Lecture: functional neuro anat Flashcards
1
Q
Nerve
A
- root
- peripheral nerve
2
Q
Junction
A
- presynaptic endplate
- synaptic cleft
- post-synaptic membrane
3
Q
Repolarization
A
- Na channels begin to close
- Slow K+ channels open more
- Re-establish RMP
4
Q
Voltage-gated channels
Na+
A
- fast
- depolarization causes conformational change in activation gate
- voltage increase closes inactivation gate, slower
- Inactivation gate won’t reopen until RMP is reestablished
5
Q
Voltage-gated Channels
K+
A
- slow
- depolarization opens gate
- opens at time of Na+ gate closing
6
Q
Calcium
A
- deficit causes Na+ channels to become activated w/ little increases in membrane potential
- Low Ca = excitability = tetany
7
Q
Action potential generation
safety factor
A
- All-or-nothing principle
- Refractory period:
- due to Na channels becoming inactivated
- new AP can’t occur in an excitable fiber as long as membrane is still depolarized from preceeding AP
8
Q
Inhibition of Excitability
A
- high extracellular Ca
- decreases membrane permeability to Na and reduces excitability
- local anesthetics
9
Q
Presynaptic terminal
A
- Neurotransmitter vesicles
- excitatory or inhibitory
- Mitochondria
- ATP for transmitter synthesis
- AP depolarizes presynaptic membrane
- opens voltage-gated calcium channels
- amount of Ca inflow directly related to transmitter release
10
Q
Postsynaptic Receptors
A
- Excitation
- opening Na channels
- dec cond thru Cl/K channels
- internal metabolic changes to excite cell activity
- Inhibition
- opening Cl channels
- inc K out of neuron
- activation of receptor enzymes to inhibit cellular activity
11
Q
Neurotransmitters
A
- Small-molecule, rapidly acting
- class I: Ach
- class II: Amines (NE, Eip, dopamine, serotonin, histamine)
- class III: Amino acids (GABA, Gly, Glutamate, Aspartate)
- class IV: NO
- Neuropeptides, slowly acting or growth factors
- hypothalamic-RH (TRH, LHRH, somatostatin)
- pituitary peptides (ACTH, GH, ADH)
- peptides GI, brain (enkephalins, gastrin, VIP, insulin, glucagon)
- other (bradykinin, angiotensin II)
12
Q
Acetylcholine
A
- recycled
- usually excitatory
13
Q
Norepinephrine
A
- not recycled
- enzymatic destruction: monoamine oxidase
14
Q
Synaptic transmission
A
- Fatigue
- dec in d/c of postsynaptic neuron
- pH
- alkalosis increases excitability
- acidosis depresses it
- Drugs
- caffeine, theophylline, theobromine reduce threshold
- strychnine - inhibits glycine in spinal cord
- anesthetics inc threshold for excitation, decreasing transmission
15
Q
electrolyte important in skeletal muscle contraction
A
Ca
16
Q
Autonomic Neurotransmitters
Cholinergic
Adrenergic
A
- Cholinergic fibers secrete acetylcholine
- all preganglionic neurons are cholinergic:
- ACh excitatory to all postganglionic neurons
- all preganglionic neurons are cholinergic:
- Adrenergic fibers secrete norepinephrine
17
Q
Most PS postganglionic nerons are
A
cholinergic
18
Q
Most Symp postganglionic neurons are
A
adrenergic
19
Q
Acetylcholine Receptors
Muscarinic
Nicotinic
A
- Muscarinic
- found on all effector cells stimulated by postganglionic cholinergic neurons of sympathetic or PS systems
- Nicotinic
- found in autonomic ganglia at synapses between pre- and postganglionic neurons of sympathetic and PS systems
- also present at NMJs
20
Q
Adrenergic receptors
A
- Alpha 1, 2
- NE excites mainly alpha, less beta
- Epi excites alpha and
- Beta 1, 2
- Epi excites beta
21
Q
Reflex arc
A
- Monosynaptic
- polysynaptic with multiple interneurons more common
- Receptor endings of primary afferent axon
- Cell body in DRG
- Synapses on efferent neuron in ventral horn
- Motoneuron axon passes out into spinal nerve to effector organ
22
Q
Motor Neurons
A
- Alpha
- innervates skeletal muscle
- a single alpha nerve fiber excites 3-several hundred muscle fibers (motor unit)
- Gamma
- transmit impulses through smaller nerves
- intrafusal muscle fibers to control muscle tone
- Interneurons
- present in spinal cord gray matter
- renshaw cells - lateral inhibition of motor neurons
23
Q
The Lower Motor Neuron
A
- Efferent neuron of the PNS that connects the CNS with the muscle to be innervated
- The alpha motor neuron
- General somatic efferent (GSE)
- striated skeletal muscle
- all spinal nerves
- CN III, IV, VI, VII, IX, X, XI XII
- General visceral efferent (GVE)
- smooth and cardiac muscle and glands
- sympathetics: all spinal and splanchnic nerves
- parasympathetics: sacral spinal nerves
- CN III, VII, IX, X, XI
- General somatic efferent (GSE)
24
Q
Forebrain
A
- Cerebrum
- Cerebral cortex
- Hippocampus
- Basal nuclei
- Diencephalon
- Thalamus
- Hypothalamus
25
Q
Midbrain (Mesencephalon)
A
- CN III
- CN IV
- Rostral and caudal colliculi
26
Q
Cerebellum & Brainstem
A
- CN V-XII
- Motor tracts
- Proprioceptive tracts
- Connected to CN VIII
- Unconsious proprioception
- Inhibitory
27
Q
Rostral fossa
A
- Cerebrum
- Diencephalon
28
Q
Caudal Fossa
A
- Cerebellum
- midbrain
- brainstem
29
Q
LMN signs
A
- Loss of reflexes
- Loss of tone
- Paresis to paralysis
- Weak and Floppy
30
Q
UMN signs
A
- N/ inc reflexes
- Increase in tone
- Paresis to paralysis
- Weak and stiff
31
Q
Proprioception
A
- postural responses
- most pathways on periphery of the spinal cord
- susceptible compressive lesions
32
Q
Conscious proprioception
A
- goes to cerebral cortex
- awareness without vision
33
Q
Unconcious proprioception
A
- goes to cerebellum
- regulatory, awareness of degree of movement
34
Q
Pain
A
- Perception of nociception
- most resistant to compression
- usually last to go
35
Q
Gait
A
- In most quadrapeds controlled from midbrain and brainstem descending pathways
36
Q
A
