LS 7C Midterm 1 Learning Objectives
Week 1 In-Class Questions What kind(s) of cell-to-cell junctions would be most useful for anchoring these cells together to form a strong tissue? A. Gap junction B. Tight junction C. Desmosomes D. Any of the above E. None of the above
C. Desmosomes
Describe the cross-bridge cycle in a skeletal muscle
1. Myosin head binds ATP => binding of ATP allows myosin head to detach from actin and readies it for attachment to actin 2. Myosin head catalyzes hydrolysis of ATP to ADP and Pi => results in conformational . change in which myosin head is cocked back. Because ADP and Pi bound rather than released myosin head in high energy state => here is where cycle is paused, myosin head not attached to actin 3. Myosin head binds actin, forming cross-bridge 4. When myosin head binds actin, myosin head releases ADP and Pi => results in another conformational change in myosin head called power stroke => myosin head pivots forward and generates force, causing myosin and actin filaments to slide relative to each other => sarcomere shorten
Describe parts of a simple reflex circuit
1. Particular tendon is activated (physician strikes tendon with hammer) 2. Stretch receptor in extensor muscle responds by sending signal along sensory nerve 3. Sensory neuron synapses with motor neuron in spinal cord 4. Motor neuron sends excitatory signal to . same extensor muscle, which responds by contracting 5. An inhibitory interneuron inhibits contraction of opposing flexor muscle Need to inhibit other because muscles can only contract and not pull or push When one muscle is activated the other is inhibited => flexor stimulated, extensor inhibited when bringing your hand/knee towards body, revered if bring away from body Goes from Afferent fiber (sensor) to spine (interneuron) inhibits extensor/inhibitor efferent neuron and stimulates other extensor/inhibitor efferent neuron (motor neuron) => cannot be activated at same time because do different actions in same pathway tetanus => This toxin is a poison that blocks the nerve signals from your spinal cord to your muscles. This can lead to severe muscle spasms, muscle contraction of sustained force
Week 1 In-Class Questions Which genes are expressed in a quiescent stem cell? A. SR genes B. DET genes C. DIV genes D. ID genes E. DIFF (skin) genes
A. SR genes
Week 1 In-Class Questions A decrease in cell adhesion, by the introduction of an experimental substance to a tissue, compromises the strength of the tissue. Which cell junction would MOST likely be affected if a tissue is treated with this experimental substance? A. adherens junctions B. gap junctions C. hemidesmosomes D. tight junctions
A. adherens junctions
Explain the process by which two neurons communicate at a synapse ++
Action potential makes it to axon terminal → depolarization activates calcium channels → vesicles with neurotransmitters fuse with pre-synaptic membrane → release neurotransmitters in synaptic cleft → neurotransmitters bind to receptors in postsynaptic neuron dendrite which are ligand-gated → receptors allow Na+/Cl- ions to open changing membrane potential → new AP in postsynaptic cell After inactivation, neurotransmitters are re-absorbed into presynaptic terminal and stored in vesicles until next action potential arrives
Desmosomes
Anchoring junctions that prevent cells from being pulled apart
Identify critical cells involved in auditory and visual sensory transmission to the brain
Auditory: Hair cells: specialized mechanoreceptors that sense movement and vibration Hair cells that detect sound vibrations are found in the cochlea and those that are part of the vestibular system that sense gravity and motion are found in the semicircular canals Stereocilia: hair-like projections from surface of hair cell that move in response to vibration => their motion cause depolarization of the cell's membrane by opening or closing ion channels Despite their name, Stereocilia more similar to microvilli than to cilia bc cilia can move on their own but Stereocilia cannot hair cells do not fire action potentials but they release neurotransmitters which affect the firing rate of adjacent neurons when they're depolarized Visual: Opsin: light-sensitive protein that converts light energy into electrical signals in receptor cell => They are G protein-coupled receptors, meaning they activate G proteins which leads to a cellular response with Opsin, the cellular response is a change in membrane potential Cone cells: photoreceptor cells that contains opsins sensitive to different wavelengths of light => provide the sharpest vision, color, found in fovea Rod cells: sensitive to light but most sensitive to blue-green light (gray shades) => found in periphery Bipolar cells: receive input from rod and cone cells and releasing neurotransmitters (do NOT fire action potentials) Ganglion cells: located on front of retina and receive input from bipolar cells => If activated, ganglion cells transmit action potentials by the optic nerve to the visual cortex in the brain to begin processing images Rods, Cones, and Bipolar cells generate graded potentials while ganglia cells generate the action potentials
Week 1 In-Class Questions What happens to a signal after it binds the receptor? A. It stays bound until the receptor is destroyed B. It eventually dissociates from the receptor C. It is eventually destroyed by the receptor D. It dissociates from the receptor when a termination signal is received
B. It eventually dissociates from the receptor
Evaluate which region of the brain has been damaged in a patient based on a set of symptoms
Broca's Area - Struggling to produce language but can comprehend speech - frontal lobe Wernicke's - Can't comprehend speech but have no issue producing speech - temporal lobe
Week 1 In-Class Questions Why do the functions of many receptor kinases depend on the fluid nature of the plasma membrane? A. The activation of enzyme pathways requires a fluid membrane. B. Binding of ligand to the receptor requires a fluid membrane. C. The receptor monomers must move together and dimerize to be activated. D. Phosphorylation requires a fluid membrane.
C. The receptor monomers must move together
Compare and contrast the sympathetic and parasympathetic divisions of the autonomic nervous system ++
Can't happen at the same time because affect the same pathway Sympathetic - go hard, accelerated heart rate, dilates pupils, stimulates glucose release Parasympathetic - constricts pupils, slows heart, rest and digest Sympathetic: - arousal and increased activity - "fight or flight"... increases heart rate and breathing rate, inhibits digestion, stimulates glucose release - nerves leave CNS from middle region of spinal cord Parasympathetic: - generally opposite effect of sympathetic - "rest and digest" - increases digestion, slows heart - nerves leave CNS from brain via cranial nerves
Describe the different types of cell-cell junctions ++
Cell-cell junctions (inside the cell): ■ Cell junctions physically connect one cell to the next and anchor cells to the extracellular matrix ■ Adherens junctions and desmosomes provide strong attachments between cells, but they do not prevent materials from passing freely through the spaces between the cells like tight junctions do. ● Tight junctions: A junctional complex that establishes a seal between cells so that the only way a substance can travel from one side of a sheet of epithelial cells to the other is by moving through the cells by a cellular transport mechanism. In other words, tight junctions prevent transport of material in between the membranes of the cell. ● Adherens junctions: A beltlike junctional complex composed of cadherins that attaches a band of actin to the plasma membrane. => The cadherins in the adherens junction of one cell attach to the cadherins in the adherens junctions of adjacent cells. This arrangement establishes a physical connection among the actin cytoskeletons of all cells present in an epithelial layer of cells. ● Desmosome: A buttonlike point of adhesion that holds the plasma membranes of adjacent cells together. In other words, they allow cells to adhere to one another. ■ Cadherins are at work here, too, strengthening the connection between cells in a manner similar to adherens junctions. Cadherins in the desmosome of one cell bind to cadherins in the desmosomes of adjacent cells. The cytoplasmic domain of these cadherins connects to intermediate filaments in the cytoskeleton. This second type of physical connection among neighboring cells greatly enhances the structural integrity of epithelial cell layers. ● Gap junctions:A type of connection between the plasma membranes of adjacent animal cells that permits materials to pass directly from the cytoplasm of one cell to the cytoplasm of another. Gap junctions are a complex of integral membrane proteins called connexons arranged in a ring. The ring of connexin proteins connects to a similar ring of proteins in the membrane of an adjacent cell. Ions and signaling molecules pass through these junctions, allowing cells to communicate The extracellular matrix (outside the cell): ■ Hemidesmosomes: A type of desmosome in which integrins are the prominent cell adhesion molecules. The extracellular domains bind extracellular matrix proteins, and the cytoplasmic domains connect to intermediate filaments. These intermediate filaments connect to desmosomes in other parts of the plasma membrane. The result is a firmly anchored and reinforced layer of cells.
Several common signaling molecules are represented below. Could any of these cross the cell membrane by simple diffusion? Which would likely have cell-surface receptors? Estradiol Adrenaline Glucagon PDGF Cortisone Acetylcholine
Cell-surface receptors Acetylcholine Adrenaline PDGF Glucagon Intracellular receptors Estradiol Cortisone Characteristics of molecules that can pass through the phospholipid bilayer: 1. Uncharged 2. Hydrophobic 3. Small in size 4. Down concentration gradient
Describe the global organization of the human nervous system ++
Central nervous system-- brain, spinal cord Peripheral nervous system-- sensory and motor nerve PNS split into: Somatic (Voluntary component)-- sensing and responding to external stimuli => split into motor nerves (efferent toward PNS) and sensory (afferent toward CNS) Autonomic (Involuntary component)-- regulate internal bodily functions => sympathetic (flight or fight) and parasympathetic (rest and digest)
Discuss the role that hormones play in the maintenance of homeostasis ++
Changes in levels are detected and hormones are released/inhibited in response Sends signal to stop the disturbance accordingly
Explain when and why hormones are released ++
Chemical compounds secreted by cells or glands that act on other cells or glands in the body either locally or at distant sites (transported through the bloodstream). They are released in response to a signal promoting growth, homeostasis, reproduction, and regulation
Predict how a charged molecule will move across a semipermeable membrane in the presence of an electrochemical gradient
Chemical gradients come from concentration differences Electrical gradients come from charge separation Electrical gradient stronger than chemical gradient Charged molecule will move down its electrochemical gradient (ie. if positive will move to negative side)
Extracellular matrix proteins
Complex of proteins and carbohydrates that surrounds the cell in animals.
Identify the components of a homeostatic negative feedback system ++
Components of negative feedback: ■ the process in which a stimulus acts on a sensor that communicates with an effector, producing a response that opposes the initial stimulus. Negative feedback is used to maintain steady conditions, or homeostasis. ● Stimulus:produces a change in the variable ● Sensor: measures/detects change in the variable ● Control: analyzes the information from the receptor and determines the appropriate response to the change ● Effector: organs or glands that carry out the response from the control center ● Response:the action of the effector that will counteract the stimulus and bring the variable back to its normal value Stimulus to sensor (Change in the level of something) - sensor to effector (Part of body or cells that detect) - effector to response (Part of body that makes change) - response inhibits sensor - brings it back to the set point
Week 1 In-Class Questions Older individuals have fragile skin that causes bed sores. The outer layer of skin can detach and blister in response to friction. Increased susceptibility to blister formation is caused by the loss of which component in the skin? A. Skin signal pathway transducers B. Cell cytoskeleton proteins C. Cell adhesion molecules D. Extracellular matrix proteins
D. Extracellular matrix proteins
Week 1 In-Class Questions Which of the following junctions would you predict to be most important for the function of the bladder? A. adherens junctions B. gap junctions C. hemidesmosomes D. tight junctions
D. tight junctions
Relate the structural features of a neuron (i.e., dendrites, axons) to their functions. ++
Dendrite - receives stimulus from presynaptic neuron. Receives signals from other nerves, input end of the nerve cell cell body: Junction where signal pass from dendrite to axon hillock Axon Hillock - start of action potential. Point where signals are summed if sum is high enough an action potential gets fired Axon - action potential travels down axon. Transmits signals away from nerves cell body Myelin sheath - insulate neuron → saltatory propagation. As, result action potentials "jump" from node to node increasing speed of conduction. Nodes of Ranvier - exposed sites (lots of ion channels). Exposed axon membrane sites between myelin sheaths. Concentrated with voltage-gated Na+/K+ channels Axon terminal - release neurotransmitters
Discuss how EPSPs and IPSPs are received and integrated by a postsynaptic neuron
EPSPs (excitatory postsynaptic potential) - depolarization (Na+) IPSPs (inhibitory postsynaptic potential) - hyperpolarization (Cl-) EPSP (Excitatory Postsynaptic Potential) - positive change in membrane potential (depolarization + repolarization), Na+ ions diffuse into cell after neurotransmitters bind and activate Na+ channels, STIMULATES ACTION POTENTIAL IPSP (Inhibitory Postsynaptic Potential) - negative change in membrane potential (hyperpolarization), neurotransmitters bind and open Cl- and K+ channels, Cl- diffuses into the cell or K+ diffuses out INHIBITS ACTION POTENTIAL
Describe different vertebrate reproductive strategies
External => in wet environment, can keep it wet, allows for nutrients from water and waste in water Internal => inside the body, to keep it wet and not dry out, amniotes with placenta, birds use eggs oviparous and humans are vivaparous
Relate the major regions of the brain, including the hypothalamus, thalamus, and sensory cortex to their respective functions ++
Frontal Lobe- decision making and planning Parietal Lobe- body awareness, ability to do complex tasks (ex. dressing) Temporal Lobe- processing sound Occipital Lobe- processing visual information Primary Motor Cortex- complex, coordinated behaviors by controlling skeletal muscle movements Primary Sensory Cortex- integrates tactile information from specific body regions and relays this information to the motor cortex cerebellum: balance Brainstem: initiates and regulates motor functions such as walking, posture, breathing and swallowing. Connects brain to spine => controls the flow of messages between the brain and the rest of the body Hypothalamus- endocrine function, hormone production, autonomic function Thalamus- relay motor and sensory signals to the cerebral cortex
Identify critical components of the endocrine system involved in regulating the human reproductive system ++
GnRH (Gonadotropin-releasing hormone) - From hypothalamus Stimulates release of FSH and LH from anterior pituitary Released during the the late follicular phase (repressed otherwise) Estrogen From ovaries Regulates release of GnRH, LH, and FSH throughout reproductive cycle Helps egg mature Positive feedback right before ovulation Progesterone From ovaries Helps maintain uterine lining Testosterone From testes Regulates release of GnRH, LH, and FSH throughout reproductive cycle
Describe how hair cells function to transduce mechanical signals to the brain
Hair cells have stereocilia that project from the surface that move in response to vibrations and cause an opening or closing of ion channels => ability to balance and hear. While they do not fire action potentials themselves, the depolarization causes a release of neurotransmitters that alter the firing rate of adjacent neurons. Sense of motion => the vestibular system is made up of two statocyst chambers and three semicircular canals. Hair cells are located within the semicircular canals and provide a sense of gravity and angular motion because as the head rotates, the fluid in the canals causes the stereocilia to move and therefore activate sensory neurons. Ability to hear => hair cells affect our ability to hear by converting pressure waves into an electrical impulse that is sent to brain. Sound is received by outer ear => sent to eardrum => amplified by 3 middle ear bones (larger size of eardrum compared to oval window)=> vibrations of oval window cause fluid pressure waves in basilar membrane and cochlear duct => cochlear duct contains organ of corti with stereocilia supported by the basilar membrane but projected into tectorial membrane. Vibrations cause movement of basilar membrane which bends stereocilia because they are projected into unmoving tectorial membrane. When stereocilia bend against tectorial membrane it causes depolarization and release of neurotransmitters. When stereocilia bend in opposite direction, hair cells repolarize and do not release neurotransmitters
Provide examples of organisms that rely on different modes of reproduction
Human (viviparity), sharks (ovoviviparity), Frogs (external fertilization), komodo dragon (asexual reproduction)
Explain the relationship between the hypothalamus and pituitary ++
Hypothalamus in the brain sends message to pituitary gland via neurons and the pituitary gland secretes the appropriate hormone (LH, FSH) ■ The hypothalamus sends signals to the anterior pituitary gland through small blood vessels. Neurosecretory neurons within the hypothalamus secrete releasing factors into these blood vessels, which bind to cell receptors in the anterior pituitary, signaling the release of hormones into the bloodstream. ■ The hypothalamus sends signals to the posterior pituitary directly; neurosecretory cells whose cell bodies reside in the hypothalamus extend their axons to the posterior pituitary. In response to action potentials, these cells release hormones directly into the bloodstream that act on distant targets.
Evaluate the effect of modifying cell-cell junctions or ECM components on tissue structure and function
If you compromise the ECM then your skin or epithelial tissues will not have strength in presence of pressure/stress => bed sores If adherens or desmosome => no cell to cell adhesion If hemidemosome => then cell can't connect to extracellular matrix If tight junction => then there would be no boundary for the skin, intestine, stomach, bladder => and molecules can go right through, there would be no seal
Describe the structure and function of a neuromuscular junction
It's a synapse between a motor neuron and a muscle, where the neurotransmitter isacetylcholine => Its function is to cause muscle contraction when activated Consists of a motor neuron synapsing with muscle fiber. There are various channels that will open/close to let in certain ions. The results is the release of neurotransmitters (Ach) that depolarize muscle cell (opens Na+ channels) and allows SrR to release calcium, which binds to troponin and removes tropomyosin from actin so myosin can undergo cross-bridge cycle 1. Action potential reaches synaptic terminal → change in voltage 2. Voltage gated calcium channels open and calcium flows in 3. Calcium binds to vesicles with neurotransmitter acetylcholine, vesicles fuse with membrane → exocytose acetylcholine 4. Acetylcholine binds to the ligand-gated ion channels in muscle cell 5. Potassium flows out and sodium flows in → Na+ channels open => depolarization → action potential 6. Depolarization causes voltage-gated sodium channels to open 7. More sodium comes in 8. Action potential propagates down T-tubules → calcium released from sarcoplasmic reticulum 9. SR release Ca2+, which bind to troponin in thin filament (actin), which moves tropomyosin from the binding sites of myosin 10. Exposure of myosin-binding sites on actin allows cross-bridge as myosin (thick filament) can now attach to produce shortening of muscle (contraction) 11. After AP, Ca2+ moves back to SR and tropomyosin covers actin again, after contraction ends and muscle relaxes
Explain how cell-cell junctions and the extracellular matrix (ECM) contribute to cells' ability to form tissues and organs ++
Junctions allow structure and stability by adhere functions and desmosomes, allowing cells to form together by cadherins. ■ Tight junctions form shape as they separate cells from cells and create a barrier. ■ While gap junctions allow molecules and signals to pass, allowing the cell to function. Extracellular matrix fibrous proteins function as holding cells together, form/properties, filter material passing through tissues, helps orient cell movement, chemical signaling. ■ Mutation in function of the extracellular matrix causes fragile tissues. Cell adhesion molecules— attach cells to one another or to the extracellular matrix Cadherins— cells to other cells (must be same type of cadherin) Integrins— cells to extracellular matrix Transmembrane, link to microfilaments or intermediate filaments Tight junctions— establish a seal between cells so that only way a substance can travel from one to the other is through cell transport mechanisms Gap junctions— permit materials to pass directly from one cytoplasm to the other Extracellular matrix: Basal lamina— present beneath all epithelial tissue, provides foundation => provides strength
Define the role of kinases and phosphatases in cell signaling pathways ++
Kinases— enzyme that catalyzes the transfer of a phosphate group from ATP to a substrate (phosphorylation), which activates the protein Phosphotases— remove a phosphate group (dephosphorylation), and protein becomes inactive ○ Kinase: ■ an enzyme that catalyzes the transfer of a phosphate group from ATP to a substrate. To catalyze this reaction, it binds both ATP and the substrate. This process is called phosphorylation. ● When a protein is phosphorylated by a kinase, it becomes active and is switched on. The addition of a phosphate group to a protein can activate it by altering its shape or providing a new site for other proteins to bind. ○ Phosphatase: ■ removes a phosphate group, a process called dephosphorylation. ● When a protein is dephosphorylated by a phosphatase, it typically becomes inactive and is switched off.
Explain how motor proteins actively move material around the cell ++
Kinesin and dynein associate with microtubules Kinesin— transports towards plus end of microtubule. A motor protein, similar in structure to myosin, that transports cargo toward the plus end of microtubules. Dynein— away from plasma membrane, towards minus end. A motor protein that carries cargo away from the plasma membrane toward the minus ends of microtubules. Driven by conformational changes and ATP Microtubules are found in cilia and flagella Microfilaments associate with with motor proteins Actin microfilaments and myosin transport in vesicles. Moving actin filaments inside muscle cells cause muscle contraction.
Relate the structure of skeletal muscle to its function in generating a contractile force
Larger muscles with more fibers produce greater forces Muscle force is depending on state already in Whole muscles are made up of parallel bundles of individual muscle fibers. A muscle fiber is a muscle cell that uses ATP => Each muscle fiber in turn contain hundreds of long, rod like structures called myofibrils. Myofibrils contain parallel arrays of actin and myosin filaments that cause a muscle to contract (where sarcomere is found) => Sarcomeres which are relatively constant invertebrates(size) are arranged in a series along the length of the myofibril. It is the contractile functional unit of muscles. The region from one Z disc to the next issarcomere. Actin subunits: Think filament (double helix with troponin and tropomyosin), lie more on the outside of the sarcomere Myosin: Thick filament, lie in the center of the sarcomereThe thick and thin filaments slide with respect to one another, using ATP as a source of energy. As a result of the sliding, the Z discs are pulled closer together (shortening results from sliding of actin thin filaments relative to myosin thick filaments) => cause contraction The contraction of a whole muscle fiber results from the simultaneous contraction of all of its sarcomeres => When Ca++ is present, this cycling of cross bridges continues and the filaments continue to slide with respect to one another. When Ca++ goes back into the sarcoplasmic reticulum, the contraction stops Striated muscles are arranged into muscle bundles → muscle fibers (muscle cell) → myofibrils (rod-like structure that contains parallel arrays of myosin and actin filaments) Myofibrils have rows are actin and myosin that are broken up by z-discs in units called sarcomeres Sliding Filament Model Sarcomere length contracts when muscle contracts → more overlap of myosin and actin filaments
Compare and contrast ligand-gated and voltage-gated ion channels with respect to their role in signal transduction in a neuron ++
Ligand-gated ion channel - opens when ligand binds (at synapse w/ neurotransmitters). Helps with neuron to neuron communication with release of neurotransmitters as signal molecules to attach to receptors Voltage-gated ion channel - opens when voltage reached (Na+, K+ channels and calcium channels in axon terminal). Play key role when neurons fire action potentials.
Evaluate the consequences of altering a component of a hormone pathway
Make alternative then issue with feedback: thyroid => overproduction causes a goiter change set point => sensor affected don't respond to sensor => effector effected
Relate changes in environmental conditions to changes in physiological or behavioral responses to temperature regulation ++
Many animals regulate their body temperature through behavior, such as seeking sun or shade or huddling together for warmth. ■ Endotherms can alter metabolic heat production to maintain body temperature using both shivering and nonshivering thermogenesis. ■ Vasoconstriction — shrinking and expansion of blood vessels to the skin can alter an organism's exchange of heat with the environment. A countercurrent heat exchanger is an arrangement of blood vessels in which heat flows from warmer to cooler blood, usually reducing heat loss. Some animals use body insulation and evaporative mechanisms, such as sweating and panting, in body temperature regulation. We can reset set point (obesity, fever)
Explain membrane potential and how it arises in both neuronal and non-neuronal cells ++
Membrane potential - measurement of charge difference between the inside and the outside of a neuron (differences in ion concentration) In neurons, resting potential is -70mV (more positive on outside) More Na+ outside, and more K+ inside (K+ leaks out) Refers to negative voltage across membrane at rest, mainly due to K+ leak channels and the negatively charged proteins inside the cell membrane compared to positive outside membrane. Also, due to sodium potassium pump, that removes 3 Na+ for 2 K+, so makes it less positive inside.
tight junctions
Membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid
Define microtubule, microfilament, and intermediate filament. ++
Microtubule: A hollow, tubelike polymer of tubulin dimers that helps make up the cytoskeleton. Function: maintain cell shape and the cell's internal structure, part of cell division (chromosome segregation), movement (cilia and flagella), and vesicle transport Microfilament: A helical polymer of actin monomers, present in various locations in the cytoplasm, that helps make up the cytoskeleton. Function: maintain cell shape and the cell's internal structure, part of cell division (cytokinesis), movement (crawling), and vesicle transport Intermediate filament:A polymer of proteins, which vary according to cell type, that combine to form strong, cable-like filaments that provide animal cells with mechanical strength. Function: cell shape and support, strength and support to tissues under stress (skin and intestine)
Identify cellular, molecular, and protein components involved in muscle contraction and explain their role
Muscle cell - cell that contracts Motor cell - cell that relays signal to muscle cell to contract through the release of acetylcholine Actin filaments - (thin filaments) double helix that is encased by protein tropomyosin Myosin filaments - (thick filaments) myosin heads sticking out Calcium - stored in sarcoplasmic reticulum, binds to troponin → change in shape Troponin - bound to tropomyosin Tropomyosin - wound around actin, blocking myosin binding sites ATP - helps myosin head move and detach from actin Action Potential in muscle - allows influx of Na+ions depolarizing the cell and allowing opening of ca2+ channels Muscle fiber - elongated cells that use ATP generated through ATP
Explain how each component of a homeostatic negative feedback system contributes to maintaining physiological stability. ++
Need each level so that body can maintain stability, without one of the levels, homeostasis won't be achieved Stimulus:Change in the level of something Sensor (receptor): Part of body or cells that detect Effector: Part of body that makes change Response
Differentiate between negative feedback and positive feedback, providing examples of each. ++
Negative feedback: ■the process in which a stimulus acts on a sensor which communicates with an effector, producing a response that opposes the original stimulus; this process results in homeostasis ● Example: High blood glucose right after a meal acts a stimulus to the pancreas (sensor), which in turn, produces the hormone insulin, which allows muscle and liver cells (effector) to take up the glucose circulating in the bloodstream, thus resulting in a lower blood sugar level (response). Positive feedback: ■ the type of feedback in which a stimulus causes a response that leads to the enhancement of the original stimulus; this process reinforces itself until it is interrupted ● Example: Positive feedback occurs in mammals during birth. When uterine contractions occur, thehormone oxytocin (stimulus) is released from the pituitary gland (sensor?), which cause the uterine muscles (effector) to contract more forcefully. The uterine contractions, in turn, cause the pituitary gland to produce more oxytocin causing more contractions until the offspring is born. Negative feedback (glucose/insulin) Positive feedback (during menstrual cycle, right before ovulation, estrogen stimulates increase of GnRH → LH surge) ● The negative feedback loop is more commonly used and is pretty simple. When a hormone reaches the optimal level in the bloodstream, a signal is sent to the hypothalamus and pituitary gland. This signal stops the production of the hormone and the levels begin to decrease or increase. ● The opposite situation can also occur. If hormone levels are too low, the hypothalamus and pituitary gland can signal glands to produce more of the needed hormone. The positive feedback loop is used less frequently. In this case, the effect of the hormone becomes more intense as the levels increase.
Determine if certain proteins in a signaling pathway function as phosphatases, kinases, or neither
On handout If it adds a phosphate group and activates protein, then it is a kinase If it removes phosphate and deactivates the protein, then it is a phosphatase If it does neither, then it is neither Kinases activate other proteins by phosphorylating them (signal transduction) Phosphatases deactivate other proteins by de-phosphorylating them (termination)
Describe the processes of oogenesis and spermatogenesis
Oogenesis - happens when female is born Oocytes matures in ovary → follicles grow and estrogen stimulates maturation process → egg is released from follicle → follicle turns into corpus luteum in ovary (releases progesterone) → egg travels to uterus → if egg is not fertilized, corpus luteum degrades Spermatogenesis - happens continuously Sperm generated in testes (seminiferous tubules) → passes through epididymis (motility) → vas deferens → prostate (motility) → seminal vesicle (provides nutrition) → bulbourethral gland (lubrication) → urethra → penis
Predict how addition of drugs or the introduction of mutated proteins will alter membrane potential, excitability, and/or signal transmission
Opioids bind to ligand-gated channels on postsynaptic cell → increased ion movement → increased signal → cell destroys receptors to decrease signal → need heavier dose of opioid to increase signal (get the same feeling) +drugs affecting CNS causes decrease in postsynaptic cells and needs higher doses + drugs interrupting membrane potential/encouraging leaks makes neurons unable to fire or overfire
Define the different types of hormones ++
Peptide/Amine Hormones ■ Due to their hydrophilic nature, they are unable to cross the cell's hydrophobic plasma membrane. Therefore, they are only able to bind to cell surface receptors. When binding to cell surface receptors, they activate second messenger pathways through the cell, resulting in changes in the metabolic state or gene expression of the target cell. ● Peptide Hormones: type of hormone made from a chain of amino acids Example(s): Oxytocin and ADH ● Amine Hormones: type of hormone derived from a single aromatic amino acid Example(s): Epinephrine, Norepinephrine, and Dopamine are all derived from the amino acid phenylalanine Steroid Hormones: ■ A type of hormone derived from cholesterol ● Due to their hydrophobic nature, they are able to cross the cell's hydrophobic plasma membrane. Inside the cell they bind to nuclear/cytoplasmic receptors, causing them to act as transcription factors which change the gene expression of the target cell. Hydrophilic-- peptide and amine (amino acids) Bind to cell-surface receptors and stimulate signaling cascade Hydrophobic-- steroid (cholesterol) Bind to receptors in cytosol, affect DNA transcription, more profound and long lasting effects
Describe the mechanism of action for a G-protein coupled receptor pathway ++
Receptor is activated by ligand GDP is switched for GTP when G-protein binds to activated receptor Alpha subunit dissociates and binds to and activates adenylyl cyclase ATP is converted into cAMP cAMP activates PKA which phosphorylates and activates many target proteins
Describe the mechanism of action for a receptor tyrosine kinase pathway ++
Responses from receptor kinases tend to involve changes in gene expression, which allow cells to grow, divide, differentiate, or change shape LONG TERM CHANGES Each kinase activates the next and so one signal can cause a prolonged response A tyrosine kinase pathway: ■ Receptor kinases bind signaling molecules, dimerize, phosphorylate each other, and activate intracellular signal molecules. 1. Inactive receptor: a. The signal molecules bind to the extracellular portion of the receptor. 2. Dimerization: a. Causes a conformational change in the cytoplasmic domain which activates the tyrosine kinase catalytic activity. b. ATP is converted to ADP in this process. 3. Active receptor: a. The conversion of ATP to ADP allows each member of the receptor pair to attach phosphate groups to one another; in other words, phosphorylation occurs. 4. These phosphate groups provide binding sites for intracellular signaling proteins, which activate them.
Predict which branch, parasympathetic or sympathetic, will respond to different stimuli
Scared - Sympathetic Relaxed or Eating - Parasympathetic
Distinguish between second messengers and other components of signal transduction pathways
Second messengers are in the cytoplasm, they help to amplify the signal and they go on to activate other molecules in the cycle i.e Cyclic AMP
Explain how the brain receives, processes, and sends information
Sensory info received by cranial nerves and spinal cord nerves → pass through brainstem → thalamus → specialized region in cerebral cortex Regions Frontal Lobe - decision making + understanding Primary motor cortex - complex motor movements Primary somatosensory cortex - relays tactile info to motor cortex Parietal lobe - controls body awareness and the ability to perform complex tasks Occipital lobe - vision Visual cortex Temporal lobe - sound, language, speaking, etc Auditory cortex Brain stem - sends info to cerebral cortex Cerebellum - coordinates complex motor tasks with sensory and motor info
Discuss how a signal can lead to both short- and long-term responses ++
Signaling cell —> signaling molecule —> receptor protein —> responding Signal binds and receptor is activated (conformational change) Signal transduction— one molecule activates the next Response— enzyme activation, turn on genes, signal other cells, cause transcription of proteins Receptor Kinase activity because changes gene expression=> long-term G-Protein-coupled receptor and ion channel receptors=> short term Long Transported by the circulatory system example: Endocrine Signaling: Adrenaline, estrogen and testosterone Short Moves by diffusion Example: Paracrine— two cells close to one another: Small, water-soluble molecule (i.e. growth factor) Autocrine signaling-Signaling molecule released by a cell and binds to receptors on the same cell: When an embryo specializes cell types, this can reinforce this decision Cell-to-cell contact: signaling molecule is not actually released from the cell, transmembrane protein When the two cells are far apart, the signaling molecule is transported by the circulatory system. When they are close, the signaling molecule simply moves by diffusion. Many cells in multicellular organisms are physically attached to one another; in this case, the signaling molecule is not released from the signaling cell at all. Short Term Response: ● Paracrine signaling: Signaling molecules travel a short distance to the nearest neighboring cell to bind its receptor and deliver its message. ■ In paracrine signaling, the signal is usually a small, water-soluble molecule such as a growth factor. A growth factor is a group of small, soluble molecules that affect cell growth, cell division, and cause changes in gene expression. Growth factors help shape the structure of an adult's tissues, organs, and limbs. ● Autocrine signaling: Signaling between different parts of a cell; the signaling cell and the responding cell are one and the same. ■ Can be used by cancer cells to promote cell division. ● Cell-cell contact: A cell can communicate with another cell through direct contact, without diffusion or circulation of the signaling molecule. This form of signaling requires that the two communicating cells be in physical contact with each other. ■ A transmembrane protein on the surface of one cell acts as the signaling molecule, and a transmembrane protein on the surface of an adjacent cell acts as the receptor. The signaling molecule is not released from the cell, but instead remains associated with the plasma membrane of the signaling cell. Long-term response: ● Endocrine signaling: Signaling molecules travel through the bloodstream.
Determine whether a particular hormone will interact with a cytosolic or membrane-bound receptor
Steroid hormones bind to a cytoplasmic receptor. Thyroid hormones bind to a nuclear receptor (inside membrane) Epinephrine binds to beta-adrenergic receptors on the plasma membrane of cells.
Explain the process by which an action potential is generated and propagated ++
Summed or spatial EPSPs (graded potential) → depolarization in dendrites → depolarization at axon hillock → opening of Na+ voltage-gated channels (QUICKLY) and K+ voltage-gated channels (SLOWLY) → Na+ ions rush in (major depolarization), few K+ leave → Voltage reaches +40mV → Na+ channels shut, K+ channels remain open → K+ ions leave cell → cell becomes more negative (repolarization) → Hyperpolarization → refractory period (no A.P) → pumps return membrane to resting potential by pumping out Na+ and pumping on K+
Evaluate how multiple signals will be integrated by a postsynaptic neuron that has formed synapses with two or more pre-synaptic neurons.
Temporal Summation - multiple EPSPs arrive quickly at single synapse Spatial Summation - multiple ESPS arrive at different locations simultaneously Cancellation - EPSPs and IPSPs cancel each other out Postsynaptic membranes contain multiple receptors, and can bind many different neurotransmitters. Cell sums all the inputs -> if summed input breaches threshold potential, an action potential is fired at axon hillock Temporal Summation = summed over time, frequency of synaptic stimuli determines action potential Spatial Summation = summed over space, number of synaptic stimuli received from different regions of the postsynaptic cell's dendrites determines action potential
Predict how components of a homeostatic system will change when part of the system is perturbed. ++
Will get disrupted
Predict cell fate based on cell activation of signaling pathways
Worksheet there could be signals that only activate certain genes that limits what the cells can differentiate to
Evaluate how changing components of the cytoskeleton would change cell structure (shape) and/or function (i.e., motility)
The cytoskeleton: ■ In eukaryotes, an internal protein scaffold that helps cells maintain their shape and serves as a network of tracks for the movement of substances within cells. ■ There are three groups of movers, the motor proteins: kinesin, dynein and myosin, and three main groups of shapers, the protein filaments: microtubules, intermediate filaments and actin filaments. ■ The protein fibers of the cytoskeleton provide internal support for cells. All eukaryotic cells have at least two cytoskeletal elements, microtubules and microfilaments. Animal cells have a third element, intermediate filaments. All three of these cytoskeletal elements are long chains, or polymers, made up of protein subunits. In addition to providing structural support, microtubules and microfilaments enable the movement of substances within cells as well as changes in cell shape. Altered activity of motor proteins can lead to build-up or loss of cellular components
Relate endocrine function to homeostatic regulation ++
The endocrine system plays an important role in homeostasis because hormones regulate the activity of body cells. ■ The release of hormones into the blood is controlled by a stimulus. ● The hypothalamus' function in the endocrine system is to control and stimulate the pituitary gland. The hypothalamus and pituitary gland are connected via a system of blood vessels. Hormones produced in the hypothalamus travel through the vessels and stimulate the pituitary gland. The hypothalamus produces inhibiting or releasing hormones. ● Our thyroid gland is located in the neck and stimulated by TSH, which is appropriately called thyroid stimulating hormone. The thyroid is responsible for metabolism, regulating body temperature, the development of the nervous system, reproductive system and heart function. The thyroid secretes two hormones, T3 and T4, which are collectively called TH (thyroid hormone). ● The pancreas is also part of the endocrine system. Insulin and glucagon are secreted by the pancreas to regulate blood sugar levels. Among the cells used for digestion, are cells that produce hormones. Alpha (α) cells secrete glucagon, which elevates the level of glucose in the blood. Beta (β) cells secrete insulin, which decrease the level of glucose. ● In females, the important hormones are estrogen and progesterone. Both are produced in the ovaries. They regulate the menstrual cycle and initiate production of eggs. ● Interstitial cells in the testes produce testosterone, which is the important sex hormone in males. Testosterone is responsible for sperm production and developing the secondary sexual traits.
Predict how changes in release of pituitary sex hormones will alter oogenesis and spermatogenesis
There is a negative feedback => decrease testosterone leads to increases in FSH and LH Increase testosterone leads to decrease in FSH and LH decrease in progesterone or estrogen then increase Increase progesterone or estrogen then decrease => use this for contraceptives
Apply the concept of negative feedback to the process of thermoregulation. ++
Thermoregulation and negative feedback: ■ Negative feedback is the most common feedback loop in biological systems. The system acts to reverse the direction of change. This tends to keep things constant, allowing the maintenance of homeostatic balance. ● Example: When body temperature rises, receptors in the skin and the hypothalamus sense the temperature change. The temperature change (stimulus) triggers a command from the brain. This command, causes a response (the skin makes sweat and blood vessels near the skin surface dilate), which helps decrease body temperature. Body temp goes up → activates thermoregulation portion of brain → Blood vessels dilate (release heat) and sweat glands release fluid → temp goes down Body temp goes down → activates thermoregulation portion of brain → blood vessels constrict (contain heat), muscles contract repeatedly (shivering) → body temp goes up
Distinguish the potential for differentiation of totipotent, pluripotent, and multipotent stem cells ++
Totipotent— can give rise to a complete organism (most potential) Pluripotent— can become any of the three germ layers (ectoderm, mesoderm, endoderm). (Less potential) Multipotent— can form a limited number of specialized cells (least potential)
Describe the general structure of a neuron ++
Types of neurons: Sensory neuron - receives info from stimulus and send to interneurons Interneuron - received info from sensory neurons and transmits it to motor neurons Motor Neuron - receive info from interneuron, effects response in body
Predict which hormones have been released from the pituitary to elicit a specific tissue response
Usually hormones that go directly to another gland to produce an effect => master gland Look at the target cell and responser, should be opposite to the stimulus
Discuss the similarities and differences in hormonal control of male and female reproductive systems ++
Very similar (in terms of hormones other than testosterone vs estrogen) Male system is continuous and female system is cyclical
Predict the effect of altering part of a signal transduction pathway
When one part of the signal transduction pathway is altered, it affects everything else downstream
Interpret data related to different types of cell signaling pathways
cell signal (ligand) => receptor activation => signal transduction => response => termination Paracrine signaling: short distance (diffusion) Synaptic signaling: short distance (ligands are neurotransmitters) Autocrine signaling: cell signals to itself Endocrine: signals release through bloodstream cell-to-cell contact: stuck together, signal can be a transmembrane protein Hydrophobic signaling molecules can diffuse through the plasma membrane and bind to internal receptors. Hydrophilic molecules are unable to pass through the plasma membrane due to their polarity and must bind to an extracellular domain of a cell-surface receptor.
Evaluate why diffusion and surface area limit cell size and its implications for large, multicellular organisms
cells can't get too big or else the volume to surface area is decreased and there is less surface area to absorb/diffuse. Waste removal faster in small cell. Implications: lots of little cells for large, multicellular organism. As volume increases, surface area decreases Cells that are bigger need more nutrients, so as gets bigger can't hold much nutrients and the ability to discard waste is reduced
Provide examples of organisms that rely on different modes of reproduction
r -strategies - lots of babies, not much parental care K-strategies - few babies, lots of parental care Internal fertilization - eggs fertilized inside body Viviparity - Born alive (ex. humans) Ovoviviparity - born as eggs and hatch (ex. shark) External fertilization - eggs fertilized outside of body Frogs Aquatic Environment - More likely to have external reproduction Terrestrial Environment - More likely to have internal reproduction
Explain how a signal transduction pathway can be turned off
■ The length of time a signaling molecule remains bound to its receptor depends on how tightly the receptor holds on to it, a property called binding affinity. ■ G proteins can catalyze the hydrolysis of GTP to GDP and inorganic phosphate. This means that an active, GTP-bound α subunit in the "on" position automatically turns itself "off" by converting GTP to GDP. In fact, the α subunit converts GTP to GDP almost as soon as a molecule of GTP binds to it. Without an active receptor to generate more active G protein α subunits, transmission of the signal quickly comes to a halt. ■ Farther down the pathway, an enzyme converts the second messenger cAMP to AMP, which no longer activates protein kinase A. ■ Phosphatases remove the phosphate groups added by PKA, inactivating PKA's target proteins. Termination: Binding affinity (ligand is released from receptor) Phosphatases remove phosphate groups de-activating proteins G-protein converts GTP back to GDP Enzymes degrade cAMP