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
Binding site for actin
Has ATPase activity
Splits an ATP to yield ADP, Pi, and energy
Endomysium
Reticular CT that surrounds each of the fibers in the fascile
Sarcoplasmic reticulum (SR)
Surrounds each myofibril
Upon electrical stimulation it releases Ca+2 from the lateral sacs
Myofilaments
Action (thin filament)
Myosin (thick filament)
General characteristics of muscle
Excitable tissue
Contracts
Relaxes
Makes up about 40% of the average persons body mass
F-actin
Fibrous actin
Coiled to form a double helix
Made of 200 G-actin
G-actin
Small globular protiens
Has an active site to which myosin binds during contraction
I bands
Light bands consisting of actin only
Connective tissue
Epimysium
Perimysium
Endomysium
Direct phosphorylation of ADP by creatine phosphate (CP)
CP is an extremely high energy molecule that is stored in muscle 1st source of energy Reaction: Creatine phosphate + ADP= creatine + ATP Enzyme: creatine kinase Yield: 1 ATP per creatine phosphate About 15 seconds of activity
Myosin
Each filament has:
a rod like tail consisting of two entwined polypeptide chains
Two heads that have three components each
Binding site for actin
Binding site for ATP
Hinge region
A bands
Dark bands consisting of actin and myosin
Z-disk/line
Protien attachment site for the actin
Myoglobin
Red pigmented oxygen storing protien
Symphyses
2 bones joined by fibrocartilage
Flexible, some movement can occur
Ex: pubic symphyses
Intervertebral disc
Fibrous joints
2 bones are united by fibrous CT
Exhibit very little to no movement at all
Three classifications:
Sutures
Syndesmoses
Gamphoses
Synchondroses
2 bone suited by hyaline cartilage
Little to no movement
Ex: epiphyseal plate
Between the costal cartilage of the 1st rib and the manubrium
Gamphoses
Specialized joints consisting of pegs and sockets
Held together by CT tissue called periodontal ligaments
Ex: between teeth and mandible and maxilla
Cartilaginous joints
Two bones united together by hyaline cartilage or fibro cartilage
Two classifications:
synchondroses
Symphyses
Classes of joints
Fibrous
Cartilaginous
Synovial
Sutures
Seams between skull bones
Very stable
Opposing bones have interlocking processes
Ex: coronal suture between frontal and parietal bone
Syndesmoses
Joins bones to a ligament
Flexible, so some movement can occur
Ex: tibiofibular joint
Periosteum
CT membrane covering the outer surface of bone
Outermost: dense, irregular CT
Innermost: osteoblasts, osteoclots
Sharpey’s fibers
Fontanels
Fibrous membranes holding the bones of the skull together before ossification
Appositional growth
Growth from the outside
Chondroblasts lay down new matrix on the outside of the tissue
Chondrocyte
When the secreted matrix surrounds the condroblast
It matures
Epiphysis
Knobs on the end of long bones
Composed mostly of spongy/cancellous bone
Outer covering of compact bone
4 bone shapes
Long
Short
Flat
Irregular
Irregular bones
Odd shaped
Vertebrae, patella
Haversian canal
Passage way for blood vessels and nerves
Compact bone
Lamellae
Circular layers of the bone matrix
Compact bone
Appendicular skeleton
Function: movement
Upper and lower limbs, shoulder and pelvic girdles
Vitamin D
Needed for absorption of Ca+2 from the small intestine
Deficiency in children can lead to rickets
Adults with the inability to metabolize vitamin D can develop osteomalacia
Diaphysis
Shaft that forms the long axis
Formed mostly of compact bone
Zone of resting cartilage
Nearest to the epiphysis
Contains randomly arranged chondrocytes that are slowly dividing
Scurvy
Characterized by ulceration and hemorrhage of skin because of lack of normal collagen in CT
Zone of hypertrophy
3rd
Chondrocytes produced in zone 2 (proliferation) mature and enlarge
Parathyroid hormone
Synthesized and secreted by the parathyroid gland
Signal for release is low plasma calcium levels
Mobilizes Ca+2 from the bone into the blood
Medullary cavity
In the diaphysis of the long bone
Children- contains red marrow
Adults- contains yellow marrow
Osteoclot
Bone resorbing cell
Epiphyseal plate
Hyaline cartilage between the epiphysis and the diaphysis
Area of growth
At the end of the growth it is transformed into bone and is called the epiphyseal line
Bone growth
Happens in length
New bone is formed on the surface of cartilage
Occurs at the epiphyseal plate
Flat bones
Thin, flat, usually curved
Some skull bones, sternum, ribs, scapula
Calcitonin
Synthesized and secreted by the thyroid gland
Promotes the incorporation of Ca+2 into bone from blood
Sensitive to estrogen levels
Lots of estrogen=lots of calcitonin release=lots of Ca+2 incorporated into the bone
Menopausal women may develop osteoporosis
Zone of calcification
Consists of cartilage matrix mineralized by Ca+2
Hypertrophied chondrocytes die
Blood vessels inner ate the area
CT surrounding blood vessels contain osteoblasts
They deposit new bone matrix on the surface of the calcified cartilage (appositional growth)
Osteon
The structural unit of Compact bone
Axial skeleton
Function: protection and support
Skull, rib cage, vertebral column
Osteoblast
Bone forming cell
Lacunae
The space a chondrocyte occupies
Zone of proliferation
2nd zone
Chondrocytes producing new cartilage through interstitial cartilage growth
Rapid division
Osteomalacia
Softening of the bones as a result of Ca+2 depletion
Long bone structure
Diaphysis Epiphysis Epiphyseal plate Medullary cavity Periosteum Endosteum
4 zones of the epiphyseal plate
Zone of resting cartilage
Zone of proliferation
Zone of hypertrophy
Zone of calcification
Long bones
Longer than they are wide
Most bones of the upper and lower limbs
Vitamin C
Necessary for collagen synthesis by osteoblasts
Deficiency can result in scurvy
Sharpey’s fibers
Secure tendons and ligaments to periosteum
Factors affecting bone growth
Nutrition
Hormones
Canaliculi
Small canals that connect the lamellae to each other and to the central haversian canal
Allows nutrient and waste exchange for the osteocytes
Compact bone
Hormone at regulate the exchange of calcium between blood and bone
Calcitonin
Parathyroid hormone
Osteoporosis
Brittle bones due to a decrease in Ca+2 deposition
General bone characteristics
206 named bones
Each bone is an organ
Made of living tissue (can grow and repair)
Short bones
As wide ass they are long
Bones of the wrist and ankle
Cartilage
Consists of special cells called chondroblasts that produce new cartilage matrix
Endosteum
CT membrane lining inner bone surfaces
Rickets
A disease resulting from reduced mineralization of the bone matrix
Causes bones to “bow”
Interstitial growth
Growth from the inside
Inner chondrocytes rapidly divide, expanding the cartilage from within
