PHYS 215: Midterms

homeostasis

process by which organisms maintain a relatively stable internal environment

four parts of homeostatic control system

stimulus

receptor

control center

effector

negative feedback loop

-A feedback loop that causes a system to change in the opposite direction from which it is moving

-ex: body temp, blood sugar

positive feedback loop

Causes a system to change further in the same direction/amplifies.

-ex: blood clotting, labor

why is negative feedback more common?

it keeps the body at a dynamic equilibrium

set point

a physiological level or setting that the body attempts to maintain through a self-regulating system

passive transport

the movement of substances across a cell membrane without the use of energy by the cell

diffusion

moves with conc gradient

active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference

facilitated diffusion

Movement of specific molecules across cell membranes through protein channels (carriers)

no ATP

osmosis

Diffusion of water through a selectively permeable membrane

what drives osmosis

osmotic pressure

osmotic pressure

pressure that must be applied to prevent osmotic movement across a selectively permeable membrane

membrane potential

the voltage difference across a membrane

Na+/K+ pump

3 Na+ out, 2 K+ in

primary active transport

-Active transport that relies directly on the hydrolysis of ATP

-Ex: Na/K pump

secondary active transport

-use preexisting gradient to drive transport of solute

-Ex: Na/Glucose Transporter

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

Exocytosis

release of substances out a cell by the fusion of a vesicle with the membrane.

Cytoskeleton

A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement

How does the plasma membrane maintain selectivity?

phospholipid bilayer

acts as a barrier to larger/charged molecules

Chromatin

-granular material visible within the nucleus; consists of DNA tightly coiled around proteins

-less condensed

chromosomes

-threadlike structures made of DNA molecules that contain the genes

-more condensed

paracrine signaling

secreted molecules diffuse locally and trigger a response in neighboring cells

paracrine signaling example

growth factors, which stimulate nearby target cells to grow and divide

Neurotransmitter signaling

-synapse

-rapid-response and action

steroid signaling

-lipid soluble/nonpolar

-travel through bloodstream

-long-lasting effects

Signal Transduction

The linkage of a mechanical, chemical, or electromagnetic stimulus to a specific cellular response.

G protein-coupled receptors (GPCRs)

-large family of integral membrane proteins involved in signal transduction

-characterized by their 7 membrane-spanning alpha-helices

-utilize heterotrimeric G protein to transmit signals to effector cells

autocrine signaling

the target cell is also the secreting cell

endocrine signaling

-secreted molecules diffuse into the bloodstream and trigger responses in target cells anywhere in the body

-slow, long-lasting

synaptic signaling

-a nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell

-rapid response

resting membrane potential of neuron

-70mV

sequence of action potential

depolarization

repolarization

hyperpolarization,

refractory period

all-or-none principle

the law that the neuron either fires at 100% or not at all

myelinization affect action potential propagation

-speeds up action potential

-acts as an electrical insulator

-saltatory conduction

saltatory conduction

the jumping of action potentials from node to node

how does synapse transmit to next neuron?

presynaptic neuron

vesicle

neurotransmitters

synaptic cleft

postsynaptic neuron

depolarization

-potential moves to less negative values

-influx of Na+

repolarization

-potential returns towards resting membrane potential after depolarization

-efflux of K+

3 major regions of the brain

forebrain, midbrain, hindbrain

forebrain

-develops into cerebrum and diencephlon (cerebral cortex)

forebrain function

Perception, conscious awareness, cognition, and voluntary action

midbrain

Region between the hindbrain and the forebrain

midbrain function

(mesencephalon) relay center for visual and auditory information, controls eye and bodily movements

hindbrain

medulla, pons, cerebellum

Hindbrain function

refined motor movements, vital functioning (breathing, digestion), arousal and alertness

Cerebellum function

coordination of voluntary movements and balance

reticular activating system

-Located in the upper brain stem

-responsible for maintenance of consciousness, specifically: arousal, wakefulness, and attention

cerebral cortex

-information-processing center

-planning, learning, memory, complex emotion

regulation of sleep

-adenosine/homeostatic regulator decreases orexin neurons

-then decrease in monoaminergic neurons

-increased sleep centers

regulation of wakefulness

-suprachiasmatic nucleus, negative energy balance, & limbic system activity triggers:

-increase of orexin neurons

-increase of monoaminergic neurons

-travels to thalamus and cortex

-decreased sleep center activity

brain regions involved in consciousness

suprachiasmatic nucleus (SCN)

monoaminergic RAS nuclei

orexin-secreting neurons

acetylcholine-secreting neurons

sleep center (GABAergic neurons)

five special senses

olfaction, gustation, vision, equilibrium, hearing

Nociceptors

pain receptors

Photoreceptors

respond to light

Mechanoreceptors

respond to touch, pressure, vibration, and stretch

(hearing, equilibrium)

Chemoreceptors

respond to chemicals (olfactory and taste receptors)

sensory transduction

-the conversion of stimulus energy into a change in the membrane potential of a sensory receptor

-sensory receptor turns stimulus energy into electrical signal

general sense

widely distributed throughout the body

(Ex: touch, temperature, hunger)

special sense

any sensory system associated with a specific organ structure

(ex: smell, taste, sight, hearing, and balance)

CNS structures

brain and spinal cord

PNS function

-communication lines between the CNS and the rest of the body

-send info to brain, send commands to body

somatic division (PNS)

voluntary control of skeletal muscle

autonomic division (PNS)

involuntary control of glands and smooth muscle

two branches of autonomic nervous system?

sympathetic and parasympathetic

sympathetic nervous system

-the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations

-"fight or flight"

parasympathetic nervous system

-the division of the autonomic nervous system that calms the body, conserving its energy

-"rest and digest"

How does the CNS coordinate with the PNS to maintain homeostasis?

feedback loops