Amyotrophic Lateral Sclerosis
- upper and lower neuron destruction
Primary Lateral Sclerosis
- only upper motor neuron destruction
Parkinson's Disease
- destruction of the dopamine cells in the brain and/or atypical protein accumulation
- treatment = exogenous NTs (i.e. synthetic dopamine)
Alzheimer's Disease/Dementia
- atypical proteins (amyloids) assemble and/or destruction of neurons
CNS vs. PNS
- C: brain and spinal cord -> Afferent
- P: cranial nerves and spinal nerves -> Efferent
Afferent vs. Efferent Divison
- A: sensory, CNS
- E: motor, PNS
Efferent Division
- ANS and SNS (somatic nervous system)
- A: involuntary, impulses from CNS to muscle; sympathetic ("exciting") and parasympathetic ("housekeeping"/regulatory)
- S: voluntary, conducts impulses from CNS to skeletal muscles
CNS - The Brain
- Cerebral cortex contains billions of neurons each connected by synapses to 1000's of other neurons
- Central control center
- Sensory neurons outnumber motor neurons 20 to 1
6 Main Areas of the Brain
- Diencephalon (
thalamus and hypothalamus
)
- Telencephalon (
cerebral cortex
)
- Mesencephalon (midbrain) brain-stem
- Pons- brainstep
-
Medulla Oblongata
- brainstem
-
Cerebellum
Lobes of the Brain
- Frontal Lobe: movement, coordination, Information
- Parietal Lobe: sensory info
- Occipital Lobe: seeing
- Temporal Lobe: hearing
Pre-Centeral Gyrus is _____ while Post Central Gyrus is _____
- Pre: motor
- Post: sensory
Medulla
- Center for cardiovascular and respiratory control
- Level of spinal cord where signals cross
Pons
Relays signals from the cerebrum to the cerebellum
-
a bridge
Cerebullum
- "little brain"
- coordinates and dampens or ramps up AP
-
Integration and Fine Tuning for Muscle Control
-> pre packaged motor patterns
- Monitors and coordinates areas of the brain involved in motor control
- Contributes to coordination, precision, and
Thalamus
- Relays sensation, special sense, and motor signals to the cerebral cortex
- Regulates consciousness, sleep, and alertness
Hypothalamus
- Links the nervous system to the endocrine system via the pituitary gland by secreting neurohormones
-
Regulatory Center
- Metabolic rate; chemoreceptors
- Body temperature
Diencephalon
- Thalamus and Hypothalamus
Telencephalon
- Contains two hemispheres of cerebral cortex
- 40% of total brain mass
Cerebral Cortex
- The intricate fabric of interconnected neural cells covering the cerebral hemispheres; the body's ultimate control and information-processing center.
Corpus Callosum
- Connects right and left hemispheres
- Connects motor and sensory cortex together
Common Neurotransmitters in the Brain
- Dopamine
- ACh
- Serotonin
- Norepinephrine
- Gamma Aminobutyric Acid (GABBA)
- Glutamate
Myelin
- A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next ->
Saltatory Conduction
The Spinal Cord Overview
- 45 cm long, 1 cm diameter
- Encased by
33
vertebrae
- Feeds 31 spinal nerves
- Provides for 2-way flow of communication b/t brain and periphery via nerve tracts and sensory receptors
Efferent vs. Afferent Neurons
- Efferent: motor neurons that transmit impulses AWAY from CNS (brain -> muscle)
- Afferent: sensory neurons that transfer impulses TOWARDS the CNS (muscle -> brain)
Lateral Corticospinal Tract
- Pyramidal (voluntary)
- Motor neurons of the
peripheral muscles
- Think of interstate 65 -- when damaged/backed up, can learn to use other pathways
- Carries a majority of the motor impulses from pre-central gyrus of the motor cortex to the peripheral n
Vertical Corticospinal Tract
- Motor neurons of the trunk/postural muscles
- Uncrossed; controls postural muscles -> core muscles, muscles that keep us erect
Where do APs exit?
- Depends on what they're targeting (i.e. fingers = upper thoracic)
Grey vs. White Matter
- Grey = neuron cell bodies, capillaries, dendrites
- White matter = myelinated axons
Anterior Route
-
Anterior side
of the spinal cord receives the information
Possible Problem with Nerves
- Could get pinched (i.e. slipped disk)
- Usually in the lumbar area where there is more pressure/ most of your weight is carried
- Dorsal Route carries info back to brain
- Can be prevented with a strong core, flexible hamstrings, and smaller "beer-belly
Reflex Arc
- A relatively direct connection between a sensory neuron and a motor neuron that allows an extremely rapid response to a stimulus, often without conscious brain involvement
- *See figures demonstrating this
Spinal Cord Protective Layers (Deep to Superficial)
Pia mater -> Arachnoid mater -> Dura mater
Vagus Nerve
- Controls stomach, cardiac, and pulmonary
Peripheral Nervous System
A division of the nervous system consisting of all nerves that are not part of the brain or spinal cord
- Connects CNS to rest of body
- 31 pairs of spinal nerves, 12 pairs of cranial nerves
2 Types of Efferent Neurons
- Somatic neurons: innervate skeletal muscle
- Autonomic neurons: activate smooth muscle, cardiac muscle, sweat and salivary glands, and some endocrine glands
Motor Unit
- group of muscle fibers and the nerve that innervates them
Neuromuscular Junction
- Point of contact between a motor neuron and a skeletal muscle cell
- Interface between the end of a motor neuron and a muscle fiber
- Anatomic features of a neuromuscular
junction:
-- Presynaptic terminals
-- Synaptic cleft
-- Postsynaptic membrane
What is an Action Potential?
- All action potentials begin as graded potentials
Requires depolarization greater than the threshold value of
15 mV to 20 mV
to be initiated
- The membrane voltage at which a graded potential becomes an action potential is called the
depolarization thres
Resting Membrane Potential
- Difference between the electrical charges inside and outside a cell, caused by separation of charges across the cell membrane
- High concentration of K+ inside of the neuron and Na+ on the outside of the neuron
- Cell is more permeable to K, thus K ions
Changes in Membrane Potential
-
Depolarization
occurs when inside of cell becomes less negative relative to outside and is caused by a change in the membrane's Na+ permeability (>-70 mV); threshold for contraction is -55mV
- Graded potentials are localized changes in membrane potentia
Extrafusal vs Intrafusal Muscle Fibers
- E: outside spindle, alpha-motor neurons
- I: inside spindle, gama-motor neurons
Muscle Spindles
- Lies between regular skeletal muscle fibers
- The middle of the spindle cannot contract but can stretch
- When muscles attached to the spindle are stretched, neurons on the spindle transmit information to the CNS about the muscle's length, and the rate
Golgi Tendon Organs (GTOs)
- Encapsulated sensory organs through which a small bundle of muscle tendon fibers pass
- Located proximal to the tendon's attachment to the muscle
-
Sensitive to changes in tension
- *Inhibit contracting/agonist muscles and excite
antagonist muscles to p
Absolute Refractory Period
- When a given segment of an axon is generating an action potential, its sodium gates are open and it is
unable to respond to another stimulus
Relative Refractory Period
- When the sodium gates are closed, the potassium gates are open, and repolarization is occurring, the segment of the axon *can
respond to a new stimulus
, but the stimulus must be
substantially greater to evoke an action potential*
REVIEW PATH OF ACTION POTENTIAL; ALL THE WAY FROM NEURON TO MUSCLE
REVIEW PATH OF ACTION POTENTIAL; ALL THE WAY FROM NEURON TO MUSCLE