AP1 Exam 2 Flashcards
(188 cards)
1
Q
Hypodermis
A
aka subcutaneous layer
NOT part of the skin
2
Q
Functions of the skin
A
Protection
Absorbs
Excretion
Thermoregulation
Cutaneous sensation
Synthesis of Vitamin D
3
Q
A mole:
A
aka Nevus
benign overgrowth of melanocytes
4
Q
Most cells in the epidermis are:
A
Keratinocytes
5
Q
Melanocytes
A
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
6
Q
Merkel cells and tactile discs function in the:
A
sensation of touch
7
Q
Layers of the epidermis
A
Stratum corneum
Stratum lucidum (not present everywhere)
Stratum granulosum
Stratum spinosum
Stratum basale
8
Q
Keratinocytes
A
have intermediate filaments called tonofilaments composed of a protein that will later form keratin
continuously undergo mitosis and migrate to more superficial layers
9
Q
Transition between the deeper living cells and the more superficial dead cells: which layer?
A
Stratum granulosum
10
Q
Stratum granulosum
A
transition from living to dead keratinocytes
filled with granules of keratin
lamellar granules release a waterproofing lipid solution
11
Q
Where is stratum lucidum located?
A
Fingertips
Palms
Soles
*cells are lucid/clear
12
Q
Dermis consists of:
A
irregular CT with collagen and elastic
contains blood vessels, nerves, glands, hair follicles, and Arrectores pilorum muscles
13
Q
Dermis is divided into two regions:
A
Papillary region (more superficial): connects the dermis to the epidermis
Reticular region
14
Q
Sudoriferous gland
A
aka sweat gland
two types: eccrine and apocrine
15
Q
Dermal papillae within the papillary region of the dermis greatly increase ______ ______.
A
surface area
allows for better adhesion to epidermis
more SA for diffusion
16
Q
Touch corpuscles
A
Meissner corpuscles
17
Q
Free nerve endings:
A
sensation of warmth, coolness, pain, tickle, itch
18
Q
Subcutaneous layer
A
aka hypodermis
more fibers than cells: attach dermis to deeper tissues
larger blood vessels
pacinian aka lamellated corpuscles: sense pressure
19
Q
lamellated corpuscle
A
aka pacinian corpuscle
sense pressure
20
Q
Epidermal ridges
A
aka fingerprints
develop during 3rd and 4th fetal months as the epidermis conforms to the contours of the underlying dermal papillae
21
Q
Skin color is due to the combination of these 3 pigments:
A
Melanin: amount and expression is genetically determined
Carotene: amount and expression is genetically determined
Hemoglobin
22
Q
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 ______.
A
melanocytes
melanin
melanosome: increased melanin production leads to tan
23
Q
Carotene:
A
yellow-orange pigment
precursor to vitamin A (used to synthesize pigments for vision)
24
Q
Hair picture
A
25
The hair follicle is located in the:
dermis
26
Hair matrix
produces new hair cells and push the growing hair through the pilary canal
27
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
28
Each nails consists of:
nail body
free edge
nail root
29
Nail picture
30
Nail matrix:
epithelium deep to the nail root
produce new keratinocytes
31
Sebum
secreted by sebaceous glands
keeps hair from drying
prevents excessive evaporation of H2O
inhibits growth of some bacteria
32
Eccrine sweat glands
merocrine glands
more common and found in most places
33
Apocrine sweat glands
apocrine gland
found in association with hair that develops at puberty (axilla, groin, beard)
34
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)
35
Most common carcinoma:
basal cell carcinoma
36
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
37
Albinism
inherited *INABILITY* of an indiv. to produce melanin
## Footnote
**most cases: unable to synthesize tyrosinase**
38
Vitiligo
partial/complete loss of melanocytes from patches of skin
irregular which spots
may be an autoimmune disorder attacking melanocytes (no apparent genetic link)
39
Jaundice caused by a buildup of \_\_\_\_\_\_
bilirubin
40
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)
41
Alopecia
partial/complete lack of hair (from aging, chemo, etc.)
42
Wound healing
Epidermal wound healing: return to normal function
Deep wound healing: loss of some function; scar tissue formation (fibrosis)
43
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**
44
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
45
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
46
Eczema
inflammation of the skin
characterized by patches of red, blistering, dry, extremely itchy
47
Wart
mass produced by uncontrolled growth of epithelial skin cells
caused by papillomavirus
48
Hirsutism
condition of excessive body hair
49
Lanugo
cover the body of the fetus
fine, nonpigmented, downy hairs
50
Terminal hairs
coarse, heavily pigmented hair
hair of head, eyebrows, eyelashes (secondary characteristic)
51
Vellus hairs
short, fine, pale hairs
develop on most of the body during childhood
52
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)
53
Cartilage is covered by CT called \_\_\_\_\_\_
Perichondrium\>\>once vascularized, this becomes periosteum
54
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)**
55
Yellow bone marrow is:
adipose connective tissue
## Footnote
**triglyceride storage: function of bone tissue**
56
Structure of long bone picture:
\*epiphyseal plate (growth plate) in children
\*articular cartilage is hyaline cartilage
57
The bone matrix is made up of:
50% hydroxyapatite (calcium phosphate and carbonate) for hardness
25% water
25% collagen
58
Osteogenic cells:
mesenchyme
\*differentiates into osteoblast
59
Osteoclasts come from ______ lineage.
WBC (macrophage of bone)
breaks down bone
60
Compact bone
**aka cortical bone**
most of the skeleton is compact bone
61
Spongy bone
**aka cancellous bone, trabecular bone**
site of hematopoiesis\>red bone marrow
**spongy bone lessens the overall bone weight**
62
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
63
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
64
Ossification
aka osteogenesis
process of forming new bone
65
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
66
Intramembranous ossification picture
does not go through cartilage stage
67
Endochondral ossification picture
\*1 primary and 2 secondary centers of growth
68
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
69
Bone fractures
Open
Comminuted
Greenstick
Impacted
70
Vitamin A for bones:
stimulates osteoblasts
71
Vitamin C for bones:
needed for synthesis of collagen
72
Vitamin D for bones:
promotes absorption of calcium from foods in the GI tract into the blood
73
Vitamin K and B12 for bones:
needed for synthesis of bone proteins
74
Bone resorption
minerals (calcium, phosphate) **into the blood**
removal of minerals and collagen fibers from bone by osteoclasts
75
Bone deposition
deposit minerals into bone (calcium, phosphate)
addition of minerals and collagen to the bone by osteoblasts
76
Abnormally thick and heavy bones
too much new bone tissue is formed (osteoblasts)
acromegaly
77
Bones are too “soft” or weak
excessive calcium loss from bone (osteoclasts)
osteoporosis, rickets, osteomalacia
78
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
79
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)
80
Calcitonin
decreases blood calcium levels (osteoblasts)
produced by parafollicular cells of thyroid gland
81
Joint
a point of contact between:
2 bones
bone and cartilage
bone and tooth
82
Syndesmoses
more space than a suture; more connective tissue
between tib. fib.
83
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
84
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)
85
Fibrous joints
Sutures: thin layer of fibrous CT
Syndesmoses: more space than a suture; more fibrous CT
Gomphoses: teeth in sockets
86
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
87
Myofibril
an organelle in a muscle fiber (myocyte)
basic functional unit of the muscle fiber (made of filaments: actin, myosin)
88
Muscle arrangement (superficial to deep)
Entire muscle: covered by epimysium
Fascicle: covered by perimysium
Muscle fiber (myocyte): covered by endomysium
Myofibril: full of filaments
89
Motor unit
group of muscle fibers supplied by a somatic motor neuron
\*each muscle fiber is only supplied by 1 neuron thus 1 NMJ
90
Embryonic muscle development
myoblasts fuse to form one muscle fiber (why they are multinucleated and they cannot undergo mitosis)
91
Calsequestrin
calcium binding protein inside SR
allows calcium concentration to be 10K times higher than in sarcoplasm (relaxed muscle)
92
T tubules are open to the outside of the muscle fiber, so they are filled with ______ \_\_\_\_\_\_.
Interstitial fluid
93
Contractile proteins:
actin
myosin
94
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)
95
Titin
helps sarcomere return to its resting length
connects Z disc to M line
attaches thick filaments to Z discs and M lines
96
Myomesin
structural protein associated with the M line
97
Dystrophin
links the thin filaments of the sarcomeres to sarcolemmal proteins (integral membrane proteins)
transmits the tensive forces of the sarcomeres
98
Sarcolemmal proteins
integral membrane proteins that dystrophin attaches to
99
How many molecules of Ach cause the Na+ channels to open?
2
100
Regulatory proteins
Troponin
Tropomyosin
101
Structural proteins
Titin
Myomesin
Dystrophin
Sarcolemmal proteins
102
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
103
Hypertrophy is an increase in the ______ of muscle fibers.
diameter
organelles increase in number
contain more myofibrils from repetitive muscular activity
**atrophy is opposite**
104
Hyperplasia
increase in number of cells
105
Growth of skeletal muscle is stimulated by ______ during childhood.
hormones
106
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
107
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)
108
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
109
Twitch
a brief contraction of all the muscle fibers in a motor unit
110
What is a myograph?
device used to measure the force generated by a contracting muscle
111
Myogram:
record of muscle contraction
112
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
113
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
114
Cardiac muscle is regulated by the ANS and the ______ system.
endocrine
115
Like cardiac muscle, smooth muscle is also \_\_\_\_\_\_
autorhythmic
116
How does smooth muscle generate ATP?
anaerobic respiration (glycolysis)
smooth muscle has a low capacity for generating ATP
117
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
118
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
119
DOMS
delayed onset muscle soreness
microscopic muscle damage as a major factor (not all contributors are known)
120
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
121
Muscle tone
small amount of tension or contraction that a muscle exhibits even at rest
loss of muscle tone= flaccid
122
Neuromuscular disease:
somatic motor neuron
NMJ
muscle fiber
term encompasses problems/diseases at any one of these 3 sites
123
Myasthenia gravis
autoimmune disease
chronic, progressive damage of NMJ
antibodies bind to and block Ach receptors
decreases overall number of functional Ach receptors
124
Spasm
sudden involuntary contraction of a single muscle that is part of a large group of muscles
125
Cramp
painful spasmodic contraction
126
Tic
spasmodic twitch made involuntarily by muscles that are normally under voluntary control
127
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
128
Somatic nervous system
Motor control of voluntary skeletal muscle
***Sensation from body wall, limbs, head, and special senses***
129
Enteric nervous system
Sensation and motor control (smooth muscle, glands) of **GI tract**
130
The somatic, ANS, and enteric nervous systems all have both a ______ and ______ subdivision.
sensory
motor
131
Nerve vs. Tract
nerve: a bundle of neuronal **axons** in the _PNS_
tract: a bundle of neuronal **axons** in the _CNS_
132
Ganglion vs. Nucleus
ganglion: a group of neuronal **cell bodies** in the _PNS_
nucleus: a group of neural **cell bodies** (unmyelinated) in the _CNS_
133
Plexus
extensive network of nerves found within the PNS
134
Tremor
rhythmic, involuntary, purposeless, contraction
produces a quivering/shaking movement
135
Fibrillation
spontaneous contraction of a single muscle fiber
*not visible under the skin*
can be recorded by electromyography
may signal destruction of motor neurons
136
Muscle strain
forceful stretching or tearing of muscle fibers
137
Myotonia
slow relaxation or decreased ability to relax muscle after voluntary contraction
may be accompanied by increased muscular excitability and contractility
138
Myomalacia
pathological softening of muscle tissue
139
In neuron, axoplasm and axolemma are synonymous with:
cytoplasm
cell membrane (_NOT the same as neurolemma)_
140
Nissl bodies
prominent clusters of _RER_
specialized form of typical organelle
141
Neuron picture
* axon: can approximate 3' long in humans!
142
In a neuron, impulses (APs) generally arise in the ______ \_\_\_\_\_\_.
Trigger zone: the junction of the hillock and initial segment
143
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**
144
Axon ______ may branch off main axon.
collaterals
145
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)
146
Axon terminals contain only some:
contain only some cytosol, mitochondria, cytoskeleton, SER and synaptic vesicles
147
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
148
_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)
149
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**
150
Neuroglia are NOT ______ cells.
excitable
\*neuroglia will fills the spaces formerly occupied by neurons in cases of injury or disease
151
Neuroglia of CNS
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
152
Neuroglia of PNS
Schwann cells (neurolemmocytes)
Satellite cells
153
Neurons do not undergo ______ but neuroglia do.
mitosis
154
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
155
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)_***
156
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
157
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**
158
Nodes of Ranvier
gaps between myelinating cells (no myelin)
only on nerve fibers supplied by potentially myelin producing cells
159
Myelination in the CNS:
no neurolemma
there are nodes of Ranvier
one oligodendrocyte can myelinate multiple times (several segments or several different axons)
160
White vs. Gray matter
White: myelin (myelinated tract fibers)
Gray: no myelin; gray color from Nissl bodies (region predominantly filled with cell bodies)
161
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
162
Resting membrane potential (neuron)
-70mV
membrane potential: opposite charges are separated in space; **their attractive force _is_ the potential**
163
Types of ion channels (picture)
164
The cell membrane is impermeable to nearly all ______ charged intracellular molecules
negatively
e.g.: proteins, amino acids, phosphates, chloride (slightly permeable to *extracellular* Cl-)
165
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
166
Threshold:
-55mV
voltage gated Na+ channels open
167
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**)
168
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
169
Continuous conduction:
step by step depolarization and repolarization of adjacent segments of the axon
170
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)
171
A, B, C fibers
A: large, myelinated (fastest)
B: medium, myelinated (fast)
C: small, unmyelinated (slow)
**\*the greater the diameter the faster the conduction**
172
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
173
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**
174
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**
175
Axo-
dendritic
somatic
axonic
176
Chemical synapse signal transmission (picture)
177
How are neurotransmitters removed?
Enzymatic degradation
Reuptake/uptake
Diffusion
178
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
179
EPSP
Excitatory post synaptic potential
potential that brings the membrane closer to threshold (depolarizing)
inside of the cell becomes less negative
180
IPSP
inhibitory post synaptic potential
potential that brings the membrane further from threshold (repolarizing)
inside of the cell becomes more negative
181
Summation
integration/evaluation of synaptic input
occurs at trigger zone
Spatial summation
Temporal summation
182
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)
183
Plasticity
nervous system's ability to change based on experience and need
neurons can sprout new dendrites, synthesize new proteins, change # of synapses
184
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
185
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
186
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)
187
Local anesthetics work by blocking:
block the opening of voltage gated Na+ channels= prevents transmission of pain signals
188
Rabies is caused by a virus that reaches the CNS via:
fast axonal transport
