What is the spinal cord's white matter composed of?
External white matter composed of myelinated fiber tracts
Describe the ventricles of the brain
Like a canal system:
Connected to one another and to the central canal of the spinal cord
Lined by ependymal cells, filled with CSF
Two C-shaped lateral ventricles in the cerebral hemispheres
Third ventricle in the diencephalon
Fourth ventricle in the hindbrain, dorsal to the pons, develops from the lumen of the neural tube
Describe the general categories of surface markings of the cerebral hemispheres.
Ridges (gyri; singular gyrus), shallow indentations (sulci; singular sulcus), and deep grooves (fissures)
Name the five lobes of the cerebral hemispheres/
What is the name of the fissure which separates the cerebrum and the cerebellum?
Transverse cerebral fissure
Where is the central sulcus located?
Separates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe
Describe the cerebral cortex.
Thin (2-4 mm) superficial layer of gray matter
40% of the mass of the brain
Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding
Each hemisphere connects to contralateral side of the body
There is lateralization of cortical function in the hemispheres
All the neurons are INTERNEURONS - no axons to be found!
List the three types of functional areas in the cerebral cortex.
Motor areas—control voluntary movement
Sensory areas—conscious awareness of sensation
Association areas—integrate diverse information (retrieving and deciphering information)
[Conscious behavior involves the entire cortex]
What are the four MOTOR areas of the cerebral cortex
Primary (somatic) motor cortex (skeletal muscle, skin, joints) - located in precentral gyrus
Premotor cortex - muscle memory for fine skills
Broca's area - a motor speech area that directs muscles of the tongue (active as one prepares to speak)
Frontal eye field - controls voluntary eye movements
See slide image for locations.
What are motor homunculi?
Upside-down caricatures representing the motor innervation of body regions
List the main SENSORY areas of the cerebral cortex.
Primary somatosensory cortex
Somatosensory association cortex
Visceral sensory area
What is the location and function of the the primary somatosensory cortex?
Located in the postcentral gyri of the cerbral cortex
Receives sensory information from the skin, skeletal muscles, and joints
Capable of spatial discrimination: identification of body region being stimulated
What is the location and function of the the somatosensory association cortex?
Posterior to the primary somatosensory cortex
Integrates sensory input from primary somatosensory cortex
Determines size, texture, and relationship of parts of objects being felt
Example: finding a quarter by feel in pocket or purse
What is the location and function of the the primary visual area of the cerebral cortex?
Extreme posterior tip of the occipital lobe
Most of it is buried in the calcarine sulcus
Receives visual information from the retinas
Visual memories are stored next door in the visual association area (complex processing involves entire posterior half of the hemispheres)
What is the location and function of the the primary auditory area of the cerebral cortex?
Superior margin of the temporal lobes
Interprets information from inner ear as pitch, loudness, and location
The auditory association area is located posterior to the primary auditory cortex, and stores memories of sounds and permits perception of sounds
What is the location and function of the olfactory cortex?
Medial aspect of temporal lobes (in piriform lobes)
Part of the primitive rhinencephalon, along with the olfactory bulbs and tracts
(Remainder of the rhinencephalon in humans is part of the limbic system)
Region of conscious awareness of odors
What is the location and function of the gustatory cortex?
In the insula
Involved in the perception of taste
What is the location and function of the the visceral sensory area of the cerebral cortex?
Posterior to gustatory cortex
Conscious perception of visceral sensations, e.g., upset stomach or full bladder
What is the location and function of the vestibular cortex?
Posterior part of the insula and adjacent parietal cortex
Responsible for conscious awareness of balance (position of the head in space)
Describe the diencephalon
Three paired structures
Encloses the third ventricle
Below the Corpus callosum
Describe the thalamus
80% of diencephalon
Superolateral walls of the third ventricle
Connected by the interthalamic adhesion (intermediate mass)
Contains several nuclei (clusters of neural cell bodies), named for their location
Nuclei project and receive fibers from the cerebral cortex
List some functions of the thalamus
Gateway to the cerebral cortex ("relay station" or "pit stop")
Sorts, edits, and relays information
Afferent impulses from all senses and all parts of the body
Impulses from the hypothalamus for regulation of emotion and visceral function
Impulses from the cerebellum and basal nuclei to help direct the motor cortices
Mediates sensation, motor activities, cortical arousal, learning, and memory
Describe the hypothalamus
Forms the inferolateral walls of the third ventricle
Contains many nuclei
Example: mammillary bodies
Paired anterior nuclei
Olfactory relay stations
Infundibulum—stalk that connects to the pituitary gland
List some functions of the hypothalamus
Autonomic control center for many visceral functions (e.g., blood pressure, rate and force of heartbeat, digestive tract motility)
Center for emotional response: Involved in perception of pleasure, fear, and rage and in biological rhythms and drives
Regulates body temperature, food intake, water balance, and thirst
Regulates sleep and the sleep cycle
Controls release of hormones by the anterior pituitary
Produces posterior pituitary hormones
Describe the epithalamus and its glands
Most dorsal portion of the diencephalon; forms roof of the third ventricle
Pineal gland—extends from the posterior border and secretes melatonin
Melatonin—helps regulate sleep-wake cycles
Describe the brain stem/
Similar structure to spinal cord but contains embedded nuclei
Controls automatic behaviors necessary for survival
Contains fiber tracts connecting higher and lower neural centers
Associated with 10 of the 12 pairs of cranial nerves
Describe the midbrain.
Located between the diencephalon and the pons
Contain pyramidal motor tracts
Channel between third and fourth ventricles
List some of the midbrain nuclei.
Nuclei that control cranial nerves III (oculomotor) and IV (trochlear)
Corpora quadrigemina—domelike dorsal protrusions
Superior colliculi—visual reflex centers
Inferior colliculi—auditory relay centers
Substantia nigra—functionally linked to basal nuclei
Red nucleus—relay nuclei for some descending motor pathways and part of reticular formation
Describe the pons.
Forms part of the anterior wall of the fourth ventricle
Fibers of the pons connect higher brain centers and the spinal cord and relay impulses between the motor cortex and the cerebellum
Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial)
Some nuclei of the reticular formation
Nuclei that help maintain normal rhythm of breathing
List some of the centers of the medulla oblangata and what they control.
Autonomic reflex centers
Cardiac center adjusts force and rate of heart contraction
Vasomotor center adjusts blood vessel diameter for blood pressure regulation
Generate respiratory rhythm
Control rate and depth of breathing, with pontine centers
Additional centers regulate
Describe the cerebellum.
11% of brain mass
Dorsal to the pons and medulla
Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction
Describe the anatomical parts of the cerebellum.
Two hemispheres connected by vermis
Each hemisphere has three lobes
Anterior, posterior, and flocculonodular
Folia—transversely oriented gyri
Arbor vitae—distinctive treelike pattern of the cerebellar white matter
List function of the cerebellum.
Cerebellum receives impulses from the cerebral cortex of the intent to initiate voluntary muscle contraction
Signals from proprioceptors and visual and equilibrium pathways continuously "inform" the cerebellum of the body's position and momentum
Cerebellar cortex calculates the best way to smoothly coordinate a muscle contraction
A "blueprint" of coordinated movement is sent to the cerebral motor cortex and to brain stem nuclei
Recognizes and predicts sequences of events during complex movements
Plays a role in nonmotor functions such as word association and puzzle solving
What does the limbic system control?
Memories and emotions associated with them.
Emotional responses to stimuli.
What does the reticular formation control?
Connects conscious and subconscious sensory stimuli.
Filters out repetitive and weak stimuli (~99% of all stimuli!)
Severe injury results in permanent unconsciousness (coma)
Describe the meninges.
Cover and protect the CNS
Protect blood vessels and enclose venous sinuses
Contain cerebrospinal fluid (CSF)
Form partitions in the skull
Describe the dura mater.
Two layers of fibrous connective tissue (around the brain) separate to form dural sinuses
What are the three dural septa and what do they do?
Dural septa limit excessive movement of the brain
Falx cerebri—in the longitudinal fissure; attached to crista galli
Falx cerebelli—along the vermis of the cerebellum
Tentorium cerebelli—horizontal dural fold over cerebellum and in the transverse fissure
Describer the arachnoid mater.
Middle layer with weblike extensions
Separated from the dura mater by the subdural space
Subarachnoid space contains CSF and blood vessels
Arachnoid villi protrude into the superior sagittal sinus and permit CSF reabsorption (draining into dural venous sinuses)
Describe the pia mater.
Layer of delicate vascularized connective tissue that clings tightly to the brain
Describe the composition of Cerebrospinal Fluid (CSF).
Less protein and different ion concentrations than plasma
Made up of: glucose, oxygen, vitamins and ions.
What are functions of CSF?
Gives buoyancy to the CNS organs
Protects the CNS from blows and other trauma
Nourishes the brain and carries chemical signals
Describe the location and function of Choroid Plexuses.
Produce CSF at a constant rate
Hang from the roof of each ventricle
Clusters of capillaries enclosed by pia mater and a layer of ependymal cells
Ependymal cells use ion pumps to control the composition of the CSF and help cleanse CSF by removing wastes
Describe the location of the spinal cord.
Begins at the foramen magnum
Ends as conus medullaris at L1 vertebra
Describe the function of the spinal cord.
Provides two-way communication to and from the brain
Contains spinal reflex centers
What protects the spinal cord?
Bone, meninges, and CSF
Cushion of fat and a network of veins in the epidural space between the vertebrae and spinal dura mater
CSF in subarachnoid space
What are filum terminale?
Fibrous extension from conus medullaris; anchors the spinal cord to the coccyx
What are the two lengthwise grooves which divide the spinal cord into right and left halves?
Ventral (anterior) median fissure
Dorsal (posterior) median sulcus
Consists mostly of ascending (sensory) and descending (motor) tracts
Transverse tracts (commissural fibers) cross from one side to the other
Tracts are located in three white columns (funiculi on each side—dorsal (posterior), lateral, and ventral (anterior)
Each spinal tract is composed of axons with similar functions