Chapter 5: The Central Nervous System Flashcards
Central Nervous System (CNS)
- brain and spinal cord
Peripheral Nervous System (PNS)
- nerve fibers
- afferent and efferent divisions
Enteric Nervous System (ENS)
- nerves network of the digestive tract
Divisions of the Efferent Nervous System
Somatic Nervous System
- fibers of the motor neurons that supply the skeletal muscles
Autonomic Nervous System
- fibers that innervate smooth muscle, cardiac muscle, and glands
- is further divided into the sympathetic and parasympathetic nervous system
Neurons Functional Classes
- the functional classes
Afferent
Efferent
Interneurons
Glial Cells of Neruons
- support interneurons physically, metabolically, and functionally
- astrocytes, oligodendrocytes, microglia, and ependymal cells
Protection and Nourishment of the Brain
- major features protect the CNS from injury
- cranium and vertebral column
- meninges
- cerebrospinal fluid
- blood-brain barrier
Three Meningeal Membranes
- wrap, protect, and nourish the CNS
Dura Mater
Arachnoid Mater
Pia Mater
Fluids of the Brain
- brain floats in its own special cerebrospinal fluid
- surrounds and cushions the brain and spinal cord
- highly selective blood-brain barrier regulates exchanges between the blood and brain
- shields from harmful changes
Nourishment of the Brain
- brain depends on constant delivery of oxygen and glucose by the blood
- cannot produce ATP without O2
- brain damages results if deprived of O2
Components of the Brain
- brain stem
- cerebellum
- forebrain
- diencephalon
- hypothalamus
- thalamus
- cerebrum
- basal nuclei
- cerebral cortex
Cerebral Cortex
- divided into right and left cerebral hemispheres
- connected by the corpus collosum
- is an outer shell of gray matter covering an inner core of white matter
Gray Matter: CNS computers
White Matter: wires that connect the computers
Cerebral cortex and Neural Networks
- neurons in different regions of the cerebral cortex may fire in rhythmic synchrony
- neural network or assembly
- cerebral cortex is organized into layer and functional columns
- functional differences result from different layering patterns and different input-output connections
Lobes of the Cerebral Cortex
- occipital
- temporal
- parietal
- frontal
Parietal Lobe
- somatosensory processing
- sensations from the surface of the body, such as touch, pressure, heat, cold, and pain
Frontal Lobe
- primary motor cortex which controls the skeletal muscles
- stimulation of different areas of the primary motor cortex brings about movement in different regions of the body
Cerebral Cortex and Motor Control
- higher motor areas are also important in motor control
- supplementary motor area
- premotor cortex
- posterior parietal cortex - somatotopic maps vary slightly between individuals and are dynamic, not static
- use-dependent competition
Plasticity and Language in the Cortex
- brain can be remodeled in response to varying demands
Plasticity: ability to change or be functionally remodeled in response to demands - different regions of the cortex control different aspects of language
- Broca’s area (speaking) and Wernicke’s area (comprehension)
- language disorders
- aphasias, speech impediments, and dyslexia
Specialization in the Cortex
- association of the cortex are involved in many higher functions
prefrontal association cortex
parietal-temporal occipital association cortex
limbic association cortex - cerebral hemispheres have some degree of specialization
Left Cerebral Hemisphere: logical, analytical, sequential, and verbal tasks
Right Cerebral Hemisphere: non-language skills
Activity in the Cerebral Cortex
- most active when mind wanders
- more active during resting states than during focused
Basal Nuclei (basal ganglia)
- consists of several masses of gray matter
- located deep within the cerebral white matter
- basal nuclei play an important inhibitory role in motor control
- inhibiting muscle tone, maintaining purposeful motor activity, suppressing useless or unwanted movement, and monitoring and coordinating slow, sustained contractions
Thalamus and Hypothalamus
Thalamus
- sensory relay for preliminary processing of sensory input
Hypothalamus
- regulates many homeostatic functions
- collection of specific nuclei and associated fiber that lie beneath the thalamus
- integrating center for many important homeostatic functions
Eight Functions of the Hypothalamus
- Provides subconscious control of skeletal muscle
- Controls autonomic function
- Coordinates activities of nervous and endocrine systems
- Secretes hormones
- antidiuretic hormone (ADH) by supraoptic nucleus
- oxytocin (OT;OXT) by paraventricular nucleus - Provides emotions and behavioral drives
- the feeding center (hunger)
- the thirst center (thirst) - Coordinates voluntary and autonomic functions
- Regulates body temperature
- preoptic area of hypothalamus - Controls circadian rhythms (day-night cycles)
- suprachiasmatic nucleus
The Limbic System
- functional system
- consists of a ring of forebrain structures that surround the brain stem
- interconnected by intricate neuron pathways
- plays a role in emotion
- subjective emotional feelings and moods plus the overt physical responses associated with these feelings
- participate in controlling basic behavioral patterns with higher cortex
- motivated behaviors are goal-directed
- reward and punishment centers
Emotion, Behavior, and Neurotransmitters
- norepinephrine, dopamine, and serotonin are neurotransmitters in pathways for emotions and behavior
- underlying neurophysiological mechanisms responsible for the psychological observations of emotions and motivated behavior largely remain a mystery
Classes of Antidepressants
- Selective Serotonin Reuptake Inhibitors (SSRIs)
- Serotonin Norepinephrine Reuptake Inhibitors (SNRIs)
Learning and Memory
- learning is the acquisition of knowledge as a result of experiences
- memory is laid down in stages
Short-term memory
Long-term memory
Working memory - amnesia is a lack of memory
Retrograde and anterograde
High-Order Function
- memory
- fact memories (specific bits of info)
- skill memories
Learned motor behaviors
Incorporated at unconscious level with repetition
Programmed behaviors stored in appropriate area of brain stem
Complex are stored and involve motor patterns in the basal nuclei, cerebral cortex, and cerebellum
Short-term and Long-term Memory
Short-Term
- involves transient modifications in preexisting synapse function
Long-term
- involves relatively permanent functional or structural changes between existing neurons in the brain
Memory Traces
- hippocampus and declarative memories
Alzheimer’s Disease: patients marked by damage to the hippocampus - cerebellum and procedural memories
- prefrontal cortex and working memory
Cerebellum
- highly folded
- lies underneath the cortex’s occipital lobe
- importance in balance, planning, and executing voluntary movement
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
Brain Stem
- vital link between the spinal cord and higher brain regions
- consists of medulla, pons, and midbrain
- area where most cranial nerves arise
- contains center that control cardiovascular, respiratory, and digestive function
- regulates equilibrium and postural reflexes
- controls overall degree of cortical alertness
- centers that govern sleep are housed within the brain stem and hypothalamus
Consciousness
- refers to awareness of one’s existence, thoughts and surroundings
- normal states of consciousness are wakefulness and sleep
- sleep-wake cycle
- waking state
Brain Stem and Synaptic Activity
- an electroencephalogram (EEG) is a record of postsynaptic activity in cortical neurons
- extracellular current flow arising from electrical activity within the cerebral cortex can be detected
- alpha, beta, theta, and delta waves
Alpha Waves
- found in healthy, awake adults at rest with eyes closed
Beta Waves
- higher frequency
- found in adults concentrating or mentally stressed
Theta Waves
- found in children
- found in intensely frustrated adults
- may indicate brain disorder in adults
Delta Waves
- during sleep
- found in awake adults with brain damage
Sleep
- the sleep-wake cycle is controlled by interactions among three neural systems
Arousal system
Slow-wave sleep center
Paradoxical sleep center - function of sleep is unclear
- sleep is by the brain and for the brain
- active process consisting of alternating periods of slow-wave and paradoxical sleep
- EEG and behavioral patterns during sleep
Impairment
Synchronization
- pacemaker mechanism
- synchronizes electrical activity between hemispheres
Brain damage can cause desynchronization
- seizure
- is a temporary cerebral disorder
- changes the electroencephalogram
- symptoms depend on regions affected
- impaired states of consciousness are associated with minimal or no awareness
Minimally conscious state
Vegetative state
Coma
ConcussionSpinal Cord
- long, slender cylinder of nerve tissue
- extends from the brain stem
- extends through the vertebral canal and is connected to the spinal nerves
- enclosed by the protective vertebral column
- white matter is organized into tracts
- bundles of nerve fibers with similar function
- ascending, descending, ventral spinocerebellar, and ventral corticospinal tracts
Neurons and Fibers
- each horn of the spinal cord gray matter houses a different type of neuronal cell body
- dorsal, ventral, and lateral horns
- spinal nerves carry both afferent and efferent fibers
- connect with each side of the spinal cord by dorsal root and a ventral root
Spinal Cord and Innate Reflexes
- reflex arc
- sensory receptor
- afferent pathway
- integrating center
- efferent pathway
- effector organ
In what ways are the physiological functions of stimulants and antidepressants similar? How do they differ physiologically?
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Why do most people dream every night?
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Based on your knowledge of the brain, what would you tell a patient about the cause of his or her headache?
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