Central Nervous System

1. Central Nervous System Chapter 13

2. Basic parts of the CNS Brain Spinal Cord

3. Brain • Basic Parts : • Cerebrum • Cerebellum • Brain Stem • Cerebral Cortex Sulcus- valley (Fissures) • Gyrus- Mountains or raised areas

4. Sulcus and Fissures of the Brain

5. Cerebrum • Cerebral Cortex • Outer surface or covering of the cerebrum Gray Matter. Highest center of brain – where decisions are made. Only site of conscious awareness • Receives and interprets sensory input, if it doesn’t reach the cerebral cortex you won’t know what is going on. • Brain death- usually means the cortex has been wiped out • Amount of cortex correlates with the intellectual capacity, reptiles have very little compared to humans, rats do not have convuluted cortex

6. Cerebral cortex   Cerebral Cortex - thin layer of gray matter that is the outermost portion of cerebrum (the part with all the wrinkles)

7. Cerebrum cont… Central Sulcus – actually intersects the medial longitudinal fissure. Lobes of Brain Frontal lobe- intellectual power Temporal Lobe- Primarily hearing and speech Occipital Lobe- receive and interprets visual information Parietal lobe- Sensory reception and processing

8. Lateral fissures of the brain

11. Midsaggital view Inside the hemispheres of the brain Thalamus- every bit of sensory information going to cortex must go through the thalamus except olfactory sense 12 Cranial nerves on base of brain

12. Midsaggital brain

13. Hypothalamus • Hypothalamus- beneath Thalamus • Small but preforms many functions of greatest importance for survival and enjoyment • Links mind and body • Links nervous to endocrine • Regulates and coordinates autonomic behavior • Regulates appetite, arousal, body temperature,

15. Base of brain Putamen and GlobusPallidus- Make up the Lentiform nucleus which is the part of the basal ganglia responsible for voluntary motor movement. (Effected in Parkinsons) Internal Capsule- all information to and from the cortex pass through this capsule. Frequent site of stroke. Fibers out of thalamus pass through the internal capsule to the cortex. Sensory thru thalamus Motor fibers descend thru internal capsule and then to spinal cord for reaction.

17. 3 types of fibers in Cerebrum • Projection fibers- connect the cerebral cortex with the CNS • To cortex are sensory fibers • From cortex are motor fibers all thru the internal capsule • Fanning out of fibers from internal capsule to cortex are called Corona Radi • Association Fibers- connect two portions of the cortex in the same hemisphere. Ie. Frontal lobe to occipital lobe on the right.

18. Fiber types cont… • Commisural fibers- connect corresponding structures in different hemispheres. 3 sets: • Corpus callosum • Anterior commisures • Posterior commisures • Without connections the 2 hemispheres are not communicating.

21. Functional and Structural Areas of the Cerebral Cortex

22. Sensory Fiber Distribution

23. Cerebellum (add to your notes) • Connected to cerebrum by 3 peduncles • Dentate nucleus- influences motor cortex • Functions of cerebellum • Coordination of motor movement • Maintains balance • Controls posture

24. Brain Stem

25. Mid brain Controls visual and auditory reflexes Pineal body- prepare body for sleep or awake state- produces melatonin Cerebral Peduncles- carry motor fibers from cortex to spinal cord. Peduncles are the only thing connecting the cerebellum to the cortex. Medulla- descending motor fibers.

27. Coverings of the Brain and Spinal Cord • Outer Covering – Bone, skull and vertebrae • Inner Coverings- Meninges of the cord continue inside the spinal cavity beyond the end of the spinal cord. • Meninges- 3 membranous layers • DURA MATER- tough protection from outside. Connective tissue against bone. Doesn’t protect against trauma but separates the brain and spinal cord from outside world. Has 3 important extensions • FalxCerebri- between the two cerebral hemispheres. Contains dural sinuses that function as veins, collecting blood from brain tissues for return to heart. Also Superior saggital sinuses found in cerebrum.

28. Meninges cont… • FalxCerebelli- separates the two hemispheres of the cerebellum. • TentoriumCerebelli- between cerebrum and cerebellum • Arachnoid Mater- delicate cobwebby layer between the dura mater and pia mater • Pia Mater- Innermost transparent layer: adheres the outer surface of the brain and SC, forms a slender filament called the filumterminale, at level of the sacrum.

29. Meninges

30. Cerebrospinal Fluid • Functions: • Provide a supportive, protective cushion • Reservoir of circulating fluid, which is monitored by the brain to detect changes in the internal environment. • Fluid Spaces: • CSF-found within the subarachnoid space around the brain and spinal cord and within the cavities and canals of the brain and spinal cord • Ventricles- fluid filled spaces within the brain; four ventricles within the brain

32. CSF- Ventricles of the Brain

33. Issues with CSF • Hydrocephally- blockage of blood flow of CSF. No communicating, fluid goes in but releases and insignificant amount. • Intracranial pressure results between the dura and pia mater. Meningitis also causes this increase in pressure. Signs include: • Loss of consciousness • Pupils different sizes • Pass out • Headache • Treatment- drain CSF out of ventricle with a shunt to another part of body- usually stomach.

34. Spinal Cord • Structure of the spinal cord • Oval shaped • Anterior Median Fissure • Posterior median sulcus • Nerve roots laterally • Fibers of dorsal nerve root • Carry sensory information into SC • Dorsal Root ganglion- cell bodies are unipolar and make up gray matter in dorsal root • Fibers of Ventral Root • Cary motor information out of spinal cord • Cell bodies of multipolar, motor neurons are in the gray matter of SC

35. SC Anatomy Continued… Interneruons are located in the spinal cord’s gray matter core Spinal nerve- single mixed nerve on each side of the SC where the dorsal and ventral nerve roots join together.

36. Gray Matter Extends the length of the cord Consists Primarily of cell bodies of interneurons and motor neurons Looks like an H with the limbs being called anterior, posterior, and lateral horns of gray matter.

37. White matter Surrounds gray matter and is subdivided in each half on the cord into three funiculi: anterior posterior and lateral horns of gray matter Each funiculus consists of large bundle of axons divided into tracts Names of spinal tracts indicate the location of the tract, the structure in which the axons originate and the structure which they terminate.

39. Functions of the SC • Routes of conduction to the brain • Organized by structure and function • Ascending Tracts: • Lateral spinothalamic • Anterior spinothalmic • Fasciculus, gracilis and cuneateus • Spinocerebellar • spinotectal

40. Tracts continued • Descending tracts: • Lateral corticospinal tract • Anterior corticospinal tract • Reticulospinal tract • Rubrospinal tract • Tectospinal tract • Vestibulospinal tract

41. CONSCIOUSNESS State of awareness of one’s self, one’s environment, and other human beings (Figure 13-21) Depends on excitation of cortical neurons by impulses conducted to them by the reticular activating system Two current concepts about the reticular activating system Functions as arousal system for the cerebral cortex Functioning is crucial for maintaining consciousness

43. LANGUAGE Ability to speak and write words and understand spoken and written words Speech centers: areas in the frontal, parietal, and temporal lobes Left cerebral hemisphere contains speech centers in approximately 90% of the population; contained in either the right hemisphere or both in the remaining 10% Aphasias: lesions in speech centers

44. EMOTIONS Subjective experiencing and objective expressing of emotions involve functioning of the limbic system (Figure 13-22) Limbic system: also known as the emotional brain Most structures of limbic system lie on the medial surface of the cerebrum (cingulate gyrus and hippocampus) Have primary connections with other parts of the brain, such as the thalamus, fornix, septal nuclei, amygdaloid nucleus, and hypothalamus

46. MEMORY A major mental activity Cortex is capable of storing and retrieving both short- and long-term memory Temporal, parietal, and occipital lobes are among the areas responsible for short- and long-term memory Structural changes in the neural pathways of the cerebral cortex store long-term memories Limbic system plays a key role in memory