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Question 1

Define homeostasis and how it is regulated.

Answer 1

a property of cells, tissues and organisms that allows the maintenance and regulation of nearly constant conditions in the internal environment (the adjustment of biochemical pathways and physiological processes)

central regulation = nervous (ANS activate/suppress physiological processes in tissues), endocrine (glandular tissues that release factors that activate/suppress physiological processes in tissues which express their receptors)
local regulation = autonomic reflexes (cardiovascular and gastrointestinal) and chemical

Question 2

Define adaptations

Answer 2

Heritable changes to a species that results in permanent physiological changes to increase fitness

Question 3

Define Acclimation and give an example

Answer 3

The process in which an individual organism adjusts to a change in its environment (such as a change in altitude, temperature, humidity, photoperiod or pH), allowing it to maintain fitness across a range of environmental conditions

example: starvation periods encountered by early humans, metabolic chemistry significantly altered to maintain needed levels of water-soluble fuels that can cross the BBB
After a day switch’s to ketones as primary energy source instead of glucose
Ketones can cross blood brain barrier

Question 4

What is an adrenergic neuron

Answer 4

A neuron that uses norepinephrine as a neurotransmitter

Question 5

What is meant by afferent

Answer 5

travels towards CNS

Question 6

Antagonism and give an example

Answer 6

two-regulation in homeostasis - a pair of hormones that have opposing effects on one another

example: blood calcium homeostasis

thyroid gland releases calcitonin when high blood Ca2+ levels - calcitonin stimulates calcium salt deposit in bone

parathyroid gland release parathyroid hormone when low blood Ca2+ levels - osteoclasts degrade bone matrix and release Ca2+ into blood

Question 7

Autonomic tone and give an example

Answer 7

occurs when the sympathetic nervous system regulates both the increase and decrease in the activity of a stimulated organ

example: blood flow
under resting conditions, the SNS maintains arterial diameter at 50%
increase SNS constricts muscles, increasing resistance in the arteries
decreasing SNS relaxes muscles, decreasing resistance in the arteries

Dual innervation to issues – systems work together to fine tune functions
Dominance of sympathetic or parasympathetic paraments to maintain their set-points
Basal tone = sympathetic nervous system regulates diameter all the time

Question 8

Autonomic nervous system

Answer 8

controlling smooth muscles, glands and other internal bodily systems (unaware/involuntary)

evaluates the environment

the control center is the hypothalamus

operates through visceral reflexes = subconscious sensory signals from organs to control center and then reflex to control organs activity

Question 9

What is a cholinergic neuron

Answer 9

neurons that utilise acetylcholine as neurotransmitter

Question 10

What is DAG?

Answer 10

A second messenger signaling lipid
It activates the enzyme protein kinase C which then phosphorylates a large number of proteins leading to the cell’s response

Question 11

Define disease

Answer 11

disrupted homeostasis

Question 12

Define dimersiation

Answer 12

A general mechanism to increase binding site affinity, specificity and diversity

Question 13

Define endocrine

Answer 13

The glands and organs that make hormones and release them directly into the blood so they can travel to tissues and organs all over the body

Question 14

What is meant by efferent

Answer 14

travels away from CNS

Question 15

What does endogenous GTPase do?

Answer 15

degrades GTP back to GDP, inactivating the protein
GTPase activity causes the alpha subunit to dissociate from phospholipase C

Question 16

What is a G-protein, what types are there and there overall function

Answer 16

a family of proteins that act as molecular switches inside cells, specialized proteins with the ability to bind the nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP)

Gs = stimulatory = Adenlyate cyclase activation
Gi = inhibitory = adenylate cyclase inhibition
Gq = Ca2+ pump

Question 17

What is GTP

Answer 17

guanosine triphosphate, analogous to ATP = specific role in signalling pathways and a major cellular metabolites

Question 18

Define Hormones

Answer 18

chemical substances that act like messenger molecules in the body

Question 19

Define Ion channels

Answer 19

protein molecules that span across the cell membrane allowing the passage of ions from one side of the membrane to the other

Question 20

What is the function of IP3

Answer 20

mobilizes calcium ions from mitochondria and the endoplasmic reticulum, and the calcium ions then have their own second messenger effects, such as smooth muscle contraction and changes in cell secretion

Question 21

Define Mass discharge and the role of the adrenal gland in mass discharge

Answer 21

almost all portions of the sympathetic nervous system discharge simultaneously as a complete unit

adrenal gland makes hormone adrenaline - sends it to your bloodstream - temporary fast changes in body
When hypothalamus is activated by fright or severe pain almost all portions of the sympathetic nervous system discharge simultaneously - increases the ability of the body to perform vigorous muscle activity

Hypothalamus activates sympathetic division
Heart rate, blood pressure and respiration increase
Adrenal medulla secretes epinephrine and norepinephrine
Blood flow to skeletal muscles increases
Stomach contractions are inhibited

Question 22

What does monophosphatase do in signal transduction?

Answer 22

hydrolyses IP3 in the cytoplasm and within the ER
causes second messenger to be short lived and degraded quickly
attenuates the signal

Question 23

Define Negative feedback loop and give an example

Answer 23

counteract imbalances in the set point of a parameter to restore the normal state

example: temperature
Stimulus = decreased temperature
Sensor = hypothalamus (thermoreceptor cells in hypothalamus that detect changes in body temp)
Control = activity of ANS and SMS
Effector = vessel diameter constricts and muscle contractions (shivering generates heat)
Increased temp = hypothalamus stimulates ANS to increase blood flow to skin and increase diaphoresis (sweating)

example: blood glucose levels
Stimulus = change in blood glucose
Sensor = beta cells (when rising levels) or alpha cell (falling levels)
Control = secretion of insulin or glycogen
Effector = muscle cells/fat cells (muscles take the glucose out of your blood and store it as glycogen, fat cells take glucose out of the blood and use it to build triglycerides) or act on liver to restore glucose (stimulates glycogen breakdown into glucose)

Question 24

Define what a nerve is

Answer 24

A bundle of fibers that receives and sends messages between the body and the brain

Question 25

What is a neurotransmitter?

Answer 25

a chemical substance which is released at the end of a nerve fibre by the arrival of a nerve impulse and, by diffusing across the synapse or junction, effects the transfer of the impulse to another nerve fibre, a muscle fibre, or some other structure (chemical messenger your body can’t function without)

Question 26

What is phosphodiesterase?

Answer 26

catalyses the hydrolysis of cAMP (attenuation of signal transduction)

Question 27

Define positive feedback loop and give an example

Answer 27

physiological responses that re-enforce and amplify an initiating stimulus example: birth contractions When uterine contractions become strong enough for the baby’s head to begin pushing through the cervix, stretching of the cervix sends signals through the uterine muscle back to the body of the uterus, causing even more powerful contractions. Thus the uterine contractions stretch the cervix and the cervical stretch causes stronger contractions. When this process becomes powerful enough, the baby is born.

Question 28

What is a preganglionic fibre? And state what neurotransmitter is released for SNS and PNS

Answer 28

fibres from CNS to ganglion PNS and SNS = cholingeric = release acetylcholine

Question 29

What is a postganglionic fibre? And state what neurotransmitter is released for SNS and PNS

Answer 29

fibers from the ganglion to the effector organ PNS = cholinergic = release acetylcholine SNS = adrenergic = norepinephrine = except sweat glands and vasodilator to skeletal muscle which is cholinergic

Question 30

What is phospholipase C?

Answer 30

an enzyme that catalyses the breakdown of PIP2 into two second messengers, DAG and IP3

Question 31

What are protein kinases?

Answer 31

type of enzyme (a protein that speeds up chemical reactions in the body) that adds chemicals called phosphates to other molecules, such as sugars or proteins inducing conformational change from an inactive to an active form of the protein They are activated by phosphorylation which in turn activates a cascade of events leading to the phosphorylation of different amino acids

Question 32

Define receptor

Answer 32

receptors are a special class of proteins that function by binding a specific ligand molecule

Question 33

Define set-point in homeostasis

Answer 33

the set point in homeostasis is the balanced physiological value for a variable when the body begins to stabilise

Question 34

Define signal transduction

Answer 34

Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellular response

Question 35

Define stimulus, sensor, control center and effector

Answer 35

Stimulus: a deviation from a physiological set point Sensor: a sensor detects the change in homeostasis Control center: a control center is the part of the body that responds to the change Effector: an effector is any organ or cell that ultimately responds to the stimulus

Question 36

Define signal amplification

Answer 36

an increase in the intensity of a signal through networks of intracellular reactions (amplified through activation of intracellular signal proteins with enzymatic activity)

Question 37

Define signal termination

Answer 37

a sequence that signals the end (termination of activation) Many negative regulators help attenuate and terminate a signal once the bodies internal environment has been moved back to its set-point Endogenous GTPase Ca2+ pump phosphodiesterase

Question 38

What is the synapse

Answer 38

The space between the end of a nerve cell and another cell

Question 39

What is a target cell

Answer 39

any cell that has a specific receptor for an antigen or antibody or hormone or drug

Question 40

Vagus nerve

Answer 40

regulation of internal organ functions, such as digestion, heart rate, and respiratory rate (mixed nerve)

Question 41

Tyrosine kinase receptors

Answer 41

act as signal transducers that mediate cell-to-cell communication

Question 42

How is homeostasis regulated in ANS and endocrine system

Answer 42

Sympathetic and parasympathetic division of ANS of the body induce opposing physiological changes to keep the internal environment in balance secrete hormones into bloodstream to maintain homeostasis and regulate metabolism (hypothalamus and pituitary gland are the control centers directing hormones) - hypothalamus stimulates the pituitary gland to secrete activating hormone Glandular tissues that released factors activate/suppress physiological process in tissues that express their receptors

Question 43

Compare and contrast branches of somatic and autonomic nervous system

Answer 43

SOMATIC Single neuron from CNS to effector organs Heavily myelinated axon Only stimulatory Releases acetylcholine at effector AUTONOMIC Two-neuron chain from CNS to effector organ (preganglionic and postganglionic neurons Lightly myelinated preganglionic axon and unmyelinated postganglionic axon Stimulatory and inhibitory depending on neurotransmitter All preganglionic fibres release acetylcholine into ganglion Sympathetic postganglionic fibres release norepinephrine (stimulatory) and postganglionic parasympathetic release acetylcholine (inhibitory)

Question 44

Discuss contributions of sympathetic nervous system and parasympathetic

Answer 44

Sympathetic = fight or flight = increases alertness, energy, blood pressure, heart rate and breathing rate Parasympathetic = rest and digest = the vagus nerve is heavily involved in, decreases alertness, blood pressure and heart rate, and helps with calmness relaxation and digestions

Question 45

What are anatomical differences between SNS and PNS neurons

Answer 45

Spinal cord exit site (SNS = exit in thoracolumbar region, PNS = exit in craniosacral and bum) Neurotransmitters in postganglionic fiber's Sympathetic release norepinephrine (adrenergic) at effector organ except sweat gland and vasodilator to skeletal muscle vasculator Parasympathetic release acetylcholine (cholinergic) at effector organ Receptors expressed at target tissues Sympathetic expresses adrenergic receptor Parasympathetic express muscarinic receptor (Gi and Gq) or nicotinic receptors (gated ion channels) Activity of target tissue Sympathetic = stimulatory Parasympathetic = inhibitory Sympathetic preganglionic neurons shorter as they synapse in ganglion of sympathetic chain as parasympathetic preganglionic neurons synapse at the effector organ

Question 46

What receptors are on the target tissue of SNS

Answer 46

Adrenergic receptors that signal via G protein complexes alpha = mostly activate Gq, Gi beta = mostly activate Gs

Question 47

What receptors are on the target tissue of PNS

Answer 47

Muscarinic receptors mostly signal Gi or Gq (stimulate smooth muscle and slows HR) Nicotinic receptors activate gated ion channels (affect skeletal muscle) - found between pre and post ganglionic neurons of PNS and SNS

Question 48

Describe three types of signal transducing membrane receptors

Answer 48

Ion channel linked Neurotransmitter binds to receptor Conformational change usually opening or closing a channel Ions flow in/out Movement of ions causes subsequent effects on postsynaptic cells G-protein linked Secondary messenger system G protein binds to active receptor GTP replaces GDP Subunit migrates down membrane resulting in catalytic activity Change in effector activity Enzyme linked Monomers Activation of ligands brings them together Dimerization Cell phosphorylate Other proteins associated with them They become activated Cellular response

Question 49

Identify major components within G protein signal transduction involving Gs and Gi

Answer 49

Gs and Gi have antagonistic influences on adenylyl cyclase resulting in formation of cAMP or inhibition of formation of cAMP The inactive G-protein complex is free in the cytosol (as long as g-protein is bound to GDP it remains inactive) Receptor activated by neurotransmitter following a nerve impulse Receptor undergoes conformational change exposing binding site for G-protein As G-proteins binds to receptor it releases GDP and is g-protein is simultaneously bound to GTP G complex is then free to move within the cytoplasm of the cell and down the membrane (specific function depends on each type of neuron) Subunit binds to adenylyl cyclase – catalyses conversion of ATP into cAMP inside cell Activates enzyme activity ATP converted to cAMP cAMP while present activates protein kinase which then phosphorylates (phosphate group is added to a molecule) other proteins which are often other enzymes leading to metabolic processes This then activates cAMP-dependent protein kinase, which phosphorylates specific cell proteins, triggering biochemical reactions that ultimately lead to the cell’s response to the hormone cAMP levels are regulated by phosphodiesterase to terminate the signal If binding of the hormone to its receptors is coupled to an inhibitory G protein (denoted Gi protein), adenylyl cyclase will be inhibited, reducing formation of cAMP and ultimately leading to an inhibitory action in the cell Transducer = Gs Effector = adenylyl cyclase Second messenger = cAMP – then activates protein kinase which phosphorylates proteins = cell response Negative regulators (terminator) = endogenous GTPase causes alpha subunit dissociation and phosphodiesterase cleave cAMP, attenuating the signal

Question 50

Identify major components within G protein signal transduction involving Gq

Answer 50

Same process as above Subunit binds to phospholipase C This enzyme catalyses the breakdown of some phospholipids, PIP2 which causes the formation of two second messengers IP3 and DAG (cleave phosphate group, catalyses hydrolysis of PIP2) The IP3 mobilizes calcium ions from mitochondria and the endoplasmic reticulum, and the calcium ions then have their own second messenger effects, such as smooth muscle contraction and changes in cell secretion IP3 acts mainly to stimulate calcium release from the endoplasmic reticulum (active transport of Ca2+ ions from cytoplasm into ER) Release of Ca into the cytoplasm activates cellular responses (muscle contractions) DAG, the other lipid second messenger, activates the enzyme protein kinase C, which then phosphorylates a large number of proteins, leading to the cell’s response IP3 is rapidly hydrolysed by inositol monophosphates in the cytoplasm and within the ER Ca2+ sucked back into ER by a pump - pumps Ca2+ from cytoplasm into ER Transducer = Gq Effector = phospholipase C Second messenger = IP3 and DAG Negative regulator = phosphatase and Ca2+ pump

Question 51

Differences between nerves of sympathetic and parasympathetic

Answer 51

SNS two neurons = preganglionic and postganglionic neuron ganglion (where the 2 neurons meet) lies in sympathetic chain PNS two neurons = preganglionic and postganglionic neuron ganglion is located at wall or organ = preganglionic neuron pass uninterrupted all the way to the organ

Question 52

Explain tyrosine kinase as a form of signal transduction

Answer 52

When ligand binds to membrane receptor and external part of the monomer, this induces dimerization of the monomer Binding ligand = changes conformation of monomer = tyrosine receptors come together on the surface which activates a catalytic domain resulting in autophosphorylation of these tyrosine groups (phosphates being added onto the molecule) These phosphotyrosine groups serve as docking points for cellular adaptor proteins that associate with phosphotyrosine - leads to conformational change and activation of protein = cellular responses Monomers Activation of ligands brings them together Dimerization Cell phosphorylate Other proteins associated with them They become activated Cellular response

Question 53

Define Neuroendocrine

Answer 53

sympathetic nervous system acts upon the adrenal gland causing cells with in the adrenal gland to release adrenaline Neuroendocrine hormones are secreted by neurons into the circulating blood and influence the function of target cells at another location in the body