IU P225 Physiology Exam 2

g-protein pathway

starts with a ligand binding to a G protein-coupled receptor on the cell's surface

3 g-protein pathways

g-alpha s (stimulatory: cAMP)

g-alpha i (inhibitory: cAMP)

g-alpha q (stimulatory: PLC)

components of g-alpha s pathway

hammer = adenylate cyclase

key & ice = ATP

key = cAMP

lock = protein kinase A

components of g-alpha i pathway

hammer = adenylate cyclase

key&ice = ATP

key = cAMP

lock = protein kinase A

components of g-alpha q pathway

hammer = PLC

key&ice = PIP2

keys = DAG and IP3

locks = protein kinase C (DAG0 and calcium channel (IP3)

types of cholinergic receptors

nicotinic and muscarinic

nicotinic receptors

acetylcholine and nicotine neurotransmitters open ion channel doors

muscarinic receptors

acetylcholine and muscarinic neurotransmitters activate g-proteins

adrenergic receptors

activated by epinephrine and norepinephrine

beta receptors

activates g-a s

beta 1: heart & kindeys

beta 2: lungs & smooth muscle

beta 3: fat cells

alpha receptors

alpha 1: vascular smooth muscle (activates g-a q)

alpha 2: brain (activates g-a i)

g-alpha s pathway

- alpha subunit +GTP bind to adenylate cyclase

- AC converts ATP into cAMP

- cAMP activates PKA

g-alpha i pathway

- alpha subunit +GTP bind to adenylate cyclase

- AC is inhibited = less cAMP

- reduced activation of PKA

g-alpha q pathway

- alpha subunit + GTP bind to PLC

- PLC activates & converts PIP2 into DAG and IP3

- IP3 triggers calcium release

what is a reflex?

automatic involuntary response to a stimulus

what kind of neuron connects a sensory receptor to the CNS?

afferent

when does a sensory receptor stop receiving information?

NEVER

reflex arc

1. sensory receptor 2. afferent neuron 3. integration center 4. efferent neuron 5. effector organ

intrinsic reflex

innate, present from birth

learned reflex

acquired from time and experience

ipsilateral reflex

reflex occurs on same side as stimulus

contralateral reflex

reflex occurs on opposite side as stimulus

somatic reflex

skeletal muscle; movement

visceral reflex

internal organs; controlled by ANS

stretch reflex

occurs in response to muscle stretching; spindles sense muscle length - example: patellar knee reflex

golgi tendon reflex

occurs in response to high tension; GT organs sense tension - example: dropping heavy item

withdrawal reflex

moves body away from harmful stimulus; example: touching hot stove

cross-extensor reflex

extension of limb opposite of the stimulus; example: prevent falling after stepping on lego

normal SNS pathway

pre = short, myelinated acetylcholine to nicotinic receptor

post = long, unmyelinated, norepinephrine to adrenergic receptor

normal PNS pathway

pre = long, myelinated, acetylcholine to nicotinic receptor

post = short, unmyelinated, acetylcholine to muscarinic receptor

adrenal SNS pathway

pre = short, myelinated, acetylcholine to adrenal gland

post = adrenal gland, epinephrine into blood stream

sweating SNS pathway

pre = short, myelinated, acetylcholine to nicotinic receptor

post = long, unmyelinated, acetylcholine to muscarinic receptor

fastest acting ANS pathway

normal PNS due to long myelinated neuron

longest lasting ANS pathway

SNS due to longest post neuron

muscle spindle

afferent information to CNS (length, rate of change); activated by length increase

golgi tendon organ

senses tension/rate of tension change; activation leads to muscle relaxation

sensory receptor

detects info from internal and external environments; found in peripheral nervous system

sensation

input about physical world obtained by sensory receptors

perception

process of brain selecting, organizing & interpreting sensations

adaptation

decreases sensitivity to a stimulus; helps recognize new stimuli

transduction

conversion of energy from one form to another

photoreceptors

light waves (eye)

chemoreceptors

chemicals, gases & pH (blood vessels)

baroreceptors

stretch/pressure (blood vessels)

mechanoreceptors

physical changes (skin)

thermoreceptors

temperature (skin)

nociceptors

pain (everywhere)

tonic receptors

slow adapting - steady state of firing while activated - good for constant info

phasic receptors

rapidly adapting - fires when first signal received, stops at constant stimulus - good for detecting change

external ear

auricle: focuses sound into eardrum (separated from M.E. by tympanic membrane)

middle ear

malleus, incus, stapes: turns sound waves into vibrations (amplifies sound)

inner ear

cochlea: converts sound into electrical signals (separated from middle ear by windows)

pitch

determined by frequency of sound waves

volume (loudness)

determined by amplitude of sound waves

hair cells in inner ear

near base = short/stocky; knocked over by high frequency waves

near apex = long/floppy; knocked over by low frequency waves

3 main types of vision cells

photoreceptors, bipolar cells, ganglion cells

photoreceptors (vision)

rods and cones

bipolar cells

outer synaptic layer

ganglion cells

inner synaptic layer, joins with optic nerve

do photoreceptors release glutamate at resting potential? (-40mV)

yes

three types of cones

blue, red, green

how does the brain see specific colors?

it depends on the type of photoreceptor being activated; takes a combination of different cone activations (i.e 80% blue, 40% green)

light adaptation

going from dark to light; light overstimulates rods and cones (rods turn off, cones become desensitized) - leads to color vision & focus

dark adaptation

going from light to dark; cones turn off, rods bleached from light - rhodopsin regenerates and sensitivity increases over 30 minutes

dark

photoreceptors release glutamate (inhibits bipolar cells); no action potential so visual cortex has no stimulus

light

no glutamate release (bipolar cells get depolarized); increase glutamate in ganglion cells causes action potential

hormone

chemical messenger used to communicate in the endocrine system

endocrine system function

long distance communication via the use of hormones; controls and coordinates body functions

target cell

has receptors for and responds to a hormone

3 types of endocrine gland stimulation

humoral, hormonal, neural

humoral stimulation

changes in blood ion concentration

hormonal stimulation

signals from a hormone

neural stimulation

signals from the nervous system

differences between endocrine and nervous systems

endocrine = slower & long lasting, travels long distance

nervous = faster & short lasting, travels short distance

similarities between endocrine and nervous systems

both use feedback loops, respond to stimuli, use chemical messengers

hypothalamus

controls homeostatic functions by releasing producing and hormones; regulated blood pressure, temperature & water balance

anterior pituitary

produces and releases hormones; controlled and stimulated by the hypothalamus

posterior pituitary

stores and releases hormones produced by the hypothalamus (does NOT produce hormones!)

anterior pituitary hormones

prolactin, GH, TSH, ACTH, FSH, luteinizing hormone

posterior pituatary hormones

vasopressin (or ADH) and oxytocin

growth hormone

stimulus: GHRH

produced: anterior pituitary

target: bone, muscle, liver

effect: increase size/muscle

thyroid-stimulating hormone

stimulus: TRH

produced: A.P.

target: thyroid

effect: production of thyroid hormones

follicle-stimulating hormone

stimulus: GnRH

produced: A.P.

targets: ovaries & testes

effect: hair growth & spermatogenesis

luteinizing hormone

stimulus: GnRH

produced: A.P.

targets: ovaries & testes

effect: ovulation & testosterone

adrenocorticotropic hormone (ACTH)

stimulus: CRH

produced: A.P.

targets: adrenal cortex

effect: cortisol production

prolactin

stimulus: estrogen, suckling baby, low dopamine

produced: A.P.

target: mammary gland

effect: milk production

oxytocin

stimulus: stretched cervic, crying baby

produced: hypothalamus (P.P.)

targets: uterus, mammary glands

effect: contractions & milk release

vasopressin (ADH)

stimulus: high plasma osmolarity (sodium)

produced: hypothalamus (P.P.)

target: kidneys

effect: water reabsorption, vasoconstriction

thyroid hormone

stimulus: TSH

produced: thyroid

target: everywhere

effect: increased metabolism

parathyroid hormone

stimulus: low blood calcium

produced: parathyroid

target: bone, kidney, small intestine

effect: vitamin D, increase blood calcium

calcitonin

stimulus: high blood calcium

produced: thyroid gland

targets: bone cells, kidneys

effect: reduces blood calcium

insulin

stimulus: high blood sugar

produced: pancreas

targets: muscle, liver fat

effect: lower blood sugar

glucagon

stimulus: low blood sugar

produced: pancreas

target: liver

effect: increase blood glucose

cortisol

stimulus: secretion of ACTH, stress, low bs

produced: adrenal cortex

target: liver, fat, muscle

effect: increase blood sugar, suppress immune system

aldosterone

stimulus: low bp, high potassium, low sodium

produced: adrenal cortex

target: kidneys

effect: sodium reabsorption, potassium excretion, increased blood pressure

epinephrine

stimulus: stress, strong emotions

produced: adrenal medulla

target: heart, blood vessels, muscle cells

effect: increased heart rate, bp, metabolism

muscle cells

skeletal, cardiac, smooth; all produce force & movement

sarcolemma

plasma membrane of a muscle cell

sarcoplasm

cytoplasm of a muscle cell

t-tubules

extension of sarcolemma - deep into muscle cell