Animal Behaviour - Endocrine Influences
Neurotransmitters (NTs) and hormones differ in how they influence behaviour and physiology. NTs act quickly, have specific effects, and operate over short distances with all-or-nothing responses, often under some voluntary control. Hormones act more slowly, have widespread and graded effects, influence long-term changes, and travel through the bloodstream with minimal voluntary control.
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
Key Terms
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
Ho...
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
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| Term | Definition |
|---|---|
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 |