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PSYC 342 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

The Synapse

Electrical & Chemical

A 
Electrical synapses (3.5nM) : 
tiny synaptic gaps crossed by ion channels from the pre- and post- synaptic neurons

Very fast, used at reflexes
Bidirectional
Degrades over distance as not all ions make it to the next cell.

Chemical synapses (20-40nM):
release of neurotransmitter by the presynaptic cell which binds to receptors on postsynaptic

Slower, does not degrade over distance as regenerated at every synapse

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2
Q

Chemical Communication Between Neurons

A

AP goes down axon

Causes NT release which changes postsynaptic membrane potential

If this hits threshold, cell fires

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3
Q

Postsynaptic Receptors

A

Ionotropic receptors have recognition sites located on the ion channel
Allow ions to enter cell to alter membrane potential
Metabotropic receptors:
A recognition site extends into the extracellular fluid, G protein on the receptor’s intracellular side.
G proteins can open nearby ion channels or activate second messengers.

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4
Q

Postsynaptic Effects

A

Excitatory postsynaptic potentials (EPSPs)
Produce slight depolarizations
Open sodium channels

Inhibitory postsynaptic potentials (IPSPs)
Produce slight hyperpolarization’s
Open either chloride or potassium channels

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5
Q

Integration of Neural Signals

A

Many EPSP and IPSP sum

If these cause threshold to be reached, you get another AP

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6
Q

GABA

A

Normally does movement

If it malfunctions, anxiety, huntington’s, epilepsy

Is the main Inhibitory NT

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7
Q

Glutamate

A

Main excitatory NT

In cns it is involved in memory

Malfunction: neuron loss after stroke

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8
Q

Why is Inhibition Important?

A

Tetanospasmin (tetanus toxin) moves through nervous system from a wound using the retrograde transport in axons.
Prevents the release of GABA from presynaptic terminals
Without inhibitory input from GABA, muscles go into involuntary contractions

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9
Q

NTs get deactivated by

A

Diffusion

Deactivating enzymes

Reuptake

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10
Q

Reasons for use of chemical communication

A

Works well over long distances
i.e. toe up to primary sensory cortex
Development and learning
alter efficacy of message with changes in receptors, transporters or transmitter production
Centralized control
Major excitatory and inhibitory transmitters, everything else modulates this overall message

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11
Q

Interactions between the nervous and hormonal system

A

Interacting: NS controls hormone and cytokine release; hormones affect neuronal firing

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12
Q

The definition of a hormone

A

Chemical messenger effective in minute quantities
Synthesized in ductless glands
Duct: distinct passage from gland to epidermis (exocrine)
Secreted into and transported by blood
Acts on receptors located far away from synthesis
Exerts a specific regulatory effect on target cell

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13
Q

Exceptions to the definition/rules of hormones

4

A

Some hormones not synthesized in ductless glands
Hormones sometimes act as neurotransmitters (paracrine function)
Can influence cell that released them (autocrine function)
Hormones have different effects depending on the specific receptor type
E.g. Estrogens have cytoplasmic and membrane receptors (so one hormone may have multiple types of receptors each with their own action)

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14
Q

Two chemical classes of hormones

A

1) amino acids and peptides

2) steroid hormones (four-ringed chemical base)

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15
Q

Corticotropin Releasing Hormone (CRH)

A

Synthesized in the anterior paraventricular nucleus (PVN) of the hypothalamus
Stimulates the secretion of Adrenocorticotropic Hormone (ACTH) from the anterior pituitary
Neural control of hormone release from pituitary
Released in a pulsatile manner, diurnally

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16
Q

Gonadotropin Releasing Hormone (GnRH)

A

Synthesized in the preoptic area (POA) of the Hypothalamus

Controls the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary

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17
Q

Thyrotropin Releasing Hormone (TRH)

A

Synthesized in the PVN of the Hypothalamus

Stimulates cells in the anterior pituitary gland to produce and release thyroid-stimulating hormone (TSH)

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18
Q

Growth Hormone Releasing Hormone (GHRH)

A

Secreted within the ventromedial nucleus (VMH) and the arcuate nucleus (ARC) of the Hypothalamus
Stimulates Growth Hormone (GH) secretion from the anterior pituitary

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19
Q

Somatostatin

A

Secreted by the VM of the HT
Inhibits GH and TSH
Also referred to as Growth Hormone Inhibiting Hormone

Also inhibitory effects on gut hormones: insulin, secretin production

20
Q

Dopamine

A

Neurons located in the arcuate nucleus of the Hypothalamus
Tuberoinfundibular dopamine pathway

When dopamine released here it inhibits prolactin release from the pituitary
Decrease in dopamine inhibition leads to prolactin release

21
Q

Oxytocin and Vasopressin

A

Synthesized in the supraoptic nucleus (SON) and in PVN of the HT
Neurons pass into the posterior pituitary and release hormone into the blood stream

Vasopressin also referred to as antidiuretic hormone
Regulates water balance, blood pressure, territoriality, bonding
More male
Oxytocin: uterine contractions, parental behaviors, attachment bonds, trust
More female

22
Q

The Pituitary

A

Also called the Hypophysis
Attached to the HT by the hypohyseal stalk (infundibulum)
Anterior pituitary
Posterior pituitary
Anterior releases six hormones, mostly trophic
Posterior releases two non-trophic

23
Q

The Hormones of the PT

A 
Adrenocorticotropic hormone (ACTH) - Adrenal Cortex (anterior)
stimulates the synthesis and release of the glucocorticoids, mineralocorticoids and androgenic steroids from the adrenal glands

Thyroid-stimulating hormone (TSH) - Thyroid gland (anterior)TSH attaches to receptors in the thyroid gland and stimulates the uptake of iodide and the release of the thyroid hormones T3 and T4 . TSH circulates in the blood in an unbound state and its secretion comes under the control of both excitatory and inhibitory control from the hypothalamus (TRH is excitatory and somatostatin is inhibitory) but is also modulated by
inhibitory feedback from the circulating thyroid hormones.

Luteinizing hormone (LH) – Gonads (anterior)

Follicle-stimulating hormone (FSH) – Gonads (anterior)

Growth Hormone (GH; anterior) – Bone and Muscle (anterior)

Prolactin (PRL) - Mammary Glands (anterior)

Oxytocin (OXT) – Uterus and mammary glands (posterior)

Vasopressin (VP) - H2O retention, respectively (posterior)

24
Q

Trophic

A

woks on an organ to cause it to release a hormone

ACTH
TSH
LH
FSH

25
Q

The HT-PT relationship

Is it 1-1 or 1 directional?

A

Hormones of the HT stimulate secretion of hormones from the PT
Not one to one relationship (e.g., CRH ≠ ACTH)
The small distance from the hypothalamus to the PT gland means you can have very small amounts of CRH etc which cause large amounts of ACTH etc top be released
Not unidirectional (PT hormones affect HT)
Not only regulated by HT but also by neurotransmitters

26
Q

Why so elaborate?

A

Allows for negative feedback, allows homeostatic control

27
Q

Acromegally

A

if old, just the areas that never stop growing (like the jaw)

if young, all areas eg Andre the giant

Usually caused by an adenoma of the PT gland

Increased GH

28
Q

The Pineal Gland

A

Superior to third ventricle and anterior to cerebellum
Produces the hormone melatonin
Under control of the suprachiasmatic nucleus (SCN) in the hypothalamus
Involved with coordinating sleep/wake cycle
Get back to this at the end of the semester with chronobiology

29
Q

Glands outside of the CNS

A 
Where the trophic pituitary hormones act:
Thyroid gland
Adrenal gland
Gonads
Ovaries and testes

Pancreas is also an endocrine gland outside of the CNS
Not activated by the hypothalamus pituitary connection
Can be inhibited by somatostatin, released from the hypothalamus to slow growth process

30
Q

2 glands outside of the pit glands control

A

pineal

pancreas

31
Q

Amino acids

A

include the catecholamines, the indoleamines and the thyroid hormones

Adrenalin + nor

Indolaemines: indoleamines consist of serotonin, synthesised from tryptophan in the CNS, and melatonin

32
Q

Peptide hormones

A

Long chains of AAs

Small peptide hormones include: oxytocin, vasopressin, thyrotropin-releasing
hormone, angiotensin, somatostatin and luteinising hormone-releasing
hormone. Large peptide hormones include: secretin, calcitonin, gastrins,
glucagon and adrenocorticotropic hormone. Polypeptide (or protein) hormones include: insulin, parathyroid hormone and growth hormone.

33
Q

Steroid hormones

A

Are lipid soluble

In blood, often bound to albumin or sex hormone binding globulin

34
Q

Androgens

A

Steroids

The key androgens are testosterone (T), dehydroepiandrosterone (DHEA), androstenedione
and 5-dihydrotestosterone (DHT)

Testosterone is the principal circulating androgen, more than 95% of this steroid being produced by the 350–500 million Leydig cells in the testes. These secrete
around 5000 g per day leading to plasma concentrations of around 700 ng/100 ml (Norman and Litwack, 1987). The remainder is produced by the
adrenal cortex of the adrenal glands. Testosterone (but not DHT) can be converted into estradiol via the enzyme aromatase

Testosterone is also a potent androgen
in women, but levels are around a tenth of those in males; testosterone production shows considerable variability in females in that an increase of 20–30% is seen around the middle of the menstrual cycle (Judd and Yen, 1973). Around 50% of circulating testosterone comes from the ovarian production of the testosterone precursor androstenedione, the remainder coming from adrenal activity. As women age, then levels of androstenedione decline, with a reduction in levels after the menopause to around half those of women of reproductive age

35
Q

Estrogens and progestins

A

In females the two most important steroid hormones are 17-estradiol and
progesterone

In the ovaries in non-pregnant
females, the follicles principally secrete estradiol and estrone; during pregnancy estriol is the principal estrogen secreted by the placenta. Progesterone
(the principal progestin and named for its progestational role in maintaining pregnancy) is produced by the follicles in non-pregnant females, and by the corpus luteum in pregnant females. Secretion and plasma concentrations of these steroids are greatly determined by the menstrual cycle, for example
levels of estradiol range from around 6 ng/100 ml in the early follicular phase to 60 ng/100 ml in the late follicular phase (Norman and Litwack, 1987). In
general the estrogens stimulate the development of the internal reproductive structures and later promote female secondary sexual characteristics (e.g.
breast development, fat deposition), and promote water retention, calcium metabolism, the stages of pregnancy, and certain reproductive and maternal behaviours

36
Q

Corticoids

A

Made in adrenal gland
corticosterone and cortisol (sometimes referred to
as hydrocortisone

Work on glucose metabolism, they increase glycerol and free fatty acid release from cells; increase muscle lactate release; inhibit glycogen breakdown; alter carbohydrate metabolism; reduce calcium absorption; suppress the immune system; and influence heart rate

levels drop in the late evening and then rise sharply before waking to then show a steady decline throughout the day

The second type of corticoid are the mineralocorticoids, which consist of aldosterone and 11-deoxycorticosterone (DOC). They principally act to maintain blood pressure and water and salt balance
in the body by helping the kidneys retain sodium and excrete potassium. When aldosterone production falls below a certain point, the kidneys are not able to regulate salt and water balance, causing blood volume and blood pressure to drop

37
Q

Prohormones

POMC

A

Prohormones’ are the precursors to ‘true’ hormones and can consist of modified molecules, or molecules that have split to form a particular hormone. A key prohormone is proopiomelanocortin (POMC), a large molecule which is composed of different sections, each section capable of producing a different hormone. One
section forms beta-lipoprotein, which in turn is the precursor for the hormone/neurotransmitter beta-endorphin (an endogenous opiate). Other sections can be synthesized into melanocyte-stimulating hormone (MSH) and adrenocorticotropic hormone (ACTH), both of which are located within the pituitary gland. In fact, testosterone also acts as a prohormone because it
serves as the precursor for both dihydrotestosterone (DHT) and estradiol.

38
Q

ACTH

A

Released from the anterior pituitary in response to

39
Q

Thyroid gland

A

In neck
Makes t4 and t3
Needs iodate
Lack of this causes goiter

40
Q

Adrenal glands

3 zones

A

They are located on the top of the kidneys and consist of two distinct structures. The adrenal cortex comprises around 90% of the total volume of the adrenal glands and consists of three distinct zones. The zona glomerulosa acts independently of the other zones and produces only aldosterone.

The zona fasciculata and the zona reticularis produce cortisol, androgens and small amounts of estrogens, and both work in conjunction under the control of ACTH.

The adrenal medulla releases three monoamine
hormones, adrenaline, noradrenaline and dopamine; it also releases a class of protein hormones – the enkephalins.
41
Q

Ovaries + hormonal control of the M cycle

A

the cycle is normally split into three stages: menses (days
1–5), follicular (days 6–14) and luteal (days 15–28).

During the follicular phase rising levels of FSH (and small amounts of LH) cause the follicles to mature, and as they do so they release estrogen which thickens the lining of
the uterus and alters the composition of the cervical mucus.
When estrogen levels reach a certain point this triggers the pituitary to secrete high levels of LH (via stimulation from the hypothalamus), which causes a follicle to
release an egg (ovulation).

During the luteal phase the ruptured follicle becomes the corpus luteum, and this secretes some estrogen and more progesterone which are necessary for maintaining a pregnancy (should the egg be fertilised).

If the egg remains unfertilised, levels of all hormones fall and the uterus lining is discarded during menses

42
Q

Testes

A

Leydig cells (also called interstitial cells)

Principally produce testosterone but also smaller
amounts of dihydrotestosterone, dehydroepiandrosterone, estradiol, estrone,
progesterone and androstenedione

43
Q

Hormones that cannot cross membranes

A

Interact with cytoplasmic receptors. All polypeptide hormones, as well as monoamines and prostaglandins are this type. Act via metabotropic receptors and their associated G proteins.

44
Q

Hormones that can cross membranes

A

Cross and bind to intracellular receptors, enter the nucleus and bind to chromosomal acceptor sites. Affects transcription to exert its effects.

Thyroid and steroid hormones, various fatty acids and the eicosanoids work in this fashion

45
Q

Hormone levels are

A

Controlled by less or more secretion typically

This is often, though not always, controlled by negative feedback

PSYC 342 (27 decks)

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