Exam 2 Flashcards
What does axon myelination consist of?
Myelin “coat”
What is the myelin sheath?
Intermittent lipid coverings down the axon
What type of cells is the myelin sheath formed by?
Non-neuron support (Glial) cells
- Schwann cells –> PNS
- Oligodendrocytes –> CNS
What are Nodes of Ranvier?
Bare axon surface
Where are Nodes of Ranvier?
Between myelin sheaths
~ 1 mm apart
What does axon myelination = ?
Speed, speed, speed
What does axon myelination = ?
Speed, speed, speed
What is saltatory conduction?
- Action potential “skips” over myelinated areas of axon membrane
- Increases action potential propagation speed
Synapse
Association between axon terminal and target cell
What are the 3 types of target cells?
Another neuron, muscle cell, secretory cell
Synaptic Cleft
Space between synaptic knob and target cell
What is the synaptic knob?
Bell-shaped ending of axon
What does the synaptic knob contain?
Synaptic vesicles that hold packaged neurotransmitters
What does the AP open?
Ca 2+ channels
What does the action potential opening the Ca 2+ channels do?
Causes exocytosis of neurotransmitters
What happens when the nuerotransmitters are released?
They cross the cleft, bind to receptors on target
Steps once action potential is released
- Action potential reaches terminal
- Voltage-gated Ca 2+ channels open
- Calcium enters axon terminal
- Nuerotransmitter is released and diffuses into the cleft
- Nuerotransmitter binds to postsynaptic receptors
- Nuerotransmitters are remobrf from synaptic cleft
Excitatory Post-Synaptic Potentials (EPSPs)
Nuerotransmitter-receptor Ligands open gated channels
- Mostly Na+ channels
- Each brings target closer to “threshold” (-55 mV)
Inhibitory Post-Synaptic Potentials (IPSPs)
Neurotransmitter-Receptor Ligans increase membrane permeability
- K+
- Cl-
Hyper polarizes membrane (Higher Resting Potential)
–> Further away from “threshold” (-55 mV)
Grand Post-Synapic Potential (GPSP)
The “sum” of concurrent EPSPs and IPSPs
Temporal Summation
- From one upstream neuron
- Rapid enough to “build up”
Spatial Summation
“Build up” from multiple upstream neurons
What do neuropeptides act on?
Act on the target cell
- near, but not within the synapse
What do neuropeptides do?
Alter (^ / v ) responsiveness to neurotransmitter
What is pre-synaptic inhibition / potentiation?
- Regulation of the pre-synaptic nueron
- By 3rd party neuron
- Influences amount of neurotransmitter released
What is the central nervous system made of?
Brain and spinal cord
What does the brain do?
- Regulation of body
- Higher thought/memory
- Lower “thought” (reactions, emotions, etc)
What does the spinal cord do?
- Passageway between the brain and body
- Coordination of some basic reflexes
- Source of motor neurons
- Destination of sensory nerves
What is the cerebrum?
- Outermost neural tissue
- Highest complexity
- Highest thought
What is the cerebrum composed of?
- Cerebral cortex
- Hippocampus
- Olfactory bulb
- Basal nuclei
What is gray matter made of?
- Cell bodies/dendrites
- Vasculature
What is white matter made of?
- Bundles of myelinated axon fibers
- “Tracts” for neural pathways
Right hemisphere
- Spatial relationships
- Music, art
- Creativity
Left Hemisphere
- Language
- Fine motor control
- Logic
Where is the occipital lobe? What does it do?
- Back of the cerebral cortex
- Visual processing cortex
Where is the temporal lobe? What does it do?
- Sides of the cerebral cortex
- Hearing
Where are the parietal lobes? What does it do?
- Top of the cerebral cortex
- Touch, pressure. heat/cold, pain, body position
Where is the frontal cortex?
in the front of the cerebral cortex
Primary motor cortex
Voluntary motor control
Supplementary motor cortex
Stores motor programs
- “memorized” specific movements
Premotor cortex
- Works in conjunction with posterior parietal cortex
- Integration of motor programs with incoming sensory information
Limbic association cortex
- Motivation
- Emotion
- Memory
Hippocampus
Coverts short-term memory to long term
Olfactory bulb
Smell
Basal nuclei
- Inhibits unnecessary muscle tone
- Helps maintain posture
Thalamus
- “Relay station”
- Coordinates sensory input from output
- Filters out “useless noise”
Hypothalamus
Regulation of homeostasis
- Body temp
- Thirst / urine output
- Food intake / appetite
Controls anterior pituitary hormone secretion
Coordinates autonomic NS
Emotional & behavioral patterns
Cerebellum
Orb shaped structure located in the back of the brain
Vistibulocerebellum
- adjacent to brain stem
- maintains balance
- controls eye movement
Spinocerebellum
- located at midline
- coordinates w/ cc motor cortex
- predicts body position
~ makes adjustment
Cerebrocerebellum
- majority of cerebellum
- “lower” voluntary action
- some “procedural” memories
What is the brainstem made of (3 components) andwhat level of function does it have?
Medulla, pons, midbrain
- lowest / least conmplex function
~ sleep/awake, alertness, basic touch/pressure
~ systems activity
Medulla
- swallowing/salvation
- vomiting (chemoreceptor trigger zone)
- respiration
- blood pressure
- heart rate
Pons
- Changes in respiratory rate, blood pressure
- Analgesic system, sleep
Midbrain
motivation
What is the spinal cord continuous with?
the brainstem
What is the spinal cord made of?
White & gray matter
Meninges
Cerebrospinal fluid
Lateral grat matter horns
cell bodies of autonomic (involuntary) efferent neurons
Ventral / anterior gray matter horns
Cell bodies of somatic (voluntary) efferent neurons
Dorsal/posterior gray matter horns
- cell bodies of interneurons
- receive signal from afferent / sensory neurons
Withdrawl (spinal reflex)
withdrawing body part from the pain source
Stretch (spinal reflex)
contracting SKM to counteract stretch
Crossed extensor (spinal reflex)
shifts load from injured limb to another
Peripheral nervous system
Nerves carrying info between CNS and body
Sensory neurons - afferent division
- detect specific conditions in body tissues
- alerts central nervous system
Motor neurons - efferent
- Begins in CNS
- Terminate on target tissues
Somatic division
voluntary
Autonomic division
involuntary
Order of spinal nerves (top –> bottom)
cervical > thoracic > lumbar > sacral > coccygeal
Receptor / dendrite
- receptor near dendrite tips
- receptor part of dendrite tips
- affect axon hillock potential
Axon
- connects to dendrites
- carries signal to CNS (via action potential)
Cell body
- axon “offshoot”
- Skeps depolarization during action potential
- groups located in same place
~ dorsal root ganglia
What do sensory neuron receptors respond to?
changes in SPECIFIC sources of energy
Photoreceptors
light
mechanoreceptors
stretch/bending
thermoreceptors
heat/cold
osmoreceptors
ECF molarity
Chemoreceptors
detect certain chemicals
- taste/smell , O2/CO2 in blood, nutrients in GI tract
Nociceptors
pain
What is intensity of sensation determined by?
action potential amount
Frequency code =
frequency of action potentials
Population code =
number of simultaneous action potentials
Receptor adaptation
Become less/non-responsive to stimuli
- often due to “over-stimulation”
Tonic receptors
- NO adaptation / gradual adaptation
- Example: muscle stretch receptors
Phasic receptors
Rapidly adapt
- “off response”
- cease firing when stimuli strength becomes constant
- example: odor, touch, temperature
Efferent division (PNS)
Autonomic nervous system
- involuntary
Sympathetic
- fight or flight
Parasympathetic
- rest and digest
- feed and breed
Somatic nervous system
- Voluntary
- Innervates skeletal muscle
Sympathetic fibers
Short preganglionic neurons
- originate in middle spinal cord
- neurotransmitter = acetylcholine (Ach)
Long postganglionic neurons
From ganglion to target
- allow coverage in greater area
- neurotransmitter = norepinephrine (NE)
Sympathetic tone
^ HR
constricts blood vessels to GI tract and skin
dilates blood vessels to heart & skeletal muscle
dilates lung bronchioles / stops mucus
slows activity of gall bladder, bladder, and GI tract
^ sweat & saliva
^ adrenaline/NE, v digestive hormones
Increased brain alertness
sympathetic immediate needs
Life or death
Fight or flight
Short term, high-input task
Parasympathetic tone
Slower HR
No effects on blood vessels
Constricts bronchioles/increases mucous production in lungs
Increases activity of GI tract and digestive organs
Gallbladder and bladder emptying
Stimulation/potentiation of many digestive enzymes and hormones
Readjusts pupil “near” vision
Longer-term parasympathetic needs
Food digestion/ nutrient level
Fertility/ reproduction
Recuperation
“Resetting” from major sympathetic event
Properties of muscle
Excitability
Contractility
Stretchability
Elasticity
Excitability
Change in function in response to stimulation
Contractility
Intentionally shorten length
Stretchability
can be lengthened w/out damage
Elasticity
Recoil from stretch to “resting” length
Skeletal muscle hyperplasia
Tissue growth via new cell formation
SKM hyperplasia is completed early
- before birth for most mammals
- early neonatal for some litter bearers
Skeletal muscle hypertrophy
Tissue growth via existing cell growth
Hypertrophy is postnatal mechanism for SKM growth
What do hyperplasia and hypertrophy both require?
Myoblasts
What are myoblasts?
Skeletal muscle stem cells
What 2 functions must myoblasts perform?
- Differentiate into specific cell type(s)
- Self-renew
Pre-natal hyperplasia
- myoblasts proliferate
2a. Most myoblasts differentiate into myocytes
2b. Some are “moth-balled” into satellite cells - Differentiated myocytes fuse to form myotubes
- Myotubes mature to form functional muscle fibers
Post-natal hypertrophy
- Quiescent satellite cells are activated into myoblasts
- Myoblasts proliferate
3a. Most myoblasts differentiate into myocytes - Differentiated myocytes fuse w/ existing fibers
Myofibril
Make up majority of the fiber
Functional unit of myofibers
Contain dark and light straining bands
Sarcomere
Repetitive contractile unit of myofibril
Z-line to z-line
Thick filaments
Myosin polymer chains
- run length of A-band
- H-zone = strictly thick filament
- Anchored by m-line
Thin filaments
Actin polymer chains
- make up I band (hang over into A-band a little bit)
- Anchored by stabilizing proteins at the z-line
What binds to thin filament?
myosin head
myosin neck purpose
hinge
Myosin tail
filament core
Titin
anchor protein
Actin
myosin attachment site
Tropomyosin
covers/exposes actin binding site
actinin
anchor protein
Sliding filament theory
Acting & myosin interdigitate at sarcomeres
- Myosin head (thick fil.) binds actin (thin fil.)
- Myosin undergoes conformational change
- Physically fulls think fil. toward center of thick ful.
- Power stroke
- Ca mediated
How do sarcomeres shorten?
Simultaneously (decreased overall fiber length)
Sliding filament theory steps
- Binding of myosin to actin
- Power stroke
- Rigor (myosin in low-energy form
- Unbinding of myosin and actin
- Cocking of the myosin head
What is muscle contraction facilitated by?
Calcium
Upstream neuron → action potential
How does calcium get into the muscle?
Travels down the t tubule
Where is the AP carried to?
The sarcoplasmic reticulum
→ major Ca dumping from blind pouches
Where is the AP carried to?
The sarcoplasmic reticulum
→ major Ca dumping from blind pouches
Skeletal muscle contraction mechanism
- Ca influx → outside cell & SR
- Ca binds to troponin
- Conformational change moves tropomyosin
- Uncovers actin’s myosin binding site.
- Myosin binds to actin
- ADP+Po keeps myosin head in “cocked” position
- Binding to actin: pi dissassociates
- Power stroke ensues (myosin neck hinges)
- Myosin and actin disengage
- Myosin binds another ATP, causing disengagement
- ATP → ADP+Pi recocked myosin head
- Ready to repeat
What keeps the thin filaments from sliding back once myosin disengages?
Staggered action
Relaxation
- Calcium re-sequestered → Ca-ATPase pump: pumps back into SR out of cell
- Troponin reverts to original conformation
- Myosin remains in cocked position (no binding site0
Glycolysis
2 ATP / glucose
Short term energy needs
No oxygen needed (anaerobic)
Oxidative phosphorylation
36 ATP per glucose
Long term-energy needs
Requires oxygen (aerobic)
- stores O2 in muscle cell
- Increases O2 extraction from blood
Energy sources
- ATP - very little “extra”
- Creatine phosphate
- “Holds” PO4 for ADP
- Phosphocreatine + ADP = ATP
- No oxygen needed
Fatigue
Acute Muscle fatigue
- ATP and/or CP depletion
Neuromuscular fatigue (chronic)
Lag in Ach production/ release
Type I fibers
red, slow oxidative
- slower, less powerful contraction
- Maintained longer
- High oxidative phosphorylation
Type IIa fibers
red, fast oxidative-glycolytic
- Medium-powered contraction
- Intermediate oxid. phos. vs. anaerobic glycolysis
Type IIx fibers
White, fast glycolytic
- Fast, powerful contraction
- Easy to fatigue
- High anaerobic glycolysis
- Easy to fatigue
What are cardiac muscle cells?
Cardiomyocytes
How do cardiac muscle cells compare to SKM?
Smaller & shorter than myocytes
Mono or binucliated
How to t tubules in cardiac muscle compare to SKM?
Shorter, broader
Intercalated discs
(cardiac muscle)
Specialized cellular junctions
Cardiac muscle - involuntary contraction
Autorhythmic pacemaker cells
Spread through gap junctions
Smooth muscle
single cells
- more thick filaments, myosin heads than SKM
- More myosin binding sites on actin
- No troponin
- Intermediate filaments → connect thin/thick networks, adds elasticity
Smooth muscle contraction steps
- Ca enters the cell
- Ca activates calmodulim
- Calmodulin activates myosin light chain kinase
- MyLHK phosphorylates MyLCs
- Phospho-MyLCs allow myosin to uncurl
- Uncurled myosin binds to actin
Endocrine system
Hormones → chemical messengers transported in circulation
Endocrine glands
- produce and secrete hormones
- Responsive to stimulus and/or inhibition
Hormone receptors
- Expressed by target cells only
- Allow tissue-specific responses to hormones
Hydrophilic
Amine hormones
- Amino derived
- Adrenaline, thyroid hormone
Peptide hormones
Short peptide chains
Oxytocin
Protein hormones
Large globular proteins
Insulin, growth hormone
Lipophilic
Steroid hormones
- cholesterol-derived
- Testosterone, estrogen, cortisol
Eicosanoid hormones
- Fatty acid-derived
- Prostaglandins, thromboxanes, lipoxins, leukotrienes
Hormone signaling
Circulate in blood
- Lipophilic hormones → transported by carrier proteins
- Hydrophilic hormones → dissolved in plasma (or carrier protein)
Cellular Signaling
Hydrophilic → membrane receptors / 2nd messenger systems
Lipophilic hormones → nuclear receptors/hormone response elements (HREs) on DNA , membrane receptors also
Hypothalamus
Brain center for homeostasis
- Makes hormones that regulate other hormones
- Makes hormones secreted by posterior pituitary
- oxytocin - uterine contracts, maternal behavior
- Vasopressin (ADH) - water balance
Hypothalamus
Brain center for homeostasis
- Makes hormones that regulate other hormones
- Makes hormones secreted by posterior pituitary
- oxytocin - uterine contracts, maternal behavior
- Vasopressin (ADH) - water balance
Anterior pituitary (epithelial)
“tropic hormones”
- Somatotrope - GH
- Thyrotrope - TSH
- Corticotrope - ACTH
- Gonadotrope - FSH / LH
- Lactotrope - prolactin
Target glands
Produce hormones with specific actions
- regulation of activities requiring DURATION rather than SPEED
- Associated with a single (or few) specific activities or functions
Examples of target glands
Thyroid/ parathyroid glands
Adrenal glands
Gonads (testes/ ovary)
Mammary glands
Liver, muscle, fat
Where is the thyroid located?
Around the trachea, below larynx
What is thyroid made of?
Follicles - clusters of secretory epith. cells
What does the thyroid use?
accounts for 99% of iodine usage
What is the thyroid stimulated by?
TSH from ant. pit.
What is thyroid product?
T3 and T4 (thyroxine)
What does the thyroid control?
Biol. effect: basal metabolism, body heat
Where is the adrenal gland?
Marble sized glands (2) sitting atop of each kidney
Adrenal gland medulla
Modified nerve endings
- secretes norepinephrine & epinephrin (adrenaline) into blood
- Acute stress responses, fight or flight
What is the adrenal cortex stimulated by?
ACTH from anterior pituitary
What are the adrenal cortex products?
- Cortisol
- Aldosterone
Adrenal gland biol. effect
- changes metabolism in response to stress “anti-stress / anti-inflammation”
- regulates mineral balance
What are the 2 types of gonads?
Ovaries in female, testes in males
What do gonads produce?
Haploid germ cells for reproduction
What are gonads stimulated by?
Gonadotropins from ant. pit.
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
Gonads products
Testosterone, estrogen, progesterone
Gonads biol. effect
Spermatogenesis, folliculogenesis, uterine quiescence, secondary sex (gender) characteristics
Liver, muscle, fat
Not traditional endocrine glands, but secrete hormones
What are muscle, liver, fat stimulated by?
Growth hormone
Other growth promoters/ inhibitors
Liver product
Insulin-like growth factors (IGFs)
Muscle product
IGFs, myostatin, etc
Fat product
leptin
Liver, muscle, fat biol. effect
IGFs promote tissue growth, cell proliferation
Myostatin inhibits growth
Leptin inhibits hunger
Pineal gland
Melatonin → regulates circadian rhythm
Thyroid
Calcitonin → stimulates production of bone
Parathyroid
Parathyroid hormone
→ stimulates breakdown of bone when blood Ca is low
→ stimulates activation of vitamin D by kidney
Liver
Angiotensin
→ stimulates vasoconstriction
→ stimulates release of aldosterone from adrenal cortex
Duodenum
Secretin & cholecystokinin
Stimulates
- biocarb & bile from liver
- Digestive enzymes from pancreas
- Gastric emptying
Stomach
Ghrelin, neuropeptide Y (NPY)
→ stimulate hunger
Kidney
Renin → activates angiotensin I
Erythropoietin → stimulates the production of RBCs
Somatostatin → Inhibits release of insulin, digestive enzymes from pancreas
Pancreas
Insulin → uptake & metabolism of glucose, especially by muscle + uptake & storage of FFA by fat cells
Glucagon → inhibition of glucose uptake + stimulates glucogenesis by liver
Where are non-coding RNA’s produced
via transcritption
What is special about non-coding RNAs
Don’t code for proteins … but affect those that do
What do non-coding RNAs regulate?
mRNA lifespan and mRNA translation rates
RNA slicing steps
- Base sequence creates double strand with hairpin loop
- Enzymatic processing
- RISC binds mRNA w/ compl. sequence
- Disables target mRNA
- Destroys it via cleavage
- Prevents ribosomal attachment
How much of mRNA’s are regulated by microRNA’s?
~ 60%
What is major structure in testes?
Seminiferous tubules
What happens in the testes?
- Site of spermatogenesis
What are Sertoli cells?
Tight-junctioned cells
- harbor developing sperm
Testes interstitial tissue
- Surround tubules
- Contain Leydig cells → produce testosterone
Epididymis
Common collection area for tubules
Spermatocytogenesis
Mitotic cellular reproduction
- multiple rounds
- Few spermatogonia become many
- Stop after G2 (2 x 2n)
Meiosis
One (2 x 2n) → Four (1 x 1n) spermatocytes
Meiosis 1
Crossing over occurs btwn chromosome pairs
1 cell w/ 2 pairs → 2 cells w/ 1 chromosome
4 immature spermatids
Spermiogenesis
Morphological transformation (differentiation)
Immature spermatid → mature spermatozoa
Ovary Medulla
Inner
Dense connective tissue
→ blood supply, nerves, lymphatic
Ovary cortex
Outer
Follicle (cell aggregate)
- 1 oocyte (femal gamete)
Granulosa cells
Produce estrogen
Interact w/ oocyte
Theca cells
Support granulosa
Stroma
Soft connective tissue
Supports follicles
Follicular phase
Primordial > primary > secondary > early antral > large antral
Ovulation
release of a mature egg from the female ovary
Luteal phase
luteinizing hormone and follicle-stimulating hormone levels decrease. The ruptured follicle closes after releasing the egg and forms a corpus luteum, which produces progesterone. During most of this phase, the estrogen level is high.
Oogenesis steps
Meiosis 1
Meiosis 2
Meiosis I
Begins prenatally
- crossing over
Arrested before splitting
Resumes after puberty
- 2 x 2n nucleus → 2 x 1n nucleus + 2 x 1n polar body
Meiosis 2
Just after ovulation
- 2 x 1n nucleus → 1 x 1n nucleus + 1 x 1n polar body