The Brain Muse Spring2430 Lecture #10 7/16/12
An Introduction to the Brain and Cranial Nerves The Adult Human Brain Ranges from 750 cc to 2100 cc Contains almost 97% of the body’s neural tissue Average weight about 1.4 kg (3 lb)
The Brain Six Regions of the Brain Cerebrum Cerebellum Diencephalon Mesencephalon Pons Medulla oblongata
The Brain Figure 14–1 An Introduction to Brain Structures and Functions.
Anterior Longitudinal fissure Frontal lobe Cerebral veins and arteries covered by arachnoid mater Parietal lobe Right cerebral hemisphere Left cerebral hemisphere Occipital lobe Posterior (c) Figure 12.6c
The Brain Figure 14–2 Ventricles of the Brain.
Brain Protection and Support Cerebrospinal Fluid (CSF) Surrounds all exposed surfaces of CNS Interchanges with interstitial fluid of brain Functions of CSF Cushions delicate neural structures Supports brain Transports nutrients, chemical messengers, and waste products
Brain Protection and Support Figure 14–4 The Formation and Circulation of Cerebrospinal Fluid.
Ependymal cells Capillary Section of choroid plexus Connective tissue of pia mater Wastes and unnecessary solutes absorbed CSF forms as a filtrate containing glucose, oxygen, vitamins, and ions (Na+, Cl–, Mg2+, etc.) Cavity of ventricle (b) CSF formation by choroid plexuses Figure 12.26b
Brain Protection and Support Blood Supply to the Brain Supplies nutrients and oxygen to brain Delivered by internal carotidarteries and vertebral arteries Removed from dural sinuses by internal jugular veins
Brain Protection and Support Figure 21–23 Arteries of the Brain.
Brain Protection and Support Blood–Brain Barrier Isolates CNS neural tissue from general circulation Formed by network of tight junctions Between endothelial cells of CNS capillaries Lipid-soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord Astrocytes control blood–brain barrier by releasing chemicals that control permeability of endothelium
Capillary Neuron Astrocyte (a) Astrocytes are the most abundantCNS neuroglia. Figure 11.3a
Brain Protection and Support Four Breaks in the BBB Portions of hypothalamus Secrete hypothalamic hormones Posterior lobe of pituitary gland Secretes hormones ADH and oxytocin Pineal glands Pineal secretions Choroid plexus Where special ependymal cells maintain blood–CSF barrier
The Medulla Oblongata The Medulla Oblongata Allows brain and spinal cord to communicate Coordinates complex autonomic reflexes Controls visceral functions Nuclei in the Medulla Autonomic nuclei: control visceral activities Sensory and motor nuclei: of cranial nerves Relay stations: along sensory and motor pathways
The Medulla Oblongata Figure 14–5a The Diencephalon and Brain Stem.
Fourth ventricle Solitary nucleus Choroid plexus Hypoglossal nucleus (XII) Dorsal motor nucleus of vagus (X) Vestibular nuclear complex (VIII) Inferior cerebellar peduncle Cochlear nuclei (VIII) Lateral nuclear group Nucleus ambiguus Medial nuclear group Reticular formation Inferior olivary nucleus Raphe nucleus Pyramid Medial lemniscus (c) Medulla oblongata Figure 12.16c
The Cerebellum Functions of the Cerebellum Adjusts postural muscles Fine-tunes conscious and subconscious movements
The Cerebellum Structures of the Cerebellum Purkinje cells Large, branched cells Found in cerebellar cortex Receive input from up to 200,000 synapses Arbor vitae Highly branched, internal white matter of cerebellum Cerebellar nuclei: embedded in arbor vitae: relay information to Purkinje cells
The Cerebellum Figure 14–7b The Cerebellum.
Anterior lobe Posterior lobe Vermis (d) (d) Figure 12.17d
The Cerebellum Disorders of the Cerebellum Ataxia Damage from trauma or stroke Intoxication (temporary impairment) Disturbs muscle coordination
The Diencephalon Integrates sensory information and motor commands Thalamus, epithalamus, and hypothalamus The pineal gland Found in posterior epithalamus Secretes hormone melatonin
The Diencephalon The Hypothalamus Mamillary bodies Process olfactory and other sensory information Control reflex eating movements Infundibulum A narrow stalk Connects hypothalamus to pituitary gland Tuberal area Located between the infundibulum and mamillary bodies Helps control pituitary gland function
The Diencephalon Figure 14–10a The Hypothalamus in Sagittal Section.
The Diencephalon Eight Functions of the Hypothalamus Provides subconscious control of skeletal muscle Controls autonomic function Coordinates activities of nervous and endocrine systems Secretes hormones Antidiuretic hormone (ADH) by supraoptic nucleus Oxytocin (OT; OXT) by paraventricular nucleus
The Diencephalon Eight Functions of the Hypothalamus Produces emotions and behavioral drives The feeding center (hunger) The thirst center (thirst) Coordinates voluntary and autonomic functions Regulates body temperature Preoptic area of hypothalamus Controls circadian rhythms (day–night cycles) Suprachiasmatic nucleus
The Limbic System The Limbic System Is a functional grouping that Establishes emotional states Links conscious functions of cerebral cortex with autonomic functions of brain stem Facilitates memory storage and retrieval
The Limbic System Figure 14–11a The Limbic System.
The Limbic System Components of the Limbic System Amygdaloid body Acts as interface between the limbic system, the cerebrum, and various sensory systems Limbic lobe of cerebral hemisphere Cingulate gyrus Dentate gyrus Parahippocampal gyrus Hippocampus
The Limbic System Components of the Limbic System Fornix Tract of white matter Connects hippocampus with hypothalamus Anterior nucleus of the thalamus Relays information from mamillary body to cingulate gyrus Reticular formation Stimulation or inhibition affects emotions (rage, fear, pain, sexual arousal, pleasure)
The Limbic System Figure 14–11b The Limbic System.
Fiber tracts connecting limbic system structures Septum pellucidum Diencephalic structures of the limbic system Corpus callosum •Fornix •Anterior thalamic nuclei (flanking 3rd ventricle) •Anterior commissure Cerebral struc- tures of the limbic system •Hypothalamus •Mammillary body •Cingulate gyrus •Septal nuclei •Amygdala •Hippocampus •Dentate gyrus •Parahippocampal gyrus Olfactory bulb Figure 12.18
Limbic System Emotional or affective brain Amygdala—recognizes angry or fearful facial expressions, assesses danger, and elicits the fear response Cingulate gyrus—plays a role in expressing emotions via gestures, and resolves mental conflict Puts emotional responses to odors Example: skunks smell bad
Limbic System: Emotion and Cognition The limbic system interacts with the prefrontal lobes, therefore: We can react emotionally to things we consciously understand to be happening We are consciously aware of emotional richness in our lives Hippocampus and amygdala—play a role in memory
The Cerebrum The Cerebrum Is the largest part of the brain Controls all conscious thoughts and intellectual functions Processes somatic sensory and motor information
The Cerebrum Gray matter In cerebral cortex and basal nuclei White matter Deep to basal cortex Around basal nuclei
The Cerebrum Figure 14–12c The Brain in Lateral View.
The Cerebrum Special Sensory Cortexes Visual cortex Information from sight receptors Auditory cortex Information from sound receptors Olfactory cortex Information from odor receptors Gustatory cortex Information from taste receptors
The Cerebrum Figure 14–15a Motor and Sensory Regions of the Cerebral Cortex.
The Cerebrum Figure 14–16 Hemispheric Lateralization.
The Cerebrum Monitoring Brain Activity Brain activity is assessed by an electroencephalogram (EEG) Electrodes are placed on the skull Patterns of electrical activity (brain waves) are printed out
The Cerebrum Four Categories of Brain Waves Alpha waves Found in healthy, awake adults at rest with eyes closed Beta waves 12-30 Hz Higher frequency Found in adults concentrating or mentally stressed Theta waves Found in children Found in intensely frustrated adults May indicate brain disorder in adults Delta waves 1-4 Hz During sleep Found in awake adults with brain damage
The Cerebrum Figure 14–17a-d Brain Waves.
Cerebral Cortex Thin (2–4 mm) superficial layer of gray matter 40% of the mass of the brain Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding Each hemisphere connects to contralateral side of the body There is lateralization of cortical function in the hemispheres
Functional Areas of the Cerebral Cortex The three types of functional areas are: Motor areas—control voluntary movement Sensory areas—conscious awareness of sensation Association areas—integrate diverse information Conscious behavior involves the entire cortex
Motor Areas Primary (somatic) motor cortex Premotor cortex Broca’s area Frontal eye field
Primary Motor Cortex Large pyramidal cells of the precentral gyri Long axons pyramidal (corticospinal) tracts Allows conscious control of precise, skilled, voluntary movements Motor homunculi: upside-down caricatures representing the motor innervation of body regions
Posterior Motor Anterior Motor map in precentral gyrus Toes Jaw Primary motor cortex (precentral gyrus) Tongue Swallowing Figure 12.9