The Brain

The Brain ~35 billion neurons Adult brain contains almost 98% of neural tissue in the body Weighs about 1.4 kg (3lbs) Volume of 1200 cc (71 in3) No correlation between brain size and intelligence

Three Main Structures 1. Cerebrum 2. Cerebellum 3. Brain Stem

The Cerebrum Conscious thought and intellectual function originate B. Outer Surface composed of: a. Gyri- elevated ridges (increase surface area) b. Sulci- shallow depressions c. Fissures- deep grooves C. Two Cerebral Hemispheres covered by a cerebral cortex 1. Right Hemisphere 2. Left Hemisphere ~Hemispheres are united by a corpus callosum - major route of communication between the hemispheres.

The Cerebrum

Hemisphere Control Right Side judging the position of things in space knowing body position understanding and remembering things we do and see putting bits of information together to make an entire picture controls the left side of the body Left Side understanding and use of language (listening, reading, speaking and writing) memory for spoken and written messages detailed analysis of information controls the right side of the body

LEFT BRAIN DAMAGE Problems seen on the right side of the body. RIGHT BRAIN DAMAGE Problems seen on the left side of the body.                                                                                                                                                                                      

Cerebral Hemispheres Separated by a deep longitudinal fissure (central sulcus extends laterally) Divided into lobes named for bones of the skull: Frontal Lobe Temporal Lobe Parietal Lobe Occipital Lobe

Frontal Lobe Primary Motor Cortex: - voluntary motor function problem solving Spontaneity Memory Language Judgment impulse control Personality Vulnerable to injury

Parietal Lobe Primary Sensory Cortex: - sensory somatic information Location for visual attention. Location for touch perception. Goal directed voluntary movements. Manipulation of objects. Integration of different senses that allows for understanding a single concept.

Temporal Lobe Hearing ability Memory acquisition Some visual perceptions Categorization of objects Auditory Cortex- hearing Olfactory Cortex- smelling

Occipital Lobe Visual Cortex - Vision ~not particularly vulnerable to injury because of their location at the back of the brain ~although any significant trauma to the brain could produce subtle changes to our visual-perceptual system

The Limbic System Contains several cerebral nuclei, gyri, and tracts that border the cerebrum and the diencephalon. Contains cerebral centers concerned with: 1. sense of smell 2. long-term memory storage- Hippocampus 3. emotional states (flight and fight)- Amygdaloid 4. control of reflex movements that can be consciously activated

Diencephalon (Forebrain) Central Core of the forebrain Switching and relay centers that integrate the conscious and unconscious sensory and motor pathways. Composed of the: 1. Thalamus 2. Hypothalamus 3. Epithalamus

Thalamus Constitutes the top of the brain stem Paired egg shaped masses Afferent impulses from all senses converge and synapse in the thalamus Impulses are sorted out, edited, and relayed as a group Coordination of voluntary and involuntary motor commands Plays an important role in mediating sensation, motor activities, learning and memory.

Hypothalamus Located between the thalamus Contains centers associated with emotions of rage, pleasure, pain, thirst, hunger, and sexual arousal 1. Adjusts and coordinates the activities of autonomic centers in the pons and medula oblongata 2. Coordinates neural and endocrine activities 3. Produces a variety of hormones including antidiuretic hormone (ADH) and oxytocin 4. Coordinates voluntary and autonomic functions 5. Maintains normal body temperature 6. Regulates sleep, sleep cycle, hunger, blood pressure, heart rate, breathing depth

Epithalamus Pineal gland: extends from the posterior border and secretes melatonin- involved in sleep regulation, and mood Choroid plexus- structure that secretes CSF (cerebrospinal fluid)

Midbrain Located between the diencephalon and the pons Midbrain structures include: 1. various nuclei and buncles of ascending and descending nerve fibers. 2. control involuntary motor reflexes to sudden visual and auditory stimuli (loud noise, bright light) Reticular Formation- network of interconnected nuclei that extend the length of the brain stem. - regulation of involuntary functions -maintains position and posture

Pons (Hindbrain) Bulging brainstem region between the midbrain and the medulla oblongata Fibers of the pons: Connect higher brain centers and the spinal cord Relay impulses between the motor cortex and the cerebellum

Medulla Oblongata Most inferior part of the brain stem Physically connects the brain with the spinal cord Cardiovascular control center- adjusts force and rate of heart contraction. Respiratory centers- control rate and depth of breathing

Cerebellum Makes rapid adjustments to muscle tone and position to maintain balance and equilibrium Programs and fine-tunes voluntary and involuntary movements Plays a role in language and problem solving Recognizes and predicts sequences of events Maybe permanently damaged by stroke or temporarily affected by alcohol

Gray Matter Adjusts the postural muscles of the body: Coordinates rapid automatic adjustments to maintain balance and equilibrium Programs and “fine-tunes” voluntary and involuntary movements - refines learned movements patterns

White Matter Arbor Vitae- (tree of life) which links Cerebellar cortex (gray matter) to the- 1. Cerebellar Peduncles- which link the cerebellum to the mesencephalon diencephalon cerebrum Transverse fibers Like the commissural fibers in the cerebrum - link the cerebellar hemispheres and extend into the pons and medulla oblongata.