Hormones Flashcards
Define Hormone
Chemical secreted by cells that is conveyed by the bloodstream. Acts on target tissues to produce specific physiological effects. Many are produced by endocrine glands.
One hormone may have multiple effects on different cells and behaviours (a single type of behaviour or physiological change can be affected by many different hormones)
Hormones are produced in small amounts and secreted in bursts (pulses)
Most hormone levels vary rhythmically throughout the day (circadian)
They can only affect those cells that have the corresponding receptor protein to recognise the hormone
Endocrine vs Neurotransmission
Both coordinate behaviour.
Both use chemical signals.
Neurotransmission can only follow existing pathways (axons) whereas hormones can travel anywhere via the circulatory system
Neurotransmission is fast and regulates immediate behaviours (e.g. movement) whereas hormones control longer-term processes (e.g. growth, reproduction, metabolism)
More voluntary control over your neurotransmission compared to hormone signals (e.g. control of limbs versus release of thyroid hormone)
3 Types of Hormones
- Peptides and protein hormones
Oxytocin = social bonding, milk production, childbirth contractions
Prolactin = reproductive actions, parental care behaviour
Thyroxine = metabolic functions, neural development
Vasopressin = water reabsorption in kidneys, learning, memory - Amines
Noradrenaline = a neurotransmitter and a hormone (action depends on its target) as a hormone it’s released from the adrenal gland into the bloodstream constantly at low levels/for fight or flight response e.g. to increase blood pressure
Adrenaline = similar to noradrenaline, wider range of effects to increase energy availability, releases in large amounts during stress
Melatonin = released from pineal gland during darkness, for sleep-wake regulation, anti-inflammatory effects, antioxidant - Steroids (cholesterol derivatives made up of 4 rings of carbon atoms)
Cortisol = stress response, increases metabolism
Estradiol (type of estrogen) = female sex hormone, reproductive cycles, secondary sexual characteristics, maintenance of reproductive tissues
Testosterone (type of androgen) = male sex hormone, sperm production, secondary sexual characteristics, development of male reproductive tissues
Define Feedback
Detect and evaluate the effect of the hormone
Feedback loops regulate hormone secretion to ensure there is an appropriate amount circulating in the body
and are used by the hypothalamic-pituitary axis
Negative feedback is the basic form of control that is used. The output of a hormone feeds back to inhibit the release of that hormone
Autocrine Feedbacl
An endocrine gland releases a hormone that acts on a target cell but feeds back negatively to inhibit further hormone secretion i.e. when cell sends signal to itself
Target Cell Feedback
Hormone from the endocrine gland acts on target cells to produce specific biological effects and these effects are detected by the endocrine cells to inhibit further hormone release
Brain Regulation (feedback)
The hypothalamus drives the endocrine gland via neuronal or hormonal signals, the biological response inhibits the hypothalamus i.e. hypothalamus directs the adrenal gland to secrete adrenaline and noradrenaline
Brain and Pituitary Regulation (feedback)
Hypothalamic-pituitary axis is the hypothalamus and pituitary gland (made up of anterior and posterior pituitary). Complex feedback mechanism involving the hypothalamus and anterior pituitary as well as an endocrine gland. Feedback by hormones can go via multiple routes
What does hypothalamus help manage
Body temperature
Blood pressure
Hunger/thirst
Sense of fullness when eating
Mood
Sex drive
Sleep
Define the Pituitary Gland
Sits below the hypothalamus, small (pea sized) but complex. Consists of anterior and posterior pituitary. Completely separate in their functions but are directly connected to hypothalamus via the pituitary stalk
Define Posterior Pituitary
Secretes oxytocin/vasopressin
Manufactured in 2 nuclei of the hypothalamus and transported along axons to the terminal. Action potential in the hypothalamic neurons travel down the pituitary stalk and reach their terminals in the pituitary gland. The hormones are released into the highly vascularised (i.e. lots of small blood vessels) pituitary gland and they enter the circulation immediately
Define Vasopression
Help to conserve water (thirst and water regulation). Can also be released as neurotransmitters from the hypothalamus and has a role in aggression and in promoting pair bonding. Monogamous prairie voles have been shown to have higher levels of vasopressin. Voles that are promiscuous can be turned monogamous with vasopressin
Define Oxytocin
Can act as a hormone and neurotransmitter, involved in aspects of reproductive and parental behaviour, single doses of oxytocin delivered to people via intranasal spray before playing an investment game were more willing to entrust their money to a stranger than placebo-treated players, such effects are not always able to be reliably produced
Define Anterior Pituitary
Controlled by the hypothalamus. The hypothalamic neuroendocrine cells are themselves controlled by circulating hormones, blood sugar and the immune system and synaptic inputs from a range of brain areas. The hypothalamic axons also terminate on a hypophyseal blood vessel system in the anterior pituitary. The hormones released from the anterior pituitary are tropic i.e. one that stimulates an endocrine gland to grow and secrete its hormones
Growth Hormones (psychosocial dwarfism)
Symptoms of psychosocial dwarfism are decreased growth hormone secretion, very short stature and weight and immature skeletal age
If removed from stress, they will recover
Released during sleep
Under fight or flight other essential systems also shut down such as growth (less growth hormone). Gastrointestinal functions also decrease so nutrients from food are not absorbed as normal. The combination of hormonal, metabolic and dietary factors results in physical and cognitive deficits
