Download Outline12 CNS - Napa Valley College

Biology 219 – Human Physiology
Central Nervous System
Clemens
Text: Ch. 9
A. Organization of the Nervous System
1. Central Nervous System (CNS)
Brain
Spinal Cord.
2. Peripheral Nervous System (PNS)
Afferent Division
a. Somatic Sensory - from skin, muscles, bones & joints (general senses)
b. Visceral Sensory - from internal organs
c. Special Senses - vision, hearing, equilibrium, olfaction, taste
Efferent Division
a. Somatic Motor – voluntary, to skeletal muscles
b. Autonomic (ANS) – involuntary, to heart, smooth muscle, glands, adipose tissue
i. sympathetic division
ii. parasympathetic division
3. Enteric Nervous System - nerve network in the GI tract; semi-autonomous
B. Supporting Structures of the CNS
1. Meninges - connective tissue coverings of the CNS
dura mater
arachnoid
pia mater
2. Cerebrospinal Fluid (CSF)
- produced by the choroid plexuses of the brain ventricles
- CSF circulates through the ventricles and into the subarachnoid space around the brain
- CSF composition is regulated; low protein concentration compared to plasma
3. Glial Cells - supporting cells of the NS
astrocytes - provide physical and metabolic support to neurons
blood-brain barrier - tight junctions between capillary endothelial cells
regulates passage of substances from the blood into the brain interstitial fluid
microglia - phagocytes, immune and maintenance functions
oligodendrocytes – form myelin sheath around axons in the CNS
Schwann cells – form myelin sheath around axons in the PNS
ependymal cells - line the brain ventricles and produce CSF
C. Spinal Cord and Spinal Nerves
1. Spinal Cord
a. gray matter – neuron cell bodies, dendrites, axon terminals, synapses; integration areas
dorsal (posterior) horn - sensory input
ventral (anterior) horn - motor output
In the brain, gray matter makes up the cerebral cortex, cerebellar cortex, and nuclei
b. white matter - tracts of myelinated axons → conduct APs over longer distances
ascending tracts: sensory information
descending tracts: motor information
2. Spinal Nerves
- 31 pairs (cervical C1-C8, thoracic T1-T12, lumbar L1-L5, sacral S1-S5, coccygeal Co1)
a. dorsal root - incoming axons of sensory neurons (cell bodies in dorsal root ganglia)
b. ventral root - outgoing axons of motor neurons (cell bodies in ventral gray horn)
3. Spinal Reflexes
Reflex Arc - basic neural response pathway
STIMULUS → 1. sensory receptor → 2. sensory neuron → 3. integrating center
RESPONSE ← 5. effector (muscle) ← 4. motor neuron ←
(spinal cord )
monosynaptic reflex (e.g., muscle spindle stretch reflex)
polysynaptic reflexes (e.g., withdrawal reflex and crossed extensor reflex)
D. The Brain
The brain stem consists of the medulla oblongata, pons and midbrain
- connects the spinal cord to higher brain regions
- controls many involuntary functions
1. Medulla Oblongata
- ascending tracts carry sensory information to higher brain areas
- descending tracts carry motor signals, cross over to opposite side in the medulla
- respiratory and cardiovascular control centers
- other involuntary control centers (swallowing, vomiting)
2. Pons
- contains connections between the cerebellum and other CNS areas
- respiratory centers coordinate with the medulla to control breathing
3. Midbrain
- controls visual and auditory reflexes
- role in unconscious motor control, connections to the cerebrum
reticular formation - collection of nuclei and neural pathways that originate in the brain stem;
involved in arousal of the cerebral cortex (sleep/wake)
4. Cerebellum
- major role in coordination of movement;
- receives inputs from muscles, joints, inner ear; feedback to cerebral motor area
- cortex is gray matter, internal white matter (arbor vitae)
5. Diencephalon
a. thalamus - sensory “relay station”, receives incoming neurons from the lower CNS and
special senses and connects each pathway to a specific location in the cerebral cortex
b. hypothalamus - major control center for homeostasis
- regulates body temperature, osmolarity, thirst, appetite,
- regulates endocrine function via control of the pituitary gland
- mediates physiological responses of emotional states (via autonomic NS)
c. pineal gland - endocrine gland in the brain, secretes melatonin
6. Cerebrum
a. Cerebral gray matter and white matter
gray matter
cerebral cortex
basal ganglia and nuclei of the limbic system
white matter
association fibers – connect areas within the same cerebral hemisphere
commissural fibers (corpus callosum) – connect R and L cerebral hemispheres
projection fibers – connect cerebral cortex to lower brain areas and spinal cord
b. Cerebral cortex
- highest-level processing and integration areas
- gyri and sulci increase surface area of cortex
Lobes: frontal, parietal, temporal, occipital
Functional brain areas:
frontal lobe - primary motor area, speech (Broca’s) area;
prefrontal cortex - higher-level thinking, planning, judgment, personality
parietal lobe - primary somatosensory area; sensory association areas
occipital lobe - visual cortex and visual association areas
temporal lobe - auditory cortex; language association (Wernicke’s) area
Cerebral lateralization: left hemisphere-right hemisphere functional differentiation
e.g., language and logic: L hemisphere; visual/spatial perception: R hemisphere
d. Basal ganglia
- deep gray matter areas, involved in subconscious motor control and other functions
e. Limbic system - “emotional brain”
amygdala - center of strong emotions (fear, anger); role in memory processing
hippocampus - major role in consolidation of long-term memory