Homeostasis in Animals

Thyroid/parathyroid

Thyroid/parathyroid

metabolic processes

Adrenal

fight or flight; stress response

Pineal

biological rhythms

Hypothalamus

control of posterior pituitary gland

Posterior Pituitary

- Reproductive physiology
- Kidney function
- Neurosecretory cells from the hypothalamus project directly into the posterior pituitary gland (like an extension of the brain).
- Doesn't release its own hormones.
- Releases hormones directly into the blood stream when stimulated.

Anterior Pituitary

- Reproductive physiology
- Adrenal function
- Growth
- Different neurosecretory cells release "releasing factor" hormones into small blood vessels that go to the anterior pituitary.
- Releasing factors trigger the release of hormones from a/p endocrine cells into blood vessels that travel to the body.
- Produce its own hormones in response to signals from the brain.

Pancreas

Digestion; glucose metabolism

Gonads (testes/ovaries)

secondary sex characters; reproductive physiology and behavior

Signal transduction

the transmission of molecular signals from a cell's exterior to its interior

Hormone effects are modulated by:

- Tissues (receptors needed)
- Age or development stage (receptor only present at certain ages)
- Season (breeding or migratory periods)
- Presence of other hormones (pregnancy, diet, stress, etc.)
- Gene regulation (hormone synthesis shut down or activated)

Close connection between the nervous system and the endocrine system

The nervous system can stimulate the release of hormones, and the release of hormones can affect nerve signal production.

***Adrenalin can act as a hormone and as a neurotransmitter.

Simple endocrine pathway

endocrine cells respond directly to an internal or environmental stimulus by secreting a particular hormone

Simple neuroendocrine pathway

Stimulus received by the sensory neuron which stimulates the neurosecretory cell to secrete a neurohormone.

Negative feedback

a mechanism of response in which a stimulus initiates reactions that reduce the stimulus/hormone production.
Ex) cruise control, any kind of regulation.

Positive feedback

a mechanism of response in which a stimulus causes a response that increases the stimulus and hormone production.
Ex) Audio feedback, panic in crowds, viral internet items. Ovulation, lactation, blood clotting, and fruit ripening.

Passive transport

the movement of substances across a cell membrane without the use of energy by the cell. Direct (through membrane) and facilitated (channels or carriers). With the concentration gradient

Active transport

Energy-requiring process that moves material across a cell membrane against a concentration gradient. Pumps and cotransporters (symporter and antiporter).

Osmoregulation

regulation of solute concentrations and water balance

Osmoconformers

organisms that have an internal concentration of water and solutes that closely match that of the environment

Osmoregulators

organisms that maintain solute environments in their bodies that are different from the surrounding medium

Hypertonic (hyperosmotic)

higher concentration of solute

Hypotonic (hypo-osmotic)

lower concentration of solute

Osmolarity

measure of total concentration of solute particles

Seawater Fish Osmoregulation

fish bodies are hypotonic relative to seawater (their bodies have less solutes than the water), so the solute potential is higher in the fish. The fish is always losing water to the environment, so it has to drink a lot and pee very little.

Freshwater Fish Osmoregulation

Fish bodies are hypertonic relative to freshwater (their bodies have more solutes than their environment), so the solute potential is lower in the fish. They drink very little, but pee constantly.

Chloride cells

Found in gills, can help marine, freshwater, and euryhaline fishes osmoregulate.

Saltwater: can burn ATP using Na+/K+ pumps to move salt out.
Freshwater: moves salt into fish

Seabass, salmon, and bull sharks can switch from freshwater to salt water by reversing these cells.

What would happen to marine fish transplanted to freshwater?

die by "drowning", water would rush into the fish

What would happen to freshwater fish transplanted to sea water?

die by "thirst", water would rush out of the fish

Salt glands

a gland that secretes excess salts in seabirds and sea turtles

Nitrogenous waste

Excretion of waste from the bloodstream, comes from the breakdown of substances that contain nitrogen (proteins), can be very toxic.

Ammonia

- nitrogenous waste in marine animals* (fish).
- most toxic
- very soluble
- needs lots of H2O
- easiest to produce

*Aquatic animals have lots of water around, which is why ammonia is the main source of nitrogenous waste

Urea

- nitrogenous waste in mammals, most amphibians, sharks, and some bony fish.

- less toxic

- needs less H2O

- harder to produce

Uric Acid

- nitrogenous waste in birds, reptiles, insects, and land snails*.
- least toxic
- least soluble
- needs the least amount of H2O
- very hard to produce

*Animals that lay eggs

Fundamental Problem in terrestrial animals and the Basic Strategy

Problem: They need to excrete metabolic wastes without losing too much water.

Strategy: Pump everything into one place and then selectively reabsorb the things you want.

Malpighian tubules

The excretory organs of insects and other terrestrial arthropods that function like the mammalian kidney. Pumps everything into one space and then reabsorbs the nutrients that it wants.

K+ gets pumped into the tubules, which causes water to diffuse in = pre-urine. The pre-urine goes into the digestive tract and those cells take back what they want. This takes a lot of energy.

Anatomy of the human urinary system and kidney

Anatomy of the Kidney

Renal cortex

outer layer of the kidney

Renal medulla

inner region of the kidney

Renal artery

carries blood to the kidney

Renal vein

blood vessel that carries blood away from the kidney

Nephron

functional unit of the kidney

Distal tubule

Between the loop of Henle and the collecting duct; Selective reabsorption and secretion occur here, most notably to regulate reabsorption of water and sodium.

Proximal tubule

The portion of a nephron immediately downstream from Bowman's capsule that conveys and helps refine filtrate.

Loop of Henle

section of the nephron tubule that conserves water and minimizes the volume of urine

Renal corpuscle

glomerulus and bowman's capsule

Bowman's capsule

cup-shaped structure of the nephron of a kidney which encloses the glomerulus and which filtration takes place.

Glomerulus

small network of capillaries encased in the upper end of a nephron; where the filtration of blood takes place

Vasa recta

A network of blood vessels from the glomerulus that collects the good stuff coming from the Loop of Henle. It leads to the main vein and back to the heart. Flows in the opposite direction of the Loop of Henle (counter-current). Prevents the tissues around the nephron from reaching equilibrium.

Urine production begins in the __________.

Renal corpuscle: Glomerulus and Bowman's capsule.

**Requires a lot of energy

Reabsorption begins in the _______.

Proximal tubule: the infoldings into the villi increase the surface area available for reabsorption, the blood also just came from the glomerulus which is why it is low in solutes.

**Even after the proximal tubule, there is still water and ions that you want to recover and keep, so you need to get them out of the tubule/Loop of Henle.

Descending limb

permeable to water, but not ions: water can leave, but ions stay.

Thin ascending limb

permeable to ions, but not water. The ions released stay in the tissues because the body wants them.

Thick ascending limb

permeable to ions, but not water. Na+/K+ pumps are located here to ensure that water does not enter back into the loop, and takes over the previously passive movement of ions.

Counter current exchange

efficient transfer of property or substance from one fluid to another through a "permeable" membrane or barrier.
Ex) fish gills, placenta, AC units

Function of the kidney

filters blood

Why does the water leaving the descending limb of the Loop of Henle not flow back in?

The water does not flow back into the loop because it is flowing in a direction of high solute concentration, therefore it is also passive movement.

Why do the ions in the ascending limb of the Loop of Henle not flow back in?

The ions do not flow back into the loop because the concentration of ions is so high inside. They want to get out and move to an area of lower concentration. This is passive ion movement.

**NOTE: sodium/potassium pumps are located in the thick ascending limb to keep the flow of ions moving out, even though the concentration is lower inside the loop. This is where active ion movement has to take over.

Similarity between the thick ascending limb and the rectal gland in sharks is ______.

The rectal gland in sharks removes the excess salt, while the thick ascending limb takes back salt. They are reverse processes.

Collecting duct

A segment of the nephron that returns water from the filtrate to the bloodstream. Allows a small amount of urea through to the tissues to keep the concentration gradients strong.

End result for the fluid in the descending limb

Fluid in descending limb encounters steadily increasing osmolarity of surrounding tissue = water wants to leave

End result for the fluid in the ascending limb.

Fluid in ascending limb continually loses solutes to surrounding tissue thus maintaining the concentration gradient.

Aldosterone

Hormones found in the nephron that come from the adrenal gland. It takes sodium from the distal tubule.

ADH hormone

(posterior pituitary): recovers water.

When ADH is present, the collecting duct will be highly permeable to water and urea, which will strengthen the concentration gradient around the descending Loop of Henle. More water will be recovered from the loop.

Caffeine and alcohol will shut down the ADH hormone = having to pee a lot = lots of water lost

Would the nephron work if it did not pass through the inner medula?

It would not work because it needs to encounter the high salt concentrations found there.

If an animal needs to conserve more water its Loop of Henle will be _____.

longer

Why is a curved Loop of Henle more efficient at removing water from forming urine than a straight tube?

The curve allows the nephron to use a countercurrent exchange to remove water from the loop.

Basic form of gas exchange and circulation

1. Ventilation
2. Diffusion
3. Circulation
4. Diffusion
5. Cellular Respiration

Open circulatory system

A circulatory system that allows the blood to flow out of the blood vessels and into various body cavities so that the cells are in direct contact with the blood.

Closed circulatory system

A circulatory system in which the oxygen-carrying blood cells never leave the blood vessels.

Single circulation: fish

Blood from the gills goes through the body and then to the heart. Less oxygen efficient. Only goes through the heart once.

Double circulation: amphibians

3 chambers: two atria and one ventricle. Blood pumps through the heart twice. The ventricle is not quite divided, so some of the oxygenated blood gets mixed with the deoxygenated blood and goes back to the lungs and heart. Pulmocutaneous.

Double circulation: mammals

4 chambers: two atriums and two ventricles. Separates oxygenated blood and deoxygenated blood because the ventricle is completely divided in two. Goes through the heart twice. Pulmonary.

Artery

carries blood away from the heart

Vein

Blood vessel carrying blood towards the heart. Thinner, less muscular, lower pressure, connective layers allow for elastic recoil, and muscle layers allow for regulation of blood pressure and pattern of flow.

Generalized blood flow in mammalian hearts

Diastole phase

When the heart relaxes to fill with blood

Systole phase

phase in the cardiac cycle in which the ventricles contract

Are the atrial and ventricular systole in or out of sync?

out of sync

Which way is the contraction pattern in the heart?

Top to bottom, not left to right. Atria to Ventricles

In evolutionary transitions from fishes to amphibians to mammals, a key pattern in circulatory architecture has been:

separating pulmonary flow from systemic flow.

AV valve function

prevent back flow into atria when ventricles contract

Semilunar valve function

prevent backflow into the ventricles from primary arteries

Respiration in fish

Counter-current exchange makes gas exchange easy. Water flows from the mouth to the gills. Blood flows in the opposite direction of water, so they are never at equilibrium.

Respiration in terrestrial animals

Tracheal system. Oxygen goes straight to the muscles. There is a film of liquid inside alveoli that gases must diffuse through for normal function.

Respirational mucle contraction in mammals

Muscle contraction required to inhale (more efficient than requiring muscle contraction to exhale against force of atmospheric pressure).
Disadvantage: brief period of no/low oxygen gas in bidirectional lungs.

Double respiratory system in birds

Homeostatic control of ventilation

Automatic control: Pons and Medulla are the breathing control centers.

Two ventilation issues with activity increase

1. Loss of oxygen
2. Gain of carbon dioxide (drop in pH)

Hemoglobin

Binds four oxygen molecules and then moves them around the body through the blood stream.

Cooperative binding

When one oxygen binding site in hemoglobin gets filled, the other sites strongly attract more oxygen.

Oxygen-hemoglobin equilibrium curve, oxygen dissociation curve, hemoglobin saturation curve, oxygen saturation curve

Shape of the curve results from cooperative binding

Ventilation rate in a vertebrate is primarily affected by:

bloop pH

Transport of oxygen and carbon dioxide in the blood

Two major effects:
1. Conversion to bicarbonate and binding to hemoglobin maintains diffusion gradient for CO2.
2. Free H+ lowers pH near hemoglobin, which affects the saturation curve.

Bohr shift

A lowering of the affinity of hemoglobin for oxygen, caused by a drop in pH; facilitates the release of oxygen from hemoglobin in the vicinity of active tissues.

Percent saturation

percent of binding sites that are bound to oxygen

Cooperative unbinding

When one oxygen pops off the hemoglobin, the other ones readily follow suit.

Which way will the Bohr Shift go when pH is lowered?

The curve will shift to the right. If pH is increased, the curve will shift to the left (picture).

Dendrite

Branchlike parts of a neuron that are specialized to receive information/stimuli

Axon hillock

Cone-shaped region of an axon where it joins the cell body.