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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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slide1

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
slide2

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?
slide3

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?
slide5

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)
slide6

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
slide8

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
slide9

The Nervous System

F. Central nervous system

  • Brain and spinal cord
  • Meninges
  • Dura mater
  • Arachnoid membrane
  • Pia mater
slide10

The Nervous System

F. Central nervous system

  • 3. Cerebrospinal fluid
  • Subarachnoid space
  • Ventricles and central canal
  • Flow pattern
slide11

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
slide13

The Nervous System

F. Central nervous system

  • 8. Spinal cord (white and gray matter)
  • Regions
  • Cervical
  • Thoracic
  • Lumbar
  • Sacral
  • Coccygeal
slide14

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
slide16

The Nervous System

G. Peripheral nervous system

  • Cranial nerves (12 pairs)
  • Spinal nerves (31 pairs)
slide17

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
slide20

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
slide23

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
slide24

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
slide25

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
slide26

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
slide27

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)
slide28

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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