Homeostasis

Question 1

What is an Action Potential?

Answer 1

An electrical signal created when ions move between the outside and inside of the axon. A chemical message is sent to neighbouring neurons when an action potential occurs.

Question 2

Steps in an Action Potential

Answer 2

Step One: Reaching the Threshold
At resting potential, the fluid inside of the axon is mostly negatively charged, proteins and chloride ions, while the fluid outside the axon is mostly positively charged, sodium.
An impulse is triggered in the dendrites of a neuron when stimulated by pressure, heat, light, or a chemical messenger from another neuron.
The threshold stimulus is the minimal level of stimulation that causes an action potential.

Step Two: Action Potential Begins
Gates in the axon called voltage-gated sodium ion channels, open, allowing sodium ions to enter the cell while potassium leaves. This gives the cell a transient (quick) positive charge.
The positive charge is the action potential.

Step Three: Refractory Period
The sodium gates close. The sodium-potassium pumps three sodium ions out of the axon and returns two potassium ions to the axon.
The axon ends up temporarily hyperpolarized until the cell returns to resting potential.
The whole process of firing an action potential takes between three and five milliseconds.

Question 3

Why is The Neuron a “Club”?

Answer 3

Only some things can get in; potassium and chloride are always on the list. Potassium can come and go, but they prefer to be inside, away from sodium.
Some sodium can get in, but the sodium-potassium pumps remove them as quickly as they get in.
Sometimes sodium gets in and distracts the cell, so a bunch of sodium can come in, causing depolarization. When this happens, the sodium-potassium pumps spring into action and clear sodium out, which is repolarization.
The cell kicks ions, mistaking them for sodium, out of the club, apologizes, and lets them back in, like in the refractory period and returning to resting potential.

Question 4

I can explain the interactions of the hypothalamus, pituitary and collecting ducts that support water balance in the body.

Answer 4

Hypothalamus- The hypothalamus has osmoreceptors. When there is a lack of water in the blood, they shrink. This stimulates the secretion of anti-diuretic hormone from the posterior pituitary gland.
Pituitary Gland- The pituitary glands secrete anti-diuretic hormones. They travel to the kidneys, then to the collecting ducts, through the blood via the circulatory system.
Collecting Ducts- The collecting ducts are notified through the anti-diuretic that to conserve water. This makes it more permeable to water. Making water leave the collecting duct, thus being reabsorbed by the body and continue to be used.
Thirst Center- The thirst center is also notified as this process cannot continue forever as you would die; this tells you that you are thirsty. A drink increases blood volume, decreases blood osmolarity, and swells the osmoreceptors.

Question 5

I can distinguish between protein and steroid hormones and give examples of each.

Answer 5

Steroid hormones are fat soluble and have a base of cholesterol (fat).
Steps: Transports through the blood.Goes into the cell membrane. Hormones bind to more receptors. Travels into the nucleus and transcribes for mRNA. Diffuses out into the cytoplasm to make new proteins.
- Sex hormones

Protein hormones are water soluble only and have a base of amino acids. They cannot diffuse across the cell membrane.
Steps: Receptors are integrated into the cell membrane. Intermediate molecules in the cytoplasm interact with our receptors. Transfer information to the nucleus.
- Insulin

Question 6

I can explain how the HPT axis and HPA axis are used to regulate the body’s long-term response to changes in temperature and stress.

Answer 6

The HT axis stands for the hypothalamus, pituitary, and thyroid glands. It responds when your metabolic rate decreases. It is like a game of telephone.
Hypothalamus- Releases thyroid-releasing hormone. (TRH)
Pituitary Gland- Releases thyroid-stimulating hormone. (TSH)
Thyroid Gland- Releases T4 and T3 hormones. This triggers the end of the cycle with inhibition. This is a negative feedback loop; the release of this hormone triggers the stop, or inhibition, of TRH.
The HPA axis stands for the hypothalamus, pituitary, and adrenal glands. It responds to long-term stress.
Hypothalamus- Release corticotropin-releasing hormone. (CRH)
Pituitary Glands- Releases adrenocorticotropin hormone. (ACTH)
Adrenal Glands- Releases cortisol. (Stress Hormone) This trigger the end of the cycle with inhibition. This is a negative feedback loop; the release of this hormone triggers the stop, or inhibition, of CRH.

Question 7

I can explain how information is communicated from one nerve cell to another.

Answer 7

Step One: The action potential reaches the axon terminal of the sending neuron causing Ca to flow into the cytosol of the sending cell through the Ca channels.
Step Two: Ca ions entering the cell trigger vesicles to fuse with the membrane dumping NTs into the synaptic cleft.
Step Three: NTs find and attach to ligand-gated channels on the membrane of the receiving cell, triggering a response within that cell.
Step Four: NTs re-enter the sending cell, and an action potential may be triggered in the receiving cell.

Question 8

I can distinguish between inhibition and excitation of a nerve cell.

Answer 8

NTs that increase the likelihood of a postsynaptic cell firing and action potential are called excitatory NTs. The ligand-gated channels that bind excitatory NTs allow sodium ions to enter the cell.
NTs that decrease the likelihood of a postsynaptic cell firing an action potential are called inhibitory NTs. The ligand-gated channels that bind inhibitory NTs either allow potassium ions to move out of the cell or chloride ions to move into the cell.
The collective effect of these signals is called summation. There are two types of summation:
Temporal summation: involves one upstream neuron that typically has a firing rate faster than the receiving neuron.
Spatial summation: involves multiple upstream neurons that modulate potential differences across the receiving neuron’s membrane.

Question 9

I can define homeostasis as the maintenance of a set of internal conditions that facilitate body processes in mammals including temperature, pH, [blood glucose], etc.

Answer 9

“Any self-regulating process by which biological systems tend to maintain stability while adjusting to conditions that are optimal for survival. If homeostasis is successful, life continues; if unsuccessful, disaster or death ensues. The stability attained is actually a dynamic equilibrium, in which continuous change occurs yet relatively uniform conditions prevail.”

Question 10

I can identify the major organs of urination and explain how urination is regulated by the nervous system (e.g. pontine storage area sends signals that inhibit the opening of the internal urethral sphincter when the bladder is empty).

Answer 10

metabolism. At any given time, 20% of your blood is in your kidneys. The other functions are to reabsorb and maintain electrolytes, pH, and fluid balance. They are released key hormones. (Filtration, Reabsorption, and Secretion)
Ureter- The ureters transport urine to the bladder.
Urinary Bladder- The urinary bladder holds urine.
Urethra- The urethra releases urine from the body by relaxing and contracting sphincter muscles.
Nephrons- The nephrons are filtering units.
Pons- The pons regulates the need to pee and the ability to hold it.
Renal Pelvis- Urine collects here and is funnelled into the ureter, the tube that connects the kidney to the bladder.
The br​ain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals occur in the correct order, normal urination occurs. The pons is the main relay centere between the bladder and brain.

Question 11

Path to the parasympathetic nervous system

Answer 11

Nervous system
Peripheral Nervous system
Motor divison (efferent)- take information for the central nervous system to muscles and glands that changes the activities of these structures (multipolar neurons)
Autonomic- governs life processes that occur without conscious thoughts taking place (breathing, digestion, blinking, and heart rate)
Parasympathetic- rest and digest

Question 12

Path to the sympathetic nervous system

Answer 12

Nervous system
Peripheral Nervous system
Motor divison (efferent)- take information for the central nervous system to muscles and glands that changes the activities of these structures (multipolar neurons)
Autonomic- governs life processes that occur without conscious thoughts taking place (breathing, digestion, blinking, and heart rate)
Sympathetic- Fight or flight

Question 13

Path to somatic nervous system

Answer 13

Nervous system
Peripheral Nervous system
Motor divison (efferent)- take information for the central nervous system to muscles and glands that changes the activities of these structures (multipolar neurons)
Somatic- Responsible for carrying out life processes that are governed by conscious thought (eating, walking, talking, and reproducing.)

Question 14

Path to sensory nervous system

Answer 14

Nervous system
Peripheral Nervous system
Sensory- (afferent) brings sensory information (touch, position in space) from a sensor to the spinal cord (mostly unipolar neurons)

Question 15

Path to central nervous system

Answer 15

Nervous system
Central nervous system- brain and spinal cord

Question 16

Neuron structure

Answer 16

Dendrites, cell membrane, cell body, axon, myelin sheath, axon terminal

Question 17

What happens when you put your hand on the stove (brain)

Answer 17

• Stimulus is detected by a sensory receptor
• Nocireceptor (pain receptors that is sensitive to heat)
• Generates a receptor potential (histamine NT influx in cleft)
  -Afferent neuron fires an action potential, enters the spinal cord via the dorsal root.
• Causing an interneuron to fire an action potential
• Brain
• Thalamus
  -> Somato sensory cortex (where the pain is)
  -> Limbic system (emotional response)
  -> Prefrontal cortex (understand and interpret the pain)

Question 18

What happens when you put your hand on the stove (muscles)

Answer 18

• Stimulus is detected by a sensory receptor
• Nocireceptor (pain receptors that is sensitive to heat)
• Generates a receptor potential (histamine NT influx in cleft)
  -Afferent neuron fires an action potential, enters the spinal cord via the dorsal root.
• Causing an interneuron to fire an action potential
• A motor neuron fires an action potential, leaves the spinal cord via the ventral root.
• Generates a muscle contraction, flooding of acetylcholine
• Effect, activated muscle or gland in response to change.

Question 19

Nephron

Answer 19

1. Filtration
   Blood enters the nephron though the afferent arteriole and goes through the glomerulus. The pressure is high enough to push blood, water, and ions through into the Bowman’s Capsule. It leaves through the efferent arteriole.
2. Tubular Reabsorption
   In the proximal convoluted tubule, ions like salt leave the urea. In the descending loop of Henel, H2O leaves because the medula is so salty. In the middle of the loop, the filtrate is most concentrated. On the ascending side, Na and Cl leave the filtrate because the medullary fluid is less concentrated than the filtrate at this point. It then goes though the distal convoluted tubule where more sodium and potassium leave. It then goes through the semi preamble collecting duct to the urter to be peed out.
3. Tubular Secretion
   In

Question 20

Need to drink

Answer 20

Osmoreceptors shrink in response to low water. The shrinking of the osmoreceptors stimulates the secretion of anti-diuretic hormones from the posterior pituitary, it goes to the kidneys via the circulatory system. This is due to osmosis. In the kidneys it goes to the collecting ducts. It tells the collecting ducts to conserve water, making it more permeable to water. The thirst centre is also notified as this process cannot continue forever as you would die. This tells you that you are thirsty. Having a drink ultimately increases blood volume and decreases osmolarity and the osmoreceptors swell.

Question 21

I can identify the major organs of excretion and the metabolic wastes that each helps regulate in a human being (e.g. sweat glands in the skin help regulate body temperature and the salt concentration of the blood).

Answer 21

Sweat Glands- body temperature, electrolytes, and water balance.
Lungs- CO2, water, and heat
Kidney- electrolytes, metabolic waste, and water
Skin- heat

Question 22

I can identify some of the effects of drugs on the brain.

Answer 22

Cocaine- Dopamine. Coke blocks reputake pumps for dopamine so it binds again and again, overstimmulating the cell. Reward pathway and voluntary movement.
Heroine- Doapmine. Heroine binds to receptors, preventing dopamine inhibition allowing doapmine to flood the synaspe. It can be used as a painkiller.
Alcohol- GABA and glutamate. It makes GABA inhibitors more effective and binds to glutamate receptors preventing them from from exciting the cell. Effects memory, discison making, and impluse control.
Meth- Doapmine. Meth mimics doapmine and is taken into the cell pushings out doapmine. Because of the excess it start sending out the dopamine. The excess dopamine binds to the receptors and overstimmulates the cell. Works on the brains reward pathways.

Question 23

I can identify the major organs of the endocrine system.

Answer 23

Hypothalamus- HPT and HPA axis.
Thyroid- T3 and T4
Adrenal Gland- HPA axis.
Pancreas- Produces insulin and gluagon which control blood sugars.
Pituitary Gland- HPT and HPA axis. Master gland.

Question 24

I can identify how urine is produced by filtration, reabsorption and secretion and how active and passive transport processes are used to regulate the composition of urine.

Answer 24

Filtration- In filration blood from the aotic artrie is pumped into the acending, which goes into the glomarus. Smaller molecules in the boold are able to go into the Bowman’s capsule because they
Reabsorption- In reabsorptionit then travels through the proximal convoluted tubule where ions, like salt leave. It then goes through the loop of Henle. The descending side is only preamble to water that eants out as the medial is salty. (Osmosis.)
Secretion- In secretion on the accdening loop of Henle is only preamble to ions that leave to make the medula salty to attract water. It then travels to the distal convoluted tubule to remove more salt. Then it reaches the collecting duct to travel to the urters. Here some times water leaves.