Chapter 14 Flashcards
What are the four major parts of the brain?
- Brainstem
- Cerebellum
- Diencephalon
- Cerebrum
What are the three cranial meninges? What makes them different from the spinal meninges?
- Dura mater - has two layers unlike the spinal dura mater which only has one. The two layers are the periosteal layer (which is external) and the meningeal layer (which is internal)
- Archnoid mater
- Pia mater
What are the three extensions of dura mater that seperate parts of the brain? What do they separate?
- Falx cerebri: separates the two hemispheres (sides) of the cerebrum.
- Falx cerebelli: separates the two hemispheres of the cerebellum.
- Tentorium cerebelli: separates the cerebrum from the cerebellum.
Blood flows to the brain mainly via the ______ and the ______; the dural venous sinuses drain into the ______ to return blood from the head to the heart.
Internal carotid; vertebral arteries; internal jugular veins
In an adult, the brain represents only __% of total body weight, but it consumes about __% of the oxygen and glucose used by the body, even when you are resting.
2; 20
Typically, an interruption in blood flow for __ minutes impairs neuronal function, and total deprivation of oxygen for about __ minutes causes permanent injury. Because virtually no glucose is stored in the brain, the supply of glucose also must be ______.
1-2; 4; continuous
Blood-brain barrier
Consists mainly of tight junctions that seal together the endothelial cells of brain blood capillaries and a thick basement membrane that surrounds the capillaries. Allows certain substances in blood to enter brain tissue and prevents passage to others.
Cerebrospinal fluid (CSF)
A clear, colorless liquid composed primarily of water that protects the brain and spinal cord from chemical and physical injuries. It also carries small amounts of oxygen, glucose, and other needed chemicals from the blood to neurons and neuroglia.
What are the three basic functions of the CSF in maintaining homeostasis?
- Mechanical protection
- Chemical protection
- Circulation
Ventricles
Four CSF-filled cavities within the brain.
What are the four ventricles?
Lateral ventricle: one in each hemisphere of the cerebrum.
Third ventricle: lies between the right and left halves of the thalamus.
Fourth ventricle: lies between the brainstem and the cerebellum.
Septum pellucidum
A thin membrane that separates the lateral ventricles.
Choroid plexuses
Networks of blood capillaries in the walls of the ventricles, where the majority of CSF is produced.
Blood-cerebrospinal fluid barrier
Permits certain substances to enter the CSF but excludes others, protecting the brain and spinal cord from potentially harmful blood-borne substances. Is formed by tight junctions of ependymal cells.
The CSF formed in the choroid plexuses of each lateral ventricle flows into the third ventricle through two narrow, oval openings, the ______. More CSF is added by the choroid plexus in the roof of the third ventricle. The fluid then flows through the ______, which passes through the midbrain, into the fourth ventricle. The choroid plexus of the fourth ventricle contributes more fluid. CSF enters the subarachnoid space through three openings in the roof of the fourth ventricle: a single ______ and paired ______, one on each side. CSF then circulates in the central canal of the spinal cord and in the subarachnoid space around the surface of the brain and spinal cord.
Interventricular foramina; aqueduct of the midbrain (cerebral aqueduct); median aperture; lateral apertures
CSF is gradually reabsorbed into the blood through ______, fingerlike extensions of the arachnoid mater that project into the dural venous sinuses, especially the ______. Normally, CSF is reabsorbed as rapidly as it is formed by the choroid plexuses, at a rate of about 20 mL/hr (480 mL/day). Because the rates of formation and reabsorption are the same, the pressure of CSF normally is constant. For the same reason, the volume of CSF remains constant.
Arachnoid villi; superior sagittal sinus
Arachnoid granulation
A cluster of arachnoid villi.
What are the three components of the brainstem?
- Medulla oblongata
- Pons
- Midbrain
Medulla oblongata
AKA medulla; begins at the foramen magnum and extends to the inferior border of the pons. Contains sensory (ascending) and motor (descending) tracts. Also contain nuclei that coordinate vomiting, swallowing, sneezing, coughing, and hiccupping.
Pyramids
Protrusions formed by the large corticospinal tracts that pass from the cerebrum to the spinal cord. The corticospinal tracts control voluntary movements of the limbs and trunk.
Decussation of pyramids
Crossing of axons in the pyramids. Explains why each side of the brain controls voluntary movements on the opposite side of the body.
Cardiovascular (CV) center
Regulates heartbeat and blood vessel diameter.
Medullary respiratory center
Together with pons, regulates breathing.
Vomiting center
Causes vomiting, the forcible expulsion of the contents of the upper gastrointestinal (GI) tract through the mouth.
Deglutition center
Promotes deglutition (swallowing) of a mass of food that has moved from the oral cavity of the mouth into the pharynx (throat).
Olive
Oval-shaped swelling lateral to each pyramid.
Inferior olivary nucleus
Provides instructions that the cerebellum uses to adjust muscle activity when learning new motor skills.
What five nuclei in the medulla oblongata are components of sensory pathways to the brain?
- Gracile nucleus
- Cuneate nucleus
- Gustatory nucleus
- Cochlear nuclei
- Vestibular nuclei
What two nuclei in the medulla oblongata are associated with sensations of touch, pressure, vibration, and conscious proprioception?
- Gracile nucleus
- Cuneate nucleus
Gracile fasciculus and cuneate fasciculus
Two tracts in the posterior columns of the spinal cord, which contain ascending sensory axons. They form synapses in the gracile and cuneate nuclei.
Medial leminscus
Band of white matter which extends through the medulla, pons, and midbrain.
Posterior column-medial lemniscus pathway
The tracts of the posterior columns and the axons of the medial lemniscus.
The medulla contains nuclei associated with five pairs of cranial nerves. What are they?
- Vestibulocochlear (VIII) nerves
- Glossopharyngeal (IX) nerves
- Vagus (X) nerves
- Accessory (XI) nerves
- Hypoglossal (XII) nerves
Pons
Is a bridge that connects parts of the brain with one another. Contains sensory and motor tracts.
What two kinds of nuclei can be found in the pons?
- Pontine nuclei
- Vestibular nuclei
Pontine nuclei
Relay nerve impulses from motor areas of the cerebral cortex to the cerebellum.
Pontine respiratory group
Together with the medulla, helps control breathing.
The pons contains nuclei associated with four pairs of cranial nerves. What are they?
- Trigeminal (V) nerves
- Abducens (VI) nerves
- Facial (VII) nerves
- Vestibulocochlear (VIII) nerves
Midbrain
AKA mesencephalon; contains sensory and motor tracts.
Cerebral peduncles
Paired bundles of axons found in the anterior part of the midbrain. Consist of axons of the corticospinal, corticobulbar, and corticopontine tracts, which conduct nerve impulses from motor areas in the cerebral cortex to the spinal cord, medulla, and pons, respectively.
Tectum
Posterior part of the midbrain. Contains four rounded elevations.
Superior colliculi
The two superior elevations of the tectum. Coordinate movements of head, eyes, and trunk in response to visual stimuli.
Inferior colliculi
The two inferior elevations of the tectum. Coordinate movements of head, eyes, and trunk in response to auditory stimuli.
Substantia nigra and red nuclei
Together contribute to control of movement.
The midbrain contains nuclei associated with two pairs of cranial nerves. What are they?
- Oculomotor (III) nerves
- Trochlear (IV) nerves
Reticular formation
The broad region where white matter and gray matter exhibit a netlike arrangement. Functions in consciousness and arousal.
Reticular activating system (RAS)
The ascending portion of the reticular formation. Consists of sensory axons that project to the cerebral cortex, both directly and through the thalamus. Many sensory stimuli can activate the ascending portion of the RAS.
Perhaps the most important function of the RAS is ______. The RAS also is active during ______, helps maintain ______, and prevents ______. Inactivation of the RAS produces ______, and damage to the RAS results in ______. The descending portion of the RAS has connections to the cerebellum and spinal cord and helps regulate ______. This portion of the RAS also assists in the regulation of heart rate, blood pressure, and respiratory rate.
Consciousness; arousal; attention; sensory overload; sleep; coma; muscle tone
Cerebellum
Smooths and coordinates contractions of skeletal muscles. Regulates posture and balance. May have role in cognition and language processing.
Transverse fissure
A deep groove. Separates the cerebellum from the cerebrum.
Vermis
The central constricted area of the cerebellum.
Cerebellar hemispheres
The lateral “wings” or lobes of the cerebellum. Each hemisphere consists of lobes separated by deep and distinct fissures.
Anterior and posterior lobes
Govern subconscious aspects of skeletal muscle movements.
Flocculonodular lobe
On the inferior surface of the cerebellum. Contributes to equilibrium and balance.
Cerebellar cortex
The superficial layer of the cerebellum. Consists of gray matter in folia.
Folia
Series of slender, parallel folds.
Arbor vitae
Deep to the gray matter. Tracts of white matter that resemble branches of a tree.