Exam 3 based on Preceptor Review Flashcards
(87 cards)
1
Q
Multipolar Neuron
A
- Most abundant in the body
- Major neuron type in the CNS
- Cell body found on left, many processes, one axon
- Reflex arc?
2
Q
Bipolar Neuron
A
- Rare
- Found in some special sensory organs (olfactory mucosa, eye, ear)
- Cell body in middle, two processes- one dendrite, one axon
- Do not generate action potentials
3
Q
Unipolar Neuron
A
- Found mainly in PNS
- Common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves
- one process extends forming central and peripheral to comprise an axon
4
Q
Dendrites: Functions
A
- convey incoming messages toward cell body as graded potentials (short distance signals)
- In many brain areas, dendrites collect info with dendritic spines
5
Q
Astrocytes: Functions
A
- Support, brace, control chemical environment by neurons
- Play role in exchanges between capillaries and neurons
- Guide migration of young neurons
- Influence neuron functioning
6
Q
Astrocytes: Influence neuron functioning
A
- respond to nerve impulses and neurotransmitters
- Participate in info processing in brain
7
Q
Ependymal Cells
A
- Range in shape from squamous to columnar
- May be ciliated (beat to circulate CSF)
- Line central cavities of brain and spinal column
- Form permeable barrier between CFS in cavities and tissue fluid bathing CNS cells
8
Q
Myelin Sheaths in the CNS
A
- Formed by multiple, flat processes of ogliodendrocytes, not whole cells
- Can wrap up to 60 axons at once
- White matter
- Gray matter
9
Q
Myelin Sheaths in the CNS: White Matter
A
-regions of brain and spinal cord with dense collections of myelinated fibers, usually fiber tracts
10
Q
Myelin Sheaths in the CNS: Gray Matter
A
-Mostly neuron cell bodies and non-myelinated fibers
11
Q
Myelination in the PNS
A
- Formed by Schwann cells
- Myelin Sheath
- Myelin sheath gaps
12
Q
Myelination in the PNS: formed by schwann cells
A
- wrap around axon in jelly roll fashion
- one cell forms one segment of myelin sheath
13
Q
Myelination in the PNS: myelin sheath
A
-concentric layers of schwann cell plasma membrane around axon
14
Q
Myelination in the PNS: myelin sheath gaps
A
- gaps between adjacent schwann cells
- sites where axon collaterals can emerge
- formerly called nodes of ranvier
15
Q
Neuron in Resting State
A
- Na concentration higher on outside of cell
- K concentration higher on inside of cell
16
Q
Neuron in Resting State: Na+ and K+ permeabilities across the membrane are different
A
- K+ loss through abundant leakage channels establish a negative membrane potential
- Na+ entry through leakage channels reduces negative membrane potential slightly
- Na+/K+ ATPases maintain the concentration gradients, resulting in RMP
17
Q
Resting Membrane Potential: Membrane Gates
A
- Large proteins serve as selective membrane ion channels, two types:
1. Leakage (nongated) channels
2. Gated channels
18
Q
Leakage (nongated) channels are
A
always open
19
Q
Gated channels use part of protein changes shape to open/close channel (3)
A
- Chemically gated (ligand gated) channels
- Voltage-gated channels
- Mechanically gated channels
20
Q
Chemically gated (ligand-gated) channels
A
Open with binding of a specific neurotransmitter
21
Q
Voltage-gated channels
A
Open and close in response to changes in membrane potential
22
Q
Mechanically gated channels
A
open and close in response to physical deformation of receptors, as in sensory receptors
23
Q
Depolarization Step 1:
A
- Can only happen if cell is in resting state first
- No ions move through voltage-gated channels
24
Q
Depolarization Step 2: (actual depolarization step)
A
-Sending a signal (AP)
-Inside of cell becomes more positive by moving sodium into the cell (open Na+/close K+ channels)
+30 mV (upward slope)
25
Right at the end of depolarization (technically after)
inactivation gate closes Na+ channel
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Repolarization caused by
K+ flowing out of the cell
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Repolarization means to
return to resting state
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Repolarization: (downward slope)
- Close Na+ channels (prevent more Na+ from entering)
- Open K+ channels
- Move K+ out of cell
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Hyperpolarization caused by
K+ continuing to leave the cell, K channels are a little leaky and Na channel starts to reset
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Action potential
- Sudden reversal of charge
- travels down axon of neuron
- As AP happens, charges reverse
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AP: Step one
special channels called stimulus gated channels in the dendrite open when certain chemicals like neurotransmitters bind
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AP: Step 2
Depolarization
| -channels open to allow Na+ to flood the cell for the neuron to become positive (30mV)
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AP: Step 3
Repolarization
| At 30 mV, Na+ channels close, and K+ channels open so K+ can flood out of the cell and the charge becomes negative again
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AP: Step 4
Hyperpolarization
| K+ floods out so quickly that gives a high negative charge for a short time before resting potential is reached again
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Effect of neuron if too much K+ in the blood?
impedes neuronal activity by depolarizing the membrane potential further causing depolarization block
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Effect of neuron if too little K+ in the blood?
hyperpolarization
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What does it mean to excite or inhibit a neuronal impulse?
Neurotransmitter can either help or hinder neuron from firing its own action potential
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Excitatory Neurotransmitters (ANGEA)
- ACh
- Nicotinic
- Glutamate
- E
- Aspartate
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Inhibitory Neurotransmitters (GG)
-GABA
| Glycine
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Neurotransmitters that bind to Ionotropic receptors
ACh
glutamate
glycine
GABA
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Neurotransmitters that bind to metabotropic receptors
???
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What happens to neurotransmitters after they have sent their signal?
...
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What binds cholinergic receptors?
bind ACh
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Cholinergic receptors (N)
- nictotinic
- -skeletal muscle
- -CNS
- -ANS
- -Allow passage of Na and K (Na inflow while K outflow)
- -Post synaptic EXCITATORY potentials
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What binds adrenergic receptors?
Bind catecholamines
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Adrenergic Receptors
- NE
- E
- Linked to G proteins
- alpha and beta receptors
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Cholinergic receptors (M)
- Muscarinic receptors
- -CNS
- -Parasympathetic division of ANS
- - M1, M2, M3, M4, M5
- -Coupled to G proteins and secondary messengers
- -EPSP or IPSP
- --bronchial smooth muscle- contraction (M3)
- --heart- decr rate (M2)
48
In the somatic nervous system, what do all neurotransmitters release?
ACh
49
In the autonomic nervous system, what do all preganglionic fibers release?
ACh
50
In the autonomic nervous system, what do postganglionic fibers release at effectors?
NE or ACh
51
Post ganglionic neuron has what type of receptor?
nictotinic, which binds ACh in autonomic nervous system
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Muscarinic receptors are where? What do they bind?
- heart
- GI system
- bind ACh and g coupled protein receptors
53
Two ways to increase heart rate
1. activate b receptor
| 2. block muscarinic receptor
54
What does GABA do?
??
55
What kind of drug would enhance/inhibit GABA?
??
56
Viscerosensory receptors (5)?
1. Baroreceptors
2. Chemoreceptors
3. Thermoreceptor (temperature)
4. Smooth muscle receptors
5. Nociceptors (pain)
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Viscerosensory receptors: Baroreceptors
detect blood pressure
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Viscerosensory receptors: chemoreceptors
detect arterial oxygen and carbon dioxide
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Viscerosensory receptors: Respiratory epithelium
coughing reflex (inhaled particles)
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Viscerosensory receptors: Smooth muscle receptors
- stretch or tension
- bladder, stomach, intestine
- important for GI motility, micturition
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Viscerosensory receptors: Nociceptors
detect changes in visceral structures caused by abnormal physical conditions
- GI bloating, cramping
- Peritonitis, pericarditis
- stretching, distension, spasm, inflammation, ischemia (loss of blood supply)
- poorly localized
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Horse is dealing with what Viscerosensory receptor?
nociceptor
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Viscerosensory fibers carried by
sympathetic and parasympathetic nerves
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What do parasympathetic nerves do for viscerosensory fibers?
mediate signals from physiologic receptors
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What do sympathetic nerves do for viscerosensory fibers?
mediate signals from nociceptors
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Are viscerosensory fibers part of the ANS?
NO
67
Viscerosensory fiber pathway
1. Enter dorsal horn via sympathetic trunk
2. Synapse with second order neurons in dorsal horn
3. Axons join spinothalamic tract
4. Thalamus
68
What can be said about receptive fields?
???
69
what part of the neurological exam is the paw with toes facing caudally?
proprioceptive positioning
70
What does proprioceptive positioning test?
to see if an animal can recognize the abnormal positioning of the limb and if they can produce adequate voluntary movements to correct it
71
What are the clinical signs of an LMN lesion?
- paresis or paralysis
- disrupts reflex arc
- reflex decr or absent
- decr tone
- rapid atrophy
72
what functions occur with the pontine reticulospinal tracts?
- descends in ventral funiculus of spinal cord
- facilitates motor neurons (a and gama) to extensor muscles
- inhibits motor neurons to flexor muscles
* *ipsilateral extensors
73
what functions occur with the medullary reticulospinal tract?
- lateral funiculus
| - opposite the other one
74
What types of neurons are found in a crossed extensor reflex?
alpha motor neurons
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Where is the rhythmic motor control located?
thoracolumber spinal cord
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What does rhythmic motor control do?
- induce rhythmic and repetitive contraction and relaxation of flexor and extensor muscles
- efficient use of upper motor regulation
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Rhythmic motor control
- walking
- gait cycle
- -two phases
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Two phases of rhythmic motor control
1. swing
| 2. stance
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Swing
foot off ground, leg moves forward
| FLEXORS
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Stance
foot planted on ground, leg moves backwards
| EXTENSORS
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What problems do cats have when afflicted with feline cerebellar hypoplasia?
walking, running, keeping balance and, locating objects
82
Basal Nuclei in general do what?
inhibit target nuclei (dopamine neurons)
83
Basal nuclei malfunctions lead to
deficits in body movements or unwanted movements (mouse)
84
What does atropine do?
-block muscarinic receptor
-block salivary secretions
SO
-incr BP
-incr HR
-decr GI contractility
85
Effects of atenolol on heart?
-decr. HR
-decr. BP
beta blocker
86
What stimulates the adrenal medulla?
fight or flight response
87
What does adrenal medulla release?
E and NE
