Endocrine Influences Flashcards by Jamie Byrne

Outline some differences between NTs and Hormones

NT - Effect specific, Digital (All or nothing) effect, Mediate rapid changes, Short distances traveled (across synapse), voluntary control

Hormones - Widespread effects, Anologue (graded) effect, mediate long-term changes, travel long distances (circulatory system), very little voluntary control

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What are the four kinds of hormone?

Monoamine - catecholamines
Peptide -
Protein - eg. thyroid hormone
Steroid - sex hormones

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How do protein and peptides act?

Bind cell membrane

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How do steroids act?

bind mRNA -> changes protein synthesis

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Give examples of Monoamine hormones

Catecholamines eg. NA, Adr, (may be NT or hormones)

DA - NT

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What three levels may hormones act upon?

Sensory
CNS
Effector

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Give an example of how hormones affect sensory systems

Testosterone ^ detection of oestrus in the female

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How are hormone levels regulated?

Physiological by-products of their activity feed back negatively
Stimulation or inhibition of other hormones (either in regulatory chain or neg/pos feedback)
Conditioned release eg in mice LH surge is conditional upon linking with female mouse (?)

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Give an example of negative feedback

PTH -> ^ Blood [Ca], [Ca] -> vPTH

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Give an example of positive feedback

Stress response, Fergusson reflex, LH

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Why are biological rhythms in hormone levels seen?

To synchronise biological function with environmental changes

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What is the name for cycles based upon day length? Night length?

Cicadian, Circalunar (for nocturnal species - more active at the full moon)

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What are the four main endocrine systems relevant to behavioural problems?

Insulin and glucose metabolism
Thyroid hormoens
Steroid hormones - glucocorticoids and mineralocorticoids
Sex hormones

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What are the two functions of sex hormones?

Direct sexual activity directly

Gender differences - females more anxious, males more impulsive

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What does castration prepuberty cause in non primates?

Lack of testosterone means will not develop aggressive tendencies

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What peripheral endocrine effects do the sex hormones have?

Pubertal changes

eg. cheeks in tom cat

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How may sex hormones alter CNS activity?

Act as modulatory NTs - direct and genomic effect on pathway activation, changing likelihood of response to stimulus

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What hormone is affected by oestrogen?

ACTH and other stress hormones - change likely to be greater in females
This phenomenon disappears with ovariectomy

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Which hormones are involved in aggressive responses?

AVP and CRH

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What other effects do sex hormones have on the brain? How may neutering affect this?

-> neural plasticity and synapse formation

^ risk of cognitive dysfunction and long term learning disabilities

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How may sex hormones end up in the brain? What kind of effect are they said to have?

Cross BBB
Local synthesis from cholesterol
Conversion in the brain 
eg. testesterone -> oestrogen; progesterone -> pregnanolone (active metabolite) 
- Tonic effect

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What are the four stages of oestrus in the bitch?

Pro-oestrus, Oestrus (LH spike, will stand), Metoestrus (pregnancy, ~ 7 months), Anoestrus

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What occurs pre-season in the bitch? How may this affect behaviour?

3 weeks pre-season, ^FSH/LH -> ^E2
Moody, irritable, very attractive to males
When in season bitches may urine mark

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What general effect does P4 have on behaviour?

Calming

Primes behaviour for when it falls (ie. end of pregnancy it drops-> maternal behaviour)

Where are FSH and LH produced?

Anterior Pituitary

What general effect does Oestrogen have on behaviour?

^aggression especially to other bitches | lower threshold for pain and seizures

Where is oestrogen produced?

Follicles in the ovary

What effect does oestrogen have on neurobiology?

^Neurogenesis

What is the action of pregnanolone?

Acts at GABA a receptors - anxiolytic effect

What behaviours does PRL initiate?

Milk let down, grooming, maternal aggression to protect young, reduces response to stressors in rodents

What relation do P4 and PRL have?

v P4 -> ^ PRL

How may pseudopregnancies be adaptive?

Allows for co-operative rearing

When are testosterone surges experienced?

Pre-natal - causes male to be male (female = default) | Post-natal adolescent - sexual maturity changes

At what age do male dogs start to cock leg and show mounting?

6-18 months

What actions does testosterone have on behaviour and physiology?

``` v frustration tolerance ^ aggression leg cocking and mounting Anabolic (^metabolism) Converted to oestrogen in the brain - affects firing of serotinergic neurones ```

Why are testosterone levels not high all the time?

High energy cost and decreased immune function - only elevated when necessary according to the ethology of the species, hence why a breeding season may be beneficial

How is immunity affected by testosterone?

T cells

When may testosterone levels be high?

After a successful competitive encounter (shown in human sports players and fans)

If a bitch is spayed before her first season can she have a pseudopregnancy?

Why may neutering a male not be effective at dereasing aggression?

If it has become a learned response

Why may neutering a female not be effective at decreasing aggression?

Tonic levels of testosterone may have been masked by female hormones - prevailing testosterone can now cause aggression Neutering may v self confidence -> ^fear related aggression

How is oestrogen modulated?

Serotonin pathways

What type of breeders are queens?

Seasonally poly-oestrus, long day breeders (Spring->Autumn) | Induced ovulators

When are pseudopregnancies caused in the queen?

Infertile mating or other contact that induces ovulation

What is the main action of corticosteroids?

^blood glucose

How does chronic stress impact the HPA axis?

Find out!

Outline the HPA axis

Hypothalamus - CRH Anterior Pituitary - ACTH Adrenal Cortex - Glucocorticoids especially cortisol

What are the two pathological states of adrenocorticoid production?

Hyperadrenocorticism (Cushings) | Hypoadrenocortocism (Addisons)

What are the common causes of Cushings?

Cortisol secreted from adrenal cortex tumour | ACTH secreted from an anterior pituitary tumour

What is the usual cause of Addisons?

Autoimmune - Adrenal cortex detroyed -> v mineralocorticoids and possibly corticosteroids -> poor stress response

Which organs does thyroid hormone act upon?

ALL

What is the function of thyroid hormone?

Control metabolic rate | - direct centra l'impact on serotinergic activity

What are the two pathological states of thyroid hormones production?

Hypothyroidism - common in dogs, -> obesity, depression, lethargy, bilateral symmetrical alopecia, myxoedema, pendulous abdomen, caused by idiopathic autoimmune thyroid damage or thyroiditis Hyperthyroidism - common in older cats, -> weight loss, nervousness, staring eyes, poor coat, ^HR, aggression

What other form of hyperthyroidism is occasionally seen?

Depressed form - Secondary heart/kidney issues

What hormones are associated with insulin and glucose metabolism?

Cortisol and Leptin

How may insulin affect behaviour?

Cross BBB, affect food seeking behaviour and glucose metabolism

What are two pathological states associated with insulin?

Diabetes mellitus - vInsulin -> HYPERglycaemic | Insulinoma - ^Insulin -> HYPOglycaemic

What behavioural problems may be associated with insulin?

Resource guarding and stealing