Download Central Nervous System

Central Nervous
System
Overview
¾
Nervous and endocrine
systems major regulators of the
body
• Rapid response to external &
internal stimuli
Nervous System = 2 systems
• Central Nervous System (CNS)
• Peripheral Nervous System
(PNS)
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CNS consists of:
1. Brain
2. Spinal cord
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PNS consists of:
1. Afferent (sensory) division
2. Efferent (motor) division
9 Efferent system divided into Somatic Nervous System
(SNS)
9 Autonomic nervous system (ANS)
1
Central
nervous
system
(CNS)
Brain
(Input to CNS
from periphery)
Sensory
stimuli
(Output from CNS
to periphery)
Peripheral
nervous
system
(PNS)
Afferent
division
Figure 5.1
Page 136
Spinal
cord
Visceral
stimuli
Efferent
division
Somatic
nervous system
Motor
neurons
Autonomic
nervous system
Sympathetic
nervous system
Parasympathetic
nervous system
Smooth muscle
Cardiac muscle
Glands
Effector organs
(made up of muscle
and gland tissue)
Skeletal
muscle
3 Classes of Neurons
1.
Afferent neurons
2.
Efferent neurons
3.
Interneurons
Central
nervous system
(spinal cord)
Axon
terminals
Peripheral
nervous system
Cell
body
Central
axon
Afferent neuron
Peripheral axon
(afferent fiber)
Receptor
Interneuron
Axon
terminals
Efferent neuron*
Effector organ
(muscle or gland)
Cell
body
Axon
(efferent fiber)
2
Central Nervous System
Cells of the CNS
¾
Nervous tissue in CNS comprised of glial cells or
neuroglia:
1. Astrocytes: scaffolding, blood-brain barrier, injury &
scar tissue, remove excess K+, enhance chemical
signaling
2. Oligodendrocytes: form myelin sheaths in CNS
3. Microglia: immune defense cells of CNS
4. Ependymal cells: support cerbrospinal fluid,
possibly aid in formation of new neurons & glial cells
Space containing cerebrospinal fluid
Ependymal cell
Astrocyte
Microglial cell
Oligodendrocyte
Figure 5.3 Page 138
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Protection for the Brain
Bony structures – cranium
1.
Cranial Meninges
2.
a. dura mater (outermost)
b. arachnoid
c. pia mater (innermost)
Cerebrospinal fluid & Ventricles
3.
•
4.
Cushioning, support, & nutrient transportation
Blood-brain barrier
Cerebrospinal fluid
Figure 5.6 (1)
Page 141
Pia mater
Arachnoid mater
Dura mater
Pia mater
Arachnoid mater
Dura mater
Cranial meninges
Spinal meninges
Figure 5.6 (2)
Page 141
Scalp
Skull bone
Dura mater
Arachnoid mater
Pia mater
Brain (cerebrum)
4
CSF and Ventricles
¾
Fluid filled cavities within the brain
• Cerebrospinal fluid
9Shock absorption
9Higher in Na+ than K+
Right lateral
ventricle
Left lateral
ventricle
Third ventricle
Central canal
of spinal cord
Figure 5.5
Page 139
Fourth ventricle
5
Blood-brain Barrier
¾
Highly selective
• Tight junctions
9H20 soluble compounds need active transport
Pore passage
Carrier-mediated transport
Lipid-soluble
substances
Transport
mechanisms
Transport
mechanisms
Lipid-soluble
substances
Tight junction (no pores)
Water-lined pore
Anatomical Organization
of the Brain
Table 5.3 (1)
Page 144 Cerebral cortex
Basal nuclei
Thalamus
Hypothalamus
Cerebellum
Midbrain
Brain stem
Pons
Medulla
6
Major Functions
Cerebral Cortex (Cerebrum)
1.
•
•
•
•
Sensory perception
Personality & language
Conscious thought & memory
Complex motor patterns
(voluntary movement)
Cerebral Cortex Lobes
1.
Frontal lobe – voluntary motor activity
(primary motor cortex), speaking, thought
2.
Parietal lobes – proprioception & body
feelings (somatosensory cortex)
3.
Temporal lobe – auditory/olfactory areas
4.
Occipital lobe – visual areas
Frontal
lobe
Parietal
lobe
Occipital
lobe
Temporal
lobe
7
Primary
motor
cortex
Somatosensory
cortex
Major Functions
Basal nuclei (Cerebrum)
2.
•
•
•
Inhibition of muscle tone
Suppress unwanted patterns of movement
Monitor and sustain slow contractions (i.e. posture)
Basal nuclei
(gray matter)
Major Functions
Thalamus
3.
•
•
Part of diencephalon
Relay station for synaptic (sensory) input
9 Screens out insignificant signals
•
Role in motor control
Thalamus
8
Major Functions
Hypothalamus
4.
•
•
•
Homeostatic function
Temperature, thirst regulation (urine output),
food intake
Link between nervous & endocrine systems
9 ANS coordinating center
•
Emotional & behavioral patterns
Mamillary bodies
(part of hypothalamus)
Major Functions
Limbic System
5.
•
•
Region surrounding brain
stem in forebrain
Emotion & behavior
patterns
Major Functions
Cerebellum (between brain stem & cerebrum)
6.
•
Vestibulocerebellum
9 Balance & eye movement
•
Spinocerebellum
9 Coordinated skill & voluntary movements
•
Cerbrocerebellum
9 Planning & initiation of voluntary movement
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
Cerebellum
9
Major Functions
Brainstem (medulla, pons, midbrain)
7.
•
•
•
•
Houses majority of cranial nerves
CV, Respiratory, & digestive control centers
Regulation of muscles involved in reflexes
(equilibrium & posture)
Reception of synaptic input from spinal cord
Brainstem
Spinal Cord
Figure 5.28
Page 173
Cervical
cord
Cervical
nerves
Thoracic
cord
Thoracic
nerves
Lumbar
cord
Sacral
cord
Vertebrae
Lumbar
nerves
Sacral
nerves
Coccygeal
nerve
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Spinal cord
Figure 5.27
Page 172
Dorsal root
ganglion
Spinal
nerve
Meninges
(protective
coverings)
Vertebra
Intervertebral
disk
Gray Matter
1.
•
Shaped like the letter H
9 Neurons & glial cells
White Matter
2.
•
Myelinated nerves (ascending & descending
tracts)
Ventral roots
3.
•
Motor nerves
Dorsal roots
4.
•
•
Sensory nerves
Dorsal root ganglion (groups of cell bodies)
Cell body of
efferent neuron
Cell body of
afferent neuron
Afferent fiber
White matter
Gray matter
Interneuron
Dorsal root
Dorsal root
ganglion
From receptors
To effectors
Ventral root
Spinal nerve
Figure 5.29 Page 174
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Reflexes & the Spinal Cord
= Inhibitory interneuron
= Excitatory interneuron
= Synapse
= Inhibits
= Stimulates
Figure 5.33
Page 178
Thermal
pain receptor
in finger
Components of a
reflex arc
Receptor
Afferent pathway
Integrating center
Efferent pathway
Effector organs
Ascending pathway
to brain
Afferent
Pathway
Stimulus
Biceps
(flexor)
contracts
Hand
withdrawn
Efferent pathway
Triceps
(extensor)
relaxes
Integrating center
(spinal cord)
Effector
organs
Response
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