Human Physiology Study Guide Exam 2

Hormones

• are synthesized and stored in the cells of glands from which they arise

• secreted into the blood by a cell or group or cells

• exert their effects in low concentrations

• act by binding to receptors (mechanism of action)

• must be terminated (half-life)

  • degraded intracellularly, extracellularly, or by lysosomes

• active (Vesicle)

Factors

candidate hormones

• usually autocrine or paracrine (GFs) and/or hormone (CCK digestive/CNS)

Classification of Hormones

Three main chemical classes based on biomolecule type

• Peptide hormones

• Steroid hormones

• Amines

Peptide Hormones

synthesized by transcription/translation

• protein synthesis

made as large, inactive preprohormones that include a signal sequence, copies of the hormone, and additional peptide fragments

hydrophilic (can’t pass through the membrane - must combine with membrane receptor to initiate signal transduction processes)

Steroid Hormones

derived from cholesterol

• cholesterol metabolism

hydrophobic hormones (not stored in endocrine cell because of this - made on demand and move through blood via carrier proteins (albumin)) made in either the adrenal cortex or the gonads

Amines

derived from specific amino acids

• amino acid metabolism

important precursors: Tyrosine (Catecholamines or Thyroid Hormones) and Tryptophan

*important paths to memorize on slide

Preprohormone

inactive (RER)

• signal sequence + hormone + peptide fragments

Prohormone

inactive (Golgi)

• hormone + peptide fragment

ACTH

pituitary hormone that targets adrenal glands to release cortisol

TRH

thyrotropin releasing hormone that is found in the hypothalamus

y-lipotropin

targets melanocytes

b-endorphin

binds to u-copied receptor that is GABA inhibited and dopamine produced

C-peptide

makes blood flow more easily (helps insulin move through blood more effectively)

Gonads

where steroids are found

Androgens

• Dihydrotestosterone (DHT)

• Testosterone

• Androstenedione

• DHEA

Estrogens

• Estradiol

• Estrone

• Progesterone

Glucocorticoids

• Cortisol

• Corticosterone

Mineralicorticoids

• Aldosterone

Law of Mass Action

reaction rates are proportional to the concentration of the reactants

• increased ligands in the reactants = decreased equilibrium constant

• decreased ligands in the reactants = increased equilibrium constant

Resorption of Calcium

breakdown of bone moving calcium into the blood

Reabsorption of Calcium

calcium moved back into the blood

Absorption of Calcium

moved into the blood

3 Major Groups of Neurohormones

1. caltecholamines: DA, NE, E

2. hypothalmic releasing hormones: DA, TRH, CRH, GHRH, SST (GHIH), GnRH

3. posterior pituitary hormones (neural hormones): OXY, AVP (ADH)

Tropic

hormones that targets a gland that is going to relaase another hormone

Trophic

directs growth

Pituitary Gland

Two different tissue types

• Anterior pituitary (true endocrine gland - Adenohypophysis)

• Posterior pituitary (neural tissue - Neurohypophysis)

*study diagrams from both

Short-Loop Negative Feedback

pituitary hormone blocks hypothalamus

Long-Loop Negative Feedback

periphery hormone blocks both pituitary and hypothalamus from releasing hormones

Ultra Short-Loop Negative Feedback

• autocrine feedback - self-inhibit

• paracine feedback - inhibit itself and its neighbors

Hormonal Additive Effect

two hormones acting individually toward a response

Hormonal Synergetic Effect

two hormones converging on signal transduction pathway

Permissiveness

one hormone cannot fully exert its effects unless a second hormone is present

• ex. GnRH and sexual maturation

  • delayed sexual maturation (optimal output not reach without second hormone)

  • sexual maturation (optimal output reached when thyroid hormone is present)

Antagonistic Hormones

two hormones may work against each other, diminishing the effectiveness or the other

• ex. glucagon, growth hormone, and insulin

  • glucagon and growth - increase blood glucose levels

  • insulin - decrease blood glucose levels

hormones may not be competing for the same receptor

• antagonistic effect are likely through separate metabolic pathways

Endogenous Causes

tumors of the endocrine gland

Exogenous Causes

• iatrogenic (physician caused)

• hormone treatment

Primary Hypersecreation

adrenal cortex problem

• CRH levels - low

• ACTH levels - low

• Cortisol levels - high

Secondary Hypersecreation

pituitary problem

• CRH levels - low

• ACTH levels - high

• Cortisol levels - high

Tertiary Hypersecreation

hypothalamic problem (very rare)

• CRH levels - high

• ACTH levels - high

• Cortisol levels - high

Hyposecretion (Hypocortisolism)

• Hyposecretion from damage to the pituitary

  • Anterior pituitary = defective gland

    • Decreased ACTH and cortisol → symptoms of deficiency

• Hyposecretion from atrophy of the adrenal cortex

  • Adrenal Cortex = defective gland

    • Decreased cortisol → symptoms of deficiency

Receptor/Signal Transduction Abnormalities

• Receptors may be non-functional or absent

• genetic alteration somewhere in the signal transduction pathway

  • ex. pseudohypoparathyroidism - genetic alteration of g-protein *know pathway on slide

Receptor Downregulation

cells may downregulate their receptors to decrease their responsiveness to a hormone that is chronically in excess

Neurons

excitable cells with a unique shape and structure that allow them to communicate with other neurons and other cells

Synaptic Cleft

space between presynaptic and postsynaptic cells

Synapse

terminal of presynaptic cell meets postsynaptic cells (target cells)

• region of communication

Node of Ranvier

keeps current moving through the cell (neuron)

Axon Hillock

change in channel gating types

• ligand-gated channels → voltage-gated channels

Integration

sum of all information coming in

Neurite

general term for projection coming out of the neuron

Arborization

dendrite branching

Sensory Neurons

• Unipolar

• Pseudo-polar - somatic sense (Schwann cell)

• Bipolar - neurons for smell, vision, audition

Interneuron of CNS

lots of dendrite branching and very integrated (lot of information telling you where everything is)

• Anaxonic

• Mutipolar

Efferent Neurons

Most typically found branching out to skeletal muscles

• Multipolar

Fast Axonal Transport and Slow Axonal Transport

• Fast: moves vesicles and mitochondria

• Slow: moves soluble proteins and cytoskeleton fibers

Anterograde

soma → terminal

Retrograde

terminal → soma

Ependymal Cells

• found in CNS

• line the ventricles (barrier between ECF and CSF)

  • ex. choroid plexus: help produce CSF using materials from blood

Astrocytes

• found in CNS

• maintain ionic environment, neurotransmitter uptake (metabolize them to get rid of them from synapse after function is performed), inhibit apoptosis process, interact with capillaries (sends signals to cells to a make a tight junction used to block paracellular transport), can impede injury recovery

Radial Glia

guide neurons to their synapses and then differientiate into astrocytes

Microglia

• modified macrophages found in CNS (develop hematopietic and migrate to CNS)

• when activated - act as phagocytes

Oligodendrocytes

• found in CNS

• one can myelinate multiple axons of different cells, can impede injury recovery

  • increases conduction velocity (faster electrical signal)

Schwann Cells

• found in PNS

• can not myelinate multiple axons (one cells → one axon), allows for growth and repair (helps repair injuries)

Satellite Cells

• found in PNS

• kind of like peripheral astrocytes

  • maintaining ionic environment, neurotransmitter uptake

Graded Potentials

• loss strength due to

  • current leak (rm)

  • cytoplasmic resistance (ri)

• associated with ligand-gated channels

• neuronal code = amplitude

• subthreshold

Action Potential

• associated with voltage-gated channels

• neuronal code = frequency

• suprathreshold (graded potential that leads to an action potential)

Action Potential Positive Feedback Loop

• Na+ entry during an action potential creates a positive feedback loop

• Stopping the positive feedback loop

  • increased permeability to K+

  • *Na+ channel inactivation gates (very important)

Absolute Refractory Period

cannot have another action potential

Relative Refractory Period

another action potential is possible but requires strong stimulus strength and the amplitude of the action potential is weaker

• some channels closed, some not, some in process of

Axon Conduction

• unidirectional signaling caused by inactive period

• continuous entry of Na+ along the axon as Na+ channels open creates an electrical signal remains constant over distance

Conduction Velocity

2 key parameters that determine the speed at which an action potential can move

• axon diameter

  • decreased diameter → increased ri → decreased conduction velocity

  • increased diameter → decreased ri → increased conduction velocity

• myelination

  • no myelination → decreased rm → decreased conduction velocity

  • myelination → increased rm → increased conduction velocity

Saltatory Conduction

the action potentials appear to jump from one node of Ranvier to the next

*study diagram on page

Divergence

single cell influences a host of paths/circuits

• forms a lot of collaterals (branching)

Convergence

host of integration

• output of the sum of information coming in

Slow v. Fast Postsynaptic Responses

• Iontropic paths “fast” - mediated by ion channels

  • depolarization = EPSP (exictatory)

  • hyperpolarization = IPSP (inhibitory)

• Metabotropic paths “slow” - mediated by G-protein coupled receptors

  • alpha subunit activates AC = EPSP (Gs)

  • alpha subunit inhibits AC - IPSP (Gi)

  • IP3/DAG (Gq)

Spatial Summation

signals converge on the same postsynpatic neuron

Temporal Summation

single presynaptic neuron fires rapidly in succession

Global Presynaptic Inhibition

affects all targets

Selective Presynaptic Inhibition

specific collateral circuit is affected

Dual Antagonistic Control

one autonomic branch in excitatory and the other is inhibitory

• both are capable of exciting or inhibiting but must be antagonistic

exception: sex organs - parasympathetic and sympathetic systems work cooperatively

Neuromuscular Junction

consists of axon terminals, motor end plates on the muscle membrane, and Schwann cell sheaths

Motor End Plate

region of muscle membrane that contains high concentrations of ACh receptors

Equilibrium v. Reversal Potential

Both influx = efflux

• Erev occurs with two ions are moving through a channel

• Eion - only one ion moving through the channel

Adrenal Cortex

true endocrine gland

Adrenal Medulla

modified sympathetic ganglion

Three Muscle Types

• Skeletal - striated, multinucleate, voluntary control

• Cardiac - striated, uninucleate (usually), involuntary control

• Smooth - smooth, uninucleate, involuntary control

H-zone

only thick filament

A-band

length of thick filament (includes overlap with thin filament)

I-band

only thin filament

Z-disk

protein that binds think filament

M-line

thin verticle line in exact middle of a sacromere that hold thick myosin filaments together

Sacromere

spans z-disk to z-disk

Troporin

important calcium binding protein intermediate found along tropomyosin

Nebulin

stiff rod, inflexible

• not found in smooth muscle cells

G-actin molecule

bulk protein (type of actin that has binding site for myosin)

Myosin Head

has a binding site for actin and is an enzyme (ATPase)

Myosin Tail

elongated to create distance from the m-line (ensures myosin heads are not near the m-line)

Sliding Filament Theory

myosin heads interact with thin filament and slide them (slide not shorten)

• violated by Titin (large, flexible protein)

Rigor State

muscle contraction is done and this is where we end up

Relaxed State

mysoin head is rotated to cocked position

• self-phosphorylating

• weakly bound to actin (tropomyosin prevents strong bound between myosin and actin)

Power Stroke

contraction state caused by dephosphorylation (loss of phosphate affinity)

• triggered by calcium binding to troporin

ST Type I

• slow twitch = slow to fatigue

• increased mitochondria, increased blood vessels, increased myoglobin, decreased diameter