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List in order coverings of the brain from the brain tissue outward and their spaces.
Pia Mater, Subarachnoid Space (Contains blood vessels), Arachnoid Mater, Dura Mater (enclose the dural venous sinuses)
Define Pia Mater
Inner layer of meninges that covers the cerebral cortex outer surface. Loose fitting sleeve of pia mater covers the blood vessels as they penetrate the brain.
Define Subarachnoid Space
Space between the pia mater and the arachnoid mater that contains blood vessels.
Define Arachnoid Mater
Meninge layer that encloses the subarachnoid space and helps to protect the brain.
Define Dura Mater
The outermost layer of meninge that encloses the dural venous sinuses.
Describe the formation of Cerebrospinal Fluid (CSF)
The majority of production is from the choroid plexuses, networks of blood capillaries in the walls of the ventricles. Water from the blood plasma is filtered by the capillaries and then secreted by the ependymal cells to produce the CSF. This is bidirectional to continue production of CSF and to transport metabolites back to the blood.
Describe the circulation of Cerebrospinal Fluid
The CSF (formed in the lateral ventricles), flows into the 3rd ventricle (choroid plexus adds additional CSF) through two narrow openings called the interventricular foramina. It then flows through the aqueduct of he midbrain (cerebral aqueduct) into the 4th ventricle (adds additional CSF). The CSF then enters the suubarachnoid space through free openings at the roof of the 4th ventricle and circulates through the central canal of the spinal cord and in the subarachnoid space around the surface o the brain and spnal cord.
How is CSF different from plasma?
There is only 80 to 150 mL of CSF and much more plasma in the body. CSF protects the brain from chemical and physicsl injuries while plasma is used mainly for transportation of nutrients and blood. CSF is confined to the brain and spinal cord while plasma goes throughout the entire body. CSF does not contain platelets or red blood cells, but does contain some white blood cells like plasma.
What happens if more CSF is produced than can be reabsorbed?
A condition known as hydrocephalus will occur when CSF becomes built up. To fix the condition the extra CSF must be drained or a surgeon can create a hole in the bottom of the 3rd ventricle so the fluid can drain dirtectly into the spinal cord.
Discuss the supply of blood to the brain
- -Blood flows to brain mainly through internal carotid and vertebral arteries.
- -Dural venous sinuses drain blood into the internal jugular veins for return to the heart from the head.
- -Brief slowing of brain blood flow may cause disorientation or lack of consciousness.
- -1 to 2 mins of blood interruption impairs neuronal function.
- -4 mins of oxygen deprivation causes permanent injury.
- -If blood entering brain has low glucose concentration confusion, dizziness, convulsions, and lack of consciousness may occur.
Describe the role of the Blood-Brain Barrier
Prevents passage of harmful substances, but also helpful substances. This is important for making sure that the brain is protected from any unneeded or harmful substances.
What are the 3 major divisions of the brainstem?
- 1. Medulla Oblongata
- 2. Pons
- 3. Midbrain
What is the function of the Medulla Oblongata?
The white matter contains all of the sensory (ascending) tracts and motor (descending) tracts that extend between the spinal cord and other parts of the brain. Its nuclei contain the cardiovascular center which regulates the rate and force of the heartbeat, as well as the diameter of the blood vessels. Also contains the respiratory medullary rhythmicity area of the respiratory center which controls the basic rhythm of breathing. The medulla controls the reflexes for vomiting, swallowing, sneezing, coughing, and hiccuping. Contains nuclei that are associated with sensations of touch, pressure, vibration, and conscious proprioception. Also contains nuclei that are components of sensory pathways for taste, hearing, and balance.
What is the function of the Pons?
Bridge that connects the parts of the brain to one another. The ventral region of the pons plays an essential role in coordinating and maximizing the efficiency of voluntary motor output throughout the body. The dorsal region of the pons contains ascending and descending tracts as well as the nuclei of cranial nerves. Other nuclei found in the pons help control breathing.
What is the function of the Midbrain?
Connects the third ventricle above with the fourth ventricle below. Contains superior calliculi which serve as reflex centers for certain visual activities. The superior calliculi are also responsible for reflexes that govern movements of the head, eyes, and trunk in response due to visual stimuli. Inferior calliculi are responsible for the auditory pathway, and reflexes of sudden movements of the head, eyes, and trunk that occur when one is startled.
Describe the structure of the cerebellum.
Second in size to the cerebellum. Contains many folds to increase the surface area of it's gray matter allowing for a greater number of neurons. Deep groove known as the transverse fissure separates the cerebrum from the cerebellum. The cerebellum resembles a butterfly from superior or inferior views. The anterior and posterior lobe of the cerebellum govern subconscious aspects of skeletal muscle movements. The inferior surface contributes to equilibrium and balance.
Describe the function of the cerebellum.
The primary function is to elevate how well movements initiated by motor areas in the cerebrum are actually being carried out. The cerebellum also contributes to coordination of skilled movements, posture, and balance. The presence of reciprocal connections between the cerebellum and the cerebral cortex suggests that the cerebellum may have nonmotor functions such as cognition and language processing.
Describe the two major components of the diencephalon.
The thalamus and the hypothalamus
What is the function of the thalamus?
It is the major relay station for most sensory impulses that reach the primary sensory areas in the cerebral cortex from the spinal cord and brain stem. It also contributes to motor functions, relays nerve impulses between different areas of the cerebrum, and plays a role in the maintenance of consciousness.
What is the function of the hypothalamus?
It controls many body activities and is one of the major regulators of homeostasis. The hypothalamus is connected to vision, taste, smell, osmotic pressure, blood glucose level, certain hormone concentrations, and the temperature of blood. The hypothalamus also controls and integrates activities of the autonomic nervous system which regulates contraction of smooth muscle and cardiac muscles along with the secretions of many glands.
Describe the functions of the reticular activating system
- Ascending portion:
- The most important function is consciousness. The RAS is also active during arousal (when waking up), and it also helps to maintain attention and alertness. The RAS also prevents sensory overload by filtering out insignificant information.
- Descending portion:
- It helps to regulate muscle tone and also assists in regulation of the heartbeat, blood pressure, and respiratory rate.
Describe the cortex of the cerebrum
- Region of gray matter that forms the outer rim of the cerebrum (2-4mm thick)
- During embryonic development the gray matter of the cortex grows much faster than the deeper white matter.
Describe the convolutions of the cerebrum.
Cinvolutions are the folds formed in the cortex due to the faster growth of the gray matter than the white matter. These folds are also called gryus or plural gyri.
Describe the fissures of the cerebrum.
Fissures are the deepest grooves found between the folds in the cerebrum.
Describe the sulci of the cerebrum.
The sulci are known as the shallower grooves found between the folds in the cerebrum.
List (and locate) the lobes of the cerebrum. (5)
What is the function of the basal ganglia (a.k.a basal nuclei)?
Recieve input from the cerebral cortex. A major function of the basal nuclei is to help regulate initiation and termination of movements. The basal nuclei also control subconscious contractions of skeletal muscle. They also help initiate and terminate some cognitive processes such as attention, memory, and planning and may regulate emotional behaviors.
What is the function of the limbic system?
Plays a primary role in a range of emotions including pain, pleasure, docility, affection and anger. It is also involved in smell and memory.
What is the primary somatic area of the cerebral cortex?
It receives nerve impulses for touch, pressure, vibration, itch, tickle, temperature, and pain. It also allows you to pinpoint where the sensations originated.
What are the 12 pairs of cranial nerves and where to they Originate?
- 1. Olfactory Nerve (superior part of the nasal cavity)2. Optic Nerve (Axons of nerves are found in the retina of each eye)3. Oculomotor Nerve (Superior rectus muscle on upper part of eyeball, and inferior oblique muscle on bottom of eyeball)
- 4. Trochlear Nerve (Superior oblique muscle on top of eyeball) 5. Trigeminal Nerve (Cover many parts of face including eyes, ears, nose, and teeth)
- a. ophthalmic
- b. maxillary
- c. mandibular
- 6. Abducens Nerve (Lateral rectus muscle of eyeball) 7. Facial Nerve (Sides of teh face, salivary glands, and nasal passage leading to throat)8. Vestibulocochlear Nerve (vestibule and cochlea in ear)
- 9. Glossopharyngeal Nerve (parotid gland, soft palate, tongue, palatine tonsil, carotid body, carotid sinus) 10. Vagus Nerve (back of throat and all major organs)
- 11. Accessory Nerve (trapezius muscle and stemocleidomastoid muscle on side of neck) 12. Hypoglossal Nerve (tongue and lower jaw muscles)
What is the function of the olfactory nerve?
Used for the sense of smell (sensory nerve only)
What is the function of the optic nerve?
Conducts nerve impulses for vision (sensory nerve only)
What is the function of the oculomotor nerve?
Movement of eyelid / blinking
What is the function of the trochlear nerver?
Controls movement of the eyeball.
What is the function of the trigeminal nerve?
Sensory axons control nerve impulses for touch, pain, and thermal sensations. The motor nerve impulses control mainly the chewing movements.
What is the function of the abducens nerve?
Lateral rotation of the eyeball.
What is the function of the facial nerve?
Sensory neurons control taste, touch, pain, and thermal sensations. The motor neurons control contraction of the facial muscles to allow expression.
What is the function of the vestibulocochlear nerve?
Controls hearing and equilibrium.
What is the function of the glossopharyngeal nerve?
Sensory nerve impulses control taste, swallowing, blood pressure,touch, pain, and thermal sensations. The motor nerve impulses control swallowing and secretion of saliva.
What is the function of the vagus nerve?
Sensory axons control taste, touch, pain, muscles of neck and throat, thermal sensations and in organs they control hunger, fullness, and discomfort. The motor axons are involved in swallowing, vocalizing, and coughing.
What is the function of the accessory nerve?
The motor axons coordinate movement of the head.
What is the function of the hypoglossal nerve?
Motor axons are used in speech and swallowing.