VTPP 427: Exam 1

T/F Intracellular fluid does not change since it is super stable but the extracellular fluid has a dynamic property that can “change” the baseline of an action potential

True

What element is the cell membrane extremely permeable to and helps establish the resting membrane potential?

Potassium

What happens when you increase the extracellular potassium concentration?

The concentration gradient for potassium will decrease because there is less of a need for potassium the leave the cell. This causes the resting membrane potential inside the cell to become more positive

Where does the action potential occur in a neuron?

Axon

Where is the “input zone” of a neuron?

The dendrites

T/F Dendrites form action potentials just like the axon

False

How do dendrites receive signals if they cant propagate action potentials?

They have the receptors that bind to a ligand and is which they receive signals from. These ligands allow more sodium to rush in and allow the voltage gated channels in the axon hillock to open up and propagate an action potential.

What are resting membrane potentials dependent on?

Leakage channels

What are action potentials dependent on?

Voltage gated channels

What makes our resting membrane potential more “negative” compared to the outside/extracellular space?

We have large anionic proteins in the intracellular space that simply can't leave

T/F When potassium leaves the cell to repolarize, we lose the majority or all the potassium we have

False

T/F The more that leaves, the more negative that the inside of the cell becomes which helps pull potassium back in.

True (This establishes equilibrium, which means the net movement of potassium is 0)

What happens when people have seizures?

You have an area that is too close to the threshold, you need to change the resting membrane potential.  (Typically lower it by hyperpolarizing it)

What does it mean by making a cell more excitable?

Bringing a cell resting membrane potential closer to the threshold. (Raising the resting membrane potential)

What are some of the few organs that don’t innervate with the parasympathetic nervous system?

Adrenal cortex and kidneys

T/F Tear production is purely sympathetic

True

What happens in the lungs when the sympathetic nervous system controls it?

Bronchioles dilate and increases respiration rate

How does the parasympathetic nervous system control heart rate?

Decreases the heart rate

What part of the heart does the parasympathetic nervous system act on?

The Atria

How does the sympathetic nervous system increasing ones heart rate impact the body?

• Help increase muscle contraction

• The vessels in the skin and organs constrict (lower flow to these areas) and the muscle and heart dilated (Increases flow).

• Also stimulate lipolysis

• Increase sweat

What is the reason we believe the SNS increase salivary mucus?

We think of our minds as a snake, compared to when a snake is stressed, it will increase its venom

What impact does the SNS have on our endocrine glands?

It decreases insulin so that there is more glucose to be used and increase glucagon. This allows skeletal muscle and the brain, who don't depend on insulin as much to use it which you need in a fight or flight situation.

T/F The SNS affects orgasmic contractions

True

How does the SNS control the dilation of our blood vessels?

At rest, sympathetic neurons are continuously firing at a low level. That means they continuously release norepinephrine (NE) onto α₁ receptors on vascular smooth muscle. This give the vessels a constant mild constricting signal. (Sympathetic tone)

What does the PNS do to bladder contraction and gastric motility?

Increases both of them

Where is the Central nervous system control center?

The Hypothalamus

What does thyroid hormone do to the heart?

Increase the expression of beta 1 receptors on the heart

What does cortisol do to the arterioles?

Causes the expression of alpha 1 receptors on the arterioles, which stimulates constriction/increases blood pressure.

T/F People with low cortisol have low blood pressure due to the lack of alpha 1 receptors present on the arterioles

True

What type of hormone is cortisol and explain the signaling process?

Cortisol is a steroid hormone, so it can cross the cell membrane and bind to an intracellular alpha 1 receptor. he cortisol-receptor complex then enters the nucleus and binds to DNA, triggering gene transcription into mRNA, which is then translated into proteins.

What does estrogen do to the coronary arteries?

Stimulates the expression of beta 2 receptors. It helps relax the arteries of biological women and helps with m2 expression in certain vessels

What is tone?

often associated with dual innervation that is constantly undergoing from both the SNS and PNS

T/F We always have tone present in our body

False

Does the autonomic nervous system control our reparatory system?

No, its controlled by higher levels of thinking to control blood pH.

T/F Blood flow to our brain usually stays constant regardless of what systems innervate with it

True

What happens to our pupils when the SNS innervates with it?

They dilate so that we can see further

What happens to our pupils when the PNS innervates with it?

They shrink so that we can see closer to us

In the SNS, describe the preganglionic and post ganglionic fibers and what all do they secrete?

• Preganglionic: Originates in the thoracolumbar spinal cord, is very short, and releases ACh.

• Postganglionic: Terminates in varicosities, very long, and release mainly norepinephrine.

In the PNS, describe the preganglionic and post ganglionic fibers and what all do they secrete?

• Preganglionic: Originates in the Cranial/Sacral spinal crod, is very long, and releases ACh.

• Postganglionic: Terminates in organs, very short, and releases ACh

What receptors are excitatory?

One receptors

What receptors are inhibitory?

Two receptors

Where is beta 1 receptor only found?

On the atria of the heart

What branch of the nervous system is in charge of regulating blood pressure?

Sympathetic Nervous System

T/F Alpha receptors are only sympathetic receptors, and the most common one is alpha 1

True

What do nicotinic receptors bind?

Acetylcholine released from the pre-ganglionic fiber

What does muscarinic receptors bind?

Acetylcholine released from the post-ganglionic fiber

What binds norepinephrine released by the post ganglionic fiber of SNS?

Alpha and Beta 1 and 2

T/F The PNS and SNS utilize both nicotinic and muscarinic receptors because of the exception that sweat/thermoregulation of the SNS uses acetylcholine in the post ganglionic fibers

True

T/F PNS increases blood flow in the reproductive organs by dilation of vessels and secretion in genitalia.

True

T/F Vasculature is under PNS control except for reproduction.

False

Why do would someone want to use a PNS blocker in the case of asthma?

Allow mucus secretion to slow which allows the airway to open up.

T/F PNS doesn’t control digestion but gets you ready for it. Increase in digestive enzymes and insulin and glucagon.

True

What impact does alpha 2 have on the PNS?

It tells the periphery to not release to much norepinephrine. Some of the NE that gets released to bind to can α₁ can also bind to α₂ receptors located back on the presynaptic nerve terminal as well. Work similar to a negative feedback in the sense that it prevents the sympathetic response from getting too excessive.

What impact does alpha 2 have on the CNS?

Similar to the PNS but more effective. When activated the brain sends less sympathetic stimulation to the body. Thats why α₂ agonist are great for sedation and reduced sympathetic activity.

T/F α₂ receptors can exist in peripheral tissues, including the GI tract, but their direct effect on GI smooth muscle isn't the major story here.

True

T/F All receptors are functional in all tissues

False

What receptors help dilate the blood pressure in the arterioles?

Beta 2

What happens in a parasympathetic overload?

Occurs in the presence of toxins such as organ-phosphates and breakdown AChesterase. This causes ACh to never be broken down, leading to constant firing of the PNS. (SLUDD)

What does “SLUDD” stand for?

Salivation, Lacrimation, Urination, Defection, and Death

Where are peptide hormones receptors located?

Surface of the target cell

Where are steroid hormones receptors located?

Inside target cell

How are steroid hormones produced?

They are derived from cholesterol and taken to the mitochondria and converted into a pregnenolone. Then depending on the organ/tissue, the enzyme will then make it into the specific steroid hormone.

What is the difference between a neurotransmitter and a neurohormone?

Neurotransmitters cross a synapse and bind to the local target (they are in very close proximity). A neurohormone is when a neuron secretes a neurohormone and enters the blood stream and acts on a distant cell.

T/F Neurons are very rapid but don't last very long but the endocrine system takes a min to hours but lasts for a longer time.

True

T/F Cells actions are dependent on the ligand, and not really depends on the receptor

False

How do hydrophilic hormones send their signals?

Through ion-gated channels, receptor-enzyme, or GPCR

How does GPCR work?

Once activated, a trimeric G protein turns on. The alpha unit activate the effector protein (typically adenylyl cyclase) which then converts ATP to cAMP (Secondary messenger). cAMP phosphorylates protein kinase A which will then activate the protein of interest to cause a signal.

How does receptor tyrosine kinase work?

This holoenzyme receptor causes phosphorylation of the tyrosine which activates a kinase that phosphorylates a protein and causes a desired response. 

What are some of the big ligands for the receptor tyrosine kinase?

Insulin, IGF1

What are some of the big ligands for adenylyl cyclase?

Epinephrine, Glucagon, CRH, ADH, ESTROGEN

What is one of the few steroid hormones who uses a surface receptor (GPCR - Adenylyl cyclase) for signaling?

Estrogen

How does receptor phospholipase C (GPCR) work?

G protein activates the effector protein (Phospholipase C) which breaks down PIP₂ into IP₃ and DAG (Secondary Messengers).

What does IP₃ do in the Phospholipase C pathway?

Mobilizes our intracellular calcium levels (Releases Ca²⁺ from ER) which causes multiple signals

What does DAG do in the Phospholipase C pathway?

Activates Protein Kinase C which will phosphorylate protein, activating it and will cause multiple signals

What are some of the big ligands for the phospholipase C pathway?

TRH, GnRH, and oxytocin

T/F Secondary messengers allow for tremendous signal amplification

True

How do lipophilic (hydrophobic/steroid hormones) work?

They require a protein carrier in the blood stream and can freely diffuse through the plasma membrane, binds to a receptor and the complex then acts as a transcription factor.

What makes a steroid hormone bioavailable?

They are weakly bounded to their carrier protein or are free of protein binding

What other ways can the steroid/lipophilic hormones cause a signal?

These hormones can be metabolized, either excreted from the body or like thyroid in the liver, causing activation.

What does diurnal secretion mean?

A hormone or substance is released in a daily pattern, changing depending on the time of day. (Like melatonin and cortisol)

How do we turn off these hormonal signals?

• We can put the receptor/ligand complexes in an endosome.

• We can have down regulation and put it in a lysosome and degrade.

• When the ligand binds, it turns off a signal.

• There is a production of an inhibitory signal or with GPCR, has something that blocks the G protein from activating something.

T/F The posterior pituitary is connected to the hypothalamus through a neural tract and the anterior is connected through a blood portal.

True

T/F The posterior pituitary doesn’t secrete neurohormones

False

What does somatostatin do?

Inhibits the release of GH and TSH

What does dopamine do?

Inhibits the release of prolactin

What does hypophysiotropic mean?

A hormone that stimulates or acts on the hypophysis (aka pituitary).

What feedback loop does the body mainly rely on?

Negative feedback loop

How does ADH increase blood pressure?

causing the increased blood volume through water reabsorption in the kidneys or vasoconstriction.

What has a similar function as ADH but mobilizes electrolytes to increase blood pressure?

Aldosterone

T/F Oxytocin also help with lactation as well. Its not used for milk production but milk ejection.

True

What controls our circadian rhythm?

By the pineal gland and the suprachiasmatic nucleus.

What in the pineal gland senses light changes?

Melanopsin containing retina ganglion cells sense the light change. These stimulate the suprachiasmatic nucleus “Master clock” to synthesize clock proteins and stimulate pineal gland to release melatonin

What is secreted from the zona glomerulosa?

Mineralocorticoids/Aldosterone

What is secreted from the zona fasciculata?

glucocorticoids/cortisol

What is secreted from the zona reticularis?

sex steroids

What is secreted from the adrenal medulla and what are the relative percentages of secretion?

epinephrine(80%) and norepinephrine(20%)

T/F Steroid hormones are not usually stored within the cells and will just diffuse through the plasma membrane and into circulation.

True

What senses a decrease in blood volume/pressure and stimulates the production of renin?

juxtaglomerular cells in the kidneys

What does aldosterone do in terms of Na⁺ and K⁺ movement in the kidney?

makes you reabsorb sodium but pee/secrete potassium

What does it mean when someone has a “primary” deficiency?

The tissue that produces the hormone is guilty