AP1 Exam 2 Flashcards
Hypodermis
aka subcutaneous layer
NOT part of the skin
Functions of the skin
Protection
Absorbs
Excretion
Thermoregulation
Cutaneous sensation
Synthesis of Vitamin D
A mole:
aka Nevus
benign overgrowth of melanocytes
Most cells in the epidermis are:
Keratinocytes
Melanocytes
contain special organelle called melanosome: synthesize melanin from the amino acid tyrosine in the presence of the enzyme tyrosinase
produce melanin and transfer to keratinocytes
melanin protect the DNA within keratinocytes
Merkel cells and tactile discs function in the:
sensation of touch
Layers of the epidermis
Stratum corneum
Stratum lucidum (not present everywhere)
Stratum granulosum
Stratum spinosum
Stratum basale
Keratinocytes
have intermediate filaments called tonofilaments composed of a protein that will later form keratin
continuously undergo mitosis and migrate to more superficial layers
Transition between the deeper living cells and the more superficial dead cells: which layer?
Stratum granulosum
Stratum granulosum
transition from living to dead keratinocytes
filled with granules of keratin
lamellar granules release a waterproofing lipid solution
Where is stratum lucidum located?
Fingertips
Palms
Soles
*cells are lucid/clear
Dermis consists of:
irregular CT with collagen and elastic
contains blood vessels, nerves, glands, hair follicles, and Arrectores pilorum muscles
Dermis is divided into two regions:
Papillary region (more superficial): connects the dermis to the epidermis
Reticular region
Sudoriferous gland
aka sweat gland
two types: eccrine and apocrine
Dermal papillae within the papillary region of the dermis greatly increase ______ ______.
surface area
allows for better adhesion to epidermis
more SA for diffusion
Touch corpuscles
Meissner corpuscles
Free nerve endings:
sensation of warmth, coolness, pain, tickle, itch
Subcutaneous layer
aka hypodermis
more fibers than cells: attach dermis to deeper tissues
larger blood vessels
pacinian aka lamellated corpuscles: sense pressure
lamellated corpuscle
aka pacinian corpuscle
sense pressure
Epidermal ridges
aka fingerprints
develop during 3rd and 4th fetal months as the epidermis conforms to the contours of the underlying dermal papillae
Skin color is due to the combination of these 3 pigments:
Melanin: amount and expression is genetically determined
Carotene: amount and expression is genetically determined
Hemoglobin
The number of ______ is about the same in all races. It is the amount of ______ produced and distributed that contributes to differences in skin color. Increased exposure to UV light increases enzymatic activity of ______.
melanocytes
melanin
melanosome: increased melanin production leads to tan
Carotene:
yellow-orange pigment
precursor to vitamin A (used to synthesize pigments for vision)
Hair picture
The hair follicle is located in the:
dermis
Hair matrix
produces new hair cells and push the growing hair through the pilary canal
Associated with hairs are:
sebaceous glands
arrector pili muscle
hair root plexuses: group of dendrites and nerve fibers endings that form a network around a hair follicle; sensitive to touch when hair shaft is moved
Each nails consists of:
nail body
free edge
nail root
Nail picture
Nail matrix:
epithelium deep to the nail root
produce new keratinocytes
Sebum
secreted by sebaceous glands
keeps hair from drying
prevents excessive evaporation of H2O
inhibits growth of some bacteria
Eccrine sweat glands
merocrine glands
more common and found in most places
Apocrine sweat glands
apocrine gland
found in association with hair that develops at puberty (axilla, groin, beard)
Psoriasis
keratinocytes divide and move more quickly than normal from the stratum basale to the stratum corneum and are shed prematurely
make an abnormal keratin: forms flaky, silvery scales (most common on knees, elbows, and scalp)
Most common carcinoma:
basal cell carcinoma
Three forms of skin cancer:
Basal cell carcinoma (most common)
Squamous cell carcinoma
Malignant melanoma (least common, most threatening)
*all are attributed to excessive sun exposure
Albinism
inherited INABILITY of an indiv. to produce melanin
most cases: unable to synthesize tyrosinase
Vitiligo
partial/complete loss of melanocytes from patches of skin
irregular which spots
may be an autoimmune disorder attacking melanocytes (no apparent genetic link)
Jaundice caused by a buildup of ______
bilirubin
Striae are caused by:
aka streaks aka stretch marks
rapid stretching and tearing of dermis (puberty, weight gain, pregnancy)
first appear as purple or reddish lines (tearing of vessels in dermis)
Alopecia
partial/complete lack of hair (from aging, chemo, etc.)
Wound healing
Epidermal wound healing: return to normal function
Deep wound healing: loss of some function; scar tissue formation (fibrosis)
Epidermal wound healing
only epidermal involvement
basal cells break away from basement membrane
they migrate into the wound until they are in full contact (as a sheet moving up from the bottom)
contact inhibition: once they are in contact they stop migrating; mitosis of basal cells is stimulated
return to normal function
Stages of deep wound healing
Inflammatory phase: blood clot, increased blood flow and permeability, WBCs and mesenchymal cells move into the area; scab formed
Migration phase: epithelial cells form bridge, fibroblasts move into area and produce collagen
Proliferative phase: growth of epidermal cells, increased collagen, regeneration of blood vessels
Maturation phase: collagen fibers become organized, fibroblasts decrease, blood vessels normal, scab sloughs off
Degrees of burns
First degree: only epidermal involvement; no blisters
Second degree (partial thickness): part of dermis involved, blisters, scarring
Third degree (full thickness): deep into dermis, lose deep nerve endings (numbness), edema, vary in appearance
*rule of 9’s is only for 2nd and 3rd degree burns
Eczema
inflammation of the skin
characterized by patches of red, blistering, dry, extremely itchy
Wart
mass produced by uncontrolled growth of epithelial skin cells
caused by papillomavirus
Hirsutism
condition of excessive body hair
Lanugo
cover the body of the fetus
fine, nonpigmented, downy hairs
Terminal hairs
coarse, heavily pigmented hair
hair of head, eyebrows, eyelashes (secondary characteristic)
Vellus hairs
short, fine, pale hairs
develop on most of the body during childhood
Cartilage consists of:
ground substance of chondroitin sulfate (provides plasticity)
dense network of collagen (provides strength) and elastic fibers
chondrocytes reside in spaces called lacunae (little lakes)
no blood vessels (slow healing and growth)
Cartilage is covered by CT called ______
Perichondrium>>once vascularized, this becomes periosteum
Types of cartilage
Hyaline: most abundant, ends of long bones, smooth surface for joint movement
Fibrocartilage: very strong, long thick bundles of collage, disc shaped segment between bones (think intervertebral discs, pubic symphysis)
Elastic: threadlike network of elastic fibers, malleable parts of body (auricle, epiglottis)
Yellow bone marrow is:
adipose connective tissue
triglyceride storage: function of bone tissue
Structure of long bone picture:
*epiphyseal plate (growth plate) in children
*articular cartilage is hyaline cartilage
The bone matrix is made up of:
50% hydroxyapatite (calcium phosphate and carbonate) for hardness
25% water
25% collagen
Osteogenic cells:
mesenchyme
*differentiates into osteoblast
Osteoclasts come from ______ lineage.
WBC (macrophage of bone)
breaks down bone
Compact bone
aka cortical bone
most of the skeleton is compact bone
Spongy bone
aka cancellous bone, trabecular bone
site of hematopoiesis>red bone marrow
spongy bone lessens the overall bone weight
Compact bone picture
Compact bone is arranged in osteons aka Haversian systems: form concentric lamellae
Interstitial lamellae: between osteons
Outer (external) circumferential lamellae: directly deep to the periosteum
Inner circumferential lamellae: line the medullary cavity
Lacunae: small spaces between lamellae housing osteocytes
Canaliculi: channels connecting lacunae, filled with ECF, contain fingerlike projections of osteocytes
Central (osteonic) canal: blood and lymph. vessels run through here
Perforating (Volkmann’s) canals: blood and lymph. vessels run from central canal to outer cortex of the bone
Spongey bone picture
Spongey bone are arranged in a lattice of thin columns called trabeculae.
Still have lamellae, lacunae, and canaliculi just in a different layout
Ossification
aka osteogenesis
process of forming new bone
Osteogenesis occurs by two different methods:
Intramembranous ossification: spongy bone, can be remodeled to form compact, forms flat bones
Endochondral ossification: cartilage (cartilage model) is replaced by bone, forms both compact and spongy bone, formation of most bones, 1 primary and 2 secondary centers of growth
Intramembranous ossification picture
does not go through cartilage stage
Endochondral ossification picture
*1 primary and 2 secondary centers of growth
Ossification contributing to bone length is usually complete by ___to ___ years of age.
18-21
*bones can still continue to thicken and are capable of repair even after epiphyseal plate closure
Bone fractures
Open
Comminuted
Greenstick
Impacted
Vitamin A for bones:
stimulates osteoblasts
Vitamin C for bones:
needed for synthesis of collagen
Vitamin D for bones:
promotes absorption of calcium from foods in the GI tract into the blood
Vitamin K and B12 for bones:
needed for synthesis of bone proteins
Bone resorption
minerals (calcium, phosphate) into the blood
removal of minerals and collagen fibers from bone by osteoclasts
Bone deposition
deposit minerals into bone (calcium, phosphate)
addition of minerals and collagen to the bone by osteoblasts
Abnormally thick and heavy bones
too much new bone tissue is formed (osteoblasts)
acromegaly
Bones are too “soft” or weak
excessive calcium loss from bone (osteoclasts)
osteoporosis, rickets, osteomalacia
Fracture repair
First step: formation of hematoma
2nd/3rd steps: phagocytes remove cellular debris, fibroblasts deposit collagen, formation of fibro-cartilaginous callus followed by a bony callus of spongy bone (osteoblasts from bony callus)
Final step: spongy bone is replaced by compact bone, fracture line disappears but evidence of fracture remains, takes several months
PTH and calcitriol
increase blood Ca2+ levels (osteoclasts)
parathyroid hormone (PTH) produced in the parathyroid glands
calcitriol (active form of Vit. D3) is produced by the kidneys after being stimulated by PTH (causes retention of calcium in kidneys)
Calcitonin
decreases blood calcium levels (osteoblasts)
produced by parafollicular cells of thyroid gland
Joint
a point of contact between:
2 bones
bone and cartilage
bone and tooth
Syndesmoses
more space than a suture; more connective tissue
between tib. fib.
Cartilaginous joints
Synchondroses: hyaline cartilage connecting bones (“bone to bone”); may ossify with age
Symphyses: fibrocartilage connecting bones
Epiphyseal cartilage:
composed of fibrocartilage or hyaline cartilage
no synovial cavity
little or no movement
Synovial joint
articular capsule: dense irregular and regular CT
synovial membrane
synovial fluid
articular cartilage: covers epiphyses of bone; not covered by synovial membrane
may contain articular discs: (menisci)
Fibrous joints
Sutures: thin layer of fibrous CT
Syndesmoses: more space than a suture; more fibrous CT
Gomphoses: teeth in sockets
Rickets and osteomalacia
Results from inadequate calcification of extracellular bone matrix
usually caused by Vit. D deficiency (fix this for prevention and treatment)
Rickets: in children, growing bones become “soft” and are easily deformed; epiphyseal plates fail to ossify resulting in bowed legs and deformities of the skull, rib cage, and pelvis
Osteomalacia: “adult rickets”; new bone formed during remodeling fails to calcify
Myofibril
an organelle in a muscle fiber (myocyte)
basic functional unit of the muscle fiber (made of filaments: actin, myosin)
Muscle arrangement (superficial to deep)
Entire muscle: covered by epimysium
Fascicle: covered by perimysium
Muscle fiber (myocyte): covered by endomysium
Myofibril: full of filaments
Motor unit
group of muscle fibers supplied by a somatic motor neuron
*each muscle fiber is only supplied by 1 neuron thus 1 NMJ
Embryonic muscle development
myoblasts fuse to form one muscle fiber (why they are multinucleated and they cannot undergo mitosis)
Calsequestrin
calcium binding protein inside SR
allows calcium concentration to be 10K times higher than in sarcoplasm (relaxed muscle)
T tubules are open to the outside of the muscle fiber, so they are filled with ______ ______.
Interstitial fluid
Contractile proteins:
actin
myosin
Sarcomere
M line: center of sarcomere
Z discs: end of sarcomere (middle of I band)
A band: length of myosin (never changes length)
H zone: between ends of actin (center of A band); only thick filaments
I band: between ends of myosin (crosses Z line)
Titin
helps sarcomere return to its resting length
connects Z disc to M line
attaches thick filaments to Z discs and M lines
Myomesin
structural protein associated with the M line
Dystrophin
links the thin filaments of the sarcomeres to sarcolemmal proteins (integral membrane proteins)
transmits the tensive forces of the sarcomeres
Sarcolemmal proteins
integral membrane proteins that dystrophin attaches to
How many molecules of Ach cause the Na+ channels to open?
2
Regulatory proteins
Troponin
Tropomyosin
Structural proteins
Titin
Myomesin
Dystrophin
Sarcolemmal proteins
Rigor mortis
“rigidity of death”
cell membranes leak Ca2+ bind to troponin: cross bridges attach
ATP is no longer being produced: cross bridges cannot detach
starts 3-4 hrs after death
disappears ~24 hrs after death: proteolytic enzymes digest cross bridges
Hypertrophy is an increase in the ______ of muscle fibers.
diameter
organelles increase in number
contain more myofibrils from repetitive muscular activity
atrophy is opposite
Hyperplasia
increase in number of cells
Growth of skeletal muscle is stimulated by ______ during childhood.
hormones
ATP production
cells do NOT store significant amounts; must be made at same rate that it is used
production via: creatine phosphate, glycolysis, aerobic respiration
Creatine
need 2g/day
synthesized in liver, kidneys, pancreas and ingested (supplements, milk, red meat, some fish)
more ingested (supplements), less synthesized (can cause dehydration and kidney dysfunction)
Control of contraction
1 nerve impulse= 1 AP in that motor unit
amplitude of AP is always the same but the frequency of stimulation is what increases the force the fibers can produce
Twitch
a brief contraction of all the muscle fibers in a motor unit
What is a myograph?
device used to measure the force generated by a contracting muscle
Myogram:
record of muscle contraction
Wave summation:
when a second stimulus is applied after the refractory period, skeletal muscle will respond to both stimuli
second stimulus occurs (after refractory period) before the muscle is relaxed= second contraction stronger than the first
more Ca2+ is released from SR
Motor unit recruitment:
process whereby the number of active motor units is increased according to need
more neurons stimulated= more motor units stimulated =more motor tension
smallest, weakest motor units are recruited first
Cardiac muscle is regulated by the ANS and the ______ system.
endocrine
Like cardiac muscle, smooth muscle is also ______
autorhythmic
How does smooth muscle generate ATP?
anaerobic respiration (glycolysis)
smooth muscle has a low capacity for generating ATP
Smooth muscle fiber picture
thick, thin, and intermediate filaments
intermediate filaments are attached to dense bodies (functionally similar to Z discs) and found in sarcoplasm and sarcolemma
contraction of thick and thin filaments generates tension on intermediate filaments
What are the two types of smooth muscle?
Single unit (aka visceral smooth muscle): connect to one another by gap junctions and contract as a single unit
Multi-unit: lack gap junctions and contract independently
DOMS
delayed onset muscle soreness
microscopic muscle damage as a major factor (not all contributors are known)
Muscle fatigue
inability of a muscle to maintain force of contraction after prolonged activity (not enough Ach, decreased release of Ca2+, depletion of nutrients, etc)
central fatigue: feelings of tiredness and desire to cease activity; may be protective mechanism
Muscle tone
small amount of tension or contraction that a muscle exhibits even at rest
loss of muscle tone= flaccid
Neuromuscular disease:
somatic motor neuron
NMJ
muscle fiber
term encompasses problems/diseases at any one of these 3 sites
Myasthenia gravis
autoimmune disease
chronic, progressive damage of NMJ
antibodies bind to and block Ach receptors
decreases overall number of functional Ach receptors
Spasm
sudden involuntary contraction of a single muscle that is part of a large group of muscles
Cramp
painful spasmodic contraction
Tic
spasmodic twitch made involuntarily by muscles that are normally under voluntary control
PNS
all nervous tissue outside the CNS
Cranial nerves (12 pairs)
Spinal nerves (31 pairs)
Peripheral nerves
- Divided into two divisions:
- Sensory (afferent)
- Motor (efferent)
- Consists of the: these all have a sensory and motor neurons
- somatic NS
- ANS
- motor portion: SNS and parasympathetic NS
- enteric NS
Somatic nervous system
Motor control of voluntary skeletal muscle
Sensation from body wall, limbs, head, and special senses
Enteric nervous system
Sensation and motor control (smooth muscle, glands) of GI tract
The somatic, ANS, and enteric nervous systems all have both a ______ and ______ subdivision.
sensory
motor
Nerve vs. Tract
nerve: a bundle of neuronal axons in the PNS
tract: a bundle of neuronal axons in the CNS
Ganglion vs. Nucleus
ganglion: a group of neuronal cell bodies in the PNS
nucleus: a group of neural cell bodies (unmyelinated) in the CNS
Plexus
extensive network of nerves found within the PNS
Tremor
rhythmic, involuntary, purposeless, contraction
produces a quivering/shaking movement
Fibrillation
spontaneous contraction of a single muscle fiber
not visible under the skin
can be recorded by electromyography
may signal destruction of motor neurons
Muscle strain
forceful stretching or tearing of muscle fibers
Myotonia
slow relaxation or decreased ability to relax muscle after voluntary contraction
may be accompanied by increased muscular excitability and contractility
Myomalacia
pathological softening of muscle tissue
In neuron, axoplasm and axolemma are synonymous with:
cytoplasm
cell membrane (NOT the same as neurolemma)
Nissl bodies
prominent clusters of RER
specialized form of typical organelle
Neuron picture
- axon: can approximate 3’ long in humans!
In a neuron, impulses (APs) generally arise in the ______ ______.
Trigger zone: the junction of the hillock and initial segment
Axon contains:
Mitochondria
Microtubules: tubulin; participate in moving material between the cell body and axon
Neurofibrils: intermediate filaments; cell shape and support
Does NOT contain RER=no protein synthesis in axon
Axon ______ may branch off main axon.
collaterals
Telodendria
- The axon and its collaterals end by dividing into many fine processes
called axon terminals or axon telodendria end in:- synaptic end bulbs
- varicosities (string of swollen bumps)
Axon terminals contain only some:
contain only some cytosol, mitochondria, cytoskeleton, SER and synaptic vesicles
Things made in the cell body must be transported to axon terminal via:
- Slow axonal transport:
- one way ( from cell body to axon terminal)
- trans. of: axoplasm to growing/regenerating axons
- Fast axonal transport:
- two way
- microtubules as tracks and motors for movement of materials
- trans. of: organelles, materials for axolemma, synaptic vesicles and end bulb
Nerve fiber relationship within a nerve (picture)
consists of axon plus myelin sheath (if present)
the endoneurium surrounds the nerve fiber (to include the myelin sheath when present)
Structural classification of neurons (picture)
Multipolar neurons: several dendrites and only one axon; located throughout the brain and spinal cord; majority of neurons in human body
Bipolar neurons: one main dendrite and one axon; utilized/located in special senses (retina, inner ear, olfactory)
Pseudounipolar neurons: one process extends from the body and divides into a central branch that functions as an axon as a dendritic root; employed for general SENSORY neurons that convey touch and stretching information
Neuroglia are NOT ______ cells.
excitable
*neuroglia will fills the spaces formerly occupied by neurons in cases of injury or disease
Neuroglia of CNS
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
Neuroglia of PNS
Schwann cells (neurolemmocytes)
Satellite cells
Neurons do not undergo ______ but neuroglia do.
mitosis
Myelin
multi layered complex of lipids and proteins (layers of plasma membranes)
prevents loss of electrical signal=speeds up conduction of nerve impulses
PNS: Schwann cells
CNS: oligodendrocytes
Schwann cell (neurolemmocyte) and myelination
Myelinates a segment of an axon in PNS
multiple layers surround the axon
the outer nucleated cytoplasmic layer of the Schwann cell is called the neurolemma (only in PNS)
A Schwann cell (neurolemmocyte) or an oligodendrocyte can be associated with neuron, yet the neuron may be unmyelinated: explain
If they are just associated (but not wrapped several times) they are just referred to as their cell name: Schwann cell, oligodendrocyte
does NOT = myelination
Schwann cell or oligodendrocyte must be wrapped its plasma membrane around the axon many times= myelination
Neurolemma
outer layer of myelinating Schwann cells
contains the nucleus and all cytoplasm
found only around axons in PNS
not to be confused with axolemma
Nodes of Ranvier
gaps between myelinating cells (no myelin)
only on nerve fibers supplied by potentially myelin producing cells
Myelination in the CNS:
no neurolemma
there are nodes of Ranvier
one oligodendrocyte can myelinate multiple times (several segments or several different axons)
White vs. Gray matter
White: myelin (myelinated tract fibers)
Gray: no myelin; gray color from Nissl bodies (region predominantly filled with cell bodies)
Neurons communicate with one another by using 2 types of electrical signals:
Action potentials: short and long distance; all or none
Graded potentials: short distance (localized) communication only; affect the generation of action potentials
Resting membrane potential (neuron)
-70mV
membrane potential: opposite charges are separated in space; their attractive force is the potential
Types of ion channels (picture)
The cell membrane is impermeable to nearly all ______ charged intracellular molecules
negatively
e.g.: proteins, amino acids, phosphates, chloride (slightly permeable to extracellular Cl-)
Establishment of resting membrane potential
K+ diffuses out of cell
negative particles left inside (neg. charge in cell)
a little Cl- diffuses into the cells
Threshold:
-55mV
voltage gated Na+ channels open
Calcium and membrane potential:
Calcium ions appear to bind to exterior surfaces of sodium channel protein molecule
Positive charge of calcium alter the electrical state of the channel protein= increased voltage level required to open the gate
Less calcium means the threshold will be lower than normal (easier to depolarize; highly excitable)
Propagation (conduction)
nerve impulses must travel from where they arise at a trigger zone down the neuron to the axon terminals
depends on positive feedback
think of it as a wave of depolarization moving toward the axon terminal
Continuous conduction:
step by step depolarization and repolarization of adjacent segments of the axon
Saltatory conduction:
special mode of impulse propagation that occurs along myelinated axons
jump from one node of Ranvier to the next where voltage gated channels are concentrated
much faster than continuous
requires less ATP (more efficient)
A, B, C fibers
A: large, myelinated (fastest)
B: medium, myelinated (fast)
C: small, unmyelinated (slow)
*the greater the diameter the faster the conduction
Light touch vs. firm pressure
light touch: low frequency, widely spaced impulses; stimulates only a few pressure sensitive neurons
firm pressure: higher frequency; stimulates more pressure sensitive neurons
Synapses and homeostasis:
contribute to homeostasis by providing evaluation and integration of stimuli
physically changed with repeated use (learning)
most neurons are both pre and post synaptic neurons
Types of synapses:
electrical: pre and post synaptic neurons are in physical contact; AP/ions flow through gap junctions (heart and GI); faster than chemical
chemical: pre and post s. neurons are NOT in physical contact; AP travels via neurotransmitter
Axo-
dendritic
somatic
axonic
Chemical synapse signal transmission (picture)
How are neurotransmitters removed?
Enzymatic degradation
Reuptake/uptake
Diffusion
uptake vs. reuptake
uptake: neurotransmitter taken up by a cell that did not release it
reuptake: neurotransmitter take up by the same cell that released it
EPSP
Excitatory post synaptic potential
potential that brings the membrane closer to threshold (depolarizing)
inside of the cell becomes less negative
IPSP
inhibitory post synaptic potential
potential that brings the membrane further from threshold (repolarizing)
inside of the cell becomes more negative
Summation
integration/evaluation of synaptic input
occurs at trigger zone
Spatial summation
Temporal summation
Neurotransmitters are divided into 2 classes
small molecule neurotransmitters:
- Ach: can be excitatory or inhibitory (at diff. synapses)
- Amino acids: CNS; can be both
- Biogenic amines: both
- ATP and other purines
- Nitric oxide: formed on demand; vasodilation
neuropeptides: both CNS and PNS; formed in cell body, packaged into vesicles, transported to axon terminals
- opioid peptides; (pain control; enkephalins, endorphins, dynorphins>bodies natural pain killers)
Plasticity
nervous system’s ability to change based on experience and need
neurons can sprout new dendrites, synthesize new proteins, change # of synapses
Neural circuits
simple series: single pre. neuron to single post. neuron; most are far more complex
diverging: amplification of the original signal
converging: results in more effective stimulation/inhibition; e.g. motor neurons
reverberating: reverberations last longer than usual (perhaps used in breathing, awakening, short term mem.)
parallel after-discharge: if summation is excitatory in post. neuron= stream of impulses; precise activities and timing
Regeneration of neurons:
to do any regeneration, neurons must:
be in PNS
have intact cell body
be myelinated by functional Schwann cells having a neurolemma: neurolemma forms regeneration tube that guides and stimulates regrowth of the axon
Demyelination
voltage gated channels are concentrated at nodes of Ranvier
myelin insulates the neuron and allows the depolarization to spread further and faster
destruction of myelin (demyelination) means the depolarization does not reach the next node of Ranvier
examples: MS (CNS; progressive destruction>scleroses) and GBS (PNS; macrophages strip myelin)
Local anesthetics work by blocking:
block the opening of voltage gated Na+ channels= prevents transmission of pain signals
Rabies is caused by a virus that reaches the CNS via:
fast axonal transport
