Organization of the CNS Flashcards
Are exciteable and conductive
Neurons
Provide output to muscles, glands (PNS), and other neurons (CNS)
Neuron Terminals
Generate action potentials
Neuronal Axons
Insulates axons and increases conduction velocity
Myelin
The “trigger zone” of the neuron
Axon Hillock
Carry sensory information from the periphery
-Associated with receptors
PNS Afferents
The cells bodies of PNS afferents are usually in the
Dorsal root ganglia
Carry (usually) motor signals to skeletal and smooth muscle
PNS Efferents
The cell bodies of PNS efferents are in the
Central Nervous System
CNS neurons are mostly
Interneurons
Interneurons form connections within the
CNS
Connect to neurons in the immediate region
Local Interneurons
Project to more distant areas of the CNS
Projection interneurons
Receiving areas of neurons can be large or small and vary in dimension. More inputs to a neuron means more
Convergence
Number of outputs from axon terminals reflects
Divergence
Convergence of information enables integration of
Inhibitory and exciteatory information
What are clusters of cell bodies called in the
- ) CNS
- ) PNS
- ) Nucleus
2. ) Ganglia
Is mainly cell bodies and synapses
Grey matter
Are myelinated axons
White matter
Grey and white matter are reversed in the
Spinal cord
In the basal ganglia, diencephalon and brainstem, the combined ratio of glial cells to neurons is is
11.35
What are the three non-neuronal cells in the CNS?
Ependymal, Macroglia, and Microglia
Line the fluid-filled cavities of the brain (ventricles) and the central canal of the spinal cord
Ependymal Cells
What are the two types of macroglia?
Astrocytes and oligodendrocytes
Phagocytes, active after injury, infection or disease in the CNS
-Produce growth factors
Microglia (5-20% of glial population)
Form the glial membrane
-an important component of Blood-brain barrier
Astrocytes
In the blood-brain barrier, control K+ and modulate the vascular tone in the brain, controlling cerebral blood flow
Astrocytes
Astrocytes remove K+ from extracellular fluid at nodes of Ranvier during
Action potentials
Astrocytes remove neurotransmitters from synaptic clefts, which prevents
Glutamate excitotoxicity
Communicate through gliotransmitters(D-serine, glutamate, ATP) in response to adjacent synaptic activity
Astrocytes
Produce neurotropic factors and also produce scar tissue in response to CNS injury
Astrocytes
Changes in neurons and pathways in response to experience
Neuroplasticity
Comprised of the brain and spinal cord
CNS
Comprised of the spinal nerves, peripheral nerves, and cranial nerves
PNS
Components:
- Motor efferents to muscle
- Autonomic efferents to viscera*
- Sensory afferents from skin, muscle, joints, visceral receptors
Spinal nerves
Sends motor efferents to muscle and autonomic efferents to viscera
Spinal nerves
In the thoracic and upper lumbar regions, spinal nerves are
Sympathetic
In the sacral region, spinal nerves are
Parasympathetic
Form peripheral nerves made up of connective tissue and fascicles with afferents and efferents
Spinal Nerves
Fluid filled cavities in every region of the central nervous system Cerebrospinal Fluid (CSF)
Ventricles
The spinal cord extends from the
Foramen magnum to the L1 vertebral body
Has white matter pathways
Spinal cord
For the long tracts, the sensory pathways are made up of
3 Neurons
Spinal cord lesions that interrupt motor pathways can cause
Paralysis
What are the two types of spinal cord reflex circuits?
- ) Simple (monosynaptic): Stretch reflex
2. ) Complex (multiple synapses): Flexor withdrawal reflex
The “little brain” dorsal to the brainstem
Cerebellum
The cerebellum functions in
Movement and balance
Damage to the cerebellum causes
Ataxia (Disordered movement)
What are the three parts of the brainstem?
- ) Medulla
- ) Pons
- ) Midbrain
Most of the cranial nerves exit on the
Ventral surface of brainstem
The ventral surface of the brainstem contains the
Cerebral peduncles and pyramid
The cerebral peduncle is located in the
Midbrain
The pyramid is located in the
Medulla
The transition between the spinal cord and brainstem
Medulla
Which 4 cranial nerves are part of the medulla?
IX, X, XI, and XII
Responsible for the regulation of body homeostasis, such as HR, respiration, vasomotor tone, and gastric secretions
Nuclei of the medulla
Damage to the medulla =
Death
Vomiting, coughing, sneezing, swallowing, and gagging are reflexes related to the
Medulla
Which 4 cranial nerves are part of the pons?
V, VI, VII, and VIII
The pons is responsible for
Balance, sound localization, eye movement, and coordination
Is a large pathway into the cerebellum
Pons
Located at the top of the brainstem
Midbrain (mesencephalon)
Which 2 cranial nerves are part of the midbrain?
CN III and IV
The nuclei of the midbrain are responsible for
Visual reflexes and motor control
Has dopamine projections to the cortical areas of the cortex
Midbrain
These dopamine projections are significant for
Movement and “reward”
Has a net-like appearance and passes through the core of the brianstem
Reticular formation
The reticular formation includes projections to the
Cortex or spinal cord
Rostral projections from the pons and midbrain (pontomesencephalic)
Reticular activating system
The reticular activating system projections controls
Attention, arousal, sleep, and wakefulness
Can lead to loss of consciousness and Coma
Lesions of the reticular formation
Major relay station for all inputs to the cortex
-examples: sensory (except olfactory), motor areas
Thalamus
Projections to the cortex are called
Thalmocortical radiations
The diencephalon is made up of the
Thalamus, hypothalamus, epithalamus, and subthalamus
The cerebral hemisphere is called the
Telencephalon
The elevations in the cerebral hemisphere
Gyri
The depressions in the cerebral hemisphere
Sulci
The deepest depressions are called
Fissures
What are the two major sulci?
Sylvian fissure and Central sulcus
What are the 5 lobes of the brain?
Frontal, Parietal, occipital, temporal, and limbic
Responsible fro planning, organizing, and controlling behavior
Frontal lobe
Responsible for Sensory perception of self and the world
Parietal lobe
The occipital lobe is responsible for
Visual processing
Responsible for auditory (superior), visual (middle) and memory (medial) processing
Temporal lobe
Responsible for emotional processing and memory consolidation
Limbic lobe
The first cortical receiving area for sensory information
Primary sensory cortex
The last cortical area to project to the spinal cord and brainstem
-Right controls/perceives left; left controls/perceives right
Primary motor cortex
The primary cortex is divided into primary sensory and primary motor cortex by the
Central sulcus
Sensory “fields” are represented in an orderly manner within the
Primary cortex
Responsible for higher-order processing, e.g. perceptions, judgments, organization, calculations, language
Association Cortex
Responsible for emotion and memory
Limbic System
Part of the limbic system that is important for long-term memory formation
Hippocampus
The part of the limbic system that is important for Fear-learning
Amygdala