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Chapter 8 Part 1 – The Brain! Chapter 8, Part 1 - The Brain! CNS = central nervous system! • Brain and spinal cord (that’s all!)! PNS = peripheral nervous system! • All nerves, ganglia – i.e. all nervous structures not part of brain or spinal cord (CNS)! ! Afferent neurons= towards CNS! Efferent neurons = away from CNS! ! Neuron = the basic unit of nervous system! Glial cells = different types of these support neurons! Nervous System Organization 1 Figure 8.1! 2 1! Chapter 8 Part 1 – The Brain! Peripheral N.S.! Sensory (afferent) division:! • Sensory info towards CNS! Motor (efferent) division:! • Somatic NS! • Voluntary control of skeletal muscle! • Autonomic NS! • Involuntary (automatic) control of smooth muscle, cardiac muscle, glands! • Sympathetic division: “fight or flight”! • Parasympathetic division: “rest and digest”! 3 Grouping of Neural Tissue - 1! White matter Myelinated (and unmyelinated) nerve processes! • Schwann cells in PNS! • Oligodendrocytes in CNS! Gray matter Nerve cell bodies and dendrites! Unmyelinated axons! Neuroglia (e.g. astrocytes) Nerve Bundle of nerve fibers (typically axons) outside the CNS! Has associated CT layers! 4 2! Chapter 8 Part 1 – The Brain! Grouping of Neural Tissue - 2! Ganglion! Collection of nerve cell bodies outside of the CNS! e.g. Dorsal root ganglion! Nucleus! Collection of nerve cell bodies with a common function found inside the CNS! • In brain or spinal cord! • Unmyelinated (gray)! E.g. basal nuclei! 5 Introduction to the Organization of the Brain! Contains about 100 billion neurons and 1 trillion glial cells of different types! 6 3! Chapter 8 Part 1 – The Brain! Principal Parts - 1! 1. Brain stem! • Medulla! • Pons! • Midbrain (mesencephalon)! 2. Cerebellum! 3. Diencephalon! • Thalamus! • Hypothalamus (Connected to pituitary gland)! 7 Principal Parts - 2! 4. Cerebrum (cerebral cortex)! • Two cerebral hemispheres containing:! Frontal lobes! Parietal lobes! Temporal lobes! Occipital lobe! 8 4! Chapter 8 Part 1 – The Brain! The Adult Brain - Lateral View! Ridges = gyri (gyrus)! Grooves = sulci (sulcus)! 9 Brain Ventricles! right and left lateral ventricles 10 5! Chapter 8 Part 1 – The Brain! Ventricles! Fluid-filled chambers within the brain! Lined with ependymal cells (glial cells)! Filled with cerebrospinal fluid (CSF)! Produced by choroid plexuses in all ventricles! (Functions discussed later)! Continuous with subarachnoid space and central canal of the spinal cord! 11 Protection and Support for the Brain! 1. Cranial bones! 2. Cranial meninges! 3. Cerebrospinal fluid! 4. Blood-brain barrier! 12 6! Chapter 8 Part 1 – The Brain! Cranial Meninges! Continuous with spinal cord meninges! 1. ! Dura mater! • Forms dural folds which:! • Stabilize and support brain! • Contain dural (venous) sinuses! • Sinuses contain venous blood (and CSF returning to circulation)! 13 Arachnoid Membrane and Pia Mater! 2. Arachnoid (“spider-like”)! • Subarachnoid space! Contains CSF! 3. Pia mater (“soft”, “delicate”)! • Closely adheres to brain surface! • Follows sulci! Arachnoid! Pia mater! 14 7! Chapter 8 Part 1 – The Brain! Cerebrospinal Fluid (CSF) Functions! Formed by choroid plexuses! Functions:! • Cushions brain! • Supports brain (brain “floats” in CSF)! • Transports nutrients, wastes, chemicals! ! ☞ Note that there is a free exchange of fluids and solutes between CSF and extracellular fluids of the brain.! 15 Circulation of Cerebrospinal Fluid! CSF is found both within and around brain and spinal cord.! Write down the pathway that I give you.! 16 8! Chapter 8 Part 1 – The Brain! Blood Supply to Brain! Arterial supply:! Internal carotid and vertebral arteries! Venous return:! Dural sinuses → internal jugular (most)! ! Neurons rely on glucose - blood supply must be continuous.! ↑ Metabolism → ↑ CO2 → ↑ [H+] → ↑ vasodilation → ↑ blood flow! (remember: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-)! 17 Blood-brain Barrier! 1. Brain capillaries do not allow much leakage between their endothelial cells.! 2. Astrocytes (glial cells)! • Their “arms” cover capillaries! • Regulate capillary permeability (“leakiness”)! ! Together, these modifications allow some things to enter brain tissue while keeping other things out.! 18 9! Chapter 8 Part 1 – The Brain! The Medulla (Oblongata)! Medulla! 19 Medulla! 1. Ascending and descending tracts! 2. Autonomic nuclei - visceral control (part of reticular formation)! a. Cardiovascular centers! • Regulate heart rate, blood vessel diameter (effect blood pressure, right?)! b. Respiratory rhythmicity center! • Sets basic breathing rhythm! 20 10! Chapter 8 Part 1 – The Brain! The Pons (“bridge”)! Pons! 21 The Pons! 1. 2. 3. 4. Ascending, descending, transverse fiber tracts! Sensory and motor nuclei for cranial nerves! Respiration nuclei! Nuclei and tracts associated with cerebellum! • Process and relay info to/from cerebellum! 22 11! Chapter 8 Part 1 – The Brain! Cerebellum (“little brain”)! Cerebellum! 23 Cerebellum! Compares intended with actual movements and makes necessary adjustments! • Subconscious (automatic)! • Produces coordinated movements! • Regulates posture, muscle tone, balance! 24 12! Chapter 8 Part 1 – The Brain! The Midbrain! Tectum! Cerebral! peduncles! Midbrain! (mesencephalon)! Cerebral! aqueduct! 25 Midbrain! Contains:! 1. Cerebral peduncles! 2. Cerebral aqueduct! 3. Tectum (“roof”)! • Superior colliculus! • Inferior colliculus! 5. Cranial nerve nuclei! 26 13! Chapter 8 Part 1 – The Brain! Corpora Quadrigemina! Tectum (“roof” of aqueduct)! Corpora quadrigemina (part of tectum)! a. Superior colliculus! • Visual reflexes: eye tracking, reflexive head and neck movements! b. Inferior colliculus! • Auditory reflexes: reflexive head, neck, trunk movements! 27 Diencephalon! Thalamus! Hypothalamus! 28 14! Chapter 8 Part 1 – The Brain! Thalamus - “inner chamber”! The major sensory relay area! ! • Relays sensory inputs to proper part of cerebrum! ! Allows a crude appreciation of:! Pain, temperature, pressure! Sensation not localized to a particular area! 29 The Hypothalamus! Pineal! ! llosum ! x rni Fo Thalamus! us ca Corp Hypothalamus! Optic chiasm Infundibulum! (cut)! Mamillary body! 30 15! Chapter 8 Part 1 – The Brain! Hypothalamus Functions - 1! 1. Subconscious control of skeletal muscles associated with emotions! E.g. facial expressions of rage, pleasure, pain! E.g. body positions associated with sexual arousal! 2. Control of the autonomic nervous system! E.g. heart rate, BP, respiration! 3. Secretion of hormones! Oxytocin - remember this??! Antidiuretic hormone - remember this??! 31 Hypothalamus Functions - 2! 4. Controls release of anterior pituitary hormones with releasing hormones! 5. Influences emotions, behavioral drives! Feeding, fighting, pleasure, thirst! 6. Coordinates voluntary and autonomic functions! Think about stressful situation →! • ↑ HR, ↑ BP before stress begins! I.e. prepares body for stress! 32 16! Chapter 8 Part 1 – The Brain! Hypothalamus Functions - 3! 7. Body temperature regulation! Cold → vasoconstrict, shiver, etc.! Hot → vasodilate, sweat, etc.! 8. Circadian rhythms (daily sleep/wake patterns)! 33 Limbic System! “The emotional brain”! A network of many brain structures! Deals with primitive emotions! Functions:! 1. Establishes emotional states! 2. Links conscious, intellectual functions with unconscious, autonomic functions! 3. Important in memory! 34 17! Chapter 8 Part 1 – The Brain! The Cerebral Hemispheres! Central sulcus! PLAY! 35 Basal Nuclei! Gray matter deep to lateral ventricles! Functions:! Subconscious control of muscle tone! Coordination of learned movements! e.g. arm-swinging during walking! e.g. stabilizing shoulder joint while reaching! 36 18! Chapter 8 Part 1 – The Brain! Basal Nuclei - Parkinson’s Disease! Receive inhibitory (dopamine - DA) input from substantia nigra! Cerebrum + Thalamus + + Substantia nigra -- Basal nuclei muscle tone DA 37 Functions of the Frontal Lobe - 1! 1. Primary Motor Cortex on the Precentral gyrus! Movement of specific muscles or groups! Wilder Penfield’s experiments described the motor homunculus (“little man”)! The area of cortex innervating a body part is proportional to the number of motor units controlling that body part.! Motor unit = a motor neuron and all of the muscle cells that it innervates! 38 19! Chapter 8 Part 1 – The Brain! Primary Motor and Sensory Cortices! Motor homunculus! Frontal lobe! Sensory homunculus! Parietal lobe! 39 Functions of the Frontal Lobe - 2! 2. Premotor cortex! Stores a pattern for learned movements involving muscle groups! e.g. typing, playing the piano! ! Information pathway: ! prefrontal cortex → premotor cortex → primary motor cortex → muscles! 40 20! Chapter 8 Part 1 – The Brain! Functions of the Frontal Lobe - 3! 3. Prefrontal Cortex - an integrative area! • Integrates info from sensory areas → abstract thinking! Phineas P. Gage - 1848! Industrious, responsible, considerate! ! Damaged prefrontal cortex! Personality changed:! Quarrelsome, lazy, irresponsible! i.e. individuality, personality reside in the brain! Long-term planning, motivation! 41 Phineas P. Gage! 42 21! Chapter 8 Part 1 – The Brain! Functions of the Frontal Lobe - 4! 4. Motor Speech (Broca’s) Area! • Translates thought into speech! • Regulates breathing and vocalization for speech! • Damage → can make sounds, but not words! • On left side in 90% of population! 5. Frontal Eye Field Area! Voluntary scanning movements - e.g. reading! 43 Functions of Parietal Lobe - 1! 1. Primary Sensory Cortex! • On post-central gyrus! • General sensation info sent here from thalamus! Contains sensory homunculus! • Area of cortex involved proportional to number of receptors! ! Wilder Penfield’s experiments again! 44 22! Chapter 8 Part 1 – The Brain! Functions of Parietal Lobe - 2! 2. Sensory Association Area! E.g. knowing the shape and texture of an object when eyes are closed! E.g. light touch on arm is a mosquito, not a battleship! ! 3. Primary Gustatory Area! Taste! 45 Functions of Parietal Lobe - 3! 4. General Interpretive Area = Wernicke’s Area! • Receives input from all sensory association areas! • Forms a common thought based on inputs! e.g. integrates sensory info in context of auditory, visual memories! e.g. damage: can recognize object, but not name them! ! Usually only present on left side of brain! 46 23! Chapter 8 Part 1 – The Brain! Functions of Temporal Lobe - 1! 1. Primary Auditory Area! 2. Auditory Association Area! Determines music, speech, noise! Interprets:! Words into language! Words into thoughts! 3. Primary Olfactory Area! 47 Functions of Occipital Lobe! 1. Primary Visual Area! Input from retina! Shape, color, direction of movement! ! 2. Visual Association Area! Receives input from #1! Recognition of visual info! 48 24!
