Animal Behavior:
Hormonal Control

ANIMALEHAVIOR LEC 3

ANIMAL BE

ANIM

Animal Behavior, Lec. 8, BIOL 4518

What do hormones do?

Hormones are small molecules used to signal between cells

Used to coordinate among cells and systems in the body

Coordinate short-term (e.g., adreniline fight or flight response) and long-term (e.g. sensitivity to reproductive hormones)

What do hormones do?

Behavior

Growth/development

Physiology/metabolism

Molting

Metamorphosis

Migration (teleost fish)

Hormones and Behavior

Reproduction

Pair-bonding

Hunger/Thirst drives

Aggression

etc.

Neuronal vs hormonal control

Voluntary; Speed; Chemical release

General model:

Neurons detect environmental stimulus; hormones coordinate changes in systems throughout the body

What are hormones?

Small molecules used to signal among cells

Hormones

Adreniline

Oxytocin, vasopressin

Androgens (e.g., testosterone)

Estrogens (e.g., estradiol)

What are hormones- types?

Types

Steroids

Androgens (e.g., testosterone)

Estrogens (e.g., estradiol)

Derived from chloresterol, lipid soluble, go straight to DNA

Single peptides (chains of amino acids; via protein synthesis)

Bind to surface receptor; secondary messenger involved

Amines

How do hormones work?

Many require conversion to another state inside the cell

May require binding to a receptor on

cell surface

Within cell

How do hormones work?

Stimulate/inhibit release of other hormones

Influence rate of biochem reactions

Change availability of rate-limitingn step enzymes

Increase membrane permeability and availability of cofactors

Protein synthesis through gene action/RNA synthesis

Vascularity increase (blood flow to tissues)

How do hormones work?

Typically feedback system (endocrine system)

secondary hormone produced by target cell inhibits production by gland

How do hormones work?

Some are produced and stored in major glands (e.g., oxytocin)

Others are produced for immediate action (e.g., steroids)

How do hormones function?

Releasing Hormones

Gonad Releasing Hormone

Growth Hormone Releasing Hormone

Releasing hormones cause release of effectors hormones (e.g., vasopressin, oxytocin)

Where?

Classic view: Endocrine system

Systemically, e.g., the endocrine system, where hormones are released to blood, circulate to targets

Now, also

Other circ systems

Pancreatic islets

Hypothalamo-hypophysial portal

Locally: local synthesis and action

Many cells can make molecules similar or identical to endocrine glands.

Can target:

Autocrine same cell type (and itself)

Paracrine other cell types

Endocrine system-wide

Cytokines are a related class of molecules which are used to signal from cell to cell

Endocrine Glands

pituitary

thyroid

Adrenal

Testes

Ovaries

Neurons and Hormones

Nerves detect external signals

Information conveyed:

Neural control of endocrine glands

Special neurons that release hormones directly into the bloodstream; instead of neurotransmitters!!!

Longer action potentials

Hormones are distinguished from neurotransmitters because response takes longer to develop and longer time

Hormones and behavior

Target a wide range of behaviors from

Social bonding (mother/child; oxytocin, vassopressin)

Aggression

Mating behaviors

Camouflage

Poikilotherm chromatophores

Hormones and Reproduction

Tissue development is triggered by reproductive hormones (e.g., testes)

High levels of hormone/tissue development and reproductive behavior can be:

Associated

Behavior and tissue development co-occur

Disassociated

Behavior and tissue development are temporally displaced

Constant reproduction

Constantly have developed tissues require trigger for behavior

Glucocoriticoids affect mood and taste perception

Hormones and behavior

Fight or flight

Adreniline release

Changes blood supply to skeletal muscles

Widen airways

Release stored erythrocytes

Increase rate of blood clotting

Superficial vessels constricted

Temporary elevation of pain threshold

Increased awareness of environment

Piloerrection (hair stands on end)

freeze response

Circadian rhythms

Suprachiasmatic nuclei

Severing

Hormone secretion

Growth hormone

Glucocorticoid sectretions

Renal electrolyte secretions

Drinking

Pineal enzyme

Reproductive patterns

Brain receptors for nuerotransmitters etc.

Cytokines

Cytokine characteristics:

polypeptide

Short-lived

Very low concentrations

Redundancy functions of most cytokines can be performed by other cytokines

Pleiotropism single cytokine may have different functional effects even on the same cells

e.g., Biphasic effect on immune systems of glucocorticoids

short term => increase in immune function

long-term => suppression of immune function