Endocrine Influences Flashcards
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
What are the four kinds of hormone?
Monoamine - catecholamines
Peptide -
Protein - eg. thyroid hormone
Steroid - sex hormones
How do protein and peptides act?
Bind cell membrane
How do steroids act?
bind mRNA -> changes protein synthesis
Give examples of Monoamine hormones
Catecholamines eg. NA, Adr, (may be NT or hormones)
DA - NT
What three levels may hormones act upon?
Sensory
CNS
Effector
Give an example of how hormones affect sensory systems
Testosterone ^ detection of oestrus in the female
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 (?)
Give an example of negative feedback
PTH -> ^ Blood [Ca], [Ca] -> vPTH
Give an example of positive feedback
Stress response, Fergusson reflex, LH
Why are biological rhythms in hormone levels seen?
To synchronise biological function with environmental changes
What is the name for cycles based upon day length? Night length?
Cicadian, Circalunar (for nocturnal species - more active at the full moon)
What are the four main endocrine systems relevant to behavioural problems?
Insulin and glucose metabolism
Thyroid hormoens
Steroid hormones - glucocorticoids and mineralocorticoids
Sex hormones
What are the two functions of sex hormones?
Direct sexual activity directly
Gender differences - females more anxious, males more impulsive
What does castration prepuberty cause in non primates?
Lack of testosterone means will not develop aggressive tendencies
What peripheral endocrine effects do the sex hormones have?
Pubertal changes
eg. cheeks in tom cat
How may sex hormones alter CNS activity?
Act as modulatory NTs - direct and genomic effect on pathway activation, changing likelihood of response to stimulus
What hormone is affected by oestrogen?
ACTH and other stress hormones - change likely to be greater in females
This phenomenon disappears with ovariectomy
Which hormones are involved in aggressive responses?
AVP and CRH
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
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
What are the four stages of oestrus in the bitch?
Pro-oestrus, Oestrus (LH spike, will stand), Metoestrus (pregnancy, ~ 7 months), Anoestrus
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
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?
NO
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
