Physiology Quiz 3 (1/2) Flashcards
EPSP
Excitatory Pre/post synaptic Neuron
IPSP
Inhibitory Pre/post synaptic neuron
What do IPSPs do?
Hyperpolarizes the membrane of the synapse
- stops/slows action potential
- more action potentials/sec = more hyperpolarization
What do EPSPs do?
Moves membrane closer to threshold without accommodation.
-speeds up synaptic transmission
Dale’s Law
One nerve cell makes only one neurotransmitter and utilizes only one neurotransmitter
Gamma-Aminobutyric Acid
AKA GABA
Common inhibitory neurotransmitter
What determines excitatory vs inhibitory properties
Depends on the combination of neurotransmitter and receptor
-eg. Norepinephrine- inhibitory on certain receptors and excitatory on others
How is nerve-nerve transmission different from nerve-muscle transmission?
- multitude of neurotransmitters used in nerve-nerve
- can have inhibition at synapse in nerve-nerve
What does the brain perceive more action potentials as?
More pain
What does the brain perceive less action potentials as?
Less pain
What must IPSPs and EPSPs do in order to have influence on the nerve fiber or cell?
Their small electrical changes must sum
-they sum algebraically
How do IPSPs and EPSPs travel?
Electrotonic conduction
How would you define integration in a neuromuscular system or a neural system?
Process by which a decision is made for what to do (if anything) based upon all the input coming into the nerve cell
-all IPSPs and EPSPs sum and how this changes the nerve membrane will determine whether or not an action potential is fired
General functions that muscles perform
Angular motion (flexion/extension) Linear motion (abdominal contraction for trunk stabilization) Pressure or volume changes (cardiac muscles)
Sarcomere
Functional unit of a muscle
Z-protein
Composes “z-line” and holds actin filaments in place
Myofibrils
Components of a muscle cell
I-band
Straddles 2 sarcomeres and includes the region of the sarcomeres where there are only actin filaments
A-band
Region in the middle of the sarcomere
- encompasses entire length of the myosin filaments
- includes the region of overlap of actin and myosin filaments
H-zone
Middle of the sarcomere
Only area where there are only myosin filaments
M-line
Line of structural proteins (m-proteins) that hold myosin filaments in place
“Thick” filaments of the sarcomere
Myosin
“Thin” filaments of the sarcomere
Actin
Crossbridges
Present on the myosin filaments
-attach to actin filaments during contraction
G-actin
Globular proteins that make up actin filaments
Tropomyosin
Blocks actin from myosin crossbridges when muscle is relaxed
Calcium sensitive
Troponin
Determines the location of the tropomyosin on the actin filament
What is the purpose of the hinges on the myosin crossbridges?
Allow the crossbridges to move and attach to the actin during muscle contraction, or to detach from actin during relaxation
Sarcoplasmic reticulum
Surrounds the myofibrils
Contains fluid almost identical to ECF
Supplies calcium to ICF during muscle contraction
What happens to calcium conductance as an action potential travels over a cell membrane?
Increases
-allowing movement of calcium into cell from outside
Where else does calcium conductance increase when an action potential travels over muscle cell aside from membrane?
Sarcoplasmic reticulum
-allows flow from inside SR to interior of muscle cell
What does calcium do once inside muscle cell?
Attaches to troponin
-troponin moves tropomyosin off the actin and into the “groove”
-allows myosin crossbridges to attach to actin
Muscle contracts
Wen is calcium pumped out of the cell?
When action potentials stop traveling across membrane
-muscle relaxes
LMM
Light meromyosin
Horizontal part of actin chain that makes up crossbridges
HMM
Heavy meromyosin
(Makes up chain that angles outward to attach to actin)
Has 2 subunits (S1 and S2)
-S2 head is part that attaches to actin
What happens in a cramp
Not due to activation of motor neuron
Ionic imbalance causes an action potential which opens up calcium channels and starts crossbridge cycle
ADPs role in crossbridge cycle
(Phase 2) when ADP is attached to S2 head, it has very high affinity to actin
-ADP releases after phase 2
What happens to crossbridge cycle if ATP not present
S2 head will not release from actin (stuck at phase 3)
Muscle stays contracted
Rigor mortis
What happens after S2 head attaches to actin?
S2 head shifts actin toward sarcomere
Muscle shortening
Role of ATP during crossbridge cycle
Aids in resetting of S2 head by giving it low affinity for actin
Are crossbridges synchronous?
No. They are asynchronous . There will be crossbridges in all phases at any given moment during contraction
A+M
Actin and myosin are in close proximity to each other, but are not attached
M.ADP.Pi
Myosin is attached to ATP and inorganic phosphate
A+M.ADP.Pi
Muscle is relaxed
What happens to ATP after it attaches to the S2 head?
It is broken down, producing ADP and inorganic phosphate
What is the energy produced by ATP hydrolysis used for?
Re-cocking the S2 head for more cycling
What is the source of muscle tone?
Low level of spontaneous activity of cross bridges
Intracellular pool
Pool where calcium flows from the SR to ICF
Extracellular pool
Pool where calcium flows from ECF to ICF
