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communication and homeostasis Flashcards

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1
Q

features of a good communication system

A

cover the whole body so the action of all cells and tissues can be co-ordinated
enable localised communication between cells
enable long distance communication between cells (widespread)
enable specific communication (targets specific cells to respond only)
be rapid (allowing fast response to rapid changes)
enable long term responses (more hormonal)
enable short term responses (more neuronal)

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2
Q

how do cells communicate with each other

A

cell signalling
2 communication systems: neuronal and hormonal
communicate to create a co-ordinated response
identify/recognise each other via cell signalling

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3
Q

cell signalling neuronal vs hormonal

A

both involve cell signalling molecules which are complementary to the shape of their receptor molecules on the cell surface membrane
neuronal often short term
hormonal long term

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4
Q

what may a cell signalling molecule be

A

protein
amino acid
lipid
glycoprotein
another organic chemical

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5
Q

examples of cell signalling molecules

A

hormones
antibodies
histamines
cytokines like interleukins

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6
Q

example of cell signalling from communicable diseases

A

in immune response, T helper cells bind to specific APCs (clonal selection) before clonal expansion is triggered by cytokine interleukin 1
T helper cells then bind to specific B lymphocytes stimulating plasma cell production by cytokine interleukin 2

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7
Q

what is the nervous system

A

interconnected network of neurones that signal to each other across synapses via neurotransmitters

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8
Q

what are neurones

A

specialised cells which can conduct electrical impulses very quickly to enable rapid responses e.g. reflexes

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9
Q

what do cells within endocrine glands release

A

hormones directly into the blood

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10
Q

what is a hormone

A

a chemical messenger which has a specific shape that is recognised by specific target cells

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11
Q

hormonal system: long or short term responses?

A

both

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12
Q

example of LT hormone response

A

LT stress response e.g. illness or injury. body cannot sustain bursts of energy mediated by adrenaline and noradrenaline so other hormones e.g. cortisol are important.
cortisol affects cellular metabolism leading to stimulation of glucose synthesis

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13
Q

nervous control vs hormonal control:
transmission

A

N: elec and chem transmission (nerve impulses and chemicals across synapses)
H: chem transmission (hormones) through blood system

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14
Q

nervous control vs hormonal control:
speed

A

N: rapid transmission and response
H: slower transmission and relatively slow-acting (adrenaline is an exception)

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15
Q

nervous control vs hormonal control:
ST/LT

A

N: often short term changes
H: often long term changes

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16
Q

nervous control vs hormonal control:
pathway

A

N: pathway is specific (through nerve cells)
H: pathway not specific (blood around whole body) but is target specific

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17
Q

nervous control vs hormonal control:
size of response

A

N: responses often v localised e.g. one muscle
H: response may be very widespread e.g. growth

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18
Q

nervous control vs hormonal control:
cell signalling molecules

A

both involve cell signalling molecules which are complementary to the shape of the receptor they interact w
both work together for the co-ordinated responses in the body e.g. in fight/flight response, sympathetic nervous system stimulates adrenal gland to release adrenaline

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19
Q

cell signalling definition

A

the process bay which cells communicate with each other for co-ordination of bodily functions
cell recognition
cells work together
trigger reaction inside of target cell
e.g. hormone

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20
Q

explain how a glycoprotein can act as a receptor

A

cell signalling molecule binds to a complementary receptor (complementary to shape of ligand) e.g. hormones/ neurotransmitters to trigger a response
may be involved in endocytosis
has a specific shape

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21
Q

outline 3 roles of glycoproteins in membranes

A

allow for recognition of ‘self’ by the immune system
act as antigens
stabilises membrane forming H bonds w/ H2O molecules
act as receptors for cell-signalling molecules
binding sites for hormones

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22
Q

examples of changes to the internal environment

A

blood glucose concentration
water potential of blood
internal temperature
pH of blood
blood pressure

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23
Q

examples of changes to the external environment

A

humidity
light intensity
external temperature
new/sudden sound
pressure on skin

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24
Q

what’s another word for an environmental change

A

stimulus

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25
what's another word for a change in behaviour
response
26
examples of responses to external stimuli
seasonal change in temperature causes thick fur development of rabbits (white and brown) appearance of predator/prey causes fight/flight and hormone release
27
give 2 reasons why both plants and animals need to be able to respond to changes in their environment
to avoid being eaten and to obtain access to resources
28
state an organ that is associated with maintaining the internal environment of a mammal and state the role it plays
pancreas releases insulin to regulate and maintain blood glucose levels
29
definition of homeostasis
maintenance of a stable internal environment around a set point despite internal/ external environmental changes
30
what does homeostasis include
thermoregulation blood glucose concentration blood salt concentration water potential of blood blood pressure blood pH (conc of CO2)
31
what is the thermoregulation important for
enzyme activity
32
why is controlling blood glucose level necessary
needed for respiration affects water potential
33
why is controlling blood salt concentration necessary
affects the water potential affects blood pressure
34
why is controlling water potential of the blood necessary
it affects blood pressure
35
why is controlling blood pressure necessary
ensures blood delivered efficiently and without damage to walls of blood vessels/ heart
36
why is controlling blood pH necessary
decreases pH which affects enzymes
37
what is feedback
when effectors bring about a response they change the condition in the body and this new condition will be detected by receptors (i.e. the input has changed) which in turn will affect the response
38
what is negative feedback
a change initiates a series of events and negative feedback is a mechanism that reverse the change bringing the system back to optimum
39
what is overshoot in a homeostatic mechanism
it takes time to respond to a stimulus and the response may cause an overshoot and so homeostasis involves fluctuations around the optimum
40
what does negative feedback ensure
conditions inside a living organism remain within a relatively narrow range
41
what is overshoot minimised by
gradually cutting off corrective mechanisms quick response antagonistic control
42
positive feedback details
the mechanism that increases a change, taking the system further away from the optimum tends to be harmful, but not always not involved in homeostasis
43
examples of positive feedback
opening of channels in neurones blood clotting during hypothermia during birth
44
examples of positive feedback: opening of channels in neurones
Na+ enters the axon due to stimulus potential difference becomes less negative voltage gated Na+ channels open more Na+ enters action potential fired
45
examples of positive feedback: blood clotting
platelets attract more platelets which accelerates clotting
46
examples of positive feedback: during hypothermia
body temp drops enzymes become less active exergonic metabolic reactions slower less heat released temp drops further enzyme activity decreases further temp decreases further
47
examples of positive feedback: during birth
cervix dilates pituitary gland releases oxytocin oxytocin increases uterine contractions this stretches the cervix further causes more oxytocin release causing more contractions
48
inflammation response involving cell signalling
mast cells release histamines and cytokines these attract neutrophils and macrophages and T helper cells histamines make blood vessels more permeable and make arterioles vasodilator more tissue fluid formed pain, heat, redness and swelling occur heat prevents pathogen reproduction
49
how could rhodniin (prevents action of thrombin) enable an insect to continuously feed on the blood of its prey
thrombin is involved in the cascade activation for blood clotting, so inhibiting it will mean fibrinogen is not converted to fibrin, so blood remains liquid and wound exposed
50
what are plasmodesmata
adhesion between plant cells is mediated by their cell walls- in particular a specialised pectin-rich region of the cell wall called the middle lamella which acts asa. flue to hold adjacent cell walls together
51
how do adjacent plant cells communicate with each other
via cytoplasmic connections called plasmodesmata plasmodesmata are dynamic structures and they can open or close in response to specific stimuli allowing regulated passage of macromolecules between cells
52
plasmodesmata diameter
40nm
53
number of plasmodesmata between a pair of neighbouring cells
between 1000 and 100000
54
when and how do plasmodesmata form
during cell division parts of the endoplasmic reticulum of the parent cell get trapped in the new cell wall that is produced to create new daughter cells
55
role of cells by plasmodesmata
control the permeability/diameter of plasmodesmata
56
types of junctions between adjacent animal cells
tight gap adherens desmosomes
57
what type of junction is this
gap junction
58
what type of junction is this
tight junction
59
what type of junction is this
adherens
60
what type of junction is this
desmosomes
61
description of tight junction
cells are tightly held against each other by many individual groups of tight junction proteins called claudins, each of which interacts with a partner group on the opposite cell membrane
62
description gap junction
develop when a set of 6 membrane proteins called connexions form an elongated, donut-like structure called a connexon when they align w those of adjacent animal cells, a channel forms between the cells
63
description adherens
built from cadherins (transmembrane proteins) and catenins (connected to actin filaments)
64
desmosomes description
cadherins (specialised adhesion proteins) are found on the membranes of both cells and hold the membranes together
65
tight junction function
create a watertight seal between 2 adjacent animal cells (keep liquid from escaping between cells)
66
gap junction function
allow for transport of ions, water and other substances between animal cells important in cardiac muscle for synchronised contraction
66
adherens function
provide strong mechanical attachments between adjacent cells hold cardiac muscle cells together as heart expands and contracts repsonsible for contract inhibition
67
desmosomes function
act like spot welds between adjacent epithelial cells involves a complex of proteins pin adjacent cells together ensuring cells in organs and tissues that stretch e.g. skin and cardiac muscle , remain connected in an unbroken sheet
68
why is it necessary to control body temperature?
optimum temp for enzyme activity molecules have more kinetic energy so increased frequency of successful collisions so increased rate of reaction (Q10=2)
69
what does increasing body temperature do (hyperthermia etc)
if temperature increases too much, enzymes denature so rate falls too high- hyperthermia: cellular respiration fails to work, leading to organ failure. initially, patient may have hot dry skin and reduction in BP, increased HR and nausea, vomiting and headaches
70
what does decreasing body temp do (hypothermia etc)
too low=hypothermia (pale blue, cold skin and shivering) Q10=2 so if temp drops 10 degrees, enzymatic reactions fall by 1/2 POSITIVE FEEDBACK LOOP so get colder
71
core temperature definition
operating temperature inside the body
72
peripheral temperature definition
temperature of skin
73
core vs peripheral temperature
core temp maintained close to set point peripheral temp is more variable and influenced by the environment
74
conduction definition
transfer of heat from hotter to cooler objects in contact heat energy can also be conducted to surrounding medium eg air
75
convection definition
warmer air is less dense and so will rise through surrounding cooler air, creating air currents convection speeds up loss of energy from objects by conduction and evaporation
76
radiation definition
transfer of heat energy from a body to colder objects that are not in contact with each other heat energy is transferred by infrared waves
77
evaporation definition
change of a liquid to a vapour which is accompanied by a cooling e.g. sweating, wallowing, respiratory surfaces can only lose heat by this method
78
what is an endotherm
organism that uses heat from metabolic reactions to maintain body temperature so have a higher metabolic rate
79
what is an ectotherm
organism that relies on external source of heart to maintain body temperature
80
endotherm example
mammals
81
ectotherm examples
fish reptiles amphibians some insects
82
endotherm vs ectotherms temp range
endotherms control body temp within strict limits ectotherms are not able to control body temp internally so cannot increase metabolism to increase temperature
83
endotherm controlling body temp mechanisms
use a variety of mechanisms: physiological and behavioural
84
ectotherm controlling body temp
fluctuates with external temperature
85
endotherms activity level impacting temp
activity level is largely independent of external temperature
86
ectotherms activity level impact on body temp / vice versa
activity level depends on external temp: more active at higher temps as enzymes at optimum
87
ectotherms niche?
often exploit a narrower niche
88
what do ectotherms do if they are too cold
try to absorb more heat from environment: move to sunny area and bask in the sun lie on a warm surface e.g. a rock expose a larger SA to sun/warm surface move around to generate some heat
89
what do ectotherms do if they are too hot
try to avoid gaining more heat or increase heat loss to the environment: move out of sun and seek shade move underground into burrow decrease SA exposed to sun/warm surface increase rate and depth of breathing so more water evaporates (open buccal cavity to expose moist surface)
90
advantages of being an ectotherm
lower respiratory rate required less food required more of their food converted to growth can survive longer without food
91
disadvantages of being an ectotherm
can be more vulnerable to large fluctuations in environmental temp cannot exploit as many locations more susceptible to predation if less active less active at colder temps: limits their activity level
92
why do lizards bask in the sun w their mouths open
buccal cavity open so more water evaporates so more heat loss lizard doesn't overheat (temp control)
93
suggest why aquatic organisms have relatively few problems in maintaining a stable body temp
water has a high SHC so its temp remains relatively constant, providing a stable habitat where ectotherms remain at a relatively stable temp
94
role of peripheral temperature receptors
detect changes in temp of skin and send impulses to hypothalamus give early warning that body temp may be about to change
95
how does the hypothalamus work as a thermoregulatory centre?
monitors temp of blood flowing through it using thermoreceptors receives impulses from peripheral thermoreceptors in the skin send impulses via motor neurones to sweat glands, muscles in arterioles, skeletal muscles and hair erector muscles increase metabolism to increase exergonic reactions so more heat released (increase TRH->TSH->thyroid gland->thyroxine)
96
what is the blood supply in sweat glands for
supplies the fluid for making sweat
97
why do sweat glands have a sympathetic nerve
part of autonomic nervous system (motor neurones)
98
why is there smooth muscle in the walls of arterioles supplying capillaries in the skin
contract to cause vasoconstriction (less blood flow to skin so less heat loss by radiation) relax to cause vasodilation (more blood flow to skin so more heat loss by radiation)
99
what are shunt vessels and their role in heat loss
allow blood to bypass capillaries in the surface of the skin so less heat is lost
100
role of erector muscles in thermoregulation
contract and pull on the base of hair follicle to stand up and trap air, acting as an insulator so less heat lost (air trapped between hairs, a poor conductor of heat so insulates the body)
101
role of shivering in thermoregulation
muscles contract, respiring which is an exergonic reaction so releases heat
102
vasodilation mechanism
if core temp starts to increase, smooth muscle in arteriole walls relaxes and arteriole dilates more blood flows through the capillaries near the surface of the skin this increases the rate of heat loss from the body
103
vasoconstriction mechanism
if core temp of body starts to decrease, smooth muscle in the arteriole walls contracts which constricts the arteriole less blood flows through the capillaries close to the surface of the skin bc blood is redirected through the shunt vessels (deeper layers of skin) reduces rate of heat loss from the body
104
suggest why the ear provides a more accurate measurement of body temperature than the skin surface
ear is close to/shares blood supply with hypothalamus, so measures a temp closer to your core temp than the peripheral temp at the skin
105
general features of a neg feedback loop
maintaining internal environment around a set point receptors detect change from a set point effectors produce change to return to set point via response
106
why does someone w hypothermia need to be warmed up gently rather than fast
sudden heating causes vasodilation of arteries to extremities, so cold blood flows to the heart and can cause heart failure more blood flow to capillary bed so more heat loss
107
why does core temp drop initially when person w hypothermia is placed in bath of warm water
heat energy lost from periphery warm blood diverted from core to skin
108
why is core re-warming better than other methods of rewarming
w/o core rewarming, other methods lead to vasodilation and cold blood to heart so lower BP temp of medulla oblongata restored faster and this controls HR, BR and shivering via autonomic NS cerebrum temp restored faster, which controls cognitive function cerebellum temp restored faster, which restores co-ordination
109
endotherm behavioural responses to being too cold
orientate body towards sun to increase SA exposed to sun lie in sun move about to generate heat in muscles (in extreme conditions roll into a ball shape to reduce SA and heat loss) remain dry
110
endotherm behavioural responses if too hot
orientate body to reduce SA exposed to sun hide away from sun in shade/burrow remain inactive and spread limbs out to enable greater heat loss wet skin to use evaporation to help cool down (cats lick themselves, elephants spray water over body)
111
endotherm physiological responses if too hot
vasodilation panting (more vaporisation of water from surface of lungs and airways) less skeletal muscle contraction erector muscles relax sweating less response in liver so less heat released
112
endotherm physiological responses if too cold
vasoconstriction less panting shivering erector muscles contrat less sweating more resp in liver cells so more energy form food converted to heat
113
why is it important to maintain the core temperature at a set point (norm) of 37C?
metabolic/chemical reactions are heat sensitive enzymes have an optimum temperature high temperatures lead to enzymes denaturing ESCs fail to form

biology (27 decks)

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