Endocrine II + Stress

cue

1. What is the role of photoperiod in reproduction? 

   • They can be used as a ___ to stimulate reproductive activity

retina

circadian

optic

clock

pineal

How is photoperiod perceived in mammals

• Mammals have a photoreceptor in their ________

  • Master ________ clock is in the paired suprachiasmatic nuclei of the hypothalamic region

  • Suprachiasmatic nuclei (SCN) are dorsal to the ________ nerve

  • Neurons in the SCN express ________ genes

  • SCN clock controls the ________ gland and secretion of melatonin

deep

GnRH

hypothalamus

3rd

complex

How is photoperiod perceived in non-mammalian vertebrates

• ____ brain photoreceptors (DBP)

  • Loss of eyes has little effect on seasonal photoperiodic responses

• Thought to be connected functionally with ____ neurons responsible for regulating pituitary and gonadal activity

• All located in the ______________

• Pineal gland includes photoreceptor units with neural connections to the brain and is directly sensitive to light

  • Acts as a ___ eye

• Interaction between SCN & pineal gland in the control of circadian rhythms in nonmammalian vertebrates is __________, not well understood

Photostimulation

• when long days induce reproductive development

  • Increases in repro hormones

  • Changes in gonad physio

  • Changes in behavior

Photorefractoriness

when long eventually induce termination of repro competence

anterior

anterior or posterior pituitary?

• neurohormones travel from the hypothalamus to the anterior pituitary to stimulate or inhibit secretions by the anterior pituitary endocrine cells

  • Hormones here are synthesized and secreted by endocrine cells

  • 2 main categories of hormones:

    • Effects on nonendocrine tissues

    • Hormones that control other endocrine glands

posterior

anterior or posterior pituitary?

neurosecretory cells in the hypothalamus secrete oxytocin and vasopressin at capillaries in the pars nervosa

hypothalamus

pituitary

gonads

1. Describe the general endocrine mechanisms associated to the Hypothalamus-Pituitary-Gonadal Axis 

   • _____________: Gonadotropin releasing hormone

   • ___________: LH, FSH

     • __________: T, estrogen, progesterone

Challenge hypothesis

circulating levels of androgens correlate with aggression only during periods of social instability, and male-male interactions over social status and access to females, as well as the presence of fertile females, tend to increase plasma androgens

C

level of challenge hypothesis in which  maximum is achieved thru social stimulation from competing males or via interactions with receptive females

B

level of challenge hypothesis that is the breeding season baseline

A

level of challenge hypothesis that is basal, non-breeding season

immune

parental

1. Why is there a tradeoff between reproduction and survival mediated by testosterone?

   •  T decreases fitness by suppressing traits such as ______________ function and ____________ care

DHEA

• May be important for the expression of aggression when gonadal testosterone synthesis is low 

• Can be metabolized into active sex steroids within the brain

Pheromones

• for mate attraction and tend to act thru the vomeronasal organ; also sync up female reproductive cycles

Hypothalamus- Pituitary- Thyroid axis (HPT axis)

• Functions in growth, maturation, & metamorphosis?

• Hormones involved: thyroxine (T4), tri-iodothyronine (T3)

basal

temp

growth

1. Name three effects of the thyroid hormones 

   • Long term regulators of _______ metabolic rate

   • Maintenance of body _____ in endotherms

   • Control ________ rate?

diodinases

Local regulation of thyroid hormones

metamophosis

thyroid hormones control all the processes that go into ______________ in amphibians

Predictable

type of environmental change with regulated changes of morphology, physiology, and behavior in anticipation of the event

• day/night rhythms

• Seasons 

unpredictable

type of environmental change with rapid facultative changes of behavior and physiology during and after the event

• Predators

• Habitat loss

principle of allocation

organisms cannot simultaneously maximize all life’s functions

Allostasis

achieving stability thru change

PRP

• Perturbation Resistance Potential

  • Declines when there is a stressful event going on i.e. molt

EE

energy required for basic homeostasis

EO

allostatic overload? When the need for change to remain stable exceeds the amount of available energy

Ei

extra energy required for individual to go out, find, process, and assimilate food under ideal conditions

EG

amount of energy (in food) available in the environmen

Indirect labile perturbation

rapid events that do not affect the organism directly in the sense of reducing food or access to it

Direct labile perturbation

 longer-term environmental events that force an individual to interrupt other activities because of reduced resources such as food

min

autonomic

sympatheic

vesicles

proteins

• Phase 1 stress response: less than 1 ___

  • _____________ nervous system

  • Catecholamines act quickly bc

    • Linked to _____________ nervous system that regulates fight or flight response

    • Stored in _____________ ready for release

    • Use of existing _____________

seconds

HPA

glucocorticoid

endocrine

steroid

new

• Phase 2: a few _____________ later

  • Hypothalamus-Pituitary-Adrenals Axis (___)

  • _____________ response

  • Takes longer to appear bc

    • Linked to _____________ system

    • _____________ molecules must be produced from precursors prior to secretion

    • Once secreted, they typically exert genomic effects in their target cells, which then synthesize ___ proteins

adrenal medulla

chromaffin

Parts of the brain involved in phase 1 stress response

mammals: ________ __________

non-mammals: ___________ tissue

amygdala, hippocampus

2 parts of the brain involved in phase 2 of stress response

cortisol

stress hormone used in fish and mammals (except some rodents)

corticosterone

stress hormone in reptiles, amphibians, birds, and rodents

receptors

affinity

saturated

1. How is that one glucocorticoid such as corticosterone produces two different effects? 

   • There are 2 different ______________ which leads to transcription of different genes

   • Type I receptors have higher ______________ → corticosterone binds here first

     • Thought to act primarily in the brain to regulate the circadian variation of corticosteroids

     • Have low capacity → completely ______________ at peak circadian concentrations

   • Type II

     • Bind here once Type I is saturated

     • Regulate the classic functions of corticosteroids

energy

behavioral

preparative

brood

1. What are the possible explanations of the seasonal modulation of the adrenocortical stress response? 

   • _____________ mobilization hypothesis

   • _____________ hypothesis

   • _____________ hypothesis

   • _____________ value hypothesis

Brood value hypothesis

possible explanations of the seasonal modulation of the adrenocortical stress response

• when the value in terms of the current brood is high, then individuals should show greater resistance potential to acute stressors and the adrenocortical response is mitigated

  • If the value of the current brood is low, then susceptibility to acute perturbations should remain high (lower resistance potential) with a high likelihood of an adrenocortical response resulting in reduced repro success

Preparative hypothesis

possible explanations of the seasonal modulation of the adrenocortical stress response

• corticosteroids have a priming effect on numerous physiological systems, many of which are necessary for survival under adverse conditions

  • Seasonal peaks may provide better priming effects during those times of year

  • This would provide enhanced prep for periods when adverse conditions are more common

Behavioral hypothesis

possible explanations of the seasonal modulation of the adrenocortical stress response

• annual variation in corticosteroid concentrations result from animals having specific requirements during each life-history stage for expressing (or not expressing) corticosteroid-mediated behaviors

  • Focuses specifically on the need to seasonally regulate the expression of these behaviors

Energy mobilization hypothesis

possible explanations of the seasonal modulation of the adrenocortical stress response

corticosteroid concentrations will be highest during energetically costly times of the year