Neurophys Lectures 1-6 (Quiz 1) Flashcards
Rheostasis
Change depending on what body needs (ie during illness/fever)
Name three core concepts in Physiology
- Homeostasis
- Cell membrane
- Flow down gradients
Define Homeostasis
maintenance of relatively constant internal environment
State components of Negative Feedback System
Regulated variable, sensor, set point, comparator, output
Example: rv=room temp, sensor=thermom, comp=thermostat, output=AC, set point=normal range
Describe effects of disturbance on negative feedback system
Disturbance comes in–>changes regulated variable–>sensor measures value of variable–>comparator detects if sensor & set point (normal range) are different and controls output–>output=change in system
Example: arterial pressure–>baroreceptors–>CNS–>change HR
Define flow
movement of particles from one point to another
Describe force behind flow of molecules, ions, fluid, gases
energy gradient (difference in sides) causes flow
Explain effect of increasing/decreasing energy gradient on flow
Increase gradient –> increase flow
Decrease gradient –> decrease flow
Describe effect of increasing/decreasing resistance on flow
increase resistance –> decrease flow
decrease resistance –> increase flow
inversely related
Describe importance of gates in controlling flow
Gates can increase resistance if closed
Can prevent or allow flow depending on conformation
Classify neurons according to function, structure, location
FUNCTION-
Sensory: sense enviro change–>send info to CNS
Motor: F-info from CNS–>organs/tissues
Interneuron: F- communicate within area of CNS
Projection: F- communication between areas of CNS
STRUCTURE-
Unipolar: one axon/dendrite (invertebrates)
Bipolar: two axon, multi dendrite (retina in humans)
Pseudo-unipolar: single junction but two ends (sensory paths-ganglion)
Multipolar: single axon, multi dendrites on axon
motor (spinal cord)
pyramidal (hippocampus)
purkinje (cerebellum)
Identify neuronal structures critical to info transfer
Cell body (soma)
Dendrites
Axon
Presynaptic terminals
Synapse: between two neurons
Neuromuscular junction=between neuron / muscle
Neuroeffector junction=between neuron / other tissue
Define role and function of glia cells in CNS / PNS
“nerve glue”
PNS: Schwann cells–myelin
CNS: oligodendrocytes (form myelin sheath for AP conduction)
astrocytes (nutritive, clean-up)
microglial (immune defense)
Identify neuronal nuclei (areas) & anatomical components of forebrain, brainstem, spinal cord
Forebrain: cerebrum, basal nuclei, thalamus, hypothalamus
Brainstem- midbrain, pons, medulla
Spinal cord- cervical, thoracic, lumbar, sacral; grey/white matter
Describe pathways/mechanisms of spinal cord reflex, myotactic reflex
Resting potential–>sensory AP from stimulus(in leg)–>AP conduction x2(PNS-CNS)
Resting potential–>AP–>AP conduction–>NTs–>synpatic (in spinal cord)–>Resting potential–>AP–>AP conduction (CNS-PNS)–>Resting potential–>AP–>AP conduction–>NT–>synaptic–>skeletal muscle (in leg)
(see Claire notes)
Define system/cellular distribution of bodily fluids/ions
60% water (intracellular fluid) *ions across cell membrane
40% water (extracellular fluid): 20% cardiac chambers, 75% interstitial, 5% trapped epithelial cell space (CSF)
Describe structure & function of ion movement across membrane
Function: maintain electrical potential across cell mem.; maintain (Vm) or disturb (AP) steady state
Structure: Diffusion (down gradient, no energy) through channels
Active transport (against gradient, ATP!) through carrier/pumpRecite mechanisms of ion channel gating
Gated channels open/close by changing states in response to signal
Activation: open when depolarized
Inactivation: prevent flow (2nd gate)
Deactivation: closing channel with repolarization
Ligand-gated: conformation change when ligand binds
Provide mechanisms of ion channel function normally, and how it might relate to animal/human dysfunction
Depolarization occurs–>gates open–>repolarization–>gates close
if not open/close properly, ions cannot move through or allow for AP or too much AP
Ex: epilepsy, cystic fibrosis, atrial fibrillation
Describe mechanism of membrane potential (Vm)
Vm is voltage difference across membrane or separation of (+) and (-) ions
Inside cell more (-) than out if no change which is resting potential of mem.
Depolarized=Vm decrease since getting “less negative” closer to 0
Hyperpolarized=Vm increased since farther from 0
Describe influence of Nernst (or equilibrium) potential and driving force on ion movement
Ek=K+ diffuses until equilibrium; Ek= -95mV (ions want out of cell)
Ena=Na+ diffuses until equilibrium; Ena= +62mV (ions want in cell)
Driving force= difference between Vm & Eion
determines direction & magnitude of ion flow
Role of ATPase in Vm
Active transport of Na/K ions across mem
Na-K ATPase if less active–>increase Na+, decrease K+, decrease Vm (move closer to 0)
Maintains Vm (electrogenic)–2 K in, 3 Na out; moves Vm away from Eion (greater driving force)
Describe ways one can change Vm
Depolarization: decrease (+) & (-) across membrane; Na ions into cell –> decrease Vm
Hyperpolarization: increase (+) & (-) across mem; K ions out–>increase Vm
Phases of AP
Threshold potential
Depolarization
Repolarization
After-hyperpolarization
Ionic basis of AP, including all phases
Threshold potential: Vm to reach to create AP
Depolarization: Vm closer to 0, less polarized, more excitable, AP occurs; Na flow in
Repolarization: Vm back to Vr; more polarized, less excitable, K flow out, Na slows/shuts
After-hyperpolarization: Vm falls before Vr after AP
Effects on AP when increase/decrease of internal and/or external Na+ & K+
External Na decreases=hyperpolarization (No AP)
External Na increases=depolarization (more AP)
Internal Na decreases=depolarization- more AP
Internal Na increases=no AP
External K decreases=no AP
External K increases=depolarization (Yes AP)
Internal K decreases=
Internal K increases=
Different refractory periods and how they alter AP discharge frequency
Absolute: no AP no matter stimulus (Na+ channels open & inactive, high K+ current=difficult)
Relative: AP only if stimulus above threshold (enough channels open for AP)
Effect of clinically relevant toxins in shape and discharge of AP
Tetrodotoxin (TTX): Na+ channel blocker, no AP fires
Tetraethylammonium (TEA): K+ channel blocker, 2 APs, no after-hyperpolarization since falling phase due to Na inactivating only
Define ionic mechanisms for AP propagation in an axon
Axon hillock/initial segment: AP initated
Nodes of Ravier: AP occurs at each node because increase Na+ gated channels
AP propagates due to ion movement and depolarization
Na channels–>local current–>depolarization–>more channels open
Ohms Law (V=IxR) Time Constant: less time for ion movement=faster AP conduction Length Constant: greater length=further current (less decay)
Define how myelination alters conduction velocity
Myelin-->high resistance=insulator Faster AP (conduction velocity) as myelin increases nerve diameter
Define characteristics of different sized fibers/axons, and mechanisms for which they differ
Somatic motor: largest diameter/CV = myelinated (up R, down Cm, no change Ri)
Visceral motor: smallest diameter/CV = unmyelinated (down R, up Cm, no change Ri)
