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Chapter 11

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Chapter 11

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  1. Chapter 11 The Brain & Spinal Cord

  2. Introduction • Brain & s.c. comprise the CNS • Brain is protected by cranium & meninges – • Consists of 3 layers: 1. dura mater 2. 3. pia mater

  3. Meninges • Dura mater – • Arachnoid mater – thin & weblike; no b.v. or nerves SUBARACHNOID SPACE – 3. Pia mater – delicate; w/b.v. & nerves; attached directly to brain & follows contours

  4. Importance of Meninges • dural sinus – space formed when d.m. splits into 2 layers • subdural hematoma – fluid & blood collects under d.m. from trauma • Meningitis –

  5. Partitions of Dura mater • Falxcerebelli – 2. Falxcerebri – b/t rt. & lt. cerebral hemispheres • Tentorium cerebelli – b/t cerebrum & cerebellum

  6. Protection of Spinal Cord • S.C. protected by bony vertebrae & same 3 meninges • Epidural space –

  7. The Spinal Cord • Consists of 31 segments • Each gives rise to a spinal nerve • Provides 2-way communi- cation b/t brain & body • 2 main functions: 1. 2.

  8. The Spinal Cord • Beginning pt. – foramen magnum • Ending pt. – conus medullaris (narrow pt. b/t L1-L2) • Cauda equina –

  9. Cross Section – Spinal Cord • Gray matter – • White matter – • 2 grooves divide s.c. into rt. & lt. halves: posterior median sulcus anterior median fissure

  10. Cross Section - S.C. • Central canal • Gray commissure – connects “wings” of “butterfly”

  11. Nerve Tracts • White matter in s.c. consists of fibers called nerve tracts; provide 2-way communication b/t brain & s.c.; • 2 types: 1. ascending – *In the medulla, fibers cross over

  12. Nerve Tracts 2. descending – * In the medulla, fibers cross over

  13. Reflexes • S.C.- center for reflexes (automatic, subconscious responses) • Reflexes control many involuntary actions (HR, resp.rate, swallowing, sneezing, etc.) - reflexarc. • One of the simplest – patellar reflex (helps maintain an upright position) • Involves only 2 neurons, sensory & motor (no interneuron)

  14. Parts of a Reflex Arc • Most reflexes include 5 structures: 1. receptor 2. 3. interneuron 4. motor neuron 5. • Other examples: withdrawal reflex (occurs when a person touches something painful) plantar reflex, Babinski reflex (abnormal in adults), biceps, triceps & ankle jerk reflexes

  15. Ventricles of Brain • Ventricles - Interconnected cavities in brain - 4 ventricles: 1st (left hemisphere) 2nd (rt. hemisphere) 3rd (midline of brain) 4th (in brainstem)

  16. Ventricles of Brain

  17. Pathway of CSF Circulation 1. Most CSF produced in lat. ventr. by choroid plexuses 2. Interventricular foramina – openings; allow CSF to flow from lat. to 3rd ventr. 3. 3rd ventricle • Cerebral aqueduct – • 5. 4th ventricle

  18. CSF Circulation • Flows into central canal & SA space of s.c. & back to subarachnoid space of brain 7. 8. Drain into blood-filled dural sinus into circ. sys. Humans secrete approx. 500ml of CSF daily. Only about 150 ml in CNS at any given time (continuously reabsorbed) CSF -

  19. Lumbar Puncture • Needle inserted into subarachnoid space of s.c. & CSF is withdrawn • Site is usually b/t L1-L2 or L3-L4 (a.k.a. spinal tap) • A manometer used to measure CSF pressure • CSF can be analyzed for viruses, bacteria, bleeding, tumors of the n.s., MS, & early-onset Alzheimers

  20. Normal vs. Hydrocephalic Brain ←Normal Normal Brain Hydrocephaly Normal intracranial Excessive accumulation pressure 7-15 mm Hgof CSF causes ventricles in brain to dilate; infant’s skull expands & incr. in circumference (bulging fontanels possible)

  21. Treatment of Hydrocephaly • Shunt placed in brain to regulate pressure & reabsorb CSF into subarachnoid space

  22. The Human Brain • 5 Major Areas: 1. Cerebrum 2. 3. Diencephalon 4. 5. Cerebellum

  23. Cerebrum • Largest part of brain • Consists of 2 halves (hemi- spheres) • Convolutions – • Sulci – • Fissures – 2 deep grooves 1. Longitudinal – divides brain into rt. & left halves

  24. Cerebrum • Transverse – separates cere- brum from cere- bellum • Cerebral cortex – • White matter – under gray; makes up most of the cerebrum

  25. Functions of Cerebrum • 3 basic functions: 1. Motor area – sends impulses to muscles 2. Sensory area – interpret impulses from sensory receptors 3. Association area –

  26. Lobes of the Brain • Sulci divide each cerebral hemisphere into 5 functional areas called lobes (named for skull bones). • 5th lobe - insula (not shown)

  27. Lobes of the Brain • Frontal • Association areas – • Motor areas – (ant. to central sulcus) – control of voluntary muscles • Broca’s area – ant. to motor cortex & in left hemi.; coordinates muscles of speech

  28. Lobes of the Brain 2. Parietal – • Somato- sensory area – cutaneous & other senses • Association area –

  29. Lobes of the Brain 3. Occipital – visual area 4. Temporal – • Wernicke’s area – in left temporal lobe; controls analysis of spoken language 5. Insula –

  30. Basal Ganglia • Also called basal nuclei • Consist of gray matter deep within the cere- bral hemispheres • Produce the ntm dopamine that inhibits motor functions (decr. levels assoc. w/Parkinson’s disease)

  31. Diencephalon • Includes 2 regions: • Thalamus – receives all sensory info & channels it to correct region on cerebral cortex for interpret- ation • Hypothalamus –

  32. Limbic System • This area controls emotions & is also assoc.w/memory

  33. Pineal & Pituitary Glands • Also located in diencephalon • Pineal gland – • Controls sleep & wake cycles • Pituitary gland –

  34. Brainstem • Connects brain to s.c. • Includes 3 regions: 1 2. 3.

  35. Midbrain • 1st, short section of brainstem • Relays info. from lower parts of b.s. & s.c. to higher brain • Contains corpora quadrigemina –

  36. Pons • Sends impulses to & from medulla & cerebellum

  37. Medulla Oblongata • Enlarged contin- uation of s.c. • All nerve tracts pass thru here & many cross over

  38. Medulla • Contains 3 centers: 1. Cardiac center – area that controls heart rate 2. Vasomotor center – 3. Respiratory center – • Nonvital centers – coughing, sneezing, swallowing, vomiting also located in medulla

  39. Reticular Formation • Nerve fibers scattered throughout the b.s. • When sensory impulses reach the r.f., it responds by activating the cerebral cortex into wakefulness • If the r.f. is destroyed, a person remains in a comatose state

  40. Reticular Formation • The r.f. filters incoming sensory info & decides what is important • Decreased activity in the r.f. results in sleep • Types of Sleep: 1. Slow-wave (non-REM)-

  41. Sleep • REM sleep (rapid eye movement) – “

  42. Cerebellum • Composed mostly of white matter • A treelike pattern is visible called the arbor vitae • Coordinates skeletal muscle activity