2. The Nervous System Introduction
Nervous control vs. endocrine control of the body
What does the nervous system do?
Receive, process, store sensory information
Integrate and interpret
Stimulation of skeletal muscle
Stimulation/inhibition of smooth and cardiac muscle
Stimulation/inhibition of glands
cognition

3. The Nervous System Introduction
3. Why is the nervous system of prime importance to understanding aging effects on the body?
It controls virtually all body functions
Neurons are postmitotic – why is this important?

4. The Nervous System B. Cells of the nervous system Neurons
Basic structure
Cell body
Dendrites
Axon
Fiber vs. nerve
What is myelin?

5. The Nervous System B. Cells of the nervous system Neurons
d. Types of neurons
Motor
Sensory
Association (interneuron)
What is a center?
What is a ganglion?

6. The Nervous System B. Cells of the nervous system
2. Neuroglia (glial cells)
Support cells of the nervous system
Greatly outnumber neurons
Types of cells
Astrocytes (CNS)
Oligodendrocytes (CNS)
Microglial cells (CNS)
Ependymal cells (CNS)
Neurolemmocytes (Schwann cells) (PNS)

7. The Nervous System C. Membrane potentials
What is a polarized membrane?
How is it formed?
What are voltage-gated channels?
Resting potential vs. action potential
Continuous conduction
Saltatory conduction

8. The Nervous System D. The synapse Presynaptic neuron Synaptic cleft
Postsynaptic neuron
Excitatory neurotransmitters
Acetylcholine
Norepinephrine
c. Dopamine
d. Serotonin
5. Inhibitory neurotransmitters
Gamma aminobutyric acid (GABA)
Glutamate

9. The Nervous System E. Organization of the nervous system
Sensory
peripheral nervous system
Motor
peripheral nervous system
Central nervous system
Brain
Spinal cord
Somatic receptors
Somatic motor neurons (voluntary) to skeletal muscles
Visceral receptors
Special sensory receptors
Sympathetic and parasympathetic nervous systems
Autonomic motor neurons (involuntary) to smooth muscle, cardiac muscle, and glands
Sensory receptors and neurons in the gut
Enteric motor neurons (involuntary) in gut to smooth muscle and glands

10. The Nervous System F. Central nervous system Brain and spinal cord
Meninges
Dura mater
Arachnoid membrane
Pia mater

11. The Nervous System F. Central nervous system 3. Cerebrospinal fluid
Subarachnoid space
Ventricles and central canal
Flow pattern

12. The Nervous System F. Central nervous system
4. Cerebrum (white and gray matter)
Hemispheres and lobes
Gyrus – sulcus – fissure
Cerebral cortex
Functional areas
Primary sensory areas
Primary motor areas
Association areas
f. Basal ganglia (cerebral nuclei)

13. The Nervous System F. Central nervous system
Cerebellum (white and gray matter)
Diencephalon (gray matter)
Thalamus
Hypothalamus
Epithalamus
7. Brainstem (white and gray matter)
Midbrain
Pons
Medulla oblongata

14. The Nervous System F. Central nervous system
8. Spinal cord (white and gray matter)
Regions
Cervical
Thoracic
Lumbar
Sacral
Coccygeal

15. The Nervous System F. Central nervous system 8. Spinal cord
b. Cross-sectional anatomy
Horns
Dorsal = sensory nuclei
Ventral = motor nuclei
ii. Roots
Dorsal = sensory axons
Ventral = motor axons
iii. Tracts
Ascending
Descending

16. The Nervous System F. Central nervous system 8. Spinal cord
c. What is a reflex?
Inborn
Unconscious
Unlearned
d. Reflex arc components
receptor  sensory neuron 
integration center 
motor neuron  effector

17. The Nervous System G. Peripheral nervous system
Cranial nerves (12 pairs)
Spinal nerves (31 pairs)

18. The Nervous System G. Peripheral nervous system 3. subdivisions
Afferent
Somatic sensory from skin, joints, skeletal muscles
Visceral sensory from organs
b. Efferent
Somatic (voluntary) motor to skeletal muscles
Autonomic (involuntary) motor to cardiac muscle, smooth muscle, glands
Sympathetic nervous system
Parasympathetic nervous system

19. The Nervous System G. Peripheral nervous system
4. Autonomic nervous system
Dual innervation
Antagonistic
Sympathetics
sympathetic
parasympathetic
Thoracolumbar
Fight-or-flight
d. Parasympathetic
Craniosacral
Feed- and-breed

20. The Nervous System H. Age-related changes
Nerve cells die with aging (~10,000 per day)
Neurons do not undergo mitosis
Therefore, lost neurons are not replaced
Nervous tissue is gradually reduced
2. Other neuronal changes
Axons swell
Myelin diminishes
Cytoskeleton decreases in abundance

21. The Nervous System H. Age-related changes
Why does routine loss of neurons not affect function until very late in life?
Loss of neurons + loss of myelin = decreased brain mass
Decrease isn’t uniform throughout brain
25% loss of cerebellum; other areas lose nothing
Decline is size begins slowly at age 30, much faster at age 60; 10% gone by age 90
Ventricles enlarge, gyri become smaller, sulci widen

22. The Nervous System H. Age-related changes
5. Loss of brain mass = loss of learning new skills
What functions tend to have greater decline?
Response times in reflexes
Integration of things observed
Alertness (brain reactivity time)
b. What functions do not decline as quickly?
Verbal ability
Memory

23. The Nervous System H. Age-related changes
6. Some neurons sprout new axons and establish new synapses
New synapses = net increase in connections
Learning requires development of new synapses
7. However, there is age-related decline in IQ test scores
Thought to be associated with neuronal loss
Elderly may have as much as 25% loss in verbal ability
Wide range of individual variability

24. The Nervous System H. Age-related changes 8. Memory is affected by age
Long-term memory least affected
Higher intellects retain better memory
Active brains retain memory longer
Decreased rate of nerve impulse conduction
Increased synaptic delay
Decreased neurotransmitter released
Decreased postsynaptic receptors

25. The Nervous System H. Age-related changes
Reduced dendrites and dendritic spines
Intracellular neuronal changes
Decreased Nissl substance (ribosomes)
In the hippocampus, particularly:
Neurofibrillary tangles
Neuritic plaques
13. Glial cell changes

26. The Nervous System H. Age-related changes
14. Changes in sympathetic nervous system activity
Increased norepinephrine secretion +
Decreased removal of norepinephrine at the synapse +
Decreased norepinephrine receptor sensitivity
15. Changes in parasympathetic nervous system activity

27. The Nervous System I. Age-related dysfunctions
Decreased somatic reflex responses
Declining autonomic reflex responses
Body temperature control
Blood pressure control
Urethral and anal internal sphincter control
3. Insomnia
REM vs. non-REM sleep
Difficulty falling asleep + frequent awakenings
Reticular activating system dysfunction

28. The Nervous System I. Age-related dysfunctions
4. Dementia (organic brain syndrome)
What is it?
Reversible vs. irreversible
Categories
Alzheimer’s disease
Non-Alzheimer’s disease
Multi-infarctional dementia
Parkinson’s disease
Cerebrovascular accident (stroke)

29. The Nervous System J. Take home messages
What are the divisions of the nervous system and how are they communicated together?
What is the basic structure and function of the neuron?
Neurons die with aging and aren’t replaced
Conduction velocities decrease with aging
Synaptic delay increases with aging
Reflex times increase with aging
Many intracellular changes with aging
What are dementias?
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