Chapter 14 Flashcards
(265 cards)
1
Q
The development of the nervous system begins with
A
a thickening of the ectoderm called the neural tube
2
Q
The brain is protected by
A
Cranial bones
Cranial menenges
Cerebrospinal fluid
Pia mater
arachnoid mater
dura mater
3
Q
Blood flows to the brain via
A
the vertebral and carotid arteries
4
Q
Blood flows from the brain back to the heart via
A
the jugular veins
5
Q
Any interuption in oxygen supply to the brain can result in
A
weakening, permanent damage, or death of brain cells
6
Q
The blood brain barrier
A
protects the brain cells from harmful substances
7
Q
what is the Neurolemma
A
The outer nucleated cytoplasmic layerof a schwann cell that completel surrounds the myelin sheath.
8
Q
What does the neurolemma do
A
aids in the regrowth and regeneration of an axon
9
Q
The brain contributes to homeostasis by
A
receiving sensory input, integrating new and stored information, making decisions, and executing responses through motor activities.
10
Q
On average, each neuron forms _____ synapses with other neurons.
A
1000
11
Q
The brain and spinal cord develop from
A
the ectodermal neural tube
12
Q
primary brain vesicles:
A
prosencephalon, mesencephalon, and rhombencephalon
13
Q
The prosencephalon (PROS-en-sef′-a-lon), or forebrain, gives rise to ,
A
the telencephalon and diencephalon
14
Q
rhombencephalon (ROM-ben-sef′-a-lon), or hindbrain, develops into
A
the metencephalon and myelencephalon.
15
Q
the metencephalon and myelencephalon the telencephalon and the diencephalon are the
A
secondary brain vesicles
16
Q
The telencephalon (tel′-en-SEF-a-lon; tel- = distant; -encephalon = brain) develops into
A
the cerebrum and lateral ventricles.
17
Q
The diencephalon (dī′-en-SEF-a-lon) forms
A
the thalamus, hypothalamus, epithalamus, and third ventricle.
18
Q
The mesencephalon (mes′-en-SEF-a-lon; mes- = middle), or midbrain,
A
gives rise to the midbrain and aqueduct of the midbrain.
19
Q
The metencephalon (met′-en-SEF-a-lon; met- = after) becomes
A
the pons, cerebellum, and upper part of the fourth ventricle.
20
Q
The myelencephalon (mī-el-en-SEF-a-lon; myel- = marrow) forms
A
the medulla oblongata and lower part of the fourth ventricle.
21
Q
The adult brain consists of four major parts:
A
brainstem, cerebellum, diencephalon, and cerebrum
22
Q
The brainstem is continuous with the spinal cord and consists of
A
the medulla oblongata, pons, and midbrain
23
Q
Posterior to the brainstem is the
A
cerebellum
24
Q
Superior to the brainstem is the
A
diencephalon
25
the diencephalon (di- = through) consists of
the thalamus, hypothalamus, and epithalamus.
26
Supported on the diencephalon and brainstem is
the cerebrum (se-RĒ-brum = brain), the largest part of the brain.
27
The four principal parts of the brain are
the brainstem, cerebellum, diencephalon, and cerebrum.
28
The cranial meninges (me-NIN-jēz)
are continuous with the spinal meninges, have the same basic structure, and bear the same names: the outer dura mater (DOO-ra MĀ-ter), the middle arachnoid mater (a-RAK-noyd), and the inner pia mater (PĒ-a or PĪ-a) (Figure 14.2).
29
the cranial dura mater has two layers;
the spinal dura mater has only one. The two dural layers are called the periosteal layer (which is external) and the meningeal layer (which is internal).
30
there is no ___________around the brain.
epidural space
31
(1) The falx cerebri (FALKS ser-i-BRĒ; falx = sickle)
separates the two hemispheres (sides) of the cerebrum.
32
The falx cerebelli (ser′-e-BEL-ī)
separates the two hemispheres of the cerebellum.
33
The tentorium cerebelli (ten-TŌ-rē-um = tent)
separates the cerebrum from the cerebellum.
34
Cranial bones and cranial meninges
protect the brain.
35
Blood flows to the brain mainly via
the internal carotid and vertebral arteries
36
the dural venous sinuses drain into the internal jugular veins to
return blood from the head to the heart
37
the brain consumes
about 20% of the oxygen and glucose used by the body, even when you are resting.
38
Because virtually no glucose is stored in the brain,
the supply of glucose also must be continuous
39
If blood entering the brain has a low level of glucose,
mental confusion, dizziness, convulsions, and loss of consciousness may occur.
40
The blood–brain barrier (BBB) consists mainly of
tight junctions that seal together the endothelial cells of brain blood capillaries and a thick basement membrane that surrounds the capillaries.
41
The BBB
allows certain substances in blood to enter brain tissue and prevents passage to others. Lipid-soluble substances (including O2, CO2, steroid hormones, alcohol, barbiturates, nicotine, and caffeine) and water molecules easily cross the BBB by diffusing across the lipid bilayer of endothelial cell plasma membranes
42
A few water-soluble substances, such as glucose
, quickly cross the BBB by facilitated transport. Other water-soluble substances, such as most ions, are transported across the BBB very slowly.
43
proteins and most antibiotic drugs—
do not pass at all from the blood into brain tissue. Trauma, certain toxins, and inflammation can cause a breakdown of the BBB.
44
Cerebrospinal fluid (CSF)
is 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
45
CSF continuously circulates
through cavities in the brain and spinal cord and around the brain and spinal cord in the subarachnoid space
46
CSF contains
small amounts of glucose, proteins, lactic acid, urea, cations (Na+, K+, Ca2+, Mg2+), and anions (Cl− and HCO3−); it also contains some white blood cells.
47
ventricles
four CSF-filled cavities within the brain,
48
There is one lateral ventricle in
each hemisphere of the cerebrum.
49
Anteriorly, the lateral ventricles are separated by
a thin membrane, the septum pellucidum
50
The third ventricle is
a narrow, slitlike cavity along the midline superior to the hypothalamus and between the right and left halves of the thalamus.
51
The fourth ventricle lies
between the pons and medulla anteriorly and the cerebellum posteriorly.
52
The CSF has three basic functions in helping to maintain homeostasis.
Mechanical protection
Chemical protection
circulation
53
Describe the mechanical protection provided by CSF
CSF serves as a shock-absorbing medium that protects the delicate tissues of the brain and spinal cord from jolts that would otherwise cause them to hit the bony walls of the cranial cavity and vertebral canal. The fluid also buoys the brain so that it “floats” in the cranial cavity.
54
Describe the chemical protection provided by CSF
CSF provides an optimal chemical environment for accurate neuronal signaling. Even slight changes in the ionic composition of CSF within the brain can seriously disrupt production of action potentials and postsynaptic potentials.
55
describe how the circulation of CSF contributes to homeostasis
CSF is a medium for minor exchange of nutrients and waste products between the blood and adjacent nervous tissue.
56
Ventricles are
cavities within the brain that are filled with cerebrospinal fluid.
57
The majority of CSF production is from the
choroid plexuses
58
choroid plexuses
networks of blood capillaries in the walls of the ventricles
59
Selected substances (mostly water) from the blood plasma, which are filtered from the capillaries, are secreted by the ependymal cells to produce
the cerebrospinal fluid.
60
Ependymal cells joined by tight junctions
cover the capillaries of the choroid plexuses.
61
Because of the tight junctions between ependymal cells,
materials entering CSF from choroid capillaries cannot leak between these cells; instead, they must pass through the ependymal cells.
62
the 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.
63
The CSF formed in the choroid plexuses of each lateral ventricle flows into the third ventricle through two narrow, oval openings, the
interventricular foramina
64
After CSF enters the third ventricle
More CSF is added by the choroid plexus in the roof of the third ventricle. The fluid then flows through the aqueduct of the midbrain (cerebral aqueduct) (AK-we-dukt), which passes through the midbrain, into the fourth ventricle.
65
CSF enters the subarachnoid space through
three openings in the roof of the fourth ventricle: a single median aperture (AP-er-chur) and paired lateral apertures, one on each side.
66
After the CSF enters the sub arachnoid space
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.
67
Normally, CSF is reabsorbed as rapidly as it is formed by the choroid plexuses
68
Elevated CSF pressure causes a condition called
hydrocephalus
69
CSF is formed from blood plasma by
ependymal cells that cover the choroid plexuses of the ventricles.
70
The brainstem is the part of the brain between
the spinal cord and the diencephalon.
71
The brainstem consists of three structures:
(1) medulla oblongata, (2) pons, and (3) midbrain
72
medulla oblongata (me-DOOL-la ob′-long-GA-ta), or more simply the medulla,
is continuous with the superior part of the spinal cord; it forms the inferior part of the brainstem (Figure 14.5; see also Figure 14.1). The medulla begins at the foramen magnum and extends to the inferior border of the pons,
73
bulges on the anterior aspect of the medulla. These protrusions are called the
pyramids
74
The corticospinal tracts control
voluntary movements of the limbs and trunk
75
Just superior to the junction of the medulla with the spinal cord, 90% of the axons in the left pyramid cross to the right side, and 90% of the axons in the right pyramid cross to the left side. This crossing is called the
decussation of pyramids
76
the decussation of pyramids is why
each side of the brain controls voluntary movements on the opposite side of the body.
77
nuclei
a nucleus is a collection of neuronal cell bodies within the CNS.
78
The cardiovascular (cv) center
regulates the rate and force of the heartbeat and the diameter of blood vessels
79
medullary respiratory center adjusts
the basic rhythm of breathing
80
The vomiting center of the medulla causes
vomiting, the forcible expulsion of the contents of the upper digestive canal through the mouth
81
The deglutition center (dē-gloo-TISH-un) of the medulla promotes
deglutition (swallowing) of a mass of food that has moved from the oral cavity into the pharynx
82
Hiccupping is caused by
spasmodic contractions of the diaphragm
83
Just lateral to each pyramid is an oval-shaped swelling called an
olive
84
Within the olive is
the inferior olivary nucleus,
85
the inferior olivary nucleus,
receives input from the cerebral cortex, red nucleus of the midbrain, and spinal cord. Neurons of the inferior olivary nucleus extend their axons into the cerebellum, where they regulate the activity of cerebellar neurons. By influencing cerebellar neuron activity, the inferior olivary nucleus provides instructions that the cerebellum uses to make adjustments to muscle activity as you learn new motor skills.
86
Nuclei associated with sensations of touch, pressure, vibration, and conscious proprioception are located in the posterior part of the medulla. These nuclei are the
right and left gracile nucleus (GRAS-il = slender) and cuneate nucleus
87
The gustatory nucleus (GUS-ta-tō′-rē) of the medulla
is part of the gustatory pathway from the tongue to the brain; it receives gustatory input from the taste buds of the tongue
88
The cochlear nuclei (KOK-lē-ar) of the medulla are part of the
auditory pathway from the inner ear to the brain; they receive auditory input from the cochlea of the inner ear
89
The vestibular nuclei (ves-TIB-ū-lar) of the medulla and pons
are components of the equilibrium pathway from the inner ear to the brain; they receive sensory information associated with equilibrium from proprioceptors (receptors that provide information regarding body position and movements) in the vestibular apparatus of the inner ear
90
the medulla contains nuclei associated with the following five pairs of cranial nerves
vestibulocochlear
Glossopharyngeal
Vagus
Accessory XI nerves (cranial portion))
Hypoglossal
91
Injury to the medulla can be fatal examples of nonfatal medulla injuries include
Symptoms of nonfatal injury to the medulla may include cranial nerve malfunctions on the same side of the body as the injury, paralysis and loss of sensation on the opposite side of the body, and irregularities in breathing or heart rhythm.
92
The pons (= bridge) lies
directly superior to the medulla and anterior to the cerebellum
93
the pons is
a bridge that connects parts of the brain with one another
94
The pons has two major structural components:
a ventral region and a dorsal region
95
The ventral region of the pons
forms a large synaptic relay station consisting of scattered gray centers called the pontine nuclei
96
The dorsal region of the pons
contains ascending and descending tracts along with the nuclei of cranial nerves.
97
Also within the pons is the pontine respiratory group, shown in Figure 23.23. Together with the medullary respiratory center, the pontine respiratory group helps .
control breathing
98
The pons contains nuclei associated with four pairs of cranial nerves.
Trigeminal
abducens
facial
vestibulocochlear
99
The midbrain or mesencephalon extends from
the pons to the diencephalon
100
The aqueduct of the midbrain passes through
the midbrain, connecting the third ventricle above with the fourth ventricle below
101
The anterior part of the midbrain contains paired bundles of axons known as
the cerebral peduncles
102
The posterior part of the midbrain,
is called the tectum
103
the tectum contains four rounded elevations called
superior and inferior colloculi
104
the superior colliculi
serve as reflex centers for certain visual activities
105
the inferior colliculi, are
part of the auditory pathway, relaying impulses from the receptors for hearing in the inner ear to the brain. These two nuclei are also reflex centers for the startle reflex, sudden movements of the head, eyes, and trunk that occur when you are surprised by a loud noise such as a gunshot.
106
The midbrain contains several other nuclei, including the
left and right substantia nigra
107
Neurons that release dopamine, extending from the substantia nigra to the corpus striatum,
help control subconscious muscle activities. Loss of these neurons is associated with Parkinson’s disease
108
The midbrain also contains the red nuclei
Axons from the cerebellum and cerebral cortex form synapses in the red nuclei which help control muscular movements.
109
other nuclei in the midbrain are associated with two pairs of cranial nerves
Oculomotor
Trochlear
110
The broad region where white matter and gray matter exhibit a netlike arrangement is known as the
reticular formation
111
The reticular formation
extends from the superior part of the spinal cord, throughout the brainstem, and into the inferior part of the diencephalon
112
The ascending portion of the reticular formation is called
the reticular activating system (RAS), which consists of sensory axons that project to the cerebral cortex, both directly and through the thalamus.
113
Perhaps the most important function of the RAS is
consciousness, a state of wakefulness in which an individual is fully alert, aware, and oriented.
114
The RAS is also active during
arousal, or awakening from sleep. Another function of the RAS is to help maintain attention (concentrating on a single object or thought) and alertness. The RAS also prevents sensory overload (excessive visual and/or auditory stimulation) by filtering out insignificant information so that it does not reach consciousness
115
Inactivation of the RAS produces
sleep, a state of partial consciousness from which an individual can be aroused.
116
Damage to the RAS, on the other hand, results in
coma, a state of unconsciousness from which an individual cannot be aroused.
117
The descending portion of the RAS has connections to the cerebellum and spinal cord and
helps regulate muscle tone, the slight degree of involuntary contraction in normal resting skeletal muscles. This portion of the RAS also assists in the regulation of heart rate, blood pressure, and respiratory rate.
118
Even though the RAS receives input from the eyes, ears, and other sensory receptors,
there is no input from receptors for the sense of smell; even strong odors may fail to cause arousal.
119
describe the cerebellum
The cerebellum, second only to the cerebrum in size, occupies the inferior and posterior aspects of the cranial cavity. Like the cerebrum, the cerebellum has a highly folded surface that greatly increases the surface area of its outer gray matter cortex, allowing for a greater number of neurons.
120
A deep groove known as the transverse cerebral fissure, along with the tentorium cerebelli
separates the cerebellum from the cerebrum
121
on the cerebellum
The central constricted area is the vermis (= worm), and the lateral “wings” or lobes are the cerebellar hemispheres
122
describe the function of the lobes of the cerebellum
The anterior lobe and posterior lobe govern subconscious aspects of skeletal muscle movements. The flocculonodular lobe (flok-ū-lō-NOD-ū-lar; flocculo- = wool-like tuft) on the inferior surface contributes to equilibrium and balance.
123
The superficial layer of the cerebellum,
is called the cerebellar cortex, consists of gray matter in a series of slender, parallel ridges called folia
124
Deep to the gray matter of the cerebellum are
tracts of white matter called arbor vitae (AR-bor VĪ-tē = tree of life) that resemble branches of a tree.
125
the cerebellar nuclei,
are regions of gray matter that give rise to axons carrying impulses from the cerebellum to other brain centers.
126
Three paired cerebellar peduncles
attach the cerebellum to the brainstem
127
The superior cerebellar peduncles
contain axons that extend from the cerebellum to the red nuclei of the midbrain and to several nuclei of the thalamus
128
The middle cerebellar peduncles
are the largest peduncles; their axons carry impulses for voluntary movements from the pontine nuclei (which receive input from motor areas of the cerebral cortex) into the cerebellum.
129
The inferior cerebellar peduncles consist of
(1) axons of the spinocerebellar tracts that carry sensory information into the cerebellum from proprioceptors in the trunk and limbs; (2) axons from the vestibular apparatus of the inner ear and from the vestibular nuclei of the medulla and pons that carry sensory information into the cerebellum from proprioceptors in the head; (3) axons from the inferior olivary nucleus of the medulla that enter the cerebellum and regulate the activity of cerebellar neurons; (4) axons that extend from the cerebellum to the vestibular nuclei of the medulla and pons; and (5) axons that extend from the cerebellum to the reticular formation.
130
The primary function of the cerebellum is to
evaluate how well movements initiated by motor areas in the cerebrum are actually being carried out.
131
Aside from this coordination of skilled movements, the cerebellum
is the main brain region that regulates posture and balance.
132
Damage to the cerebellum can result in an inability to coordinate muscular movements, a condition called
ataxia
133
describe the location of the diencephalon
It is almost completely surrounded by the cerebral hemispheres and contains numerous nuclei involved in a wide variety of sensory and motor processing between higher and lower brain centers. The diencephalon extends from the brainstem to the cerebrum and surrounds the third ventricle; it includes the thalamus, hypothalamus, and epithalamus. Projecting from the hypothalamus is the hypophysis, or pituitary gland.
134
The thalumus
consists of paired oval masses of gray matter organized into nuclei with interspersed tracts of white matte
135
what structure joins the right and left halves of the thalamus in about 70% of human brains.
A bridge of gray matter called the interthalamic adhesion (intermediate mass)
136
what divides the gray matter of the right and left sides of the thalamus (Figure 14.9c).
A vertical Y-shaped sheet of white matter called the internal medullary lamina It consists of myelinated axons that enter and leave the various thalamic nuclei.
137
the internal capsule,
a thick band of white matter lateral to the thalamus
138
The thalamus is
the principal relay station for sensory impulses that reach the cerebral cortex from other parts of the brain and the spinal cord.
139
the thalamus contributes to motor functions by
transmitting information from the cerebellum and corpus striatum to the primary motor cortex of the cerebrum
140
there are seven major groups of nuclei on each side of the thalamus
The anterior nucleus
the medial nuclei
the lateral group
the ventral group
the intralaminar nuclei
The preventricular nucleus
the reticular nucleus of the prethalamus
141
The anterior nucleus
receives input from the hypothalamus and sends output to the limbic system (described in Section 14.6). It functions in emotions and memory.
142
The medial nuclei of the thalamus
receive input from the limbic system and basal nuclei and send output to the cerebral cortex. They function in emotions, learning, memory, and cognition (thinking and knowing).
143
Nuclei in the lateral group
receive input from the limbic system, superior colliculi, and cerebral cortex and send output to the cerebral cortex. The lateral dorsal nucleus functions in the expression of emotions. The lateral posterior nucleus and pulvinar nucleus help integrate sensory information.
144
The ventral anterior nucleus of the thalumus
receives input from the basal nuclei and sends output to motor cortex of the cerebrum; it plays a role in movement control
145
The ventral lateral nucleus of the thalamus
receives input from the cerebellum and corpus striatum and sends output to motor areas of the cerebral cortex; it also plays a role in movement control
146
The ventral posterior nucleus of the thalamus
relays impulses for somatic sensations such as touch, pressure, vibration, itch, tickle, temperature, pain, and proprioception from the face and body to the cerebral cortex
147
The lateral geniculate nucleus (je-NIK-ū-lat = bent like a knee)
relays visual impulses for sight from the retina to the primary visual cortex of the cerebrum.
148
The medial geniculate nucleus
relays auditory impulses for hearing from the ear to the primary auditory cortex of the cerebrum
149
Intralaminar nuclei of the thalamus (in′-tra-LA-mi′-nar)
lie within the internal medullary lamina and make connections with the reticular formation, cerebellum, corpus striatum, and wide areas of the cerebral cortex. They function in arousal (activation of the cerebral cortex from the brainstem reticular formation) and integration of sensory and motor information.
150
The periventricular nucleus of the thalamus
forms a thin band adjacent to the third ventricle and has a presumed function in memory and olfaction.
151
The reticular nucleus of the prethalamus
surrounds the lateral aspect of the thalamus, next to the internal capsule. This nucleus monitors, filters, and integrates activities of other thalamic nuclei
152
The hypothalamus (hī′-pō-THAL-a-mus; hypo- = under)
is a small part of the diencephalon located inferior to the thalamus. It is composed of a dozen or so nuclei in four major regions
153
The four major regios of the hypothalamus are
the posterior hypothalamic area (mamillary)
the intermediate hypothalamic area
the anterior hypothalamic area
the preoptic area
154
The mammillary nuclei form two small, rounded projections,
the mammillary bodies, that serve as relay stations for reflexes related to the sense of smell.
155
the infundibular stalk (in-fun-DIB-ū-lar = funnel),
connects the pituitary gland to the hypothalamus
156
The median eminence of the hypothalamus
is a slightly raised region that encircles the infundibular stalk
157
Axons from the paraventricular and supraoptic nuclei form the hypothalamohypophyseal tract (hī′-pō-thal′-a-mō-hī-pō-FIZ-ī-al), which
extends through the infundibular stalk to the posterior lobe of the pituitary
158
The preoptic area anterior to the supraoptic region is usually considered part of the
hypothalamus because it participates with the hypothalamus in regulating certain autonomic activities. The preoptic area contains the medial and lateral preoptic nuclei
159
the hypothalamus
controls many body activities and is one of the major regulators of homeostasis
160
Important functions of the hypothalamus include the following
control of the ANS
Production of hormones
regulation of emotional and behavioral patterns
regulation of eating and drinking
control of body temperatureregulation of circadian rythms
161
The hypothalamus releases what two hormones into the posterior lobe of the pituitary
oxytocin or antidiuretic hormone
162
hypothalamic hormones released into the anterior lobe of the pituitary
releasing hormones and inhibiting hormones
163
Three centers within the hypothalamus that regulate eating and drinking
feeding center (promotes eating)
satiety center (Causes a sensation of fullness)
thirst center
164
The suprachiasmatic nucleus (SCN) of the hypothalamus
serves as the body’s internal biological clock because it establishes circadian (daily) rhythms (ser-KĀ-dē-an), patterns of biological activity (such as the sleep–wake cycle) that occur on a circadian schedule (cycle of about 24 hours).
165
The mechanism responsible for the internal clock in an SCN neuron is
the rhythmic turning on and off of clock genes in the cell’s nucleus, resulting in alternating levels of clock proteins in the cell’s cytosol.
166
The epithalamus (ep′-i-THAL-a-mus; epi- = above),
a small region superior and posterior to the thalamus, consists of the pineal gland and habenular nuclei.
167
The pineal gland (PĪN-ē-al = pineconelike)
is about the size of a small pea and protrudes from the posterior midline of the third ventricle (see Figure 14.1). The pineal gland is part of the endocrine system because it secretes the hormone melatonin.
168
The habenular nuclei (ha-BEN-ū-lar), shown in Figure 14.7a, are involved in
olfaction, especially emotional responses to odors such as a loved one’s cologne or Mom’s chocolate chip cookies baking in the oven.
169
Parts of the diencephalon, are called circumventricular organs (CVOs) (ser′-kum-ven-TRIK-ū-lar)
because they lie around the third ventricle.
170
circumventricular organs
can monitor chemical changes in the blood because they lack a blood–brain barrier. CVOs include part of the hypothalamus, the pineal gland, the pituitary gland, and a few other nearby structures. Functionally, these regions coordinate homeostatic activities of the endocrine and nervous systems,
171
The 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.
172
The cerebrum consists of
an outer cerebral cortex, an internal region of cerebral white matter, and gray matter nuclei deep within the white matter.
173
the cortical region of the cerebrum rolls and folds on itself forming a series of elevated ridges and depressions called
grooves
174
the ridges of the cortical region are called
cerebral gyri
175
three types of grooves of the cerebral cortex
1. cerebral sulci
2. interlobar sulci
3. Cerebral fissures
176
Cerebral sulci (SUL-sī; singular is cerebral sulcus)
are grooves that separate neighboring cerebral gyri.
177
Interlobar sulci are
grooves that separate the various lobes of the cerebrum.
178
Cerebral fissures are
grooves that separate parts of the brain.
179
The most prominent cerebral fissure, the longitudinal cerebral fissure,
separates the cerebrum into right and left halves called cerebral hemispheres.
180
Within the longitudinal cerebral fissure between the cerebral hemispheres is the
falx cerebri
181
The cerebral hemispheres are connected internally by
the corpus callosum (kal-LŌ-sum; corpus = body; callosum = hard), a broad band of white matter containing axons that extend between the cerebral hemispheres at the floor of the longitudinal cerebral fissure
182
The lobes of the cerebrum are named after
the bones that cover them: frontal, parietal, temporal, and occipital lobes
183
The central sulcus (SUL-kus) separates
the frontal lobe from the parietal lobe.
184
A major gyrus, the precentral cerebral gyrus—located immediately anterior to the central sulcus—
contains the primary motor cortex of the cerebrum.
185
the postcentral gyrus
contains the primary somatosensory cortex of the cerebrum.
186
The lateral cerebral sulcus separates
the frontal lobe from the temporal lobe.
187
The parieto-occipital sulcus separates
the parietal lobe from the occipital lobe.
188
the insula,
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
189
The cerebral white matter consists primarily of myelinated axons in three types of tracts
1. Association tracts
2 Commissural tracts
3. Projection tracts
190
Association tracts contain
axons that conduct nerve impulses between cerebral gyri in the same hemisphere
191
Commissural tracts (kom′-i-SYUR-al) contain
axons that conduct nerve impulses from cerebral gyri in one cerebral hemisphere to corresponding cerebral gyri in the other cerebral hemisphere.
192
Three important groups of commissural tracts are
the corpus callosum (the largest fiber bundle in the brain, containing about 300 million fibers), anterior commissure, and posterior commissure.
193
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. An example is the internal capsule, a thick band of white matter that contains both ascending and descending axons
194
Deep within each cerebral hemisphere are nuclei (masses of gray matter) that are collectively termed the corpus striatum (strī-Ā-tum) or basal nuclei
Two of the nuclei of the corpus striatum lie side by side, just lateral to the thalamus. They are the globus pallidus (GLŌ-bus PAL-i-dus; globus = ball; pallidus = pale), which is closer to the thalamus, and the putamen (pū-TĀ-men = shell), which is closer to the cerebral cortex
195
Together, the globus pallidus and putamen are referred to as the
lentiform nucleus
196
The third nucleus of the corpus striatum is
the caudate nucleus (KAW-dāt; caud- = tail), which has a large “head” connected to a smaller “tail” by a long, comma-shaped “body.”
197
The corpus striatum
helps initiate and terminate movements, suppresses unwanted movements, and regulates muscle tone.
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The claustrum (KLAWS-trum)
is a thin sheet of gray matter situated lateral to the putamen. It is considered by some to be a subdivision of the corpus striatum. The function of the claustrum in humans has not been clearly defined, but it may be involved in visual attention.
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The corpus striatum receives input from the
cerebral cortex and provides output to motor parts of the cortex via the medial and ventral group nuclei of the thalamus.
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Other roles of the nuclei of the corpus striatum include
They help initiate and terminate some cognitive processes, attention, memory, and planning, and may act with the limbic system to regulate emotional behaviors.
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Encircling the upper part of the brainstem and the corpus callosum is a ring of structures on the inner border of the cerebrum and floor of the diencephalon that constitutes
the limbic system
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The limbic lobe is
a rim of cerebral cortex on the medial surface of each hemisphere.
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the limbic lobe includes
the cingulate gyrus (SIN-gyu-lat; cingul- = belt), which lies above the corpus callosum, and the parahippocampal gyrus (par′-a-hip-ō-KAM-pal), which is in the temporal lobe below. The hippocampus (hip′-ō-KAM-pus = seahorse) is a portion of the parahippocampal gyrus that extends into the floor of the lateral ventricle.
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the dentate gyrus is a component of the limbic systemthat
lies between the hippocampus and parahippocampal gyrus.
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The amygdala (a-MIG-da-la; amygda- = almond-shaped) is part of the limbic system that is composed of several groups of neurons located close to the tail of the caudate nucleus.
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The septal nuclei is part of the limbic system
located within the septal area formed by the regions under the corpus callosum and the paraterminal gyrus (a cerebral gyrus).
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The mammillary bodies of the hypothalamus
are two round masses close to the midline near the cerebral peduncles. they are components of the limbic system
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Two nuclei of the thalamus, the anterior nucleus and the medial nucleus, participate in
limbic circuits
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The olfactory bulbs
are flattened bodies of the olfactory pathway that rest on the cribriform plate. they are components of the limbic system
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The fornix, stria terminalis, stria medullaris, medial forebrain bundle, and mammillothalamic tract (mam-i-lō-tha-LAM-ik)
are linked by bundles of interconnecting myelinated axons. They are all a part of the limbic system
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The limbic system governs
emotional aspects of behavior.
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The limbic system is also involved in
olfaction and memory
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One portion of the limbic system, the hippocampus, is seemingly unique among structures of the central nervous system—
it has cells reported to be capable of division.
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Specific types of sensory, motor, and integrative signals are processed in
certain regions of the cerebral cortex
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sensory areas
receive sensory information and are involved in perception, the conscious awareness of a sensation;
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motor areas control
the execution of voluntary movements
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association areas deal with
more complex integrative functions such as memory, emotions, reasoning, will, judgment, personality traits, and intelligence.
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Sensory association areas
integrate sensory experiences to generate meaningful patterns of recognition and awareness.
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a person with damage in the ___________ visual cortex would be blind in at least part of his visual field, but a person with damage to a visual ____________ area might see normally yet be unable to recognize ordinary objects such as a lamp or a toothbrush just by looking at them.
Primary
association
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Important sensory areas of the cerebral cortex
primary somatosensory cortex
primary visual cortex
primary auditory cortex
gustatory cortex
olfactory cortex
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The distorted somatic sensory map of the body within the somatosensory cortex is known as the
sensory homunculus
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The primary somatosensory cortex allows you to
pinpoint where somatic sensations originate, so that you know exactly where on your body a stimulus is coming from
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The primary visual cortex,
located at the posterior tip of the occipital lobe mainly on the medial surface (next to the longitudinal cerebral fissure), receives visual information and is involved in visual perception.
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The primary auditory cortex,
located in the superior part of the temporal lobe near the lateral cerebral sulcus, receives information for sound and is involved in auditory perception.
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The primary somatosensory cortex is located
directly posterior to the central cerebral sulcus of each cerebral hemisphere in the postcentral gyrus of each parietal lobe. It extends from the lateral cerebral sulcus, along the lateral surface of the parietal lobe to the longitudinal cerebral fissure, and then along the medial surface of the parietal lobe within the longitudinal cerebral fissure.
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The gustatory cortex,
located in the insula, receives impulses for taste and is involved in gustatory perception and taste discrimination.
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The olfactory cortex,
located in the temporal lobe on the medial aspect, receives impulses for smell and is involved in olfactory perception.
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Particular areas of the cerebral cortex
process sensory, motor, and integrative signals.
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Motor output from the cerebral cortex flows mainly from
the anterior part of each hemisphere
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The four motor areas of the cerebral cortex
The primary motor cortex
The premotor cortex
Brocas area
The frontal eye field
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Electrical stimulation of any point in the primary motor cortex causes
contraction of specific skeletal muscle fibers on the opposite side of the body.
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The primary motor cortex is located
in the precentral gyrus of the frontal lobe
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The distorted muscle map of the body within the primary motor cortex
is called the motor homunculus.
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The premotor cortex is located
immediately anterior to the primary motor cortex.
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The premotor cortex
sends impulses to the primary motor cortex that plan movements that cause specific groups of muscles to contract simultaneously or sequentially.
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Broca’s area (BRŌ-kaz) is located
in the frontal lobe close to the lateral cerebral sulcus
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From Broca’s area,
nerve impulses pass to the premotor regions that control the muscles of the larynx, pharynx, and mouth. The impulses from the premotor cortex result in specific, coordinated muscle contractions. Simultaneously, impulses propagate from Broca’s area to the primary motor cortex. From here, impulses also control the breathing muscles to regulate the proper flow of air past the vocal cords. The coordinated contractions of your speech and breathing muscles enable you to speak your thoughts.
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The frontal eye field is located
partially in and anterior to the premotor cortex and superior to Broca’s area.
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Association areas of the cerebral cortex include
somatosensory association area
visual association area
Facial recognition area
auditory association area
orbitofrontal cortex
Wernickes area
common integrative area
the prefrontal cortex
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The somatosensory association area is located
just posterior to and receives input from the primary somatosensory cortex as well as from the thalamus and other parts of the brain
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The somatosensory association area
permits you to determine the exact shape and texture of an object by feeling it, to determine the orientation of one object with respect to another as they are felt, and to sense the relationship of one body part to another. Another role of the somatosensory association area is the storage of memories of past somatic sensory experiences, enabling you to compare current sensations with previous experiences.
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The visual association area, is located
in the occipital lobe
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the visual association area
receives sensory impulses from the primary visual cortex and the thalamus. It relates present and past visual experiences and is essential for recognizing and evaluating what is seen.
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The facial recognition area, is located
in the inferior temporal lobe,
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the facial recognition area
receives nerve impulses from the visual association area. This area stores information about faces, and it allows you to recognize people by their faces.
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The auditory association area,
is located inferior and posterior to the primary auditory cortex in the temporal lobe, allows you to recognize a particular sound as speech, music, or noise.
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The orbitofrontal cortex,
is located along the lateral part of the frontal lobe, receives sensory impulses from the olfactory cortex. This area allows you to identify odors and to discriminate among different odors. During olfactory processing, the orbitofrontal cortex of the right hemisphere exhibits greater activity than the corresponding region in the left hemisphere.
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Wernicke’s area (VER-ni-kēz) (posterior language area),
a broad region located in the left temporal and parietal lobes, interprets the meaning of speech by recognizing spoken words.
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The regions in the right hemisphere that correspond to Broca’s and Wernicke’s areas in the left hemisphere also contribute
to verbal communication by adding emotional content, such as anger or joy, to spoken words.
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The common integrative area
is bordered by somatosensory, visual, and auditory association areas. It receives nerve impulses from these areas and from the gustatory cortex, the olfactory cortex, the thalamus, and parts of the brainstem. This area integrates sensory interpretations from the association areas and impulses from other areas, allowing the formation of thoughts based on a variety of sensory inputs. It then transmits signals to other parts of the brain for the appropriate response to the sensory signals it has interpreted
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The prefrontal cortex is
an extensive area in the anterior portion of the frontal lobe that is well developed in primates, especially humans.
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The prefrontal cortex is concerned with
the makeup of a person’s personality, intellect, complex learning abilities, recall of information, initiative, judgment, foresight, reasoning, conscience, intuition, mood, planning for the future, and development of abstract ideas.
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although the two hemispheres share performance of many functions, each hemisphere also specializes in performing certain unique functions. This functional asymmetry is termed
hemispheric lateralization.
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At any instant, brain neurons are generating millions of nerve impulses. Taken together, these electrical signals are called
brain waves.
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electroencephalogram EEG
a record of a patients brain waves that is gathered by placing electrodes on the scalp
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Four types of brain waves
Alpha Waves
Beta Waves
Theta Waves
Delta Waves
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Alpha waves.
These rhythmic waves occur at a frequency of about 8–13 cycles per second. (The unit commonly used to express frequency is the hertz [Hz]. One hertz is one cycle per second.) Alpha waves are present in the EEGs of nearly all normal individuals when they are awake and resting with their eyes closed. These waves disappear entirely during sleep.
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Beta waves.
The frequency of these waves is between 14 and 30 Hz. Beta waves generally appear when the nervous system is active—that is, during periods of sensory input and mental activity.
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Theta waves. .
Theta waves (THĀ-ta) have frequencies of 4–7 Hz. These waves normally occur in children and adults experiencing emotional stress
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Delta waves.
The frequency of these waves is 1–5 Hz. Delta waves occur during deep sleep in adults, but they are normal in awake infants. When produced by an awake adult, they indicate brain damage.
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A concussion (kon-KUSH-un) is
an injury characterized by an abrupt, but temporary, loss of consciousness (from seconds to hours), disturbances of vision, and problems with equilibrium.
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chronic traumatic encephalopathy (CTE).
It is a progressive, degenerative brain disorder caused by concussions and other repeated head injuries and occurs primarily among athletes who participate in contact sports such as football, ice hockey, and boxing as well as combat veterans and individuals with a history of repetitive brain trauma
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The signs and symptoms of TBI
range from mild to moderate to severe, depending on the extent of brain damage. A person with mild TBI may remain conscious or lose consciousness. Among other signs and symptoms of mild TBI are headache, slurred speech, confusion, lightheadedness, dizziness, blurred vision, tinnitus, fatigue, sleep disturbances, memory loss, behavioral or mood changes, and difficulty with memory, concentration, attention, and thinking.
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A brain contusion (kon-TOO-zhun) is
bruising due to trauma and includes the leakage of blood from microscopic vessels. It is usually associated with a concussion. In a contusion, the pia mater may be torn, allowing blood to enter the subarachnoid space.
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A laceration (las-er-Ā-shun) is
a tear of the brain, usually from a skull fracture or a gunshot wound. A laceration results in rupture of large blood vessels, with bleeding into the brain and subarachnoid space. Consequences include cerebral hematoma (localized pool of blood, usually clotted, that swells against the brain tissue), edema, and increased intracranial pressure.
