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CNS Physiology
For Bio 260
Regions and Organization of the CNS
•
Adult brain regions
1.
2.
3.
4.
Cerebral hemispheres
Diencephalon
Brain stem (midbrain, pons, and medulla)
Cerebellum
Precentral
gyrus
Frontal
lobe
Central
sulcus
Postcentral
gyrus
Parietal lobe
Parieto-occipital sulcus
(on medial surface
of hemisphere)
Lateral sulcus
Occipital lobe
Temporal lobe
Transverse cerebral fissure
Cerebellum
Pons
Medulla oblongata
Spinal cord
Fissure
(a deep
sulcus)
Gyrus
Cortex (gray matter)
Sulcus
White matter
(a)
Figure 12.6a
Motor areas
Central sulcus
Primary motor cortex
Premotor cortex
Frontal eye field
Broca’s area
(outlined by dashes)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
(a) Lateral view, left cerebral hemisphere
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatic
Somatosensory
sensation
association cortex
Gustatory cortex
(in insula)
Taste
Wernicke’s area
(outlined by dashes)
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Vision
Hearing
Motor association cortex
Primary sensory cortex
Primary motor cortex
Sensory association cortex
Multimodal association cortex
Figure 12.8a
Primary Somatosensory Cortex
• In the postcentral gyri
• Receives sensory information from the skin,
skeletal muscles, and joints
• Capable of spatial discrimination:
identification of body region being stimulated
Multimodal Association Areas
• Receive inputs from multiple sensory areas
• Send outputs to multiple areas, including the
premotor cortex
• Allow us to give meaning to information
received, store it as memory, compare it to
previous experience, and decide on action to
take
Premotor cortex
Corpus
callosum
Cingulate
gyrus
Primary
motor cortex
Frontal eye field
Prefrontal
cortex
Processes emotions
related to personal
and social interactions
Orbitofrontal
cortex
Olfactory bulb
Olfactory tract
Fornix
Temporal lobe
(b) Parasagittal view, right hemisphere
Uncus
Primary
olfactory cortex
Central sulcus
Primary somatosensory
cortex
Parietal lobe
Somatosensory
association cortex
Parieto-occipital
sulcus
Occipital
lobe
Visual
association
area
Primary
visual cortex
Calcarine sulcus
Parahippocampal
gyrus
Motor association cortex
Primary sensory cortex
Primary motor cortex
Sensory association cortex
Multimodal association cortex
Figure 12.8b
Anterior Association Area (Prefrontal
Cortex)
• Most complicated cortical region
• Involved with intellect, cognition, recall, and
personality
• Contains working memory needed for
judgment, reasoning, persistence, and
conscience
• Development depends on feedback from
social environment
Posterior Association Area
• Large region in temporal, parietal, and
occipital lobes
• Plays a role in recognizing patterns and faces
and localizing us in space
• Involved in understanding written and spoken
language (Wernicke’s area)
Lateralization of Cortical Function
• Left hemisphere
– Controls language, math, and logic
• Right hemisphere
– Insight, visual-spatial skills, intuition, and artistic
skills
• Left and right hemispheres communicate via
fiber tracts in the cerebral white matter
Basal Nuclei (Ganglia)
• Subcortical nuclei
• Consists of the corpus striatum
– Caudate nucleus
– Lentiform nucleus (putamen + globus pallidus)
• Functionally associated with the subthalamic
nuclei (diencephalon) and the substantia nigra
(midbrain)
Functions of Basal Nuclei
• Though somewhat elusive, the following are
thought to be functions of basal nuclei
– Influence muscular control
– Help regulate attention and cognition
– Regulate intensity of slow or stereotyped
movements
– Inhibit antagonistic and unnecessary movements
Thalamic Function
• Gateway to the cerebral cortex
• Sorts, edits, and relays information
– Afferent impulses from all senses and all parts of the body
– Impulses from the hypothalamus for regulation of emotion
and visceral function
– Impulses from the cerebellum and basal nuclei to help
direct the motor cortices
• Mediates sensation, motor activities, cortical arousal,
learning, and memory
Cerebral hemisphere
Septum pellucidum
Interthalamic
adhesion
(intermediate
mass of
thalamus)
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla oblongata
Corpus callosum
Fornix
Choroid plexus
Thalamus
(encloses third
ventricle)
Posterior commissure
Pineal gland
(part of epithalamus)
Corpora
quadrigemina MidCerebral
brain
aqueduct
Arbor vitae (of
cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Spinal cord
Figure 12.12
Hypothalamic Function
• Autonomic control center for many visceral
functions (e.g., blood pressure, rate and force
of heartbeat, digestive tract motility)
• Center for emotional response: Involved in
perception of pleasure, fear, and rage and in
biological rhythms and drives
Hypothalamic Function
• Regulates body temperature, food intake,
water balance, and thirst
• Regulates sleep and the sleep cycle
• Controls release of hormones by the anterior
pituitary
• Produces posterior pituitary hormones
View (a)
Optic chiasma
Optic nerve (II)
Crus cerebri of
cerebral peduncles
(midbrain)
Diencephalon
• Thalamus
• Hypothalamus
Mammillary body
Thalamus
Hypothalamus
Diencephalon
Midbrain
Oculomotor nerve (III)
Trochlear nerve (IV)
Pons
Brainstem
Medulla
oblongata
Trigeminal nerve (V)
Pons
Facial nerve (VII)
Middle cerebellar
peduncle
Abducens nerve (VI)
Vestibulocochlear
nerve (VIII)
Pyramid
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Vagus nerve (X)
Ventral root of first
cervical nerve
Decussation of pyramids
Accessory nerve (XI)
Spinal cord
(a) Ventral view
Figure 12.15a
Spinal Cord Physiology
Dorsal root (sensory)
Dorsal root ganglion
Dorsal horn (interneurons)
Somatic
sensory
neuron
Visceral
sensory
neuron
Visceral
motor
neuron
Somatic
motor neuron
Spinal nerve
Ventral root
(motor)
Ventral horn
(motor neurons)
Interneurons receiving input from somatic sensory neurons
Interneurons receiving input from visceral sensory neurons
Visceral motor (autonomic) neurons
Somatic motor neurons
Figure 12.32
Ascending tracts
Fasciculus gracilis
Dorsal
white Fasciculus cuneatus
column
Dorsal
spinocerebellar
tract
Ventral
spinocerebellar
tract
Lateral
spinothalamic tract
Ventral spinothalamic
tract
Descending tracts
Ventral white
commissure
Lateral
reticulospinal tract
Lateral
corticospinal tract
Rubrospinal
tract
Medial
reticulospinal
tract
Ventral corticospinal
tract
Vestibulospinal tract
Tectospinal tract
Figure 12.33
Example of a tract
Anterolateral Pathways
• Lateral and ventral spinothalamic tracts
• Transmit pain, temperature, and coarse touch
impulses within the lateral spinothalamic tract
Lateral
spinothalamic
tract (axons of
second-order
neurons)
Medulla oblongata
Pain receptors
Cervical spinal cord
Lumbar spinal cord
Axons of first-order
neurons
Temperature
receptors
(b) Spinothalamic pathway
Figure 12.34b (2 of 2)
Primary
somatosensory
cortex
Axons of third-order
neurons
Thalamus
Cerebrum
Midbrain
Cerebellum
Pons
(b) Spinothalamic pathway
Figure 12.34b (1 of 2)
Example of Clinical Consideration
Spinal Cord Trauma
• Spastic paralysis—damage to upper motor
neurons of the primary motor cortex
– Spinal neurons remain intact; muscles are
stimulated by reflex activity
– No voluntary control of muscles
Spinal Cord Trauma
• Flaccid paralysis—severe damage to the
ventral root or ventral horn cells
– Impulses do not reach muscles; there is no
voluntary or involuntary control of muscles
– Muscles atrophy