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.
Cerebellar nuclei
Regions of gray matter that give rise to axons carrying impulses from the cerebellum to other brain centers. Within the white matter.
Cerebellar peduncles
Bundles of white matter that consist of axons that conduct impulses between the cerebellum and other parts of the brain. Attach the cerebellum to the brainstem. Three of them.
What are the three cerebellar penducles?
- Superior cerebellar peduncles
- Middle cerebellar peduncles
- Inferior cerebellar peduncles
What are the three components of the diencephalon?
- Thalamus
- Hypothalamus
- Epithalamus
Thalamus
Relays almost all sensory input to cerebral cortex. Contributes to motor functions by transmitting information from cerebellum and basal nuclei to primary motor area of cerebral cortex. Plays role in maintenance of consciousness.
Interthalamic adhesion
AKA intermediate mass; a bridge of gray matter that joins the right and left halves of the thalamus in about 70% of human brains.
Internal medullary lamina
A vertical Y-shaped sheet of white matter that divides the gray matter of the right and left sides of the thalamus. Consists of myelinated axons that enter and leave the various thalamic nuclei.
Internal capsule
A thick band of white matter lateral to the thalamus that axons that connect the thalamus and cerebral cortex pass through.
Based on their positions and functions, there are seven major groups of nuclei on each side of the thalamus. What are they?
- Anterior nucleus
- Medial nuclei
- Nuclei in the lateral group
- Nuclei in the ventral group
- Intralaminar nuclei
- Midline nucleus
- Reticular nucleus
Hypothalamus
Controls many body activities and is one of the major regulators of homeostasis. Controls and integrates activities of autonomic nervous system. Produces hormones, including releasing hormones, inhibiting hormones, oxytocin, and antidiuretic hormone (ADH). Regulates emotional and behavioral patterns (together with limbic system). Contains feeding and satiety centers (regulate eating), thirst center (regulates drinking), and suprachiasmatic nucleus (regulates circadian rhythms). Controls body temperature by serving as body’s thermostat.
The hypothalmus is composed of a dozen or so nuclei in four major regions. What are they?
- Mamillary region
- Tuberal region
- Supraoptic region
- Preoptic region
The mammillary region includes the ______ and ______.
Mammillary bodies; posterior hypothalamic nuclei
Infundibulum
Connects the pituitary gland to the hypothalamus
Median eminence
Is a slightly raised region that encircles the infundibulum.
Epithalamus
Consists of pineal gland and habenular nuclei.
Pineal gland
Secretes melatonin
Melatonin
Helps regulate circadian rhythms.
Habenular nuclei
Involved in olfaction.
Circumventricular organs (CVOs)
Lie in the wall of the third ventricle and can monitor chemical changes in the blood because they lack a blood-brain barrier. These regions coordinate homeostatic activities of the endocrine and nervous systems, such as the regulation of blood pressure, fluid balance, hunger, and thirst.
Cerebrum
Is the “seat of intelligence.” It provides us with the ability to read, write, and speak; to make calculations and compose music; and to remember the past, plan for the future, and imagine things that have never existed before. Consists of an outer cerebral cortex, an internal region of cerebral white matter, and gray matter nuclei deep within the white matter.
Cerebral cortex
Is a region of gray matter that forms the outer rim of the cerebrum. Contains sensory areas, motor areas, and association areas.
Gyri
AKA convolutions; folds in cortex. Develop during embryonic development, when brain size increases rapidly, and the gray matter of the cortex enlarges much faster than the deeper white matter. As a result, the cortical region rolls and folds on itself.
Fissure
The deepest grooves between folds.
Sulci
The shallower grooves between folds.
Longitudinal fissure
The most prominent fissure; separates the cerebrum into cerebral hemispheres.
Cerebral hemispheres
Right and left halves of the cerebrum.
Central sulcus
Separates the frontal lobe from the parietal lobe.
Precentral gyrus
A major gyrus. Contains the primary motor area of the cerebral cortex.
Postcentral gyrus
A major gyrus. Contains the primary somatosensory area of the cerebral cortex.
Lateral cerebral sulcus
Separates the frontal lobe from the temporal lobe.
Parieto-occipital sulcus
Separates the parietal lobe from the occipital lobe.
Insula
Part of the cerebrum. Cannot be seen at the surface of the brain because it lies within the lateral cerebral sulcus, deep to the parietal, frontal, and temporal lobes.
What are the three tracts that compose the cerebral white matter?
- Association tracts
- Commissural tracts
- Projection tracts
Association tracts
Contain axons that conduct nerve impulses between gyri in the same hemisphere.
Commissural tracts
Contain axons that conduct nerve impulses from gyri in one cerebral hemisphere to corresponding gyri in the other cerebral hemisphere. Three important groups of commissural tracts are the corpus callosum, anterior commissure, and posterior commissure.
Corpus callosum
A broad band of white matter containing axons that extend between the cerebral hemispheres and connects them. The largest fiber bundle in the brain.
Projection tracts
Contain axons that conduct nerve impulses from the cerebrum to lower parts of the CNS (thalamus, brainstem, or spinal cord) or from lower parts of the CNS to the cerebrum (Eg. The Internal capsule).
Basal nuclei
Helps initiate and terminate movements, suppress unwanted movements, and regulate muscle tone.
What are the three nuclei of the basal nuclei?
- Globus pallidus
- Putamen
- Caudate nucleus
Together, the globus pallidus and putamen are referred to as ______.
Lentiform nucleus
Together, the lentiform and caudate nuclei are known as ______.
Corpus straitum
Limbic system
Limbic system promotes range of emotions, including pleasure, pain, docility, affection, fear, and anger. Also functions in memory.
What are the eight main components of the limbic system?
- Limbic lobe
- Dentate gyrus
- Amygdala
- Septal nuclei
- Mammillary bodies
- Two nuclei of the thalamus
- Olfactory bulbs
- The fornix, stria terminalis, stria medullaris, medial forebrain bundle, and mammillothalamic tract.
Sensory area
Area of the cerebral cortex that is involved in perception of sensory information.
______ receive sensory information that has been relayed from peripheral sensory receptors through lower regions of the brain. ______ often are adjacent to the primary areas. They usually receive input both from the primary areas and from other brain regions. ______ integrate sensory experiences to generate meaningful patterns of recognition and awareness.
Primary sensory areas; sensory association areas; sensory association areas
Sensory homunculus
The distorted somatic sensory map of the body.
What are the five important sensory areas?
- Primary somatosensory area
- Primary visual area
- Primary auditory area
- Primary gustatory area
- Primary olfactory area
Motor area
Area of the cerebral cortex that controls execution of voluntary movements.
Motor homonculus
Distorted muscle map of the body due to the unequal muscle representation in the primary motor area.
What are the two important motor areas?
- Primary motor area
- Broca’s speech area
Association areas
Area of the cerebral cortex that deals with more complex integrative functions such as memory, personality traits, and intelligence.
What are the ten important association areas?
- Somatosensory association area
- Visual association area
- Facial recognition area
- Auditory association area
- Orbitofrontal cortex
- Wernicke’s area (AKA posterior language area)
- Common integrative area
- Prefrontal cortex
- Premotor area
- Frontal eye field area
Hemispheric lateralization
Functional asymmetry of hemispheres of the brain.
Brain waves
Millions of nerve impulses (action potentials) together.
Electroencephalogram (EEG)
Record of brain waves. Brain waves generated by neurons close to the brain surface can be detected by sensors called electrodes placed on the forehead and scalp.
What are the four types of brain waves? When are they active?
- Alpha waves (appear when individuals are awake and resting with their eyes closed. These waves disappear entirely during sleep)
- Beta waves (appear when the nervous system is active – that is, during periods of sensory input and mental activity)
- Theta waves (appear in children and adults experiencing emotional stress)
- Delta waves (appear during deep sleep in adults, but they are normal in awake infants. When produced by an awake adult, they indicate brain damage)
Cranial nerves
12 pairs; are part of the peripheral nervous system (PNS).
Special sensory nerves
Three cranial nerves (I, II, and VIII) that carry axons of sensory neurons. These nerves are unique to the head and are associated with the special senses of smelling, seeing, and hearing.
Motor nerves
Five cranial nerves (III, IV, VI, XI, and XII) that only contain axons of motor neurons as they leave the brainstem.
What are the three types of axons associated with motor nerves?
- Branchial motor axons
- Somatic motor axons
- Autonomic motor axons
Mixed nerves
Four cranial nerves (V, VII, IX, and X) that contain axons both of sensory neurons entering the brainstem and motor neurons leaving the brainstem. Each cranial nerve is a paired structure.
Olfactory (I) nerve
Is a special sensory nerve. Its principal function is olfaction (smell).
Olfactory bulbs
Paired masses of grey matter where olfactory nerves end. They are extensions of the brain that rest on the cribriform plate.
Olfactory tracts
Axons of neurons in the olfactory pathway, which extend posteriorly from the olfactory bulbs. Axons in the olfactory tracts end in the primary olfactory area in the temporal lobe of the cerebral cortex.
Optic (II) nerve
Is a special sensory nerve. Its principal function is vision (sight).
Optic chiasm
Formed by the two optic nerves merging.
Optic tracts
Formed by the regrouped axons from each eye. Most axons in the optic tracts end in the lateral geniculate nucleus of the thalamus. There they synapse with neurons whose axons extend to the primary visual area in the occipital lobe of the cerebral cortex. A few axons pass through the lateral geniculate nucleus and then extend to the superior colliculi of the midbrain and to motor nuclei of the brainstem where they synapse with motor neurons that control the extrinsic and intrinsic eye muscles.
The oculomotor, trochlear, and abducens nerves are the cranial nerves that control the muscles that ______.
Move the eyeballs
Oculomotor (III) nerve
Is a motor nerve, with somatic and motor (autonomic) components. The somatic component’s principal function is movement of eyeballs and upper eyelid, and the motor component’s principal function is to adjust lens for near vision (accommodation) and constriction of pupil.
Which ganglion is associated with the oculomotor (III) nerve?
Ciliary ganglion
Trochlear (IV) nerve
Is a motor nerve, with a somatic component. The somatic component’s principal function is movement of eyeballs.
Abducens (VI) nerve
Is a motor nerve, with a somatic component. The somatic component’s principal function is movement of eyeballs.
Trigeminal (V) nerve
Is a mixed nerve, with sensory and motor (branchial) components. The sensory component’s principal function is touch, pain, and thermal sensations from scalp, face, and oral cavity (including teeth and anterior two-thirds of tongue). Then the motor component’s principal function is chewing and controlling middle ear muscle.
Which ganglion is associated with the trigeminal (V) nerve?
Trigeminal (semilunar) ganglion
What are the three branches of the trigminal nerve?
- Ophthalamic branch
- Maxillary branch
- Mandibular branch
Facial (VII) nerve
Is a mixed nerve, with sensory, motor (branchial), and motor (autonomic) components. The sensory component’s principal function is taste from anterior two thirds of tongue and touch, pain, and thermal sensations from skin in external ear canal. The motor (branchial) component’s principal function is control of muscles of facial expression and middle ear muscle. Lastly, the motor (autonomic) component’s principal function is secretion of tears and saliva.
Which three ganglia are associated with the facial (VII) nerve?
- Geniculate ganglion
- Pterygopalatine ganglion
- Submandibular ganglion
Vestibulocochlear (VIII) nerve
Is a special sensory nerve. Its principal function is hearing and equilibrium.
What are the two branches of the vestibulocochlear (VIII) nerve?
- Vestibular branch
- Cochlear branch
Which two ganglia are associated with the vestibulocochlear (VIII) nerve?
- Vestibular ganglia
- Spiral ganglion
Glossopharyngeal (IX) nerve
Is a mixed nerve, with sensory, motor (branchial), and motor (autonomic) components. The sensory component’s principal function is taste from posterior one-third of tongue, proprioception in some swallowing muscles, monitoring blood pressure and oxygen and carbon dioxide levels in blood, and touch, pain, and thermal sensations from skin of external ear and upper pharynx. The motor (branchial) component’s principal function is to assist in swallowing. Lastly, the motor (autonomic) component’s principal function is secretion of saliva.
Which three ganglia are associated with the glossopharyngeal (IX) nerve?
- Superior ganglion
- Inferior ganglion
- Otic ganglion
Vagus (X) nerve
Is a mixed nerve, with sensory, motor (branchial), and motor (autonomic) components. The sensory component’s principal function is taste from epiglottis, proprioception from throat and voice box muscles, monitoring blood pressure and oxygen and carbon dioxide levels in blood, touch, pain, and thermal sensations from skin of external ear, and sensations from thoracic and abdominal organs. The motor (branchial) component’s principal function is swallowing, vocalization, and coughing. Lastly, the motor (autonomic) component’s principal function is motility and secretion of gastrointestinal organs, constriction of respiratory passageways, and it decreases heart rate.
Which two ganglia are associated with the vagus (X) nerve?
- Superior ganglion
- Inferior ganglion
Accessory (XI) nerve
Is a motor nerve, with a brachial component. The brachial component’s principal function is movement of head and pectoral girdle.
Hypoglossal (XII) nerve
Is a motor nerve, with a somatic component. The somatic component’s principal function is speech, manipulation of food, and swallowing.
