Download Chapter 7 The Nervous System

The Nervous System
A. Introduction
1. Nervous control vs. endocrine control of the body
2. What does the nervous system do?
a. Receive, process, store sensory information
b. Integrate and interpret
c.
Stimulation of skeletal muscle
d. Stimulation/inhibition of smooth and cardiac muscle
e. Stimulation/inhibition of glands
f.
cognition
The Nervous System
A. Introduction
3. Why is the nervous system of prime importance to
understanding aging effects on the body?
a. It controls virtually all body functions
b. Neurons are postmitotic – why is this important?
The Nervous System
B. Cells of the nervous system
1. Neurons
a. Basic structure
i.
Cell body
ii.
Dendrites
iii.
Axon
b. Fiber vs. nerve
c.
What is myelin?
The Nervous System
B. Cells of the nervous system
1. Neurons
d. Types of neurons
i.
Motor
ii.
Sensory
iii.
Association (interneuron)
e. What is a center?
f.
What is a ganglion?
The Nervous System
B. Cells of the nervous system
2. Neuroglia (glial cells)
a. Support cells of the nervous system
b. Greatly outnumber neurons
c.
Types of cells
i.
Astrocytes (CNS)
ii.
Oligodendrocytes (CNS)
iii.
Microglial cells (CNS)
iv.
Ependymal cells (CNS)
v.
Neurolemmocytes (Schwann cells) (PNS)
The Nervous System
C. Membrane potentials
1. What is a polarized membrane?
2. How is it formed?
3. What are voltage-gated channels?
4. Resting potential vs. action potential
5. Continuous conduction
6. Saltatory conduction
The Nervous System
D. The synapse
1. Presynaptic neuron
2. Synaptic cleft
3. Postsynaptic neuron
4. Excitatory neurotransmitters
a. Acetylcholine
c.
Dopamine
b. Norepinephrine
d. Serotonin
5. Inhibitory neurotransmitters
a. Gamma aminobutyric acid (GABA)
b. Glutamate
The Nervous System
E. Organization of the nervous system
Sensory
peripheral nervous system
Somatic receptors
Visceral receptors
Special sensory receptors
Sensory receptors and
neurons in the gut
Motor
peripheral nervous system
Central nervous system
Brain
Somatic motor neurons
(voluntary) to skeletal
muscles
Spinal cord
Sympathetic and
parasympathetic nervous
systems
Autonomic motor neurons
(involuntary) to smooth
muscle, cardiac muscle,
and glands
Enteric motor neurons
(involuntary) in gut to
smooth muscle and glands
The Nervous System
F. Central nervous system
1. Brain and spinal cord
2. Meninges
a. Dura mater
b. Arachnoid membrane
c.
Pia mater
The Nervous System
F. Central nervous system
3. Cerebrospinal fluid
a. Subarachnoid space
b. Ventricles and central canal
c.
Flow pattern
The Nervous System
F. Central nervous system
4. Cerebrum (white and gray matter)
a. Hemispheres and lobes
b. Gyrus – sulcus – fissure
c.
Cerebral cortex
d. Functional areas
f.
i.
Primary sensory areas
ii.
Primary motor areas
iii.
Association areas
Basal ganglia (cerebral nuclei)
The Nervous System
F. Central nervous system
5. Cerebellum (white and gray matter)
6. Diencephalon (gray matter)
a. Thalamus
b. Hypothalamus
c.
Epithalamus
7. Brainstem (white and gray matter)
a. Midbrain
b. Pons
c.
Medulla oblongata
The Nervous System
F. Central nervous system
8. Spinal cord (white and gray matter)
a. Regions
i.
Cervical
ii.
Thoracic
iii.
Lumbar
iv. Sacral
v.
Coccygeal
The Nervous System
F. Central nervous system
8. Spinal cord
b. Cross-sectional anatomy
i.
Horns
a)
b)
ii.
Roots
a)
b)
iii.
Dorsal = sensory nuclei
Ventral = motor nuclei
Dorsal = sensory axons
Ventral = motor axons
Tracts
a)
b)
Ascending
Descending
The Nervous System
F. Central nervous system
8. Spinal cord
c.
What is a reflex?
i.
Inborn
ii.
Unconscious
iii.
Unlearned
d. Reflex arc components
receptor  sensory neuron 
integration center 
motor neuron  effector
The Nervous System
G. Peripheral nervous system
1. Cranial nerves (12 pairs)
2. Spinal nerves (31 pairs)
The Nervous System
G. Peripheral nervous system
3. subdivisions
a. Afferent
i.
Somatic sensory from skin, joints, skeletal muscles
ii.
Visceral sensory from organs
b. Efferent
i.
Somatic (voluntary) motor to skeletal muscles
ii.
Autonomic (involuntary) motor to cardiac muscle, smooth
muscle, glands
a)
b)
Sympathetic nervous system
Parasympathetic nervous system
The Nervous System
G. Peripheral nervous system
4. Autonomic nervous system
a. Dual innervation
b. Antagonistic
c.
Sympathetics
i.
Thoracolumbar
ii.
Fight-or-flight
d. Parasympathetic
i.
Craniosacral
ii.
Feed- and-breed
sympathetic
parasympathetic
The Nervous System
H. Age-related changes
1. Nerve cells die with aging (~10,000 per day)
a. Neurons do not undergo mitosis
b. Therefore, lost neurons are not replaced
c.
Nervous tissue is gradually reduced
2. Other neuronal changes
a. Axons swell
b. Myelin diminishes
c.
Cytoskeleton decreases in abundance
The Nervous System
H. Age-related changes
3. Why does routine loss of neurons not
affect function until very late in life?
4. Loss of neurons + loss of myelin =
decreased brain mass
a. Decrease isn’t uniform throughout brain
b. 25% loss of cerebellum; other areas lose nothing
c.
Decline is size begins slowly at age 30, much faster
at age 60; 10% gone by age 90
d. Ventricles enlarge, gyri become smaller, sulci widen
The Nervous System
H. Age-related changes
5. Loss of brain mass = loss of learning new skills
a. What functions tend to have greater decline?
i.
Response times in reflexes
ii.
Integration of things observed
iii.
Alertness (brain reactivity time)
b. What functions do not decline as quickly?
i.
Verbal ability
ii.
Memory
The Nervous System
H. Age-related changes
6. Some neurons sprout new axons and establish new
synapses
a. New synapses = net increase in connections
b. Learning requires development of new synapses
7. However, there is age-related decline in IQ test scores
a. Thought to be associated with neuronal loss
b. Elderly may have as much as 25% loss in verbal ability
c.
Wide range of individual variability
The Nervous System
H. Age-related changes
8. Memory is affected by age
a. Long-term memory least affected
b. Higher intellects retain better memory
c.
Active brains retain memory longer
9. Decreased rate of nerve impulse conduction
10. Increased synaptic delay
a. Decreased neurotransmitter released
b. Decreased postsynaptic receptors
The Nervous System
H. Age-related changes
11. Reduced dendrites and dendritic spines
12. Intracellular neuronal changes
a. Decreased Nissl substance (ribosomes)
b. In the hippocampus, particularly:
i.
Neurofibrillary tangles
ii.
Neuritic plaques
13. Glial cell changes
The Nervous System
H. Age-related changes
14. Changes in sympathetic nervous system activity
a. Increased norepinephrine secretion +
b. Decreased removal of norepinephrine at the synapse +
c.
Decreased norepinephrine receptor sensitivity
15. Changes in parasympathetic nervous system activity
The Nervous System
I. Age-related dysfunctions
1. Decreased somatic reflex responses
2. Declining autonomic reflex responses
a. Body temperature control
b. Blood pressure control
c.
Urethral and anal internal sphincter control
3. Insomnia
a. REM vs. non-REM sleep
b. Difficulty falling asleep + frequent awakenings
c.
Reticular activating system dysfunction
The Nervous System
I. Age-related dysfunctions
4. Dementia (organic brain syndrome)
a. What is it?
b. Reversible vs. irreversible
c.
Categories
i.
Alzheimer’s disease
ii.
Non-Alzheimer’s disease
iii.
Multi-infarctional dementia
iv. Parkinson’s disease
v.
Cerebrovascular accident (stroke)
The Nervous System
J. Take home messages
1. What are the divisions of the nervous system and how
are they communicated together?
2. What is the basic structure and function of the neuron?
3. Neurons die with aging and aren’t replaced
4. Conduction velocities decrease with aging
5. Synaptic delay increases with aging
6. Reflex times increase with aging
7. Many intracellular changes with aging
8. What are dementias?
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