Exam 3 review questions

What are glutamate receptors?

(an amino acid) that is the most abundant excitatory
neurotransmitter in the vertebrate brain.

What are NMDA receptors?

They are a type of ionotropic glutamate receptor that conduct both Na+ and Ca2+ into neurons.

What are AMPA receptors?

They are a different type of ionotropic glutamate receptor that conduct only Na+ but NOT Ca2+ into neurons.

What event removes the magnesium block of NMDA receptors?

Depolarization of the postsynaptic membrane.

Why is it important that NMDA receptors become unblocked?

Allows Ca+ to enter the postsynaptic cell.

Which retrograde messenger is involved in Long-Term Potentiation?

Nitric Oxide (NO)

The plasma membrane of a skeletal muscle fiber is known as the _____________________.

sarcolemma

Why is the mammalian neuromuscular junction sometimes called an End Plate?

Because of its platter-like shape in mammals (including humans).

Spinal nerves are said to be 'mixed'. What does this mean?

This means that they contain both sensory and motor axons

A single spinal motor neuron, and all of the skeletal muscle fibers that it innervates, is known as a _________.

motor unit

Why do all of the skeletal muscle fibers within the same motor unit all contract at the same time?

Because they are all members of the same motor unit

What are myofibrils?

They are long contractile fibers that contain parallel arrays of actin and myosin filaments

Why does the diameter of myofibrils need to be small?

So calcium can diffuse quickly.

What binding sites are located on the myosin II protein?

enzymatic ATP-binding & hydrolysis site AND actin-binding site

What is a thick filament?

Myosin

How is a thick filament related to myosin II dimers?

thick filaments are composed of myosin II dimers (two protein molecules that function together)

The smallest functional unit (defined by a Z-disc on both ends) of contraction is known as a _________________.

sarcomere

What happens to the distance between Z-disks during contraction?

They become shorter.

Why must intracellular calcium concentration (i.e., [Ca2+]) increase before myosin heads can bind to actin?

Allows for this cycle to start:
1) binding to actin filaments
2) undergoing a power stroke and then
3) unbinding from actin filaments.

During cross-bridge cycling, which specific event triggers the power stroke?

myosin binds and then rotates its head

During cross-bridge cycling, which specific event allows the myosin head to unbind from actin?

ATP binding causes myosin to release actin, allowing actin and myosin to detach from each other

What role does Troponin T play in muscle contraction?

pulls Tropomyosin away from the myosin-binding sites on the actin filament

What role does Troponin C play in muscle contraction?

Ca2+ ions bind to it, which is transmitted to Troponin T

What role does Troponin I play in muscle contraction?

binds to actin.

What is Tropomyosin?

A protein that covers up (i.e., occludes) the sites on actin where myosin heads can bind.

Where is it located (and what is it doing) in non-contracting (i.e., relaxed) muscle?

Covers the active heads of actin.

In skeletal muscle fibers, most of the calcium that triggers contraction is released from the _________________________.

sarcoplasmic reticulum

What exactly is a T-tubule?

They are a bilayer.

What is the function of a T-tubule?

Action potentials travel down them into the fiber's center to reach the triads.

The process by which an action potential within the ___________________ induces the SR to release calcium ions into the myoplasm is known as _________________ - ________________ coupling.

T tubule bilayer (sarcolemma), excitation-contraction coupling

What is Ryanodine Receptor 1 (RyR1)?

They are giant, tetrameric Ca2+ channels embedded within the SR bilayer.

Where is RyR1 located?

present in skeletal muscle within the SR bilayer.

What does RyR1 do?

they bind with high affinity to ryanodine, a poisonous chemical found in the South American plant Ryania speciosa

How is RyR1 gated?

mechanically gated

What is CaV1.1?

is an L-type, voltage-gated Ca2+ channel (L-type refers to long-
lasting openings).

Where is CaV1.1 located?

skeletal muscle fibers

What does CaV1.1 do?

serves as the voltage-sensor for E-C coupling in skeletal muscle
fibers.

What is SERCA?

Sarcoplasmic-Endoplasmic Reticulum Ca2+ ATPases.

What does SERCA do?

constantly pumping Ca2+ back into the SR lumen

What is endocrinology?

the study of this system and the diagnosis and treatment of its disorders. It is the study of hormones.

Signaling by the endocrine system tends to be (faster or slower) and (shorter-lasting or longer-lasting) than signaling by the nervous system.

slower, longer lasting

Why do exocrine glands have ducts?

they carry secretion to an epithelial surface or the mucosa of the digestive tract: “external secretions”

Why don’t endocrine glands have ducts?

Secretions of endocrine cells move directly into the interstitial fluid (ISF), which is directly outside of most cells.

How many different types of endocrine cells are present with pancreatic Islets of Langerhans?

five

Which type of endocrine cell within the pancreatic Islets secretes insulin?

beta cells

Which type of endocrine cell within the pancreatic Islets secretes glucagon?

alpha cells

Speaking generally, what is the time-course for a cell's response to catecholamines such as epinephrine
(aka adrenaline)?

effects are produced within seconds-to-minutes

Speaking generally, what is the time-course for a cell's response to thyroid hormones?

days-to-weeks

In order for a cell to respond to a particular hormone, that cell must possess what?

specific receptor proteins

What is the difference between a hormone and a neurohormone?

Neurohormones are hormones secreted by a neuron onto a fenestrated capillary.

What is a neurohemal organ?

The axon terminals of hypothalamic neurosecretory neurons contact fenestrated capillaries within the Infundibulum of the Pituitary Gland to form one.

Precisely where on a cell are the receptor proteins for a water-soluble hormone located?

they are exposed (on the cell’s surface) to the interstitial fluid (ISF).

Why is the insulin receptor protein known as a "receptor tyrosine kinase"?

Because it binds insulin and is then activated by dimerization,
and the intracellular portion of the dimerized receptor protein itself
functions as a kinase enzyme.

Which portion of the insulin receptor functions as a tyrosine kinase enzymatic domain?

the intracellular portion

The receptor proteins for lipid-soluble (i.e., hydrophobic or lipophilic) hormones are typically located (where within the cell)?

within the cytoplasm and/or nucleus

In order to be carried throughout the body in the blood plasma, lipid-soluble hormones such as thyroid
hormones are typically bound to water-soluble ______________ ______________ that render them soluble in the ISF and the blood plasma.

carrier proteins

Name some endocrine tissues or organs that have other, non-endocrine function(s).

• Heart : secretes the hormone Atrial Natriuretic Peptide (ANP) & it also pumps blood.
• Testes : secrete testosterone & they also produce sperm.
• Adipose tissue : secretes numerous hormones (adipokines) and it also stores lipids.
• Ovaries : secrete estrogen & produce eggs.

What chemical type of hormone are estrogen, testosterone & aldosterone?

Steroids

Which molecule is used to synthesize testosterone?

cholesterol molecule

Taking exogenous testosterone may result in 'pharmacological concentrations' of testosterone that are
much higher than the normal 'physiological concentrations'. The excess testosterone may be converted
into the steroid hormone _______________ by an enzyme known as ___________________.

Estrogen, Aromatase

What is the Sella Turcica?

a saddle shaped depression of the sphenoid bone in which the pituitary gland occupies

Where is the Sella Turcica located?

sphenoid bone

Which aspects of homeostasis are regulated by Hypothalamic neurons?

temperature control, water balance, hunger, satiety, circadian rhythms
and reproduction.

The Posterior Pituitary gland is an extension of the ___________________.

the hypothalamus

The Anterior Pituitary is also known as the _______________.

Adenohypophysis

The stalk that connects the pituitary to the brain is named the _____________________________.

infundibulum

The _____________________ develops as a superiorly directed outgrowth of the roof of the mouth.

Anterior Pituitary gland

A _____________________ organ within the Posterior pituitary gland allows its two hormones to enter the blood plasma.

Neurohemal

The hormone ____________________ triggers maternal uterine contractions during childbirth.

Oxytocin

The hormone ____________________ may affect some male paternal behaviors.

Oxytocin

Name the eight hormones secreted by endocrine cells of the Anterior Pituitary.

FLAT PiG ME

Follicle-Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
Adrenocorticotropic Hormone (ACTH)
Thyroid-Stimulating Hormone (TSH)
Prolactin (Pro)
ignore the letter “I” – it is just a place holder
Growth Hormone (GH)
Melanocyte-Stimulating Hormone (MSH) – from Pro-opiomelanocort.
Endorphin (from Pro-opiomelanocortin, a pro-hormone)

A system of vessels in which blood, after passing through one capillary bed, is conveyed by a small vein (i.e., venule) to a second capillary network is known as a ________________ system.

portal

ACTH, MSH and endorphin are smaller peptides obtained by cutting a _________ into smaller pieces.

pro-hormone

What are hypophysiotropic hormones?

They either stimulate (releasing hormones) or inhibit the secretion of
hormones from the Anterior Pituitary endocrine cells.

Where do hypophysiotropic hormones come from?

(i.e., “pituitary-regulating”) are secreted by neurosecretory neurons within the Hypothalamus.

What are two advantages that arise from the Portal Vessel system that carries Hypophysiotropic hormones from the Median Eminence of the Hypothalamus to the Anterior Pituitary gland?

1) No dilution of hormone.
2) No enzymatic destruction of hormone by liver or lungs.

Is the secretion of Oxytocin during childbirth regulated by a positive or negative feedback loop? Explain how this loop works.

POSITIVE
• The hormone Oxytocin triggers uterine contractions during childbirth.
• The contractions cause the release of more Oxytocin from the Posterior Pituitary Gland.
• The extra Oxytocin intensifies uterine contractions.
• This continues until the child is born.

Is the secretion of Thyrotropin-Releasing Hormone (TRH) by the Hypothalamus regulated by a positive or negative feedback loop?

NEGATIVE

What two other hormones are involved in these negative feedback loops?

Thyroid-Stimulating Hormone and Thyroxin

From which tissues are those other two hormones secreted in the negative feedback loop?

In which types of organisms (on Earth) have circadian rhythms been observed?

• Animals
• Plants
• Fungi
• Cyanobacteria

What does the word 'diurnal' mean?

active during the day

What does the word nocturnal mean?

active during the night

What does the word crepuscular mean?

active at dawn or dusk

endogenous

Circadian rhythms are inherent to our bodies, or built-in

Zeitgeber

“time-giver”

entrained

synchronized

intrinsic

essential

Approximately which range of wavelengths of electromagnetic radiation are considered by humans to be 'light'?

400 - 700 nanometers

Which wavelengths (and colors) of light are detected by intrinsically-photosensitive retinal ganglion neurons (iPRGs)?

Blue light (wavelength 446 – 477 nanometers)

What is melanopsin?

a photo-sensitive G protein-coupled receptor (GPCR) that is similar to Rhodopsin used for vision.

What does melanopsin do?

When melanopsin encounters blue light, it will change shape, this will
activate an intracellular signaling pathway that will produce an electrical signal (action potential).

iPRGs contain

Melanopsin

What are the Retino-Hypothalamic Tracts?

is composed of axons that propagate action potentials from iPRGs to the SCN

How do Retino-Hypothalamic Tracts differ from the Optic Tracts?

completely separate tracts

If the SCN are destroyed, what happens to the animal's circadian rhythms?

circadian rhythmicity is lost

Where is the Pineal Gland located?

in the roof of the 3rd ventricle of the brain.

Where are the Superior Cervical Ganglia located?

anterior to the prevertebral muscles and behind the carotid sheath

What is melatonin?

is an indoleamine hormone synthesized from the amino acid L-tryptophan, which is liberated when dietary proteins are digested.

Which organ secretes melatonin?

pineal gland