Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Clinical Immunology and Biochemistry > Hypothalamus and Pituitary > Flashcards

Hypothalamus and Pituitary Flashcards

1
Q

What is the function of the hypothalamus and pituitary glands?

A

The hypothalamus is responsible for direct control of the endocrine system through the pituitary gland

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is the hypothalamus?

A

In the brain, below the thalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where is the pituitary gland?

A

The pituitary is located at the base of the brain, just below the hypothalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How are the hypothalamus and the pituitary gland connected?

A

Through the pituitary stalk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the structure of the pituitary gland

A

Small pea-sized gland below brain
Consists of 3 parts:
- Anterior lobe (adenohypophysis)
• glandular tissue, controlled by humoral releasing peptides from hypothalamus (via hypothalamo-hypophyseal portal system)
- Posterior lobe (neurohypophysis)
• neural tissue, made up of nerve-endings of neurones with cell bodies in the hypothalamus
- Intermediate lobe (pars intermedia) (not distinct in humans)
• glandular tissue, alternative processing of proopiomelanocortin (POMC)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which part of the pituitary gland is not distinct in humans?

A

The intermediate lobe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the hierarchy of the endocrine system

A

The hypothalamus releases hormones into the hypothalamo-hypophyseal portal system

These hormones act on the anterior pituitary, causing the release of trophic hormones

These trophic hormones pass the the circulatory system to their target organs, where they cause a response.

The target organs release hormones, which act as a negative feedback impulse, either directly; by acting on the anterior pituitary, or indirectly; by acting on the hypothalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the release pathway of GnRH

A

The hypothalamus releases GnRH into the hypophyseal
portal system.
The GnRH binds to receptors on the anterior pituitary, and stimulates the release of LH and FSH.
LH and FSH passes through the bloodstream to the gonads, where they stimulate the release of sex steroids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the release pathway of TRH

A

The hypothalamus releases TRH into the hypophyseal
portal system.
The TRH binds to receptors on the anterior pituitary, and stimulates the release of TSH.
TSH passes through the bloodstream to the thyroid, where they stimulate the release of sex T3 and T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the release pathway of CRH

A

The hypothalamus releases CRH into the hypophyseal
portal system.
The CRH binds to receptors on the anterior pituitary, and stimulates the release of ACTH.
ACTH passes through the bloodstream to the adrenal glands, where they stimulate the release of corticosteroids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the release pathway of GHRF

A

The hypothalamus releases GHRF into the hypophyseal
portal system.
The GHRF binds to receptors on the anterior pituitary, and stimulates the release of GH.
GH passes through the bloodstream to the body tissues, where they stimulate growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the methods by whi hormone release is controlled

A

Direct negative feedback (where negative feedback acts directly on the anterior pituitary)
Indirect negative feedback (where negative feedback acts on the hypothalamus, and the hypothalamus acts on the anterior pituitary)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the types of endocrine disorders?

A

Primary
Secondary
Tertiary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are primary endocrine disorders?

A

Lesion is on the endocrine organ - direct effect on hormone production, leading to pathological changes in metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are secondary endocrine disorders?

A

Secondary disorders occur when the endocrine organ is affected by lesions in another tissue. This is usually the pituitary, as it produces trophic hormones which control the activity of most of the endocrine organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are tertiary endocrine disorders?

A

-Hypothalamus-releasing factors control release of trophic hormones by the pituitary.

Lesion in the hypothalamus causes dysfunction of the pituitary, which causes dysfunction of an endocrine organ.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is negative feedback?

A

The production of most hormones is controlled by a negative feedback loop. e.g. TSH stimulates thyroid hormone production, thyroid hormone inhibits TSH production.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What hormones are released by the anterior pituitary gland?

A 
GH
Prolactin
TSH
FSH
LH
ACTH
β-lipotrophin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the function of GH?

A

Somatomedin synthesis, hence growth stimulation

Metabolic regulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the function of prolactin?

A

Lactation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the function of TSH?

A

T3 & T4 synthesis & release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the function of FSH?

A

Oestrogen synthesis
Oogenesis
Spermatogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the function of LH?

A

Ovulation
Corpus luteum (progesterone production)
Testosterone synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the function of ACTH?

A

Glucocorticoid synthesis & release

Pigmentation (or αMSH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the function of β-lipotrophin?

A

Precursor of endorphins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe the cycle of hormone release

A

Many pituitary hormones are secreted cyclically

- Circadian rhythms observable e.g. in cortisol are due to circadian variation in release of ACTH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Why is it important to know the cycles of hormone release?

A

When samples are collected, the time of day that they are collected needs to be noted.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How large is GH?

A

191 aa protein hormone

29
Q

What hormones control the release of GH?

A

GNRH

Somatostatin

30
Q

What diseases result from excessive GH production?

A

Gigantism (children)

Acromegaly (adults)

31
Q

What diseases result from deficient GH production?

A 
Growth retardation (children)
Fatigue/reduced muscle strength (adults)
32
Q

What are the metabolic actions of GH?

A

Increased lipolysis (ketogenic)
Increased hepatic glucose production (diabetogenic)
Increased protein synthesis (anabolic)

33
Q

What is the function of somatostatin?

A

Inhibits GH
Inhibits TSH
Inhibits Gastrin, Insulin, Glucagon (paracrine - produced by islet d-cells)

34
Q

How is assessment of GH disorders complicated?

A

Complicated by cyclical secretion

35
Q

What is the normal GH level?

A

> 20 mU/l

36
Q

How can GH deficiency be detected?

A

Normal is >20 mU/l - less during sleep or after exercise indicates possible deficiency

Perform insulin hypoglycaemia (glu < 2.2 mmol/l) test – inject short-acting insulin in clinically controlled conditions

GH increases over 20 mU/l – no deficiency
No stimulation - GH deficiency diagnosed

37
Q

How can GH excess be detected?

A

GH may be measured by oral glucose tolerance test (OGTT)
GH normally suppressed by glucose
Not suppressed if produced by tumour

38
Q

How can GH excess be treated?

A

GH excess usually due to pituitary adenoma

Surgery/radiotherapy
Octreotide/bromocriptine

39
Q

How large is prolactin?

A

198 aa protein

40
Q

What is the function of prolactin?

A

Stimulates lactation

41
Q

What is hyperprolactnaemia?

A

Excess prolactin in the blood >600 mU/l

42
Q

What causes hyperprolactinaemia?

A

Usually due to prolactinoma

43
Q

What can hyperprolactinaemia cause?

A

Inhibits GnRH pulsatile release from hypothalamus

Causes infertility (impotence or amenorrhoea)

44
Q

What can cause hypopituitarism ?

A 
Tumours
Trauma
Infection,
Hypothalamic disorders
Iatrogenic (e.g. treatment of tumours)
45
Q

How can hypopituitarism be assessed?

A

Using anterior pituitary function test:

  • Assay resting glucose; ACTH/cortisol; FSH; LH; TSH; T4; GH; testosterone/oestradiol
  • Assay following bolus of TRH, GnRH and insulin ~every 15 mins for next 2h

Sub-normal response indicates hypopituitarism

46
Q

What is the precursor of ACTH?

A

POMC (Proopiomelanocortin)

47
Q

What is POMC a precursor of?

A

ACTH
MSH
β-endorphin (but not enkephalins)
β-lipotropin

48
Q

How is POMC processed in the anterior lobe of the pituitary?

A

Cleaved by PC1 to produce ACTH and β-lipotropin

49
Q

How is POCM processed in the Intermediate Lobe of the pituitary/ Hypothalamus

A

Cleaved by PC1 to produce ACTH and β-lipotropin

ACTH then cleaved by PC2 to produce α-MSH and CLIP

β-lipotropin is cleaved by PC2 to produce γ-lipotrophin and β-endorphin

CLIP and γ-lipotrophin are then trimmed by exopeptidases to produce βCT and β-MSH

50
Q

Where is β cell tropin produced?

A

Neurointermediate (NIL) pituitary

51
Q

What is the function of β cell tropin?

A

Potentiator of GSIS (and amylin secretion)

  • potent monophasic effect at low glucose (ED50 ~ 20 pM)
  • increased biphasic effect at high glucose
52
Q

What is the effect of β cell tropin in diabetics?

A

β CT potentiates biphasic response to high glucose

53
Q

How many melanocortin receptors are there?

A

5

54
Q

What are the roles of the different melanocortin receptors?

A

MC1R, MC2R and MC5R have established roles in pigmentation in the skin, adrenal steroidogenesis and thermoregulation respectively

MC3R and MC4R expressed in brain
- role in feeding modulation - k/o leads to obesity (hypothalamic POMC expression modulated by leptin)

55
Q

How is ACTH release controlled?

A

Controlled by CRH (CRF)

56
Q

What causes Cushing’s Disease?

A

Increased ACTH release due to tumour causes increased corticosteroid release, leading to Cushing’s Disease

57
Q

What is the difference between Cushing’s Syndrome and Cushing’s Disease?

A

Cushing’s Disease is caused by increased ACTH release due to tumour causes increased corticosteroid release

Cushing’s Syndrome if increased corticosteroid due to
other causes

58
Q

How can Cushing’s Disease be tested for?

A

Dexamethasone (synthetic glucorticoid) suppression test for Cushing’s disease (confirmed of plasma cortisol is above reference range - ~200mmol/l)

59
Q

What causes Addison’s Disease?

A

A primary defect in corticosteroid production leads to loss of inhibitory feedback on CRH/ACTH secretion, hence overproduction of ACTH - also causes increased pigmentation

60
Q

How can Addison’s Disease be tested for?

A

Administering Synacthen (ACTH1- 24; “Short ACTH”)

Addison’s Disease confirmed if patient’s plasma cortisol level below reference range after 60 minutes

61
Q

What hormones are released by the posterior pituitary hormone?

A

Oxytocin

Vasopressin

62
Q

How are posterior pituitary hormones produced?

A

Synthesised in hypothalamus and released from nerve endings in posterior pituitary

63
Q

What is the function of oxytocin?

A

Control of uterine contractility and milk release

64
Q

How large is oxytocin?

A

9aa protein

65
Q

Give an example of positive feedback

A

Oxytocin release:

  • suckling causes increased stimulation of afferent nerves from breast
  • causes increased pituitary secretion of oxytocin
  • causes increased lactation - more suckling “letdown reflex”
66
Q

What is the function of vasopressin?

A

Controls water & mineral balance

67
Q

How is release of vasopressin controlled?

A

Increased osmolality at hypothalamus - increased secretion

Decreased osmolality at hypothalamus - decreased secretion

68
Q

What can a deficiency of vasopressin cause?

A

Diabetes insipidus

Clinical Immunology and Biochemistry (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions