BILD2 exam 3

What does the efferent nervous system consist of?

Autonomic Nervous System and Somatic Motor System

Which system controls involuntary, subconscious movement of glands and smooth muscle organs

autonomic nervous system

which system controls mostly voluntary movement of skeletal muscles?

somatic motor system

what is the skeletal muscle hierarchy?

muscle, muscle fiber bundles, single muscle fiber, myofibril, sarcomeres, actin and myosin

What are the three stages of muscle contraction?

1) activation at neuromuscular junction

2)signal propagation

3)cross-bridge cycling

What happens during the first stage of contraction?

Activation at the neuromuscular junction:

\-action potential propagates through the motor neuron into the presynaptic terminal

\-depolarization triggers VG ca2+ channels to open

\-influx of Ca2+ signals synaptic vesicles to move closing the membrane and release nt Ach acetylcholine

\-ACh will bind to the receptor on the postsynaptic neuron

\-Na+ can enter the cell, depolarize the cell, and generate a muscle action potential

What happens during the second stage of contraction?

Signal propagation:

\-muscle action potential propagates through the muscle fiber

\-signals the sarcoplasmic reticulum to release Ca2+

what happens during the last stage of contraction?

cross-bridge cycling

\-binding of Ca2+ to troponin removes tropomyosin from actin

\-actin and myosin heads slide past each other and create movement and contraction

\-requires ATP and Ca2+ because ATP is hydrolyzed to ADP and Pi, myosin heads release ADP and Pi,

\-sarcomere shortens and muscles contract

do actin filaments change in length from contraction?

no, actin and myosin filaments do not change in length because they only move and slide to overlap, but the sarcomeres do shorten because they consist of the both actin and myosin

What are the main functions of the kidneys?

1. filtration: pushing/moving of water and small molecules from blood into renal tubule (forming filtrate)
2. reabsorption: reabsorb useful molecules and water back into the blood
3. secretion: removal of toxins and waste from the blood and filtrate
4. excretion: moving the final filtrate (urine) to the bladder and excretion from the body through urination

Where does each function/step of the kidney take place?

filtration: Bowman’s capsule

reabsorption: proximal tubule, descending and ascending limb (loop of Henle), distal tubule, collecting duct

secretion: proximal tubule, distal tubule, and collecting duct

excretion: bladdar

What happens in Bowman’s Capsule?

filtration-massive loading of “filtrate” from blood to renal tubule, bp forces fluid movement, glomerulus are porous, small molecules (water, ions, sugar,) move from blood renal tubule by blood pressure to bowman’s capsule, blood cells and proteins stay in blood

What occurs in the proximal tubule?

reabsorption and secretion- via active transport and diffusion

active transport: ions and glucose

diffusion: water

the main function is reabsorption (about1 100% nutrient reabsorbed)

what is osmolarity?

the concentration of particles dissolved in a fluid

how is osmolarity and water concentration related?

higher osmolarity means lower water concentration

lower osmolarity means higher water concentration

What occurs in the descending limb of the loop of Henle?

water is reabsorbed, driven by differences in osmolarity via passive transport

what happens in the ascending limb of the loop of Henle?

ions are reabsorbed driven by difference in osmolarity and energy input via active and passive transport for NaCl

reabsorption in loop of Henle occurs due to __*____*__ and ___

increased/gradiented osmolarity in renal medulla, selective permeability of the renal tubule

what occurs in the distal tubule and collecting duct?

reabsorption in distal tubule and collecting duct depends on hydration levels

how is osmolarity homeostatically regulated?

hypothalamus--→via release of ADH for water reabsorption or neurons of hypothalamus generate thirst--→normal blood osmolarity (25-295 m)sm/L)--→ blood osmolarity increases

how does the kidney regulate body’s pH levels?

more HCO3- reabsorption from filtrate increase the pH, less HCO3- reabsorption from filtrate decreases pH (CO2+H2O <==> H2CO3 <==> HCO3-+H+)

what are the functional units of the kidney that carries out the the steps of urine production?

nephrons

What challenges do plants face?

\-plants cannot move but they still need nutrients/CO2, removal of waste and to maintain a healthy stable environment

\-growth depends on the local environment conditions like (temperature, sunlight, water level, nutrient level, pathogenic attack)

How do they cope with challenges?

they alter their growth and development in response to the environment rather than moving which animals do

How do plants respond to the environment?

1. input- receiving information from the environment through a receptor (ie. hormones, light, etc)
2. signal transduction-signaling molecules (such as relay proteins and secondary messengers) activate and relay signals to other signaling molecules
3. response-signal reaches final molecule that activates a response

how do plants breathe?

via stomata which are surrounded by guard cells

what are the characteristics of a hormone?

\-produced in low concentration in a specific part of the organism (nonspecific in plants)

\-transported to other parts and bind to specific receptors

\-trigger responses in the target cell/tissue

do plants have specific or no specific hormone producing organ?

no specific

how are hormones important to plants?

in plant adaptability to the environment

how do plants transport hormones?

via xylem, phloem, and in between cells

How could water be lost in plants?

through transpiration if the environment is too dry

What is produced in plants when the environment is too dry? what does it do?

ABA, Abscisic acid, prevents water loss since it closes the stomata

What stimulates the ripening of fruits and vegetables? What does it do?

Ethylene is gaseous and spreads through the air (can affect neighboring fruits) via positive feedback

ethelyene production is inhibited by CO2

what is involved in the elongation and growth of cells? where does it occur?

auxin and it occurs in environments where there is light

what are hormones?

signaling molecules that is produced at low concentrations by one part of an organism’s body and is transported to other parts where it binds to a specific receptor to trigger a response in target cells and tissues

\
Explain how a signal transduction pathway would look like in a plant that is \n closing its stomata

The plant cell identifies ABA with a receptor, starting transduction, and ending \n with the activation of a molecule that closes the stomat

Explain how a plant’s growth would be affected by the lack of phytochrome

The plant would not be able to respond to light meaning there would be no \n de-elotiation

Why might fruit producers expose their fruits to excess carbon dioxide before \n they transport their produce long distances?

To ensure their fruits do not ripen too early; CO2 inhibits the production of \n ethylene, extending their shelf life

What does the endocrine system do?

coordinates gradual changes which affects the entire body (ex. growth, digestion, reproduction) when endocrine glands secrete hormones into bodily fluids

what are the types of hormone signaling?

\-endocrine: endocrine cells release hormones--→ hormones travel long distances through bloodstream --→ bind to far-away target cells

\-paracrine: endocrine cells release hormones --→ bind to neighboring target cells

\-autocrine: endocrine cells release hormones --→ bind to receptors on the same cell

neuroendocrine: neurons release neurohormones --→ nuerohormones travel long distance through bloodstream --→ bind to far-away target

true or false hormones cause different effects depending on the type of receptor, the target cell, the different signal transduction pathways

true

what is a fight or flight response?

body will release hormone epinephrine to raise blood sugar, increase reactivity of skeletal muscles, and downregulate digestive system

true or false cells can use the same receptor but have different signal transduction pathways?

true

true or false cells have the same receptors?

false they have different receptors

what are the two classes of hormones?

1. water-soluble: polypeptides are the majority of all hormones in the body, amines
2. lipid-soluble: steroid hormones, amines

what are examples of water-soluble hormones?

insulin, glucagon, ADH, FSH, LH, epinephrine (amines)

what are some examples of lipid-soluble hormones?

cortisol, estradiol (estrogen), testosterone, progesterone, “look for -ol or one\*, thyroid

whats the difference between water and lipid soluble hormone signaling?

\-water-soluble hormones have receptor proteins only on the plasma membrane of their target cells this is because they cannot pass the lipid bilayer of the plasma membrane

\-lipid-soluble hormones can have receptor proteins in the cytoplasm or in the nucleus of their target cells because they can easily pass through the lipid bilayer of the plasma membrane

which type of hormone requires a transport protein when traveling through the bloodstream because it is a water-based environment?

lipid soluble

what does the hypothalamus do?

receives information from brain and responds by secreting hormones

what does pituitary gland do?

receives signals from hypothalamus and secretes hormones

what are the two different pituitaries and their functions?

posterior pituitary: stores and secretes the __same__ hormones made in hypothalamus (made up of same cells)

anterior pituitary: makes and releases __different__ hormones in response to hypothalamic hormone signals, secreted hormones often target another endocrine gland

what is an example of a hormone from the posterior pituitary?

ADH for more water retention

what is an example of a hormone from the anterior pituitary?

FSH and LH bind to receptors in the testes or ovaries (endocrine glands) causing the release of sex hormones which will stimulate a response

what are the two different thyroid hormones?

T3 and T4

what are the thyroid hormones functions?

\-essential for growth and development in children and infants, not essential in adult life

\-increases metabolic rate (how much energy is used at rest) by stimulating oxidative metabolism

\-contains iodine and require sufficient amounts in order to be synthesized

what can cause low levels of thyroid hormones? what else can it result in (symptoms)?

iodine deficiency, results in low metabolic rate- feeling cold, physical and mental lethargy, weight gain, swelling of thyroid gland

what is the thyroid hormone cascade?

1\. Hypothalamus senses low levels of T3/T4 \n 2. Neurosecretory cells of hypothalamus secrete TRH into blood vessels going to anterior pituitary \n 3. TRH binds to receptors in anterior pituitary causing AP cells to secrete TSH \n 4. TSH binds to receptors in the thyroid gland causing the release of T3 and T4 Negative feedback occurs on multiple levels when T3/T4 bind receptors on AP and hypothalamus