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Human Physiology > Phone Unit 1 > Flashcards

Phone Unit 1 Flashcards

1
Q

What ions are more concentrated inside/outside the cell?

A

Potassium: inside Sodium chloride and bicarbonate: outside

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2
Q

What is osmosis

A

Movement of water across a membrane due to a solute gradient

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3
Q

What is osmotic pressure?

A

Pressure that exerts a force to oppose osmosis

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4
Q

Molar it’s vs osmolarity?

A

Molarity: mols per liter Osmolarity: ions per liter

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5
Q

Given solution A and B, and solution A is more concentrated. Which is hyposmotic and which is hyperosmotic?

A

A is hyperosmotic to B B is hyposmotic to A If they had the same concentrations, they’d be is isosmotic

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6
Q

If solution A is hypotonic relative to the cell, than the cell ___

A

The cell swells. Hypotonic as a result of water LEAVING solution.

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7
Q

If solution B is isotonic relative to the cell, than the cell ___

A

The cell doesn’t change size

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8
Q

If solution C is hypertonic relative to the cell, than the cell ___

A

The cell shrinks. Hyper tonic as a result of fluid ENTERING cell

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9
Q

How do to tonicity and osmolarity differ?

A

Tonicity always compares a solution and a cell (cell volume change). Tonicity also depends on whether solute are penetrating or not Osmolarity is a reciprocal relationship to compare two cells.

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10
Q

What properties of molecules influence movement across cell membrane?

A

The size of the molecule and its lipid solubility. Large molecules, ions, and polar molecules don’t cross membrane easily

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11
Q

Active transport vs passive transport?

A

Passive transport does not require energy whereas active transport requires it (like ATP)

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12
Q

What do we know about diffusion?

A
  1. Passive 2. High–>low concentration 3. Net movement until equal concentration everywhere 4. Rapid over short distances, slower of long 5. Related to temperature. High temp, inc rate 6. Inversely relates to molecular weight and size. 7.open system or across a partition
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13
Q

What is ficks law of diffusion?

A

Rate of diffusion is proportional to surface area, concentration gradient, and membrane permeability. Think: emphysema and hydrophobic interior

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14
Q

What influences membrane permeability?

A
  1. Size/shape of molecule 2. Lipid solubility 3. Composition of lipid bilayer
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15
Q

What is facilitated diffusion?

A

Mediated transport down concentration gradient. Doesn’t require energy

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16
Q

What are the four classes of functional membrane proteins:

A
  1. Structural proteins 2. Enzymes 3. Receptors 4. Transporters
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17
Q

What is the function of structural proteins

A

In cell junction and cytoskeleton. Hold, connect, and attach to keep tissues and membrane together

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18
Q

What is the function of membrane enzymes?

A

Catalyze chemical reactions on cell surface or in cell. Active in metabolism and signal transfer

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19
Q

What is the function of membrane receptor proteins?

A

Part of the body’s signaling system. Activate enzymes, open/close chemical channels, etc. Ligands bind to receptor

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20
Q

What are membrane transporters?

A

Membrane spanning proteins 1. Carrier- only open on one side. Larger molecules 2. Channel- water filled pore Gated and open channels. Faster transport.

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21
Q

What is active transport?

A

Moving a molecule against its concentration gradient. Requires direct or indirect form of energy, ATP.

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22
Q

What is the difference between primary and secondary active transport?

A

Primary active transport involves the direct use of ATP, while secondary active transport involves the indirect use of ATP. Secondary active transport involves a molecule moving against it’s concentration gradient with potential energy from another molecule moving with its concentration gradient.

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23
Q

What is the sodium potassium pump?

A

An example of active transport. Sodium moves out of the cell (against gradient) and potassium moves into the cell (against gradient).

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24
Q

What is the mechanism for the NaK pump?

A
  1. ATPase activates Na binding sites (conformational change) 2. Na transported to ECF, dephosphorylation leads to affinity for K. 3. K binding leads to original conformation, release of K into ICF, and return to step 1.
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25
Q

What is the sodium-glucose cotransport mechanism?

A

An example of secondary active transport. Binding of Na increases affinity for glucose. 1. Na from ECF binds to protein. 2. Conformational change, glucose binds 3. Protein opens to inside of cell, then releases Na and glucose. (When Na leaves, reduced affinity for glucose). **Think (Clubs)

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26
Q

What characteristics of carrier-mediated transport determine what/how much substance is transported?

A
  1. saturation: results in transport maximum, only so many carriers. 2. competition: binding of more than one molecule, then depends on number of molecules of each. 3. specificity: ex. 6-carbon sugar limiting transporters.
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27
Q

What are the different ways of vesicular transport?

A

Used for larger macromolecules, involves the cell membrane. 1. phagocytosis 2. endocytosis 3. exocytosis

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28
Q

what is phagocytosis?

A

An actin-mediated process that requires ATP. Bacterium engulfed by cell membrane and lysosomes attach and “eat” the invader.

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29
Q

What is endocytosis?

A

3 types: 1. pinocytosis- “drink” nonselective process 2. receptor-mediated cytosis: ligand binds to receptor to initiate the process. Located in “pits,” regions high in protein clatherin. Vesicle is formed and loses clatherin coating. Receptor and ligands separate. Ligand is either destroyed (lysosomes) or processed (golgi apparatus). Receptor is moved in transport vesicles and exits cell. 3. potocytosis- similar to receptor mediated process but involve caveolae. Help concentrate and internalize small molecules, aid in cell signaling, and aid in transfer of macromolecules across capillary epithelium.

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30
Q

What is exocytosis?

A

Opposite of endocytosis. Used to secrete large polar molecules. Allows cell to add components to plasma membrane.

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31
Q

What is epithelial transport?

A

Movement of substances between cells (paracellular, though uncommon because of tight junctions) or through cells (transcellular). Usually one step is uphill and one is downhill.

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32
Q

What is absorption? secretion?

A

absorption: movement from lumen to ECF secretion: movement from ECF to lumen

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33
Q

What are the steps involved in transcellular transport of glucose?

A
  1. Glucose and Sodium symport. Glucose against gradient, sodium with gradient. Secondary active transport. 2. Glucose passes out of cell via facilitated diffusion. with gradient 3. Na K pump removes sodium, against gradient
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34
Q

What is transcytosis?

A

Combination of endocytosis and exocytosis used from transport through cell. Used for large molecules

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35
Q

What is the equilibrium potential of a cell?

A

point when chemical gradient equals electrical gradient.

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36
Q

In which way do sodium and potassium leak and which way does the Na K pump transport them?

A

K wants to move out of cell, down its concentration gradient. Na wants to move into cell down its concentration gradient The Na K pump wants to move K into cell and Na out of cell.

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37
Q

What two factors influnce a cell’s membrane potential?

A
  1. concentration gradient 2. membrane permeability to ions
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38
Q

What is depolarization?

A

When the membrane potential is going towards zero, the membrane potential difference is decreasing

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39
Q

What is repolarization?

A

The membrane potential is returning to it’s resting state. Membrane potential difference is increasing.

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40
Q

What is hyperpolarization?

A

The membrane potential difference is becoming larger than the resting state, becoming more negative

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41
Q

What is a gap junction?

A

Protein channel that creates a bridge between two cells, connexins. Only smaller molecules can pass through gap junctions

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42
Q

What is contact-dependent signaling?

A

Requires contact between two membranes. Receptor on one membrane reaches another. Involves CAMs (cell adhesion molecules) that act as receptors

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43
Q

What is the difference between paracrine and autocrine signaling?

A

Paracrine signaling involves a cell signal being sent to many other cells. Autocrine signaling involves a cell signal being received by the same cell that made it. These are both examples of local signaling processes because the signals are limited by diffusion

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44
Q

What two systems are involved in long-distance communication? What is the name of the chemical message they send out?

A

The endocrine and nervous system send out chemical messages called hormones

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45
Q

Different types of neurocrines: What are neurotransmitters and how do they differ from neurohormones and neuromodulators?

A

Neurotransmitters act quickly over short distances while neuromodulators act slowly in a paracrine or autocrine fashion. Neurohormones release the chemical signal directly into the blood.

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46
Q

What are the steps in the signal pathway?

A
  1. ligand (first messenger) binds to receptor 2. binding actives receptor molecule 3. Receptor molecule activates intracellular molecule 4. Intracellular molecule alters protein 5. Initiates response
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47
Q

What type of chemical signals can diffuse through the membrane and bind to receptors in cytoplasm or nucleus?

A

Lipophilic because they can cross inside of cell membrane. Not very water soluble, so don’t want to be in outside of cell. Instigate the production of NEW proteins. (slower) ex: steroids, thyroid hormones

48
Q

What type of chemical signals can’t easily diffuse through membrane and require a membrane receptor?

A

Hydrophilic chemical signals because they can’t cross through lipophilic membrane. Ligand binding to receptor and signal pathway usually results in ALTERED protein. (faster) ex: most are peptides/proteins. Insulin, catecholamines, FSH.

49
Q

What are the major categories of receptor proteins?

A

G-protein coupled receptors (rhodopsin), receptor-channels (rapid/influence permeability, receptor-enzymes (receptor region on ECF/enzyme region on ICF), and integrin receptors (cytoskeleton)

50
Q

What are the steps in signal transduction, and which parts of the cell are involved in each step?

A
  1. receptor (ligand binding as 1st messenger) 2. transducer (membrane protein) 3. amplifier (amplifier enyzme, 2nd messengers) 4. response (last 2nd messenger)
51
Q

What are the steps in the cAMP 2nd messenger pathway?

A
  1. ligand binds to receptor (ECF) 2. g-proteincoupled receptor activates after (GDP–> GTP) then activates adenyly cyclase (ICF) 3. AC (amplifier enzyme) turns ATP into cAMP 4. cAMP actives protein kinase A 5. PKA phosphorylates proteins 6. target proteins change. 7. changed proteins have response
52
Q

What are the steps in the calcium/ calmodulin 2nd messenger pathway?

A
  1. Ligand binds to receptor 2. G-protein actives PLC, an amplifier enzyme. 3. PLC converts PIP (membrane phospholipids) into DAG and IP3. –> DAG remains in membrane –> IP3 moves into cytosol 4. –>DAG activates Protein Kinase C (PKC) which phosphorylate proteins –>IP3 causes release of calcium from organelles, which activates calmodulin 5. Both phosphorylated proteins and calmodulin lead to an intracellular response.
53
Q

Why can epinephrine either constrict or dilate different blood vessels? How can one ligand yield different responses?

A

There are different isoforms of the receptors that the ligand binds to.

54
Q

What do down-regulation and up-regulation do? Desensitization?

A

Down-regulation lowers the number of receptors (endocytosis) while up-regulation increases the number of receptors (exocytosis) Desensitization is when a modulator attaches to the receptor to diminish sensitivity to the signal molecule even if it’s in high concentration

55
Q

How is the 2nd messenger cascade terminated?

A

-First messenger is removed -Alpha subunit turns itself off -Downstream effectors are turned into their original state

56
Q

What are Cannon’s postulates?

A
  1. The nervous system has a roll in controlling “fitness” of the body 2. Some systems are under tonic control. (think: dials controlling volume. Level of intensity controls response) 3. Some systems are under antagonist control (different signals used which have opposite controls ex: fight or flight). 4. One chemical signal can have different effects in different tissues.
57
Q

What are the steps of the reflex pathway?

A
  1. stimulus 2. sensor/receptor (must meet threshold) 3. afferent (towards) 4. integration center 5. efferent (away) 6. target/effector (carries out response) 7. response
58
Q

What is the difference between local control and reflex control?

A

Local control is short distance control, often in an autocrine or paracrine fashion. Reflex control is a long distance control by the nervous or endocrine systems.

59
Q

In both neural and endocrine reflexes, what are the difference in speed, specificity, chemical/electrical nature, length of time, and stimulus variation requirements for a response?

A

Neural controls: fast, specific, chemical/electrical signaling, short lasting, and intensity variation is displayed by a change in frequency of signal Endocrine controls: slow, not specific, chemical signaling only, long lasting response, and intensity displayed by varying amount of hormones secreted.

60
Q

What is negative feedback?

A

The response stimulus shuts of the initial stimulus. Self-stopping mechanism

61
Q

What is positive feedback?

A

Positive feedback has no self-stop so the response gets further and further from set-point. An outside mechanism is needed to shut off the system

62
Q

What are feedforward controls?

A

anticipatory reflex controls. (like braking a car)

63
Q

What are biological rhythms?

A

Predicted physiological change associated with time Circadian rhythms and seasonal rhythms for example.

64
Q

What is the definition of a hormone?

A

A chemical secreted into the blood in very low concentrations that has its effects in long distances. Hormones can be released by endocrine glands, neurons (neurohormones), or by the immune system (cytokines)

65
Q

What four things do we know about the complexity of hormone action?

A
  1. A single gland can produce multiple hormones 2. A single hormone may be secreted by more than one gland 3. A single hormone can have more than one target cell 4. Rate of hormone secretion can vary cyclically (ex. menstrual cycle)
66
Q

What do we know about the complexity of endocrine function?

A
  1. A single target cell may be influenced by more than one hormone 2. A chemical messenger may be classified either as a neurotransmitter or hormone depending on its source and method of delivery 3. Some organs are exclusively endocrine while others aren’t (testes)
67
Q

What do we know about synthesis/storage/release of peptide/proteins hormones?

A

-Preprohormones are synthesized in the ER -process in the golgi apparatus into prohormones (post-translational modification) -then packaged into secretory vesicles as hormones. Stored. -secreted by exocytosis into the blood stream

68
Q

What are the different chemical classes of hormones?

A
  1. peptide/protein hormones: composed of linked amino acids 2. amine hormones: from amino acids, typically tyrosine and tryptophan 3. steroid hormones: from cholesterols
69
Q

What do we know about mechanism of action, half-life, and transport of peptide/protein hormones?

A

Mechanism of action: Lipophobic so must bind to cell surface receptors to elicit response via signal transduction pathways. Half-life: short transport: lipophobic but water soluble so can travel in the ECF

70
Q

What do we know about synthesis/storage/release of steroid hormones?

A

-Basic modification in the smooth ER -Usually are similar in structure (derived from cholesterol) -Made in adrenal glands, reproductive glands (gonads), and placenta in females -Lipophilic, but diffuse through the membrane easily.

71
Q

What do we know about the mechanism of action, half-life, and transport of steroid hormones?

A

Mechanism of Action: Steroid hormones are synthesized as needed (not stored). Because they are lipophilic, they need to bind to carrier proteins in the ECF (hydrophobic). Once isolated from carrier, they can diffuse through membrane into cytosol and nuclear receptors. Results in new protein synthesis, gene activation/inactivation. Long lag time between binding and response (bc you have to make a new protein) Half-life: Steroid hormones have an extended half-life due to the fact that they bind to carrier proteins. Transport: Bind to carrier proteins, however, carrier proteins make it hard for steroid proteins to enter cell. Only isolated steroid hormones may diffuse easily through membrane.

72
Q

What do we know about amine hormones?

A

-Derived from the amino acids tryptophan (melatonin) and tyrosine (catecholamines and thyroid hormones) -Catecholamines act like peptide proteins, binding on surface receptors. -Thyroid hormones act like steroid hormones and bind to intracellular receptors to activate gene transcription

73
Q

Simple endocrine reflexes are controlled by what feedback mechanism?

A

Controlled by a negative feedback loop.

74
Q

What are the major classes of neurohormones?

A
  1. catecholamines 2. hypothalamic neurohormones 3. hypothalamic neurohormones
75
Q

What is the pituitary gland?

A

A structure that extend downward from the brain that contains two distinct and functionally differing lobes. 1. anterior lobe: glandular 2. poster lobe: neural. Secretes neurohormones made in the hypothalamus

76
Q

What hormones are released from the posterior pituitary gland, what is their function?

A
  1. vasopressin: antidiuretic hormone (ADH), water balance 2. oxytocin: controls ejection of milk and contractions during labor **Cells can make either/or but not both
77
Q

What hormones are released from the anterior pituitary gland, what is their function? What is a tropic hormone? Which hormone is not a tropic hormone?

A
  1. luteinizing hormone (LH)–> gonads 2. thyrotropin (TSH)–>thyroid 3. growth hormone (GH)–> liver 4. adrenocorticotropin (ACTH)–>adrenal cortex 5. follicle-stimulating hormone (FSH)–> gonads *top 5 are tropic hormones, hormones that control the secretion of OTHER hormones. **6. prolactin (PRL)–> mammary glands only not tropic hormone
78
Q

What is the sequence of events in a complex endocrine pathway?

A

stimulus–> hypothalamus–> tropic hormone 1–> anterior pituitary gland–> tropic hormone 2–> endocrine gland–> hormone 3–> target tissue–> response

79
Q

What two feedback loops control the complex endocrine pathway?

A
  1. short-loop feedback loop: tropic hormone from anterior pituitary uses negative feedback to stop hypothalamus 2. long-loop feedback loop: hormone from endocrine gland goes back to anterior pit. gland and/or hypothalamus to stop secretion
80
Q

What is the hypothalamic- hypophyseal portal system? What are the advantages?

A

region of circulatory system directly transports hormones from the hypothalamus to the anterior pituitary gland. Advantage: hormones aren’t diluted as much. Not as much hormone is then required to elicit a given response.

81
Q

What are the functions of the anterior pituitary hormones?

A
  1. PRL: milk production 2. FSH/ LH: gonadotropins 3. TSH: regulates thyroid hormone secretion 4. ACTH: regulates prod/secr. adrenal cortex 5. GH: metabolism and regulate hormone production by liver.
82
Q

What are the effects that hormones have on other hormones?

A
  1. permissiveness: affect hormone has is dependent on presence/absence of another hormone. 2. synergism: hormones are complementary. Their mutual effect is greater than sum of independent effects (1+1=3) 3. antagonism: one hormone results in loss of another hormone’s receptors.
83
Q

What are the 3 basic patterns of endocrine pathologies?

A
  1. hormone excess: hypersecretion 2. hormone deficiency: hyposecretion 3. abnormal responsiveness: down-regulation, abnormalities in signal transduction pathways.
84
Q

What are the two major systems within the nervous system? Do they divide further?

A
  1. Central nervous system- brain and spinal cord 2. peripheral nervous system –>a. afferent: to CNS –>b. efferent: from CNS ——>1. somatic: skeletal muscle ——>2. automatic: smooth and cardiac ———–>a. sympathetic ———–>b. parasympathetic
85
Q

What are dendrites? Do they have Na+ channels?

A

“input” collect signals from surrounding cells. Sparse Na+ gated channels

86
Q

What are Axons? Axon hillock? Axon terminal? Do they have Na+ channels?

A

“output” conduct the action potential away from the cell –> axon hillock: where the action potential leaves the cell. Contains concentration of Na+ channels. Site where AP are intiated by graded potential –>axon terminal: release chemical messenger in response to AP

87
Q

What are the three functional classes of neurons?

A
  1. Afferent neurons: mostly in PNS. cell body doesn’t have dendrites. Axon terminals in CNS. 2. Interneurons: connect aff to eff neurons. located in CNS. 99% of neurons are these. (abstract mind). 3. Efferent neurons: located in PNS. Cell body in CNS. Axon terminals extend to effector organ
88
Q

What are the types of glial cells found in the CNS?

A

(“ammo”) A: astrocytes–> support, BBB M: microglia–> immune O: oligodendrocytes–>myelin sheath E: ependymal cells–>ECF brain

89
Q

What are the types of glial cells found in the PNS?

A

S: satellite: support S: schwann: myelin sheath

90
Q

With an open channel, in which direction would K and Na flow? Does this represent depolarization, repolarization or hyperpolarization?

A

K: potassium would flow out of the cell, down its concentration gradient. This would make the cell more negative (hyperpolarized) Na: Sodium would enter the cell and make the cell more positive (depolarized)

91
Q

What are the different types of gated channels?

A
  1. voltage-gated: change in membrane potential 2. mechanically-gated: physical change (like pressure) 3. chemically-gated: concentration gradient, have membrane receptors *Na gated channels open fast, K gated channels open slow.
92
Q

What are the two kinds of potential changes?

A
  1. graded potentials: -variable in size -can cause an AP -signal diminishes with distance -short-distance 2. action potentials: -very brief, large depolarizations -long distance signals -don’t diminish in strength -rapid signal over long distance
93
Q

What is the difference between graded potentials and action potentials in type of signal, location, gated channels involved, ions involved, strength of signal, initater of signal, unique characteristics, and hyperpolarization/depolarization?

A
94
Q

What causes graded potentials to die out?

A
  1. ion leak through open channels. (less current flow)
  2. cell membrane. (resistance)
95
Q

What is the trigger zone? Is it different in afferent and efferent neurons?

A

The trigger zone is the integrating center of the neuron and contains a lot of sodium voltage-gated channels.

In efferent and interneurons, the trigger zone is the axon hillock and the very first part of the axon, or initial segment.

In afferent neurons, the triggering zone is the region where the dendrites meet the axon (adjacent to the receptor)

96
Q

Label the events that comprise the axon potential

A
  1. resting membrane potential.
  2. depolarizing stimulus
  3. Reaching threshold (-55mV). Voltage-gated Na channels open, voltage-gated K channels open slowly
  4. Na rapidly enters cell, depolarizes quickly
  5. Na channels close, slow K channels open
  6. K moves out of cell, repolarizing it
  7. K still moves out of cell, hyperpolarizing it
  8. Voltage-gated K channels close
  9. Return to resting membrane potential
97
Q

Which voltage-gated channel contain an activation gate and an inactivation gate, Na or K?

A

Voltage-gated Na channels have two gates, an activation or an inactivation gate.

Both gates must be open for flow of Na in and out of cell.

98
Q

What are the three configurations of the voltage-gated Na channels?

A
  1. Closed but able to open
  2. Open (activated)
  3. Closed but incapable of opening (inactivated)
99
Q

Whats true about the voltage-gated K channels?

A

There is one gate with two configurations (either open or closed)

100
Q

What is true at resting potential?

A

No voltage-gated channels are open

Leak channels are still open, more membrane permeability to K than Na

101
Q

What happens at the triggering event?

A

A membrane depolarizes from a triggering event due to the influx of sodium ions. Sodium moves down it’s concentration and electrical gradient. More voltage-gated sodium channels open in response to depolarization (positive feedback)

102
Q

What is the overshoot?

A

The portion of the action potential that is positive, greater than 0.

103
Q

What happens at threshold?

A

At threshold, enough Na gates have opened to set up the positive feedback loop. Na permeability increases and Na rushes into the cell.

104
Q

What happens at the return to resting potential?

A

Na channels moved to a “closed, but inactive” state and K channels are open. K ions exit the cell and the cell rapidly repolarizes.

Na channels then return to their “closed but capable of opening” state. K channels then close, after allowing an excess to escape (hyperpolarization)

105
Q

What is the difference between the absolute and relative refactory periods?

A

The refactory period is the time when a new AP cannot be initiated because it has just undergone an AP. The refactory period limits the frequency of action potentials. Key characteristic that distinguishs graded potentials from action potentials

Absolute: complete unresponsiveness. Na channels are in activated state but must return to initial “closed but ready” state.

Relative: An AP can be initiated but the triggering event must be larger. This is due to lingering inactive Na channels and hyperpolarization (requires more effort to get to threshold of -55)

106
Q

What is the relationship between speed of an action potential and diameter of a neuron/ presence of myelin sheath?

A

Larger diameter neurons are met with less resistance so speed increases with increasing diameter.

Presence of a myelin sheath increases speed

107
Q

What are the two methods of action potential propagation? Which is faster?

A
  1. contiguous: the spreading of an action potential down the length of the axon. slower
  2. saltatory: the action potential “jumps” between the nodes of ranvier created by the myelin sheath. faster
108
Q

What is true regarding the presence of the myelin sheath?

A

The myelin sheath is composed mostly of lipids. Allows the process of the action potential to require less energy, in the form of ATP. Acts as an insulator. Not part of neuron itself, but forms support cells.

109
Q

In myelinated regions of the neuron, which section of the axon involves the production of an action potential?

A

An action potential is formed within the Nodes of Ranvier.

The myelinated segments of the axon allow the current to “jump” to the next node.

110
Q

What is a synapse? What are the two types?

A

The synapse is a junction of communication between two nerve cells. Communication between an axon terminal of the presynaptic cell and the membrane of the post synaptic cell.

Two types: electrical synapse- pass electrical current through gap junction (rare) and chemical synapse- more common. Electrical signal becomes chemical message which travels across synaptic cleft.

111
Q

Where are neurotransmitters stored?

A

Neurotransmitters are stored in synaptic vessicles within the synaptic knob on the presynaptic cell.

112
Q

What are the synaptic events?

A
  1. An action potential depolarizes the axon terminal.
  2. The depolarization opens voltage gated Calcium channels and calcium enters the cell
  3. Calcium entry triggers exocytosis of synaptic vesicle contents
  4. Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
  5. neurotransmitter binding initiates a response in the postsynaptic cell.
113
Q

What are the differences between neurotransmitters and neuromodulators?

A

Neurotransmitters act at a synapse and elicit a rapid response, whereas neuromodulators act at both synaptic and non-synaptic sites and are slow acting. Neuromodulators bring out long-term changes at the synapse. Neuromodulators may act in an autocrine or paracrine fashion.

114
Q

What do we know about neurotransmitter receptors?

A

All neurotransmitters bind to one or more receptors

Fall into two categories:

  • g-protein coupled receptors (GPCR) are metabotropic (metabolic, signal transduction cascade) receptors
  • ligan-gated channels (LGIC) are ionotropic (allow ions to move into cell, change in membrane potential)
115
Q

How is a signal terminated?

A
  1. Actively transported back to presynaptic terminal or glial cells
    - For storage/repackage/destruction
  2. Enzymatic deactivation
  3. NT can diffuse away from the synaptic cleft
116
Q

What is an excitatory synapse?

A

NT released at the pre-synaptic terminal binds its receptor on the post-synaptic which opens nonspecific cation channels

Na moves into the cell, K moves out. causes DEPOLARIZATION

Known as excitatory post-synaptic potential (EPSP)

. Related to grated potential so can be summed, vary in magnitude, no refractory period

117
Q

What is an inhibitory response?

A

NT released at the pre-synaptic terminal binds to receptor on the post-synaptic terminal which opens non specific cation channels.

Channels for K/Cl are opened. Cl moves into cell or K moves out.

Increased negative charge leads to hyperpolarization (graded potential)

known as Inhibitory post-synaptic potential IPSP

Human Physiology (9 decks)

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