A&P I: Unit 3: Module 6.2: CNS (Brain)
Identify the general location and the type of matter for the structures below:
-(1) Cerebellar Cortex: Layer of Gray Matter on surface. -(2) Arbor Vitae: Deeper layer of white matter. ("Tree of Life") -(3) Cerebellar Nuclei: Deep clusters of gray matter.
Medulla Oblongata
-(a) Most inferior and is continuous above with the pons and below with the spinal cord. The Medulla houses essential ascending and descending nerve tracts as well as brain stem nuclei. -(1) Pyramids: The anterior surface has swellings called pyramids. -(b) Decussate: The descending motor tracts cross over (decussate) from right to left side at the pyramids.
What is the function of the arachnoid villi?
-(granulations) that are part of the arachnoid mater are knob-like structures with capillaries that function in the absorption of CSF. Notice they project into the superior sagittal sinus.
What information do the large and small regions on the somatosensory homunculus communicate?
-Areas that have a larger number of sensory receptors (and so are more sensitive) have a larger representation. For example, the lips which are very sensitive are shown larger than the elbows.
What information do the large and small regions on the motor homunculus communicate?
-Areas that have more neurons that serve that area (and so allow for fine controlled movements), are larger. For example, notice the hands which can thread a needle are shown larger than the elbows which only have gross motor movements.
Cortex
-At the surface of the brain, gray matter is called cortex ("Bark on a Tree")
What 2 organs compose the CNS?
-Brain -Spinal Cord
Label the structures of the brainstem on the following brain cross-section.
-Brainstem -Medulla Oblongata -Pons -Midbrain
The subarachnoid space is filled with ________________ and contains large ________________.
-CSF; blood vessels that supply the neural tissue.
Label the following parts of the cerebellum: cerebellar cortex, arbor vitae, and cerebellar nuclei.
-Cerebellar Cortex -Arbor Vitae -Cerebellar Nuclei
Regions of the brain stem send fibers to the......
-Cerebellum through the cerebellar peduncles, which arun throughout the entire brainstem.
What are the structures of the cerebrum?
-Cerebral hemispheres -Fissures
What are the 4 major regions of the brain?
-Cerebrum -Diencephalon -Cerebellum -Brainstem
CNS Protection: Meninges
-Connective tissue membranes that cover the brain and spinal cord.
What is the function of the middle cerebellar Peduncles?
-Connects the Cerebellum to the brain stem and is involved with somatic and visceral motor control. -Smoothes out the basic rhythm of breathing set by the Medulla Oblongata (that is, the pace and depth of breathing, such as after walking upstairs)
Region of White Matter: Corpus Callosum
-Connects the two cerebral hemispheres to allow them to communicate with each other.
Which Ventricle is located in the Pons?
-Contains the 4th Ventricle
What is the Cerebral Aquaduct of the Midbrain?
-Contains the cerebral aquaduct which connects the 3rd and 4th ventricles.
What are the functions of the cerebrum?
-Controlling all voluntary movements -Processing all sensory info. (Such as visual, hearing, gustatory, olfactory, and balance) -Consciousness -Memory -Decision-making -Personality
What is White Matter composed of?
-Corpus Callosum -Internal Capsule -Septum Pellucidum -Made of myelinated axons. White matter in brain occurs deep within.
List the specific areas of gray and white matter in the image below.
-Cortex -Cerebral Nuclei -"inner" white matter -Corpus Callosum -Septum Pellucidum -Internal Capsule
What is Gray matter composed of?
-Cortex -Cerebral Nuclei -Cell Bodies, Dendrites, & Unmyelinated axons
What are fissures?
-Deep grooves that are associated with the cerebrum; F: They separate different regions of the brain.
Cerebral Nuclei
-Deep within the brain, the neuron cell bodies of the gray matter occur in clusters called cerebral nuclei (or just nuclei for short), each of which carries out specific functions.
Lobes of the cerebral cortex
-Deeper sulci divide the cerebral hemispheres into five different lobes. Four of the lobes are named for the skull bones overlying them. The 5th lobe (the insula) is deep to the temporal, parietal, and frontal lobes.
Label the following picture of the brain with the 4 regions.
-Diencephalon -Brain Stem -Cerebellum -Cerebrum
Label the layers of the Meninges in the following pictures:
-Dura Mater -Arachnoid Mater -Pia Mater
What are the layers of the Meninges?
-Dura Mater -Arachnoid Mater -Pia Mater
Additional Structures Associated with the Dura Mater:
-Epidural Space: Space above the dura mater. In the brain, contains blood vessels that nourish the meninges and bones of the cranium. -Subdural Space: Space below the Dura Mater.
General Functions of the Parietal Lobe
-Evaluates shape and texture of objects being touched.
What 2 regions does the Pons link?
-Forms a link between the Brain Stem and the Cerebellum, which is how it derives its name.
It is important to know where each of the lobes are located on the cerebrum. Label the following pictures with the 5 lobes of the cerebrum.
-Frontal -Parietal -Temporal -Occipital -Insula
Blood Brain Barrier (BBB):
-Function: System of capillaries that controls which substances pass from the bloodstream into the nervous tissue in the brain so that the brain is not exposed to toxins or bacteria, but yet gets the nutrients the cell needs to survive.
What are the 4 bumps on the dorsal surface of the midbrain called? What are their functions?
-Has 4 bumps on dorsal surface that form the corpora quadrigemina. The 2 superior bumps are called the superior colliculi and the 2 bottom bumps which are called the inferior colliculi. -Functions: —Superior Colliculi: are involved in visual reflexes, such as tracking moving objects and blinking. Located in the midbrain. —Inferior Colliculi: relay impulses from the receptors for heating in the ear to the thalamus. Also involved in auditory reflexes, such as turning head towards loud sounds in the environment.
The Midbrain contains two cerebral peduncles, which information do these carry?
-Has two paired cerebral peduncles (motor tracts that carry voluntary motor commands).
General Functions of the Temporal Lobe
-Hearing -Interpreting speech and language -Smell
Label the structures of the Diencephalon on the following brain cross-section.
-Hypothalamus -Subthalamus -Thalamus -Epithalamus
What is the primary purpose or function of the gyri and sulci?
-Increase the surface area of the brain to fit all of the neurons required for the cerebrum to function.
Meninges: Pia Mater
-Innermost meninge, covers contours of brain, forms choroid plexus in the ventricular system. ("Pia" means delicate) -Adheres to the surface of the brain. -Structure (what tissue is it composed of?): Impermeable and is composed of areolar connective tissue. -Function: It contains a rich supply of blood vessels that nourish the brain. Notice how it clings tightly to the gyri and sulci of the brain. By containing the CSF, it helps to protect and cushion the brain.
What is the Cerebellar Peduncle?
-Is a nerve tract that allows communication between the cerebellum and the brain stem. All messages sent and received by the cerebellum run on these fibers.
What are the 4 primary functions of the Brain Stem?
-It acts as a passageway for all fibers running between the cerebrum and spinal cord. -It is important in the Innervation of the face and head; 10 of the 12 cranial nerves (CN) attach to the brain stem. -It produces ridgidly programmed, automatic behaviors necessary for survival. -It is a major site for integration of auditory and visual reflexes.
Where is the white matter located in the cerebrum?
-It is deep to the gray matter. The white matter is composed primarily of myelinated axons and so links different regions together, sending info from one region of the brain to another or to and from the spinal cord.
Functions of the Cerebellum:
-It smoothes and coordinates body movements and helps maintain equilibrium and posture. It does this by..... -Motor Cortex sends info to the cerebellum regarding the movements being planned. -Cerebellum compares the planned movement to what is actually happening with the body, info from receptors in the inner ear and proprioceptors in the trunk and limbs. -If there are differences between what is planned and what is occurring, the cerebellum sends info to the cortex on how to correct these differences. (Stores motor (procedural) memory (learned motor skills); the saying "you never forget how to ride a bike" is true because "know how" is stored in the cerebellum).
Thalamus
-Largest part of the Diencephalon -Location: Found on either side of the third ventricle -Structure: Is made of large paired, oval structures; consisted of two masses of Gray Matter organized into 12 nuclei. -Function: Main relay center for all sensory impulses ascending to the cerebral cortex, except olfactory sensations (screens out insignificant signals and routes important ones to appropriate areas on the somatosensory cortex and other areas of the brain. -It is called the gateway to the cerebral cortex
Label the following parts of the ventricles:
-Lateral Ventricles -Third Ventricle -Fourth Ventricle -Intervertebral Foramen -Septum Pellucidum -Lateral Apertures -Medial Apertures -Cerebral Aquaduct
Periosteal Layer of the Dura Mater: Meningeal Layer of the Dura Mater:
-Lines the Skull. -Adheres to the periosteal layer -These two layers are fused except at the Dural Venous Sinuses. (Blood filled spaces that drain blood from the brain)
On what specific gyrus is the primary somatosensory cortex located?
-Located along the postcentral gyrus do the parietal lobe.
Sensory Area: Gustatory Cortex
-Location (Lobe): Insula Lobe -Receives info from: Tongue
Sensory Area: Visual Cortex
-Location (Lobe): Occipital Lobe -Receives info from: Retina
Sensory Area: Primary Somatosensory
-Location (Lobe): Parietal Lobe -Receives info from: general somatic senses. (Touch, temperature, pressure, etc.)
Sensory Area: Auditory Cortex
-Location (Lobe): Temporal Lobe -Receives info from: Ears
Third Ventrical
-Location: Between the Cerebral hemispheres in the Diencephalon, around the thalamus. -The interventricular foremen is an opening between the lateral ventricles that allows the lateral ventricles to communicate with the 3rd ventricle. (Joined by the interventricular foremen that allows fluid to move between the lateral ventricles and the third ventricle).
Cerebellum ("Little Brain"):
-Location: Dorsal to the Pons and Medulla Oblongata. -Structure: Has two cerebellar hemispheres connected medially by a thin vertical structure called the vermis ("worm-like")
Epithalamus
-Location: Dorsal to the thalamus and part of the "roof" of the Diencephalon. -Structure: made of one small group of nuclei and a cone-shaped gland called the pineal gland. -Function: secretes the hormone melatonin -Functions of this hormone: promotes sleep; helps set the body's biological clock; may be involved in mood and timing the onset of puberty.
Cerebral Spinal Fluid (CSF):
-Location: Is a watery fluid that fills the subarachnoid space as well as the ventricles in the brain and spinal cord.
Motor Areas of the Cerebral Cortex
-Location: Located anterior to the central sulcus. Each cerebral hemisphere contains a primary motor cortex and motor association area (premotor cortex) -Function: The motor areas initiate a motor response, which is used to direct the movement of skeletal muscles.
Pons:
-Location: The Pons ("The Bridge") is located between the Medulla Oblongata and midbrain.
Association Areas of the Cerebral Cortex
-Location: throughout the Cortex (Parietal, Occipital, Temporal, and Frontal) -Function: Sensory info is passed to the adjacent association areas which integrate sensory info into perception. Perception is the brains interpretation of sensory stimuli.
Region of White Matter: Internal Capsule
-Made of ascending tracts that pass sensory info from the spinal cord to the brain and descending tracts that pass motor info from brain to spinal cord.
What are the 3 regions of the Brain Stem?
-Midbrain -Pons -Medulla Oblongata
Meninges: Arachnoid Mater
-Middle Layer; "arachnoid" means spider. The elastic fibers look like a spider web. -Structure: Made of delicate web of elastic and collagen fibers. -Subarachnoid Space: The Space below the arachnoid mater, the subarachnoid space, is full of weblike threads that connect the arachnoid mater to the Pia Mater.
Where is the Cerebrum located?
-Most Rostral part of the brain. -It covers the diencephalon and the brainstem (similar to a mushroom cap covering the stalk)
CNS Protection:
-Nervous Tissue is a delicate tissue. Neurons don't miotically divide. Therefore, if neurons are destroyed they cannot replace themselves. Thus, in addition to the skull, several structures function to protect the brain.
What are examples of substances that can get through the blood brain barrier?
-Only gases, ions, viruses, and a few lipid soluble substances such as nicotine, anesthetics, and alcohol can pass through to reach the neurons without using a special transport mechanism.
Meninges: Dura Mater
-Outermost meninge, has 4 folds, lines periosteum of skull. -Toughest layer (Dura mean Hard and Mater means mother) -Structure: Made of dense irregular tissue and has two layers. -Function: gives structural support to the dural venous sinuses and carries blood from the brain to the heart.
Hypothalamus
-Part of the Diencephalon -Involved in Homeostasis -Location: Inferior portion of the Diencephalon on the ventral surface (underside) of the brain. -Structure: Made of various nuclei -Functions: Controls the ANS; Regulates body temperature; regulates hunger and thirst sensations; regulates rage, pleasure, aggression, and sex drive; regulates sleep-wake cycles; involved in formation of memory; makes at least 9 hormones.
Corpus Callosum:
-Part of the brain that allows communication between the two hemispheres of the brain. -Responsible for transmitting neural messages between both the right and left hemispheres.
On what specific gyrus is the primary motor cortex located?
-Part of the motor area that brings about precise voluntary movements of the body (especially fingers, forearms, and facial muscles). It is located along the precentral gyrus.
General Functions of the Occipital Lobe
-Processes incoming visual information -Stores Visual Memories
What is the general function of the CNS?
-Responsible for an individuals behavior, personality, and intellect.
2 New directional terms associated with CNS:
-Rostral -Caudal
Sensory Areas of Cerebral Cortex
-Sensory areas are located posterior to the central sulcus. The arrival of sensory info to the cortex results in the awareness of the sensation.
Functions of the Meninges:
-Separate the soft tissue of the brain from the bones of the cranium and the vertebrae. -Enclose and protect blood vessels that supply the brain. -Contain and circulate CSF. -Some parts of the meninges that surround the brain from veins called dural venous sinuses that drain blood from the brain.
Which Cranial Nerves attach to the Midbrain?
-Serves as attachments for the cranial nerves III & IV
What are Sulci?
-Shallow Grooves (singular: Sulcus)
At two places, the layers of the dura mater are not fused and the dura mater dips down into the brain to form the ________________ between the right and left hemispheres and the ________________ between the occipital cortex and the cerebellum.
-Sheets called the falx cerebri; Tentorium Cerebelli
Internal Capsule:
-Situated in the inferomedial part of each cerebral hemisphere of the brain. -It carries info past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus.
Midbrain (AKA Mesencephalon)
-Structure: The midbrain is the most Rostral part of the brain stem.
Choroid Plexus:
-Structures that produce CSF -(a) The capillaries in the walls of the ventricles. -(b) Ependymal Cells (neuroglial cells) of the ventricles.
What are Gyri?
-The "wrinkled" surface is due to elevated ridges called gyri (singular: gyrus)
Functions of the Medulla Oblongata:
-The Medulla Oblongata contains several autonomic nuclei which regulate vital functions for life. -(1) Respiratory Center: Helps to control depth and rate of breathing. -(2) Cardiac Center: Adjusts the force and rate of the heartbeat. -(3) Vasomotor Center: Regulates Blood Pressure by controlling the contraction of the smooth muscle in the wall of the blood vessels, causing them to either constrict or dilate. -(4) The Centers for What Other Activities are Located Here? The medulla also has centers that regulate reflexes such as coughing, sneezing, hiccuping, vomiting, and swallowing.
2 Lateral Ventricles
-The largest ventricles (first and second ventricles); Located within the cerebral hemispheres -Each C-Shaped -Separated by the Septum Pellucidum
What is unique about the lateral surface of the medulla?
-The lateral surface has swellings called the olives that relay sensory information. (Especially about proprioception) to the cerebellum.
Cerebral Cortex:
-The outer 2-4mm thick layer of gray matter in the cerebrum. -It makes up 40% of the mass of the brain because the gyri and sulci triple its surface area.
Additional info on Primary Somatosensory Cortex and Primary Motor Cortex
-The somatosensory and Primary cortices (cortices=plural of cortex) have been mapped to the cerebrum. The maps are called the somatosensory homunculus and motor homunculus, respectively. Each homunculus shows the specific region of the post central gyrus (for the somatosensory cortex) or precentral gyrus (for the motor cortex) that is associated with a specific part of the body
Fourth Ventricle
-The ventricle located between the cerebellum and the dorsal pons, in the center of the metencephalon. -Within the medulla, it narrows and becomes continuous with the central canal of the spinal cord. -Contains 3 openings (2 lateral and 1 median aperture): connect the 4th ventricle to the subarachnoid space (A fluid filled space surrounding the brain and spinal cord.)
What Cranial Nerves attach to the Medulla?
-There are attachment sites for Cranial Nerves VIII-XII
What are the Ventricles?
-They are cavities (spaces) in the brain. -The ventricles are connected to one another as well as the subarachnoid space and the central canal of the spinal cord.
Region of White Matter: Septum Pellucidum (Has both white and gray matter)
-Thin medial partition that separates the two lateral ventricles (spaces in the brain).
Region of White Matter: Fornix
-Thin tract of white matter that connects the hippocampus (an area of the brain involved w/ learning and memory) to other diencephalon structures.
General Functions of the Insula Lobe
-This lobe is located under the temporal lobe -Memory -Interpretation of taste
Rostral:
-Toward the nose/forehead (Synonomous with Anterior)
Caudal:
-Toward the tail (cord) (synonymous with posterior)
2 major fissures of the brain?
-Transverse Fissure: Separates cerebral hemispheres from the cerebellum. -Longitudinal Fissure: Separates the right and left hemispheres from one another.
Which Cranial Nerves Attach to the Pons?
-V-VIII
General Functions of the Frontal Lobe
-Voluntary motor function -Concentration -Verbal Communication -Decesion making -Planning -Personality
Describe the flow of CSF through the brain and spinal cord:
-a) CSF is produced by the choroid plexus of each ventricle. -b) CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. -c) CSF flows through the subarachnoid space. -d) CSF is absorbed into the dural venous sinuses via the arachnoid granulations.
Structures that make up the Blood Brain Barrier:
-a) Capillaries with tight junctions between the adjacent simple squamous cells (Called Endothelial Cells) that make up the capillary. -b) The basement membrane around the capillary. -c) The perivascular feet of astrocytes that cover and wrap around the basement membrane and capillaries in the brain.
Which parts of the brain do not have a blood brain barrier?
-a) Choroid Plexuses (as they need to make CSF by filtering blood) -b) Hypothalamus (makes hormones that must enter the blood stream to circulate) -c) Pineal Gland (makes the hormone melatonin which must enter the blood stream)
Functions of CSF:
-a) The brain and spinal cord float in the CSF, which cushions them from hard blows and sudden jolts. -b) The CSF also provides nutrients to the brain and spinal cord and helps remove wastes produced by neurons. -c) The CSF carries chemical signals (for example, hormones) between various parts of the CNS.
What fluid fills the ventricles?
-cerebrospinal fluid
Septum Pellucidum (Translucent Wall)
-is a thin, triangular, vertical double membrane separating the anterior horns of the left and right lateral ventricles of the brain. -It runs as a sheet from the corpus Callosum down to the Fornix.
