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RUSVM Physiology I > Neuro - Part 2 > Flashcards

Neuro - Part 2 Flashcards

1
Q

What are the three parts of the brainstem?

A
  • medulla, pons, midbrain
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2
Q

What are some features of the medulla?

A
  • crucial for life
  • contains centers that regulate:
    • heart rate
    • blood pressure
    • breathing
    • waking and sleeping
    • swallowing
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3
Q

What are some features of the pons?

A
  • influences the cortex to maintain consciousness and alertness
  • influences the regulation of posture, locomotion, and visceral reflexes
  • provides a pathway for the nerve fibers to relay sensory information between cerebellum and cerebral cortex
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4
Q

What are some features of the midbrain?

A
  • location of brainstem UMN pathways, aka extrapyramidal tracts
  • subconscious posture and voluntary skilled/learned movements
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5
Q

What are the different regions of the spine? Functional regions??

A
  • cervical (C1-C8)
  • thoracic (T1-T13)
  • lumbar (L1-L7)
  • sacral (S1–S3)
  • caudal (Cd1-Cd5)

/

  • cervical neck (C1-C5)
  • thoracic limb intumescence (C6-T2)
  • thorax and abdomen (T3-L3)
  • pelvic cavity, pelvic limb intumescence (L4-S3)
  • caudal tail (Cd-Cd5)
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6
Q

What is the structure of the spinal cord?

A
  • transversely tubular, with a small central canal with CSF, anatomically divided into peripheral white matter and central grey matter
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7
Q

What are some features of grey matter in the spinal cord?

A
  • integrative area for cord reflexes**
  • sensory signals enter almost entirely from the sensory roots (dorsal horn)
  • after entering the cord, each signal travels to different locations
    • one branch terminates in grey matter and elicits local reflexes
    • another branch transmits signals to higher levels of the ns (cord/brainstem/cerebral cortex)
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8
Q

What are the components of the PNS?

A
  • composed of all neural tissue outside the CNS
  • receptors, nerves, and peripheral ganglia
  • connect CNS to limbs/organs
    • delivery sensory info to CNS
    • carry motor info to peripheral tissues/systems
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9
Q

What are the kinds of sensory neurons (afferent)?

A
  • Primary/First-Order Neurons (PNS)
    • receive signal + send info to CNS
  • Secondary/Second-Order Neurons (CNS)
    • send impulses from spinal cord/brainstem to thalamus, switches sides (ex: L to R)
  • Tertiary/Third-Order Neurons (CNS)
    • conduct impulses from thalamus to primary somatosensory cortex
  • Quaternary/Forth-Order Neurons (CNS)
    • located in sensory area of the cerebral cortex
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10
Q

What are the kinds of motor nerves (efferent)?

A
  • upper motor nerve (UMN)
    • completely contained in CNS
  • lower motor nerve
    • cell body in CNS, axons in PNS
    • ** except for post-ganglionic autonomic motor neuron
    • completely in PNS
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11
Q

What are ganglia?

A
  • bunch of nerve bodies outside the CNS
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12
Q

What is the organization of nerve fibers?

A
  • just like muscle fibers!
  • nerve fiber (axon + myelin sheath) < endoneurium (CT) < fascicle < perineurium (CT) < peripheral nerve < epineurium (CT)
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13
Q

What are the three main components of a spinal nerve?

A
  • roots (dorsal + ventral)
  • main trunk
  • peripheral branches
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14
Q

What are some features of spinal nerves?

A
  • communicate w/ spinal cord via sensory receptors, muscles, viscera, and vessels
  • exit the vertebral canal via lateral cerebral foramen of the atlas or via intervertebral foramen
  • each segment of the spinal cord is paired to special nerves (7C, 13T, 7L, 3S, 10-24Cd)
  • neurons innervating the limbs (LMNs) are confined to the cervical + lumbar intumescences
    • cranial part innervates cranial + proximal muscles of the limb
    • caudal part innervates distal + caudal muscles of the limb
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15
Q

T/F: A peripheral ganglion is located distally to each ventral horn

A
  • False; dorsal root
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16
Q

What are the 4 types of fibers present in all spinal nerves?

A
  • somatic sensory neurons
    • enter the cord through the dorsal root
  • visceral sensory neurons
    • ener the cord through the dorsal root
  • somatic motor neurons
    • exit the cord through the ventral root
  • visceral motor neurons
    • exit the cord through the ventral root
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17
Q

After leaving the intervertebral foramen, the main trunk gives off a __________ and ___________ branch, which connects the ____________________ with the spinal nerve.

A
  • dorsal + communicating
  • sympathetic trunk ganglion of the sympathetic chain
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18
Q

What are some features of cranial nerves?

A
  • 12 pairs innervate the head and extend into the body
    • most arrive in brainstem
  • individual nerves have specific sensory and/or motor, somatic, or autonomic functions
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19
Q

What are the three meninges?

A
  • dura mater, arachnoid, pia mater
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20
Q

What are characteristics of dura mater?

A
  • “hard mother”
  • outermost meningeal layer
  • often fused with inner surface of skull
  • thicker, protects CNS
21
Q

What are characteristics of arachnoid?

A
  • “web form”
  • spider web appearance, extensive network of trabeculae that join pia mater
  • thin, loose, connective tissue layer
  • subarachnoid space between arachnoid and pia matter that traps CSF to be absorbed
22
Q

What are characteristics of pia mater?

A
  • “soft mother”
  • innermost meningeal layer
  • adheres to surface of CNS
23
Q

What are some features of blood supply for the CNS?

A
  • CNS is 2% of body weight, but receives 20% of cardiac output due to high metabolic rate
  • oxygen requirements for synapses and cell bodies are greater than for axons, grey matter gets more blood than white matter
  • association/integration areas have higher requirements than other areas (ex: forebrain is more vascular)
  • CNS and meninges drained by veins and sinuses
24
Q

What are the regions of the ventricular system?

A
  • lateral ventricles (2): oriented longitudinally in each hemisphere, connected to the 3rd
  • third ventricle: surrounding the interthalamic adhesion and connected to the 4th
  • fourth ventricle: connected with the subarachnoid space and central canal of spinal cord
25
Q

Where is CSF stored?

A
  • subarachnoid space, ventricular system, central canal through core of spinal cord
26
Q

What are some functions of CSF?

A
  • clear fluid w/ several functions:
    • protect brain/spinal cords against impact w/ surrounding bone
      • effective waste control system that can remove potentially harmful cellular metabolites
    • act as brain distribution system for some peptide hormones/growth factors
    • maintain a consistent extracellular micro environment for neurons and glia
27
Q

How do neurons and neuroglia recieve essential materials?

A
  • capillaries in choroid plexus: provide micronutrients
  • interstitial capillaries: provide O2 + substances consumed in large amounts
28
Q

Where is CSF produced?

A
  • mostly the choroid plexus of the ventricles:
    -cauliflower like growth of capillaries covered by a thin layer of modified ependymal cells
  • ependymal lining of ventricles
  • glial limiting membrane between brain/spinal cord and pia mater
29
Q

What kind of junction is found in epithelial cells?

A
  • tight junctions
  • seal gap between epithelial cells
    • seal intercellular space from luminal environment
    • not absolute: impermeable to macromolecules, permeable to ions and some other small molecules
  • most apical location
  • found in epithelial cells (ex: lining interstitial mucosa, bladder etc.)
30
Q

How many times does CSF replace in a day? What are some features of this?

A
  • rate of formation, flow, and absorption allows for replacement ~ 4 times/day
  • formation is fairly constant and independent of changes in pressure
  • most of the CSF is absorbed from the subarachnoid space into the venous sinuses through arachnoid villi; small finger-like projections of the arachnoid membrane that poke through the dura mater in the lumen of various sinuses
31
Q

Why does the choroid epithelium form a selective tight-junction barrier?

A
  • to control the composition of CSF that enters the ventricles
    • created from blood plasma
    • 99% water, other %’s of ions, almost NO proteins , micronutrients
32
Q

What is the pathway of CSF secretion?

A
  • water in choroid epithelial cells combines w/ intracellular CO2 produced by cell metabolism to form H+ and HCO3-
  • at the basal surface, H+ is exchanged for extracellular Na+ from blood
  • influx of Na+ results in excess positive charge
  • to neutralize this Cl- and HCO3- move into ventricles
  • Na+ is pumped out through apical surface into the ventricles
  • water also diffuses into the ventricles to maintain osmotic balance
33
Q

Absorption of CSF is _________ and __________

A
  • pressure dependent + unidirectional
  • from subarachnoid space to venous outflow system
34
Q

Where is the blood brain barrier and blood-CSF barrier located?

A
  • barriers located at both the choroid plexus and at tissue capillary membranes in all areas of brain
  • exception some areas like hypothalamus and pituitary gland that have sensory receptors that respond to changes in body fluid like osmolity or glucose concentration
35
Q

What causes the blood brain barrier to be low permeability?

A
  • the manner in which the cells are joined to one another, via tight junctions
  • astrocytes form a perivascular end foot around the entire outer surface of the capillary end; the interactions between the astrocytes + endothelial cells are important for bbb maintenance
36
Q

What is the permeability of the BBB?

A
  • highly permeable to water, CO2, O2, and most lipid-soluble substances (ex: alcohol + anesthetic)
  • slightly permeable to plasma proteins, and non-lipid-soluble large organic molecules
37
Q

How does the brain receive certain nutrients that are restricted by the BBB?

A
  • glucose: uses GLUT 1 and facilitated diffusion
  • large neutral amino acids: some are precursors for neurotransmitters, use facilitated diffusion
  • small neutral amino acids: synthesized in the CNS
38
Q

What do dendrites do? Axons?

A
  • integrate incoming information and determine whether action potentials will be produced by the neuron
  • ability to transport cargo either direction via cytoskeleton and different proteins
39
Q

What are the kinds of synapses?

A
  • chemical
    • MOST COMMON, usually unidirectional transmission; presynaptic neuron secretes a neurotransmitter that will act on receptor proteins in the postsynaptic neuron (excitatory or inhibitory)
  • electrical
    • cytoplasm of adjacent cells is directly connected by clusters of ion channels called gap junctions, bidirectional transmission, coexist and interact with chemical synapses, promote synchronous firing of interconnected neurons
40
Q

What are the two kinds of neurotransmitters?

A
  • conventional: share basic features; stored in vesicles, released when Ca2 enters axon in response to AP, act by binding to receptors on membrane of postsynaptic cell (small + large molecule neurotransmitters)
  • unconventional: several classes that dont follow usual rules; not stored in vesicles, can carry signals backwards, not dependent on receptors (ex: endocannabinoids, gasotransmitters)
41
Q

What are types of synapse interfaces?

A
42
Q

Differentiate between ionotropic and metabotropic receptor proteins

A
  • ionotropic
    • neurotransmitter receptor that directly gates ion channels:
      • cation channels - opened by excitatory neurotransmitters, induce depolarization (ex: Na+ channels)
      • anion channels - opened by inhibitory neurotransmitters, induce hyperpolarization (ex: Cl- channels)
  • metabotropic
    • neurotransmitter receptor that act through second messenger systems
      • G-protein coupled receptors - open specific ion channels in postsynaptic membrane, activate cAMP, activate intracellular enzymes, activate gene transcription
43
Q

How are graded potentials initiated?

A
  • a neuron receives hundreds of inputs from other neurons in response to neurotransmitters from presynaptic neurons
  • brief local changes in post-synaptic membranes are generated (graded potentials)
44
Q

The amplitude of graded potentials is __________________ to the intensity of the stimulus applied at synaptic sites

A
  • directly proportional
  • each synaptic site generates graded potentials, thousands of graded potentials occur at cell bodies and dendrites and travel to reach the axon hillock/trigger zone
45
Q

What is the trigger zone?

A
  • axon hillock
  • where graded potentials are integrated to generate action potentials, this zone is more sensitive to the depolarizing action of local currents
  • in order to initiate an action potential, graded potentials must reach a certain level: threshold potential/threshold voltage (-55 mV)
  • once the sum of graded potentials exceeds the threshold, an action potential will be triggered. AP propagates along axon. **if depolarization does not reach threshold, no AP will occur, then graded potentials decay.
46
Q

Graded potentials modulate the postsynaptic neuron by shifting the resting membrane potential, through _______ and ________

A
  • excitatory postsynaptic potentials EPSP (shift TOWARDS threshold potential)
    • depolarization (shift MP toward more +), excitatory neurotransmitters open cation channels, ex: glutamate
  • inhibitory postsynaptic potentials IPSP (shift AWAY FROM threshold potential)
    • hyperpolarization (shift MP toward more -), inhibitory neurotransmitters open anion channels, ex: GABA
47
Q

What are the two modes of summation?

A
  • spatial summation
    • graded potentials induced by different synapses summate in the postsynaptic neuron, SIMULTANEOUS summation of IPSP & EPSP graded potentials also occur
  • temporal summation
    • successive discharges from a single presynaptic terminal summate in the PS neuron if they are rapid enough
48
Q

What is saltatory conduction?

A
  • all AP generated at the trigger zone are identical and propagate without losing strength
  • AP occur only at nodes of ranvier in myelinated fibers, “jump” aka REGENERATE from node to node, electrical current flows through axoplasm inside the axon

RUSVM Physiology I (7 decks)

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