Neurophys Lectures 1-6 (Quiz 1)

Question 1

Rheostasis

Answer 1

Change depending on what body needs (ie during illness/fever)

Question 2

Name three core concepts in Physiology

Answer 2

1. Homeostasis
2. Cell membrane
3. Flow down gradients

Question 3

Define Homeostasis

Answer 3

maintenance of relatively constant internal environment

Question 4

State components of Negative Feedback System

Answer 4

Regulated variable, sensor, set point, comparator, output

Example: rv=room temp, sensor=thermom, comp=thermostat, output=AC, set point=normal range

Question 5

Describe effects of disturbance on negative feedback system

Answer 5

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

Question 6

Define flow

Answer 6

movement of particles from one point to another

Question 7

Describe force behind flow of molecules, ions, fluid, gases

Answer 7

energy gradient (difference in sides) causes flow

Question 8

Explain effect of increasing/decreasing energy gradient on flow

Answer 8

Increase gradient –> increase flow

Decrease gradient –> decrease flow

Question 9

Describe effect of increasing/decreasing resistance on flow

Answer 9

increase resistance –> decrease flow
decrease resistance –> increase flow
inversely related

Question 10

Describe importance of gates in controlling flow

Answer 10

Gates can increase resistance if closed

Can prevent or allow flow depending on conformation

Question 11

Classify neurons according to function, structure, location

Answer 11

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)

Question 12

Identify neuronal structures critical to info transfer

Answer 12

Cell body (soma)
Dendrites
Axon
Presynaptic terminals
Synapse: between two neurons
Neuromuscular junction=between neuron / muscle
Neuroeffector junction=between neuron / other tissue

Question 13

Define role and function of glia cells in CNS / PNS

Answer 13

“nerve glue”
PNS: Schwann cells–myelin
CNS: oligodendrocytes (form myelin sheath for AP conduction)
astrocytes (nutritive, clean-up)
microglial (immune defense)

Question 14

Identify neuronal nuclei (areas) & anatomical components of forebrain, brainstem, spinal cord

Answer 14

Forebrain: cerebrum, basal nuclei, thalamus, hypothalamus
Brainstem- midbrain, pons, medulla
Spinal cord- cervical, thoracic, lumbar, sacral; grey/white matter

Question 15

Describe pathways/mechanisms of spinal cord reflex, myotactic reflex

Answer 15

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)

Question 16

Define system/cellular distribution of bodily fluids/ions

Answer 16

60% water (intracellular fluid) *ions across cell membrane

40% water (extracellular fluid): 20% cardiac chambers, 75% interstitial, 5% trapped epithelial cell space (CSF)

Question 17

Describe structure & function of ion movement across membrane

Answer 17

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/pump

Question 18

Recite mechanisms of ion channel gating

Answer 18

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

Question 19

Provide mechanisms of ion channel function normally, and how it might relate to animal/human dysfunction

Answer 19

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

Question 20

Describe mechanism of membrane potential (Vm)

Answer 20

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

Question 21

Describe influence of Nernst (or equilibrium) potential and driving force on ion movement

Answer 21

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

Question 22

Role of ATPase in Vm

Answer 22

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)

Question 23

Describe ways one can change Vm

Answer 23

Depolarization: decrease (+) & (-) across membrane; Na ions into cell –> decrease Vm
Hyperpolarization: increase (+) & (-) across mem; K ions out–>increase Vm

Question 24

Phases of AP

Answer 24

Threshold potential
Depolarization
Repolarization
After-hyperpolarization

Question 25

Ionic basis of AP, including all phases

Answer 25

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

Question 26

Effects on AP when increase/decrease of internal and/or external Na+ & K+

Answer 26

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=

Question 27

Different refractory periods and how they alter AP discharge frequency

Answer 27

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)

Question 28

Effect of clinically relevant toxins in shape and discharge of AP

Answer 28

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

Question 29

Define ionic mechanisms for AP propagation in an axon

Answer 29

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)

Question 30

Define how myelination alters conduction velocity

Answer 30

Myelin-->high resistance=insulator
Faster AP (conduction velocity) as myelin increases nerve diameter

Question 31

Define characteristics of different sized fibers/axons, and mechanisms for which they differ

Answer 31

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)