Understanding the Human Brain: Functions and Components

1. Essentials of Human Anatomy Nervous System II

2. Brain • An adult brain weighs between 1.35 and 1.4 kilograms (kg) (around 3 pounds) and has a volume of about 1200 cubic centimeters (cc). • Brain size is not directly correlated with intelligence • It is not the physical size of the brain that determines intelligence—it is the number of active synapses.

3. Functions of the Brain • interprets sensations • determines perception • stores memory • reasoning • makes decisions • coordinates muscular movements • regulates visceral activities • determines personality 3

4. The Brain’s 4 Major Regions • Prosencephalon (forebrain) • Telencephalon: cerebrum • Diencephalon: epithalamus, thalamus,hypothalamus • Mesencephalon (midbrain) • Mesencephalon: cerebral peduncles, colliculi • Rhombencephalon (hindbrain) • Metencephalon: pons, cerebellum • Myelencephalon: medulla oblongata

5. The Brain’s 4 Major Regions • The cerebrum is divided into two halves, called the left and right cerebral hemispheres. • Each hemisphere is subdivided into four functional areas called lobes. • Outer surface of an adult brain exhibits folds called gyri (gyrus) and shallow depressions between those folds called sulci (sulcus). • The brain is associated with 12 pairs of cranial nerves.

8. Lobes of Cerebral Hemispheres • Frontal • Parietal • Temporal • Occipital • Insula 8

9. Functional Regions of Cerebral Cortex Cerebral Cortex – thin layer of gray matter that constitutes the outermost portion of cerebrum; contains 75% of all neurons in nervous system 9

12. Diencephalon • Between cerebral hemispheres and above the brainstem • Surrounds third ventricle 12

13. Diencephalon • Thalamus • gateway for sensory impulses heading to cerebral cortex • receives all sensory impulses (except smell) • channels impulses to appropriate part of cerebral cortex for interpretation • Hypothalamus • maintains homeostasis by regulating visceral activities • links nervous and endocrine systems 13

14. Diencephalon Limbic System • Consists of • portions of frontal lobe • portions of temporal lobe • hypothalamus • thalamus • basal nuclei • other deep nuclei • Functions • controls emotions • produces feelings • interprets sensory impulses 14

15. Brain Stem • Three Parts • Midbrain • Pons • Medulla Oblongata 15

16. Midbrain • between diencephalon and pons • contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain

17. Pons • rounded bulge on underside of brainstem • between medulla oblongata and midbrain • helps regulate rate and depth of breathing • relays nerve impulses to and from medulla oblongata and cerebellum 17

18. Medulla Oblongata • enlarged continuation of spinal cord • conducts ascending and descending impulses between brain and spinal cord • contains cardiac, vasomotor, and respiratory control centers • contains various nonvital reflex control centers (coughing, sneezing, swallowing, vomiting)

19. Cerebellum • inferior to occipital lobes • posterior to pons and medulla oblongata • two hemispheres • vermis connects hemispheres • cerebellar cortex – gray matter • arbor vitae – white matter • cerebellar peduncles – nerve fiber tracts • dentate nucleus – largest nucleus in cerebellum • integrates sensory information concerning position of body parts • coordinates skeletal muscle activity • maintains posture 19

22. Cranial Nerves 22

23. membranes surrounding CNS • protect CNS • three layers • dura mater – outer, tough • arachnoid mater – thin, weblike • pia mater – inner, very thin Meninges 23

24. 3) Pia mater 2) Arachnoid 1) Dura mater Spinal Meninges Three membranes surround all of CNS 1) Dura mater - "tough mother", strong 2) Arachnoid meninx - spidery looking, carries blood vessels, etc. Subarachnoid space 3) Pia mater - "delicate mother", adheres tightly to surface of spinal cord

25. Ventricles • interconnected cavities • within cerebral hemispheres and brain stem • continuous with central canal of spinal cord • filled with cerebrospinal fluid (CSF) • lateral ventricles • third ventricle • fourth ventricle • cerebral aqueduct 25

26. Cerebrospinal Fluid • secreted by choroid plexus • circulates in ventricles, central canal of spinal cord, and subarachnoid space • completely surrounds brain and spinal cord • clear liquid • nutritive and protective • helps maintain stable ion concentrations in CNS 26

27. Lumbar Puncture (= Spinal Tap) L3 L4 For clinical examination of CSF or administration of radiopaque dyes, drugs and sometimes anesthetics However: mostly “epidurals” for anesthetics

28. THE END