Chapter 12 Flashcards
Central Nervous System (CNS)
Brain and Spinal Cord
Cephalization
More developed brain
Neurons
Embryonic Developement
Brain and Spinal Cord start as neural tube
Neural Tube: 3 Primary Vesicles at Anterior End
Forebrain
Midbrain
Hindbrain
Neural Tube: Posterior End
Spinal Cord
Brain vs. Membranous Skull
Brain develops faster
- Folds
- Forebrain moved towards brain stem
- Cerebral hemispheres envelope midbrain
Creases and Folds Purpose in Brain
Caused by developing fast
-Increases surface area
Regions of Brain
Cerebral hemispheres
Diencephalon
Brain Stem
Cerebellum
Spinal Cord
Central cavity surrounded by gray matter
External white matter
Brain
Higher amounts of gray matter in brain
Two parts
-Cerebral hemispheres
-Cerebellum
Cortex
The outer gray matter of the cerebral hemispheres and cerebellum
-Disappears in brain stem- scatters
Ventricles of Brain
Filled with cerebrospinal fluid
Lined by ependymal cells
Connected to one another and to central canal of spinal cord
Lateral Ventricles
Third ventricle via interventricular foramen
Third Ventricle
Fourth ventricle via cerebral aqueduct
Third and Fourth Ventricles
Paired, C-shaped lateral ventricles in cerebral hemispheres
Septum
Separating lateral ventricles of brain (Look at Diagram)
Gyrus (Gyri)
Ridge, mountain like
Sulcus (Sulci)
Valley
Fissure (Fissures)
Deep Groove
Longitudinal Fissure
Location
-Right sagittal
Function/Purpose
-Makes right and left
Transverse Cerebral Fissure
Location -Cerebrum -Cerebellum Function/Purpose -Makes top and bottom
Cerebral Hemispheres (5 Lobes)
Frontal Parietal Temporal Occipital Insula
Central Sulcus
Separates frontal lobe and parietal lobe
Parieto-Occipital Sulcus
Separates occipital and parietal lobes
Lateral Sulcus
Outlines temporal lobes
3 Layers of Cerebral Hemispheres
Cerebral Cortex
White Matter
Basal Nuclei
Cerebral Cortex
Gray matter superficially
White Matter
Internal
Basal Nuclei
Deep within the white matter
Cerebral Cortex
Thin- superficial layer
40% mass of brain
Cerebral Cortex (Site of Conscious Mind)
Awareness Sensory Perception Voluntary Motor Initiation (versus reflex) Communication Memory Storage Understanding
Cerebral Cortex (Functional Areas)
Motor Area
Sensory Area
Association Area
Motor Area
Control voluntary movement
Sensory Area
Conscious awareness of sensation
Association Areas
Integrate diverse information
Motor Areas of Cerebral Cotrex
Frontal Lobe
Primary Motor Cortex in Precentral Gyrus
Premotor Cortex anterior to Precentral Gyrus
Frontal Lobe
Control of voluntary movement
Primary Motor Cortex
Long axons
-Corticospinal Tracts of spinal cord
-Allows conscious control of precise/skilled movements
Motor Homunculi
-upside-down caricatures
-Contralateral motor innervation of body regions
Premotor Cortex
Plans movement
Controls repetitious/patterned motor skills
Coordinates simultaneous or sequential actions
Controls voluntary actions that depend of sensory feedback
Broca’s Area
Present in one hemisphere
-Left
Motor Speech area that directs muscles of speech production
Active in planning speech and voluntary motor activities
Primary Somatosensory Cortex
In postcentral gyri of parietal lobe
- Proprioceptors
- Spatial Discrimination
- Somatosensory Homunculus
Visual Areas
Visual Association Area
- Surrounds primary visual cortex
- Uses part experiences to interpret visual stimuli
- Complex processes involves entire posterior half of cerebral hemispheres
Auditory Areas (2 Parts)
Primary Auditory Cortex
Auditory Association Area
Primary Auditory Cortex
Superior margin of temporal lobes
Interprets information from inner ear as pitch, loudness, and location
Auditory Association Area
Located posterior to primary auditory cortex
Stores memories of sounds and permits perception of sound stimulus
Vestibular Cortex
Responsible for conscious awareness of balance (position of head in space)
Olfactory Cortex
Smell
- Medial aspect of temporal lobes
- Olfactory bulbs and tracts
- Part of limbic system
- Region of conscious awareness of odors
Gustatory Cortex
Deep to temporal lobe
Involved in perception of taste
Visceral Sensory Area
Posterior to gustatory cortex Conscious perception of visceral sensations Examples -Upset stomach -Full bladder
Multimodal Association Areas (3 Parts)
Anterior Association Area
Posterior Association Area
Limbic Association Area
Anterior Association Area (Prefrontal Cortex)
Involves
-Intellect
-Cognition
-Recall
-Personality
Contains working memory needed for abstract ideas, judgement, reasoning, persistence, and planning
Development depends on feedback from social environment
Posterior Association Area
Large Region:
-Temporal
-Parietal
-Occipital
Recognizes patterns and faces and localizing us in space
Involved in understanding written and spoken language (Wernicke’s Area)
Limbic Association Area
Part of Limbic System
Involves Hippocampus
Provides emotional impact, helps establish memories
Lateralization of Cortical Function
Hemispheres almost identical
Cerebral Dominance- dominate for language
Lateralization
Right and Left
Left Hemisphere
Language
Math
Logic
Right Hemisphere
Visual-spatial skills Intuition Emotion Artistic Skills Musical Skills
Hemisphere Communication
Instantly due to fiber tracts
Cerebral White Matter
Myelinated fibers and tracts
Communication between cerebral areas, and between cortex and lower CNS
-same
-between
Diencephalon (3 Paired Structures)
Thalamus
Hypothalamus
Epithalamus
Thalamus
80% of diencephalon
Bilateral nuclei connected by interthalamic adhesion
-Contains several nuclei, named for location
-Nuclei project and receive fibers from cerebral cortex
Thalamus Function
Gateway to cerebral cortex
Sorts, edits, and relays ascending input
Mediates sensation, motor activities, cortical arousal, learning, and memory
Hypothalamic Function
Controls Autonomic Nervous System Physical responses to emotions Regulates -Body temperature -Hunger -Thirst -Wake-Sleep -Endocrine System
Epithalamus
Most dorsal portion of diencephalon
Pineal Gland
Pineal Gland
Extends from posterior border and secretes melatonin
Melatonin
Helps regulates sleep-wake cycle
Brain Stem (3 Parts)
Midbrain
Pons
Medulla Oblongata
Brain Stem
Similar structure to spinal cord but contains nuclei embedded in white matter
Controls automatic behaviors necessary for survival
Nuclei associated with 10 or the 12 pairs of cranial nerves
Pons
4th ventricle separates pons and cerebellum
Fiber of pons:
-Connect higher brain centers and spinal cord
-Relay impulses between motor cortex and cerebellum
Origin of cranial nerves V (trigeminal), VI (abducens), VII (facial)
Nuclei help maintain normal rhythm of breathing
Medulla Oblongata (Medulla)
Joins spinal cord at foramen magnum
Contains choroid plexus of fourth ventricle
Two ventral longitudinal ridges formed by pyramidal tracts
Cranial nerves are associated with medulla
Several nuclei relay sensory information
Decussation of Pyramids
Crossover of corticospinal tracts
Inferior Olivary Nuclei
Relay sensory information from muscles and joints to cerebellum
Vestibular System
(Pons and Medulla)
Mediate responses that maintain equilibrium
Medulla Oblongata Functions
Autonomic reflex center
-Functions overlap with hypothalamus
Cardiovascular Center
Respiratory Center
Cardiovascular Center
Cardiac center adjusts force and rate of heart contraction
Vasomotor center adjusts blood vessel diameter for blood pressure regulation
Respiratory Center
Generate respiratory rhythm
Control rate and depth of breathing
Cerebellum
11% of brain mass
Dorsal to pons and medulla
Input from cortex, brain stem and sensory receptors
Allows smooth, coordinated movements
Cerebellum Function
Receives impulses from cerebral cortex
-initiate voluntary muscle contraction
Role in thinking, language, and emotion
Functional Brain Systems
Networks of neurons that work together but span wide areas of brain
- Limbic System
- Reticular Formation
Limbic System
Structures on medial aspects of cerebral hemispheres and diencephalon
Located in Middle Brain
Limbic System Function
Emotional or affective brain -Recognition -Expression Emotional Responses to odors -Example skunks smell bad Most output relayed via hypothalamus
Limbic System: Emotion and Cognition
Limbic systems interacts with prefrontal lobes
- React emotionally to things we consciously understand to be happening
- Consciously aware of emotional richness in our lives
Hippocampus
Plays a role in memory
Brain Wave Patterns and EEG
EEG= Electroencephalogram
Records electrical activity that accompanies brain function
Measures electrical potential differences between various cortical areas
Brain Waves
Patterns of neuronal electrical activity
Generated by synaptic activity in cortex
Each person’s brain waves are unique
Can be grouped into four classes based on frequency measured as Hertz (Hz)
Types of Brain Waves
Alpha
Beta
Theta
Delta
Alpha
8-13 Hz
Regular and rhythmic, low-amplitude, synchronous waves indicating an “idling” brain
Beta
14-30 Hz
Rhythmic, less regular waves occurring when mentally alert
Theta
4-7 Hz
More irregular, common in children and uncommon in awake adults
Delta
4 Hz or less
High-amplitude waves of deep sleep, indicate brain damage in awake adult
Brain Waves: State of the Brain
Change with age, sensory stimuli, brain disease, and chemical state of brain
EEGs used to diagnose and localize brain lesions
Epilepsy
Loss of consciousness, fall stiffly, and have uncontrollable jerking
Intelligence or lack there of
Incidence
Aura
Sensory Hallucination may precede seizure
Absence Seizures
Petit Mal
Mild seizures; few seconds
Tonic-Clonic Seizures
Grand Mal
Most severe: few minutes
Control of Epilepsy
Vagus Nerve stimulation or deep brain
-Simulators that affect certain areas of brain to prevent seizures
Anti-convulsive drugs
Consciousness
Perception of sensation Movement Loss of consciousness signal that brain function impaired -Fainting/Syncopy -Coma
Sleep and Sleep Wake Cycles
Non-Rapid Eye Movement (NREM) Sleep
Rapid Eye movement (REM) Sleep
Narcolepsy
Abrupt lapse into sleep from awake state
Often have cataplexy
Insommnia
Chronic inability to obtain amount/quality of sleep needed
Sleep Apnea
Temporary cessation of breathing during sleep
Causes hypoxia
Memory
Storage and retrieval of information
Two Stages of Memory Storing
Short Term- not needed for life
Long Term- limitless capacity
Factors Affecting Transfer from Short Term to Long Term Memory
Emotional State- Alert Motivated
Rehearsal
Association
Automatic Memory
Protection of Brain
Bone
Membrane
Watery Cushion
Blood Brain Barrier
Meninges
Cover and protect CNS
Protect blood vessels and enclose venous sinuses
Contain cerebrospinal fluid (CSF)
Form partitions in skull
3 Layers of Meninges
Dura Mater
Arachnoid Mater
Pia Mater
Meningitis
Inflammation of meninges
Arachnoid Mater
Middle layer with weblike extensions
Subarachnoid Space
Contains CSF and largest blood vessels of brain
Cerebrospinal Fluid (CSF)
Watery solution form from blood plasma
-Less protein and different ion concentrations than plasma
Constant volume
Functions of Cerebrospinal Fluid
Buoyancy
Protects
Nourishes
Choroid Plexuses
Hang from roof of each ventricle: produce CSF at constant rate: keep in motion
Normal Volume: 150 mL, replaced every 8 hours
Hydrocephalus
Obstruction blocks CSF circulation or drainage
Unfused skull bones of newborn allow enlargement of head
Brain damage in adult due to rigid adult skull
Treated by draining with ventricular shunt to abdominal cavity
Blood Brain Barrier
Helps maintain stable environment for brain
Separates neurons from some blood borne substances
Composition of Blood Brain Barrier
Contrinous endothelium of capillary walls
Thick basal lamina around cappilaries
Function of Blood Brain Barrier
Selective Barrier
- Allows nutrients to move by facilitated diffusion
- Denies metabolic wastes, proteins, toxins, most drugs, small nonessential amino acids, and K+
- Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics
Homeostatic Imbalances of the Brain
Traumatic Brain Injuries
OR
Cerebrovascular Accidents (CVA’s or Strokes)
Concussion
Temporary
Contusion
Permanent damage
Subdural or Subarachnoid Hemorrhage
Could result in death
Cerebral Edema
Swelling of brain associated with traumatic head injury
Ischemia
Tissue deprived of blood supply: brain tissue dies
Example
-Blockage of cerebral artery by blood clot
Hemiplegia
One side
Transient Ischemic Attacks (TIA)
Temporary episodes of reversible cerebral ischemia
Tissue Plasminogen Activator (TPA)
Only approved for treatment of strokes
Parkinson’s Disease
Degeneration of dopamine-releasing neurons of substantia nigra
Basal nuclei deprived of dopamine become over-active; tremors at rest
Unknown Cause
Treated with L-Dopa: Deep brain stimulation
Huntington’s Disease
Fatal hereditary disorder
-wild jerky flapping movements
Treated with drugs that block dopamine effects
Spinal Cord Location
Begins at Foramen Magnum
Ends Lumbar 2 Vertebrae
Spinal Cord Function
Provides 2-way communication to and from brain
Contains Spinal Reflex Centers
Spinal Cord Protection
Bone, meninges, and CSF
Epidural Space- Cushioning
CSF in subarachnoid space
Dural and arachnoid membranes extend to sacrum
Spinal Nerves
31 Pairs
Cervical and lumbosacral enlargements
-Nerves serving upper and lower limbs emerge here
White Matter
Myelinated and nonmyelinated nerve fibers allow communication between:
-Parts of spinal cord
-Spinal cord to brain
Each spinal tract composed of axons with similar destinations
3 Directions of White Matter
Ascending
Descending
Transverse
White Matter Divided into 3 Columns on Each Side
Dorsal
Lateral
Ventral
Ascending Pathways 3 Neurons
First
Second
Third
Transmit somatosensory information to sensory cortex via thalamus or terminate in the cerebellum
First Neuron
- Conducts impulses from cutaneous receptors and proprioceptors
- Branches diffusely as enters spinal cord or medulla
- Synapses with second order neuron
Second Neuron
- Interneuron
- Cell body in dorsal horn of spinal cord
- Axons extend to thalamus or cerebellum
Third Neuron
- Interneuron
- Cell body in thalamus
- Axon extends to somatosensory cortex
Spinal Cord Trauma
Functional Losses
- Paresthesias- Sensory Loss
- Paralysis- Loss of Motor Function
Flaccid Paralysis
Severe damage to ventral root or ventral horn cells
-End result
Paraplegia
Transection between Thoracic 1 and Lumbar 1
Quadriplegia
Transection in Cervical Region
