CH 14: 9-27-13 (BIO181) Flashcards
• The brain consists of six regions
- Cerebrum
- Cerebellum
- Diencephalon
- Brainstem – 3 parts
- Mesencephalon
- Pons
- Medulla oblongata
- Largest part of brain
- Controls higher mental functions
- Divided into left and right cerebral hemispheres
- Contains an outer surface layer of gray matter (neural cortex)
cerebrum (cortex)
- Folded surface increases surface area
- Elevated ridges (gyri)
- Shallow depressions (sulci)
- Deep grooves (fissures)
• Neural cortex (cerebral cortex)
- Second largest part of brain
- Coordinates repetitive body movements
- Two hemispheres
- Covered with cerebellar cortex
cerebellum
- Located under cerebrum and cerebellum
- Links cerebrum with brain stem
- Two divisions (thalamus and hypothalamus)
• Diencephalon
• Relays and processes sensory information in diencephalon
thalamus
• Neural AND endocrine functions
– Hormone production
– Emotion
– Autonomic function
hypothalamus
- Major endocrine gland
- Connected to hypothalamus via infundibulum (stalk)
- Acts as the interface between the nervous and the endocrine systems
• Pituitary gland (anterior and posterior)
brain stem 3 parts
mesencephalon, pons, medulla oblongata
- Also called midbrain
- Processes sight, sound, and associated reflexes
- Maintains consciousness
- THIS IS THE SENSORY-MOTOR INTEGRATOR!
• Mesencephalon
- Connects cerebellum to brain stem
* Is involved in somatic and visceral motor control
• Pons
• Connects brain to spinal cord
• Relays sensory information
• Regulates autonomic functions:
– heart rate, blood pressure, and digestion
• Medulla oblongata
• The CNS begins as a hollow
neural tube
• Throughout development, the_____ _____ (region that will become brain) expands
cephalic region
– Prosencephalon Will become
forebrain
mesencephalon will become
midbrain
rhombencephalon will become
hindbrain
• Prosencephalon and Rhombencephalon further differentiate into
secondary brain regions
• Prosencephalon differentiates into the _____ (which becomes cortex) and _____
Telencephalon; Diencephalon
mesencephalon changes the ____ during growth
least
• During development, the Neural tube encloses a _____
neurocoel (a fluid filled internal cavity)
• This Neurocoel expands to form _____ lined with ependymal cells
chambers (ventricles)
• Eventually, each cerebral hemisphere contains one large
Lateral ventricle
- Ventricle of the diencephalon
* Lateral ventricles communicate with third ventricle via the interventricular foramen
• Third ventricle
- Extends into medulla oblongata
* Becomes continuous with central canal of the spinal cord
• Fourth ventricle
- Bones of the cranium
- Cranial meninges
- Cerebrospinal fluid
physical protection of the brain
blood brain barrier
biochemical isolation of brain
- Protect the brain from cranial trauma
* Have three layers:
cranial meninges
• Inner fibrous layer (meningeal layer)
• Outer fibrous layer (endosteal layer)
• Venous sinuses are between the two layers
– Contain fluids and blood vessels
– Receives venous blood and delivers it to the jugular veins
dura mater of brain
- Covers brain
- Contacts epithelial layer of dura mater
- Subarachnoid space: between arachnoid mater and pia mater
arachnoid mater of brain
• Attached to brain surface by astrocytes
pia mater of brain
- Surrounds all exposed surfaces of CNS
- Functions of CSF
- Cushions neural structures
- Supports brain
- Transports nutrients, chemical messengers, and waste products
CFS
• Consists of specialized ependymal cells and capillaries:
– secrete CSF into ventricles
– remove waste products from CSF
– adjust composition of CSF
• Formation of CSF starts in the Choroid plexus
- From choroid plexus
- Through ventricles
- To central canal of spinal cord
- Into subarachnoid space around the brain and spinal cord
circulation of CSF
• extend through dura mater to superior sagittal sinus
• Clusters of these villi are called Arachnoid granulations
– Function in absorbing CSF into venous ciculation
• Subarachnoid space contains Arachnoid villi:
- Isolates CNS neural tissue from general circulation
- Formed by network of tight junctions between endothelial cells of CNS
- Allows ONLY lipid-soluble compounds (O2, CO2), steroids, and prostaglandins to diffuse into interstitial fluid of brain and spinal cord
- Astrocytes control blood–brain barrier by releasing chemicals that control the permeability of endothelium
• Blood-Brain Barrier
- Meninges stabilize brain in cranial cavity
- Cerebrospinal fluid cushions and protects against sudden movement
- CSF provides nutrients and removes wastes
- Blood–brain barrier and blood–CSF barrier
- Selectively isolate brain from chemicals in blood that might disrupt neural function
Brain Protection and Support Summary
• Supplies nutrients and oxygen to brain
• Arterial blood supply
– Delivered by internal carotid arteries and vertebral arteries
• Venous blood
– Removed from dural sinuses by internal jugular veins
- When things go wrong = Cerebrovascular Disease
- Disorders interfere with blood circulation to brain
- Stroke or cerebrovascular accident (CVA)
- Shuts off blood to portion of brain
- Neurons die within minutes
blood supply to brain
- Is the largest part of the brain
- Controls all conscious thoughts and intellectual functions (higher functions)
- Processes somatic sensory and motor information
- Gray matter
- The exterior of the cerebrum and comprises the cerebral cortex and basal nuclei
- White matter
- Comprises the interior of the cerebrum
the cerebrum
• Gyri (ridges) and Sulci (grooves) of the neural cortex
• Increase surface area of the brain (and number of cortical neurons)
• Longitudinal fissure
• Separates the two cerebral hemispheres (right and left)
• Four Lobes
• Divisions of each hemispheres
Frontal - Parietal - Occipital – Temporal
Structures of the Cerebrum
- Central sulcus
- Divides frontal lobe from parietal lobe
- Lateral sulcus
- Divides frontal lobe from temporal lobe
- Parieto-occipital sulcus
- Divides parietal lobe from occipital lobe
Sulci of the Cerebrum
– Logic
– Analytical abilities
– Language
• Left brain specializations
– Creativity
– Spatial perception
• Right brain specializations
- Boundaries are not distinct
- Boundaries overlap
- One region may have several functions
- Certain functions cannot easily be assigned to a single region of the brain
• Correspondence between a specific function and a specific region of cerebral cortex is not precise
• Connections within one hemisphere:
• arcuate fibers:
– short fibers that connect one gyrus to another
• longitudinal fasciculi:
– longer bundles that connect frontal lobe to other lobes in same hemisphere
• Association fibers
- Bands of fibers connecting two hemispheres:
- corpus callosum
- anterior commissure
• Commissural fibers
• Link cerebral cortex with diencephalon, brain stem, cerebellum, and spinal cord
• Projection fibers
- Also called cerebral nuclei
* Are masses of gray matter that are embedded in white matter of cerebrum
The Basal Nuclei of the Cerebrum
- Caudate nucleus
- Globus pallidus
- Putamen
• Structures of Basal Nuclei
- The subconscious control of skeletal muscle tone
- The coordination of learned movement patterns (walking, lifting)
- Inhibit unwanted movements
- Selecting purposeful movements
- Postural support
• Functions of Basal Nuclei
separates motor and sensory areas of cerebrum
• Central sulcus
– is the surface of precentral gyrus of the frontal lobe
– Directs voluntary movements
• Pyramidal cells:
– are neurons of primary motor cortex
• Primary motor cortex:
– surface of postcentral gyrus
– receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)
• Primary sensory cortex:
- In the occipital lobe
* Information from sight receptors
• Visual cortex
- In the temporal lobe
* Information from sound receptors
• Auditory cortex
- In the temporal lobe
* Information from odor receptors
• Olfactory cortex
- In the frontal lobe
* Information from taste receptors
• Gustatory cortex
• are connected to sensory and motor regions of the cortex
• Function in:
– Interpreting incoming sensory information
– Coordinating motor responses
Association Areas of the Cerebrum
• Interprets input to primary sensory cortex (e.g., recognizes and responds to touch)
• Somatic sensory association area
• Coordinates motor responses (learned movements)
• Somatic motor association area (premotor cortex)
• Interprets activity in visual cortex
• Visual association area
• Monitors auditory cortex
• Auditory association area
- Part of the Premotor Cortex
- Controls learned eye movements
- Controls the ability to perform Saccadic Eye Movements or Saccades
• Frontal Eye Field
- Are located in lobes and cortical areas of both cerebral hemispheres
- Receive information from association areas
- Direct complex motor functions or analytical activities
Integrative Centers of the Cerebrum
- Located in the left hemisphere
- Receives information from all sensory association areas
- Functions in the ability to understand language or visual information
• General Interpretive Area ( Wernicke’s Area)
- Is also in left hemisphere and is associated with general interpretive (wernicke) area
- Coordinates all vocalization functions and the ability to construct speech
• Speech center (Brocca’s Area)
- Integrates information from all sensory association areas
* Performs abstract intellectual activities (e.g., predicting consequences of actions)
• Prefrontal cortex of frontal lobe
- Adjusts postural muscles
- Fine-tunes conscious and subconscious movements
- Structures of the cerebellum
- Folia
- Surface of cerebellum
- Highly folded neural cortex
- Anterior and posterior lobes
- Separated by primary fissure
- Cerebellar hemispheres:
- Separated at midline by the vermis
- Purkinje cells
- Large, branched cells
- Found in cerebellar cortex
- Receive input from up to 200,000 synapses
- Arbor vitae
- The internal white matter of cerebellum
- Contains cerebellar nuclei that relay information to Purkinje cells
• Functions of the Cerebellum
- Damage from trauma or stroke
- Intoxication (temporary impairment)
- Disturbs muscle coordination
ataxia (cerebellum)
- Integrates sensory information and motor commands
- Thalamus, epithalamus, and hypothalamus
- The pineal gland
- Found in posterior epithalamus
- Secretes hormone melatonin
The Diencephalon
- Filters ascending sensory information before it reaches the primary sensory cortex
- KNOWN AS THE RELAY STATION
- Relays information between basal nuclei and cerebral cortex
Diencephalon: The Thalamus
- Are masses of nuclei that form the thalamus
- Relay sensory information to basal nuclei and cerebral cortex
- FIVE groups of nuclei in total
- Anterior group
- Part of limbic system (emotions)
- Medial group
- Provides awareness of emotional states
- Ventral group
- Relays sensory information
- Posterior group
- Pulvinar nucleus (sensory)
- Lateral geniculate nucleus (visual)
- Medial geniculate nucleus (auditory)
- Lateral group
- Affects emotional states
- Integrates sensory information
• Thalamic nuclei
- Just posterior to the Mamillary bodies which:
- Infundibulum connects hypothalamus to pituitary gland
- Functions of the Hypothalamus
- Provides subconscious control of skeletal muscle
- Controls autonomic function
- Coordinates activities of nervous and endocrine systems
- Secretes hormones
- Produces emotions and behavioral drives
- Stimulates the feeding center (hunger)
- Stimulates the thirst center (thirst)
- Coordinates voluntary and autonomic functions
- Regulates body temperature
- Controls circadian rhythms (day–night cycles)
The Diencephalon: Hypothalamus
- Also known as the midbrain
- Start of the brainstem
- Consists of two parts
Mesencephalon
- Two pairs of sensory nuclei
- superior colliculus (visual)
- inferior colliculus (auditory)
• Tectum (roof of the midbrain)
- Red nucleus (subconcious control of upper limbs and muscle tone)
- Substantia nigra (regulates the basal nuclei)
• Tegmentum (floor of the midbrain)
- Allows communication between brain and spinal cord
- Coordinates and controls complex autonomic reflexes and visceral functions
- Consists of three groups of Nuclei
The Medulla Oblongata
• Reticular formation • Regulates autonomic functions • Reflex centers • Control peripheral systems: • cardiovascular centers: – cardiac center – control blood flow through peripheral tissues • respiratory rhythmicity centers – sets pace for respiratory movements
• Autonomic nuclei (2 types) The Medulla Oblongata)
• Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII)
• Sensory and motor nuclei of cranial nerves
- Links cerebellum with most other brain regions
- Contains the sensory and motor nuclei of cranial nerves V, VI, VII, VIII
- Nuclei involved with respiration
The Pons
- Process and relay information to and from cerebellum
* Ascending, descending, and transverse tracts
• Nuclei and tracts
olfactory nerve (I)
sensory (smell)
optic nerve (II)
sensory (vision)
oculomotor nerve (III)
motor (eye movements)
trochlear nerve (IV)
motor (eye movements)
abducens nerve (VI)
motor (eye movements)
trigeminal nerve (V)
mixed nerve (to the face) largest nerve in brain
facial nerve (VII)
mixed nerve (to the face) has 5 branches
Vestibulocochlear Nerves (VIII)
sensory
Glossopharyngeal Nerves (IX)
• Mixed (sensory and motor) to head and neck
Vagus Nerves (X)
• Mixed (sensory and motor)
Accessory Nerves (XI)
• Motor to muscles of neck and upper back
The Hypoglossal Nerves (XII)
• Motor (tongue movements)
