Lecture 9- Body Tissues 1 Flashcards
State the two types of Muscle cell types
Striated muscle
Non striated muscle
State the 2 types of striated (striped) muscle
Skeletal muscle
Cardiac muscle
Features of skeletal muscles
Myoglobin present
Voluntary control
Direct nerve-muscle communication
Features of cardiac muscles
Myoglobin present
Involuntary control
Indirect nerve - muscle communication
Example of a non striated muscle
Smooth muscle
Features of smooth muscles
Myoglobin absent
Involuntary control
No direct nerve-muscle communication
Structure and role of Myoglobin
A red protein that is structurally similar to a single subunit if haemoglobin.
Stores only oxygen and provides it to working striated muscles ( cardiac and skeletal ).
Receives oxygen from haemoglobin at low pH
What occurs when striated muscles (skeletal and cardiac )dies (Muscle Necrosis)?
Symptoms?
Myoglobin is released into the bloodstream (myoglobinuria) and this can Cause renal damage as it sometimes blocks the kidney ducts .
Symptoms include tea coloured urine as the kidneys remove myoglobin from the blood into the urine
Muscle cell component terminology
Sarcolemma? Sarcoplasm? Sarcosome? Sarcomere? Sarcoplasmic reticulum?
Sarcolemma : the outer membrane of a Muscle cell
Sarcoplasm : the cytoplasm of a Muscle cell
Sarcosome: the mitochondrion
Sarcomere: the contraction unit in striated muscle
Sarcoplasmic reticulum: smooth endoplasmic reticulum of a Muscle cell
Muscle is attached to the bone through tendons.
Tendons sheet have dense connective tissue.
What is the name of the outermost layer sheet?
Epimysium
The name of the structure in which group of skeletal muscle cells (fibres) are held in?
Dense connective tissue wrapped around each fascicles ?
Loose connective tissue wrapped around each muscle fibre cell?
Fascicles ( all fascicles surrounded by epimysium-dense connective tissue)
Each fascicle wrapped around with dense connective tissue perimysium
Each individual muscle fibre cell wrapped in loose connective tissue called endomysium and contains numerous myofibrils.
Main function of skeletal muscle fibres (striated muscle cell ) is to contract and they do this in a coordinated manner. What is the movement dependent on?
When does movement occur?
Movement dependent on the direction of muscle fibre contraction ( not easy to predict because fibres have lots of different shapes).
Movement occurs when the point of origin and point of insertion (bones) crosses a joint.
Tension created at origin tendon point while o emend created at insertion tendon point.
What are intrinsic muscles of the tongue?
Muscles within the tongue that allow the tongue to change shape but not position as they are not attached to a bone but to other muscles in the tongue.
What are extrinsic muscle of the tongue?
They are connected to bones and cartilage by tendons and they help protrude the tongue. Retract it and move it side to side.
E.g Thyroid cartilage, Hyoid bone
What accounts for the mobility of skeletal muscles of the tongue ?
The plasticity and strength of the connective tissues and the multidirectional orientation of the muscle fibres .
Key point to work out skeletal muscle electron micrographs
How are the nuclei arranged in transverse section? (Cross sectional)
How are the nuclei arranged in Longitudinal section?
Peripheral ( on the edge of cell)
In rows
Muscle cells are multinucleate
What is the capillary network surrounding skeletal muscle fibres (striated muscle cell) related to?
To the thickness of the fibre : the thicker it is, the thicker the blood vessels around it
Thin fibres require less blood so thinner bv
Thick fibres require more blood so thicker bv
Structure of myofibrils (found in muscle cells fibres)
Made up of sacromeres
Thin filament called Actin
Thick filament called Myosin
Each sacromeres consists of I band, A band, H zone and Z line.
I band consists of only actin filaments
A band consists of both myosin and actin filaments
H stone consists of only myosin filament - M line which is the middle of the myosin filaments
Z line marks the start and end of a sacromere
Striated skeletal muscles cell fibres contractions depend on what type of muscle fibre it is.
State the three different type of skeletal muscle fibres
Slow twitch muscle fibres ( Type 1) -mostly red
Intermediate muscle fibres - mixture of red and white fibres (uses up energy is white then red)
Fast twitch muscle fibre (type 2a and 2b)- mostly white
Each fibre has its own neural input.
Features of slow twitch fibres ( Type 1)
Slow oxidative fibres Rich capillary supply Aerobic respiration High myoglobin levels Many mitochondria Manny cytochromes Red Fatigue resistance Endurance type activities Used in standing / walking
Mainly uses fatty acids to generate lots of ATP and CO2
Features of fast twitch fibres ( type 2A)
Fast oxidative glycolytic fibres (absence of oxygen) Rich capillary supply Aerobic High myoglobin levels Many to intermediate mitochondrial numbers Many cytochromes Red to pink in colour Moderate fatigue resistance Assists type 1 and 2B activities
Mainly uses fatty acids and glycogen to produce energy , initially CO2 produced then lactate
Features of fast twitch fibres (type 2B)
2X fast glycolytic fibres (absence of oxygen ) Poor capillary supply Anaerobic Low myoglobin levels Few mitochondria Few cytochromes White in colour Rapidly fatigue Strength filled activities Jumping, running, sprinting
Mostly glycogen stores used to produce lots of lactate and little ATP
Structure of striated cardiac muscle fibres
Striated
Centrally positioned nuclei ( 1 or 2 per cell)
Lots of glycogen
Intercalated disks - has lots of gap junctions , communication between cell possible. Allows simultaneous contractions .
Branching occurs in these cells
Compare and contrast cardiac and skeletal muscles
Both striated muscles
Contraction mechanism are similar ( sarcomeres )
-cardiac uses troponin I and T (can indicate heart attack)
-skeletal uses troponin C
Cardiac nuclei is central ; skeletal nuclei is peripheral
Sarcomere not so developed in cardiac
No t tubules in cardiac sarcoplasmic reticulum
Cardiomyocyte are the only contractile cell type in cardiac muscle fibres and they communicate through gap junctions in intercalated disks.
Electron micrograph of a cardiac muscle fibre ( atrial)
Z lines not lying up like in skeletal Endomysium thicker ANP granules ( atrial natriuretic peptide) found in endomysium
What are ANP and BNP?
ANP-atrial natriuretic peptide
BNP- Brain type ^^
Naturietic peptides released by heart during heart failure .
If atrial is affected then ANP is released, if ventricles then BNP.
When cardiac muscle is under stress, release these peptides. It reduces arterial pressure by decreasing blood volume and blood pressure and systemic vascular resistance.
BNP-Vasodilation-reduce bp
ANP-Glomerulus - Natriuresis Diuresis - reduce bv- reduce bp
Difference between Hypertrophy and Hyperplasia
Hypertrophy is the enlargement of individual cells
Hyperplasia is the multiplication of cells
Hypertrophy and Atrophy
Hypertrophy is the enlargement of cardiomyocytes
Atrophy is the shrinkage of cardiomyocytes
Heart is bigger/smaller than normal heart
The conduction system of the heart- how the heart passes on electrical impulse
Sinoatrial node receives impulse from para/sympathetic neurones from brain which passes on to the atrioventricular node. Bachman’s bundle Akins simultaneous contraction of atria . Time delay before AVN passes on to bundle of his so that atrium can contract fully into ventricles. Signal branches of into left and right bundle of his branch and into the purkinje fibres at the bottom of the heart causing it to contract.
Features of Purkinje fibres (cardiomyocytes)
Abundant in glycogen Sparse myofibrils Extensive gap junctions sites Good conductor of electricity Not as fast as muscle fibres because of glycogen which prevents movement of electrical conduction Full of myoglobin
Features of smooth muscle cells
- Spindle shaped with a single central large nucleus
- Not striated, no sarcomere and no t tubules
- Fewer mitochondria
- Capable of being stretched substantially
- Contraction relies on actin-myosin interactions but is slower and more sustained and require less ATP(filaments found in sarcoplasm and remain there until a signal is received in which they contract)
- Can remain contracted for hours or days
- Responds to stimuli in form of nerve signals, hormones, drugs o local concentrations of blood gases.
- Form sheets, bundles or layers containing thousands of cells
- Numerous caveolae(small cave like invaginations)
- Gap junction - allows calcium and actin molecules to enter
Myosin and actin come together on focal adhesion plaque located in plasma membrane and sarcoplasm -contraction machinery
Location of smooth muscle fibres
Forms contractile walls of passageways or cavities
- vascular structures
- gut, respiratory tract , genitourinary system
Smooth muscle fibres is an involuntary muscle so it can have its mind of its own .
What are the disorders it can be a clinical significance in ?
- High blood pressure
- painful menstruation
- asthma
- abnormal gut mobility (diarrhoea)
- urge incontinence (detrusor muscle instability - control bladder for urine)
Structure of the Smooth muscle of the gut ( muscularis externa)
Inner circular layer
Outer longitudinal layer
Is it possible for skeletal muscle to repair ?
Yes
They cannot divide but can regenerate by mitotic activity of satellite cells ( stem cells) so that hyperplasia ( multiplication of cells ) follow muscle injury.
Satellite cells can fuse with existing cells to increase mass ( skeletal muscle Hypertrophy )
Is it possible for cardiac muscle to repair ?
Yes is children
No in adults -incapable of regeneration
After damage , fibroblasts lays down fibres and this causes scarring
Is smooth muscle repair possible ?
Yes
They retain their mitotic activity and can form new smooth muscle cells . Can undergo hyperplasia . ESP in pregnant uterus.
