Biology 211 Anatomy & Physiology I The Brain

= = Central Brain Nervous Spinal cord System Nerves Peripheral Nervous

Human Central Nervous System Starts as a groove which becomes a hollow tube in the embryo; Remains hollow & fluid-filled throughout life; These fluid-filled spaces form the ventricles of the brain and the central canal of the spinal cord. Cranial end of this hollow tube enlarges & folds to form brain and its various parts Caudal end of this hollow tube does not enlarge or fold; Develops into spinal cord

Fifth week Fourth week

Prosencephalon Rhombencephalon From your reading in Saladin and from lab, you should understand what adult structures form from the myelencephalon, metenchephalon, mesencephalon, diencephalon, and telencephalon

More terms you need to know for brain and spinal cord Gray Matter: Nervous tissue of the CNS consisting of neuron cell bodies, their supporting glia, and unmyelinated axons & dendrites. White Matter: Nervous tissue of the CNS consisting of myelinated axons & dendrites and their supporting glia Cortex: On the surface of the brain (only on cerebrum and cerebellum) Nucleus: Deeper, surrounded by white matter

Coronal Section of Brain Cross Section of Spinal Cord

The brain has seven major (and many minor) regions: Cerebrum Thalamus Hypothalamus Midbrain Pons Medulla Oblongata Cerebellum Brainstem Let’s discuss each of these briefly.

Thalamus develops from diencephalon Most nuclei are “relay centers”: Receive sensory information from spinal cord, other regions of brain, eyes, ears, tongue, nasal epithelium. Relay that to sensory regions of cerebral cortex Some nuclei relay motor information from cerebral cortex to other regions of brain Some nuclei regulate sleep/wakefulness attention span

Hypothalamus develops from diencephalon Some nuclei regulate body temperature, blood pressure, hunger, thirst, fatigue. Some nuclei regulate endocrine (hormone) functions by controlling activity of pituitary gland (to which it is connected)

Midbrain develops from mesencephalon Often still called that. Some nuclei regulate eye movement & visual reflexes. Large tracts of white matter (myelinated axons) pass through, carrying motor information from cerebral motor cortex toward other parts of brain and spinal cord. Some nuclei modify that information to regulate motor functions. Large tracts of white matter pass through, carrying sensory information from spinal cord toward thalamus.

Pons develops from metencephalon Some nuclei relay signals between cerebrum and cerebellum. Some nuclei help regulate sleep, respiration, swallowing, taste, hearing, bladder control, equilibrium, eye movement, facial expressions, facial sensation, and posture. Motor information from cerebral cortex (white matter) passes through toward medulla oblongata and spinal cord; Sensory information continues from the medulla oblongata and spinal cord toward the thalamus and toward the cerebellum.

Cerebellum develops from metencephalon Gray matter = cortex and nuclei Receives motor information from all parts of the brain, including the cerebrum, and Receives sensory information from spinal cord and other parts of the brain. Uses that information to coordinate and fine-tune movement, particularly timing and precision.

Medulla Oblongata develops from myelencephalon Some nuclei help regulate respiration, heart rate, blood pressure, blood distribution. Other nuclei regulate vomiting, swallowing, coughing, sneezing, movement of tongue White matter carries motor information from other regions of brain to spinal cord, and sensory information from spinal cord to other regions of brain.

Cerebrum Arises from the telencephalon Consists of right and left hemispheres separated by each other by the longitudinal fissure Each hemisphere is hollow, containing a lateral ventricle which is lined by ependyma and filled with cerebrospinal fluid

Each hemisphere includes both white matter and gray matter: Cerebrum Each hemisphere includes both white matter and gray matter: Cortex Basal Nuclei Coronal Section

Cerebral Cortex Gray Matter 2 - 4 mm thick Folded into ridges, or gyri (singular: gyrus) separated by shallow grooves, or sulci (singular = sulcus) Different parts of brain separated by deep fissures

Lobes of Cerebral Cortex

Cerebral Cortex Each gyrus, sulcus, and fissure has a name (more than 50 gyri & sulci)

Cerebral Cortex Each gyrus, sulcus, and fissure has a name You don't need to know all of them You will need to know the following: Longitudinal Fissure Central Sulcus Precentral Gyrus Postcentral Gyrus Lateral Fissure/Sulcus Parietooccipital Sulcus

Different regions of the cortex have specific functions Cerebral Cortex Different regions of the cortex have specific functions Three types of functional areas: Motor Sensory Association More about these in a moment – they form more than 75% of the cerebral cortex

Cerebral Cortex Different regions of the cortex have specific functions From your reading and lab exercises, you should know the functions of the following areas and where they are located: Primary motor area Motor association area Primary somatosensory area Somatosensory association area Primary visual area Visual association cortex Primary auditory area Auditory association area Questions on these may be on lecture and/or lab exams

The “association” regions of the cerebral cortex also carry out the highly complex functions we associate with the brain. Just a few examples:

Cerebral Cortex Two regions of cortex important in language: Broca's Area deals with formation of speech Wernicke's Area deals with recognition and interpretation of speech Both located primarily on just one hemisphere (usually the left). Similar regions on other hemisphere control emotional content of speech.

Gray matter forms both: Cerebrum Recall:: Gray matter forms both: Cortex Basal Nuclei Coronal Section

Basal or Deep or Cerebral Nuclei Caudate Putamen Globus Pallidus Claustrum Amygdala Not shown: Amygdala

Areas of the brain active in Parkinson’s Disease Areas of the brain active in Huntington’s Disease

Keep in mind: All regions of the brain must work together, so there are many ways in which they communicate with each other. Three examples (of many) of association area functions: The Reticular Formation The Limbic System Cerebellar Function

Many nuclei in the brainstem (midbrain, pons, medulla oblongata) are interconnected to form the reticular formation. It helps integrate sensory information from the spinal cord, eyes, ears, etc. with the motor information coming from the cerebrum, cerebellum, and other parts of the brain. Thus, it plays a major role in coordinating all of the different parts of the nervous system. It also plays a major role in coordinating the sleep/wake cycle and in habituation to frequent stimuli.

Different parts of the cerebrum (telencephalon) and the thalamus and hypothalamus (diencephalon) communicate with each other on the medial surface of each cerebral hemisphere to form the limbic system. These coordinate emotions, motivation, memory, and other functions important to survival of the individual (e.g. fear, anger, excitation, pleasure) or to survival of the species (sexual responses.) The limbic system is closely linked to the sense of smell.

The cerebellum receives large amounts of motor information from the cerebral cortex, basal nuclei, and various parts of the brainstem. It also receives large amounts of sensory information coming from the spinal cord and brainstem. It integrates this sensory input with the motor information to maintain balance and equilibrium and to coordinate both the timing and the intensity of voluntary movements

From your reading and lab exercises, you should also know the locations of the - Lateral ventricles - Interventricular foramen - Third ventricle - Fourth ventricle - Mesencephalic aquaduct - Median aperture - Lateral apertures Questions on these may be on lecture and/or lab exams

Brain is surrounded by three layers of connective tissue: (Skull) Epidural Space Subdural Space Subarachnoid Space Dura Mater Arachnoid Mater Pia Mater

The brain is protected in three ways: 1) Skull 2) Meninges Pia Mater Arachnoid Mater Dura Mater 3) Floats in cerebrospinal fluid in subarachnoid space

Cerebrospinal fluid produced within ventricles by specialized tissue called choroid plexus. Flows toward fourth ventricle Exits from fourth ventricle through three openings (apertures or foramina) into the subarachnoid space. Median Aperture Two Lateral Apertures Surrounds brain & spinal cord. Reabsorbed into blood through arachnoid villi on surface of brain