Week 1: Cell Signaling and Homeostasis Flashcards
What is Direct Contact?
- two neighboring cells having gaps in their membranes (gap junctions)
- cells from either cell react with each other creating a response
- two cells in blood stream have surface proteins
- when those proteins connect it can cause a reaction such as the release of some molecules
What is indirect contact?
- proteins/molecules manage to break through the cell membrane and can create a response if they find other receptor molecules in the blood stream
What is the paracrine system?
when cell response happens indirectly over a short distance
What is the endocrine system?
when cell response happens indirectly over a long distance. Molecules are called hormones
What is the autocrine process?
when a cells own molecules react with the cell to cause a response by binding with the cells receptors
what is a ligand?
the molecule which binds to a receptor
what is signal transduction
when the signal is bought into the cell from the receptor
what is the condition of equilibrium
the body’s internal balance
what is homeostasis
a dynamic process by which we adapt and adjust to changes in our environment to maintain functional integrity
why is homeostasis a fundamental principle of body function
- all variables pf physiological mechanisms must operate within a narrow range of values
- furthermore, there needs to be a balance between different variables. This means that homeostasis of one variable is not independent of other variables
- a core concept to understanding physiology
afferent
from sensory receptors to the CNS
efferent
from the CNS to the muscles/glands
breathing regulation
- sensor: chemosensors (carotoid bodies and aortic body)
- control centre: brain stem
- effector: diaphragm and respiratory muscles
- effector response: changes in breathing frequency and tidal volume
- regulated variable: 75-100mmHg
heart regulation
- sensor: mechanosensors (carotoid sinus and aortic arch)
- control centre: medulla
- effector: heart rate and blood pressure
- effector response: alter heart rate and peripheral resistance
- regulated variable: 93mmHg
blood glucose regulation
- senosor: fed state (chemosensors - pancreas), fasted state (chemosensors - hypothalamus/pancreas)
- control centre: pancreas
- effector: liver, adipose tissue, skeletal muscle
- effector response: alter storage/metabolism/release of glucose and its related compounds
- regulated variable: 70-110 mg/dl
core body temperature regulation
- sensor: thermoceptors (hypothalamus, skin)
- control centre: hypothalamus
- effector: blood vessels, sweat glands and skeletal muscle
- effector response: blood vessels, sweat glands and skeletal muscle
- regulated variable: 37 C
what are the different patterns in homeostasis
- tight control means that at any given time a variable will be close to the predicted value
- looser control means the variable may fluctuate in response to diurnal rhythms but they will eventually return to normal
what is gain
- the gain of a variable is the precision by which a control system can prevent deviation from homeostasis
- a control system that has a larger gain indicates that it has a more sensitive regulation that better maintains “normal” or closer to “normal” conditions
what is the calculation for gain
gain = (amount of correlation needed) / (amount of abnormality after correction)
what is negative feedback
- acts to reduce an effect e.g. thinning blood
- bring things back to normal
what is positive feedback
- acts to increase an effect
- e.g. blood clotting
what are feedforward loops
- physiological responses in anticipation of a change
- e.g. heart rate increasing prior to a race
what is a reflex response
requires knowledge from an integrating centre and a circuitry that connects the receptor and the effector
what is a local response
highly significant because they allow individual parts of the body to self regulate their responses to certain conditions
