Exam 1 Physiology

Classify each of the structures as containing primarily smooth, skeletal, or cardiac muscles.

Smooth Muscle --> vein, intenstine Skeletal Muscle --> forearm, calf Cardiac Muscle --> heart

What is the difference between a regulated variable and a controlled variable?

The body senses a regulated variable and maintains it within a limited range, whereas the body changes a controlled variable but cannot sense it.

How can a hormone increase activity in one tissue but decrease activity in another tissue?

The hormone effect is dictated by the receptor and intracellular signaling cascades.

4. When a QB throws a pass, he must bring his arm back before he brings it forward. This slightly stretches the triceps and allows for a more forceful throw. Explain the physiology behind the increase in force of muscle contraction:

The resting muscle length = 100% length of the muscle - so there's a certain distance that muscle can shorten to - which is defined by constraints like bone, etc. within muscle tissue there's the individual sarcomeres, and these sarcomeres are restricted by the length that the fibers can contract and release. To generate peak force of a muscle, it has to be stretched a little bit (120% of resting length) in order to have enough overlap between actin and myosin to have enough relative force. The missile ground where there is enough room to contract, as well as enough force generated creates the best recipe for a forceful throw.

Metabolism

The sum total of all the chemical reactions of a cell or organism

What is a hormone?

a chemical messenger released by the endocrine system that acts on certain cells

With regard to normal muscle physiology, what is complete tetanus?

a continuous, fused contraction of the muscle

What is the definition of a sarcomere?

a contractile unit of striated muscle consisting of myosin and actin filaments and bordered by Z discs

What is creatine phosphate?

a high-energy phosphate compound that is used to produce ATP in working muscle

anterior pituitary

adrenocorticotropic hormone (ACTH), prolactin, follicle stimulating hormone, luteinizing hormone

What is hyperplasia?

an increase in the number of normal cells within an organ or tissue

From what substance are steroid hormones synthesized?

cholesterol

What is atrophy?

decreased cell size

You suspect your patient, Ms. Yaseen, has myasthenia gravis (MG). MG is an autoimmune disease that destroys acetylcholine (ACh) receptors and is characterized by varying degrees of skeletal muscle weakness. Select all of the muscles that MG may affect.

diaphragm orbicularis oculi supraspinatus

Ms. Yaseen, your patient, has myasthenia gravis (MG), a chronic autoimmune disease that attacks and reduces the number of acetylcholine (ACh) receptors in the neuromuscular junction. Which step of muscle stimulation would MG most likely affect?

generation of an end plate potential In patients with MG however, autoantibodies bind to ACh receptors and reduce the number of available receptors.

synergistic hormone interaction

hormones work together to produce greater effect Ex. estrogen, progesterone in female reproductive (combined effect on a target cell that is greater than the sum of their individual effects).

structure that produces the hormones that are secreted by the posterior pituitary

hypothalamus!

2 Examples of hormones involved in generic functions:

insulin involved in glucose uptake (metabolism), and ADH is part of water homeostasis (kidneys)

mimetic

mimetic (specific drugs can activate adrenergic receptors) sympathomimetic

Skeletal muscles are almost never completely relaxed. Even when a skeletal muscle is not fully contracting or moving, the nervous system automatically stimulates different groups of motor units, which creates a small degree of contraction. What is the name of this mechanism?

muscle tone (the mechanism that maintains an optimal overlap of myosin and actin when a person is at rest).

oxidative fibers have higher levels of an oxygen‑storing protein called _______

myoglobin.

Antagonistic hormone interaction

one hormone causes opposite effect of another

posterior pituitary

oxytocin and antidiuretic hormone

cholinergic receptors

receptors for acetylcholine receptors bind to acetylcholine 2 classes: nicotinic and muscarinic

You think that your patient, Ms. Yaseen, has myasthenia gravis (MG), an autoimmune, neuromuscular disease that destroys acetylcholine (ACh) receptors. You order additional tests to confirm the diagnosis, including the injection of neostigmine, an acetylcholinesterase inhibitor, to test if muscle strength temporarily improves. You give Ms. Yaseen an intramuscular injection of neostigmine in her right deltoid. If Ms. Yaseen has MG, how will neostigmine affect her muscle weakness?

reduce ACh breakdown and decrease muscle weakness

Ms. Tomaganuk has mild hypothermia, and her low body temperature causes her to shiver uncontrollably. Shivering is a physiological response that reestablishes temperature homeostasis. This is one example of a negative feedback response pathway. Label the components of the shivering negative feedback response pathway: - Body temp below 98 - Nerve cells in skin - Temp regulatory center in brain - Muscles

- Body temp below 98 --> stimulus - Nerve cells in skin --> sensor - Temp regulatory center in brain --> control center - Muscles --> effector

A skeletal muscle has three layers of connective tissue sheaths that help to organize the muscle. Match each description to the appropriate tissue layer.

- Endomysium (endo = inner): the sheath that surrounds a muscle fiber - Epimysium: the sheath that surrounds the whole muscle - Perimysium: the sheath that surrounds a fascicle

adrenergic pathway

- SNS: acetylcholine released, found by nicotinic receptor, postganglionic neuron responds to acetylcholine, norepinephrine is released onto adrenergic receptor on target tissue - PNS: muscarinic acetylcholine receptors

Which of the actions are functions of skeletal muscles?

- helps stabilize joins - producing heat

adrenergic receptors

-respond to adrenaline -signaling molecules like epinephrine and norepinephrine -many subclasses -makes heart beat faster, sweating, pupils dilate (positive response) - turns off gut motility and acid secretion (negative response) - different subclasses mediate different types of adrenergic receptors (why different responses will occur in different tissues)

Match a functional description to each component of thin filaments found in cardiac and skeletal muscle: 1. Actin 2. Tropomyosin 3. Troponin

1. A structural protein that binds the thick filament during the cross-bridge cycle 2. A regulatory protein that blocks the thick filament binding sites 3. A regulatory protein that binds calcium, causing a conformational change

Place the events of excitation-contraction coupling in the sequence they occur:

1. An action potential is produced in the sarcolemma 2. The T tubules are depolarized 3. Calcium channels in the sarcoplasmic reticulum open 4. Calcium ions flow into sarcoplasm 5. Calcium ions bind to troponin 5. troponin changes shape 6. Tropomyosin moves 7. Active sites are exposed on the thin filament 8. The thin and thick filaments bind.\

In order to function properly and stay alive, cells must maintain a relatively constant internal environment (homeostasis). The plasma membrane is mostly made up of phospholipids and proteins, and helps the cell maintain homeostasis. Identify the true statements about how the plasma membrane helps cells maintain homeostasis:

1. The intracellular and extracellular environments can have different concentrations of solutes such as sodium ions (Na+)(Na+) and chloride ions (Cl−). 2. If there is an excess of carbon dioxide inside the cell, some of the carbon dioxide molecules will diffuse across the plasma membrane and leave the cell. 3. A cell can use endocytosis and exocytosis to move large molecules between the intracellular and extracellular environments.

Arrange the events that take place when a motor neuron's action potential triggers a muscle contraction in sequential order, from the top down.

1. The motor neuron's action potential arrives at the neuromuscular junction. 2. Acetylcholine arrives at the muscle fibers plasma membrane, causing membrane to depolarize. 3. action potential moves through the muscle fibers along transverse tubules 4. Sarcoplasmic reticulum becomes more permeable in response to the action potential, causing release of Calcium ions 5. The tropomyosin shifts in position as calcium ions bind to troponin, and actin binding sites are exposed. 6. Myosin cross-bridges attach to actin fibers 7. Sarcomeres within the muscle fibers contract.

Define these key terms as they relate to homeostasis: 1. Effector 2. Variable 3. Receptor

1. a biological feature that responds to changes in the internal environment 2. a biological factor that is subject to change 3. an element that senses changes in a biological system

The following terms are all properties of muscle tissues. Match the correct definition to each term: 1. Elasticity 2. Extensibility 3. Contractibility 4. Excitability

1. ability to regain shape after stretching or contracting 2. ability to lengthen and stretch 3. ability to shorten and generate force 4. ability to respond to a stimulus

Place the events following binding of ACh by muscle to the cross-bridge cycle.

1. acetylcholine binds to nicotinic acetylcholine (nAChR receptors open), allowing sodium influx 2. Graded depolarization reaches threshold triggering voltage-gated sodium ion channels to open 3. Actin potential is transmitted along the sarcolemma to the t-tubule 4. Depolarization is transmitted to the voltage gated calcium channels 5. Calcium influx triggers more calcium efflux from the sarcoplasmic reticulum 6. Troponin binds calcium 7. Cross-bridge between actin and myosin is formed

In general, 1. _______ (Slow, fast, or both) oxidative fibers have a rich capillary supply and contain many oxygen‑utilizing 2. _______ (mirochondria or lysosomes) in comparison to fast glycolytic fibers, which rely on anaerobic metabolism to make ATP.

1. both slow and fast 2. mitochonria

Match each description to the appropriate microscopic feature of skeletal muscles: 1. Sarcoplasm 2. Sarcolemma 3. Sarcoplasmic reticulum

1. cytoplasm of muscle fiber 2. plasma membrane of muscle fiber 3. smooth ER of muscle fiber

Classify each description as characterizing facilitated diffusion, primary active transport, secondary active transport, or both primary and secondary transport: 1. Facilitated Diffusion: 2. Primary Active Transport 3. Secondary Active Transport 4. Primary & Secondary

1. does not require energy input, includes the glucose carrier protein 2. directly uses ATP hydrolysis to pump substances across the membrane, includes the Na+/K+ ATPase pump 3. uses energy stored in electrochemical gradients, always moves more than one substance at once, includes the Na+/glucose transporter 4. requires ATP, movement of substances against their concentration/electrochemical gradients

how is endocrine system stimulated: 1. hormonal stimulation 2. 3.

1. in order for glands to secrete specific hormone, another hormone has to come in and tell this response to happen. There are multiple axis this can happen along, like the anterior pituitary pathway. An example is when the nervous system input is sent to glandular cells; SNS sends signals to adrenal medulla, triggering release of epinephrine as a part of fight or flight. - Increases hormone secretion - Pituitary System has anterior and posterior parts (posterior hormones are produced by neurons in the hypothalamus and are released by anterior part - ADH and Oxytocin) 2.

Identify the neuromuscular structures in the junction

1. motor neuron axon terminal 2. synaptic cleft 3. motor end plate

List the correct order of steps in a response pathway:

1. stimulus, 2. sensor, 3. control, 4. effector, 5. response SSCER (think soccer)

At any given time, there is an array of signaling molecules in a cell's environment. How does a cell know which signaling molecules to respond to? 1. A cell responds only to signaling molecules that are targeted to that specific cell. 2. A cell responds only to signaling molecules that can enter the cell. 3. A cell responds to a signaling molecule only if the cell has the appropriate receptor. 4. A cell responds only to signaling molecules from neighboring cells. 5. A cell responds only to paracrine signaling molecules

3.

Which examples relate the law of mass balance to body homeostasis: A. Low blood glucose levels stimulate secretion of glucagon, which releases glucose into the blood. B. Water lost through sweat and urination is replaced by drinking water. C. An increased body temperature stimulates vasodilation of capillaries in the skin and activation of sweat glands. D. High levels of thyroid hormone in the blood inhibit further secretion of thyroid hormone. E. Uterine contractions during labor stimulate the secretion of the hormone oxytocin, which stimulates more contractions.

A & B

Which statements describe intercalated discs? A. Intercalated discs contain desmosomes. B. Intercalated discs occur in smooth muscle. C. Intercalated discs prevent direct communication between cells. D. Intercalated discs allow synchronized contraction of cardiac muscle cells. E. Intercalated discs are found between cardiomyocytes.

A D and E

Define homeostasis and explain its importance to normal human functioning

A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level.

Muscle cells store only enough ATP to complete a few contractions. After using up the readily available ATP, muscle cells can form additional ATP from which of the choices? A. cellular respiration B. the Calvin cycle C. creatine phosphate D. hydrolysis E. glycolysis

A, C, E

Which major mutation types, if found in a coding region, would alter the structure of the resulting protein at multiple structural levels? A. nonsense mutation B. silent mutation C. frameshift mutation D. missense mutation

A, C, and D

Facilitated diffusion is a type of passive transport that allows solutes to move across the plasma membrane of a cell. Which statements describe facilitated diffusion?

A. Solutes move across the membrane down their concentration gradient through specialized membrane proteins. B. Small, charged molecules and ions move down their concentration gradient out of a cell through proteins in the plasma membrane.

Which statement accurately describes the mechanism of the length-tension relationship? A. The muscle generates the greatest amount of tension when it begins its contraction from resting length, because the number of crossbridges is high. B. The muscle generates the greatest amount of tension when it is stretched, because the thin filaments have the longest distance to travel. C. The muscle generates the greatest amount of tension when it is shortened, because the number of crossbridges is low. D. The muscle generates the greatest amount of tension when it begins its contraction from resting length, because the number of crossbridges is low.

A. The muscle generates the greatest amount of tension when it begins its contraction from resting length, because the number of crossbridges is high.

Which enzyme is responsible for degrading the neurotransmitter that remains in the synaptic cleft after a muscle contracts? A. acetylcholinesterase B. glutamate decarboxylase C. cysteine protease D. lactate dehydrogenase

A. acetylcholinesterase

3 Examples of Each: A. Positive Feedback: B. Negative Feedback

A. savings account balance increases with interest, Oxytocin release increases in response to labor contractions, additional platelets aggregate in response to platelets adhering at an injury site. B. cruise control maintains a vehicles speed, an increase in body temp causes sweating, production of insulin increases in response to high blood sugar.

What is the cellular importance of ATP?

ATP is the primary source of chemical energy.

3. Explain why muscle diseases that result from inadequate release of ACh can be treated with drugs that inhibit acetylcholinesterase:

Acetylcholinesterase is the enzyme that breaks down acetylcholine (into synaptic cleft between neurons). This is a normal part of the cleanup process after calcium is released in order to turn off the muscle cell after stimulus is no longer necessary, or the muscle no longer needs to contract. Using drugs that inhibit acetylcholinesterase (like SSRIs) allow for the acetylcholine to stay around for lumber and have more of a signaling impact. This is a common way of treating various disorders like depression (for serotonin), it's different with acetylcholine and muscle contractions, however the same strategy is used.

Anabolism

All of the chemical reactions leading to the construction of complex molecules from smaller building blocks

Catabolism

All of the chemical reactions that lead to the breakdown of complex molecules into smaller subunits

eccentric contraction

An eccentric contraction occurs when tension develops as a muscle is lengthening.

second messenger

An intracellular molecule that facilitates a signaling cascade. A molecule that is generated when a specific substance attaches to a receptor on the outside of a cell membrane, which produces a change in cellular function.

isotonic contraction

An isotonic contraction occurs when a muscle develops tension and the length of the muscle shortens.

Which is the correct definition of the law of mass balance?

Any gain of a substance in the body must be offset by an equal loss, and any loss must be offset by a gain for the amount of the substance to remain constant. - Explained: Mass balance is the existing body load plus intake (or metabolic production minus excretion/ metabolic removal). According to the law of mass balance, any water lost in the sweat or urine must be balanced by water ingestion

One portion of a homeostatic feedback mechanism carries out the response to homeostatic imbalance. What is the term for this portion? A. receptor B. effector C. control center D. efferent pathway E. afferent pathway

B. effector

Select the description of a neuromuscular junction: A. a site where communication takes place between two neurons B. a site where a motor neuron transmits a signal to a muscle fiber C. a site where muscle fibers meet to form a tendon D. a site a sensory neuron meets dermis of the skin

B. where a motor neuron transmits a signal to a muscle fiber

Which of the structures are found in triads? A. acetylcholine receptor B. actin C. terminal cisterna D. transverse tubule

C & D

Muscle contraction is caused by: A. the shortening of each actin filament. B. myosin and actin filaments pushing farther apart. C. myosin filaments pulling on actin filaments. D. actin heads pulling myosin filaments closer.

C. myosin filaments pulling on actin filaments.

Why would calcium deficiency limit muscle contractions?

Calcium binds to the troponin-tropomyosin complex, exposing actin's myosin‑binding sites.

Select the statement that best describes homeostasis: A. prevention of changes from happening within the human body B. spontaneous induction of changes to alter the internal state of the body C. internal mechanisms that decrease physiological variables D. maintenance of a dynamic state of equilibrium within the human body

D.

Select the statement that describes recruitment in muscle contraction: A. The contraction of muscle fibers in one muscle stimulates the contraction of antagonistic muscles in an opposing muscle group. B. An increasing number of motor neurons are connected to the muscle fiber as a muscle grows and becomes stronger. C. Neurotransmitters from the synaptic terminal of a motor neuron stimulate an action potential in the muscle fiber. D. More motor neurons and larger motor units are activated to stimulate a greater number of muscle fibers for a more powerful muscle contraction.

D. More motor neurons and larger motor units are activated to stimulate a greater number of muscle fibers for a more powerful muscle contraction.

Adrenergic Agonists

Drugs that stimulate and mimic the actions of the sympathetic nervous system. Also called sympathomimetics. - Epinephrine, dopamine, dobutamine, isoproterenol, terbutaline

Endocrine glands and exocrine glands differ in their site of release and whether they have ducts.

EXOcrine glands secrete to the body surface and cavities and have ducts!!

Explain how homeostasis influences living systems:

Homeostasis is necessary for organisms on a cellular ( to maintain things like blood sugar levels and oxygen levels), however, it is also necessary for our bodies so that we don't do things like overheat or die or thirst. Our body will do things to maintain homeostasis like shivering to avoid hypothermia when it's too cold.

5. Jack & Jill ran up the hill...... Jill's legs are primarily of fast glycolytic (white) type, while Jack's are of slow oxidative type (red). Assuming everything else is the same, which one would utilize the most oxygen during the run and why?

I would assume that Jack would use the most oxygen during the run because both slow and fast oxidative tissue use oxygen as a primary source of energy (aerobic), whereas glycolytic muscle will switch over to anaerobic metabolism to create ATP as a source of energy. This is why Slow oxidative is the fatigue resistant muscle and fast glycolytic muscle is the most fatiguable. Fast glycolytic tissue = good for sprinting, slow oxidative tissue = good for long distances like marathons, fast oxidative fiber = somewhere in the middle (closer to marathon over sprint).

Categorize the exercises according to whether they utilize isotonic or isometric contractions:

Isotonic contraction: pull up and deadlift Isometric: static lunge and V sit

Match the descriptions with the appropriate kind of skeletal muscle contraction: Isotonic Isometric Concentric Eccentric

Isotonic: peak muscle tension does not equal load, muscle length changes Isometric: peak muscle tension never exceeds load, muscle length remains constant Concentric: peak muscle tension exceeds load, muscle shortens Eccentric: peak muscle tension less than load, muscle lengthens

Place the muscle fiber types in order from most fatigable to least fatigable.

Most fatigible --> fast glycolytic fiber, fast oxidative fiber, slow oxidative fiber <-- last fatigable

muscle tension

Muscle tension is the force exerted by a contracting muscle on an object.

Which statement best describes the sliding filament model of contraction?

Myosin binding to actin through cross bridges causes thin filaments to slide past thick filaments.

Classify the key elements of replication, transcription, and translation according to the process to which they belong:

Replication: primers, DNA polymerase, Okazaki fragments Transcription: promotor, exons and introns, RNA polymerase Translation: ribosome, codons and anticodons, aminoacyl-tRNAs

What is excess postexercise oxygen consumption (EPOC, oxygen debt)?

the amount of oxygen needed to restore all body systems to a resting state

What does autorhythmicity (automaticity) mean?

the spontaneous, regular depolarization and contraction of cardiac muscle

2. Using the info from the previous question, tell where and how each of the following would affect EC coupling: 1. Blocking calcium channels on T-tubules: 2. Inhibiting the active transport for calcium into the SR: 3. Inhibiting myosin ATPase: 4. "Turning off" genes in skeletal muscle that code for tropomyosin:

1. Blocking calcium channels on T-tubules: blocking the calcium channels on T tubules would impede muscle contraction because we need that calcium signal to kick off the big calcium release inside the cell - if a little bit of calcium does not flow into that muscle cell, nothing else will follow and that muscle contraction will not work. (This short-circuits the process, look at step 5 of last question) 2. Inhibiting the active transport for calcium into the SR: We need to pump calcium into the SR because in order to stop the contraction process, we have to take the calcium out and put it back in the SR where it belongs because the presence of calcium is the key regulatory factor (inside of the cell) for muscle contraction, even without neuronal stimulation. 3. Inhibiting myosin ATPase: inhibiting the ATPase function of myosin, we are turning off the hydrolysis of ATP into ADP. This means for the cell that this release of energy is no longer occurring - which in turn, prevents myosin from binding to the actin. If this does not happen then thick filaments cannot be formed. Thus, there is nothing to anchor myosin so actin cannot be pulled during contraction and the sarcomere cannot shorten. 4. "Turning off" genes in skeletal muscle that code for tropomyosin: If tropomyosin is not theore, then there isn't anything there to prevent myosin from binding with actin. As long as ATP is present, and myosin can bind to ATP - there will be muscle contraction without stimulation (especially if tropomyosin is not there to stop the myosin from binding).

1. Ms. Tomaganuk's body temperature is lower than normal. Her skin is cold to the touch because blood flow has been diverted away from the skin, toward underlying structures. This physiological response to decreased skin surface temperature prevents further heat loss. 2. After getting caught in a snowstorm, Ms. Tomaganuk's body temperature has become abnormally low. The coldest parts of her body are small structures, such as her fingers and toes. In contrast, larger body structures, such as her thorax and abdomen, are less cold.

1. Deep 2. Distal

The concentration of sodium and chloride is greater in the extracellular fluid compartment outside of a cell, whereas the concentration of potassium is greater in the intracellular fluid compartment within a cell. By maintaining these concentration differences, the two fluid compartments are _________. In order for the fluid compartments to be _______, the concentration of each substance would need to be identical in both compartments. Fluid compartments at equilibrium and fluid compartments in a steady state ______, but only maintenance of a ________ requires continual energy inputs over time.

1. In a steady state 2. at equilibrium 3. are both stable over time 4. steady state

Define: 1. Simple Transport 2. Facilitated Diffusion 3. Active Transport 4. Bulk Transport

1. Movement of solutes out of the cell directly through the plasma membrane 2. Movement of solutes out of the cell down their concentration gradients using membrane proteins 3. Movement of solutes into the cell against their concentration gradients using membrane proteins 4. Movement of contents of transport vesicles out of the cell by exocytosis

Classify the descriptions as characterizing only simple diffusion, only facilitated diffusion, or both processes: 1. Simple Diffusion 2. Facilitated Diffusion 3. Both

1. Movement of substances directly through the lipid bilayer, applies to substances like steroid hormones, O2 and Co2 2. may involve carrier proteins, may transport through channel proteins, glucose and some amino acids 3. passive transport, movement of substances down concentration gradient

Match each definition to the appropriate muscle component:

1. Muscle Fiber: an individual muscle cell 2. Myofibril: an organelle that contains sarcomeres 3. Myofilament: may contain either actin or myosin

Classify each atypical condition of skeletal muscle by whether it directly affects the neuromuscular junction or the myofilament interactions.

1. Neuromuscular junction= electrical stimulation botulism poisoning curare poisoning 2. Myofilament interactions = addition of Ca+ , removal of myocyte Ca+, removal of muscle cell ATp

Classify each description as characterizing osmolarity, tonicity, or both osmolarity and tonicity:

1. Osmolarity: the product of moles per liter of solute and the number of particles resulting from ionization, relevant to biological and nonbiological processes 2. Both: depends on solute concentration 3. Tonicity: depends on solute permeability of the plasma membrane, determines how a solution affects cell volume

The relative abundance of myoglobin influneces the color of each type of fiber. Slow Oxadative = ? Fast Oxidative = ? Fast Glycolytic = ?

1. Red 2. Pink 3. White

Primary and Secondary Active Transport

small things without charge scan cross a membrane. molecules with charges cannot effectively cross membranes on their own, they need facilitated diffusion to carte a doorway for a molecule to flow down its gradient (voltage gated ion channels are an example of this type of diffusion). This is not active transport (where energy is expended somewhere). theres 2 kinds - an example of primary active transport is the sodium-potassium ATPase. things are moved against their concentration gradients in primary active transport (costs ATP). Secondary active transport is when we establish a concentration gradient for something which requires energy to do so, then we make use of this concentration gradient to maintain a low or high concentration inside of the cell. an example of this is a sodium-glucose symporter (as sodium flows in, the protein also moves some glucose into the cell against its concentration gradient, this action is powered by the sodium gradient that was established in the first place). Sodium glucose pump needs sodium concentration gradient to take up glucose (harnesses energy to do something else). Cells will have both types of active transport to do different things.

dual innervation

some organs get both PNS and SNS inputs - for heart rate for example, there is both a gas petal and a break. Not all organs have dual innervation, however the ones that do allow for more fine control. These organs sit in the middle (autonomic tone) in terms of their response. Airways for example sit in the middle, giving them flexibility in both directions depending on what types of inputs needed to be sent to this tissue. If the body goes into fight or flight, the airways will expand as input from the SNS is necessary to keep you on your toes. At the same time, the PNS will send signals to the airways once you have calmed down, constricting the airways back up once they no longer need to be dilated. autonomic tone is dependent on amount of input from PNS and SNS.

input stimulus

sometimes a neuron or cell will need 2 inputs rather than one to get neuron to send a signal (spatial summation). can also be one neuron that has to signal multiple times in order to get up to threshold. every neuron has up to hundreds of synapses. the further from point of stimulus, the more a action potential decays - in gated potentials (mechanical or chemical), signals are trying to fire in order to step up towards threshold to get channels to open. inhibitory (IPSPS) are driven by potassium and chloride. Chloride comes in and potassium wants to stay inside (theres enough of a concentration gradient for it to flow out of the cell though). Graded potentials can go up or down whereas (hyper or depolarizing depending on channel).

Prolactin

stimulates milk production

Follicle-stimulating hormone (FSH)

stimulates production of ova and sperm

thyrotropin

stimulates the release of hormones from the thyroid gland

Growth hormone

stimulates tissue building and increases body size

refractory period

the time following an action potential during which a new action potential cannot be initiated. resting potential of neuron is at -70 mV. More sodium outside cell than inside cell (double gradient for sodium to enter cell). Ion channels are closed for sodium so gradient doesn't matter - until the trigger is pulled and gates open. Must be an initial polarization to trigger membrane threshold of neuron, allowing gates to open for sodium (must move cell to -55mV for shape change of protein). This chemical/ligand gated channel binds to acetylcholine, and sodium can flow in through a GRADED POTENTIAL (magnitude of membrane potential change, different levels) as long as there is a protein bound to the ligand gated channel. Mechanically gated channels are involved in hearing, touch, etc (connected to ECM) - temporary opening of ion channels - if they are sodium channels, it leads to Na+ flowing in (inside of cell is more negative, electrical gradient and now a chemical gradient as well). If enough sodium flows in, the neuron reaches threshold and the voltage gated sodium channels open, action potential is fired. As soon as they are opened, the cell enters the absolute refractory period. Once the cell is "inactivated" in the refractory period (+30-40 mV), shape changes in channel so it is blocked (even though its technically still open). Once inactivated, it cant open again until the cell has fully done its reset. The cell will then depolarize once potassium leaves the cell (down slope in diagram of ref. period). Once cell gets below resting membrane potential, it can reset so channels close and the cell is capable of being stimulated again (end of absolute refractory period - where there isd absolute NO action potentials being fired). Now the cell is in relative refractory period (charge is dipping below resting membrane potential). capable of being stimulated but further from action potential than the start (around -80mV), so more stimulation is needed. Functional purpose of refractory periods: for nervous system to signal, frequency of stimuli must be organized or else information will get mixed up / blended together.

Thyroid Hormone (TH)

thyroid hormones are non-polar, can cross membrane without help, receptors are inside the cell, stimulate transcription and translation (like steroid hormones, however its made from amino acids not lipids). They cant be stored. Makes thyroid-globulin proteins, has lots of tyrosines and iodines, we can start to make thyroid hormones while its still a part of the thyroid-globulin protein (which have to be actively secreted). To make thyroid hormone (2 tyrosine's and 0-4 iodines, t3 and t4 thyroxin).