Test 2 (Final) Flashcards
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This reversal is due to changes in membrane permeability
At RMP the membrane is more permeable to K+ than it is to Na+
To generate an AP the membrane becomes more permeable to Na+
To end the AP (so a new one can be generated) the membrane again becomes more permeable to K+
There are _______ chemically and voltage gated channels on the sarcolemma.
Many
Both channel types are
Highly specific for what ion is allowed to pass through
Depolarization
Na+ will Move down its concentration gradient into the cell (Na+ influx)
Na+ brings its positive charge with it, creating intracellular positivity
When Na+ channels close influx stops
In nerve and skeletal tissue
An excitatory stimulus (chemical binding or voltage change) will cause Na+ channels to open
Occurs at RMP, the cell is polarized
Full AP
- Cell is at RMP, then receives an excitatory stimulus
- Voltage opens some Na+ channels; allowing Na+ influx and the cell gradually becomes more positive/less negative
- Voltage allows many Na+ channels to open; allowing an increase in Na+ influx creating a steep incline (spike potential)
- Na+ channels close and K+ channels open, allowing K+ eflux; the cell becomes more negative/less positive
- Excess K+ eflux
- The Na+/K+ pump begins to actively pull K+ back into the cell to restore RMP
Chemically gated ion channels
Open or close when a chemical binds to a protien receptor that is part of the ion channel
Ex: Ach (Acetylcholine) is a neurotransmitter that causes Na+ channels to open
Muscle contraction is the summation of
Many APs (all phases)
At about the same time that Na+ channels close
K+ channels open
The ion will move into or out of the cell based on
It’s concentration gradient (always down)
Voltage gated ion channel
Open or close in response to voltage changes
membrane becoming more positive or negative
Hyperpolarization
A brief period when excess K+ leaves the cell and the membrane temporarily becomes more negative than it was at rest
Repolarization
K+ will move down its concentration gradient out of the cell (K+ eflux)
K+ takes its positive charge with it creating intracellular negativity
AP trace
Represents the voltage across the cell membrane
Measured by comparing the charge of the ICF to the ECF
Technique is called “patch clamping”
Branch of science is called “electrophysiology”
Permeability changes are due to
The opening of protien ion channels in the membrane
AP
The reversal of the resting membrane potential such that the inside of the cell becomes more positive
Excitable tissue
Only contracts in response to electrical activity on the surface of the muscle cell membrane
Epimysium
Dense connective tissue layer around the whole muscle
Also called fascia
Microscopic general characteristics
Each fiber is a long cylindrical cell with multiple oval nuclei
Each muscle fiber is made of many myofibrils
Motor unit
One motor neuron + all the muscle fibers it innervates
Perimysium
CT covering around the bundles of muscle fibers called fasciles
Sarcoplasm
Intracellular fluid
Contains glycosomes and myoglobin
Tropomyosin
Stabilizing protien that winds along a groove in the F-actin strand
General functions of muscle
Body movement (skeletal)
Maintenance of posture (skeletal)
Production of heat as a by product of activity (all)
Constriction of organs and blood vessels (smooth)
Production of heart beat (cardiac)
Glycosomes
Store glycogen for energy
Hinge region
Junction of the head and the tail
Allows the head to bend and straighten during contraction
Transverse tubule (T-Tubule)
Invagination of the muscle cell sarcolemma
Runs between lateral spaces to form a triad (1 t tubule+2 lateral sacs= a triad)
Functions to quickly transmit AP through out the muscle cell
The AP signals the release of Ca+2 from the lateral sacs
Gross anatomy
Connective tissue
Neural innervation
Sarcomer
Structural units of actin and myosin
Functional unit of a muscle
Extends from one Z-disk to another
Striations can be seen under a microscope due to alternating light and dark bands
A bands
I bands
H zone
M line
Sarcolemma
Plasma membrane
Actin
Each myofilament is made of:
Tropomyosin
Troponin
F-actin
Anaerobic respiration/glycolysis
Does not require O2
Involves catabolism of glucose that has been obtained from the blood stream or from the breakdown of glycogen stores in the muscles (within glycosomes)
Reaction: the glucose is broken down into ATP and pyruvic acid
Yield: 2 ATP per 1 glucose
About 30-60 seconds of activity
Troponin
3 polypeptide complex
TnI bonds to G-actin
TnT binds to tropomyosin, anchoring it to the F-actin strand
TnC binds to Ca+2
Muscle metabolism
Continuous muscle contraction requires continuous ATP production
Accomplished via 3 pathways:
Direct phosphorylation
Anaerobic respiration/glycolysis
Aerobic respiration/oxidative phosphorylation
M line
One in the middle of the H zone that holds the myosin in place
Neuromuscular junction
The contact between the axon terminal and the muscle
Functions of ATP
Contraction
Relaxation
Myofibrils
Thread like structures that extend from one end of the muscle to the other
Made of myofilaments
Motor neuron
Specialized nerve cells
Somas are in the spinal cord
Axons extend to muscle fibers
Function: electrically stimulate the muscles to contract
H zone
Band in the middle of the A band
Myosin only
Contraction
Powers the ratcheting movement of the myosin head
After each ratcheting movement a new ATP molecule binds to the myosin head so it can detach, then bind again to the next G-actin molecule
Aerobic respiration/oxidative phosphorylation
Requires O2
Pyruvic acid from glycolysis is transferred to the Kreb’s cycle
Within mitochondria high energy bonds are broken and ATP is released
Yield: 34 ATP per 1 glucose
Hours at activity
+ the 2 from glycolysis
Relaxation
Powers the pump that removes Ca+2 from the sarcomere