Cardiac Muscle Tissue | Additional Study Material for NEET PDF Download
Musculature System
Cardiac Muscle
It is special type of muscle which found only in heart so it is also called as cardiac muscle. On the basis of structure it is striated type of muscle. It is also cylindrical fibre. Fibre are branched. Many transverse septa are found in the muscle fibre which are called as intercalated disc. Junctional region b/w the cell membrane called intercalated discs & these are made up of sarcolemma.
Due to septa fibres are divided into many segments each segment is Uninucleate. Each segment called individuals cells.
Dark & light line also found in the Muscle fibre. Intercalated disc, helps in the propagation of impulse & contraction. It is also Non fatigue type muscle. Its contraction is not controlled by will power of animal.
On the basis of function it is involuntary type & control by pacemaker (SA, AV & Purkinje fibres). Both central nerve & autonomic nerves are supplied to this type of muscle.
| Striated | Non Striated | Cardiac |
1. | They are present in upper limb & lower limb etc. | Iris of eye (Ciliary muscle of eye) Urinary bladder, Urinogenital tract, Dermis of skin - Erector pill muscle of dermis | They are present in walls of Heart |
2. | Cylindrical | Spindle in shaped | Cylindrical |
3. | Fibres Unbranched | Unbranched | Fibres are branched |
4. | Multi Nucleated fibres | Uninucleated | Uninucleated |
5. | Light and Dark band present | Absent | Present |
6. | Oblique bridges & Intercalated disc absent | Absent | Present |
7. | Controlled by CNS. | ANS | Both CNS + ANS |
8. | Blood supply abundant. | less | Richly Blood supply |
9. | Soon fatigue. | Do not get fatigue | Never fatigued |
PROPERTIES OF MUSCLES
Terminology
1. Origin - fixed end of muscle (Proximal end).
Insertion - Distal end of muscle which is attach to bone (Movable end).
2. Excitability - Muscles responds to stimuli which can be nervous, chemical, electrical & thermal & mechanical.
Conductivity - Stimulus acting in one region of muscle fibres propagated to all parts within no time.
Contractility - on being stimulated the muscle fibres contract & shorten followed by relaxation.
3. Threshold Stimulus - Intensity of stimulus below the threshold value which does not produces contraction in muscle fibres is called subthreshold stimulus.
Stimulus stronger than threshold one is called suprathreshold stimulus.
4. All or none law :-Response of muscle fibre is maximum whether the stimulus has threshold value or suprathreshold value. Response is absent when intensity is subthreshold.(Below threshold value)
5. Muscle twitch - It is single isolated contraction of muscle fibres due to single stimulus. Muscle curve or kymograph indicates three phases :
(a) Period of latent excitation (Latent period) Interval between the application of appropriate stimulus & initiation of contraction It is 0.01 sec. in skeletal muscle. 3 sec. in smooth muscle.
(b) Contraction phase - Duration for which muscle remain contracted state. It is 0.04 sec. in skeletal muscle. 20 sec. in smooth muscle.
(c) Relaxation phase - Interval for contracted muscle to regain its original/relaxed state 0.05 sec. in skeletal muscle. 23 sec. in smooth muscle.
6. Refractory period – It is period between two twitches during this muscle does not respond to second stimulus after single twitch. It is 0.002 - 0.005 second in skeletal muscles and 0.1 - 0.2 second in visceral muscles.
7. Summation of stimuli - two subliminal stimuli Applied simultaneously get added up & Evoke the response
Muscle response = (1st stimulus + 2nd stimulus ≥ threshold value)
However a muscles consist of large no.of muscle fibres with different threshold value so in intensity of stimulus increases contraction of muscle although individual fibres obey all/none law.
Summation of IInd stimulus during contraction phase
8. Muscle tone - In relaxed muscles, a few fibres always undergoing contraction alternately so maintain the health of muscles It is known as Muscle tone.
9. Tetanic condition - It is sustained muscles contraction due to rapid series of Impulse, During this relaxation of muscles does not take place.
10. Paralysis - Supply of motor nerve impulse completely cut off. So function of muscle contraction is stopped.
11. Shivering - Involuntary contraction of muscles to make body warm.
12. Muscle tension - force produced during contraction of muscle is known as muscle tension.
Isometric –
Contraction occur when a muscle is stimulated adequately but is prevented to shorten. e.g. By applying too heavy load against the muscle so that the muscle contract but cannot lift the load at all ext. work done is zero.
Isotonic –
When muscle is stimulated adequately & is allowed to shorten, than the contraction is called Isotonic some external work is done. Technically called a load is lifted.
13. Antagonistic muscles -They are pair of muscles which causes opposite movement at the same site when one muscle is contracting, the other is relaxes & vice versa e.g - Biceps (flexor) & Triceps of arms (extensor)
14. Motor unit - Groups of mucles fibres supplied by single motor neuron. It is a functional unit of muscles because all the muscles fibres of motor unit contract & relax simultaneously.
15. Cori cycles – Lactic acid accumulated in muscles during sustained contraction. formed lactic acid transported in blood as blood lactate to liver where it changes into liver glycogen which is changed in to glucose.
16. Speed of –
Skeletal muscle = 0.1 sec. per contraction per cycle
Cardiac muscle = 0.8 sec. per contraction per cycle
Smooth muscle = 46 - sec. per contraction per cycle
Red (slow) muscle | Pale (fast) muscle |
1. Myoglobin content is ore. So, it is red | Myoglobin content is less So, it is pale |
2. Sarcoplasmic reticulum is less extensive | Sarcoplasmic reticulum is more extensive |
3. Blood vessels are more extensive | Blood vessels are less extensive |
4. Mitochondria are more in number | Mitochondria are less in number |
5. Response is slew with long latent period | Response is rapid with short latent period |
6. Contraction is less powerful | Contraction is more powerful |
7. This muscle is involved in prolonged and continued activity as it undergoes sustained contraction | This muscle is not involved in prolonged and continued activity as it relaxes immediately |
8. Fatigue occurs slowly | Fatigue occurs quickly |
9. Depends on cellular respiration for ATP production | Depends on glycolysis for ATP production. |
2. Consumption of stored glycogen, ATP, CTP
Infatigue –
(i) Increase latent period and phase of relaxation.
(ii) decrease height of contraction
19. Rigor Mortis – After death fresh supply of ATP become impossible so once the local store of ATP molecule are exhausted. Due to non availability of ATP/C.P. deattachment of myosin from actin cannot take place resulting in permanent state of contraction of muscle. This phenomenon is called rigor mortis. This condition helps fixation of the hour of death.
20. E.D.T.A. (Ethylene Diamine tetra acetic acid) injected inside muscle combined with Ca+ and stops contraction.
21. Muscle and nerve exitability is reduced by K+.
22. During muscle contration chemical energy changed into mechanical energy.
23. Over streching of tendon is called sprain.
MUSCLE TYPES ON BASIS OF MOVEMENTS
1. Flexor = Fore arm move in upward direction. (Bend) Bending of part over one another E.g. biceps brachii Extensor - Fore arm move in downward direction. Straighting of bending part Eg. Triceps
2. Adductor - Toward body axis. Towards the body Lattissimus dorsi brings the arms towards body Abductor - Upper & lower limb move away from body axis. Away from the body (midline) deltoids
3. Pronator - Palm state in down. Rotate downward e.g pronater teres Supinator - Palm state in upward Rotate upward e.g brachioradialis
4. Dilatation - Diameter increases, widening of of Iris (radial muscle of iris) Constrictor - Diameter decreases, Closing an aperture - sphincter ani closes anus
5. Depressor - Lower Jaw move in downward direction. Lowering part depressor mandibular Elevator - Lower Jaw move upward direction. Raising the part e.g. Masseter.
6. Median Rotation :- Upper & lower limb rotate in inward direction.
Lateral Rotation :- Out ward direction rotation.
7. Inversion :- When sole of foot turn toward body axis.
8 . Eversion :- Away from body axis
Aryepiglotticus muscle is called Hilton muscle.
Gastrocnemius muscle present in shank.
Sartorius the Longest muscle of body
Gluteus maximus (Buttock muscles) – Largest muscle of body.
Stapedius – Smallest muscle of body.
In Human beings 639 muscle are found. 634 muscle are paired and 5 muscle are unpaired. 400 muscles are striated & most of the muscles are found in back reason & number of back muscles are 180. Jaw muscles are strongest. Longest smooth muscle is present in uterus of pregnant lady.
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Nov 17, 2024 Last updated |
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