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58 Cards in this Set
- Front
- Back
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Nervous System Organization
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• Central nervous
system (CNS) – brain, spinal cord • Peripheral nervous system (PNS) – Afferent division – information to CNS – Efferent division – away from CNS • Somatic (volitional) • Autonomic (automatic/ involuntary) • Sympathetic • Para-sympathetic |
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Afferent neurons
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Inform CNS about
external /internal conditions |
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Efferent neurons
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instructions from
CNS to effector organs (muscles, glands) |
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Interneurons
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– Within CNS
– Integrate afferent information , formulate efferent response – Higher mental functions |
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Most neural cells are interneurons
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- massive amount, vary per region
- information processing - filtered - storage - output |
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Neuroglia (glial cells)
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• Physically, metabolically, and functionally support
interneurons (90% of CNS cells) • Major types (astrocytes, oligodendrocytes/Schwann cells, microglia, ependymal cells) |
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Astrocytes
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– “Glue” of CNS – holds neurons together
– Guide neurons during fetal development – Aids establishment of blood-brain barrier (BBB) – Repair brain injuries, neural scar formation – Neurotransmitter activity – Take up excess K+ from brain ECF – Enhance synapse formation and modify synaptic transmission |
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Ependymal cells
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– Line internal, fluid-filled
cavities of the CNS – In ventricles of brain, help form and circulate cerebrospinal fluid |
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Microglia
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– Immune cells of CNS
(macrophages) – Release low levels of growth factors/cytokines facilitate neuronal/ glial growth |
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Oligodendrogytes/Schwann
cells |
myelin sheaths around
axons in CNS/PNS |
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CNS Protection
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• Cranial cavity (primary protection)
• Meninges – protective, nourishing membranes –(closely approximated) – Dura mater – tough, fibrous CT, houses some dural or venous cavities – Arachnoid mater - vascularized, above subarachnoid space – filled with cerebrospinal fluid (CSF) – Reabsorbed via arachnoid villi (protrude outward into dural sinuses) – Pia mater – closely adhered to CNS, vascular • CSF - cushioning, nutritional fluid –; Formed primarily by choroid plexuses • Blood-brain barrier limits access of blood-borne materials into brain tissue |
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Blood-Brain Barrier (BBB)
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• Limits chemical fluctuations, entry of potential harmful
substances in blood • Prevents/limits hormones/drugs from acting on CNS • Cells joined by tight junctions – certain areas exemp |
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Brain Anatomy
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• Brain stem (midbrain, pons, medulla)
• Cerebellum • Forebrain – Diencephalon • Hypothalamus • Thalamus • Telencephalon • Basal nuclei (caudate/putamen) • Cortex |
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Brain Stem
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• Major areas (midbrain/pons/medulla)
• Cranial nerves/nuclei (III-XII) • Autonomic regulation – regulate heart and blood vessel function, respiration, GI functions |
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Midbrain
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• Cranial nuclei III-IV
• Cerebral peduncles –cerebrum to lower levels • Superior/inferior colliculi • Substantia nigra (dopamine – basal ganglia) • Red nucleus – rubrospinal tracts (lower species) • Reticular formation starts - large, diffuse network |
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Pons
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• Relay area
• Pontine nuclei – projection to cerebellum • Cranial nuclei (V-VII) |
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Medulla
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• Pyramidal decussation
• Cranial nuclei – VIII-XII • Visceral motor function (CV, resp.) • Upper/lower airway reflexes |
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Brain Stem Autonomic regulation
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regulate heart and blood vessel function
respiration GI functions |
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Reticular Formation
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• Dorsal brainstem (clustered neurons/netlike fibers)
– Modulatory (serotonin, norepinephrine, cholinergic, dopamine) – Ascending integration of sensory input, limbic system (mood/emotion/pain), sleep-arousal – Descending - Muscle reflexes, equilibrium/posture, visceral modulation |
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Cerebellum
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• Interlimb coordination, balance,
specific types of motor learning, motor planning and execution • Attached at top rear portion of brain stem • Maintains proper position of the body in space • Subconscious coordination of motor activity (movement) • Key role in learning skilled motor tasks |
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Vestibulocerebellum
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balance and eye movements
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Spinocerebellum
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muscle “tone” (partially), comparator
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Cerebrocerebellum
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• Plays role in planning and
initiating voluntary activity by providing input to cortical motor areas • Stores procedural memories |
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Diencephalon (Thalamus)
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– primitive sensory processing
– “relay station”, processing towards cortex – direct attention to stimuli of interest (brainstem and cortex) – crude awareness of sensation (cannot distinguish location/intensity) |
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Diencephalon (Hypothalamus)
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– Controls homeostatic functions
important in maintaining stability of internal environment – Functions (body temperature, food/water intake, urine output, hormonal secretion (many), major ANS center, emotional/behavioral, sleep/wake cycle |
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Limbic System
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• Portions of hypothalamus and other forebrain structures
(ring of gray matter on medial cerebral hemispheres) – Emotion (behavior/memory/learning) – Reward and fear systems – Motivation/learning • Specific electrical stimulation of nuclei within amygdala produce emotional behaviors • Subcortical structures |
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Cerebrum/Telencephalon
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• Makes up about 80% of total brain
weight (largest portion of brain) • Inner core houses basal nuclei • Outer surface is highly convoluted cerebral cortex – Highest, most complex integrating area of the brain – Plays key role in most sophisticated neural functions |
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Basal nuclei/basal ganglia
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• Initially thought to be solely motor functions (gross
motor/oculomotor) • Cognitive/learning • Emotion/limbic system |
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Schematic of BG organization
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• Input:
– Caudate and putamen (together, the striatum) • Intrinsic: – Subthalamic nucleus (STN) – External segment of globus pallidus (GPe) • Output: – Substantia nigra pars reticulata (SNr) – Internal segment of globus pallidus (GPi) • Neuromodulator: – Substantia nigra pars compacta (SNc) |
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Cerebral Cortex
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• Each half of cortex divided into four major lobes
– Occipital lobe – initial visual processing – Temporal lobe – initial sound sensation – Parietal lobe – somatosensory, sensory integration – Frontal lobe – volitional, speech, cortical/logical processing |
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Cerebral Cortical Layers
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• 6 well-defined layers
– I – molecular layer mostly axons – II – External granule layer (stellate cells) – III – external pyramidal layer (pyramidal – to subcortical) – IV – Internal granule layer – V – internal pyramidal (giant pyramidal cells - descending) – VI – multiform layer (receive thalamic input, project other lamina) – V-VI – stellate cell – to subcortical regions |
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Primary motor cortex
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– commands to lower levels for
initiation/ modulation of movement to contralateral side – specific trajectory planning – Motor programs located here or at interneuron networks |
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Primary somatosensory cortex
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– provides sensory information for
movement planning/initiation – modulation of ongoing movement |
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“Motor homunculus”
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Location/amount of
cortex devoted to output to muscles |
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“Sensory homunculus”
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Location/amount of
cortex devoted to sensory input from periphery |
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Premotor area
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– involved in goal-directed movements
– Activity prior to visually-guided movements |
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Supplementary motor area
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– ensures correct sequencing of movement (order of movement)
• biomechanical constraints • task performed • external conditions – Activity prior to internally-guided movements |
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Posterior parietal cortex
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– encodes complex sensory information
– internal sensory representation |
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Primary areas of cortical
specialization for language |
– Broca’s area – speech output
– Wernicke’s area • language comprehension • formulating coherent patterns of speech |
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Processing
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1) Integration visual/auditory,
association cortices 2) Information to Wernicke’s area (choice/sequence of words are formulated) 3) Info to Broca’s area, message to sound pattern 4) Program conveyed to primary motor cortex to allow motor output |
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Left cerebral
hemisphere |
– Logical, analytic,
sequential, \verbal tasks • Math, • language forms • philosophy |
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Right cerebral
hemisphere |
– Nonlanguage skills
• Spatial perception • artistic/ musical talents |
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Spinal Cord
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• Extends from brain stem through vertebral canal
– 31 pairs of spinal nerves from SC through spaces between arches of adjacent vertebrae – named for region it exists (C1-7 above vertebral segment, C8 and all else below (C1-8, T1-12, L1-5, S1-5, 1 coccygeal) |
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Functions
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– Communication between brain and PNS (somatic and autonomic) –
descending/ascending pathways – Incoming sensory input/motor output from most of body (except BS – Integration of sensorimotor information (simple reflex to complex motor behaviors, integration from descending input) |
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Reflex
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– Stereotypical response to similar afferent input
• Not hardwired; modulated by other neural inputs/pathways • Any response that occurs automatically without conscious effort – Occurs locally at SC or BS, transmit through multiple INs, ascending/descending tracts |
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Two types
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- Simple (basic, unlearned, genetic)
- Acquired (conditioned) |
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Five basic components
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- Receptor
- Afferent pathway - Integrating center - Efferent pathway - Effector |
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PNS
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• Communication to/from CNS with rest of body
Afferent -Sensory transduction/ pathways -Special Senses Efferent -Somatic nervous system -Autonomic nervous system |
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PNS: Efferent Division
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• Communication link by which CNS controls
activities of muscles and glands • Two divisions of PNS – Autonomic nervous system (ANS) • Involuntary branch of PNS • Innervates cardiac muscle, smooth muscle, most exocrine glands, some endocrine glands, and adipose tissue – Somatic nervous system • Subject to voluntary control • Innervates skeletal muscle |
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Somatic Nervous System
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• Axons of MNs originate in SC or BS- end on skeletal
muscle • MN terminal releases ACh, stimulates muscle contraction • MNs are final common pathway – All motor commands act through MNs to allow movement – Controlled by multiple areas (SC, BS, sensorimotor cortex, basal ganglia/cerebellum) |
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MN to muscle transmission
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• AP initiation/propagation from MN
down axon • Neuromuscular junction – Muscle fiber, terminal button (“motor end plate”) – Ach release • Presynaptic vesicular • Postsynaptic intracellular – Endplate potentials • nicotinic receptors (Na/K flow) • Inflow of sodium and potassium • AP propagated along muscle fiber – Ach breakdown – Ach esterase |
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Autonomic Nervous System
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• Autonomic nerve pathway
– Extends from CNS to an innervated organ • Ganglion = neuronal cell bodies in the PNS • Nuclei = neuronal cell bodies in the PNS CNS – Two-neuron chain • Preganglionic fiber (synapses with cell body of second neuron) • Postganglionic fiber (innervates effector organ) |
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Division usually opposite...
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Some exceptions:
– most arterioles and veins receive only sympathetic – Sweat glands only sympathetic – Salivary glands -both ANS divisions, both stimulate salivary secretion |
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Viscera
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innervated by symp and para (usually
produce opposite effects) |
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Dual innervation allows
control over activity |
– Sympathetic system
• dominates in emergency or stressful situations • Preparation for strenuous physical activity – Parasympathetic system • dominates in quiet, relaxed situations • body-maintenance activities (digestion) |
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Adrenal
medulla |
• Adrenal medulla is a
modified symp nervous system – Minimal postganglionic fibers – Preganglionic fiber initiates hormonal secretion • 20% norepinephrine • 80% epinephrine (adrenaline) • Broadcast vs. localized |
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Autonomic Neurotransmitter
Receptors |
– Mostly modulatory (effector organ)
– Localized – varicosities, broadcast – adrenal medulla – Cholinergic receptors – bind to ACh • Nicotinic receptors – cell bodies of autonomic ganglia • Muscarinic receptors – found on effector cell membranes – Adrenergic receptors – bind to norepinephrine and epinephrine • Alpha (α) receptors - -1- vessel constriction, contraction of smooth muscle, - 2 - relaxation in the digestive tract, inhibitory? Beta (β) receptors - Found in the heart, increases contractility and rate - Found in the arterioles and airways, dilator |
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Regions of CNS Involved in Control of
Autonomic Activities |
• Prefrontal association complex - emotional expression
characteristic of individual’s personality • Hypothalamus – integrating autonomic, somatic, and endocrine responses accompanying emotional and behavioral states • Medulla - directly responsible for autonomic output • Some autonomic reflexes, such as urination, defecation, and erection, are integrated at spinal cord level |
