THE BRAIN Allied Health II

DIVIDED INTO 4 MAJOR PORTIONS

4 MAJOR PORTIONS Cerebrum – largest part  Nerve centers associated with sensory and motor functions  Higher mental functions: memory, reasoning Diencephalon – processes sensory information

4 MAJOR PORTIONS Brainstem – connects various parts of nervous system  Regulates certain visceral activities Cerebellum – Centers that coordinate voluntary muscle movement

STRUCTURE OF THE CEREBRUM 2 large masses – cerebral hemispheres Corpus callosum – bridge of nerve fibers that connect 2 hemispheres Convolutions (ridges) separated by grooves  Shallow groove – sulcus  Deep groove – fissure

STRUCTURE OF CEREBRUM Distinct patterns in all normal brains  Longitudinal fissure – separates right and left hemispheres  Transverse fissure – separates cerebrum from cerebellum Lobes of cerebral hemispheres are named from the bones they lie beneath

FRONTAL LOBE STRUCTURE Forms anterior portion of each cerebral hemisphere Bordered posteriorly by central sulcus Bordered inferiorly by lateral sulcus

PARIETAL LOBE Posterior to frontal lobe Separated by central sulcus

TEMPORAL LOBE Lies below frontal & parietal lobes Separated by lateral sulcus

OCCIPITAL LOBE Forms posterior portion of each cerebral hemisphere Separated from the cerebellum by shelf like extension of dura matter (tentorium cerebelli) Boundary between occipital lobe and parietal/temporal lobes is not distinct

INSULA Located deep within lateral sulcus Covered by parts of frontal, parietal and temporal lobes Circular sulcus separates insula from other lobes

CEREBRAL CORTEX Outermost portion of cerebrum Covers convolutions and dips into sulci and fissures Contains nearly 75% of all the neuron cell bodies in the nervous system

CEREBRAL CORTEX Beneath cortex is a mass of white matter – makes up bulk of cerebrum Contains bundles of myelinated axons that connect neuron cell bodies of the cortex with other parts of the nervous system Some fibers pass from one cerebral hemisphere to the other by way of the corpus callosum Some carry sensory or motor impulses from portions of the cortex to nerve centers in the brain or spinal cord

FUNCTIONS OF THE CEREBRUM Higher brain function Has centers from interpreting sensory impulses arriving from sense organs Centers for initiating voluntary muscular movement Stores information that comprises memory and reason Intelligence and personality

FUNCTIONAL REGIONS OF CEREBRAL CORTEX Divided into motor, sensory and association areas Motor areas of cerebral cortex lie in the frontal lobes just in front of the central sulcus Contains many large pyramidal cells that transmit impulses down through brainstem, into spinal cord, form synapses with lower motor neurons whose axons leave the spinal cord and reach skeletal muscle fibers

FUNCTIONAL REGIONS OF CEREBRAL CORTEX In addition to primary motor areas, certain other regions of the frontal lobe affect motor functions Broca’s area – motor speech area Anterior to the primary motor cortex and superior to the lateral sulcus Coordinates complex muscular actions of the mouth, tongue, and larynx that makes speech possible

FUNCTIONAL REGIONS OF CEREBRAL CORTEX Above Broca’s area is a region called the frontal eye field Motor cortex controls voluntary movements of eyes and eyelids

FUNCTIONAL REGIONS OF CEREBRAL CORTEX Sensory Areas – located in several lobes of cerebrum interpret impulses that arrive from sensory receptors, producing feelings or sensations  Touch – anterior portions of parietal lobes along central sulcus  Vision – Posterior parts of occipital lobes  Hearing – temporal lobes  Taste – near bases of the central sulci along the lateral sulci  Smell – centers deep within cerebrum

FUNCTIONAL REGIONS OF CEREBRAL CORTEX Association Areas – Analyze and interpret sensory experiences and oversee memory, reasoning, verbalizing, judgment and emotion Anterior portions of frontal lobes and are widespread in the lateral portions of the parietal, temporal and occipital lobes

FUNCTIONAL REGIONS OF CEREBRAL CORTEX Frontal lobes control: concentrating, planning, complex problem solving, and consequences Parietal lobes control: understanding speech, choosing words to express thoughts/feelings Temporal lobes control: complex sensory experiences like reading, remembering visual scenes and music

FUNCTIONAL REGIONS OF CEREBRAL CORTEX Occipital lobes control: analyzing visual patterns, combining visual images with sensory experiences General interpretative area – Parietal, temporal, and occipital association areas meet near the posterior end of the lateral sulcus  Plays primary role in complex thought processing

HEMISPHERE DOMINANCE Most people have one dominant hemisphere controlling the ability to understand language. In over 90% of people, left side is dominant for language, reading, writing, etc. Non-dominant hemisphere specializes in non-verbal functions like motor tasks that require orientation of the body in space, understanding musical patterns, non-verbal visual experiences

VENTRICLES AND CEREBROSPINAL FLUID Within the cerebral hemispheres and brainstem is a series of interconnected cavities called ventricles Contain cerebrospinal fluid Largest ventricles are the lateral ventricles (1 st and 2 nd ventricles) 3 rd ventricle – midline of brain, beneath corpus callosum 4 th ventricle – in the brainstem anterior to the cerebellum, has openings in its roof that lead to subarachnoid space of the meningies

VENTRICLES AND CEREBROSPINAL FLUID Choroid plexuses – tiny reddish, cauliflower-like masses of specialized capillaries from the pia matter. Secrete cerebrospinal fluid Cerebrospinal fluid completely surrounds the brain and spinal cord Acts as a shock absorber

DIENCEPHALON Located between cerebral hemispheres and above midbrain Surrounds 3 rd ventricle, composed mostly of gray matter Within the Diencephalon, a dense mass called the thalamus bulges into the 3 rd ventricle from each side Hypothalamus – lies below thalamus, forms lower walls & floor of 3 rd ventricle

THALAMUS Central relay station for sensory impulses ascending from other parts of the nervous system to the cerebral cortex Receives all sensory impulses and channels them to appropriate regions of the cortex for interpretation General awareness of pain, touch, temperature

HYPOTHALAMUS Maintains homeostasis by regulating a variety of visceral activities. Links nervous and endocrine systems Controls  Heart rate, arterial blood pressure  Body temp  H2O/electrolyte balance  Hunger/body weight  Movements and glandular secretions of stomach/intestines  Production of neurosensory substances that stimulate the pituitary gland to secrete hormones  Sleep and wakefullness

DIENCEPHALON Structures in the region of the diencephalon control emotional responses Limbic system – parts of cerebral cortex connect with thalamus and hypothalamus.  Controls emotional experience and expression  Can modify the way a person acts by producing fear, anger, pleasure, sorrow  Recognizes fear or upsets in a person’s physical or psychological condition that might threaten life  By causing pleasant or unpleasant feelings about experiences, the limbic system guides a person to a behavior that is likely to increase chances of survival

THE BRAINSTEM Bundle of nervous tissue that connects cerebrum to spinal cord Parts include  Midbrain  Pons  Medulla oblongata

MIDBRAIN Short section of brainstem between diencephalon and pons Contains bundles of myelinated axons that join lower parts of the brainstem/spinal cord with higher parts of the brain 2 prominent bundles of axons on the underside of the midbrain are the corticospinal tracts  The main motor pathways between cerebrum and lower parts of nervous system

MIDBRAIN Several masses of gray matter that act as reflex centers Certain visual reflexes – responsible for moving eyes to view something as the head turns Contains auditory reflex centers – enable you to turn your head to hear sounds more distinctly

PONS Rounded bulge on the underside of the brainstem Separates midbrain from medulla oblongata Dorsal portion – longitudinal nerve fibers  Relay impulses to the from the medulla oblongata and cerebrum Ventral portion – large bundles of transverse nerve fibers  Transmit nerve impulses from cerebrum to centers within cerebellum

PONS Several nuclei of the pons relay sensory impulses from peripheral nerves to higher brain centers Some nuclei function with centers on the medulla oblongata to regulate rate/depth of breathing

MEDULLA OBLONGATA Extends from Pons to opening of skull Top surface forms floor of 4 th ventricle Bottom surface is marked by corticospinal tracts All nerve fibers connecting the brain and spinal cord must pass through medulla

MEDULLA OBLONGATA Some nuclei in the medulla control visceral activities  Cardiac center – impulses beginning here are transmitted to the heart on peripheral nerves, altering HR  Vasomotor center – initiate impulses that travel to smooth muscles (blood vessels)  vasoconstriction, vasodilation  Respiratory center - acts with centers in the pons to regulate rate/depth of breathing  Also responsible from coughing, sneezing, swallowing, vomiting

RETICULAR FORMATION Complex network of nerve fibers found throughout medulla oblongata, pons and midbrain Responsible for wakefulness (activates cerebral cortex) Injury in reticular formation = comatose state

CEREBELLUM Large mass of tissue below occipital lobes of cerebrum Has 2 hemispheres separated by layer of dura matter Primarily white matter with thin layer of gray matter (cerebellar cortex) Communicates with central nervous system via nerve tracts (cerebellar peduncles)

CEREBELLUM Reflex center for sensory information regarding position of body parts and coordinating complex skeletal movements Maintain posture

CRANIAL NERVES Peripheral Nervous System  Somatic Located on the underside of brain, except for 1 st pair which begin in cerebrum 12 Pairs total

CRANIAL NERVES I – Olfactory II – Optic III – Oculomotor IV – Trochlear V – Trigeminal VI – Abducens VII - Facial VIII – Vestibulocochlear IX – Glossopharyngeal X – Vagus XI – Accessory XII - Hypoglossal

CRANIAL NERVES I – olfactory – smell II – optic – vision (acuity) III – Oculomotor – Move eyelids, control pupils IV – Trochlear – Eye movement V – Trigeminal – facial sensation, movement of jaw VI – Abducens – eye movement VII – Facial – facial expressions, taste

CRANIAL NERVES VIII – Vestibulocochlear – hearing/balance IX – Glossopharyngeal – Swallowing, salivary glands X – Vagus – Speech, swallowing, heart, smooth muscles, glands XI – Accessory – Soft palate, neck muscles Hypoglossal – Move the tongue

CRANIAL NERVES Oh Oh Oh To Touch And Feel Very Green Vegetables At Home Can be motor, sensory, or both Some Say Marry Money But My Brother Says Big Biceps Matter More

HOW TO REMEMBER & TEST CRANIAL NERVES seconds/ seconds/