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Biology - SBI4U > Unit 4 - Homeostasis > Flashcards

Unit 4 - Homeostasis Flashcards

excretory, nervous, and endocrine system

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1
Q

Functions of the Excretory/Urinary System

A
  1. excretion of metabolic waste
  2. maintenance of water-salt balance
  3. maintenance of acid-base balance
  4. secretion of hormones
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2
Q

Parts of the Excretory System (organs)

A

Kidneys, Ureters, Bladder, Urethra
Also; the blood vessels (renal arterys and veins, etc)

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3
Q

What are the 3 sections of a kidney?

A

renal cortex, renal medulla, renal pelvis

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4
Q

Nephron (where, function, parts/structure)

A

Functional unit of the kidney; in cortex and medulla, they filter various substances from blood, transforming to urine.

Parts: renal artery, glomerulus, bowmans capsule, proximal tubule, loop of henle (descending and ascending), distal tubule, collecting duct, peritubular capillaries, renal vein

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5
Q

Globular Filtration (brief explanation)

A

moves water and solutes (not protein) from blood plasma into the nephron due to pressure gradient in glomerulus

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6
Q

Tubular Reabsorption (brief explanation)

A

Water and useful solutes are reabsorbed from the filtrate into the capillaries surrounding the nephron for use in the body (from nephron to blood)

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7
Q

Tubular Secretion (brief explanation)

A

Wastes and excess substances are moved from the blood into the filtrate in the nephron (where they will eventually be secreted in urine)
from blood into nephron

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8
Q

Water Reabsorption

A

Water is removed from the filtrate in the nephron and returned to the blood for use by the body

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9
Q

What factors does Glomular Filtration depend on? What aspects of blood are in filtrate?

A
  1. Permeability of the capillaries to the glomerulus
  2. Blood pressure (high bp forces filtration to occur)

Filtrate is everything except for protein and blood cells

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10
Q

What parts of the nephron are substances (other than water) being REABSORBED? Name the substances

A

Proximal Tubule: NaCl, glucose, amino acids, potassium, bicarbonate
Ascending Loop of Henle: NaCl
Distal Tubule: NaCl, bicarbonate
Collecting Duct: NaCl

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11
Q

What parts of the nephron is WATER being REABSORBED?

A

Proximal Tubule
Descending Loop of Henle
Distal Tubule
Collecting Duct

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12
Q

What parts of the nephron are substances being SECRETED? Name the substances

A

Proximal Tubule: H+ ions, Ammonium
Distal Tubule: H+ ions, Ammonium, Potassium

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13
Q

What is the difference between the reabsorption of NaCl in the thin and thick segments of the ascending loop of henle?

A

Thin: Na+ diffuses out, Cl- is passively reabsorbed
Thick: Na+ uses active transport out, Cl- is passively reabsorbed

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14
Q

Why is the Loop of Henle Important?

A
  1. helps replenish Na+ environment of medulla for descending loop and collecting duct (salty medulla so water can be reabsorbed by osmosis)
  2. Makes filtrate less concentrated than tissues and blood that surround it
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15
Q

What happens to collecting duct and distal tubule if dehydration occurs?

A

the permeability increases, so more water is reabsorbed

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16
Q

How does the concentration of urine differ from a hydrated person to a dehydrated person?

A

Dehydrated: low concentration of water, more concentrated urine
Hydrated: high concentration of water, less concentrated urine

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17
Q

What are diuretics?

A

Increase the passing of urine
Examples: ethanol in alcoholic beverages (increases volume of urine) and caffeine

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18
Q

What is ADH (antidiuretic hormone) and its function?

A

Travels through

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19
Q

Homeostasis (definition)

A

the process by which a constant internal environment is maintained despite changes in the external environment

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20
Q

Components of a Homeostatic Control System: Sensor (function)

A

Detects change in variable

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21
Q

Components of a Homeostatic Control System: Control Centre (function)

A

Receives message from sensor and directs response via effector

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22
Q

Components of a Homeostatic Control System: Effector (function)

A

Carries out the response initiated by the control centre, effecting change in variable

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23
Q

Negative Feedback System (definition)

A

response triggered by changed conditions, serves to reverse the change

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24
Q

Positive Feedback System (definition)

A

response triggered by changed conditions, serves to move the variable even further away from steady state (for certain end event, eg child birth)

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25
Q

Central Nervous System (definition)

A

network of nerves that includes the brain and spinal cord; integrates and processes the information sent by nerves

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26
Q

Peripheral Nervous System (definition)

A

network of nerves that carry sensory messages to the central nervous system (CNS) and send information from CNS to the muscles and glands; consists of autonomic system and somatic system

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27
Q

What is a Neuron?

A

nerve cell; basic functional and structural unit of nervous system

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28
Q

What is a Nerve?

A

Message pathway of the nervous system

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29
Q

Glial Cell (definition)

A

Support cell of the nervous system that nourishes neurons, removes their waste, fights infections, and provides supporting framework for all nervous system tissues

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30
Q

Myelin Sheath (function)

A

Protects myelinated axons and speeds rate of nerve impulse transmission, sends signals/impulses quicker

31
Q

Dendrites (function)

A

receives nerve impulses from other neurons or sensory receptors and relays the message to the cell body

32
Q

Cell Body (function)

A

processes input from dendrites, if information is too large it relays it to axon

33
Q

Axon (function)

A

conducts impulse away from cell body

34
Q

Branching ends of Axon (function)

A

communicate with adjacent neurons, glands, or muscles, releases chemical signals into space between it and receptors or dendrites of neighbouring cells.

35
Q

What is a reflex arc? And an example

A

simple connection of neurons that results in a reflex action in response to a stimulus, signal sent without brain.

Withdrawal reflexes, from potentially painful situations

36
Q

Reflex arcs usually only involve ___ neurons to transmit messages. As a result, they can be very rapid, occuring in about _____ miliseconds

A

3, 50

37
Q

Membrane Potential (definition/why)

A

electrical charge separation across cell membrane; form of potential energy.
inside of the cell is negative compared to the outside of the cell

38
Q

Resting Membrane Potential (definition)

A

potential difference across the membrane in a resting neuron, usually -70mV

39
Q

Three Factors that help maintain resting membrane potential?

A
  1. Large protein molecules
  2. Ion specific channels in the plasma membrane (passive transport)
  3. Na-K pump (active transport)
40
Q

What does the sodium-potassium pump do?

A

uses ATP to transport Na+ ions out of the cells and K+ ions into the cells, results in an excess of positive charge accumulation outside the cell -> POLARIZED MEMBRANE

41
Q

Describe the DEPOLARIZATION process and how it is all or nothing.

A

occurs when membrane potential DECREASES, and inside of the cell becomes LESS NEGATIVE relative to the outside. The gates of K+ channels close and Na+ open, so more positive enters the cell.

a stimulus causes the axon to depolarize only if there is SUFFICIENT stimulus (greater than threshold) an impulse moves down the length of the axon (threshold must be reached, -50mV)

42
Q

When does REPOLARIZATION begin? Describe the process and what happens after?

A

The Na+ entering the cell (during depolarization) makes the potential difference around +40mV. Depolarization occurs for a split second, then the gates of K+ re-open and Na+ close at the same time.

K+ moves out until membrane potential becomes “HYPERPOLARIZED” -too negative and then the pump and some diffusion re-establish the polarity of that region

43
Q

Define “Action Potential”

A

in an axon, the change in charge that occurs when the gates of the K+ channels close and the gates of Na+ open after a wave of depolarization is triggered.

44
Q

What is the function of the gaps on myelinated neurons (Nodes of Ranvier)?

A

Nerve impulses jump from one node to another, action potentials are generated ONLY at the nodes of ranvier. Allows nerve impulses to be sent quicker along the length of an axon.

45
Q

Synapse (definition, purpose)

A

Since neurons do not touch each other, they communicate using the SYNAPSE between them.
Where signal transmission occurs

46
Q

Pre-synaptic Neuron (meaning)

A

carries a wave of depolarization towards a synapse (sends neurotransmitters to other neuron)

47
Q

Post-synaptic Neuron (meaning)

A

neuron that receives the stimulus

48
Q

Neurotransmitter (definition/purpose)

A

carry a nerve impulse across a synapse from one neuron to another. can either inhibit or excite the neuron.

49
Q

Briefly describe chemical signalling (across synapse)

A

Impulse carried down pre-synaptic axon, causes synaptic vesicles containing neurotransmitters to fuse with membrane. Then neurotransmitters exit using exocytosis into the synaptic cleft. Neurotransmitters bind to receptor proteins and affect post-synaptic neuron. Finally enzyme breaks up neurotransmitter and its components are reabsorbed by the presynaptic neuron

50
Q

Excitatory Neurotransmitter Response

A

opens Na+ gates, more likely to have action potential

51
Q

Inhibitory Neurotransmitter Response

A

makes postsynaptic neuron more negative, opens K+ channels causing hyperpolarization, less likely to have action potential

52
Q

Main Function of Endocrine System

A

secretes hormones (chemical messengers) into the blood to signal other cells to behave in certain ways, slower than nervous system but has longer lasting effects

53
Q

Endocrine Gland (function, examples)

A

secretes hormones into bloodstream
examples: pituitary, thyroid, parathyroid, and adrenal glands

54
Q

Hormone (function)

A

chemical messenger, sends signals
act on target cells to elicit a response

55
Q

Steroid Hormones vs Water-Soluble Hormones

A

Steroid: lipid-soluble molecules made from cholesterol
Water-soluble: derived from amino acids or chains of amino acids

56
Q

What is the master endocrine gland

A

the hypothalamus, located in brain, controls most endocrine secretions

57
Q

Trophic Hormones

A

hormones that affect the secretion of other hormones by acting on other endocrine glands

58
Q

Posterior pituitary (function/role)

A

considered part of the nervous system
stores and releases hormones that are produced in the hypothalamus. example: ADH

59
Q

Anterior pituitary (function/role)

A

hormone synthesizing gland, makes hormones, stores and secretes them into bloodstream. example: TSH, hGH

60
Q

Human Growth Hormone (function, disorders, etc)

A

-regulated by anterior pituitary
-stimulates growth of bones, tissues, and muscles
-most of its effects are tropic
-increases protein synthesis, cell division and growth
-too much in childhood: gigantism
-too little in childhood: pituitary dwarfism
-too much in adulthood: acromegaly

61
Q

Thyroid Gland (structure, function)

A

-Butterfly shaped gland below larynx
-controls metabolism/rate chemical rxns occur in body
-example: thyroxine

62
Q

What happens when high levels of thyroxine/T4 is secreted?

A

sugars and other nutrients oxidize at a faster rate, individuals tend to not gain weight

63
Q

What happens when lower levels of thyroxine/T4 is secreted?

A

nutrients are not oxidized as quickly and therefore sugars tend to not break down quickly and is eventually turned to fat. individuals tend to experience weight gain, muscle weakness, and cold intolerance.

64
Q

HypOthyroidism (thyroid activity, symptoms)

A

Thyroid under activity
-weak/slow heartbeat
-muscular weakness/constant fatigue
-sensitivity to cold
-thick puffy and/or dry skin
-slowed mental processes and poor memory
-constipation

65
Q

HypERthyroidism (thyroid activity, symptoms)

A

Thyroid over activity
-rapid/forceful heartbeat
-tremor
-muscular weakness
-weight loss in spite of increased appetite
-restlessness, anxiety, and sleeplessness
-profuse sweating and heat intolerance
-diarrhea
-eye changes
-GOITRE (increased size of the thyroid)

66
Q

Describe negative feedback system of thyroid hormones

A

-receptors in hypothalamus activate if there is decreased metabolic rate
-nerve cells in hypothalamus secrete TRH, which stimulates pituitary to release TSH
-TSH is carried in blood to the thyroid gland, which releases thyroxine/T4
-Thyroxine raises metabolism by stimulating increases sugar utilization/cell respiration
-Higher levels of thyroxine INHIBITS release of TRH, thus stopping production of TSH as well.

67
Q

Goitres (cause, definition)

A

-caused by low iodine concentration (key component of both thyroid hormones)
-results in enlargement of thyroid gland
-Thyroxine production stops, more TSH produced, no negative feedback, thyroid overstimulated so cells continue to grow and thyroid enlarges

68
Q

Calcitonin (function)

A

-assists in regulation of calcium levels in blood
-secreted by thyroid gland if blood Ca2+ is too high
-goes to bones, bones take Ca2+ from blood

69
Q

Parathyroid Hormone/PTH (function)

A

-maintains calcium levels in blood
-parathyroid gland releases PTH into blood if blood Ca2+ is too low
-PTH causes blood, kidneys, and digestive tract to absorb Ca2+

70
Q

What happens when blood glucose levels are high (after eating)?

A

-pancreas secretes insulin
-liver stores glucose as glycogen, muscle cells store glycogen and build protein, fat storing tissue uses glucose to form fat
-blood glucose levels return to normal

71
Q

What happens when blood glucose levels are low (between eating)?

A

-pancreas secretes glucagon
-fat storing tissue breaks down fat to glucose, liver breaks down glycogen to glucose
-blood glucose levels return to normal

72
Q

Short-term stress response

A

Fast, so nerve impulse is sent to adrenal medulla which secretes epinephrine and norepinephrine
-heart rate and blood pressure ↑
-breathing rate ↑
-blood glucose ↑
-rate of cellular metabolism ↑

73
Q

Long-term stress response

A

neurosecretory cells in hypothalamus produce releasing hormone, anterior pituitary secretes ACTH, adrenal cortex secretes glucocorticoids and mineralocorticoids
-blood pressure ↑
-blood glucose ↑
-inflammation ↓
-immune system ↓

74
Q

Diabetes (definition, cause, types)

A

-Caused by insufficent production or use of insulin
-excess blood glucose appears in urine and water follows = excessive urination

Type 1: insulin dependent, unable to produce insulin

Type 2: decreased production of insulin/ineffective use of insulin (doesn’t work)

Gestational Diabetes: temporary, occurs in some pregnancies

Biology - SBI4U (4 decks)

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