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Ch. 13 CNS

BRAIN Control center for thoughts, memories, and behaviors
SPINAL CORD The pathway for sensory nerve impulses traveling to the brain and motor nerve impulses traveling from the brain to skeletal muscles or other effectors ▪ Also controls some of the rapid reactions to environmental changes (reflexes)
BRAIN ▪ Cerebrum - left and right hemispheres ▪ Diencephalon - includes thalamus and hypothalamus ▪ Brain stem - includes midbrain, pons, and medulla oblongata ▪ Cerebellum - posterior segment
SPINAL CORD Extends inferiorly from brain stem to level of first or second lumbar vertebrae
PROTECTION OF CNS ▪ Skeletal ▪ Meninges ▪ Cerebrospinal fluid
MENINGES ▪ Dura mater ▪ Arachnoid mater ▪ Pia mater
DURA MATER ▪ Strongest, dense, irregular connective tissue ▪ Adheres to periosteum of cranial bones ▪ Three extensions separate portions of brain ▪ Double layer forms dural sinuses ▪ Separated from spinal cord by epidural space
ARACHNOID MATER ▪ Avascular web of delicate collagen and elastic fibers ▪ Separated from dura mater by subdural space
PIA MATER ▪ Transparent, adheres tightly to surface of brain and spinal cord ▪ Separated from arachnoid by subarachnoid space
SKELETAL -Skull - cranial bones form cavity - Vertebral column - vertebral foramina for canal
MENINGES ▪ Three protective, connective tissue layers ▪ Cranial and spinal meninges continuous with each other
CEREBROSPINAL FLUID - Fluid in space between meninges and inside cavities of brain and spinal cord - Buoyant, and shock-absorbing cushion
SPACES ASSOCIATED WITH MENINGES -dural sinuses -subdural space -epidural space -subarachnoid space
Dural sinuses brain only ▪ Blood from brain, delivers to internal jugular veins
Subdural space brain and spinal cord ▪ Interstitial fluid
Epidural space spinal cord only ▪ Fat and connective tissue ▪ Interstitial fluid
Subarachnoid space brain and spinal cord ▪ Cerebrospinal fluid ▪ Along spinal cord only: denticulate ligaments extend laterally from pia mater to fuse with arachnoid mater to protect from sudden displacement of spinal cord
Blood brings continuous supply of oxygen and glucose, and removes wastes and carbon dioxide
Blood flow to active areas of the brain increases during higher levels of metabolic activity
Interruptions in blood flow have very serious consequences (unconsciousness, stroke, death)
BLOOD FLOW TO BRAIN AND SPINAL CORD ▪ Brain -Internal carotid and vertebral arteries - Dural sinuses and internal jugular veins ▪ Spinal cord - Posterior intercostal and lumbar arteries and veins
BLOOD-BRAIN BARRIER (BBB) ▪ Created by tightly connected endothelial cells of CNS capillaries and astrocyte processes that press up against the capillaries ▪ Controls what can and cannot cross from blood into interstitial fluid of CNS tissues ▪ Glucose, oxygen, carbon dioxide, most anesthetics, alcohol, and some other substances can cross ▪ Toxins, most antibiotics, and proteins cannot cross ▪ Protects CNS from harmful substances and pathogens
BRAIN VENTRICLES Cerebrospinal fluid-filled cavities ▪ Two lateral ventricles (right and left) ▪ Third ventricle - midline, superior to hypothalamus ▪ Fourth ventricle - between brain stem and cerebellum
CEREBROSPINAL FLUID (CSF) Formed by choroid plexuses - capillary network in walls of ventricles
Functions of CSF ▪ Mechanical protection - buoyancy and shock-absorption ▪ Chemical protection - maintain optimal ionic concentrations of interstitial fluid ▪ Circulation of nutrients - efficient exchange
▪ Ependymal cells’ tight junctions form blood-cerebrospinal fluid barrier that controls passage of substances from blood into CSF
CEREBROSPINAL FLUID CIRCULATION Ependymal cell cilia move fluid between ventricles where formed ▪ Interventricular foramina - from lateral ventricles to third ventricle ▪ Cerebral aqueduct - from third to fourth ventricle ▪ Median aperture and pair of lateral apertures - from fourth ventricle to subarachnoid space ▪ Some enters central canal of spinal cord
CEREBROSPINAL FLUID CIRCULATION Arachnoid villi ▪ Eventually fluid flows to subarachnoid space around brain ▪ Fingerlike extensions project into dural sinus for reabsorption into blood
CEREBRUM: FUNCTION ▪ Interprets sensory impulses ▪ Controls muscular movements ▪ Functions in intellectual processes
CEREBRUM: SECTIONAL ANATOMY ▪ Cortex ▪ Internal (medulla) ▪ Basal nuclei
Cortex ▪ Outer rim of gray matter ▪ Gyri - folds of cortex ▪ Sulci - shallow grooves between gyri ▪ Fissures - deepest grooves, between major sections
Internal (medulla) ▪ White matter - tracts of myelinated axons ▪ Propagate impulses for communication within CNS
Basal nuclei ▪ Functional clusters of gray matter (neuronal cell bodies) deep within white matter
CEREBRUM Lobes named for superficial cranial bone ▪ Frontal, parietal, temporal, and occipital ▪ Insula: deeper, within lateral fissure
CEREBRUM Fissures and sulci ▪ Longitudinal fissure - between hemispheres ▪ Central sulcus - between frontal and parietal lobes ▪ Separates major gyri: precentral and postcentral gyrus ▪ Lateral sulcus - between frontal and temporal lobes ▪ Parieto-occipital sulcus - between parietal and occipital lobe
CEREBRUM: WHITE MATTER TRACTS ▪ Association tracts ▪ Commissural tracts ▪ Projection tracts
ASSOCIATION TRACTS Conduct impulses between gyri of the same hemisphere
COMMISSURAL TRACTS ▪ Conduct impulses between gyri of different hemispheres ▪ Corpus callosum - largest fiber bundle in brain ▪ Anterior and posterior commissures
PROJECTION TRACTS ▪ Conduct impulses between cerebrum and lower CNS regions
CEREBRUM: BASAL NUCLEI Located deep in the cerebral white matter ▪ Globus pallidus ▪ Putamen ▪ Caudate nucleus
CEREBRUM: BASAL NUCLEI-FUNCTIONS ▪ Help initiate and terminate movements ▪ Regulate muscle tone ▪ Control subconscious contractions of skeletal muscles ▪ Influence some cognitive processes
CEREBRUM: CORTEX FUNCTIONAL AREAS ▪ Cortex ▪ Sensory areas ▪ Motor areas ▪ Association areas
CORTEX (gray matter with gyri/sulci) can be divided into specialized functional areas
SENSORY AREAS Allow perception (conscious awareness) of sensory information
MOTOR AREAS Control the execution of voluntary movements
ASSOCIATION AREAS Concerned with more complex integrative functions such as memory, personality traits, emotions, and intelligence
CEREBRAL CORTEX SENSORY AREAS ▪ Primary somatosensory area (postcentral gyrus) ▪ Primary visual area ▪ Primary auditory area ▪ Primary gustatory area ▪ Primary olfactory area
Primary somatosensory area (postcentral gyrus) Receives nerve impulses from somatic sensory receptors for touch, pressure, vibration, itch, tickle, temperature, pain, and proprioception and is involved in perception of these sensations
Primary visual area Receives and perceives visual information
Primary auditory area Receives and perceives sound information
Primary gustatory area Receives and perceives taste information
Primary olfactory area Receives and perceives smell information
CEREBRAL CORTEX MOTOR AREAS ▪ Primary motor area (precentral gyrus) ▪ Broca’s area
Primary motor area (precentral gyrus) ▪ Controls voluntary contractions of specific skeletal muscles or muscle groups on opposite side of body ▪ More cortical area devoted to muscles involved in skilled, complex, or delicate movement
Broca’s area ▪ Controls muscles of larynx, pharynx, and mouth for production of speech ▪ Coordinates control of muscles for breathing to regulate proper flow of air
CEREBRAL CORTEX ASSOCIATION AREAS ▪ Somatosensory association area ▪ Visual association area ▪ Auditory association area ▪ Wernicke’s area ▪ Common integrative area ▪ Prefrontal cortex ▪ Premotor area ▪ Frontal eye field area
Somatosensory association area ▪ Permits you to evaluate an object by touch and to sense the relationship of one body part to another; also stores memories of past somatic sensory experiences
Visual association area ▪ Utilizes past visual experiences for recognizing and evaluating what is seen
Auditory association area ▪ Allows you to recognize a particular sound
Wernicke’s area Interprets the meaning of speech by translating words into thoughts
Common integrative area ▪ Integrates sensory interpretations from the association areas, allowing thoughts based on sensory input
Prefrontal cortex ▪ Concerned with personality, intellect, complex learning abilities, judgment, reasoning, conscience, intuition, and development of abstract ideas
Premotor area ▪ Controls sequential muscle contractions, and serves as a memory bank for complex movements
Frontal eye field area ▪ Controls voluntary scanning movements of the eye
CEREBRUM: HEMISPHERIC LATERALIZATION ▪ Subtle anatomical differences between two hemispheres, although variable in individuals ▪ Each has unique functions, in a division of labor ▪ Each receives sensory signals from and controls movements on the opposite side of the body ▪ Left: more important for language, numerical and scientific skills, and reasoning ▪ Right: more important for musical and artistic awareness, spatial and pattern perception, recognition of faces, emotional content of language, identifying odors, and generating mental images of sight, sound, taste, and smell
FUNCTIONAL DIFFERENCES BETWEEN THE 2 CEREBRAL HEMISPHERES-LEFT HEMISPHERE FUNCTIONS -receives somatic sensory signals from and controls muscles on right side of body -reasoning -numerical and scientific skill -ability to use and understand sign language -spoken and written langauge
FUNCTIONAL DIFFERENCES BETWEEN THE 2 CEREBRAL HEMISPHERES-RIGHT HEMISPHERE FUNCTIONS -receives somatic sensory signals from and controls muscles on left side of body -musical and artistic awareness -space and pattern perception -recognition of faces and emotional content of facial expressions -generating emotional content of langauge -generating mental images to compare spacial relationships -identifying and discriminating among odors
DIENCEPHALON: FUNCTION ▪ Central core of brain tissue from brain stem to cerebrum, surrounding third ventricle ▪ Involved in variety of sensory and motor processing between higher and lower brain centers
DIENCEPHALON: SECTIONAL ANATOMY ▪ Thalamus ▪ Hypothalamus ▪ Pineal gland
Thalamus ▪ Paired oval masses of gray matter ▪ Intermediate mass connects right and left halves across third ventricle
Hypothalamus ▪ Many gray matter nuclei inferior to thalamus, including mammillary bodies ▪ Stalk-like infundibulum connects to pituitary gland
Pineal gland ▪ Pea-shaped protrusion posterior in midline of the third ventricle
DIENCEPHALON: THALAMUS ▪ Relays and processes sensory impulses to the primary sensory areas of the cerebral cortex ▪ Transmits input from the cerebellum to the primary motor area of the cerebral cortex ▪ Together with other brain areas, it functions in movement control, maintenance of consciousness, pain perception, memory, learning, and cognition
DIENCEPHALON: HYPOTHALAMUS ▪ One of the major regulators of homeostasis ▪ Control of autonomic nervous system (ANS) ▪ Production of hormones, especially related to pituitary gland ▪ Regulation of emotional and behavioral patterns ▪ Regulation of eating and drinking ▪ Control of body temperature ▪ Regulation of circadian rhythms and states of consciousness
DIENCEPHALON: PINEAL GLAND ▪ Secretes the hormone melatonin ▪ More during darkness than in light ▪ Promotes sleepiness ▪ Appears to contribute to setting the body’s biological clock
BRAIN STEM: FUNCTION ▪ Contain both tracts and nuclei ▪ Act as relay centers for processing and controlling involuntary reflexes for vision and hearing, and govern reflexes vital to life
BRAIN STEM: ANATOMY ▪ Midbrain ▪ Pons ▪ Medulla oblongata
Midbrain ▪ Divided anterior/posterior by cerebral aqueduct ▪ Axons from cerebellum and cerebral cortex form synapses with midbrain nuclei
Pons ▪ Inferior to midbrain, anterior to cerebellum
Medulla oblongata ▪ Inferior part, continuation with spinal cord ▪ Pyramids - bulges on anterior aspect ▪ Olive - swelling lateral to each pyramid
BRAIN STEM: MIDBRAIN ▪ Cerebral peduncles ▪ Corpora quadrigemina ▪ Nuclei
Cerebral peduncles ▪ Three paired, anterior tracts ▪ Motor axons (descending) conduct nerve impulses from motor areas of cerebrum to medulla, pons and spinal cord
Corpora quadrigemina ▪ Superior colliculi - visual reflexes ▪ Inferior colliculi - auditory reflexes
Nuclei Extend to basal nuclei and release dopamine ▪ Help control subconscious muscle activity
BRAIN STEM: PONS ▪ Relays signals for voluntary movements from the cerebral cortex to the cerebellum ▪ Sensory (ascending) tracts ▪ Conduct impulses to higher brain areas ▪ Motor (descending) tracts ▪ Conduct impulses from higher brain areas toward the spinal cord ▪ Pneumotaxic and apneustic areas ▪ Nuclei that work with the medullary rhythmicity area to help control breathing
BRAIN STEM: MEDULLA OBLONGATA ▪ Pyramids ▪ Motor tracts from cerebrum to spinal cord control voluntary movement of trunk and limbs ▪ Decussation (crossing over) of pyramids to opposite side before continuing to spinal cord ▪ Cardiovascular center ▪ Controls heart rate and blood pressure ▪ Medullary rhythmicity area ▪ Adjusts basic rhythm of breathing ▪ Olive ▪ Relay motor impulses to cerebellum
RETICULAR FORMATION ▪ Broad region of brain stem and diencephalon ▪ White matter and gray matter form a netlike arrangement ▪ Reticular activating system (RAS) ▪ Sensory axons - visual, auditory, mental activities ▪ Helps arouse the body from sleep ▪ Maintains attention and alertness (consciousness) ▪ Descending motor function ▪ Regulate posture ▪ Maintain muscle tone
CEREBELLUM: FUNCTION ▪ Highly folded surface that greatly increases surface area of outer gray matter cortex, allowing for greater number of neurons ▪ Evaluates, smoothes, and coordinates contractions of skeletal muscles; also maintains posture and balance
CEREBELLUM: ANATOMY ▪ Vermis ▪ Cerebellar hemispheres ▪ Arbor vitae ▪ Cerebellar peduncles
Vermis Central constricted area
Cerebellar hemispheres Anterior, posterior, and flocculonodular lobes
Arbor vitae Branching, white matter deep to cortex
Cerebellar peduncles ▪ Three, paired tracts ▪ Superior: to midbrain and thalamus ▪ Middle: from pons and cerebral motor cortex ▪ Inferior: sensory information from medulla, pons, and spinal cord
LIMBIC SYSTEM ▪ Broad region including parts of cerebrum and diencephalon ▪ Encircles upper brain stem and corpus callosum ▪ Primary role in emotional aspects of behavior ▪ Pain, pleasure, docility, rage, anger, affection ▪ Also role in memory and olfaction
SPINAL CORD: FUNCTIONS ▪ Assist in maintaining homeostasis ▪ Nerve impulse propagation ▪ Ascending (sensory) or descending (motor) nerve impulse propagation ▪ Information integration ▪ Spinal reflexes - fast, involuntary responses to stimuli processed in the gray matter of spinal cord
SPINAL CORD: EXTERNAL ANATOMY ▪ Oval in shape, slightly flattened anteriorly and posteriorly ▪ Two enlargements ▪ Conus medullaris ▪ Filum terminale
Two enlargements ▪ Cervical - supplies nerves to/from upper limbs ▪ Lumbar - supplies nerves to/from lower limbs
Conus medullaris ▪ Conical portion inferior to lumbar enlargement
Filum terminale Extension of pia mater extending inferiorly to anchor spinal cord to coccyx
SPINAL CORD: SPINAL NERVE ROOTS Connect spinal nerves to segment of cord ▪ Posterior root ▪ Posterior root gangli ▪ Anterior root ▪ Cauda equina
Posterior root Contains sensory axons
Posterior root ganglion Contains cell bodies of sensory neurons
Anterior root Contains axons of motor neurons
Cauda equina Collection of spinal nerve roots that hang inferiorly from spinal cord in the vertebral canal
SPINAL CORD: INTERNAL ANATOMY Anterior median fissure and posterior median sulcus -Gray matter -White matter
Gray matter H-shaped, deep ▪ Anterior, lateral and posterior horns ▪ Gray commissure connects right and left sides and surrounds central canal (cerebrospinal fluid-filled)
White matter cortex ▪ Anterior, lateral, and posterior columns ▪ Ascending (sensory) tracts ▪ Descending (motor) tracts
SPINAL CORD TRACTS Named for position and origin-destination -Ascending (sensory) -Descending (motor)
SPINAL CORD TRACTS-Ascending (sensory) ▪ Spinothalamic tract - pain, warmth, coolness, itching, tickling, deep pressure, crude touch ▪ Posterior column - discriminative touch, light pressure, vibration, conscious proprioception
SPINAL CORD TRACTS-Descending (motor) ▪ Direct pathways - cerebral cortex voluntary movement of skeletal muscles ▪ Indirect pathways - brain stem automatic movements of skeletal muscles
Created by: fieldslady80