HOMEOSTASIS

what is the definition of homeostasis

an active and dynamic process to maintain a stable interval environment to sustain life, despite external changes

what are neurones

high specialised nerve cells that respond to stimuli and transmit electrical impulses, which are only found in the brain, spinal cord and nerves

where do afferent neurones carry information from

sensory neurones - they carry sensory information from receptors to the CNS as their cell bodies are located outside of the spinal cord

where do efferent neurons carry information from 

motor neurones - they carry information from the brain to the PNS as their cell bodies are located in the ventral horn of the spinal cord

describe a negative feedback loop

• the stimulus produces a change

• the change is detected by a receptor

• the information is sent along the afferent pathway to the control centre

• the information is then sent along the efferent pathway to the effecot

• the effector feeds back to reduce the effect of the stimulus to return the variable to the homeostatic level

what is a positive feedback loop

when the change in variable is enhanced not reversed like blood clotting or labour

what are the major glands in the endocrine system 

• the hypothalamus 

• the thyroid 

• the adrenal and pituitary glands

• the pancreas

• the uterus and ovaries 

• the testes

where is oxytocin released from

the posterior pituitary gland

what does oxytocin cause

uterine contractions, milk ejection, social and psychological cues like trust and bonding

what does ADH stand for and where is it released from 

antidiuretic hormone 

the posterior pituitary gland 

what does oxytocin cause

the regulation of water reabsorption in the kidneys and blood pressure

what does the thyroid gland produce

T3

T4

calcitonin

what are the main functions of the thyroid gland

to enhance metabolism, protein synthesis and growth 

increase basal metabolic rate, oxygen consumption and energy expenditure 

reduces blood calcium levels by inhibiting bone reabsorption 

what does the parathyroid gland release

parathyroid hormone

what does parathyroid hormone cause

regulation of blood calcium due to stimulation of osteoclasts, increasing kidney calcium reabsorption and stimulating calcitriol production - causes intestinal calcium absorption

what are the regions of the adrenal gland

the outer and middle cortex, adrogens and medulla

what hormone does the outer cortex of the adrenal gland release and what does it cause

aldosterone

regulates sodium and water balance which effects blood pressure

what hormone does the middle cortex of the adrenal gland release and what does it cause

cortisol

controls metabolism and stress response

what hormone does the medulla of the adrenal gland release

catecholomines

fight or flight response, increase HR, blood flow and energy availability 

what do androgens cause

they contribute to secondary sex characteristics

what is dopamine

a neurotransmitter in the nervous system

a neurohormone in the hypothalamic-pituitary system

what are the 3 types of endocrine gland stimuli

1. humeral stimulus

2. neural stimulus

3. hormonal stimulus

what are the 3 types of signalling

1. endocrine signalling

2. paracrine signalling 

3. autocrine signalling

what is the distance and duration of endocrine signalling effects

distance = far

duration = long lasting

what is the distance and duration of paracrine signalling effects

distance = effects are localized to adjacent or nearby cells

duration = short term and immediate

what is the duration and distance of autocrine signalling effects

distance = effects the same cell it was released from

duration = immediate and self regulating