The Central Nervous System

1. The Central Nervous System

2. The Brain • The Brain looks pinkish grey, is wrinkly like a walnut, and has the consistency of oatmeal. • It weighs on average 3.5 lbs for men and 3.2 pounds for women.

3. Embryonic Development • At three weeks old, the outer layer of the “brain” thickens and forms a line that runs down the center called a neural plate. • That plate invaginates to form a neural fold. (That big line that runs down the center of the brain).

4. The superior edges of the neural grooves fuse and drop forming a neural tube. This neural tube deepens and extends forming the caudal (tail) end of the brain forming what will later be defined as the spinal cord. As the Neural groove deepens…

5. In week five of development, the Primary vesicles of the brain give rise to secondary vesicles, which will later form the major regions of the brain.

6. Secondary structure Telencephalon  Diencephalon  Mesencephalon,  metencephalon, Myencephalon. Forms: Two cerebral hemispheres of brain Hypothalamus, thalamus, epithalamus, and retina of the eye Midbrain, pons and cerebellum, and medulla oblongata

8. Cerebral Hemispheres

9. Cerebral Hemispheres • The most superior part of the brain, makes up 83% of the brains body weight.

10. The elevated ridges of the cerebral hemispheres are called gyri. They are separated by grooves called sulci. • The deeper grooves are called fissures.

12. Regions of the brain • Lobes: • Frontal • Parietal • Occipital • Temporal • Cerebellum • Pons • Medulla oblongata • Brain stem • Olfactoral stem • Olfactoral tract • Hypocampus • hypothallumus

13. Gyri and sulci • Precentral gyrus • Postcentral gyrus • Central sulcus • Parieto-occipital sulcus • Gyri of insula (medial to temporal lobe)

14. Fissures • Longitudinal fissure • Transverse cerebral fissure

15. Thing to keep in “mind” about the cerebral cortex. • No one area of the cerebral cortex acts alone, and all conscious behavior involves every area of the cerebral cortex in some way.

16. The cerebral cortex • Contains three function areas, motor areas, sensory areas, and association areas. • Each hemisphere of the cerebral cortex is contralaterally concerned with the senses of the opposite side of the body.

17. The cerebral cortex: motor areas • Primary motor cortex: contains a type of nerve cell called pyramidal cells that allow us to consciously control precise voluntary movement. • These pyramidal cells serve for function of only one area. • For example, there are pyramidal cells that are specifically for foot movement, while there are other pyramidal cells that are designed for hand movement.

18. Stroke • Stroke is a very serious problem that develops when there is an interruption in the flow of blood to the brain. Also known as cerebrovascular accidents or "brain attacks." • There are two main types of strokes. • If a blood vessel is blocked by clots or other particles, it is called an ischemic stroke. • If a blood vessel breaks and bleeds, it is called a hemorrhagic stroke.

19. Signs of a stroke • Symptoms of stroke: • Sudden weakness or numbness in your face, body, arms or legs, especially if only one side is affected • Sudden loss of vision or problems seeing in one or both eyes • Sudden confusion, inability to speak or understand what others are saying • Sudden dizziness, instability or inability to stand, walk or coordinate movement • Sudden severe, unexplained headache

20. Commonality of stroke • Stroke is the third leading cause of death, after coronary heart disease and cancer. • Each year there are about 600,000 strokes in the US, and strokes kill over 150,000 Americans each year. • Over 15% of people who have had a stroke die within 30 days, and 15-30% of people who survive a stroke are permanently disabled.

21. Who’s at risk • Anyone can have a stroke but most people who have strokes are over the age of 55. Strokes affect both men and women. • African Americans tend to be at highest risk, but people of all races and ethnicities suffer from strokes.

22. How to prevent stroke • There are many things you can do to reduce your risk of stroke: • don't smoke • keep your blood pressure under control • stay physically active • if you have diabetes, treat it • eat a healthy diet that focuses on fruits, vegetables, and whole grains • maintain a healthy weight • keep your blood cholesterol under control • avoid illegal drug use

23. Who should be screened? • People of all ages should be periodically screened for risk factors of stroke: • diabetes • high blood pressure • poor blood cholesterol levels • overweight/obesity

24. motor areas continued • Premotor cortex- In the frontal lobe of the brain, just anterior of the precentral gyrus. Responsible for learned motor skills and repetitious and patterned nature.

25. motor areas continued • Broca’s area- inferior to the anterior region of the premotor area. Present only on left side of the brain, directs muscles involved in speech production.

26. motor areas continued • Frontal eye field- superior to Broca’s area. Controls voluntary movements of the eyes.

27. Sensory areas allow for the conscious awareness of sensation. Mostly in the parietal temporal and occipital lobes. Sensory areas

28. Sensory areas continued • Primary somatosensory cortex- posterior to the postcentral gyrus. Receives information from skin, muscles and tendons when stimulus is applied. • It is not the size of the body part, but the number of sensors in that region that determines sensitivity. The face and fingertips are the most sensitive areas.

30. Sensory areas continued • Somatosensory association cortex- posterior to primary somatosensory cortex. Integrates sensory inputs like temperature, pressure, etc. from past experience to judge a stimulus without the use of another sense like sight.

31. Sensory areas continued • Visual area- extreme posterior of occipital lobe. It creates a contralateral map of visual space.

32. Auditory areas • Primary auditory cortex: located in superior portion of the temporal lobe. Involved in interpreting pitch, loudness, and sound. • Auditory association area: Posterior to the primary motor cortex. It interprets and perceives a sound stimulus.

33. Olfactory cortex: • Medial area of temporal lobe. Used to interpret impulses from smell receptors in the nasal cavity.

34. Gustatory cortex • Gustatory (taste) cortex: Located deep in the temporal lobe. It’s involved in the perception of tastes. • EWW That tastes disgusting!

35. Visceral Sensory areas • Just posterior to the gustatory complex, the visceral sensory area is responsible for the perception of visceral sensation. • (i.e. full bladder, upset stomach, feeling like your lungs will explode if you hold your breath too long.)

36. Vestibular cortex • Responsible for the conscious awareness of balance.

37. Multimodal association areas

38. Multimodal association areas • Multimodal association areas are responsible for collecting a large amount of information and processing it on multiple levels.

39. Multimodal association areas: prefrontal cortex • Encompasses most of the cerebrum. • Is involved in the process of memory formation, intellect, complex learning abilities, recall, and personality. • The ability of the prefrontal cortex varies greatly from the use of positive and negative feedback.

40. Multimodal association areas: Posterior association areas • Encompasses the parietal, temporal and occipital lobes. • Allows one to pay attention to the space around them, also plays a role in written and spoken language.

41. Multimodal association areas: Limbic association areas • Cingulate gyrus, parahippocampal gyrus, and the hippocampus. • Provides the emotional impact of a scene, which allows for the proper response to a stimulus.

42. Cerebral White Matter • Responsible for communication between hemispheres of the brain. • Commissures (made of commissural fibers) connect the grey areas of the hemispheres. The largest fissure is called the corpus callosum.

43. Cerebral White Matter continued • Association fibers- connects different parts of the same hemisphere. • Projection fibers- motor output from the cerebral cortex to the rest of the body. Projection fibers run vertically in the brain, while association fibers and commissure fibers run horizontally.

44. Basal Nuclei • Receives input from the entire cerebral cortex as well as from other subcortical nuclei and each other. • The true function of the Basal nuclei is unclear due to many parts of the cerebral cortex having overlapping functions.

45. Diencephalon • Contains the: • Thalamus • Hypothalamus • epithalamus.

46. Diencephalon: Thalamus • The thalamus contains a pair of egg shaped nuclei. The thalamus acts as the relay station for all information that enters the cerebral cortex.

47. Diencephalon: hypothalamus • Hypothalamus (below the thalamus) is the main visceral control center of the brain and is in charge of homeostasis in the body. • It is responsible for: • autonomic control • emotional response • body temperature regulation • Regulation of food intake • regulation of water balance and thirst • regulation of sleep/wake cycle • control of endocrine system functions

48. Diencephalon: epithalamus • Contains the pineal gland, which secretes melatonin. This is a major part of the sleep/wake cycle.

49. Brain stem • Contains the: • pons • midbrain • medulla oblongata

50. Brain stem: midbrain • b/w the diencephalon and the pons. Contains the: • corpora quadragemina: forms four bumps on the mid brain which themselves hold: • superior colliculi-visual reflex center • inferior colliculi-Allows for the reflex response to sound.