Transcript The Central Nervous System

Ch. 5
The Central Nervous System
Objectives
• Understand how the nervous system is organized
• Know the various cell types that are found in
nervous tissue and their function
• Identify and understand the function of the
various parts of the central nervous system
• Define and know what memory is
• Understand how a reflex arc works
Organization and Cells
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Neurons and Glial Cells
• Three functional classes of
neurons
– Afferent
• Four types of glial cells
– Astrocytes
• Spatial orientation and support
• Synapse formation
• sensory
– Thrombospondin
– Interneurons
– Efferent
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Repair and barrier formation
Nourish
Degradation of neurotransmitters
K+ regulation
• motor
– Oligodendrocytes
• myelination
– Microglia
• Immune protection
• Nerve growth factor
– Ependymal cells
• Internal lining of CNS
• Production of CSF
• Neural stem cells
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Protection and Nourishment
• Skull
• Oxygen
• Meninges
– neuroglobin
– Dura mater
– Arachnoid mater
– Pia mater
• Cerebral Spinal fluid
• Glucose
– Secreted by choroid plexus
– Rich in Na+
• Blood-brain barrier
– Anatomical and physiological
barrier
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Overview of CNS
• Brain and spinal cord
• Brain organization
– Forebrain
• Cerebrum
– Cerebral cortex
– Basal nuclei
• Diencephalon
– Thalamus
– Hypothalamus
– Cerebellum
– Brain stem
• Midebrain
• Pons
• medulla
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Cerebrum
• Composed of two hemispheres divided into four lobes
– Frontal
• Voluntary motor skills, speaking, though
– Parietal
• Somatosensory processing
– Temporal
• Auditory processing
– Occipital
• Visual processing
– Hemispherical specialization
• Left – logical and analytic
• Right – creative and artisitic
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Motor and Sensory Humunculi
• Use-dependent
competition
– Modifications
based on use
• Plasticity
– Ability to be
functionally
remodeled
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Electroencephalogram (EEG)
• Record of postsynaptic activity in cortical
neurons
– EPSPs or IPSPs
• Uses
– Brain dysfunction
– Brain death
– Sleep stages
Basal Nuclei and Diencephalon
• Basal Nuclei
– Regulatory inhibition of
motor control
– Divided into four regions of
grey matter
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Caudate nucleus
Putamen
Globus pallidus
Claustrum
– Associated with
Parkinson’s disease
• Diencephalon
– Thalamus
• Relay station for sensory
input
• Also involved in motor
control
– Hypothalamus
• Integrates and regulates
important homeostatic
functions
– Body temp
– Thirst
– Adenohypophysis control
The Limbic System
• Associated with learning and emotions
• Controls basic behavioral patterns
– Reward and punishment centers
– Motivation – ability to direct behavior to toward
specific goals
• Norepinephrine, dopamine, and seratonine
Learning and Memory
• The acquisition of
knowledge or skills as a
consequence of
experience or
instruction
• The storage of acuired
knowledge for later
recall
• Memory traces
– Neural changes
responsible for storage
of knowledge
Short-term Memory
• Involve temporary modifications in the function of
preexisting synapses
• Two types
– Habituation
• Decreased responsiveness to a repetitive indifferent stimulus
• Ca2+ channels do not readily open
– Sensitization
• Increased responsiveness to mild stimuli following a strong stimulus
• Ca2+ channel open and stay open longer
– K+ influx prevented
• Long term Potentiation
– Modifications due to increased use, connection gets stronger the more it is
used
– Transition to long term memory
Long-Term Memory
• Involves formation of new, permanent
synaptic connections
• Immediate early genes
– Play a role in memory consolidation
– Genes may encode for proteins that are necessary
for synapse formation, production of
neurotransmitters, answer not clear yet
Memory Traces in the Brain
• Hippocampus
– Declarative memory
• The “what’ memories of specific people, places, objects,
facts (semantic) and events (episodic)
• Cerebellum
– Procedural memories
• “how to” memories involving repetitive motor skills
• Prefrontal cortex
– Working memory
• Memory necessary to integrate information that is relevant
now
Cerebellum
• Balance and coordination
• Three regions
– Vestibulocerebellum
• Balance and controls eye movements
– Spinocerebellum
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• Enhances muscle tone and coordinates voluntary
movements
– Cerebrocerebellum
• Plans and initiates voluntary activity by providing input to
cortical motor areas
– Procedural memory
Brain Stem
• Link between spinal cord and high brain
– Medulla, pons, midbrain
• 12 cranial nerves arise from brain stem
• Cardiac, respiratory, and digestive control centers
• Reticular formation (RAS)
• Regulates muscle reflexes involved with euilibrium and
posture
• House the sleep center
Spinal Cord
• Slender tube that extends from the brain stem
and goes through vertebral column
• Gives rise to 31 pairs of spinal nerves
– Cervical, thoracic, lumbar, sacral, coccygeal
• Grey matter core, white matter on the periphery
– White matter organized into tracts
• Begin and end in specific brain regions and transmit specific
information
Spinal Tracts
• Ascending tracts
– Carry sensory information
up
• Descending tracts
– Carry motor input down
• Horns of spinal cord
– Dorsal
• Synapse with sensory
neurons
– Ventral
• Cell bodies of motor
neurons
– Lateral
• Fibers supplying cardiac and
smooth muscle, glands
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Reflexes
• Response that occurs automatically without conscious
effort
– Basic reflexes
– Acquired reflexes
• Reflex arc
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Sensory receptor
Afferent pathway
Integrating center
Efferent pathway
Effector
• Please know reflexes described