Intro to Physiology

Question 1

Define the term homeostasis. Explain some of the challenges of maintaining
homeostasis.

Answer 1

• the process associated with the maintenance of a constant state
• the ability or tendancy of an organism to maintain internal equilbria by adjusting physiological processes against external fluctuation
• homeostatis is multicellular and this can make things difficult because different cell types require different things
• requires at least four interacting components: stimulus, sensor, control centre, and effector.
• nfections, allergens, toxins, and noxious xenobiotics can impact homeostasis

Question 2

What are feedback loops? Provide examples of both positive and negative feedback
loops.

Answer 2

• regulatory processes of homeostasis depend on the principle of feeback
• positive feedback loops: a process (series of effects) that reinforce (or amplifies) that process to continue). for example birth or breastfeeding
• negative feedback loop: a process (series of efects) that negates (or subdues) that process fro continuing. maintains homeostasis. much more common that positive feedback loop. Ex. time mangement and procrastination; blood sugar regulation
  SEE DIAGRAMS OF BOTH

Question 3

What is a neurotransmitter? What is their importance to drug action and effects?

Answer 3

• chemicals that are released between two nerve cells (presynaptic nerve to psotsynaptic nerve) thereby affecting the electrical potential of the second (postsynaptic) nerve
• recieveing cells must have specific receptors for the neurotransmitter to be affected
• Drugs interfere with the way neurons send, receive, and process signals via neurotransmitters. Some drugs, such as marijuana and heroin, can activate neurons because their chemical structure mimics that of a natural neurotransmitter in the body. This allows the drugs to attach onto and activate the neurons

Question 4

action potenial tiggers a release of neurotransmitter

Answer 4

-an action potential is initiated by a stimulus, leading to a rapid change in membrane potential and sequential opening and closing of ion channels. This process allows for the transmission of signals along the nerve axon and subsequent communication with other neurons or effector cells.
1. action potenial arrives; triggers entry of ca2+
2. in rsponse to ca2+, synatpic vesicles fuse with synaptic membrane, then release neurotransmitter
3. ion channels open when neurotransmitter binds; ion flows cause chane in postsynaptic cell potential
4. ion channels will close as neurotransmitter is broken down or taken bac up by presynaptic cell
SEE DIAGRAM

Question 5

What is a hormone?

Answer 5

• chemical that are released by a cells or a gland in one part of the body that affects cells in other parts of the organism
• recieveing cells must have specific (intracellular) receptors for the hormone to be affected
• ex epinephrine

Question 6

What is an agonist? What is an antagonist? How do their effects differ?

Answer 6

• agonist: a chemical that bind to a receptor of a cell and triggers a response by that cells. mimic the action of a naturally occurin substance. perpetuates what is happening. Initiates pathway. super, full and partical agonists/ ex. isoproterenol, mimics aderaline
• antagonist: binds the receptor site and prevents the binding of an agonist or inverse agonist. can be reverible or irrevesible inhibits signaling pathway. Stops.
• agonists keep the pathway going; antagonists stop it

Question 7

What is a diuretic?

Answer 7

• medicines that help reduce fluid buildup in the body
• Most diuretics help the kidneys remove salt and water through the urine. This lowers the amount of fluid flowing through the veins and arteries. As a result, blood pressure goes down
• common treatment for high blood pressure

Question 8

What is a metabolite?

Answer 8

• a substance formed in or necessary for metabolism.
• Metabolites can have a multitude of functions, including energy conversion, signaling, epigenetic influence, and cofactor activity
• an intermediate or end product of metabolism

Question 9

What are the renal and hepatic systems? Why are it important?

Answer 9

• renal system: in humans, organ system that includes the kidneys, where urine is produced, and the ureters, bladder, and urethra for the passage, storage, and voiding of urine
  -hepatic system: he hepatic system detoxifies blood, metabolizes glucose, and synthesizes proteins, and is a blood reservoir. The liver and heart are connected through the hepatic artery
• they are portal systems. they are important to eliminate toxins, balance electrolytes, maintain homeostasis, waste elimination, fluid balance, protein synthesis, metablosim, storage of nutrients. impotrant for overall health

Question 10

what are the types of intercellular communication

Answer 10

• autocrine signals: act on the same cell that secretes them
• paracrine signals: diffuse locally and act on neighbouring cells
• endocrine signals: hormones carried betwen cells by blood or other body fluids
• neural signals: diffuse a short distance between neurons
• neuroendocrine signals: released from neurons but are carried by blood or other body fluids and act on distant cells
• pheromones: released into the environment and act on a different individual

Question 11

what is an inverse agonist

Answer 11

• a chemical that binds to a receptor of a cells and triggers a response by that cell
• agonists induce the opposite action of a naturally occuring substance
• does the opposite of what an agonist does.
  partial and full inverse agonists

Question 12

what is a super agonist

Answer 12

• an agonist that is capable of producing a maximal response greater than the endogenous agonist

Question 13

how are receptors activated or inactivated

Answer 13

• endogenous agonists and anatagonists (ex. hormones and neurotransmitters)
• exogenous agonists and antagonists (such as drugs)

Question 14

method of action vs mode of action

Answer 14

• Mode of action usually refers to the functional or anatomical changes at a cellular level induced by exposure to a substance, whereas method of Action includes specific targets or pathways modulated by the compound.

Question 15

method of action

Answer 15

• see flow chart in notes

Question 16

structure and function of a nerve cell

Answer 16

• dendrite: collect electrical signals
• cell body: integrates incoming signals and genertes outgoing signals to axon
• axon: passes eelctrical signals to dendrites of another cells or to an effector cell

Question 17

resting potential

Answer 17

Neuron maintains a resting membrane potential of around -70 mV.
Sodium (Na+) and potassium (K+) ions are unequally distributed across the membrane.

Question 18

action potenal specifcs

Answer 18

1. resting potential
2. Depolarization:
   - Stimulus reaches the axon hillock, causing depolarization. If depolarization reaches the threshold (-55 mV), voltage-gated sodium channels open.
3. Rapid Sodium Influx:
   - Sodium rushes into the neuron, leading to a rapid increase in membrane potential.
   - Membrane potential reaches around +30 mV during the rising phase of the action potential.
4. Repolarization:
   - Sodium channels close, and voltage-gated potassium channels open.
   - Potassium leaves the neuron, repolarizing the membrane.
5. Hyperpolarization and Refractory Period:
   - Potassium channels briefly overshoot, causing hyperpolarization.
   - Absolute refractory period prevents immediate re-excitation.
6. Propagation:
   - Action potential travels down the axon due to local depolarization.
   - Sodium channels open sequentially in adjacent segments, ensuring one-way propagation.
7. Saltatory Conduction (If Myelinated):
   - In myelinated axons, action potential jumps between nodes of Ranvier.
   - Faster conduction due to reduced ion leakage.
8. Axon Terminal and Synaptic Transmission:
   - Action potential reaches synaptic terminals.
   - Triggers release of neurotransmitters into the synapse.
9. Reception by Next Neuron or Effector Cell:
   - Neurotransmitters bind to receptors on the postsynaptic membrane.
   - Initiates a new action potential in the next neuron or effector cell.

Question 19

na k pump

Answer 19

• The primary function of the Na+/K+ pump is to actively transport sodium ions (Na+) out of the cell and potassium ions (K+) into the cell against their respective concentration gradients.
  steps:
  1. three sodium ions enter the protein from within the cell
  2. atp phosphorylates the pump. it changes shape and releases 3 na to the outside of the cell
  3. two potassium ions eter the protein from outside the cell
  4. the phosphate group drops off the pump. the protein changes shape and releases 2 kto the interior of the cell
• it is an active, atp-driven pump
• plays a fundamental role in maintaining the resting membrane potential of cells, regulating cell volume, and contributing to the electrical excitability of neurons and muscle cells.