The Central Nervous System
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Chapter 8 The Central Nervous System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
CNS
Consists of:
Brain. Spinal cord.
Receives input from sensory neurons. Directs activity of motor neurons. Association neurons maintain homeostasis in the internal environment.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Embryonic Development
Groove appears in ectoderm to fuse to form neural tube by 20th day after conception. Neural tube eventually forms the CNS. During 5th week, modified:
Forebrain: telencephalon and diencephalon. Midbrain: unchanged. Hindbrain: metencephalon and myelencephalon.
Part of ectoderm where fusion occurs becomes neural crest.
Neural crest forms ganglia of PNS.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Embryonic Development
(continued)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Embryonic Development
(continued)
Telencephalon grows disproportionately forming 2 the hemispheres of the cerebrum. Ventricles and central canal become filled with cerebral spinal fluid (CSF). CNS composed of gray and white matter.
Gray matter consists of neuron cell bodies and dendrites. White matter (myelin) consists of axon tracts.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebrum
Only structure of the telencephalon. Largest portion of brain (80% mass). Responsible for higher mental functions. Corpus callosum:
Major tract of axons that functionally interconnects right and left cerebral hemispheres.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebrum
(continued)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
Characterized by numerous convolutions.
Elevated folds: gyri.
Depressed groves: sulci.
Frontal lobe:
Anterior portion of each cerebral hemisphere. Precentral gyri:
Contains upper motor neurons. Involved in motor control.
Body regions with the greatest number of motor innervation are represented by largest areas of motor cortex.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
(continued)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
Parietal lobe:
(continued)
Primary area responsible for perception of somatesthetic sensation. Body regions with highest densities of receptors are represented by largest areas of sensory cortex.
Temporal lobe:
Contain auditory centers that receive sensory fibers from cochlea. Interpretation and association of auditory and visual information.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
Occipital Lobe:
(continued)
Primary area responsible for vision and coordination of eye movements.
Insula:
Implicated in memory encoding. Integration of sensory information with visceral responses. Coordinated cardiovascular response to stress.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Visualizing the Brain
X-ray computed tomography (CT):
Complex computer manipulations of data obtained from xray absorption by tissues of different densities.
Soft tissue.
Positron-emission tomography (PET):
Radioisotopes that emit positrons are injected into blood stream.
Collision of positron and electron result in emission of gamma rays.
Pinpoint brain cells that are most active.
Brain metabolism, drug distribution.
Magnetic resonance imaging (MRI):
Protons (H+) respond to magnetic field, which align the protons.
Emit a radio-wave signal when stimulated.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Electroencephalogram (EEG)
Measures synaptic potentials produced at cell bodies and dendrites.
Create electrical currents.
Used clinically do diagnose epilepsy and brain death.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
EEG Patterns
Alpha:
Recorded from parietal and occipital regions.
Person is awake, relaxed, with eyes closed.
Beta:
Strongest from frontal lobes near precentral gyrus.
Produced by visual stimuli and mental activity. Evoked activity.
13-25 cycles/sec.
Theta:
Emitted from temporal and occipital lobes.
Common in newborn. Adult indicates severe emotional stress.
10-12 cycles/sec.
5-8 cycles/sec.
Delta:
Emitted in a general pattern.
Common during sleep and awake infant. In awake adult indicate brain damage.
1-5 cycles/sec.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
EEG Sleep Patterns
2 types of EEG patterns during sleep:
REM (rapid eye movement):
Dreams occur. Low-amplitude, high-frequency oscillations. Similar to wakefulness (beta waves).
Non-Rem (resting):
High-amplitude, low-frequency waves (delta waves). Superimposed on these are sleep spindles:
Waxing and waning bursts of 7-14 cycles/sec. Last for 1-3 sec.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Basal Nuclei (basal ganglia)
Masses of gray matter composed of neuronal cell bodies located deep within white matter. Contain:
Corpus striatum:
Caudate nucleus. Lentiform nucleus:
Putman and globus pallidus.
Functions in the control of voluntary movements.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Lateralization
Cerebral dominance:
Specialization of one hemisphere.
Left hemisphere:
More adept in language and analytical abilities. Damage:
Severe speech problems.
Right hemisphere:
Most adept at visuospatial tasks. Damage:
Difficulty finding way around house.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Language
Broca’s area: Involves articulation of speech. In damage, comprehension of speech in unimpaired. Wernicke’s area: Involves language comprehension. In damage, language comprehension is destroyed, but speech is rapid without any meaning. Angular gyrus: Center of integration of auditory, visual, and somatesthetic information. Damage produces aphasias.
Arcuate fasciculus:
To speak intelligibly, words originating in Wernicke’s area must be sent to Broca’s area.
Broca’s area sends fibers to the motor cortex which directly controls the musculature of speech.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Emotion and Motivation
Important in the neural basis of emotional states are hypothalamus and limbic system. Limbic system:
Group of forebrain nuclei and fiber tracts that form a ring around the brain stem.
Center for basic emotional drives.
Closed circuit (Papez circuit): Fornix connects
hippocampus to hypothalamus, which projects to the thalamus which sends fibers back
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Emotion and Motivation
Areas or the hypothalamus and limbic system are involved in feelings and behaviors. Aggression:
Hypothalamus (feeding and satiety centers).
Sexual drive and behavior:
Amygdala and hypothalamus.
Feeding:
Amygdala and hypothalamus.
Fear:
(continued)
Hypothalamus and limbic system.
Goal directed behavior (reward and punishment):
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Memory
Short-term:
Medial temporal lobe:
Memory of recent events. Consolidates short term into long term memory.
Hippocampus is critical component of memory. Acquisition of new information, facts and events requires both the medial temporal lobe and hippocampus.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Long-Term Memory
Consolidation of short-term memory into longterm memory.
Requires activation of genes, leading to protein synthesis and formation of new synaptic connections.
Cerebral cortex stores factual information:
Altered postsynaptic growth of dendritic spines in area of contact.
Visual memories lateralized to left hemisphere. Visuospatial information lateralized to right hemisphere.
Prefrontal lobes:
Involved in performing exact mathematical calculations.
Complex, problem-solving and planning activities.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Long-Term Potentiation
Type of synaptic learning.
Synapses that are 1st stimulated at high frequency will subsequently exhibit increased excitability.
In hippocampus, glutamate is NT.
Requires activation of the NMDA receptors for glutamate. Glutamate and glycine or D-serine binding and partial depolarization are required for opening of channels for Ca2+ and Na+.
May also involve presynaptic changes:
Binding of glutamate to NMDA receptors and simultaneous depolarization, open receptor channels for Ca2+.
Ca2+ causes long-term potentiation in postsynaptic neuron, release of NO from postsynaptic neuron.
NO acts as a retrograde messenger, causing release of NT.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Neuronal Stem Cells in Learning and Memory
Neural stem cells:
Hippocampus has been shown to contain stem cells (required for longterm memory). Neurogenesis:
Cells that both renew themselves through mitosis and produce differentiated neurons and neuroglia.
Production of new neurons.
Indirect evidence that links neuogenesis in hippocampus with learning and memory.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Thalamus and Epithalamus
Thalamus:
Composes 4/5 of the diencephalon. Forms most of the walls of the 3rd ventricle. Acts as relay center through which all sensory information (except olfactory) passes to the cerebrum.
Lateral geniculate nuclei:
Medial geniculate nuclei:
Relay visual information. Relay auditory information.
Intralaminar nuclei:
Activated by many sensory modalities. Projects to many areas.
Promotes alertness and arousal from sleep.
Epithalamus contains:
Choroid plexus where CSF is formed. Pineal gland which secretes melatonin.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hypothalamus
Contains neural centers for hunger, thirst, and body temperature. Contributes to the regulation of sleep, wakefulness, emotions, sexual arousal, anger, fear, pain, and pleasure. Stimulates hormonal release from anterior pituitary. Produces ADH and oxytocin. Coordinates sympathetic and parasympathetic reflexes.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pituitary Gland
Posterior pituitary:
Hypothalamus produces releasing and inhibiting hormones that are transported to anterior pituitary. Regulate secretions of anterior hormones. Anterior pituitary: Regulates secretion of hormones of other endocrine glands.
Stores and releases ADH (vasopressin) and oxytocin.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Midbrain
Contains:
Corpora quadrigemina:
Superior colliculi:
Inferior colliculi:
Composed of ascending and descending fiber tracts.
Substantia nigra:
Relay centers for auditory information.
Cerebral peduncles:
Involved in visual reflexes.
Required for motor coordination.
Red nucleus:
Maintains connections with cerebrum and cerebellum.
Involved in motor coordination.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hindbrain
Metencephalon:
Pons:
Surface fibers connect to cerebellum, and deeper fibers are part of motor and sensory tracts. Contains several nuclei associated with cranial nerves V, VI, VII. Contains the apneustic and pneumotaxic respiratory centerss.
Cerebellum:
Receives input from proprioceptors. Participates in coordination of movement. Necessary for motor learning, coordinating different joints
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hindbrain
(continued)
Myelencephalon (medulla oblongata): All descending and ascending fiber tracts between spinal cord and brain must pass through the medulla.
Vasomotor center:
Controls autonomic innervation of blood vessels.
Cardiac control center:
Nuclei contained within the medulla include VIII, IX, X, XI, XII. Pyramids: Fiber tracts cross to contralateral side.
Regulates autonomic nerve control of heart.
Regulates respiration with the pons.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Reticular Formation
Reticular Formation: Complex network of nuclei and nerve fibers within medulla, pons, midbrain, thalamus and hypothalamus. Functions as the reticular activating system (RAS).
Non specific arousal of cerebral cortex to incoming sensory information.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ascending Spinal Tracts
Convey sensory information from cutaneous receptors, proprioceptors and visceral receptors to cerebral cortex. Sensory fiber tract decussation may occur in medulla or spinal cord.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Descending Spinal Tracts
Pyramidal (corticospinal) tracts descend directly without synaptic interruption from cerebral cortex to spinal cord.
Function in control of fine movements that require dexterity.
Reticulospinal tracts (extrapyramidal):
Influence movement indirectly.
Gross motor movement.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cranial and Spinal Nerves
Cranial nerves:
2 pairs arise from neuron cell bodies in forebrain. 10 pairs arise from the midbrain and hindbrain.
Roman numerals refer to the order in which the nerves are positioned from front of the brain to the back.
Most are mixed nerves containing both sensory and motor fibers.
Spinal nerves:
31 pairs grouped into 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and l coccygeal. Mixed nerve that separates near the attachment of the nerve to spinal cord.
Produces 2 roots to each nerve.
Dorsal root composed of sensory fibers. Ventral root composed of motor fibers.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Reflex Arc
Unconscious motor response to a sensory stimulus. Stimulation of sensory receptors evokes APs that are conducted into spinal cord.
Synapses with association neuron, which synapses with somatic motor neuron.
Conducts impulses to muscle and stimulates a reflex contraction.
Brain is not directly
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
CNS
Consists of:
Brain. Spinal cord.
Receives input from sensory neurons. Directs activity of motor neurons. Association neurons maintain homeostasis in the internal environment.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Embryonic Development
Groove appears in ectoderm to fuse to form neural tube by 20th day after conception. Neural tube eventually forms the CNS. During 5th week, modified:
Forebrain: telencephalon and diencephalon. Midbrain: unchanged. Hindbrain: metencephalon and myelencephalon.
Part of ectoderm where fusion occurs becomes neural crest.
Neural crest forms ganglia of PNS.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Embryonic Development
(continued)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Embryonic Development
(continued)
Telencephalon grows disproportionately forming 2 the hemispheres of the cerebrum. Ventricles and central canal become filled with cerebral spinal fluid (CSF). CNS composed of gray and white matter.
Gray matter consists of neuron cell bodies and dendrites. White matter (myelin) consists of axon tracts.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebrum
Only structure of the telencephalon. Largest portion of brain (80% mass). Responsible for higher mental functions. Corpus callosum:
Major tract of axons that functionally interconnects right and left cerebral hemispheres.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebrum
(continued)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
Characterized by numerous convolutions.
Elevated folds: gyri.
Depressed groves: sulci.
Frontal lobe:
Anterior portion of each cerebral hemisphere. Precentral gyri:
Contains upper motor neurons. Involved in motor control.
Body regions with the greatest number of motor innervation are represented by largest areas of motor cortex.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
(continued)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
Parietal lobe:
(continued)
Primary area responsible for perception of somatesthetic sensation. Body regions with highest densities of receptors are represented by largest areas of sensory cortex.
Temporal lobe:
Contain auditory centers that receive sensory fibers from cochlea. Interpretation and association of auditory and visual information.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Cortex
Occipital Lobe:
(continued)
Primary area responsible for vision and coordination of eye movements.
Insula:
Implicated in memory encoding. Integration of sensory information with visceral responses. Coordinated cardiovascular response to stress.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Visualizing the Brain
X-ray computed tomography (CT):
Complex computer manipulations of data obtained from xray absorption by tissues of different densities.
Soft tissue.
Positron-emission tomography (PET):
Radioisotopes that emit positrons are injected into blood stream.
Collision of positron and electron result in emission of gamma rays.
Pinpoint brain cells that are most active.
Brain metabolism, drug distribution.
Magnetic resonance imaging (MRI):
Protons (H+) respond to magnetic field, which align the protons.
Emit a radio-wave signal when stimulated.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Electroencephalogram (EEG)
Measures synaptic potentials produced at cell bodies and dendrites.
Create electrical currents.
Used clinically do diagnose epilepsy and brain death.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
EEG Patterns
Alpha:
Recorded from parietal and occipital regions.
Person is awake, relaxed, with eyes closed.
Beta:
Strongest from frontal lobes near precentral gyrus.
Produced by visual stimuli and mental activity. Evoked activity.
13-25 cycles/sec.
Theta:
Emitted from temporal and occipital lobes.
Common in newborn. Adult indicates severe emotional stress.
10-12 cycles/sec.
5-8 cycles/sec.
Delta:
Emitted in a general pattern.
Common during sleep and awake infant. In awake adult indicate brain damage.
1-5 cycles/sec.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
EEG Sleep Patterns
2 types of EEG patterns during sleep:
REM (rapid eye movement):
Dreams occur. Low-amplitude, high-frequency oscillations. Similar to wakefulness (beta waves).
Non-Rem (resting):
High-amplitude, low-frequency waves (delta waves). Superimposed on these are sleep spindles:
Waxing and waning bursts of 7-14 cycles/sec. Last for 1-3 sec.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Basal Nuclei (basal ganglia)
Masses of gray matter composed of neuronal cell bodies located deep within white matter. Contain:
Corpus striatum:
Caudate nucleus. Lentiform nucleus:
Putman and globus pallidus.
Functions in the control of voluntary movements.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cerebral Lateralization
Cerebral dominance:
Specialization of one hemisphere.
Left hemisphere:
More adept in language and analytical abilities. Damage:
Severe speech problems.
Right hemisphere:
Most adept at visuospatial tasks. Damage:
Difficulty finding way around house.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Language
Broca’s area: Involves articulation of speech. In damage, comprehension of speech in unimpaired. Wernicke’s area: Involves language comprehension. In damage, language comprehension is destroyed, but speech is rapid without any meaning. Angular gyrus: Center of integration of auditory, visual, and somatesthetic information. Damage produces aphasias.
Arcuate fasciculus:
To speak intelligibly, words originating in Wernicke’s area must be sent to Broca’s area.
Broca’s area sends fibers to the motor cortex which directly controls the musculature of speech.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Emotion and Motivation
Important in the neural basis of emotional states are hypothalamus and limbic system. Limbic system:
Group of forebrain nuclei and fiber tracts that form a ring around the brain stem.
Center for basic emotional drives.
Closed circuit (Papez circuit): Fornix connects
hippocampus to hypothalamus, which projects to the thalamus which sends fibers back
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Emotion and Motivation
Areas or the hypothalamus and limbic system are involved in feelings and behaviors. Aggression:
Hypothalamus (feeding and satiety centers).
Sexual drive and behavior:
Amygdala and hypothalamus.
Feeding:
Amygdala and hypothalamus.
Fear:
(continued)
Hypothalamus and limbic system.
Goal directed behavior (reward and punishment):
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Memory
Short-term:
Medial temporal lobe:
Memory of recent events. Consolidates short term into long term memory.
Hippocampus is critical component of memory. Acquisition of new information, facts and events requires both the medial temporal lobe and hippocampus.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Long-Term Memory
Consolidation of short-term memory into longterm memory.
Requires activation of genes, leading to protein synthesis and formation of new synaptic connections.
Cerebral cortex stores factual information:
Altered postsynaptic growth of dendritic spines in area of contact.
Visual memories lateralized to left hemisphere. Visuospatial information lateralized to right hemisphere.
Prefrontal lobes:
Involved in performing exact mathematical calculations.
Complex, problem-solving and planning activities.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Long-Term Potentiation
Type of synaptic learning.
Synapses that are 1st stimulated at high frequency will subsequently exhibit increased excitability.
In hippocampus, glutamate is NT.
Requires activation of the NMDA receptors for glutamate. Glutamate and glycine or D-serine binding and partial depolarization are required for opening of channels for Ca2+ and Na+.
May also involve presynaptic changes:
Binding of glutamate to NMDA receptors and simultaneous depolarization, open receptor channels for Ca2+.
Ca2+ causes long-term potentiation in postsynaptic neuron, release of NO from postsynaptic neuron.
NO acts as a retrograde messenger, causing release of NT.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Neuronal Stem Cells in Learning and Memory
Neural stem cells:
Hippocampus has been shown to contain stem cells (required for longterm memory). Neurogenesis:
Cells that both renew themselves through mitosis and produce differentiated neurons and neuroglia.
Production of new neurons.
Indirect evidence that links neuogenesis in hippocampus with learning and memory.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Thalamus and Epithalamus
Thalamus:
Composes 4/5 of the diencephalon. Forms most of the walls of the 3rd ventricle. Acts as relay center through which all sensory information (except olfactory) passes to the cerebrum.
Lateral geniculate nuclei:
Medial geniculate nuclei:
Relay visual information. Relay auditory information.
Intralaminar nuclei:
Activated by many sensory modalities. Projects to many areas.
Promotes alertness and arousal from sleep.
Epithalamus contains:
Choroid plexus where CSF is formed. Pineal gland which secretes melatonin.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hypothalamus
Contains neural centers for hunger, thirst, and body temperature. Contributes to the regulation of sleep, wakefulness, emotions, sexual arousal, anger, fear, pain, and pleasure. Stimulates hormonal release from anterior pituitary. Produces ADH and oxytocin. Coordinates sympathetic and parasympathetic reflexes.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pituitary Gland
Posterior pituitary:
Hypothalamus produces releasing and inhibiting hormones that are transported to anterior pituitary. Regulate secretions of anterior hormones. Anterior pituitary: Regulates secretion of hormones of other endocrine glands.
Stores and releases ADH (vasopressin) and oxytocin.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Midbrain
Contains:
Corpora quadrigemina:
Superior colliculi:
Inferior colliculi:
Composed of ascending and descending fiber tracts.
Substantia nigra:
Relay centers for auditory information.
Cerebral peduncles:
Involved in visual reflexes.
Required for motor coordination.
Red nucleus:
Maintains connections with cerebrum and cerebellum.
Involved in motor coordination.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hindbrain
Metencephalon:
Pons:
Surface fibers connect to cerebellum, and deeper fibers are part of motor and sensory tracts. Contains several nuclei associated with cranial nerves V, VI, VII. Contains the apneustic and pneumotaxic respiratory centerss.
Cerebellum:
Receives input from proprioceptors. Participates in coordination of movement. Necessary for motor learning, coordinating different joints
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hindbrain
(continued)
Myelencephalon (medulla oblongata): All descending and ascending fiber tracts between spinal cord and brain must pass through the medulla.
Vasomotor center:
Controls autonomic innervation of blood vessels.
Cardiac control center:
Nuclei contained within the medulla include VIII, IX, X, XI, XII. Pyramids: Fiber tracts cross to contralateral side.
Regulates autonomic nerve control of heart.
Regulates respiration with the pons.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Reticular Formation
Reticular Formation: Complex network of nuclei and nerve fibers within medulla, pons, midbrain, thalamus and hypothalamus. Functions as the reticular activating system (RAS).
Non specific arousal of cerebral cortex to incoming sensory information.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ascending Spinal Tracts
Convey sensory information from cutaneous receptors, proprioceptors and visceral receptors to cerebral cortex. Sensory fiber tract decussation may occur in medulla or spinal cord.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Descending Spinal Tracts
Pyramidal (corticospinal) tracts descend directly without synaptic interruption from cerebral cortex to spinal cord.
Function in control of fine movements that require dexterity.
Reticulospinal tracts (extrapyramidal):
Influence movement indirectly.
Gross motor movement.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cranial and Spinal Nerves
Cranial nerves:
2 pairs arise from neuron cell bodies in forebrain. 10 pairs arise from the midbrain and hindbrain.
Roman numerals refer to the order in which the nerves are positioned from front of the brain to the back.
Most are mixed nerves containing both sensory and motor fibers.
Spinal nerves:
31 pairs grouped into 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and l coccygeal. Mixed nerve that separates near the attachment of the nerve to spinal cord.
Produces 2 roots to each nerve.
Dorsal root composed of sensory fibers. Ventral root composed of motor fibers.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Reflex Arc
Unconscious motor response to a sensory stimulus. Stimulation of sensory receptors evokes APs that are conducted into spinal cord.
Synapses with association neuron, which synapses with somatic motor neuron.
Conducts impulses to muscle and stimulates a reflex contraction.
Brain is not directly
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