The Brain: Structure, Function, and Development

1. The Brain Ale Robles MinJeong Cho Joseline Dubon

2. Function • The brain is responsible for integrating most sensory information and coordinating body functions. The brain includes: • Two cerebral hemispheres • Diencephalon • Brain stem • Cerebellum

3. Development • Basic structure of the brain begins as the neural tube that gives rise to the CNS. The Portion that becomes the brain has three cavities: • Forebrain (prosencephalon) • Midbrain (mesencephalon) • Hindbrain (rhombencephalon)

4. Cont... • The forebrain divides into the telencephalon and diencephalon. • The hindbrain divides into the metencephalon and myelencephalon.

5. Meninges Three layers: Dura mater, arachnoid mater, and pia mater. • Dura mater-outermost layer. composed of tough, white, dense connective tissue. Contains many blood vessels and nerves. • Arachnoid mater- thin, web like membrane that lacks blood vessels and is located between the dura and pia matters. • Pia mater- thin and contains many nerves, and blood vessels that nourish the underlying cells of the brain and spinal cord.

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7. Spinal Cord • It is a slender column of nervous tissue that is continuous with the brain and extends downward through the vertebral canal. • Like the brain, the spinal cord is covered by the meninges and cushioned by cerebrospinal fluid.

8. Cont...

9. Cont... • The spinal cord is a center for spinal reflexes. • Nerve impulses follow nerve pathways. The simplest of these pathways, constitutes a reflex arc.

10. Reflex Behavior • They are automatic, subconscious responses to stimuli within the body. • Examples: Knee-jerk reflex, Withdrawal reflex • They both use two neurons- a sensory neuron communicating directly to a motor neuron.

11. Knee-jerk Reflex

12. Withdrawal Reflex

13. Different sections of the brain • Cerebrum • Develops from anterior portion of the forebrain. • Consists of two large cerebral hemispheres, which are mirror images. • Lobes of the hemispheres are named after the skull bones they underline.

14. Cerebral hemisphere lobes Frontal lobe- forms anterior portion of each cerebral hemisphere. Parietal lobe- Posterior to the frontal lobe and is separated from it by the central sulcus. Temporal lobe- Lies inferior to the frontal and parietal lobes and is separated by the lateral sulcus. Occipital lobe- Forms the posterior portion of each cerebral hemisphere. Insula- Located deep within the lateral sulcus. It is covered by parts of the frontal, parietal, and temporal lobes.

15. Cont... Involved in several functions of the body including: • Determining Intelligence • Determining Personality • Thinking • Perceiving • Producing and Understanding Language • Interpretation of Sensory Impulses • Motor Function • Planning and Organization • Touch Sensation

16. Hemisphere Dominance • One hemisphere of the brain is dominant for a certain function. • Nerve fibers enable dominant hemisphere to control motor cortex of the nondominant hemisphere. • MEMORY: located in the temporal lobe, specifically in the hippocampus. • short term • long term

17. Basal Nuclei • Masses of grey matter deep in cerebral hemisphere. • 3 parts: • Caudate nucleus • Putamen • Globus pallidus • Produces dopamine.

18. Diencephalon • Develops from posterior forebrain, made up of the hypothalamus and thalamus. • Links the phylogenetically older brainstem to various structures in the phylogenetically newer telencephalon.

19. Diencephalon cont. • Optic tracts, optic chiasma, infundibulum, posterior pituitary gland, mammillary bodies, and pineal gland.

20. Limbic System • Portions of cerebral cortex in the medial parts of the frontal and temporal lobes that connect with deep nuclei from the limbic system. • Controls emotional experience and expression, by modifying how someone acts (anger, fear, pleasure) • Fight or Flight • Can interpret sensory impulses

21. Brainstem • Connects brain to spinal cord. • Made up of: • Midbrain: controls visual and auditory systems • Pons: contains nuclei that relay signals from forebrain to the cerebellum. • Medulla Oblongata: nerve fibers that control visceral activity pass through.

22. Cerebellum • Large mass of tissue located inferior to the occipital lobes of the cerebrum. • Primarily composed of white matter with a thin layer of gray matter (cerebellar cortex). • Communicates with other parts of the CNS by means of three pairs of nerve tracts called cerebellar peduncles.

23. Cranial Nerves • 12 pairs • Except for first two pairs, • originated from brainstem. • 12 pairs are named and • numbered in Roman • Numerals (I - XII)

24. I - IV • Olfactory Nerves (I) • Sense of smell • Only sensory neurons • Located upper nasal cavity • Optic Nerves (II) • Vision • Sensory neurons • Lead from eyes • Oculomotor Nerves (III) • Part 1 • Movement of eyes, four of six muscles that move eyes. • From mid brain, pass into orbots of the eyes • Trochlear Nerves (IV) • Carry motor impulses • Motor neurons • From mid brain to a fifth pair of external eye muscles

25. V - VIII • Trigeminal Nerves (V) • Mixed; sensory and motor neurons • From the pons to different parts of face • Ophthalmic • Maxillary • Mandibular • Absucens Nerves (VI) • Supply motor impulses • Motor neurons • Originated from pons, enter the orbits of eye. • Facial Nerves (VII) • Taste receptors on tongue and transmit impulses to muscles of face • Mixed; sensory and motor neurons • From floor plans two side of the face • Vestibulocochlear Nerves (VIII) • Sensory Neurons • Originatedd from medulla oblongata

26. IX - XII • Glossopharyngeal Nerves (IX) • Associated with tongue and pharynx • Mixed; sensory and motor neurons • Arise from medulla oblongata • Vagus Nerves (X) • Carries impulses • Mixed neurons • Originated in medulla oblongata, extend downward through neck into chest and abdomen • Accessory Nerves (XI) • Carries impulses to muscles of soft palate, pharynx and larynx • Motor neurons • From medulla oblongata and spinal cord • Hypoglossal Nerves (XII) • Carry impulses to muscles to move tongue • Motor neurons • From medulla oblongata and pass into tongue

27. Overview

28. Spinal Nerves • grouped by the level from which they arise number in sequence • 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, 1 pair of coccygeal nerves. • Each spinal nerves consist of... • Dorsal root • Ventral root

29. Spinal Nerves Cont. • Each spinal nerves has a dorsal and ventral branches • Dorsal: turns posteriorly • Ventral: continues forward • The thoracic and lumbar spinal nerves also have a the visceral branch • Visceral: part of autonomic nervous system

30. Spinal Nerves Cont. • Autonomic nervous system: • Preganglionic fiber • Postganglionic fiber • Sympathetic • Ganglionic fibers originate from neurons • found in upper two lumbar segments of the cord • Sympathetic chain ganglia and sympathetic trunks • Whute and Gray rami • gray rami communicantes to ALL spinal nerves; result in autonomic sympathetic fibers being incorporated • white rami communicantes carry presynaptic sympathetic fibers

31. Works Cited http://www.healthline.com/human-body-maps/brain http://psychology.about.com/od/biopsychology/ss/brainstructure_4.htm http://brainmadesimple.com/pons.html