Behavioral Neuro - Ch 13

Feeding

Why do we eat and drink?

Internal and external (sensory) experiences drive feeding behaviors to restore balance

How do you determine if you need food?

homeostasis (balance between the internal and external environments)

• glucose levels, proteins, fats, salts, water, etc.

How do you determine if you want food?

incentive motivation

• flavors, reward, hedonic tone, etc.

Describe homeostasis

• maintaining the “set point”

• monitors physiological mechanisms

  • blood glucose, body fat, salt levels, etc.

What happens homeostasis is in a deficient?

stimulate seeking/feeding

• a little hungry after you come home from class

• hungry after a swim practice

• extremely hungry/starving if you get lost while hiking

What happens homeostasis is in a surplus?

suppress seeking/feeding

• negative feedback regulation of feeding

  • deviation from the set point leads to compensation to return to set point

Define redundancies

multiple mechanisms of maintaining homeostasis that work at the same time

Define endotherms

• species that produce their own heat through metabolic processes

• metabolism and muscles

  • greater muscle activity through increased use of oxygen

What does the pre-optic area (POA) do?

Organizes thermoregular responses and sends information to other brain regions.

What do we do if we’re cold?

• shiver to produce heat

• increase metabolism to generate heat/energy

• reduce sweat

• decrease blood flow to reduce heat loss

• increase respiration

• can also change behavior

• redundancies makes it more complicated!

What is an example of homeostasis?

fluid regulation

Define osmolality

number of particles (salts) per unit volume of water

• isotonic

• hypertonic

• hypotonic

Describe an isotonic salt solution

• 0.9% NaCl

  • 0.9 grams of NaCl in 100 milliliters of water

Define hypertonic solution

more salty than an isotonic solution

Define hypotonic solution

less salty than an isotonic solution

What is a 0.5% NaCl solution?

hypotonic

Define aquaporins

• specialized channels for H2O

• H2O moves based on concentrations within or outside the cell

Define the intracellular compartment

Within cells

Define the extracellular compartment

Outside of cell (includes fluid between cells [interstitial fluid] and blood plasma [protein rich])

Describe osmotic thirst

• high salt concentration in extracellular compartment

  • regular water loss (respiration, perspiration, urine)

  • eat something salty

• water flows out of cells

  • H2O flows out of cell into [NaCl] area

Where are osmosensory neurons located?

hypothalamus

Describe osmosensory neurons

• located in the hypothalamus

• cell changes size based on osmolarity and water pressure

What occurs when there is too much salt outside of a osmosensory neuron?

• cell shrinks

• ion channel open

• action potential triggers the pre-optic area

• triggers osmotic thirst response

• vasopressin release

Is vasopressin released when an osmosensory neuron shrinks or swells?

when it shrinks

What does vasopressin release do?

reduces urination

What is partnered with an osmotic thirst response?

vasopressin release

Describe hypovolemic thirst

too little volume of extracellular fluid

• large water loss (vomiting, hemorrhage, diarrhea)

• lose water AND salts so no change in osmolarity/concentration of salt within the cells

What flows out of cells in osmotic thirst?

water only (causing a high salt concentration in the extracellular compartment)

What flows out of cells in hypovolemic thirst?

water and salts (causing NO change of osmolarity in the extracellular compartment)

What is the different cravings between osmotic and hypovolemic thirst?

• osmotic = crave water

• hypovolemic = crave water AND salt

What do the baroreceptors in the blood vessels/heart do in