Download The Brain

Anatomy & Physiology I Dr. L. Bacha
Chapter Outline
(Marieb & Hoehn 2013)
The Brain
Regions and Organization
◦ List the four adult brain regions and identify them in Fig. 12.2:
Ventricles
 the four ventricles are cavities within the brain; what are the ventricles continuous with?
 what are they filled with?
 name the cells that line them:
 name and describe the general location of each type of ventricle, and identify each in Fig. 12.3:
- the fourth ventricle is continuous with what inferiorly?
- openings in the walls of the fourth ventricle (apertures) connect the ventricles to what fluid-filled space
around the brain?
Cerebral Hemispheres
• the cerebrum makes up the bulk of the brain and is formed by two halves called cerebral hemispheres
• the cerebrum has numerous gyri and sulci
 define gyri:
 define sulci:
 define fissures:
- what does the longitudinal fissure separate?
• name the 5 lobes into which each cerebral hemisphere is divided:
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• list and briefly describe the three basic regions of each cerebral hemisphere:
Cerebral Cortex
 the cerebral cortex is where our conscious mind is found; what does it enable us to do?
 what is the cerebral cortex composed of?
 how many neurons does it contain?!
 what does having many convolutions (a folded surface) do to surface area?
 read the 4 generalizations about the cerebral cortex on p. 432 to p. 433
1. name the three functional areas that the cerebral cortex contains:
2. each hemisphere is chiefly concerned with what?
3. although largely symmetrical in structure, are the 2 hemispheres entirely equal in function?
4. no functional area of the cortex acts alone, and conscious behavior involves what?
Motor Areas (Fig. 12.8)
∙ what do motor areas control?
∙ motor areas are in what lobe of the cerebrum?
1. Primary motor cortex
- is a specific region of the cerebral cortex that initiates somatic motor impulses for movement of
particular parts of the body
∙ the large neurons called pyramidal cells in the primary motor cortex allow us to do what?
- their long axons, which project to the spinal cord, form what?
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∙ Fig. 12.7 maps where the motor impulses to specific parts of the body originate in the cerebrum. The
entire body is represented spatially in the primary motor cortex of each hemisphere as a caricature-like
“human” called motor homunculus.
2. Premotor cortex
∙ this region controls learned motor skills of a repetitious or patterned nature, such as playing a musical
instrument or typing
∙ what does this region coordinate?
∙think of the premotor cortex as the “memory bank” for skilled motor activities
3. Broca’s area
∙ a special motor speech area that directs what?
4. Frontal eye field
∙ controls what?
Sensory Areas (Fig. 12.8)
∙ what are sensory areas of the cerebral cortex concerned with?
1. primary somatosensory cortex
∙ is in what lobe of the cerebrum?
∙ neurons here receive information (somatic sensory input) from what?
Fig. 12.7 maps where the sensory impulses from specific parts of the body terminate in the primary
somatosensory cortex of the cerebrum; the entire body is represented spatially in the primary
somatosensory cortex according to the site of stimulus input; the amount of sensory cortex devoted
to a particular body region is related to what?
- this results in a distorted somatosensory homunculus
2. somatosensory association cortex - read about this area just because it is interesting!
3. visual areas
 receive and analyze visual information; visual areas are in what lobe of the cerebral cortex?
4. auditory areas
 responsible for auditory reception; auditory areas are in what lobe of the cerebral cortex?
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5. olfactory cortex
 responsible for perception of odors (olfaction); olfactory cortex is in what lobe of the cerebral
cortex?
6. gustatory cortex
 responsible for the perception of taste (gustatory sensation)
7. visceral sensory area
 responsible for conscious perception of visceral sensations
8. vestibular (equilibrium) cortex
 responsible for the detection of body position and spatial awareness
 in the insula and parietal lobe
Lateralization of Cortical Functioning
- describe the phenomenon called lateralization of the cerebral cortex:
Cerebral White Matter
 the white matter is deep to the cerebral cortex and is responsible for what?
 white matter consists largely of what?
 there are three types of fibers and tracts, classified according to the direction in which they run;
summarize what each type connects:
 association fibers:
 commissural fibers:
- the corpus callosum is the largest bundle of commissural axons that links the right and left cerebral
hemispheres; it contains about 300 million axons!
 projection fibers: contain axons that conduct nerve impulses between the cerebrum and the lower
parts of the nervous system) thalamus, brainstem, or spinal cord
Basal Nuclei
 basal nuclei (basal ganglia) are masses of gray matter deep within the white matter of each cerebral
hemisphere
 coordinate gross, automatic muscle movements and regulate muscle tone
 play a role in cognition and emotion; filter out incorrect or inappropriate responses
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Diencephalon
• between the brainstem and the cerebrum
• the diencephalon consists largely of what three paired structures?
• these structures collectively enclose what ventricle?
Thalamus
 the right and left halves of the thalamus are connected at the midline by the interthalamic adhesion
(intermediate mass)
 the thalamus is the major relay station for motor and sensory information to the cerebral cortex; think of
it as the “gateway” to the cerebral cortex
Hypothalamus
 controls many body functions to maintain homeostasis
 list its 7 chief homeostatic roles (in bold print on pages 442):
Epithalamus
 includes the pineal gland; what hormone does the pineal gland secrete?
Brain Stem
 it consists of what three parts?
 it is responsible for many essential functions
 the brain stem contains the nuclei of 10 of the 12 pairs of cranial nerves that enter or exit the brain
through the brainstem
Midbrain
 what is the midbrain located between?
 the dorsal midbrain has two pairs of domelike, elevated nuclei that form the corpora quadrigemina; see
Figs. 12.10 and Fig. 12.13(b and c); the corpora quadrigemina includes:
 two superior colliculi
- involved in visual reflexes; for example, if you are watching a movie and see something
run by out of the corner of your eye, you will reflexively turn to see what it was
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 two inferior colliculi
- part of the auditory pathway and involved in auditory reflexes
- for example, if you are reading your textbook and you hear a loud noise behind you, you will
reflexively turn to see what made the noise
Pons
 describe the pons:
 what does “pons” mean?
 it helps to control normal rhythm of breathing
Medulla Oblongata
 most inferior part of the brain stem; it is continuous with the spinal cord at the foramen magnum
 contains all sensory (ascending) tracts and motor (descending) tracts between the spinal cord and other
parts of the brain; most tracts cross over to the opposite side in the medulla
 the medulla has important visceral motor nuclei, which include:
1. cardiovascular center
- list the two parts of the cardiovascular center and indicate the function of each:
2. respiratory centers, which do what?
3. various other centers, which regulate what?
Cerebellum
 second largest part of the brain
 controls subconscious contraction of skeletal muscles for balance, coordination and posture
 read about the four ways in which cerebellar processing fine-tunes motor activity!
 cerebellar injury results in what?
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Functional Brain Systems
 functional brain systems are what?
The Limbic System
 a functional system that involves the cerebrum and diencephalon
 what are the functions of the limbic system (see Table 12.1 on page 450 for the answer!)?
The Reticular Formation
 a functional system that extends throughout the brainstem
 what are the functions of the reticular formation (see Table 12.1 on page 451 for the answer!)?
Higher Mental Functions
Brain Wave Patterns and the EEG
 what is a recording of the electrical activity of neurons of the brain called and how is it
abbreviated?
 what are the patterns of neuronal electrical activity of the brain called?
Consciousness
 define consciousness (from the glossary in the back of the book; it is more straight forward!):
 except during sleep, unconsciousness is always a signal of what?
 define fainting, or syncope:
Sleep and Sleep-Wake Cycles
 define sleep:
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 define coma:
read the rest of the information on sleep (and on language and memory) if you are interested; otherwise,
take a nap…
Protection of the Brain
Meninges
◦ define meninges:
◦ list the four functions of the meninges:
◦ note the three meninges on Fig. 12.22
Dura Mater
 is a two-layered sheet of fibrous connective tissue that attaches to the periosteum of the skull and forms
the external covering of the brain (and continues caudally in the vertebral canal to enclose the spinal cord)
Arachnoid Mater
 is the middle, weblike meninx
 it is separated from the dura mater by a narrow fluid filled cavity called what?
 name the wide space beneath the arachnoid membrane:
- weblike extensions span the space and secure the arachnoid mater to the pia mater
- what is the subarachnoid space filled with and what does it also contain?
 has arachnoid villi that absorb what fluid?
Pia Mater
 a well vascularized layer that is attached tightly to the surface of the brain
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To remember the order of
the meninges, think that they
form a “p-a-d” around the
brain and spinal cord. Thus,
“p” for pia mater, which
adheres to the brain and
spinal cord; “a” for
arachnoid mater in the
middle; “d” for dura mater,
which is furthest out from the
brain and spinal cord.
Cerebrospinal Fluid
 how is cerebrospinal fluid abbreviated?
 list the functions of cerebrospinal fluid:
 name the structures that hang from the roof of each ventricle and form CSF:
 in adults, what is the total CSF volume?
 the CSF produced by the choroid plexuses circulates through the ventricles of the brain, the central canal
of the spinal cord, and the subarachnoid space around the brain and spinal cord (see Fig. 12.24)
Blood-Brain Barrier
 the blood-brain barrier is a protective mechanism that helps maintain what?
 the brain is the only body organ that is absolutely dependent on what?
 define blood-brain barrier (from the glossary in the back of the book) :
 the special capillaries that form the blood-brain barrier are selective:
 nutrients such as glucose, essential amino acids, and some electrolytes in the blood can
pass through the blood brain barrier by facilitated diffusion
 the capillaries are impermeable to metabolic wastes, proteins, nonessential amino acids,
certain toxins, and most antibiotics
 oxygen, carbon dioxide, alcohol, nicotine, & anesthetics can easily pass through it by
simple diffusion
Note: If a clinician needs to treat an infection of the brain, such as Lyme’s disease, the
drug of choice must be one that can cross the blood-brain barrier to be effective!
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The Spinal Cord
Gross Anatomy and Protection
• the spinal cord extends from the medulla oblongata of the brainstem (at the foramen magnum of the
skull) and extends to what level of the vertebral column?
- so, does the spinal cord extend the entire length of the adult vertebral column?
• it provides a two-way conduction pathway to and from the brain and it is a major reflex center
• what is the spinal cord protected by?
• meninges
 on Figure 12.28, identify the pia mater, arachnoid mater and the dura mater
 also locate the subarachnoid space, subdural space and the epidural space
 the dura mater of the spinal cord does not fuse with the periosteum of the vertebrae; instead there is a
space above the dura mater between it and the periosteum, called the epidural space, filled with fat and
blood vessels
• the spinal cord ends as a tapered conical structure called what?
• the filum terminale is an extension of fibrous CT from the conus medullaris
- what does it extend between and what is its function?
• 31 pairs of spinal nerves attach to the spinal cord by paired roots (see Fig. 12.28)
- each nerve exits from the vertebral column by passing through what foramen?
• the spinal cord is cylindrical and about the width of a thumb for most of its length, with two enlargements:
- name the two enlargements of the spinal cord and indicate to what part of the body each enlargement
supplies nerves:
• because the spinal cord is shorter than the vertebral column, nerves that arise from the lower regions of
the spinal cord do not leave the vertebral column at the same level that they arise from the
spinal cord. Instead, they pass through the vertebral canal for some distance, then emerge
through the intervertebal foramina. The roots of these spinal nerves in the vertebral canal are
collectively are called the cauda equina.
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Spinal Cord Cross-Sectional Anatomy
GRAY MATTER AND SPINAL ROOTS
C what does the gray matter of the spinal cord look like?
C the two lateral gray masses are connected by a crossbar of gray matter called what?
-
- what does the gray commissure enclose?
C define dorsal (posterior) horns:
C define ventral (anterior) horns:
C the lateral horns are present in which segments of the spinal cord?
C all neurons whose cell bodies are in the spinal cord gray matter are what type?
 what do the dorsal horns consist entirely of?
 the ventral horns mainly house the cell bodies of what?
- the axons of the motor neurons to skeletal muscles form the ventral rootlets that fuse together to
become what?
 the lateral horns consist mostly of what and what do they serve?
 what forms the dorsal roots?
- the dorsal roots fan out as dorsal rootlets before they enter the spinal cord
 where are the cell bodies of the associated sensory neurons found?
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WHITE MATTER
 what is the white matter of the spinal cord composed of and what do they allow?
 list the three directions in which these fibers run:
From the glossary in the back of the book, define:
Psst…
over
here…
tract -
nerve
 what makes up most of the white matter?
 the white matter on each side of the cord is divided into three what?
 each column contains several fiber tracts, and each tract is made up of what?
Neuronal Pathway
 all major spinal tracts are part of what?
 these ascending and descending pathways contain not only spinal cord neurons but also parts of what?
List and briefly summarize the four key generalizations about the tracts and pathways to which they
contribute:
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ASCENDING PATHWAYS TO THE BRAIN
 summarize how ascending (sensory) pathways conduct sensory impulses:
 first-order neurons have cell bodies in ganglia
- they conduct impulses from what structures?
- they conduct impulses to what structures, where they synapse with second order neurons?
second-order neurons have cell bodies in the dorsal horn of the spinal cord or in nuclei of the medulla
oblongata
- they transmit impulses to what?
 third-order neurons have cell bodies in the thalamus
- they relay impulses to what?
 in general, somatosensory information is conveyed along three main ascending pathways on each side of
the spinal cord (see Fig. 12.30 and Fig. 12.31):
1. dorsal white columns
provide discriminative touch and conscious proprioception
2. spinothalamic tracts
3. spinocerebellar tracts convey information about muscle or tendon stretch
DESCENDING PATHWAYS AND TRACTS
 descending (motor) tracts convey information from the brain to the spinal cord (see Fig. 12.32)
 motor pathways involve two neurons, referred to as what?
 upper motor neurons have cell bodies in the brain
 lower motor neurons are the neurons in the ventral horns of the spinal cord that actually innervate the
skeletal muscles
 pyramidal (corticospinal) pathways control skilled voluntary movements
 other descending pathways regulate muscles that maintain balance and posture,
muscles that control coarse limb movements, and muscles that control head, neck
and eye movements in response to visual stimuli
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The
End!