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Date posted: October 23, 2011

Dr. Ajith Kumar D S
Dept. of Physiology & Biochemistry, GHMC, Calicut.
Email : ajithdevarajan@yahoo.co.in 

Muscle Physiology

  • Muscle form 40 to 50% of body mass.
  • About 600 muscles are identified.

Classification of Muscles:

  • Depending on striations: Striated(Skeletal & Cardiac) & Nonstriated(smooth)
  • Depending on Control: voluntary(Skeletal) & Involuntary(Cardiac & smooth)
  • Depending on situation: Skeletal, Cardiac & Smooth.
  • Muscle fiber or cell has a length b/w 1 – 4cm (Average 3cm) & diameter from 10 – 100microns.
  • 1 myofibril contains 1500 myosin filaments & 3000 actin filaments
  • Sarcomere is the structural & functional unit of skeletal muscle.
    • Length – 2.5 to 3.2 mm.
    • Sarcomere lies b/w two ‘Z’ lines
  • Each myofibril consists of alternate light (I or J band) & dark band (A or Q band).
  • Each sarcomere consist of thin (Actin) & thick (myosin) filaments.
    • Myosin filament is present throughout the ‘A’ band.
    • No movement of myosin during muscular contraction.
  • Actin filaments are formed by 3 types of proteins called actin, tropomyosin & troponin.
  • The skeletal muscle is formed by 75% of water, 20% of proteins & 5%of organic substances.
  • Troponin: is formed by 3 subunits; Troponin I – attached to F actin; Troponin T – attached to tropomyosin; Troponin C – attached to calcium ions.
  • Following are the muscle proteins; Myosin; Actin; Tropomyosin; Troponin; Actinin; Titin; Desmin; Myogen & Myoglobulin.
  • There is no movement in the myosin filament during muscle contraction.
  • Actin filaments slide over the myosin filament during muscle contraction.
  • Tropomyosin covers the active sites of actin.
  • Rheobase: this is the least possible, i.e. (minimum) strength (Voltage) of stimulus which can excite the tissue.
  • Chronaxie: it is the minimum time, at which a stimulus with double the rheobasic strength (voltage) can excite the tissue.
    • Chronaxie of skeletal muscle is shorter than that of cardiac and smooth muscles.
    • Cold lengthens chronaxie. whereas vagal stimulation shortens chronaxie.
  • Refractory period is the period at which the muscle does not show any response to a stimulus.
  • Skeletal muscles are purely aerobic & don’t have any fuel reserve.
  • Dark, light bands & troponin are absent in smooth muscle.
  • The study of electrical activity of the muscle is done by electromyography.
  • The muscle ruptures when it is stretched to about 3 times its equilibrium length. 

Cardiovascular system

  • The syncytium of called physiological syncytium because there is no anatomical continuity of the fibers.
  • SA node the pace maker is a small strip of modified cardiac muscle is situated in the superior part of lateral wall of right atrium, just below the opening of superior vena cava.
  • AV node is situated in the right posterior portion of interatrial septum.
  • Bundle of his run on either side of the interventricular septum.
  • Rhythmicity of different parts of heart:
    • SA node                      : 70 to 80 / min
    • AV node                      : 40 to 60 / min
    • Atrial muscle               : 40 to 60 / min
    • Ventricular muscle      : 20 to 40 / min
  • Velocity of impulse at different parts of the conductive system.
    • Atrial muscle fibres     : 0.3 meter / second
    • Internodal fibers          : 1.0 meter / second
    • AV node                      : 0.05 meter / second
    • Bundle of his               : 0.12 meter / second
    • Purkinje fibers             : 4 meter / second
    • Ventricular muscle fibers : 0.5 meter / second
  • Cardiac cycle includes systole & diastole which practically includes the events of ventricles.
  • When heart beats at the normal rate of 72/min, the duration of cardiac cycle is 0.8 sec.
  • The duration of systole is 0.27 sec & that of diastole is 0.53 sec.
  • The subdivision with duration are
    • Systole
      • Isometric contraction  = 0.05 sec
      • Ejection period            = 0.22 sec
    • Diastole
      • Protodiastole               = 0.04 sec
      • Isometric relaxation    = 0.08 sec
      • Rapid filling                 = 0.11 sec
      • Slow filling                   = 0.19 sec
      • Atrial systole                = 0.11 sec
      • Total duration of cardiac cycle = 0.27 + 0.53 = 0.8 sec.
  • Atrial systole: atrial contract & a small amount of blood enter the ventricles.
  • Isometric contraction: all the valves are closed, ventricles undergo isometric contraction & pressure in the ventricles is increased.
  • Ejection period: semilunar valves opened, ventricles contract & blood is ejected out.
  • Protodiastole: this is the first diastole. The semilunar valves are closed at the end of this period.
  • Isometric relaxation: all the valves are closed, ventricles undergo isometric relaxation & pressure in the ventricles is reduced.
  • Rapid & slow filling: Atrioventricular valves are opened, ventricles relax & filling occurs.
  • Pressure difference
Pressure Right Atrium Left Atrium Right Ventricle Left Ventricle Systemic Aorta Pulmonary artery
Max(mm of Hg) 5 – 6 7 – 8 25 120 120 25
Min(mm of Hg) 0 – 2 0 – 2 2 – 3 5 80 7 – 8
  • End systolic volume is 70 – 90 ml
  • End diastolic volume is 130 – 150 ml.
  • Cause for cardiac murmurs 
Systolic murmur Diastolic murmur Continuous murmur
  1. Incompetence of AV valve
  2. Stenosis of semilunar valves
  3. Anemia
  4. Septal defect
  5. Coarctation of aorta
  6. Stenosis of AV valve
  7. Incompetence of semilunar valves
Patent ductus arteiosus
  • Electrocardiography:

Duration

    • Interval B/W 2 thick lines: (5mm) = 0.2 second
    • Interval B/W 2 thin lines (1mm) = 0.04 second

Amplitude

    • Interval B/W 2 thick lines: (5mm) = 0.5 mV
    • Interval B/W 2 thin lines (1mm) = 0.1 mV

Speed of the paper

    • 25 mm  or 50 mm / second
  • Normal heart rate is 72 / min
  • Tachycardia: increase heart rate above 100 / min.

Waves of normal ECG

Wave / segment From – to Cause Duration(second) Amplitude(mV)
P wave - Atrial depolarization 0.1 0.1 to 0.12
QRS complex - Ventricular repolarization 0.08 – 0.10 Q=0.1 – 0.2R=1

S=0.4

T wave -  Ventricular repolarzation 0.2 0.3
P – R interval Onset of P wave to onset of Q wave Atrial depolarization & conduction through AV node 0.18 (0.12 to 0.2) -
Q – T interval Onset of Q wave & end of T wave Electrical activity in ventricles. 0.4 – 0.42 -
ST segment End of S wave & onset of T wave - 0.08 -
  • In hyperkalemia, ECG shows a tall T wave.
  • In hypokalemia, ECG shows depressed S-T segment.
  • Heart sounds.
Heart sounds Occurs during Cause Characteristics Duration(sec) Relation to ECG
First Isometric contraction & ejection period Closure of AV valves Long, soft, & low pitched. Resembles the word ‘LUBB’ 0.10 – 0.17 ‘R’ wave
Second Protodiastole & part of isometric relaxation Closure of semilunar valves Short, sharp, & high pitched. Resembles the word ‘DUBB’ 0.10 – 014 Precedes or appears 0.09 sec after summit of ‘T’ wave
Third Rapid filling Rushing of blood into ventricles Low pitched 0.07 – 0.1 B/W ‘P’ wave & ‘Q’ wave.
Fourth Atrial systole Contraction of atrial musculature Inaudible sound 0.02 – 0.04 B/W ‘P’ wave & ‘Q’ wave
  • Bradycardia: decrease in rate below 60 / min.
  • Sinus tachycardia: increase in discharge of impulse from SA node, upto 100 / min
  • Sinus bradycardia: reduction in the impulses from SA node, about 40 / min
  • Atrial flutter: Atrial rate is about 250 – 350 / min
  • Atrial fibrillation: rate of 300 – 400 beats / min
  • Ventricular fibrillation: rate is about 400 – 500 / min
  • Bain Bridge reflex (venous reflex) is characterized by reflex increase in Heart rate on venous engorgement of the right atrium.
  • Mary’s law states that the Heart rate and Blood pressure have inverse relationship.
  • Stokes Adams syndrome is characterized by repeated fainting attacks associated with complete heart block.
  • Arrhythmia: irregular heart beat.
  • Cardiac Output:
    • The amount of blood pumped from each ventricle.
  • Stroke volume: the amount of blood pumped out by each ventricle during each beat – 70ml.
    • Stroke volume at rest is 80 – 100 ml.
  • Minute volume: amount of blood pumped out by each ventricle in one minute. Minute volume = stroke volume X heart rate. – 5 liters/per ventricle/minute. 
  • Cardiac Index: the minute volume from ventricle expressed in relation to square meter of body surface area. Normal value: 2.8 ± 0.3 liters / 1 square meter of body surface area / minute.
  • Ejection fraction: the fraction of end diastolic volume that is ejected out by each ventricle. Normal – 60 to 65%.
  • Cardiac reserve: the maximum amount of blood that can be pumped out by the heart above normal value. Normal healthy adult: 300 – 400%.
  • Variations in Cardiac output: (Physiological)
    • Less in children, females, early morning, changing from recumbent to upright position & in sleep.
    • Increased in males, greater body build, day time, emotional upset, after meals, after exercise, high attitude, and later months of pregnancy.
  • Distribution of  Cardiac output:
Organ Amount of blood Percentage
Liver 1500ml 30%
Kidney 1300ml 26%
Skeletal muscles 900ml 18%
Brain 800ml 16%
Skin, bone & GIT 300ml 6%
Heart 200ml 4%
Total 5000ml 100%
  • Factors maintaining  Cardiac output:
    1. Venous return
  • Respiratory pump; Muscle pump; Gravity; Venous pressure; Vasomotor tone.
    1. Force of contraction
    2. Heart rate
    3. Peripheral resistance
  •  Regulation of Heart rate:
  1. 1.    Vasomotor center: bilaterally situated in the reticular formation of medulla oblongata & lower part of pons.
  2. 2.    Motor nerve fiber of heart.
  3. 3.    sensory nerve fiber
  • Haemodynamics:

Factors maintaining volume of flow of blood.

  • Pressure gradient; Resistance to blood flow; Viscosity of blood; Diameter of blood vessels; Velocity of blood flow:
  • Arterial Blood pressure:
    • Systolic pressure: maximum pressure exerted in the arteries during the systole of heart. Normal: 120 mmHg. (range 110 – 140)
    • Diastolic Blood Pressure: minimum pressure in the arteries during the diastole of the heart. Normal: 80 mmHg (range 60 – 90)
    • Pulse pressure: Difference between the systolic pressure & diastolic pressure. Normal: 40 mmHg.
    • Mean arterial blood pressure: this is the diastolic pressure plus one-third of pulse pressure. Normal: 93 mmHg.
    • Variations (Physiological)
      • Less in children, females before menopause, early morning & in sleep.
      • Increased in males, greater body build, and day time, after meals, after exercise, sleep with dreams.
    • Determinants of Arterial blood pressure:

Cardiac output; Heart rate; Peripheral resistance; Venous return; Elasticity & Diameter of blood vessels; Velocity of blood flow; Viscosity of blood

  • Regulation of Arterial blood pressure:
    • Nervous mechanism: by vasomotor center & impulse from periphery
    • Renal mechanism: by regulation of ECF volume & rennin-angiotensin mechanism.
    • Local mechanism

                        Local vasoconstrictors & Local vasodilators

  • Hormonal mechanism:
Hormones increase BP Hormones decrease BP
AdrenalineNoradrenaline

Thyroxine

Aldosterone

Vasopressin

Angiotensin

Serotonin

Vasoactive intestinal polypeptide(VIP)Bradykinin

Prostaglandin

Histamine

Acetylcholine

Atrial natriuretic peptide

  •  Venous pressure:
    • Venous pressure in Jugular vein: 5.1 mmHg (6.9 cm H2O)
    • Venous pressure in superior vena cava: 4.6 mmHg (6.2 cm H2O)
    • Portal venous pressure: 10 mm Hg
    • Hepatic venous pressure: 5 mm Hg.
    • Capillary pressure:
      • Capillary pressure in the arterial end is about 30 – 32 mmHg & venous end is about 15 mmHg.
      • It is high in Kidney (glomerular capillary pressure), about 60 mmHg – responsible for filtration.
      • Low in lungs (pulmonary capillary pressure), about 7 mmHg.
      • Venous pulse: (it is the pressure changes transmitted in the form of waves from right atrium to the veins near the heart)
        • Recording of JVP is called phlebogram.
        • Phlebogram has 3 positive waves – a, c & v and 3 negative waves – x, x1 & y.
        • ‘a’ wave – 1st positive wave & it’s due to atrial systole.
        • ‘x’ wave – fall of pressure in atrium, coincides with atrial diastole
        • ‘c’ wave – its due to rise in atrial pressure during isometric contraction during which the AV valves bulges into atrium.
        • ‘x1 wave – occurs during ejection period, when AV ring is pulled towards ventricles causing distension of atria.
        • ‘v’ wave – occurs during isometric relaxation period or during atrial diastole.
        • ‘y’ wave – due to opening of AV valve & emptying of blood into ventricle. 

Nervous system

  • Neuron is defined as the structural & functional unit of nervous system.
  • Neuron does not have Centrosome so it cannot undergo division.
  • Nissl bodies are organelles containing ribosomes & are concerned with synthesis of protein in neurons.
  • Dendrites are conductive in nature & transmit impulses towards the nerve cell body.
  • Axons are longer process of the nerve cell concerned with transmission of impulse away from the nerve cell body.
  • The myelin sheath envelops the axon except at its ending and at the nodes of Raniver.
  • Myelin sheath is responsible for faster conduction of impulse through the nerve fiber & also acts as an insulating material.
  • Neurotrophins are the substances, which facilitate the growth, survival & repair of the nerve cells.
  • A alpha (Type Ia) nerve fiber is said to be the fastest nerve with a velocity of conduction of 70 to 120 meters / second.
  • Glial cells are very abundant and as many as 10 to 50 times as neurons.
  • Astrocytes form supporting network in brain & spinal cord, form basis for blood brain barrier.
  • Microglia is phagocytic in function.
  • Oligodendrocytes are responsible for the formation of myelin sheath in CNS because schwann cells are absent there.
  • Receptors:
    • Exteroceptors: give response to stimuli arising from outside the body. (Cutaneous, Chemoreceptors & Telereceptors)
    • Interoceptors: give response to stimuli arising from within the body.
    • Cutaneous receptors:
  • Touch receptors: Meissner’s corpuscle & Merkel’s disc (max in lips & fingers)
  • Pressure receptors: Pacinian corpuscles
  • Temperaturereceptor
    • Cold: Krause’s end organ
    • Warm: Raffini’s end organ
    • Warm receptors respond at body temperature of— 30 – 45°C.
    • Cold receptors are activated at body temperature of— 10°C or below.
    • Warm Sensation is carried by — C Fibres.
    • Cold Sensation is carried by — A. & C fibres.
      •  Pain receptors: free (naked) nerve ending. (sensation which return earliest on recovery)
    • Chemoreceptors:
      • Taste: Taste buds
      • Smell: Olfactory receptors
      • Hearing: hairs cells of organ of corti in the internal ear.
      • Vision: Rods & Cones in retina – for visual sensation.
    • Viseroreceptors:
      • Stretch receptors, baroreceptors, chemoreceptors & Osmoreceptors
    • Proprioceptors: give response to change in position – labyrinthine, muscle spindle, golgi tendon, pacinian corpuscle, muscle, tendon & fascia.
  • Neurotransmitters:
    • Excitatory neurotransmitter: is responsible for the conduction of impulse from the presynaptic neuron to the postsynaptic neuron.
    • Inhibitory neurotransmitters: inhibits the conduction of impulse from the presynaptic neuron to the postsynaptic neuron.
Group Name Action
Amino acids GABA Inhibitory
Glycine Inhibitory
Glutamate Excitatory
Aspartate Excitatory
Amines Adrenaline Inhibitory & Excitatory
Noradrenaline Inhibitory & Excitatory
Dopamine Inhibitory
Serotonin Inhibitory
Histamine Excitatory
Others Nitric oxide Excitatory
Acetylcholine Excitatory
  • Superficial reflexes:
Reflex Stimulus Response Center
Corneal Irritation of cornea Blinking of eye Pons
Conjunctival Irritation of conjuctiva Blinking of eye Pons
Nasal Irritation of nasal mucus membrane Sneezing Motor nucleus of V cranial nerve
Pharyngeal Irritation of pharyngeal mucus membrane Retching of gagging Nuclei of X cranial nerve
Uvular Irritation of Uvula Raising of Uvula Nuclei of X cranial nerve
  • Superficial cutaneous reflexes
Reflex Stimulus Response Center – spinal segment involved
Scapular Irritation of skin at the interscapular space Contraction of scapular muscles & drawing in of scapula C5 to T1
Upper abdominal Stroking the abdominal wall below the costal margin Ipsilateral contraction of abdominal muscle & movement of umbilicus towards the site of stroke T6 to T9
Lower abdominal Stroking the abdominal wall at umbilical & iliac level Ipsilateral contraction of abdominal muscle & movement of umbilicus towards the site of stroke T10 to T12
Cremasteric Stroking the skin at upper & inner aspect of thigh Elevation of testicles L1, L2
Gluteal Stroking the skin over glutei Contraction of glutei L4 to S1, S2
Plantar Stroking the sole Plantar flexion & adduction of toes L5 to S2
Bulbocavernous Stroking the dorsum of glans penis Contraction of bulbocavernous S3, S4
Anal Stroking the perianal region Contraction of anal sphincter S4, S5
  • Deep reflexes
Reflex Stimulus Response Center – spinal segment involved
Jaw jerk Tapping middle of the chin with slightly opened mouth Closure of mouth Pons – V cranial nerve
Biceps jerk Percussion of biceps tendon Flexion of forearm C5, C6
Triceps jerk Percussion of triceps tendon Extension of forearm C6 to C8
Supinator jerk or radial periosteal reflex Percussion of tendon over distal end (Styloid process) of radius Supination & flexion of forearm C7, C8
Wrist tendon or finger flexion reflex Percussion of wrist tendons Flexion of corresponding finger C8, T1
Knee jerk or Patellar tendon reflex Percussion of patellar ligament Extension of leg L2 to L4
Ankle jerk or Achilles tendon reflex Percussion of Achilles tendon Plantar flexion of foot L5 to S2
  • Pathological reflexes:
    • Babinski’s sign: there is dorsiflexion of great toe & fanning of other toes. Seen in UMN lesion, also in infants & normal persons with deep sleep.
  • Spinal cord:
    • Extends from foramen magnum to 1st lumbar vertebra.
    • Length – 45 cm in male & 43 cm in females.
    • Below the lumbar enlargement, the spinal cord rapidly narrows to a cone shaped termination called Conus medullaris.
    • Spinal corresponds to 31 pairs of spinal nerves. (C-8; T-12; L-5; S-5; C-1)
    • Grey matter is the collection of nerve cell bodies, dendrites & parts of axons.
    • White matter is a collection of myelinated & nonmyelinated nerve fibers.
    • Neurons in the grey matter of spinal cord
      • Neurons in Anterior gray horn
  • Alpha motor neurons; Gamma motor neurons & Renshaw cells
  • Intermediolateral horn cells
  • Substania gelatinosa of Rolando; Marginal cells; Chief sensory cells & Clarke’s column of cells.
      • Neurons in lateral gray horn
      • Neurons in posterior gray horn

Ascending tracts of Spinal cord:

Situation Tract Function
Anterior white funiculus Anterior spinothalamic tract Crude touch sensation
Lateral white funiculus Lateral spinothalamic tract Pain & temperature sensation
Ventral spino cerebellar tract Subconscious kinesthetic sensations
Dorsal spino cerebellar tract Subconscious kinesthetic sensations
Spinotectal tract Concerned with spinovisual reflex
Fasiculus dorsolateralis Pain & temperature sensations
Spinoreticular tract Conciousness & awareness
Spinoolivary tract Proprioception
Spinovestibular tract Proprioception
Posterior white funiculus Fasciculus gracilis Tactile sensationTactile localization

Tactile discrimination

Vibratory sensation

Conscious kinesthetic sensation

stereognosis

Fasciculus cuneatus

 Descending tracts of Spinal cord:

Situation Tract Function
Pyramidal tracts Anterior corticospinal tract Control voluntary movementsForms upper motor neurons
Lateral corticospinal tract
Extra Pyramidal tracts Medial longitudinal fasciculus Coordination of reflex ocular movementIntegration of movements of eyes & neck
Anterior vestibulospinal tract Maintenance of muscle tone & postureMaintenance of position of head & body during acceleration
Lateral vestibulospinal tract
Reticulospinal tract Coordination of voluntary & reflex movements.Control of muscle tone.

Control of respiration & blood vessels.

Tectospinal tract Control of movement of head in response to visual & auditory impulses.
Rubrospinal tract Facilitatory influence on flexor muscle tone.
Olivospinal tract Control of movements due to proprioception.

Effect of upper motor neuron & lower motor neuron lesion:

  Effects upper motor neuron lower motor neuron lesion
Clinical observation Muscle tone Hypertonic Hypotonic
Paralysis Spastic type of paralysis Flaccid type of paralysis
Wastage of muscle No wastage Present
Superficial reflexes Lost Lost
Plantar reflex Abnormal – babinski’s sign Absent
Deep reflexes Exaggerated Lost
Clonus Present Lost
Clinical confirmation Electrical activity Normal Absent
Muscles affected Groups of muscles are affected Individual muscles are affected
Fascicular twitch in EMG Absent present

Action of sympathetic & parasympathetic divisions of ANS:

Effector organ Sympathetic division Parasympathetic division
Eye Ciliary muscle Relaxation Contraction
Pupil Dilatation Constriction
Lachrymal  secretion Decrease Increase
Salivary secretion Decrease in secretion & vasoconstriction Increase in secretion & vasoconstriction
GIT Motility Inhibition Acceleration
Secretion Decrease Increase
sphincters constriction Relaxation
Gall bladder Relaxation contraction
Urinary bladder Detrusor muscle Relaxation contraction
Internal sphincter Constriction Relaxation
Sweat glands Increase in secretion -
Heart rate & force Increase decrease
Blood vessels Constriction of all blood vessels except those in heart & skeletal muscle Dilatation
Bronchioles Dilatation Constriction

Resting membrane potential of various cells of the body.

  • Resting membrane potential of a skeletal muscle is -90mV.
  • Resting membrane potential of a smooth muscle is -50 to -75mV.
  • Resting membrane potential of a cardiac muscle is -85 to -95mV.
  • The resting membrane potential in the nerve fiber is -70mV.
  • The resting membrane potential in the rods is -40mV.
  • The resting membrane potential of inner ear cell is -60mV.

Brain stem: (medulla oblongata, Pons & Midbrain)

  • Pathway for ascending & descending tracts b/w brain & spinal cord.
  • Important centers for regulation of vital functions in body. 

Medulla oblongata

  • Respiratory centers: inspiratory & expiratory.
  • Vasomotor center: B.P & Heart rate.
  • Deglutition center: Pharyngeal & Oesophageal stage.
  • Vomiting center: induce vomiting.
  • Superior & inferior salivatory nuclei: controls secretion of saliva.
  • Cranial nerve nuclei: nuclei of 10, 11 & 12 cranial nerves.
  • Vestibular nuclei:

Pons

  • Bridge b/w medulla & midbrain.
  • Forms pathway connecting cerebellum with cortex.
  • Nuclei of 5 to 8th cranial nerve.
  • Pneumotoxic & apneustic centers for regulation of respiration.

     Midbrain: (Consist of 2 parts Tectum & cerebral peduncles)

  • Tectum: center for light & auditory reflexes.
  • Cerebral peduncles: control of muscle tone
  • Control of complex  & skilled muscular movements, movement of eye balls

     Thalamus: Ovoid mass of gray matter, situated B/L in diencephalons)

  • Relay center: for sensations (also called functional gateway).
  • Center for integration of sensory impulses: determining the quality of sensations(discriminative & affective nature)
  • Center for sexual sensations.
  • Role in arousal & alertness reactions.
  • Center for reflex activity
  • Center for integration of motor functions.

       Hypothalamus:

  • Control the secretion of Ant. & Post Pituitary hormones & adrenal cortex & medulla.
  • Control of Autonomic nervous system; Heart rate; B.P; Body temp; Food intake (satiety, hunger &thirst); water balance; sleep & wakefulness.
  • Role in behaviour & emotional changes.
  • Regulation of sexual function & response to smell.
  • Role in circadian rhythm.

       Cerebellum:

  • Vestibulocerebellum: regulates tone, posture & receiving impulse for vestibular apparatus.
  • Spinoncerebellum: regulates tone, posture & equilibrium by receiving impulses from proprioceptors in muscles, tendons & joints, tactile receptors, visual receptors & auditory receptors.
  • Corticocerebellum: concerned with the integration & regulation of well coordinated muscular activities.
  • Different parts are represented in an upright manner in cerebellum. (opp: in cerebrum)

       Basal ganglia: (concerned with motor activities of extra-pyramidal system)

  • Control of voluntary motor activity, muscle tone, reflex muscular activity, associated movements.
  • Role in arousal mechanism.

       Cerebral cortex:

Frontal lobe Pre central cortex(Post. Part) Primary motor area(concerned with initiation of voluntary movements & speech) Area 4 – center for movement
Area 4S – suppressor area. Inhibits movements initiated by area 4.
Pre motor area Area 6 – concerned with coordination of movements initiated by area 4.
Area 8 – frontal eye field.
Area 44 & 45(broca’s area) – motor area for speech.
Supplementary motor area Concerned with co-ordinated skilled movements.
Pre –frontal cortex(Ant. Part) Silent area or association areaCenter for higher functions – emotion, learning, memory. Area – 9 to 14, 23, 24, 29 & 32. Center for planned action.Seat of intelligence. Personality of individual.
Parietal lobe Somesthetic area I Area 1 – concerned with sensory perception
Area 2 & 3 – integration of these sensations. Spatial recognition. Recognition of intensity, similarities & diff. B/W stimuli
Somesthetic area II Concerned with perception of sensation.
Somesthetic association area Synthesis of various sensations perceived by S.Area-I. Stereognosis.
Temporal lobe Primary auditory area Area 41, 42 & wernicke’s area – concerned with perception of auditory impulses, analysis of pitch, determination of intensity & source of sound
Auditopsychic area Area 22 – interpretation of auditory sensation
Area of equilibrium Maintenance of equilibrium
Occipital lobe Primary visual area Area 17 – perception of visual impulse
Visual association area Area 18 – Interpretation of visual impulses
Occipital eye field Area 19 – Movements of eye

Limbic system: (It is a group of cortical & sub cortical structures which form a ring around the hilus of cerebral hemisphere)

  • Regulation of olfaction, autonomic functions (B.P, water balance & body temp).
  • Control of circadian rhythm.
  • Regulation of sexual function.
  • Role in emotional state, memory & motivation.
  • Retention of recent memory.
  • Most developed part of Limbic System — Hippocampal formation
  • Major efferent from Limbic system goes to — Mid brain reticular formation.
  • Main function of Limbic system is to — Control the emotional behaviour.

Proprioceptors: (These are receptors which give response to change in the position of different parts of the body).

  • Muscle spindle: gives response to change in length of muscle.
  • Golgi tendon organ: gives response to change in force developed in muscle.
  • Pacinian corpuscle: pressure receptor in fascia, tendon & joints.
  • Free nerve endings:

Vestibular apparatus:

  • Give response to rotatory movements or angular acceleration of the head.
  • Responsible for detecting the position of head during different movements.

EEG: (ELECTROENCEPHOLEGRAM)

  • Alpha rhythm:
    • Frequency: 8 to 12 waves / sec
    • Amplitude: 50µU.
    • Most marked in parieto-occipital area.
    • Obtained in inattentive brain as in drowsiness & light sleep.
  • Beta rhythm:
    • Frequency: 15 to 60 waves / sec
    • Amplitude: 5 – 10µU.
    • Recorded during mental activity or mental tension or arousal state.
  • Delta rhythm:
    • Frequency: 1 to 5 waves / sec
    • Amplitude: 20 – 200µU.
    • Seen in tumour, epilepsy, increased intracranial pressure & mental depression.
  • Theta rhythm:
    • Frequency: 4 to 8 waves / sec
    • Amplitude: 10µU.
    • Seen in children below 5 years. 

SLEEP:

  • Sleep requirement:
    • Newborn infants: 18 to 20 hours.
    • Growing children: 12 to 14 hours.
    • Adults: 7 to 9 hours.
    • Old persons: 5 to 7 hours.
  • Types of sleep:
Rapid eye movement sleep(REM) Non rapid eye movement sleep(NREM)
Eye balls move Absent
Dreams occur Absent
Muscle twitching Absent
20 to 30% of sleep 70 to 80% of sleep
  • Normal amount of C.S.F. in man is 150 C.C,
  • Sympathetic nervous system is controlled by — Posterior hypothalamic nuclei
  • Parasympathetic nervous system is controlled by — Anterior nuclei and part of middle nuclei of hypothalamus.

EYE:

  • Refractory power is measured in dioptre (D).
  • Refractory power of cornea is 42D.
  • Refractory power of lens is 23D.
  • Refractory power of eye at rest is 59D.
  • Focal length of cornea is 24mm.
  • Focal length of lens is 44mm.
  • The wave lengths of visible light are approximately 397 to 723 nm.
  • There are about 6 million cones & 12 million rods in human eye.
  • Rods are responsible for dim light or night vision or scotopic vision.
  • Cones are responsible for colour vision, sensitive to day light & acuity of vision.
  • Rhodopsin is the photosensitive pigment of rods cells.
  • Photosensitive pigment in cones are
    • Porpyropsin – Red
    • Iodopsin – Green
    • Cyanopsin – Blue
  • Electroretinogram is the instrument to record the electrical basis of visual process.
  • Test for visual acuity – snell’s chart (distant vision) & Jaeger’s chart (near vision).
  • Test for color blindness – Ishihara’s colour chart.
  • Mapping of visual field – perimetry.
  • Nearest point at which the object is seen clearly is about 7 to 40cm.
  • Farthest point is infinite.
  • Myopia (short sightedness) is corrected by concave lens.
  • Hypermetropia (long sightedness) is corrected by convex lens.
  • Astigmatism is corrected by cylindrical lens.
  • Presbyopia is corrected by convex lens.

EAR:

  • Ear is sensitive to sound between 1000 to 4000Hz range.
  • Hairs cells in organ of corti are the receptors for auditory sensation.
  • Sound becomes painful above 140db.
  • Auditory centers – 41, 42 & also auditopsychic area 22.

TONGUE:

  • Sense organ of taste sensation is taste buds.
  • There are about 10,000 taste buds & each taste bud is replaced in every 10 days.
  • Each taste bud consists of 4 types of cells and is supplied by about 50 nerve fibres.
  • Receptors are type III cells of taste buds.
  • Taste center – opercular insular cortex (lower part of post central gyrus).
  • Bitter taste has very low threshold – 1 in 2,000,000.
  • Sweet taste has high threshold – 1 in 200.
  • Locations of taste buds are: sweet – tip; salt – dorsum; sour – side; bitter – posterior.

SMELL:

  • Olfactory mucus consists of 10 to 20 million olfactory receptor cells.
  • Human nose can distinguish 2000 to 4000 different odours.

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