Dr. Ajith Kumar D S
Dept. of Physiology & Biochemistry, GHMC, Calicut.
Email : email@example.com
- 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.
- 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
- Isometric contraction = 0.05 sec
- Ejection period = 0.22 sec
- 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|
||Patent ductus arteiosus|
- Interval B/W 2 thick lines: (5mm) = 0.2 second
- Interval B/W 2 thin lines (1mm) = 0.04 second
- 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
|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|
|Skin, bone & GIT||300ml||6%|
- Factors maintaining Cardiac output:
- Venous return
- Respiratory pump; Muscle pump; Gravity; Venous pressure; Vasomotor tone.
- Force of contraction
- Heart rate
- Peripheral resistance
- Regulation of Heart rate:
- 1. Vasomotor center: bilaterally situated in the reticular formation of medulla oblongata & lower part of pons.
- 2. Motor nerve fiber of heart.
- 3. sensory nerve fiber
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|
|Vasoactive intestinal polypeptide(VIP)Bradykinin
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.
- 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.
- 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
- 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)
- 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.
- Stretch receptors, baroreceptors, chemoreceptors & Osmoreceptors
- Proprioceptors: give response to change in position – labyrinthine, muscle spindle, golgi tendon, pacinian corpuscle, muscle, tendon & fascia.
- 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.
|Amines||Adrenaline||Inhibitory & Excitatory|
|Noradrenaline||Inhibitory & Excitatory|
- Superficial reflexes:
|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:
|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|
|Posterior white funiculus||Fasciculus gracilis||Tactile sensationTactile localization
Conscious kinesthetic sensation
Descending tracts of Spinal cord:
|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|
|Plantar reflex||Abnormal – babinski’s sign||Absent|
|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|
|Salivary secretion||Decrease in secretion & vasoconstriction||Increase in secretion & vasoconstriction|
|Urinary bladder||Detrusor muscle||Relaxation||contraction|
|Sweat glands||Increase in secretion||-|
|Heart rate & force||Increase||decrease|
|Blood vessels||Constriction of all blood vessels except those in heart & skeletal muscle||Dilatation|
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.
- 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:
- 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.
- 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.
- 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.
|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:
- Give response to rotatory movements or angular acceleration of the head.
- Responsible for detecting the position of head during different movements.
- 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 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|
|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.
- 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 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.
- 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.
- Olfactory mucus consists of 10 to 20 million olfactory receptor cells.
- Human nose can distinguish 2000 to 4000 different odours.
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