Endocrine systems & hormones in animals Flashcards
Endocrine vs nervous system
*Nervous system
Neurotransmitters
Rapid (~100m/s)
Targeted
All-or-nothing
*Endocrine system
Hormones (“setting in motion”)
Slower (s, mins, hrs)
Large spatial area
Graded response
What do hormones do?
Regulate exocrine/endocrine gland secretions
Regulate growth and development
Control reproductive processes
Coordinate response to environmental stimuli
What are;
Glucocorticoid hormones (slighlty different structure)
Catecholamines (refers to structure of the molecule)
Adrenaline/Noradrenaline
Glucocorticoid hormones = cortisol/corticosterone
Catecholamines = Adrenaline/Noradrenaline
Adrenaline/Noradrenaline = Epinephrine/Norepinephrine
Describe some functions of insect hormones?
Juvenile hormone (in haemolymph)
Juvenile characteristics
Inhibition triggers metamorphosis
Reproductive maturity in adults
Yolk/seminal fluid production
What do these do (insects)?
Prothoracicotrophic (PTTH)
Edysone
Eclosion
Burcison
Prothoracicotrophic (PTTH): stimulates ecdysone production
Edysone: production of new cuticle
Eclosion: new cuticle
Burcison: tanning of new cuticle
HPG axis
what do these do;
*Gonadotropin-releasing hormone (GnRH)
*Follicle-stimulating hormone
*Lutenizing hormone
*Gonadotropin-releasing hormone (GnRH) produced in the hypothalamus
-Stimulates gonadotropin (FSH/LH) release
*Follicle-stimulating hormone
-Maturation of germ cells, i.e. follicular growth, spermatogenesis
*Lutenizing hormone made in pituitary gland
-Estrodiol/testosterone production
-Reproductive tissues
-Behaviour
-Negative feedback
What are the methods for studying hormones?
Correlatively
Exposure
Inhibitors
By removing/transplanting glands
Vertebrate hormones explain water soluble and lipid soluble
*Water soluble
Travel on circulatory system
Bind to surface receptors
Cascade –>signal transduction
Altered transcription
*Lipid-soluble
Need carrier proteins
Bind to receptors on surface or in nucleus
Vertebrate nervous system
PNS (peripheral nervous system)
Afferent (sensory): PNS–> CNS
Efferent (motor): CNS –>PNS
Divisions
Somatic nervous system: voluntary and reflex movements of skeletal muscles
-Acetylcholine (cholinergic)
Autonomic nervous system:
Sympathetic (mostly adrenergic, catecholamines)
-Parasympathetic (cholinergic)
Explain the autonomic nervous system
Negative feedback –>homeostasis
Control centre: hypothalamus
Parasympathetic= Feed & Breed”, “Rest & Digest”
Slowly activated dampening
-Conserves energy (e.g. heart)
Sympathetic
“fight-or-flight”
Quick response mobilising
-Mobilises energy (e.g. heart)
Direct effects of the autonomic nervous system
sympathetic
Skeletal muscles=“no” vessel vasoconstriction
Gastro-intestinal tract= Vasoconstriction; constrict sphincters; inhibit peristalsis
Periphery=Vasoconstriction
Lungs=Dilate bronchioles, vasodilation
Heart=Coronary vessel dilation; Increase contraction
Eyes=Relaxes ciliary muscles for pupil dilation
Glands=Altered hormone secretion: metabolism versus other functions!
Direct effects of the autonomic nervous system
parasympathetic
Skeletal muscles= Vasodilation; Stimulates salivary gland; accelerates peristalsis
Gastro-intestinal tract= Vasodilation
Lungs= Constrict bronchiolar diameter
Heart= Baseline contraction
Eyes= Constriction/contraction of ciliary muscles
Glands= Altered hormone secretion: metabolism versus other functions!
HPA axis and the SAM pathway
Hypothalamic-Pituitary-Adrenal axis
Sympathomedullary (‘sympathoadrenal’) Pathway
(neuroendocrine) Hypothalamus is the control centre
1. (hormone)Corticotropin-releasing hormone
(CRH) hypothalamus –> Pituitary
2. Adrenocorticotropic hormone (ACTH) pituitary adrenal gland
–>ACTH stimulates adrenal glands to produce cortisol/corticosterone
Neuroendocrine cells produce catecholamines
3. (hormonal) Negative feedback: circulating corticosteroids detected by receptors in the hypothalamus
Describe the pituitary gland
Pea-sized gland!
Human growth hormone (GH)
Thyroid-stimulating hormone (TSH)
-thyroxine in thyroid
-baseline metabolic rate
Luteinizing hormone (LH) and Follicle-stimulating hormone)
-regulates reproductive system
Prolactin
-lactation, regulates reproduction
Adrenocorticotropic hormone (ACTH)
Adrenal Gland
*Steroidogenesis
Mineralocorticoids (e.g. aldosterone)
–>blood pressure/electrolyte balance
Glucocorticoids (cortisol/corticosterone)
–>metabolism/altered immune function
*Androgens
-converted to sex hormones in gonads
-reproductive function
*Chromaffin cells
“Neuroendocrine cells” “post-ganglionic”
Epinephrine and norepinephrine
Similar structure to nerve cell, but exocytosis directly into blood stream = neurohormone
Vertebrate endocrine system: cortisol
It’s not a “stress” hormone and it lacks valence (positive and negative)
Cortisol/corticosterone =Mobilise energy, increase metabolism (alter immune function)
Stress-induced hyperthermia:
Rapid, hormonally mediated cutaneous vasoconstriction and thermogenesis in response to stress, leading to an increase in core body temperature.
Early life stressors can alter glucocorticoid receptor densities in the brain
Can also early life effects on e.g. dopamine and serotonin receptors
High DA/low 5-HT = bold & inflexible, opposite shy & environmentally sensitive
What is SAM pathway?
The sympathomedullary pathway (SAM pathway) is the route through which the brain directs the sympathetic branch of the autonomic nervous system (ANS) to activate in response to short-term stress.
