Week 8 Content Flashcards
Cerebral Cortex - Functional Regions
- Sensory Areas
- Association Areas
- Motor Areas
Memory and language involve multiple areas
Cerebral Cortex - Information Processing
- Primary sensory cortex receives sensory information
- Information sent to sensory association area
- Multimodal areas integrate input from sensory regions
- Motor plan is executed
Cerebral Cortex - Sensory Areas
Involved in conscious sensation awareness
Parietal, temporal, and occipital lobes
- Specific regions process different senses
Primary Somatosensory Cortex
Along the postcentral gyrus (parietal lobe
General somatic senses, spatial discrimination, and precise stimulus location
Contralateral Projection: Hemispheres process input from the opposite side
Sensory Homunculus
Cortical map of regions dedicated to processing sensory input from different body parts
Fingertips and lips are better at distinguishing precise stimuli
- Larger area
Somatosensory Association Cortex
Posterior to primary somatosensory cortex
Integrates sensory inputs (ie; touch and pressure)
Uses memory to identify objects
Primary Visual Cortex
In the calcarine sulcus sulcus, medial occipital lobe
Largest sensory area
- Processes input from the retina
Contralateral function
First step in visual processing pathways
Visual Association Area
Surrounds the primary visual cortex
Analyzes color, form, and movement
Complex processing extends to temporal and parietal lobes
Primary Auditory Cortex
Superior edge of the temporal lobe
Awareness of sound
Auditory Association Area
Posterior to the primary auditory cortex
Evaluates and interprets sounds
Vestibular Cortex
Posterior insula, deep to the lateral sulcus
Conscious awareness of balance
Gustatory Cortex
In the insula
Conscious awareness of taste
Olfactory Cortex
Medial aspect of cerebrum, piriform cortex
Conscious awareness of smells
Part of the rhinencephalon (nose brain)
- Piriform lobe, olfactory tracts, and olfactory bulbs
Visceral Sensory Area
Lateral sulcus on the insula
Receives sensory input related to…
- Pain
- Pressure
- Hunger
Cortex - Motor Areas
Posterior frontal lobe
Control motor function
1. Premotor cortex
2. Primary motor cortex
3. Frontal eye field
4. Broca’s area
Premotor Cortex
Anterior to precentral gyrus
Plans and coordinates complex movements
Receives sensory input
- Controls voluntary actions based on sensory feedback
Primary Motor Cortex
Precentral gyrus
Controls voluntary motor functions
Contains pyramidal cells (large neurons)
Control specific body areas
Somatotopy
Spatial organization of the body represented in the brain
- Different parts represented by clusters of neurons that correspond to their movement control
- More cells for precise movements
Corticospinal Tracts
Descend through the brainstem and spinal cord
Control skilled movements via motor neurons
Contralateral: Pyramidal axons cross to the opposite side of the brain
Frontal Eye Field
Anterior to the premotor cortex
Controls voluntary eye movement and tracking moving targets
Broca’s Area
In the left hemisphere
Controls speech production
- Language comprehension area
Broca’s Homolog: Right hemisphere region controls emotional tone of speech
Multimodal Association Areas
Integrate sensory input from multiple modalities
Combine information from sensory association areas
Enable complex processing and interpretation of sensory data
Key Multimodal Association Areas
- Posterior association area
- Anterior association area
- Limbic association area
Posterior Association Area
Interface between visual, auditory, and somatosensory areas
Integrates sensory input for unified perception
- Spatial awareness
- Language comprehension and speech
Dorsal (Back) Stream
Extends to the postcentral gyrus
Processes spatial relationships
‘Where’
Ventral (Front) Stream
Extends into the inferior temporal lobe
Recognizes objects, words, and faces
‘What’
Auditory Pathways
Auditory stimuli follow two streams
‘Where’ Pathway: Parietal and lateral frontal lobes, locates sound
‘What’ Pathway: Anterior temporal and inferior frontal lobes, identifies sound
Wernicke’s Area
In the left cerebral cortex
Speech comprehension
Coordination of auditory and visual language
Initiation of word articulation
Recognition of sound sequences
Posterior Association Areas (Right Hemisphere)
Right parietal, temporal, and occipital lobes
Processes spatial, visual, and emotional aspects of communication
Creative interpretation and emotional tone of speech
Anterior Association Area
Prefrontal Cortex
- In the frontal lobe
Integrates information from posterior areas and past experiences
Motor planning and decision-making
Connected to the limbic system for emotion regulation
Prefrontal Cortex
Higher Functions: Thinking, perceiving, memory, abstract reasoning, judgement, and decision-making
Impulses, mental flexibility, and social skills
Humour, empathy, and conscience
Injury or tumors may cause personality and mental disorders
Matures last, fully developed in early adulthood
Limbic Association Area
On the medial frontal lobe
Memory, emotion, and sensory-motor integration
Aids in memory formation and emotional processing
Lateralization of Cortical Functioning
Hemispheres control opposite sides of the body (contralateral)
Left Hemisphere: Language, math, logic
Right Hemisphere: Visual-spatial skills, facial expressions, intuition, emotion, art, music
Images of Left and Right Cerebral Hemispheres
Cerebral White Matter
Connects different areas of the cerebral cortex
Connects the cortex with the brain stem and spinal cord
Composed of myelinated fibers bundled into tracts
White Fiber Tracts of the Cerebral Hemispheres (ACP)
- Association Fibers: Connect regions within the same hemisphere (ie; Wernicke’s and Broca’s area)
- Commissural Fibers: Connect the Hemispheres (ie; Corpus Callosum)
- Projection Fibers: Transmit information to/from the cerebral cortex and lower regions (ie; Interal capsule and corona radiate)
Deep Gray Matter of the Cerebrum
Basal Nuclei (Ganglia)
- Involved in motor control
Basal Forebrain Nuclei
- Associated with memory
Claustrum
- Not fully understood, thought to be involved in memory
Amygdaloid Body
- Part of the limbic system, involved in emotion
Basal Nuclei (CPG)
Group of nuclei deep in cerebral white matter
1. Caudate Nucleus (Movement and learning)
2. Putamen (Voluntary movement)
3. Globus Pallidus (Muscle tone)
Functions of Basal Nuclei
Control voluntary movement with cortex
Receive input from multiple cortical areas
Select appropriate muscles for tasks and inhibit others
Help estimate the passage of time
Involved in regulating movement via the substantia nigra
Basal Forebrain Nuclei
Part of the cholinergic system
- Synthesize and release acetylcholine
Anterior and dorsal to the hypothalamus
Arousal
Learning and memory
Motor control
Degeneration linked to Alzheimer’s disease
Functional Brain Systems
- Limbic System
- Widespread across the forebrain
- Emotions, memory, and behaviour - Reticular Formation
- Extends throughout the brain stem
- Alertness, arousal, and consciousness
Limbic System Key Structures (SCHA)
Medial aspect of cerebral hemispheres
Diencephalon
1. Septal nuclei
2. Cingulate gyrus
3. Hippocampal formation
4. Part of the amygdaloid body
The fornix and other tracts connect the limbic system
Limbic System - Emotional Brain (CHA)
Cingulate Gyrus
- Thought shifting, interprets pain as unpleasant
Hippocampal Formation
- Hippocampus and parahippocampal gyrus
- Memory
Amygdaloid Body (Amygdala)
- Fear
- Emotional responses
Reticular Formation
Central core of the brain stem
- Neurons have long, branching axons
Projects to…
1. Thalamus
2. Cerebellum
3. Spinal cord
Reticular Activating System (RAS)
Widespread connections across the brain
- Essential for brain arousal and alertness
Filters out repetitive stimuli
Regulates sleep and awakening
- Malfunctions linked to narcolepsy
Various Brain Parts and Their Functions
Brain Protection
- Skull
- Physical barrier - Meninges
- Protective membranes - Cerebrospinal Fluid (CSF)
- Cushions and nourishes - Blood-Brain Barrier (BBB)
- Regulates chemical environment
Skull
Encases and protects the brain
Cranial Bones
- Frontal (1)
- Occipital (1)
- Sphenoid (1)
- Ethmoid (1)
- Parietal (2)
- Temporal (2)
Meninges
Protect and cover the CNS
Enclose and protect blood vessels supplying the CNS
Contain CSF
- Pia mater
- Arachnoid mater
- Dura mater
Mnemonic: Meninges ‘PAD’ the brain
Dura Mater
Toughest layer
Periosteal Layer: Attached to skull
Meningeal Layer: Outer covering of the brain
Layers fused except to encolose dural sinuses
- Largest Sinus: Superior Sagittal Sinus
Partitions of Dura Mater
Falx Cerebri: Separates cerebral hemispheres
Tentorium Cerebelli: Separates cerebrum from cerebellum
Falx Cerebelli: Separates cerebellar hemispheres
Diaphragma Sellae: Forms roof of the sella turcica, encloses pituitary gland
Arachnoid Mater
Beneath the dura mater
Arachnoid Villi
- Small projections through the dura mater
Facilitate passage of CSF into dural venous sinuses
Pia Mater
Innermost Layer
Thin, delicate, connective tissue
Tightly adheres to brain surface
Follows all cortical folds (convolutions)
Highly vascular
Cerebrospinal Fluid (CSF)
Fills brain and spinal cord cavities
- Liquid cushions the brain and spinal cord
Nourishes, removes wastes, and carries signals in the CNS
Formation of Cerebrospinal Fluid
Produced in choroid plexuses of brain ventricles
Composed of ependymal cells and capillaries
Derived from blood, with 100-160mL present at a time
Blood-Brain Barrier
Prevents most toxins from entering the brain
Selective, semi-permeable capillaries
Allows nutrients and substances to pass through
Spinal Cord
Connects spinal nerves
2-way communication pathway
Reflex center
Extends from the foramen magnum to the L1/L2 vertebra within the vertebral canal
Spinal Cord Anatomy
Conus Medullaris: Tapered end of the spinal cord
Filum Terminale: Connective tissue anchoring the spinal cord to the coccyx
Cervical and Lumbar Enlargements: Nerve origins for limbs
Cauda Equina: Bundle of spinal nerve roots
Spinal Cord Segments
Regions where spinal nerves emerge
Named for the corresponding spinal nerve
Spinal Cord Grooves
Two deep grooves span the length of the cord
1. Dorsal median sulcus
2. Ventral median fissure
White Matter of the Spinal Cord
Outer layer made of myelinated and nonmyelinated axons
Communication between the brain and spinal cord
Organized into dorsal, lateral, and ventral columns
Types of Fibers
Ascending: Carry sensory information to the brain
Descending: Transmit motor commands from the brain
Commissural: Connect opposite sides of the spinal cord
Gray Matter of the Spinal Cord
Neuronal cell bodies and nonmyelinated axons
Regions of Gray Matter
1. Gray commissure
2. Dorsal horns
3. Ventral horns
4. Lateral horns
Gray Matter Regions
H-shaped structure with a central canal
Gray Commissure: Connects the two sides, enclosing the central canal
Key Spinal Cord Structures
Dorsal Horns: House interneurons processing sensory information
Ventral and Lateral Horns: Contain motor neuron cell bodies
Gray Matter Regions - Functions
SS (Somatic Sensory)
- Sensory input from skin and muscles
VS (Visceral Sensory)
- Sensory input from internal organs
VM (Visceral Motor)
- Autonomic motor control for internal organs
SM (Somatic Motor)
- Motor output to skeletal muscles
Somatic and Visceral Pathway Structures
Dorsal Root Ganglion
- Cluster of sensory neuron cell bodies outside the spinal cord
Dorsal/Sensory Root
- Pathway for sensory neurons entering the spinal cord
Dorsal Horn
- Gray matter region that processes sensory input via interneurons
Motor Pathway Structures
Ventral/Motor Root
- Pathway for motor neurons to send commands from the brain to the muscles and glands
Ventral Horn
- Gray matter region housing motor neuron cell bodies
Somatic Motor Neurons
- Control voluntary movement of skeletal muscles
Visceral Motor Neurons
- Control involuntary functions (ie; heart, digestion)
Spinal Nerve
- Mixed nerve
Spinal Cord Protection
Vertebrae
Spinal Meninges (Pia, arachnoid, and dura mater)
Epidural Space (Contains fat, surrounds dura mater)
Subdural Space (Between dura and arachnoid mater)
Subarachnoid space (Filled with CSF)
Meninges
Dura Mater: Tough, outer layer
Arachnoid Mater: Middle layer
Pia Mater: Innermost delicate connective tissue layer, extends to the coccyx
Denticulate Ligaments: Lateral extensions of pia mater, stabilize the spinal cord
Spinal Tap (Lumbar Puncture)
Collect CSF, deliver anesthetics or chemotherapy
Needle inserted between vertebrae (L3-L4 or L4-L5)
Through the supraspinous ligament or ligamentum flavum
Reaches the subarachnoid space
Sensory and motor Pathways in the CNS
Multi-neuron pathways connect the brain to the body
- Consist of tracts
Ascending Pathways: Carry sensory information to brain areas
Descending Pathways: Transmit motor commands from the brain to the body
Ascending Pathways
Transmit general somatic sensory impulses
Involves chains of neurons; first, second, and third order
1. Spinothalamic pathway
2. Dorsal column pathway
3. Spinocerebellar pathway
Spinothalamic Tracts
Transmit pain, temperature, and crude touch sensations to the thalamus
Lateral Spinothalamic: Carries pain and temperature information
Ventral (Anterior) Spinothalamic: Carries crude touch and pressure sensations
Dorsal White Column
Carries fine touch, proprioception, and pressure sensations
Fasciculus Gracilis: Transmits sensory information from the lower body
Fasciculus Cuneatus: Carries sensory information from the upper body
Spinocerebellar Tracts
Transmit proprioceptive information to the cerebellum for coordination
Dorsal Spinocerebellar: Carries information from the lower limbs and trunk
Ventral Spinocerebellar: Carries proprioceptive input from the lower body
Descending Pathways
Most motor pathways
Consist of 203 neurons
Deliver motor commands from the brain to the spinal cord
Types of Descending Pathways
- Direct Pathways
- Carry voluntary motor commands from the cerebral cortex to the spinal cord
- ie; Pyramidal tracts - Indirect Pathways: Multiple synapses, modulate motor activity through brainstem nuclei
Direct Motor Pathways
Corticospinal (Pyramidal) Tracts
- Originates in the primary motor cortex
- Terminates in the spinal cord
- Lateral corticospinal tract
- Controls voluntary movement of distal limbs - Ventral corticospinal tract
- Controls voluntary movement of axial muscles
Indirect Motor Pathways
- Tectospinal tract
- Vestibulospinal tract
- Reticulospinal tract
- Rubrospinal tract
Tectospinal Tract
Coordinates head and neck movements
Originates in superior colliculus of the midbrain tectum
Terminates in the cervical spinal cord
Responds to visual, auditory, and pain stimuli
Reticulospinal Tract
Carry information from the brain stem to periphery
Medial reticulospinal tract: Regulates posture and balance, originates from the pontine reticular formation
Lateral reticulospinal tract: Controls muscle tone and movement, originates from the medullary reticular formation
Terminates in the spinal cord
Vestibulospinal Tract
Maintain balance and posture
Controls trunk and limb muscles
Originates from the vestibular nuclei of the brain stem (pons and medulla)
Terminates in the anterior gray matter of the spinal cord
Rubrospinal Tract
Involved in motor control, specifically movement coordination of limbs
Originates in the midbrain at the red nucleus
Moves down through the pons and medulla oblongata
Terminates in the cervical spinal cord
Funiculi
Bundles of nerve fibers (axons) in white matter
Dorsal Funiculus: Sensory pathways (ie; fasciculus gracilis, cuneatus)
Lateral Funinculus: Sensory and motor pathways (ie; spinothalamic corticospinal)
Ventral Pathways: Motor pathways (ie; corticospinal tract)
Spinal Cord Injury
Paralysis: Loss of motor function
Parasthesia: Loss of sensation
Paraplegia: Injury between T1 and L2, lower limb paralysis
Quadriplegia: Injury in cervical region, paralysis of all four limbs
Degenerative Brain Disease
Parkinson’s Disease: Loss of motor control due to damage in the basal nuclei
Multiple Sclerosis (MS): Autoimmune disorder destroying myelin sheaths
Alzheimer’s Disease: Progressive loss of memory and cognition, abnormal build-up of proteins amyloid and tau
Traumatic Brain Injury (TBI)
Damage caused by external forces
Causes contusions
Concussion: Temporary brain function disruption from a mild TBI
Stroke
Cerebrovascular accident
Blockage or interruption of blood flow to a brain region
- Causes tissue damage
Ischemic Stroke: Blocked blood vessel
Hemorrhagic Stroke: Burst blood vessel
CNS Cancer
Gliomas: Tumours arising from glial cells
Meningiomas: Tumours originating in the meninges
May compress brain or spinal cord
CNS Infections
Meningitis: Inflammation of meninges caused by bacteria or viruses
Encephalitis: Inflammation of brain tissue due to infection
Aging Central Nervous System
Atrophy
Neuroplasticity declines
Increased vulnerability to injury
Increased risk for neurodegenerative diseases
Diminished sensation, balance, and movement control
