Physiology Midterm

equilibrium

stable over time w/o the input of energy

steady state

system that is stable over time but only with the input of energy

what parameters does the body need to regulate

1. gases (O₂ and CO₂)

2. nutrient availability

3. body temp

4. water removal

5. water ion balance

6. blood volume + pressure

7. pH

8. sleep duration

9. metabolism

low body temperature receptor

thermoreceptors that use specific ion channels

low body temperature affarent pathway

relies on peripheral cord thermoreceptors in the skin, transmits signnals to spinal dorsol horm to hypothalamus

low body temperature integrating center

hypothalamus

low body temperature efferent pathway

preoptic area of hypothalamus sends signal down spinal cord uses nervous system to trigger blood vessel constriction and shivering

low body temperature effector and their action

vasoconstriction, shivering, nonshivering thermogenesis piloerection

low body temperrature negative feedback

when body temp drops

elevated blood glucose receptor

pancreatic beta cells

elevated blood glucose integrating center

pancreatic beta cells

elevated blood glucose efferent pathway

pancreatic beta cells

elevated blood glucose negative feedback

falling ECI (glucose reduces insulin secretion)

biological regulatory system pathway

stimulus —> receptor —afferent pathway→ inegrating center —efferent pathway→ effector ——→ response —→ negative feedback + repeat

how glucose regulatory system works

increased ECF (glucose) ——> pancreas (pancreatic beta cells sense glucose) and secrete insulin ——> target tissues respond to insulin to take up glucose ——> glucose goes down ——> negative feedback to pancreas

different ways integrators communicate to different cells in the body

1. endocrine system

2. nervous system

3. neuro-endocrine system

how are endocrine hormones removed from circulation

either inactivated by enzymes or excreted in urine

how does the nervous and endocrine system overlap

hormones can change properties of nervous system, and neurosecretory neurons secrete hormones into the blood stream

autocrine and paracrine regulation

provide local control within tissues/organs (not hormones)

how is strength of the endocrine system determined

the concentrating of the circulating (and available) hormones

how is strength of nervous system determined

the frequency of impulses (action potentials) of nerve cells

how does paracrine regulation provide local control

paracrine cells produce agents, and the responding cells have the receptors

how does autocrine regulation provide local control

autocrine cell has ability to produce both the cell and the receptor to respond to the agent

ex: oxytocin has autocrine agent that creates positive feedback loop when acts on receptors

acclimatization definition

alteration of existing homeostatic mechanisms, often changes system set points

involve changes in the number, size, or sensitivity of cells that are responsible for regulating homeostatic mechanism

what is the purpose of acclimatization

enables organisms to survive rapid environmental changes, usually reversible

biological rhythms

changes in dif parameters in the body that occur in a set time interval

circadian rhythms

free running in the absense of external clues: releases norepinephrine (neurotransmitter) which acts on cells in pineal gland (effector) to release melatonin (hormone)

sensory cells in retina have negative feedback loop to inhibit melatonin release

Na⁺ extracellular and intracellular concentration (mM)

extracellular: 140

intracellular: 12

K⁺ extracellular and intracellular concentration (mM)

extracellular: 5

intracellular: 150

Ca²⁺ extracellular and intracellular concentration (mM)

extracellular: 1

intracellular: 0.0001

Cl^- extracellular and intracellular concentration (mM)

extracellular: 100

intracellular: 7

basic structure of a plasma membrane

lipid bilayer of phospholipids and transmembrane proteins

lipid bilayer of plasma membrane

serves as a barrier to polar molecules and serves as an electrical insulator, and has nonpolar tails

*some molecules can pass directly through because they are lipid soluble

what are the polar membranes that require transmembrane proteins to travel across the lipid bilayer

ions, glucose, water, and amino acids

what are the lipid soluble molecules that can pass through the lipid bilayer

oxygen, CO₂, steroids, urea, and fatty acids

how does diffusion work

random thermal motion will cause molecules to move from high to low concentration until they reach equilibrium

flux definition

rate of solute flow per unit area

things that influence the net flux of a molecule across a membrane

1. temperature

2. mass of the diffusing molecules

3. viscosity of the fluid

4. area of the membrane

5. thickness of the membrane

temperature affect on net flux of a molecule across a membrane

higher temperature = more rapid movement/flux

mass affect on net flux of a molecule across a membrane

higher mass = slower movement

viscosity affect on net flux of a molecule across a membrane

higher viscosity = slower movement

area affect on net flux of a molecule across a membrane

higher area (surface area:volume) = higher flux rate

Fick equation

to determine rate of transport/flux

J = D(C₀ - C_i)

flux units: mol s^-1 m^-2

ions use ___ channels for efficient diffusion

protein-based

types of ion channels

1. voltage-gated

2. ligand-gated

3. mechanically-gated

diffusion of polar substances larger than ions requires _______ transport

carrier mediated

carrier mediated transport

single molecule transports, typically closed at one end at any given time

transport solute will bind to binding set, other side will open so the transported solute will come through

saturated kinetics

in mediated transport, limited number of transporters present in a given area of cell membrane

at low transport concentration = max rate of transport

active transport can move solutes ____ a gradient

against

Na⁺K⁺ATPase

counter transporter

3x sodium out

2x potassium in

*requires hydrolysis of 1 ATP molecule

secondary active transport

allows the coupling of one molecule moving down its concentration gradient to one moving up, driven indirectly by ATP hydrolysis

symports

transporter in same direction

antiports

transporter molecule in dif. directions

cotransport

if item being transported and counter ion are in the same direction

countertransport

if item being transported and counter ion being transported in dif. directions

bulk movement of water across membranes is mediated by

aquoporins

aquaporins play

important roles in kidneys and perform the bulk movement of water across membranes

molarity

moles of solute/liter of soln

osmolarity

osmoles of solute/liter of solvent

osmolality

osmoles of solute/kg of solvent

osmoles formula

#moles * #particles formed in soln

how does hypertonic solution of extracellular fluid alter cell size

the cell shrinks

how does isotonic solution of extracellular fluid osmolarity alter cell size

no change in cell volume

how does hypotonic solution of extracellular fluid osmolarity alter cell size

cell swells

dendrites of nerve cells

receive electrical signals and send through the cell body

cell body of nerve cells

where nucleus resides, protein synthesis and energy metabolism take place here

initial segment of nerve cell

site of regulation of transmission rate

flow of signal in nerve cells

dendrites —→ cell body —→ axon ——> axon terminal —→ synapse —→ next cell

why are dendrites and axons so long in nerve cells

because they have bundles of filaments inside

____ forms the backbone of an axon

microtubules (part of cell cytoskeleton)

two main sections of the nervous system

1. central nervous system (CNS)

2. peripheral nervous system (PNS)

two sections of the peripheral nervous sytstem (PNS)

1. Autonomic nervous system

2. Somatic nervous system

Three parts of the autonomic nervous system

1. Parasympathetic nervous system

2. Enteric nervous system

3. Sympathetic nervous system

glial cells

make up 90% of the cells in the nervous system, dont convey information but serve to support nerve cells

Schwann cells

myelinate peripheral neurons

oligodendrocytes

myelinate CNS neurons

ependymal cells

form sheets that line the brain ventricles (full of cerebral spinal fluid)

astrocyte

control composition of CNS extracellular fluid (ion and glucose concentration, permeability of capillaries) and modulate neuronal function

microglia

immune functions

myelin sheath

layers of cytoplasm wrap around axons to speed up neurotransmitters

example of a channel that is always open

K⁺ leak channels

voltage-gated channels open and close in response to changes in ____

membrane voltage potential

ligand-gated channels open in response to ___

binding of small chemical messengers

two forces to consider when ions moved in or out of cell

1. concentration gradient

2. electrical potential (separation of charges)

electrical potential

the ability (used or not) to move electrical charges (unit of Volts)

when charges move, the result is _____

an electrical current (I)

Ohm’s Law (current flow)

I =V/R

I: current flow

V: voltage

R: resistance

resting potential of a cell

determined by all of the ion channels open and functioning,

membrane potential of a neuron when it is not signaling

____ maintains the resting potential of a cell

Na⁺/K⁺ ATPase

most cells are more permeable to K⁺ than Na⁺ because of ____

leak channels

the cell is at equilibrium potential when ____ and ____ exactly balance each other out

force of concentration gradient and electrical potential

to find the equilibrium potential (E) you can use the ____

Nernst equation

Nernst Equation

E_ion= 61/z log [C_out/C_in]

what does driving force determine

if an ion will enter or exit a cell

driving force equation

driving force = membrane potential - ion potential

what does a negative driving force mean

a cation will enter the cell while an anion will exit the cell

Description of voltage-gated Na⁺ channel

channel has two gates

• a fast activation gate that opens in response to depolarization

• a slow gate inactivating gate that closes in response to depolarization

Description of voltage-gated K⁺ channel

channel has one gate that opens slowly in response to depolarization

how does an action potential start

starts as a local depolarization that exceeds the threshold

in afferent neurons, what starts an action potential

sensory events (like light hitting the retina)