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Central Nervous System Chapter 13 – Lecture Notes
to accompany Anatomy and Physiology: From Science to Life textbook by Gail Jenkins, Christopher Kemnitz, Gerard Tortora
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Chapter Overview 13.1 Central Nervous System
13.2 Protection and Nourishment of the CNS 13.3 Cerebrum 13.4 Limbic System 13.5 Signal Processing in the Cerebrum 13.6 Diencephalon 13.7 Brain Stem 13.8 Cerebellum 13.9 Spinal Cord 13.10 Propagation of Impulses
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Essential Terms Central Nervous System (CNS) brain and spinal cord
control center for thoughts emotions creativity wisdom memories activities behaviors Tract bundle of axons
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Introduction CNS made up of ~100 billion neurons
Adult brain mass of ~1300g (3 lbs) Spinal cord mediates rapid reactions reflexes pathway for sensory nerve impulses to brain pathway for motor nerve impulses from brain
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Concept 13.1 Central Nervous System
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CNS Brain Spinal Cord medulla oblongata to superior edge of L2
cerebrum cerebral hemispheres diencephalon brain stem cerebellum Spinal Cord medulla oblongata to superior edge of L2 Protection of CNS two types of connective tissues bony skull cranial and spinal meninges cushion of cerebrospinal fluid
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Figure 13.1a
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Figure 13.1c
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Figure 13.2
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Skeletal Protection Brain is located in cranial cavity of skull
Spinal cord is located within vertebral canal of vertebral column vertebral foramina of vertebrae stacked one on top of one another form the vertebral canal
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Meninges three connective tissue coverings that encircle brain and spinal cord cranial meninges spinal meninges superficial to deep dura mater arachnoid mater pia mater
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Figure 13.3a
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Figure 13.4a
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Dura Mater of Brain falx cerebri falx cerebelli tentorium cerebelli
most superficial adheres to periosteum of cranial bones strongest menix extensions separate portions of brain falx cerebri two hemispheres of cerebrum falx cerebelli two hemispheres of cerebellum tentorium cerebelli separates cerebrum from cerebellum
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Dura Mater of Spinal Cord
between dura mater and all of vertebral canal epidural space cushion of fat dura mater tissue sinuses that act as collection points for interstitial fluid and blood leaving brain return interstitial fluid and blood to internal jugular veins of neck
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Arachnoid Mater avascular collagen fibers some elastic fibers
surrounds both brain and spinal cord subdural space thin space between dura mater and arachnoid matter contains interstitial fluid
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Pia Mater innermost membrane tightly adheres to surface of CNS
interlacing bundles of collagen fibers some fine elastic fibers surrounds both brain and spinal cord subarachnoid space thin space between arachnoid mater and pia matter contains cerebrospinal fluid also covers surface blood vessels of CNS
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Meninges and Spinal Nerves
All three cover spinal nerves up to point of exit from spinal column through intervertebral foramina
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Denticulate Ligaments
suspend spinal cord in middle of dural sheath membranous extensions of pia mater project laterally and fuse with arachnoid mater and inner surface of dura mater between anterior and posterior nerve roots of spinal nerves on either side protect spinal cord against shock and sudden displacement
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Concept 13.2 Nourishment and Protection
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Blood Flow to CNS to brain via to spinal cord via
internal carotid and vertebral arteries flows into dural sinuses empties into internal jugular veins to spinal cord via posterior intercostal and lumbar arteries empties into posterior intercostal and lumbar veins
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Figure 20.20c
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Figure 20.20d
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Blood Flow to Brain Brain at rest uses 20% of oxygen and glucose
even though only 2% of mass of adult Neurons synthesize ATP almost exclusively from glucose when activity increases in a particular region, blood flow to that area also increases
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Blood Flow to Brain decreased blood flow to brain
short time can cause unconsciousness 1 to 2 minutes impairs neuronal function 4 minutes causes permanent injury virtually no glucose stored in the brain low blood glucose to brain can cause mental confusion dizziness convulsions loss of consciousness
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Blood Flow to Brain Blocked blood flow to brain
arterial blockage can damage brain CVA cerebrovascular accident stroke most common brain disorder affect 500,000 people per year in US 1/3 leading cause of death
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Blood Brain Barrier Physiology protects CNS from harmful substances
pathogens prevents passage from blood into interstitial fluid of neural tissue water soluble substances usually pass by active transport others pass slowly lipid soluble substances pass readily
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Blood Brain Barrier Anatomy
cerebral arteries divide quickly into capillaries tight junctions seal together endothelial cells of CNS capillaries capillaries also surrounded by thick basement membrane astrocyte processes press against capillaries selectively pass some substances and inhibit others
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Cerebrospinal Fluid (CSF)
ml volume clear colorless liquid protects and nourishes brain & spinal cord protects against chemical and physical injuries acting as shock absorber on which brain floats nourishes by carrying oxygen glucose other chemicals continuously circulates through cavities in and around CNS in subarachnoid space
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Cerebrospinal Fluid (CSF)
Contributes to homeostasis in three ways: mechanical protection shock absorber chemical protection circulation
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Figure 13.5a
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Formation of CSF CSF fills ventricles CSF produced in choroid plexuses
lateral ventricles located in each hemisphere of cerebrum separated by septum pellucidum third ventricle fourth ventricle CSF produced in choroid plexuses capillaries in walls of ventricles covered by ependymal cells that form CSF from blood plasma by filtration and secretion
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Circulation of CSF Cilia on ependymal cells assist with flow
from lateral ventricles through interventricular foramina to third ventricle then through cerebral aqueduct into fourth ventricle enters subarachnoid space through median aperture pair of lateral apertures reabsorbed into blood arachnoid villi
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Figure 13.6a
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Figure 13.3a
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Figure 13.6c
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Concept Cerebrum
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Cerebrum Seat of intelligence Cerebral Cortex White matter on inside
interprets sensory impulses controls muscular movements functions in emotional and intellectual processes Cerebral Cortex gray matter on outside receives & integrates incoming & outgoing information White matter on inside white is myelination Gray matter nuclei deep within white matter
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Cerebral Cortex connected internally by corpus callosum
enlarges faster during embryonic development than white matter rolls and folds forming gyri (singular = gyrus) bulges or folds fissures deep grooves longitudinal fissure separates cerebrum into left and right hemispheres connected internally by corpus callosum sulci (singular = sulcus) shallow fissures
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Figure 13.7a
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Figure 13.7b
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Figure 13.7c
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has tracts Cerebral White Matter myelinated and unmyelinated axons
communicate between regions of CNS three types association tracts between gyri in same hemisphere commissural tracts from gyri in one hemisphere to corresponding gyri in other hemisphere projection tracts from cerebrum to lower parts of CNS
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Basal Nuclei mass of cell bodies
two are side by side just lateral to thalamus globus pallidus and putamen third is caudate nucleus large “head” connected to smaller “tail” by long comma-shaped “body” receive input from cerebral cortex provide output to motor portions control subconscious contractions of skeletal muscles
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Table 13.2 part 1
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Table 13.2 part 2
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Table 13.2 part 3
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Table 13.2 part 4
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Table 13.2 part 5
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Concept Limbic System
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Limbic System controls emotion, behavior, and memory
encircles upper part of brain stem and corpus callosum ring of structures on inner border of cerebrum and floor of diencephalon controls most involuntary aspects of behavior related to survival intense pain extreme pleasure anger/rage affection recognition of fear
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Concept 13.5 Functional Areas of Cerebrum
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Functional Areas of Cerebrum
Sensory areas receive sensory impulses Motor areas initiate movements Association areas complex integrative functions memory emotions reasoning will judgment personality traits intelligence
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Figure 13.10
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Sensory Areas Posterior half of both hemispheres
behind central sulci most direct connections with peripheral sensory receptors primary somatosensory area receives impulses for touch, proprioception, pain, itching, tickle, thermal sensations localize exactly the points where sensations originate primary visual area receives impulses for vision eye to thalamus to primary visual area shape, color, movement of visual stimuli
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Sensory Areas primary auditory area primary gustatory area
receives impulses for basic characteristics of sound pitch and rhythm primary gustatory area receives impulses for taste primary olfactory area receives impulses for smell
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