F. Brain Structure & Functions

1. F. Brain Structure & Functions • Average adult brain weighs 3 lbs • Divided into 4 regions: • Cerebrum – largest region, broken into left & right hemispheres • Diencephalon – interbrain atop brain stem • Brain stem – stalk on which brain sits, connects to spinal cord • Cerebellum – bulbous projection at occipital region, broken into two hemispheres

2. 1. Cerebrum • Made of two hemispheres together called cerebrum • Encloses other three parts of brain • Entire surface made of peaks and valleys • Gyrus (gyri) – peaks of ridges • Sulcus (sulci) – shallow valleys • Fissures – deep grooves separating large regions

3. Function of cerebrum is vast • speech, memory, logical & emotional response, consciousness, interpretation of sensation, voluntary movement • Sulci & fissures divide cerebrum into lobes (named after cranial bones) • Parietal lobe • Frontal lobe • Temporal lobe • Occipital lobe

4. Parietal Lobe • Somatic sensory area located just posterior to central sulcus receives & interprets impulses from body’s sensory receptors (NOT special senses) • Pain, cold, light touch

5. Spatial map depicting region on body where senses come from and how much brain power is devoted to them is called sensory homunculus Model depiction showing areas of body given more brain “power” than others

6. Sensory pathways are crossed pathways, meaning left side of brain receives impulses from right side of body & vice versa • Itch on right hand interpreted on left side of somatic sensory area.

7. Occipital lobe • Visual area located in posterior part • Temporal lobe • Auditory area bordering lateral sulcus • Olfactory (smell) area deep inside

8. Frontal lobe • Contains primary motor area, just anterior to central sulcus, which allows us control of skeletal muscles • Spatial map region called motor homunculus • Broca’s area – located in left hemisphere gives ability to speak • Higher intellectual reason • Socially acceptable behavior • Language comprehension

9. Sensory & Motor Areas of Cerebral Hemisphere

11. Two layers of cerebral hemisphere: • Gray matter (cerebral cortex) • Outermost layer made out of cell bodies of neurons (no myelin) • Ridges allow greater surface area, increasing amount of neurons • Several islands of gray matter that jut inward called basal ganglia • White matter • Deeper cerebral layer made from fiber tracts (bundles of nerve fibers) • Major tract called corpus callosumconnects right & left cerebral hemisphere

13. 2. Diencephalon • AKA interbrain, made of 3 areas: • Thalamus – relay station for sensory impulses going up to sensory cortex • Get rough idea if sensation will be pleasant or unpleasant – sensory cortex figures it out • Hypothalamus – regulates body temperature, water balance (thirst), metabolism (appetite), sex, pain, pleasure, pituitary gland • Pituitary gland is attached & secretes hormones • Epithalamus – pineal gland(secretes hormones) & choroid plexus (knots of capillaries that form cerebrospinal fluid)

14. Diencephalon

15. 3. Brain Stem • Made of 3 structures: • Midbrain – reflex centers for vision & hearing • Pons – fiber tracts that control breathing • Medulla oblongata – control heart rate, blood pressure, breathing, swallowing, vomiting • Many small gray matter areas that control breathing, blood pressure • Running along length is reticular formation which regulates consciousness, awake/sleep cycles • Damage here results in permanent unconsciousness or coma

16. 4. Cerebellum • Two hemispheres & wrinkly (convoluted) surface • Outer cortex is gray matter while inner region is white matter called arbor vitae (tree of life) • Provides timing for muscle activity, controls balance & equilibrium • Constantly monitors body position & makes adjustments to keep balance

17. Brain Structure Recap