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BIO IB > Unit 10: Coordination and Control > Flashcards

Unit 10: Coordination and Control Flashcards

1
Q

What is system integration and what does it depend on?

A

Within these systems, there are interdependent subsystems that work together to perform an overall function. At every level in the functioning of an organism, there must be coordination between and within systems.

System integration depends on eective communication between components
so they can interact. The interactions may be as simple as negative or positive
feedback between two components. More commonly however, they are
complex and multifactorial, with many loops and branches.

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2
Q

What are the component subsystems of a cell?

A

Organelles

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3
Q

What is a tissue? What are the component subsystems of a tissue? How do these subsystems work together?

A

A group of cells
(component subsystem = cells)

–> cells within tissues stick to each other
—-> plant cells: a middle lamella between cell walls that is rich in gluey pectin
—-> animal cells: transmembrane proteins that form strong links between neighbouring cells

cells within a tissue communicate with each other.

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4
Q

What is an organ? What are the component subsystems of an organ? How do these subsystems work together?

A

A group of tissues that work together to carry out a specific function of life
(component subsystem = tissues)

–> tissues within an organ are interdependent

i.e. spongy mesophyll: adapted for gas exchange, palisade mesophyll: adapted for photosynthesis

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5
Q

What is an organ system? What are the component subsystems of an organ system? How do these subsystems work together?

A

A group of organs interacting with each other to perform an overall function of life.
(component subsystem = organs)

HUMAN ORGAN SYSTEMS:
circulatory, digestive, endocrine, gas exchange, integumentary, lymphatic, muscular, nervous, reproductive, skeletal, urinary

usually organs within organ systems are physically linked

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6
Q

What is an organism? What are the component subsystems of an organism? How do these subsystems work together?

A

A living individual made up of interconnected parts.

–> parts are interdependent so failure of a single group of cells in a tissue can cause an organism to die

i.e. a cheetah becomes an effective predator by integration of its body systems

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7
Q

Describe hormonal signalling in the endocrine system

A
  • Type of signal: Chemical
  • Transmission of signal: in the bloodstream
  • Destination of signal: widespread (all parts of body that are supplied w/ blood)
  • Effectors: target cells in any type of tissue
  • Type of response: growth, development (puberty), reproduction (gamete production and pregnancy), metabolic rate + heat generation, solute conc. in blood, mood
  • Speed of response: slower
  • Duration of response: long (until hormone broken down)
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8
Q

Describe nervous signalling in the neurons

A
  • Type of signal: Electrical (by passage of cations across membranes)
  • Transmission of signal: in neurons
  • Destination of signal: highly focused (to one specific neuron/group of effector cells)
  • Effectors: muscles or glands
  • Type of response: responses due to contraction of muscle, i.e. striated muscle (locomotion), smooth muscle (peristalsis + sphincter opening and closing), cardiac muscle (heart rate)
  • Speed of response: very rapid
  • Duration of response: short, unless nerve impulses are sent repeatedly
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9
Q

What is the role of the brain?

A

The brain is the central integrating organ of our body. It receives information,
processes it, stores some of it and sends instructions to all parts of the body to
coordinate life processes.

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10
Q

What is the role of the spinal cord? What makes up the spinal cord?

A

The spinal cord is located inside the vertebral
column (backbone). It is widest at its junction with the brain and tapers going downwards towards the pelvis. Pairs of spinal nerves branch off to the left and right between the vertebrae. In humans, there are 31 pairs of spinal nerves, each serving a different region of the body.

Consists of 2 parts:
1. White matter = myelinated axons + other nerve fibres, convey signals from sensory receptors to the brain and from the brain to the organs of the body
2. Grey matter = cell bodies of motor neurons and interneurons, with many synapses between these neurons (used for processing information and for decision making)

Spinal cord is an INTEGRATING CENTRE, and only coordinates UNCONSCIOUS PROCESSES, especially reflexes

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11
Q

What is the difference between unconscious and conscious processes?

A

UNCONSCIOUS:
* Performed when awake or asleep
* Performed involuntarily
* Secretion by glands and contractions of smooth muscle (not attached to bone) are unconscious and therefore involuntary
* Coordinated by brain AND spinal cord
* i.e knee reflex, or vomiting when stomach contents are regurgitated

CONSCIOUS
* Performed when awake only
* Performed voluntarily
* Contraction of striated muscle (attached to bone) are conscious and therefore voluntary
* Coordinated only by brain
* i.e. lifting something, or initiation of swallowing when food is pushed from mouth cavity into pharynx

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12
Q

What is a non-binary action?

A

We may consciously choose to carry out the actions but the processing then used is unconscious (i.e. we consciously choose to stand up and use striated muscles for this, but then unconscious postural reflexes keep up standing use the same muscles)

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13
Q

Explain the input to the spinal cord and cerebral hemispheres through sensory neurons. Also explain the output from the cerebral hemispheres
to muscles through motor neurons

A

sensory receptors –> sensory neurons –> CNS –> motor neurons –> effector organs

External
Touch, heat, light

Internal
Stretch, chemoreceptors

different parts of the brain affect different organs via motor.

Many neurons have their cell bodies located in the same part of the brain, but their axons and terminals attach to very different effector organs

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14
Q

What are nerves?

A

Nerve = bundle of nerve fibres surrounded by a sheath

–> contains both sensory and motor neurons (each can only transmit signals one way)

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15
Q

Explain a pain reflex arc

A

= involuntary response with skeletal muscle as the effector

  1. RECEPTORS
    sense a stimulus
  2. SENSORY NEURONS
    receive signals from receptor cells/own sensory nerve endings
  3. INTERNEURON
    (outside CNS) neurons that go between sensory and motor neuron
  4. MOTOR NEURON
    receive signals via synapses with interneurons
  5. EFFECTORS
    carry out response to stimulus when signal from a motor neuron is received
    –> 1. MUSCLES - contract
    –> 2. GLANDS - secrete
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16
Q

What is a cerebellum and what is its role

A

The little bit on the bottom back of the brain, near the start of the spinal cord

Coordinates the timing of muscle contraction, helps with coordination of movements, balance, posture, and things that require muscle memory

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17
Q

What is melatonin/circadian rhythms?

A

Circadian rhythms = pattern of sleep/wake cycles that organisms are adapted for

Melatonin = hormone secreted by the PINEAL gland in the brain that controls circadian rhythms
–> inhibited by light but produced in the dark
–> causes drop in temperature, drowsiness, sleep
–> integrated with a sensory neuron in the eye that senses light

Light receptor –> CNS –> pineal gland

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18
Q

What is ephinephrine and what is its role and effects?

A

Epinephrine = adrenaline

secreted by adrenal glands on top of kidney

Hormone to prepare for vigorous activity (fight or flight hormone)
–> to increase glucose and oxygen supply to skeletal muscles

EFFECTS
–> hydrolysis of glycogen –> glucose
–> increased diameter of bronchi and bronchioles
–> ventilation rate and tidal volume increases
–> sinoatrial node increases heart rate
–> increase blood flow to liver and muscles (vasodilation)
–> decrease blood flow to gut and kidneys (vasoconstriction)

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19
Q

What are the hypothalamus and the pituitary gland

A

INPUT—-
HYPOTHALAMUS - small region of the brain
–> attached to the pituitary gland, connects the nervous + endocrine system
–> receives input from other parts of the brain and sensors for temp, blood glucose and solute conc.

OUTPUT—–
PITUITARY GLAND - releases hormones
–> ANTERIOR LOBE - FSH, LH
–> POSTERIOR LOBE - Oxytocin

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20
Q

Explain osmoregulation and puberty in terms of system integration

A

OSMOREGULATION:
- senses solute concentration/osmolarity
- prompts pituitary to release antidiuretic hormone to increase reabsorption of water in kidneys

PUBERTY
- hypothalamus will release GnRH
- prompts pituitary to release FSH and LH to initiate puberty

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21
Q

Explain the feedback control of the heart rate

A

SA node is connected to the medulla oblongata by the vagus and sympathetic nerves. can only transmit nervous impulses towards the SA node

Baroreceptors and chemoreceptors both in carotid artery walls, BR monitoring blood pressure and CR monitoring pH + blood oxygen concentration

BR = inc. heart rate when pressure is low
CR = inc. heart rate when pH and oxygen conc. is low

Vagus nerve = slow down heart rate
Sympathetic nerve = increase heart rate

EPINEPHRINE CAN OVERRIDE THESE

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22
Q

Explain feedback control of ventilation rate following sensory input from chemoreceptors

A

normal pH of blood = 7.35-7.45

IF ACTIVITY ↑
- respiration ↑, CO2 ↑, pH ↓
- when pH ↓, causes nerve signals to be transmitted to diaphragm and intercostals, which control breathing (ventilation rate increases)

Negative feedback loop (when pH ↓, ventilation rate ↑

measure ventilation rate using spirometer

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23
Q

Explain the control of peristalsis in the digestive system by the CNS and the enteric nervous system

A

Peristalsis: muscle contractions that move food through the digestive tract

Voluntary digestive movements controlled by CNS
- initiation and swallowing
- defecation (after potty-trained)

Involuntary and controlled by ENS (nerves that connect to digestive system)
- peristalsis
- defecation (before potty trained)

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24
Q

What are tropisms and what types are there?

A

Tropism = growth response to stimuli

Positive tropism = growing towards stimulus

Negative tropism = growing away from stimulus

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25
Q

Explain positive phototropism

A

Positive phototropism = grow towards the highest light intensity in their environment

Benefit: increases the amount of light absorbed by a shoot’s leaves for use in photosynthesis

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26
Q

What is and what is the role/effects of a phytohormone?

A

Phytohormone = plant hormone that helps control growth, development and responses to stimuli in plants

  1. GROWTH
    - can either promote or inhibit growth by affecting rates of cell division and cell enlargement (i.e. gibberelin causing stem elongation)
  2. DEVELOPMENT
    - promote or inhibit aspects of development (i.e. ethylene ripens fruits)
  3. RESPONSE TO STIMULI
    - control tropisms (i.e. auxins control phototropism)
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27
Q

What is auxin and what is an auxin efflux carriers?

A

Auxin = phytohormone that promotes stem growth and causes differential growth response of phototropism.
- enter cells by passive diffusion as long as its carboxyl group remains undissociated

Auxin efflux carriers will move to the side that requires auxin, allowing auxin to be pumped into that side of the plant

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28
Q

Explain the promotion of cell growth by auxin

A

Auxin promotes proton pump synthesis in the cell walls (apoplast)
–> lowers pH of cell wall
–> weakens crosslinks between cellulose microfibrils within cell wall
–> cell wall can then elongate

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29
Q

Explain the interactions between auxin and cytokinin

A

Auxin is produced in shoot tips, transported down into roots in phloem

Cytokinin is produced in root and transported up into shoots in xylem.

If they work together, it is called synergism. Else: antagonism

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30
Q

Explain positive feedback in fruit ripening

A

When seeds are ready to be dispersed, the fruit ripens
- colour changes from green
- cell walls are partially digested, - softening fruit flesh
- acids and starch converted to sugar (palatable)
- volatile substances are synthesized to give fruit a distinctive scent

Positive feedback: ethylene stimulates ripening, ripening fruits produce ethylene.

Ethylene is also a gas –> so it affects nearby fruits

31
Q

Compare receptors and enzymes

A

SIMILARITIES:
1. binding of ligand/substrate occurs at the specific site
2. shape + chemical properties of the ligand-binding/active site match ligand/substrate, preventing other substances from binding
3. receptors/enzymes are unchanged by the binding of a ligand/substrate, even if temporary changes to induce fit

DIFFERENCES:
4. ligand released unchanged after bonded, but substrate is chemically converted into product and released

32
Q

What is quorum sensing? Explain its process and give an example

A

A change in the behaviour of a colony when its population density reaches a certain threshold

More cells = more chemical messenger molecules. At certain density, enough molecules have been received to cause a change in activity

= demonstrates interdependence

EXAMPLE: Vibrio fischeri –> bioluminescence
- when it reaches a certain population density, it will bioluminesce

33
Q

What are the differences between hormones, neurotransmitters, cytokines and calcium ions?

A

All are functional categories of signalling chemicals in animals

  1. HORMONES (i.e. insulin, glucagon, testosterone, estrogen)
    - come from endocrine glands
    - target cells have receptor proteins
    - long effect time
  2. NEUROTRANSMITTERS (i.e. dopamine, seratonin)
    - only travel in the synapse
    - isolated to just that nerve junction
    - short effect time, because they are quickly removed from synapse
  3. CYTOKINES (i.e. interferon)
    - proteins that act as chemical messages within cells/between nearby cells
    - can have multiple effects depending on binding site
  4. CALCIUM IONS
    - not a biological molecule
    - with muscle fibres = calcium ions bind to a protein on actin to allow myosin heads to attach
    - neurons = causes the release of neurotransmitters from the presynaptic neuron
34
Q

Explain the chemical diversity of hormones and neurotransmitters

A

Both are small, soluble, and have a shape compatible with a receptor.

HORMONES:
steroids, amines, peptides

NEUROTRANSMITTERS:
amines, amino acids, esters, gases

35
Q

Explain the localised and distant effects of signalling molecules

A

Hormones have effect over LARGE distances because they are travelling through blood

Neurotransmitters produce a localised effect between 2 neurons, because they are only travelling between 2 neurons

36
Q

What are the differences between transmembrane receptors in a plasma membrane and intracellular receptors in the cytoplasm or nucleus

A

INTRACELLULAR RECEPTOR:
Signalling molecule (steroid hormone) CAN enter the cell because it is hydroPHOBIC, so receptor protein is located IN the cytoplasm or nucleus (inside the cell), and have a surface of hydroPHILIC amino acids

TRANSMEMBRANE RECEPTORS:
Signalling molecule (non-steroid hormone) CANNOT enter the cell because it is NOT hydrophobic, so receptor protein is located ON the plasma membrane, has BOTH hydrophilic and hydrophobic amino acids

37
Q

What is a signal transduction pathway and how is it initiated by receptors? (transduction, intracellular, transmembrane pathways)

A

TRANSDUCTION:
sequence of interactions initiated by the ligand binding to receptor

TWO MAJOR TYPES OF TRANSDUCTION PATHWAYS:
1. INTRACELLULAR:
- ligand enters cell
- binds to receptor
- complex regulates gene expression

  1. TRANSMEMBRANE PATHWAY
    - ligand binds with the receptor
    - receptor changes shape
    - produces secondary messenger molecules
    - causes changes inside the cell
38
Q

What are transmembrane receptors for neurotransmitters and what are the changes to the membrane potential? (1st type of transmembrane receptors)

A

Neurotransmitters are released from the presynaptic neuron.

They bind to receptors on the post-synaptic neuron and cause sodium ion channels to open.

Sodium then enters the cell via facilitated diffusion.
–> changes the membrane potential from negative to positive

Example: acetylcholine is a messenger between neurons and muscle fibers

39
Q

What are transmembrane receptors that activate G proteins? (2nd type of transmembrane receptors)

A

GPCR: G-protein coupled receptor (transmembrane receptor protein)
GDP: guanosine DIphosphate
GTP: guanosine TRIphosphate

when GDP bound to G protein = inactive

when ligand binds to the receptor, GDP is replaced by GTP
–> protein complex activates, disassembles and causes changes within cells

40
Q

What is the mechanism of action of epinephrine receptors

A

Epinephrine = NON STEROID hormone produced in the adrenal glands, so cannot enter cell

when it binds with a G-protein, it causes a SECONDARY MESSENGER MOLECULE CASCADE – ATP to be converted into a secondary messenger molecule called cyclic AMP (cAMP)
- amplifies the effect

example: hydrolysis of glycogen –> glucose

41
Q

What are transmembrane receptors with tyrosine kinase activity (3rd type of transmembrane receptors)

A

Kinase: enzyme that phosphorylates molecules by removing a phosphate group from ATP and adding it to a molecule

Tyrosine Kinase: enzyme that transfers a phosphate group from ATP to tyrosine (a type of amino acid) in a protein

EXAMPLE:
binding of insulin to the transmembrane receptor protein

tyrosine kinase are the 2 tails that extend into the cytoplasm

-insulin cannot enter cell
-insulin binds to the receptor, the tyrosine kinase with join and this causes a conformational change in the proteins
-the vesicle that contains the proteins will fuse with the membrane (insertion of glucose transporters into the membrane
-glucose can move into the cell

42
Q

What are the intracellular receptors that affect gene expression

A

Intracellular receptors are hydrophobic so can enter the cell and bind to an intracellular receptor

The hormone receptor complex will attach to the DNA in the nucleus and changes gene expression

43
Q

What are the effects of oestradiol and progesterone on target cells?

A

OESTRADIOL
GnRH –> secretion of LH and FSH –> travel through bloodstream and target tissue = ovary –> when follicles are acted upon by these hormones, they secrete oestradiol

Oestradiol will travel BACK to hypothalamus and enter the hypothalamus cells, causing even more transcription and translation to take place –> MORE GnRH produced (positive feedback)

PROGESTERONE
target tissue in endometrium, progesterone will travel through bloodstream to these cells, will enter the cells and regulate genetic expression that thickens and intensifies nutrition value of endometrium

44
Q

Regulation of cell signalling pathways by positive and negative feedback

A

Negative feedback loop:
- to maintain stable conditions
- increasing concentrations of the end product inhibits further production
- example is testosterone
–> GnRH –> LH, travels via bloodstream to testes, triggering testosterone release –> travels to hypothalamus to INHIBIT GnRH production

Positive feedback loop:
- final product triggers more production of the product
- example: oestradiol
–> GnRH –> secretion of LH and FSH –> travel through bloodstream and target tissue = ovary –> when follicles are acted upon by these hormones, they secrete oestradiol

Oestradiol will travel BACK to hypothalamus and enter the hypothalamus cells, causing even more transcription and translation to take place –> MORE GnRH produced (positive feedback)

45
Q

What is a neuron and how do they work?

A

Neurons = cells within nervous system that carry electrical impulses

electrical impulses = electrical signal passed between 2 cells

46
Q

Explain the generation of the resting potential by pumping to establish and maintain conc. gradients of Na+ and K+ ions

A

membrane potential = voltage created by an imbalance of charges on either side of the membrane

at rest:
- inside of neuron is relatively negative (-70 mV [millivolts])
- Na+ are on the outside of the cell
- this is established by active transport (sodium potassium pump), requires ATP and generating a CONC. GRADIENT
–> sodium OUTSIDE and potassium INSIDE

47
Q

Explain nerve impulses as action potentials that are propagated along nerve fibres

A

depolarisation: membrane potential goes from negative to positive

–> ions into the cell
–> potassium ions will leave the cell afterwards

repolarisation: membrane potential goes from positive back to negative

–> when potassium ions leave the cell

sodium potassium pump will move the sodium ions out and potassium ions in

PROCESS:
1. voltage gated sodium ion channels open
2. sodium ions diffuse INTO the cell (facilitated diffusion)
3. depolarisation
4. voltage gated sodium ion channels close, and voltage gated potassium ion channels open
5. potassium ions diffuse out of the cell (facilitated diffusion)
6. repolarisation
7. sodium potassium pump re-establishes resting potential by actively pumping sodium ions out and potassium ions in

nerve transmission occurs starting from dendrites and along the axon to the terminal. depolarisation in one part triggers depolarisation in the next part due to the opening of voltage-gated channels. this is called SELF-PROPAGATION

48
Q

Explain the variation in the speed of nerve impulses

A

Average speed = 1m/s

to increase speed:
-larger axon diameter
-myelination
–> myelin sheath (the little knobs on the axon

MYELINATED VS NON-MYELINATED NEURONS
–> saltatory conduction occurs only in MYELINATED CONDUCTION
–> myelin sheath insulates the electrical impulse, so it only has to jump from node to node
–> 1 to 100m/s

49
Q

What are synapses and what is the role of them

A

Synapse = gap between cells through which signals are passed by neurotransmitters

only 20nm wide

occur between neurons and between neurons and effectors

50
Q

Explain the process of the release of neurotransmitters from a presynaptic membrane

A
  1. Action potential (wave of positive voltage) reaches the end of the presynaptic neuron
  2. Voltage gated calcium ion channels open
  3. Calcium ions enter the presynaptic neuron (facilitated diffusion)
  4. Ions force vesicles with neurotransmitters to fuse with the membrane
  5. Neurotransmitters released into the synapse (exocytosis)
  6. Neurotransmitters diffuse across synapse
  7. Bind to receptors on the postsynaptic membrane
  8. Ion channels open
  9. If enough ions enter the postsynaptic cell, that generates an action potential
  10. Neurotransmitter is removed from the synapse (either destroyed or moves back into presynaptic neuron)
51
Q

Explain the generation of an excitatory postsynaptic potential

A

Acetylcholine - responsible for carrying messages between neurons and muscles

Enzyme that breaks down acetylcholine = acetylcholinesterase
–> breaks down to acetyl and choline
–> choline is reabsorbed by the presynaptic neuron to make more acetylcholine

52
Q

Explain the depolarisation and repolarisation during action potentials

A

Threshold potential = the membrane potential that must be reached in order for the voltage gated ion channels to open (-50mV)

When sodium diffuses into the neuron, a wave of ion-channel openings occurs further down the axon

53
Q

Explain the propagation of an action potential along a nerve
fibre/axon as a result of local
currents

A

local current = movement of sodium ions between polarised and depolarised regions

54
Q

What can you use to measure membrane potentials?

A

Oscilloscope = can measure membrane potentials using electrodes

55
Q

What is saltatory conduction?

A

Occurs in myelinated sheaths, means the jumping of the nerve impulse from node to node to increase speed of impulses

1m/s to 100m/s

56
Q

Explain the effect of exogenous chemicals on synaptic transmission

A

Exogenous chemical = something that enters the body from an external source

can affect synaptic transmission (block or promote)

EXAMPLES
neonicotinoids:
insecticides/pesticides
–> binds to acetylcholine receptors, so cannot bind
causes paralysis and death
1. pros: does not affect humans
2. cons: affects non-pest species (like bees)

cocaine:
-blocks the reuptake mechanism for dopamine to the presynaptic neuron
-dopamine builds up
-too many dopamine messages
-stimulant/feelings of euphoria

57
Q

What are inhibitory neurotransmitters and explain the generation of inhibitory postsynapticpotentials

A

Some neurotransmitters make the membrane even more negative (hyperpolarized), making it harder for nerve impulses to be sent

Acetylcholine is an excitatory neurotransmitter. Gaba is an inhibitory neurotransmitter.

58
Q

What are summation of the effects of excitatory and inhibitory neurotransmitters in a postsynaptic neuron

A
  • an excitatory neurotransmitter from one presynaptic neuron is usually not enough to reach threshold potential in the postsynaptic neuron
    SUMMATION: when multiple releases of an excitatory neurotransmitter are needed to cause an action potential in the postsynaptic neuron
    -> neurotransmitters from diff neurons OR
    -> several neurotransmitters from the same neuron

excitatory neurotransmitters MUST OUTNUMBER inhibitory neurotransmitters in order to reach threshold potential

59
Q

explain the perception of pain by neurons with free nerve endings in the skin

A

sensory neurons have endings in the skin.

action potential is initiated in response to pain

carries the impulse to the spinal column, then to the brain

brain sends an impulse along motor neurons to affect behaviour

60
Q

discuss consciousness as a property

A

consciousness is a property that emerges from the interaction of individual neurons in the brain.

–> simultaneous awareness of many different things

Sleep = reduced consciousness
Anesthesia = unconsciousness

61
Q

What is homeostasis?

A

Maintaining stable internal conditions regardless of fluctuations in the external environment

examples = body temp, blood pH

62
Q

Explain the negative feedback loops in homeostasis

A

Homeostasis utilises negative feedback loops and uses energy but allows organisms to make use of a wider range of habitats

63
Q

Explain blood glucose regulation as an example of the role of hormones in homeostasis. Which cells secrete the glucagon and insulin?

A

Cells of the pancreas
-> exocrine glands = secrete substances through a duct
-> endocrine glands = secrete hormones into the bloodstream
—> α cells = glucagon (secreted when low blood glucose levels)
——> stimulates conversion of glycogen to glucose
——> glucose levels return to normal

—> β cells = insulin (secreted when high blood glucose levels)
——> opens glucose channels to allow for uptake
——> stimulates conversion of glucose to glycogen
——> glucose levels return to normal

64
Q

Describe the physiological changes that form the basis of type 1 and type 2 diabetes

A

Diabetes = chronically elevated blood glucose levels

TYPE I
- Immune system attacks β cells, so little to no insulin is produced
-> autoimmune
to treat: insulin injections

TYPE II
- Decreased sensitivity to insulin due to lack of insulin receptors
-> caused by lifestyle and genetics
to treat: dietary changes to avoic peaks + exercise

65
Q

What is thermoregulation?

A

peripheral thermoreceptors in the skin and central thermoreceptors predict temperature changes.

hypothalamus monitors and interprets information from thermoreceptors and initiates a response

TRH = thyrotropin releasing hormone
TSH = thyroid stimulating hormone
Thyroxine = a hormone that increases cellular metabolism (respiration)

@ LOW TEMP
-> Hypothalamus secretes TRH
-> Pituitary secretes TSH
-> Thyroid secretes Thyroxine
-> Cellular metabolism increases, causing temp to increase

Endocrine tissues:
Muscle tissues: contractions generate heat
Adipose tissues (fat cells): insulator to prevent heat loss , respiratory substrate for heat generation (respiration)

66
Q

describe thermoregulation mechanisms in humans

A

If COLD:
- shivering
- erection of hair
- vasoconstriction (reducing blood flow to skin)
- uncoupled respiration in brown adipose tissue
–> No ATP produced, only heat

If HOT:
- sweating
–> water has a high latent heat of vapourisation
–> controlled by hypothalamus
- vasodilation
–> increases blood flow to skin

67
Q

Explain the role of the kidney in osmoregulation and excretion

A

Osmoregulation = Keeping the osmotic concentration of body fluids within narrow limits
–> Kidney carries out osmoregulation by varying the relative amounts of water and salts that are removed from the body in urine.

Excretion = The removal of toxic waste products of metabolism from the body.
–> kidney removes substances like urea

68
Q

What is the role of the glomerulus, Bowman’s capsule and proximal convoluted tubule in excretion?

A

Glomerulus = fenestrated capillaries that allows filtrate to be separated from blood

Bowman’s capsule = captures filtrate from the glomerulus

Proximal convoluted tubule = site of selective reabsorption

69
Q

What is ultrafiltration

A

Afferent arteriole > efferent arteriole
Creates high pressure, forces molecules out of the glomerulus, glomerular filtrate captured by Bowman’s capsule
Based on size and charge (not selective)

70
Q

What is selective reabsorption

A

Recapture molecules from ultrafiltration
- sodium ions (active transport)
- chloride ions (active transport)
- water (osmosis)
- glucose (using cotransporter proteins by facilitated diffusion)

special adaptations for this: microvilli (larger surface area), mitochondria (produce atp for active transport)

molecules not reabsorbed:
- urea and other toxins
- salt
- water

71
Q

What is the role of the loop of Henle

A

Medulla has high solute concentration

Descending limb
- water exits via osmosis

Ascending limb
- not permeable to water
- sodium ions leave filtrate (active transport)

72
Q

Explain osmoregulation by water reabsorption in the collecting ducts

A

Hypothalamus monitors osmotic concentration in blood

  • can trigger the pituitary to release ADH (or not)

ADH = antidiuretic hormone (increases permeability of the collecting duct by moving aquaporins to cell surface)

So, when dehydrated, more ADH, more water leaves filtrate, more concentrated urine. Hydrated, NO ADH.

73
Q

Describe the changes in blood supply to organs in response to changes in activity

A

Arterioles:
Vasoconstriction = reduce blood flow
Vasodilation = increase blood flow

BLOOD FLOW
1. SLEEP
Brain: high
Skeletal muscle: low
Digestive system: variable
Kidneys: low

  1. RESTING BUT AWAKE
    Brain: moderate
    Skeletal muscle: moderate
    Digestive system: variable
    Kidneys: very high
  2. EXERCISE
    Brain: high
    Skeletal muscle: very high
    Digestive system: low
    Kidneys: low
74
Q
A

BIO IB (12 decks)

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