L21 Nervous Regulation of Physiological Function Flashcards
what feedback mechanism does homeostasis rely on most?
negative feedback - returning a variable to a normal range
when does positive feedback occur in homeostasis
rarely, childbirth-pressure, blood clotting and electrical impulses in nerves
when does feedforward mechanisms occur in homeostasis?
they anticipate expected change, increased heart rate BEFORE exercise, increased secretion of insulin BEFORE food, gastric secretions BEFORE ingestion of food
why do females body water take up less of their weight (50%)?
larger fat to lean ratio of mass
what is our total body water TBW?
Men ~ 42L (60% of their weight), this makes up ICF and ECF(plasma and ISF)
How is physiological function maintained?
nervous and endocrine system
Describe Nervous System
fast acting, hardwired, electrical and chemical signalling, local cellular response and rapid response
Describe Endocrine System
slow acting, chemical signalling involving change of gene expression, long lasting responses
give an example where nervous and endocrine system co-operate to maintain homeostasis
regulation of blood pressure
what is the language of the nervous system?
electrical impulses and generated neurotransmitters
give an example of internal stimulus
pressure receptors in blood - blood pressure
give an example of an external stimulus
light detected by photoreceptors within eye
what does the efferent nervous system consist of?
the autonomic nervous system (parasympathetic and sympathetic/ enteric nervous system the gut) and the motor system
why does brain have lots of invaginations?
nerves are present more surface area and room to interact
what are cranial nerves part of?
CNS
what do cranial nerves consist of?
2 nerves - one sensory, one motor, going in opposite directions
what does the olfactory nerve do?
brings info abour smell to olfactory gull
what does the cortex control?
motor neurons in eyes - opening of iris to focus light on retina
what is a visceral afferent?
incoming pathway to brain from internal organs in body
what is a sensory afferent?
incoming pathway from body surface and proprioception such as touch and pain
what does the autonomic system do?
regulates smooth and cardiac muscles involuntarily
what does the enteric nervous system do?
controls digestive tract, pancreas, gall bladder
what does the sympathetic system do?
regulates energy generation aka fight or flight and arousal
what does the parasympathetic system do?
has antagonistic effects on target organs - promotes ‘rest and digest’
what is a ganglia?
collection of cell bodies in PNS
what is a nuclei?
collection of cell bodies in brain/ CNS
how do sympathetic and parasmypathetic systems work?
opposingly, most internal/ visceral organs have both nerves present
sweat glands only recieve sympathetic
what is a preganglionic fiber?
extends from neuron in CNS, it synapses with cell body of second neuron (efferent)
what is a post ganglionic fibre?
it recieves signal from first neuron in CNS via pre-ganglionic fibre and innervates effector organ by post ganglionic neurotransmitters
what does dual innervation of organs by both autonomic systems allow?
precise control over organ activity
name 2 nerves that are solely sensory
olfactory (smell) and optic (vision)
what are the 3 types of motor nerves
alpha, beta and gamma motor neurons
