre)
Multiple Peripheral Nuclei
Mitochondria between myofibrils
SKeletal muscle Glycogen
Carbohydrate stored to provide energy for excerise
Skeletal Muscle Myoglobin
Red pigment - provides O2 needed for muscle activity
Skeletal muscle Myoblasts
Stem cells fuse and form muscles fibres early in development
Skeletal muscle Saatellite cells
unspecialized myoblasts between muscle fibre and endomysium. Play a role in regeneration of damaged skeletal muscle tissue
Muscle Fibre - Myofibrils
Attached to inner surface of sarcolemma. Comprised of bundles of protien fillaments
Thin - Actin
THick - myosin
Sarcoplasmic Reticulum - SR
Smooth ER network around myofibril
Terminal Ciserns
Dilated end sacks of SR that cross muscles fibre from one side to the other - Ca+ reservoir
T tubules
Tubular infoldings of sarcolemma which penetrate through cell and emerge on other side
Triad
T Tubule and two terminal cisterns associated with it
Muscle fibre - Sarcomeres
Myofilaments organized into repeating functional unis.
A bands - Dark
I bands - Light
Sacromere
Segment from Z disk to Z disk.
H Band - contains thick filaments
I band - contains thin filaments
Subdivisions::
M line- Protiens that connect neighbouring thick filaments
H Band - Region either side of M line (THICK FILAMENTS ONLY)
A band - zone of overlap
Actin
Thin filaments
Fibrous acitn - two intertwined strands
Glubular - single string w/ active site that binds to had of myosin molecule.
Tropomyosin
Actin binding protien. Molecules that block acive sites on G actin subinits
Troponin - small calcium binding protien on each Tropomyosin
Myosin
Comprise of thick filaments.
Molecules shaped like double headed golf club - 2 chains.
Heads directed outwards
Heads on 1/2 filament angle to left, other 1/2 to right
Bar zone = no heads
Dystrophin
Linked actin to outermost myofilaments to membrane protiens that link to endomysium.
Transfers forces of muscle contraction to connetie tissue leading to tendon.
Genetic defect = myscular dystrophy
Titin (hehe titty)
Elastic filaments
Runs through core of thin filament and anchors it to Z disk and M line
- stabalize and position thick filament
Skeleal muscle contraction in order
- Sarcomere shorten
- H bands and I bands get smaller
- Zones of overlap get larger
- Z lines move closer together as thick and thin filaments slide past eachother
- Width of A band remains constant
- During shortening↔Dystrophin and linking protiens pull on extracellular protiens
- Transfers pull to extracellular tissue
- Sliding in all sarcomeres in Myofibril
- Myofibril gets shorter
- muscle fibre gets shorter
- muscle gets shorter
- produces tension
- ONLY CONTRACT WHEN STIMULATED BY A NERVE
Motor neurons and motor units
Somatic motor neurons - nerve cells who bodies lie in brainstem and spinal cord
Somatic motor fibres - axons that lead to skeletal msucle
Motor Unity - one nerve fibre and all muscle fibres innovated by it.
Muscles fibres in one motor unit
- dispersed throughout muscle
- Contract in unison
- produce weak contraction over wide area
- Able to sustain long term contraction as motor units take turn contracting
- Contraction usually requires contraction of several motor units at once .
Small motor unit
- Fine degree of control
- 3-6 muscles per neuron
- eye and hand muscles
Large motor units
- More strength than control
- Powerful contractions supplied by alrge motor units with hudreds of fibres
- Gastrocnemius has +- 1000 muscle fibres per neuron
Neuromuscular Junction
nerve fibre meets target cell - target cell is muscle cell
- Terminal branches of nerve fibres within NMJ forms synapses with muscle fibres
- one nerve fibre stimulates the muscle fibre at several points within MNJ
Nerve parts
Axon terminal - swolen end of nerve fibre
Synaptic cleft - gap beween axon terminal and sarcolemma
Electrivally excitable cells
- Muscle fibers and neurons are electrically excitable
- Cell membranes exhibit voltage changes in responce to stimulation
- Voltage - difference in eectrical charge from one point to another
- resting membrane potential +- 90mV in skeletal muscle cells
- Maintained by sodium/potassiun point
Unstimulated resting cell
- More anions (-ve) on inside of cell membrane than outside
- anions make inside of pl asma membrane negatively cahrged by comparison to outer surface
- plasma membrane is electrcially polarized with negative resting membrane potential
- there are excess Na+ In extracellular fluid (ECF)
- Excess potassium Ions (K+) in intracellular fluid.
Stimulated
- Na+ Ion gates open in the plasma memrbrane
- Na+ flows into cell down its electrochemical gradient
- these cations overide the negative charges in ICF
- depolarization↔inside of plasma membrane becomes positive
- Na+ gates close and K+ gates open
- K moves otu of cell partly repelled by na+ cahrge and aprtly because of concentration gradient
- Loss of positive K+ ions turns membrane negative again - repolarization
- this voltage shift - depolarization and repolarization - is an action potential
Resting membrane potential - cell not stimulated
- Action potential is quick event in stimulated excitable cell
- perpetuates itself down length of cell membrane
- AP causes another ot happen immediatly infront of it
- triggers another
- wave of excitation is called a impulse
Neruomuscular toxins and paralysis
- toxins can interfere with synaptic function - paralyzem uscles
- some pesticisdes contain cholisterase inhibitors
- bind to acetylcholinestrae and prevent it from degrading ACh
- Spastic paralysis - state of continual contraction of muscles - suffocation
Teatnus / lockjaw
Form of spastic paralysis cauased by toxin Clostridium Tetani
Flaccid paralysis
Muscles are limp and cannot contract
Butolism
Food poisoning caused by neruomsuclar toxin secreted by the bacterium colstridum botulinum
Exccitation
- Excitation↔process in which nerve action potential lead to muscle action porentials
- Action potential arrives at synaptic terminal
- scetylcholine is relaseased
- permeability of membrane changes and triggers ACh
- ACh molecules cross synaptic cleft and bind to ACh receptors on Sarcolemma
- Na+ ions rush into sarcolemma generate action potential
- K+ moves out of cell - concentration gradient
Excitation - contracting coupling
events that link action potentials on sarcolemma to activation of myofilaments - preparing them to contract
- Action potential spreads along each T tubule (lie between two ends of sarcoplasmic reticulum
- In resting state tropmyosin srands cover active sites on thin filaments
- Prevents cross-bridge formation
- Ca+ binds to and cahnges shape of troponin molecule
- Troponin molecule roles tropomyosin from active sites
Contraction
- Contraction↔muscle fibre develops tension and may shorten
- Energised (ADP) myosin heads bind to active sites of F actin
- Formation of cross bridges
- contraction cycle begins
- Myosin head pivots towards M line - requires energy. REFERED AS A POWER STROKE
- Breaking of new ATP - breaking of cross bridge.
Relaxation
stimulation ends - muscle fibres relaxes and returns to resting length
- Cessation of nervous stimulation and ACh release.
- ACh breakdown by Acetylcholinesterase (AChE)
- Reabsorption of Ca ions by sarcoplasmic reticulum
- Free myosin head splits ATP int ADP and phosphate group
- Energy released cocks Myosin head
- cycle can now be repeated
- ATP binds to myosin head and breaks link to action
- Active site now free.
Length tension relationship
amount of tension generateed by a muscle depending on how stretched or shortened it was before it was stimulated
- If overally shortened before stimulation - weak contraction results as thick filaments approached Z discks
- if to stretched before stimulated - weak contraction results as minimal overlap between thich and thin filaments in minimal corss bridge formation
- Optimum resting length produces greatest force of muscle contracts↔Nervous system maintains muscle tone (partial contraction) to ensure that resting muscles are near this length
Rigor Mortis
- Hardening of muscles and stiffening of body
- Starts 3-4 hours after death
- teriorating sarcoplasmic reticulum releases Ca+2
- Allows Ca+2 to enter cytosol
- Ca+2 activates Myosin actin cross bridging
- muscle contracts, but cannot relax
- Muscle relaxation requires ATOP - No longer produced after death
- Fibres remain contracted until Myofilaments begin to decay
- Rigor mortis peaks +- 12 hours after death
- Diminishes over next 8-60 hours.
Threshold
Minimul voltage neccessary to generate an action potential in muscle fibre and produce contraction
Twitch
cycle of contraction and relaxation when stimulus is at threshold or higher
Latent Period
very bried delay betweein stimulus and contraction
- Time required for excitation, excited Contraction coupling, and tensing of elastic Components of muscle
Contraction phase
time when muscle generates external tension
- Force generated can overcome load and cause movement
- Relaxation phase↔time when tension declines to baseline
- SR reabosrbs Ca+2 myosin released actin adn tension decreases
- Takes Longer than contraction.
Integumentary system
Skin and accessory organs (hair nails + glands).
Largest and heaviest organ - thick and thin
Thick skin (location, accessories and epidermis thickness)
Plams of hands/soles of feet
sweat glands
Sweat glands, NO hair follicles or Sebacenous glands
Epidermis - 0.5mm thick
Thin skin (location, accessories and epidermis thickness)
Rest of body (Not soles/palms)
Hair follicles, sebaceous glands and sweat glands
Epidermis +/- 0.1mm thick
Functions of the skin
Resistance to trauma/infection
H2 barrier (prevents h2 getting in) - tight junctions between cells (prevents dehydration)
Uv radiation + harmful chemicals
Vitamin D synthesis (First step - liver and kidneys complete)
Epidermis - outer stratified squamous epithelium
Keritinized (tough protein)
layered + flat cells.
MAIN CELL = Keratinocytes
No blood vessels - nutrients fro diffusion from underlying connective tissue.
Nerve endings and receptors for touch/pain
Layers of epidermis (Deepest to top)
- Stratum basale - single layer stem cells + keratinocytes. Migrate to surface to replace lost cells - also contains melanocytes nad tactile cells
- Stratum spinosum - several layers of keratinocytes + desmosmes and tight junctions
- Stratum granulosum - 3-5 layers of flat keratinocytes (dark staining keratohyalin granules)
- Stratum lucidum - thin + pale layer only in thick skin - keratinocytes packed with clear protein eleidin.
- Stratum corneum - surface layer - several layers (up to 30) of dead scaly keratinized cells.
Keratinocytes
synthesis keratin - produced by mitosis of stem cells. needs abundant Oxygen and nutrients - once away from Blood vessels, itosis cannot occur
Melanocytes
Synthesise pigment melanin - sheilds DNA from UV radiation (only in stratum basale)
Dendric cells
Macrophages, originate in bone marrow - guard against pathogens (Stratum spinosum + stratum granulosum)
Tactile cells
Touch receptor cells associated w/ dermal nerve fibres - base layer of epidermis
Dermis
Connective tissue layer under epidermis - 0.2mm to 4mm.
Mainly collagen + blood vessels, sweat glands, sebaceous glands and nerve endings
Hair follicles + nail roots.
FOrms wavy boundary with epidermis
DERMAL PAPILLAE - Upward finger like extension of dermis.
- Prominant wave on fingers - finger prints
Dermis layers
Papillary layer - superficial zone - thin areolar tissue in and near dermal papilla (allows mobility of leukocytes and other defence cells)
Reticular layer - deeper, thicker layer. Dense irregular connective tissue. (stretch marks - tears in collagen fibres)
Hypodermis
Deep connective tissue layer below dermis - not considered apart of the skin, but associated with it)
Subcutaneous tissue - more areolar and adipose tissue than in dermis. Pads the body and binds skin to underlying tissues
Abundant blood vessels - common injection sites
Skin disorders
Ichthyosis - inherited, shedding process inhibited (can result in overheating)
Eczema - chronic inherited inflammatory skin condition w/ dry itchy and reddening of skin
Exfoliative dermatitis - excessive shedding of skin
Skin colour
Melanin produced by melanocytes - accumulates in keratinocytes
Eumelanin - brownish black
Pheomelanin - reddish yellow
Haemoglobin - pink/red hue to skin
Carotene - yellow pigment aquired from egg yolks / orange/ yellow vegetables
Hair
Slender filament of keratinized cells gorwing from follicle in skin
- not on palms/ soles.
Structure of Hair
Bulb↔A swelling at the base of a hair follicle where hair originates in Dermis - only living hair cells are in or near bulb
Root↔the remainder of the hair in the follicle
Shaft↔the portion above the skin surface
Hair matrix↔region of mitotically active cells immediately above papilla - hair growths centre
Dermal papilla↔Bud of vascular connective tissue encase by bulb - only source of nutrition for hair
Hair receptors↔Sensory nerve fibres entwining follicles
Piloerector muscle (arrector pili)↔smoothe muscle attaching follicle to the dermis - contracts to make hair stand on end - goosebumps
Skin apendages - Nails
Clear derivates of stratum corneum - thin dead cells packed with hard keratin
Nail plate - hardp art of the nail, free bit hangs over fingertip (nail body attached to finger, nail root, under skin)
Nail fold surrounding rising skin around nail
Nail groove - separates nail fold from nail plate
Nail bed - skin under naiN
Sweat glands
Apocrine sweat glands - groin/anal region, areola, beard area in men - near hair follicles. milky sweat + pheromones.
Merocrine sweat glands- most numerous, dese on palms, soles + forehead. Simple tubular glands + watery perspiration
Sweat
Protein free filtrate of blood plasma - 99% water with a ph of 4-6
500ml/day
Mammary glands
Produce milk - develop during pregnancy and lactation
MODIFIED APOCRINE SWEAT GLANSD - Rich secretion
Skin cancer
§ Basal cell carcinoma
□ Most common type and least dangerous - seldom metatasizes
□ Forms from cells in stratum basale
□ lesion is small shiny bump with central depression and beaded edges
§ squamous cell carcinoma
□ Arises from keratinocytes of stratum spinosum. Lesions usally on scalp, ears, lower lip or back of hand.
□ raised reddened scaly appearance later formed a concave ulcer
□ cahnce of recovery good with early detection and surgical removal
□ tends to metastasize to lymph nodes - may become lethal
§ malignant melanoma
□ Cancer arises from melanocytes <5% of skin cancers - most deadly form.
□ Can be successfully removed if caught early, but if metastasizes it is usually fatal
□ Greatest risk factor - familial history
Highest incidence in men, redheads and people who had severe sunburn as a child
Burns
Leading cause of accidental death
First degree burns
□ Only involve epidermis
□ Redness, slight edema and pain
□ heal in days
Second degree burns
□ Partial thickness burn - involves part of dermis
□ May appear red, tan or white - blistered and painful
□ two weeks to several months to heal and may leave scars
Third degree burn
□ Full thickness burn - involves epidermis, all of dermis and often some deeper tissue.
□ Often requires skin grafts
needs fluid replacement, infection control, supplemental nutrition
stages of healign a skin wound
§ Several vessels bleed into cut
§ mast cells and damaged cells release histamine
§ histamine dialates blood vessels and makes capillaries more permeable
§ blood plasma seeps into wound carrying antibodies and clotting proteins
§ Blood clot forms↔Knits edges of cut together. Inhibits spread of pathogens
§ Forms scab that temporarily seals wound and blocks infection
§ Macrophages phagocytise and digest tissue debris
§ New capillaries sprout from nearby vessels.
§ Deeper portion of cloinfiltrated by capilaries and friblasts
§ Transforms into soft mass called granulation tissue
§ macrophages remove blood cot
§ fibroblasts deposit new collagen
§ begins 3-4 days after injury and lasts up to two weeks
§ Epithelial cells multiply and migrate beneath scab - tissue regenerates
§ underlying connective tissue undergoes fibrosis
§ Scar tissue may or may not show through epithelium
Remodeling phase begins several weeks after injury and may last up to 2 years
Blood
Connective tissue.
Plasma - liquid in blood
cells - forms elements of the blood
Function of the blood.
§ Transportation↔Dissolved gases, nutrients, hormones and metabolic wastes
§ Regulation of pH and ion composition of interstial fluids
§ Restriction of fluid loss at injury sites - clotting
§ defence against toxins and pathogens
stabilisation of body temperature
Haeme - recycling of red blood cells
○ Macrophages of liver, spleen and bone marrow monitor quality and engulf old RBC’s
○ Each component of haemoglobin molecule is recycled
○ Globular proteins dissembled into amino acids and released for other cells to use
○ Heme units are stripped of ion and turned into biliverdin (green in bruises)
○ Biliverdin is turned into bilirubin (orange/yellow in jaundice) and transported to liver- excreted as bile
blood antigens
○ Type A↔Surface antigen A only
○ Type B↔Surface antigen B only
○ Typpe AB↔Surface antigen A and B
Type O↔Neither surface antigen or AB
Blood antibodies
○ Type A↔Anti-B antibodies in plasma
○ Type B↔Anti-A antibodies in plasma
○ Type AB↔Neither Anti-A/B antibodies in plasma
Type O↔Both Anti-A/B antibodies in plasma
Haemolytic disease of the newborn
arise when Rh-neg. woman is carrying Rh-pos. fetus. When fetal and maternal blood mix at delivery - antepartum haemorrhage, amniocentesis - the mother recognises fetus Rh antigens as being foreign
○ Mixing of blood can stimulate mothers immune system to produce anti Rh antibodies - sensitisation
○ if mother has another rh pos. fetus her anti Rh antibodies cross placenta and attack fetus RBCS
The THorax
○ RIB CAGE
○ Wall comprises↔12 Thoracic vertebrae (posteriorly), sternum (anteriorly) and rubs (Anterolaterally)
○ Inlet - root of neck‒ and outlet - diaphram.
○ Encloses heart and lungs - some protection for spleen , liver and kidney.
Provides atachement for pectoral girdle and upper limbs. Able to contract and expand during respiration
Sternum
○ Bony plate anteriro to the heart - palpable (subcutaneous) in parts.
○ Three parts
§ manubrim
§ body - gladiolus
§ xiphoid process
Other features↔jugular notch and manubriosternal junction/joint - sternal angle
The Ribs
○ 12 pairs
○ articulate posteriorly with bodies and transverse processes of vertebrae
○ articulate anteriorly with their costal cartilages
○ costal cartialges - hyaline cartilage - to attach rib to sternum.
○ Costochondral joints classified as priamry cartilaginous joints
Ribs anatomy
○ Head↔portion of rib that articulates w/ bodies of thoracic vertebrae. - superior and inferior articular facets
○ Neck↔narrow portion distal to the head
○ tubercle↔wider, rough area distal to the neck. - articulates with transverse costal facet of vertebra
○ Angle↔lateral curve of rib
○ Shaft↔long sloping blade like portion of rib. - costal groove on inferior margin of shaft
True ribs↔Ribs 1-7. Each articulate with sternum via costal cartilage
False ribs↔ribs 8-12. Connects to costal cartilage of above ribs. forms costal margin.
Floating ribs↔ribs 11-12. No cartilaginous connection to sternum. No connections to costal cartilages above. No tubercles. No attachments to transverse processes of vertebra
Chest cavity + contents
○ Contains
§ Right and left lungs and pleural cavities
§ heart and great vessels - centrally, in mediastinum
§ trachea, oesophagus, nerves
Mediastinal boundaries
○ Anteriorly↔sternum
○ posteriorly↔vertebral column
○ inferiorly↔diaphragm
superiorly↔thoracic inlet
Mediastinal subdivisions
○ T4 plane
§ Arching aorta
§ tracheal bifurcation
§ azygos vein enters SVC
§ thoracic duct crosses vertebral column
○ Inferior mediastinum
§ Further subdivided by fibrous pericardium into
□ Anterior mediastinum
□ Middle mediastinum
□ Posterior mediastinum
□ Pericardium
□ heart
roots of great vessels
Pulmonary circuits
○ Major divisions of circulatory system
○ Pulmonary circuit↔right side of heart - carries blood to lungs for gas exchange and back to heart
§ Oxygen poor blood arrives at inferior and superior venae cavae
§ Blood sent to longs via pulmonary trunk
○ Systemic circuit↔Left side of heart - supplies oxygenated blood to all tissues of body and returns it to heart
§ Fully oxygenated blood arrives from lungs via pulmonary veins
§ Blood sent to all organs of the body via aorta
Histology (anatomy) of blood vessles
§ Tunica intima - innermost
§ tunica media - middle
tunica adventitia - outer
Anatomy of the heart
○ Hollow four chambered fibromuscular pump
○ Right and left atria and right and left ventricles
Base, apex, surfaces and borders
□ Outer fibrous pericardium↔Outer collagenous, inelastic sac. Fused to central tendon of diaphragm and adventitia of great vessels. Attached by ‘ligaments’ to sternum - variable. Securely anchored heart within thorax
□ Parietal serous Pericardium↔Lines the fibrous pericardium and reflects on to surface of the heart
□ Visceral serous pericardium
Chambers of the heart
○ Right and left atria↔superior in position. receive blood returning to heart. Auricles (seen on surface) - extensions of chamber
Right and left ventricles↔inferior in position. Pump blood into aorta and pulmonary trunk
Atriums
○ Openings for veins - venae cavae, pulmonary veins
○ Reveive venous blood from systemic and pulmonary circulations
○ Blood reservoir - weak pump
Right atrium
§ Musculi pectinati.
§ Crista terminalis - suculus terminalis
§ Limbus fossa ovalis + Fossa ovalis
§ cusps of tricuspid valve
§ Openings for↔Superior/inferior vena cavae and Coronary sinus
○ Left atrium
§ Openins of 4 pulmonary veins.
§ Cusps of bicuspid valve.
Roughened auricle
Ventricles
○ Thick muscular chambers - cardiac muscle
○ receive blodo from atria via AV openings.
○ Pump blood into systemic and pulmonary circulation
○ Features
§ Trabeculae carneae
§ valve cusps
§ chordae tendinae
§ papillary muscles
aortic/pulmonary opening
Atrioventricular valves
○ Collagenous tissue lined with endothelium. Control blood flow from atria to ventricles
○ Right AV has three cusps - tricuspid valve
○ Left AV has two cusps - mitral or bicuspid valve
Chordae tendinae - attach to valves. Prevents AV valves from flipping back into atria when ventricles contract. Each papilalry muscle has 2-3 attachments to heart wall - distribute physical stress, coordinate timing of electrical conduction and provide redundancy
Semilunar valves
○ Conenctive tissue lined with endothelium. Control flow into aorta and pulmonary trunk
○ Pulmonary semilunar valve↔between right ventricle and pulmonary trunk
aortic semilunar valve↔between left ventricle and aorta
Blood flow through the chambers
○ In a typical cycle↔followign ventricular contraction, ventricles relax. Pressure inside ventricles drop. Semilunar valves close as blood flows back into ventricles from great vessels. AV valves open - blood flows from atria into ventricles
○ Ventricles contract↔AV valves close as blood attempts to back up into atria. Pressure rises inside of ventricles. Semilunar valves open and blood flows into great vessels
○ Opening and closing of all heart valves - passive.
○ Close when backward pressure gradient pushes blood back
○ open when forward pressure gradient pushes blood forwards
○ I.E. Opening and closing due to pressure differences between chambers.
○ Flimsy AV valves dont require to much pressure to close. Semilunar valves have fibrous nodles in centre - stronger back pressure for short duration
Structure of cardiac muscle
○ Cardiomyocytes↔short, thick branched cells
○ striations of actin and myosin - as in skeletal muscle
○ Central nucleus surrounded by light staining mass of glycogen
○ intercalated discs - join cardiomyocytes end to end
The conduction system of the heart
○ Specialised muscle cells that control and coordinate heart beat
○ cardiac muscle contracts on its own - auto-rhythmicity (without stimulation)
○ Maximum heart rate is 230bpm - maximum rate that AV node can conduct impulses.
§ Comprises an internal pacemaker and nerve like conduction pathways through myocardium
