hormones- lecture 6 Flashcards
hormones
- secreted by specialised glands- endocrine
- carried in the bloodstream to specific target regions (e.g. other endocrine glands, organs, cells, the brain)
neural and endocrine communication similarities
- production of chemicals stored for later release
- stimulated to release chemicals
- some chemicals act as hormones and neurotransmitters
- react with specific receptors
neural and endocrine communication differences
- neural communication is fixed between channels to precise locations- hormonal, signalling is more generalised
- neural messages are very rapid- hormonal coomunication is slower and more prolonged
- neurotransmitters travel across the synaptic cleft- hormones travel through the blood
- some neural communication is under voluntary control- hormone release is not
hormones also regulate:
- growth and development
- metabolism (intake, production and utilisation of energy)
- maintenance of internal environment (e.g. homeostasis of bodily systems- temperature, sleep)
- control of internal organs and systems (e.g. regulation of heart rate, blood pressure, immunity)
maintenance of homeostasis
- most hormonal release is regulated by negative feedback
- output from a gland (hormones) is responsible for preventing further release
location of major endocrine glands
males
- hypothalamus, pituatry gland, thyroid gland, adrenal gland, testis
female
- pinneal gland, thymus, pancreas, ovary
the pinneal gland
- at around 20:00 the pineal gland begins to produce melatonin, levels peak in the middle of the night, then decline to low daytime amounts
control of hormone release
controlled by 2 key strictures in the brain
1. hypothalamus
2. pituitary gland
hypothalamus
located at the base of brain, hypothalamic nuclei synthesise hypothalamic releasing hormones that either stimulate or inhibit hormone release from pituitary gland
pituitary gland
releases tropic homones- hormones that influence release of hormones from other glands, anterior pituatry- controlled by hypothalamic releaing hormones, prosterior pituatry- controlled by nerve stimulation from hypothalamus
prosterior pituatry gland- due to nerve impulse what does the hypothalamus release?
Anti-diuretic Hormone (ADH / Vasopressin)
- Stimulates the re-absorption of water by kidneys
(conserves water as prevents it being lost in urine)
- Stimulates vasoconstriction (> BP in response to stress)
Oxytocin
- Causes muscle contraction in uterus (quite handy in childbirth!)
- Stimulates ejection of breast milk (quite handy, but not always!)
Oxytocin – The Tend & Befriend Hormone
- Elevated levels during sexual arousal & orgasm
- Levels respond to social stimulation
- Causing anti-stress effects (inhibiting stress hormones
oxytocin studies
grewen et al 2005
Couples rated the level of support they got from their partner
10 mins of ‘Warm Contact’
© Snuggling up on a ‘loveseat’
© Watching ‘romantic video’
© Talking about ‘times when they felt close’
anterior pituitry gland- due to hypothalamus releasing hormones
Growth Hormone – does what it says
- Pre-pubertal deficits – Pituitary
Dwarfism
- Pre-pubertal excess - Gigantism
Thyroid Stimulating Hormone- Stimulates release of Thyroxine by Thyroid Gland (regulation of metabolic rate – heart / digestive function)
Gonadotrophins - Sex Hormone Release- Luteinizing Hormone- Increases production: Progesterone (ovaries), Testosterone (testes & adrenal cortex), Follicle Stimulating Hormone- Increases production: Estrogen (ovaries), Sperm (testes)
Adrenocorticotropic Hormone (ACTH) – Stress Hormone Release-
Stimulates release of stress hormones from adrenal cortex
Prolactin
- Promotes tissue development in breasts during pregnancy
- Stimulates milk production after birth
Prolactin – The Sexual Desire Hormone?
Recent research shows that Prolactin also plays an important role in sexual desire
adrenal gland
The Adrenal Glands sit on top of the kidneys
The Adrenal Glands made up of 2 areas
- Medulla (inside)
Responds to nerve impulses from hypothalamus
- Cortex (outside)
Responds to ACTH (from Anterior Pituitary)
adrenal medulla
Secretes Noradrenaline & Adrenaline
- Increase heart rate
- Constrict peripheral blood vessels
- Glucose release
Increased blood flow & energy supply to essential areas (e.g., muscles)
Short-term preparation for stress
Flight Fight Hormones
the adrenal cortex
Secretes 3 types of hormones:
- Sex Hormones (Androgens & Estrogens)
But mostly secreted by Testes & Ovaries
- Mineralocorticoids
Aldosterone - Helps kidneys retain sodium & excrete potassium
- Maintains blood pressure
- Maintains balance of salt & water in the body
- Corticosteroids (Stress hormones)
Principally Cortisol - Maintains essential responses during stressful events
prolactin and sexual desire
Sustained elevation of prolactin post orgasm…
- Increases sexual satiety / reduces sexual desire
- Decreases likelihood of subsequent erections & orgasms
Evidence
- Multi-orgasmic men – produce significantly less prolactin at orgasm
So, no reduction in desire – ability for more orgasms
- [some] Impotence treatments (e.g., Cabergoline)
Decreases prolactin release (Prolactin Antagonist)
INCREASE Sexual desire
DECREASE Refractory period (time before able / want to have sex again
the pancreas
secretes 2 main hormones- insulin, glucagon
low blood sugar and stress- pancrease releases glucagon and liver releases glucose into blood- normal glucose levels
high blood sugar- pancreas releases insulin, excess glucose taken up by fat cells- normal glucose levels
the testes
The testes secrete Male Sex Hormones (Androgens)
Also secreted in small amounts from Adrenal Cortex
(so also produced by women)
The main Androgen is Testosterone
Production begins during foetal development (organisational effect on sex)
Testosterone burst at puberty stimulates male secondary characteristics
- Growth & development of male reproductive structures
- Increased skeletal & muscle growth
- Enlargement of larynx (& voice changes)
- Increased body hair
- Sexual drive
the ovaries
Ovaries secrete Female Sex Hormones (Estrogens)
Also secreted in small amounts from Adrenal Cortex
(so also produced by men)
At onset of puberty (female secondary characteristics)
Estradiol
- Breast development
- Distribution of fat (hips, legs, breasts)
- Maturation of uterus & vagina
Progesterone
- Thickens lining of uterus in pregnancy
Progesterone & Estradiol
- Stimulate changes in uterus during menstrual cycle
- Sexual behaviour
hormones and behaviour
Hormones do NOT cause a particular behaviour to change…
…They change the likelihood of behaviours occurring in appropriate contexts
Certain behaviours / stimuli can also influence hormone levels
e.g., Cortisol levels increase when you get stressed during exams
Testosterone levels increase when a contest has been won
BUT
Which comes first – the behaviour or the hormonal change
testing hormones/behaviour relationships
- Remove the source of a hormone
- Artificially add the hormone
Measure behaviour associated with that hormone
For example,
Castration / Ovariectomy will remove source of testosterone & estrogen
This should have an effect on sexual behaviour
Somatic Intervention or Behaviour Intervention
estrogens and sexual behaviour
Slightly more tricky to measure sexual behaviour in female rodents
Lordosis Posture of female rat to aid male penetration
Lordosis behaviour more frequent when female ‘on heat’
