1. Physl important notes CNS Mid1

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3. Function of glial cells: 1.Astrocytes Functions 1.Physical support to neurons 2.Help transfer nutrients to neurons 3.Take up and degrade released neurotransmitter 4.Enhance synapse formation & ↑ Synaptic transmission 5.Maintain normal Brain ECF ion concentration 6.Formation of blood – brain – barrier 7.Repair of brain injuries & formation of neural scar tissue 2.Oligodendrocytes Functions 1.Forms myelin sheath in the CNS.

4. 3.Microglia Functions 1.Phagocytosis [defense cells of CNS] 2.Release nerve growth factor 4.Ependymal Cells Functions 1.Line internal cavities of brain and spinal cord 2.Formation of Cerebrospinal fluid [CSF]. 3.Work as Neural Stem Cell – to form new neurons and glial cells

5. Basal Nuclei Functions: – Co-ordination of movements – Muscle tone regulation – Posture maintenance

6.  Thalamus All sensory information passes. Crude awareness of sensation.

7. Cerebellum  Functions: – Balance of body. – Muscle tone. – Co-ordination and planning of skilled movements e.g. dance.

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9. SPINAL CORD Function: – Conduit for Information passage To & fro Brain – Center for some reflexes

10. REFLEXES Examples a.Reflexes carry out the automatic actions of swallowing, sneezing, coughing, vomiting. b.Reflexes maintain balance and posture; e.g., spinal reflexes control trunk and limb muscles. c.Brain reflexes involve reflex center in brainstem; e.g., reflexes for eye movement.

11.  Polysynaptic reflex  e.g. Withdrawal reflex, Abdominal reflex, Plantar reflex  Stretch reflex:  Sudden stretch to a muscle leads to contraction of that muscle is known as stretch reflex.  Stretch Reflex is a basic spinal reflex. Example Knee jerk The 5 components of Stretch Reflex – Sensory receptor – Muscle Spindle in skeletal muscle – Afferent pathway – 1a fibers – Center – spinal cord – Efferent fibers – α-motor neuron – Effector organ – skeletal muscle contraction

12. Types of muscle fibers I.Extrafusal muscle fibers – Takes part in muscle contraction – Supplied by α - motor neuron II.Intrafusal muscle fibers – Also called as Muscle Spindle – Receptors for stretch reflex – supplied by γ - motor neuron

13. Types of Nerve Fibers Know only the major function

14. Types of motor neuron α - motor neuron – Supply Extrafusal fibers γ - motor neuron – Supply Intrafusal fibers

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16. Sensory receptor Every receptor is most sensitive to a particular modality of stimuli. That specific form of energy to which the receptor is most sensitive is called as its Adequate Stimulus. – e.g. rods & cones are stimulated by light not heat, sound etc

17. Know the type and the function only

18. Difference Between Receptor potential  In the Receptor  Graded  Doesn’t obey all or none rule  Can be summated  Unpropagated Action potential  In the Sensory Nerve fiber  Not Graded  Obeys all or none rule  Not summated  Propagated

19. Adaptation or Desensitization I.Phasic Receptors: Rapidly Adapting Receptors – E.g. pacinian corpuscles, Meissners corpusle. – For Touch, Pressure & Smell etc. II.Tonic Receptors: Slow Adapting receptors – E.g. Nociceptors, muscle spindles, Proprioceptors – For Pain, Body position etc.

20. Receptor field Receptor field of a sensory unit is the area from which a stimulus produces response in that unit. Smaller the receptive field – More precise the information e.g. Finger tips Larger the receptive field- less precise the information e.g. Back, arms, legs.

21. Fiber type : A  Number: II Origin: Muscle spindle - flower-spray ending, touch, pressure

22. Primary afferent fibers which carry cutaneous sensations are – Large myelinated fiber A α – proprioception – Large myelinated fiber A β – touch, pressure. – Small myelinated fiber Aδ – fast pain, Temp – Small unmyelinated C fibers – slow pain, Temp

23. Sensory pathway Dorsal Column Medial Lemniscal system Also called as Posterior column Tract or Tracts of Goll & Burdach or Fasciculus Gracilis and Cuneatus Carries sensations of fine touch, position, vibration, two point discrimination & stereognosis. Anterolateral system Consists of … 1.Anterior (Ventral) spinothalamic tract carries crude touch and pressure, 2.Lateral spinothalamic tract carries pain and temperature.

24. Deferent between DORSAL COLUMN PATHWAY Carries fine touch, position, pressure, vibration, two point discrimination, stereognosis Afferent sensory fibers aβ type. Very fast velocity 30 – 70 m/s ANTEROLATERAL PATHWAY Carries pain & temperature (lat. Sp.Th) Crude touch & pressure (vent, sp. Th) Afferent sensory fibers aδ 6 – 30 m/s (myelinated) fast pain C fibers – 0.5 – 2 m/s (unmyelinated) slow pain

25. Temperature Afferent from cold receptors – Aδ & C fibers. Afferent from warm receptors – C fibers. Temperature sensation is carried via lateral spinothalamic tract.

26. Aδ (myelinated) : for fast pain”sharp loclized” C fibers (unmyelinated): slow pain “ dull, diffuse” Both Aδ & C fibers terminate in dorsal horn.

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28. Brain Analgesic System Brain has built in analgesic system. By sending message through descending analgesic pathway to the inhibitory neuron in the Dorsal horn cell of spinal cord. Brain descending pathways release Enkephalin which bind with opiate receptors at afferent pain fiber terminals in Dorsal horn of spinal cord and work like Morphine (powerful analgesic). Endorphin, Enkephalin and Dynorphin are endogenous or natural analgesic system. They suppress release of substance P.

29. Somatosensory cortex (S1 area) It is located in post central gyrus of the cerebral cortex. There is detailed localization of the fibers from various parts of the body. Somatosensory cortex is a site of perception of – Somasthetic sensation [touch, pain, temperature, pressure] – Proprioception The arrangement of thalamic fibers in S1 is such that parts of body are represented in order, along the post central gyrus with the feet on the top & head at the lower end of the gyrus.

30. Somatosensory cortex (S1 area) Here different body parts are not represented equally Size of cortical receiving area for impulses from a particular part of the body is proportionate to the No. of receptors. Thus very large area is occupied by impulses coming from lips, face, and hand (thumb) also parts of mouth concerned with speech. Trunk & back has small area of presentation in sensory cortex. Each side of the cortex receives information from opposite side of the body. From here many of signals spread directly to motor cortex, play a major role in controlling motor signals that activate muscle contraction

31. Somatosensory area II SII is located in the superior wall of the sylvian fissure, the fissure that separate the temporal lobe from the frontal & the prietal lobe. Face is presented anteriorly, arms centrally & legs posteriorly. The presentation of the body parts on sylvian fissure is not as complete & detailed as in post central gyrus. Little is known about role of somatosensory area II (SII). Signals enter into SII from brain stem, also SI area and other areas of brain visual & auditory. Projection from SI are required for function of SII.

32. Somatosensory Association Area Located in parietal lobe behind area SI. It receives signals from ; 1.Somatosensory area I 2.Thalamus 3.Visual cortex 4.Auditory cortex Effect of removing … – Person looses the ability to recognize objects felt on the opposite side of the body, he looses the sense of form of his own body on the opposite side also. He forget it is there. – This complex sensory deficit is called Amorphosynthesis.

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34. CORTICOSPINAL TRACTS: It is the most important motor pathway from motor cortex Origin: – 30% from Primary Motor Cortex – 30% from Premotor and Supplementary Motor Area – 40 % from Somatosensory Area Course: – passes through posterior limb of internal capsule and downwards through brainstem. – Majority of fibers (80%) than cross in lower medulla to the opposite side and descend as lateral Corticospinal tracts. – 20% uncrossed continue as Anterior Corticospinal Tract. Eventually most of them also cross before termination in Spinal Cord

35. CORTICOSPINAL TRACTS: Termination: – Terminate principally on the Interneurons, in the intermediate region of cord grey matter, – A few terminate on sensory relay neurons in dorsal horn and – A few terminate directly on Anterior Motor Neuron. – direct innervation of alpha motor neurons by pyramidal tract axons is mainly to distal muscles and is associated with the ability to execute fine, precise movements

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37. RUBROSPINAL TRACT Functions - Involved in movements of distal limbs (hand & feet) also regulates tone and posture. It is excitatory to flexors and inhibitory to extensor muscles.

38. VESTIBULOSPINAL TRACT Function - Excitatory to ipsilateral extensor. Inhibitory to flexor muscles Regulates muscle tone for maintaining balance in response to head movement

39. Difference between Pyramidal and Extrapyramidal Tract PYRAMIDAL TRACTS 4.80 % of Corticospinal tracts (lateral) cross in medulla 20 % of corticospinal tract (ventral) cross in spinal cord Because of crossing cerebral cortex controls opposite side of the body 5.Function: - Lat. Corticospinal tract – fine movement of fingers eg. Writing, needle work - Ventral corticospinal tract – Axial or Postural Movement EXTRA PYRAMIDAL TRACTS Major extra pyramidal tracts, some cross and others are uncrossed Function: Control of body posture involving involuntary movements of axial and Proximal limb muscle

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41. BASAL NUCLEI - FUNCTIONS Modulation of motor activities through neuronal circuits. Maintain purposeful motor activity while suppressing unwanted or useless movement. Change the Timing and Scale the Intensity of Movements Basal ganglia function in association with the corticospinal system to determine & control complex patterns of motor activity.

42. BASAL NUCLEI - FUNCTIONS Regulate muscle tone - Inhibit muscle tone throughout the body Monitor and coordinate slow, sustained contractions related to posture and support. Prevent abnormal involuntary movements. Control group of movements for emotional expression. Role in procedural learning, routine behaviors or "habits" such as bruxism. Role in Memory, emotion, Reward Learning and other cognitive functions.

43. BASAL NUCLEI - CONNECTIONS Main input: Comes from the cerebral cortex (motor area) and projects to the Striatum (Caudate nucleus & Putamen) Main output: Is from Globus Pallidus via the thalamus to the cerebral cortex (motor area)

44. GLU GABA GLU GABA GLU GABA GLU

46. Parkinson’s Disease Clinical symptoms Rigidity – Cogwheel, Lead Pipe Tremor (Resting) – Pill rolling type Hypokinesia/Akinesia - poverty and slowness in initiating and carrying out different motor movement. Face – expressionless, Mask like face Blinking of eyelid is reduced Writing becomes small – micrographic and spidery Changes in posture – Stoop is characteristic Gait – becomes hurrying, festinant, short and shuffling with poor arm swinging