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)
¾ CNS consists of: 1. Brain 2. Spinal cord
¾ 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 Spinal Figure 5.1 Brain system cord Page 136 (CNS) (Input to CNS (Output from CNS from periphery) to periphery)
Peripheral Afferent nervous Efferent division system division (PNS)
Sensory Visceral Somatic Autonomic stimuli stimuli nervous system nervous system
Motor Sympathetic Parasympathetic neurons nervous system nervous system
Skeletal Smooth muscle Cardiac muscle muscle Glands Effector organs (made up of muscle and gland tissue)
3 Classes of Neurons
1. Afferent neurons
2. Efferent neurons
3. Interneurons
Central Peripheral nervous system nervous system (spinal cord)
Cell Axon body terminals Afferent neuron
Central Peripheral axon axon (afferent fiber) Receptor
Interneuron
Axon terminals Efferent neuron* Effector organ (muscle or gland) Cell Axon body (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
3 Protection for the Brain 1. Bony structures –cranium
2. Cranial Meninges a. dura mater (outermost) b. arachnoid c. pia mater (innermost)
3. Cerebrospinal fluid & Ventricles • Cushioning, support, & nutrient transportation
4. Blood-brain barrier
Cerebrospinal fluid Figure 5.6 (1) Page 141
Pia mater Arachnoid mater Cranial meninges Dura mater
Pia mater Arachnoid mater Spinal meninges Dura mater
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 Transport mechanisms 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
1. Cerebral Cortex (Cerebrum) • 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
Somato- sensory cortex
Major Functions 2. Basal nuclei (Cerebrum) • Inhibition of muscle tone • Suppress unwanted patterns of movement • Monitor and sustain slow contractions (i.e. posture)
Basal nuclei (gray matter)
Major Functions 3. Thalamus • Part of diencephalon • Relay station for synaptic (sensory) input 9 Screens out insignificant signals • Role in motor control
Thalamus
8 Major Functions
4. Hypothalamus • 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 5. Limbic System • Region surrounding brain stem in forebrain • Emotion & behavior patterns
Major Functions 6. Cerebellum (between brain stem & cerebrum) • 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 7. Brainstem (medulla, pons, midbrain) • 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 Cervical cord nerves Vertebrae
Thoracic Thoracic nerves cord
Lumbar Lumbar nerves cord
Sacral Sacral nerves cord Coccygeal nerve
10 Spinal cord Figure 5.27 Page 172 Dorsal root ganglion
Spinal nerve Meninges (protective Vertebra coverings)
Intervertebral disk
1. Gray Matter • Shaped like the letter H 9 Neurons & glial cells
2. White Matter • Myelinated nerves (ascending & descending tracts)
3. Ventral roots • Motor nerves
4. Dorsal roots • Sensory nerves • Dorsal root ganglion (groups of cell bodies)
Cell body of White matter Gray matter efferent neuron Interneuron
Cell body of afferent neuron Dorsal root
Afferent fiber Dorsal root ganglion
From receptors
To effectors
Ventral root
Spinal nerve Figure 5.29 Page 174
11 Reflexes & the Spinal Cord
= Inhibitory interneuron Components of a Figure 5.33 = Excitatory interneuron reflex arc Page 178 = Synapse = Inhibits Receptor = Stimulates Afferent pathway Integrating center Efferent pathway Effector organs Thermal pain receptor in finger Ascending pathway to brain Afferent Pathway
Stimulus
Biceps Efferent pathway (flexor) Integrating center contracts Triceps (spinal cord) (extensor) Hand relaxes withdrawn Effector organs Response
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