Ch. 10 - Neurophysiology 2 Flashcards
What are the divisions of the parasympathetic postganglionic receptors?
- Nicotinic
- Muscarinic
What are all preganglionic autonomic neurons and all postganglionic parasympathetic neurons classified as?
Cholinergic
What are the cholinergic effects of:
- preganglionic autonomic system?
- postganglionic parasympathetic fibers?
- Excitatory
- Either excitatory or inhibitory (depending on the end-organ)
Describe the preganglionic nerve fiber and the postganglionic nerve fiber of the sympathetic nervous system.
- Preganglionic - Myelinated, cholinergic
- Postganglionic - Unmyelinated, adrenergic
What are the principal locations of Alpha-1 and Alpha-2 adrenergic receptors?
- Alpha-1 - Vascular smooth muscle (skin, mucosa, GI) (Vasoconstriction)
- Alpha-2 - Presynaptic nerve terminals, platelets, fat cells, GI tract wall
What are the principal locations of the Beta-1 and Beta-2 adrenergic receptors?
- Beta-1 - Heart (increase heart rate, contractility)
- Beta-2 - Skeletal muscle, bronchial smooth muscle (Vasodilation, bronchodilation)
What are the sensory (ascending) pathways, along with their stimuli?
- Spinothalamic
- Pain, temperature
- Dorsal column, medial lemniscus
- Touch, pressure, vibration, proprioception
What are the motor (descending) pathways?
- Corticospinal (pyramidal)
- Extrapyramidal
What makes up the spinal cord?
- SAME DAVE
- Dorsal horn - Sensory (afferent)
- Ventral (anterior) root - Motor (efferent)
What are the 2 broad types of receptors and what is included in each of those types?
- Exteroreceptors (external stimuli)
- Touch, pressure, pain, temperature, light, sound
- Internoreceptors (visceroreceptors)
- Pressure, pain, chemical changes
- Proprioceptors (position in space)
What are the different types of joint receptors?
- Nonencapsulated
- Free nerve endings
- Encapsulated
- Pacinian - vibration, pressure
- Ruffini - stretch
- Neuromuscular spindles - stretch
- Neurotendons - tension
Which part of the spinothalamic tract transmits pain and temperature vs the tract that transmits light touch?
- Pain & temperature - Lateral spinothalamic
- Light touch - Anterior spinothalamic
What does the dorsal column and medial lemniscus system convey?
- Touch, pressure, vibration
In the dorsal column, medial lemniscus system, what fibers use the Fasciculus gracilis and what fibers use the Faciculus cuneatis?
- Fasciculus gracilis - lower extremities
- Fasciculus cuneatis - upper extremities
How is the somatosensory cortex representation described?
Homunculus (body proportional to sense)
What are the 2 major systems of the descending motor tracts?
- Corticospinal tract (pyramidal)
- Extrapyramidal
Where do the fibers of the corticospinal tract decussate?
In the medulla (pyramids)
What does it mean that the corticospinal tract decussates in the medulla?
The right brain controls left somatic muscles, visa-versa
What smaller tracts make up the extrapyramidal system?
- Rubrospinal - posture, somatic muscle
- Reticulospinal - locomotion
- Olivospinal - motor learning
- Vestibulospinal - head and neck muscles
- Tectospinal - coordinates head, neck, eye
Where does the extrapyramidal system tracts decussate?
In the pons - which means the right brain controls the left lower motor neuron
If you hemitransect the right side of the spinal cord, you lose ______ motor control (________), and _________ pain and temperature sense (_________).
- Ipsilateral
- Corticospinal
- Contra-lateral
- Spinothalamic
A lesion on one side of the spinal cord causes?
- Ipsilateral motor loss (corticospinal)
- Ipsilateral touch/sensory loss
- Contralateral pain and temp loss (spinothalamic)
What is the resting membrane potential in most cells, and heart cells?
- Most cells - around -70mV
- Cardiac cells - -90mV
What is the threshold for an action potential?
20 mV+
What is the “all or none” phenomenon?
If don’t reach threshold, dont get action potential
What is responsible for the relative refractory period?
Hyperpolarization - an overshoot in the more negative direction during repolarization
What are the excitable cells?
- Neurons
- Muscle cells
- Cardiac pacemaker
How do local anesthetics work?
- Block sodium channels (decrease Na+ permeability)
- Lowers membrane excitability –> can’t generate AP –> no nerve impulse conduction
In what order does local anesthetics affect nerve fibers?
- Unmyelinated C-fibers (slow, dull, long lasting)
- Small myelinated nerve fibers (pain, temp)
- Large A-fibers (touch proproiception, golgi tendon)
What is the major excitatory neurotransmitter?
Glutamate
What are some examples of inhibitory neurotransmitters?
- Glycine
- GABA
- Both bind receptors and open Cl- channels
What is Spatial Summation?
When 2 excitatory inputs arrive at a postsynaptic neuron simultaneously - converging circuit
What is Temporal Summation?
When 2 excitatory inputs arrive at a postsynaptic neuron in rapid succession
What does myelin do?
Prevents movement of Na+ and K+ through membrane
- Lowers membrane capacitance
- Raises membrane resistance
What does conduction velocity depend on?
- Diameter of nerve fiber
- Presence of myelin sheath
Define these problems with nerve conduction:
- Wallerian Degeneration
- Neuropraxia
- Axonotmesis
- Neurotmesis
- Wallerian Degeneration - axon is cut
- Neuropraxia - transient block (bruise)
- Axonotmesis - axon damaged, connective sheath remains intact
- Neurotmesis - complete transaction of nerve trunk –> motor flaccid paralysis, atrophy of end-organ
Which nerve fibers can regenerate, and where are they located?
Fibers of the PNS - with neurilemma (sheaths)
How are nerve cells myelinated in the CNS vs the PNS?
- CNS - oligodendrocytes with no neurilemma
- PNS - Schwann cells with neurilemma
