The Nervous System
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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

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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


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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?


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The Nervous System

B. Cells of the nervous system

  • Neurons

  • Basic structure

  • Cell body

  • Dendrites

  • Axon

  • Fiber vs. nerve

  • What is myelin?


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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?


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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)


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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


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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


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The Nervous System

E. Organization of the nervous system

  • Sensory

  • peripheral nervous system

  • Motor

  • peripheral nervous system

  • Central nervous system

  • Brain

  • Spinal cord

  • Somatic motor neurons (voluntary) to skeletal muscles

  • Somatic receptors

  • 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


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The Nervous System

F. Central nervous system

  • Brain and spinal cord

  • Meninges

  • Dura mater

  • Arachnoid membrane

  • Pia mater


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The Nervous System

F. Central nervous system

  • 3. Cerebrospinal fluid

  • Subarachnoid space

  • Ventricles and central canal

  • Flow pattern


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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)


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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


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The Nervous System

F. Central nervous system

  • 8. Spinal cord (white and gray matter)

  • Regions

  • Cervical

  • Thoracic

  • Lumbar

  • Sacral

  • Coccygeal


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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


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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


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The Nervous System

G. Peripheral nervous system

  • Cranial nerves (12 pairs)

  • Spinal nerves (31 pairs)


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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


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The Nervous System

G. Peripheral nervous system

  • 4. Autonomic nervous system

sympathetic

parasympathetic

  • Dual innervation

  • Antagonistic

  • Sympathetics

  • Thoracolumbar

  • Fight-or-flight

  • d. Parasympathetic

  • Craniosacral

  • Feed- and-breed


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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


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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


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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


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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


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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


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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


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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


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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


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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)


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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?

end


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