Test 2 - Muscle & Nervous Flashcards
Where is each of the skeletal muscle types found?
- skeletal
- cardiac
- smooth
How does skeletal muscle appear under the microscope?
multinucleated in periphery
striated
long strands
help us move
voluntary
How does cardiac muscle appear under the microscope?
arranged end to end
intercalated discs separate cells
central nuclie
striated
found in heart
involuntary
How does smooth muscle appear under the microscope?
spindle-shaped
central nucleus
no striation
involuntary
in organs
Describe muscle (using terms)
A muscle is made of small myofibrils (made of actin and myosin) that bundle to form a muscle fiber. Multiple muscle fiber bundles are surrounded by endomysium and make up a muscle fascicle. Fascicles are bundles surrounded by perimysium. The entire muscle unit is surrounded by epimysium.
Skeletal muscle red fiber:
slow twitch
Type I - slow oxidative
decrease in mitochondria
decrease ATP
increase myoglobin
fatigue resistant
lighter in H&E
Skeletal muscle white fiber:
fast twitch
Type IIB - fast glycolytic
increases mitochondria
decrease myoglobin
fatigue prone
darker in H&E
breast meat in chicken
Skeletal muscle intermediate fiber
Type IIA - fast oxidative glycolytic
decrease ATP
increase glycogen
fatigue prone
used in anaerobic conditions
stain in b/w others (blend of both)
Describe a sarcomere.
I-band = actin = thin filament
A-band = myosin = thick filament (stays the same)
H-zone = center of sarcomere (decrease in size as muscle contracts)
Z-line = middle of the I band
Tell the entire story of how skeletal muscle contracts.
- initiation: nerve impulses arrive and NMJ (action potential)
- release of Ach, open Ach-gated Na channels and depolarize sarcolemma
- Na enters cell and depolarization spreads
- voltage-center proteins in T-tubules change conformation
- T-tubules release Ca
- Ca diffuse to myofilaments
- Ca binds to troponin which grabs on to tropomyosin (blocks myosin heads) and allows actin and myosin to bind to each other
- Reuptake of Ca leads to contraction ending
Where are intercalated disks located?
cardiac muscle
What is found at intercalated disks that allows them to stain a bit more densely?
3 different junction types (highly specialized)
What are the 3 junction types found at intercalated discs?
- fascia adherens
- maculae adherens
- gap junctions
Fascia adherens
transverse cell-cell - thin filaments of sarcomeres that anchor to plasma membranes
Maculae adherens
like desmosomes… attach cardiac muscle tell to cardiac muscle cell… even under strain
Gap junctions of intercalated discs
pacemaker - how all cells contract together - allows ions to pass
What exactly are Purkinje fibers, and why does the region of Purkinje fibers?
large cardiac conducting cells that are arranged in nodes and fibers - they generate and quickly transmit contractile ion pulse to myocardium in a precise sequence - pacemaker of the heart
When considering cardiac vs. skeletal muscle repair, what is the largest difference in ability to repair?
skeletal muscle - myoblasts are self-renewing and can replace damaged muscle cells (myoblasts -> myotubes -> myocytes)
cardiac muscle - cannot regenerate - injury leads to cell death & replacement with fibrous C.T. (collagen)
What is special about myosin filaments in smooth muscle (compared to skeletal muscle)?
smooth has….
1. specialization for long and slow contraction
2. spontaneous contraction
3. no discrete NMJ
4. feet crawl across slowly - side polar
Somatic nervous system
-efferent motor neurons both CNS & PNS
-functions under conscious control
-sensory & motor innervation
Autonomic nervous system
-visceral autonomic neurons
-involuntary control
-has three divisions (parasympathetic, sympathetic, enteric)
How are the somatic and autonomic nervous systems classified/divided?
by function not by location
Describe the structure of a neuron.
- dendrite - receives info
- cell body - process info
- axon - new info out
Differentiate the 3 neuron types.
- multipolar (motor)
- bipolar- one dendrite and one axon (sensory & integrative)
- unipolar - both branches behave like axon (sensory & integrative)
What are Schwann cells?
myelinate the PNS
What is the significance of the nodes of Ranvier that they create?
increase in concentration of Na channels strengthens the action potential signal as it travels down the axon
What are satellite cells, and where do you find lots of those?
peripheral neuroglia - cuboidal cells that surround neuron cell bodies of ganglia
fx: provides insulation and metabolic exchange
List the supporting cells of the CNS
- oligodendrocyte
- astrocyte
- microglia
- ependyma
Oligodendrocyte
forms myelin in CNS
Astrocyte
provides support (physical and metabolic) - allows substances to pass from vessels to nerves and go across the blood-brain barrier
Microglia
immune response of CNS - phagocytic - found in injury and disease
Ependyma
form “epithelial” linin of fluid-filled cavities - maintains CSF
Supporting connective tissues of the PNS
- endoneurium (around single axon)
- perineurium (bundle of axons wrapped)
- epineurium (wraps the whole bundle/nerve)
Supporting connective tissues of the CNS
- dura mater (dense CT) - right under skull
- arachnoid mater (loose CT; increase ground substance) - has subarachnoid space with CSF and vessels
- pia mater (CT) - sits on brain and invaginates into brain around blood vessels
What is the blood-brain barrier, and why does it exist?
restricts passing of infectious agents into bloodstream of the CNS - tight junctions between endothelial cells (depends on astrocyte function for extra protection)
Describe Wallerian degeneration and repair
degeneration of axon distal to site of injury
Can the PNS & CNS regenerate?
the PNS can regenerate but not the CNS
What are the steps of regeneration in the PNS?
- injury
- macrophages clean up mess (usually necrosis)
- Schwann cells make new myelin sheath
- new axon grows into myelin sheath
Describe the organization of the spinal cord
gray matter (cell bodies=nuclei) surrounded by white matter (axons=tracts)
anterior horn of gray matter: innervates skeletal muscle
posterior horn of gray matter: sensing afferent neurons (dorsal?)
How would you describe the organization of the cerebrum?
6 layers of gray matter made of pyramidal and glial cells make up the cortex with and inside white matter which makes up the medulla
What is the organization of the cerebellum?
- molecular (outside layer) + granular (inside) = cortex
- inside is what matter = medulla
- all covered in pia mater
Are the Purkinje cells in the cerebellum the same as the Purkinje cells of the heart?
No
What are Purkinje cells in the cerebellum?
send inhibitory messages
(their nuclei are at the edge of the granular layer and their processes go into the molecular layer)
