Communication, Homeostasis and Energy -> hormonal and neuronal communication

Question 1

Role of the pituitary gland

Answer 1

The pituitary gland produces the growth hormone, which controls the growth of bones and muscles; anti-diuretic hormone, which increases reabsorption of water in kidneys and gonadrotrophins (which control development of ovaries and testes)

Question 2

Gonadotrophins function

Answer 2

Gonadotrophins control the deevelopment of ovaries and testes

Question 3

Anti-diuretic hormone function

Answer 3

Anti-diuretic hormone increases the reabsorption of water in the kidneys

Question 4

Thryoid gland

Answer 4

The thyroid gland produces thyroxine, which controls the rate of metabolism and rate that glucose is used up in respiration, and promotes growth

Question 5

Adrenal gland

Answer 5

The adrenal glad produces adrenaline which increases heart and breathing rate and raises blood sugar level

Question 6

Testes

Answer 6

Testes produces testosterone, which controls sperm production and secondary sexual characteristics

Question 7

Pineal gland

Answer 7

Pineal gland produces melatonin which affects reproductive development and daily cycles

Question 8

Thymus

Answer 8

The thymus produces thymosin which promotes production and maturation of white blood cells

Question 9

Pancreas

Answer 9

The pancreas produces insulin which converts excess glucose into glycogen in the liver; and glucagon, which converts glycogen back into glucose in the liver

Question 10

Ovaries

Answer 10

The ovaries producce oestrogen, which controls ovulation and secondary sexual characteristics, and progesterone, ostrogen, which controls ovulation and secondary sexual characteristics and progesterone which prepares the uterus lining for recieving an embryo

Question 11

Hormones

Answer 11

-Hormones are chemical messengers that carry information from one part of the body to another
-Secreted directly into the blood when gland is stimulated

Question 12

Movement of hormones

Answer 12

Hormones secreted directly into blood -> transported in blood plasma all over the body -> hormones diffuse ot the blood and bind to specfici receptors found on membranes or in cytoplasms (known as target cells) -> once bound, hormones stimulate target cells to produce response

Question 13

Steroid hormone effect on a target cell (eg oesterogen)

Answer 13

Steroid hormones:
-Lipid-soluble
-Passes through the lipid membrane -> binds to receptors to form hormone-receptor complex -> acts as a transcription factor which facilitates or inhibits the transcription of a specific gene

Question 14

Non-steroid hormone effect on target cells (eg adrenaline)

Answer 14

Non-steroid hormones:
-Hydrophillic so cannot pass directly through cell membrane -> binds to specific receptors -> triggers a cascade reaction mediated by chemicals called second messengers

Question 15

Differences between hormonal and nervous systems

Answer 15

Hormonal system: communication of hormones, tansmitted by blood, slow, target organs, response is widespread, slow but longer lasting, may be permanent and irreversible effect]
Nervous system:
communication by nerve impulses, transmission by neurons and is rapid, specific parts of body, localised response and short-lived, temporary and reversible effect

Question 16

Adrenal gland structure

Answer 16

Adrenal gland structure:
-Two small glands 3cm height and 5cm length
-located ontop of each kidney
-Made up of two parts surrounded by a capsule:
->Adrenal cortex (outer region of glands, produces essential hormones cortisol and aldosterone
-> Adrenal medulla (inner region of the gland, produces non-essential hormones such as adrenaline)

Question 17

Three main types of hormones produced by adrenal cortex

Answer 17

Three main types of hormones produced by adrenal cortex:
-Glucocorticoids
-Mineralocorticoids
-Androgens

Question 18

Glucocorticoids function

Answer 18

Glucocorticoids:
-Include coritsol, helps regulate metabolism by controlling how body converts fats proteins and carbs into energy
-Regulates blood pressure and cardiovascular function
-Other example is corticosterone, that works with cortisol to regulate immune response and suppress inflammatory reactions

Question 19

Mineralocorticoids

Answer 19

Mineralocorticoids:
-Main one is aldosterone, helps control blood pressure by maintaining the balance between salt and water conc in the blood and body fluids - release is mediated by signals triggered by the kidney

Question 20

Androgens

Answer 20

Androgens - type of hormone produced by the adrenal corext - small amounts of male and female sex hormones released, small impact but important still especially after menopause

Question 21

When are the hormones of the adrenal medulla released?

Answer 21

The hormones of the adrenal medulla is released when the sympathetic nervous system is stimulated

Question 22

Hormones secreted by the adrenal medulla

Answer 22

Hormones secreted by the adrenal medulla:
-Adrenaline = increases heart rate, sends blood quickly to muscles and brain, rapidly raises blood glucose conc
-Noradrenaline = works with adrenaline in response to stress, producing effects such as heart rate, pupil widening etc

Question 23

Noradrenaline

Answer 23

-Noradrenaline = works with adrenaline in response to stress, producing effects such as heart rate, pupil widening, blood vessel narrowing of non essential organs to increase blood pressure at essential organs

Question 24

Main functions of the pancreas

Answer 24

Main functions of the pancreas:
-Exocrine gland = produces enzymes and release them via duct into the duodenum
-Endocrine gland = produces hormones and release them into the blood

Question 25

Three important enzymes produced by the pancreas

Answer 25

Three important enzymes produced by the pancreas:
-Amylases (breaks starch into simple sugars)
-Proteases (breaks proteins into amino acids)
-Lipases (breaks down lipids into fatty acids and glycerol)

Question 26

Islets of langerhans

Answer 26

Islets of langerhans:
-Lightly stained appearence under a microscope
-Large spherical cluster shape
-Endocrine tissue within pancrease
-Produces and secrets hormones

Question 27

Pancreatic acini/acinus

Answer 27

Pancreatic acini/acinus:
-Darker stained appearence under a microscope
-Small, berry-like clusters
-Exocrine pancreatic tissue
-Produces and secretes digestive enzymes

Question 28

Types of cells within the islets of langerhans

Answer 28

Types of cells within the islets of langerhans:
-alpha cells = produces and secretes glucagon (larger and more numerous) (pink stain)
-beta cells = produces and secretes insulin (blue cells)

Question 29

Factors that increase blood glucose concentration

Answer 29

Factors that increase blood glucose concentration;
-Diet (carbohydrate-rich foods)
-Glycogenolysis
-Gluconeogenesis

Question 30

Glycogenolysis

Answer 30

Glycogenolysis = glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream increasing blood glucose concentration

Question 31

Gluconeogenesis

Answer 31

Gluconeogenesis: the production of glucose from non-carbohydrate sources (eg liver is able to make glucose from glycerol from lipids and amino acids)

Question 32

Ways of which blood glucose concentration decreases

Answer 32

Ways of which blood glucose concentration decreases:
-Respiration
-Glycogenesis

Question 33

Glycogenesis

Answer 33

Glycogenesis = the production of glycogen - when blood glucose conc is too high, excess glucose taken in through the diet is converted into glycogen which is stored in the liver

Question 34

How does insulin interact with receptors to lower blood glucose concentration?

Answer 34

Insulin binds to complementary glycoprotein receptor -> change in tertiary structure of glucose transport protein channels -> causes channels to open allowing more glucose to enter the cell
-Insulin also activates enzymes within some cells to convert glucose to glycogen and fat

Question 35

How does insulin lower blood glucose concentration:

Answer 35

Insulin:
-Increases rate of absorption of glucose by cells
-Increases repiratory rate of cells (increases need for glucose and causes higher uptake of glucose from the blood
-Increases rate of glycogenesis by stimulating liver to remove glucose and convert it to glycogen
-Increases rate of glucose to fat conversion
-Inhibits release of glucagon from alpha cells of the islets of langerhans

Question 36

How does glucagon raise blood glucose concentration?

Answer 36

Glucagon:
-Glycogenolysis - liver breaks down its glycogen store into glucose and releases it back into the bloodstream
-Reducing the amount of glucose absorbed by the liver cells
-Increases gluconeogensis - increases conversion of amino acids and glycerol into glucose in the liver

Question 37

Antagonistic hormones

Answer 37

Insulin and glucagon are antogonisitc hormones in that they work against eachother

Question 38

Why does blood glucose concentration fluctuate?

Answer 38

Blood glucose concentration fluctuates as a result of negative feedback

Question 39

Mechanism of control of insulin secretion by the B cells in the islets of langerhans

Answer 39

Mechanism of control of insulin secretion by the B cells in the islets of langerhans:
1). Normal blood glucose conc levels, potassium channels in the plasma membrane of B cells are open and potassium ions diffuse out cell
2), when conc rises, glucose enters the cell by a glucose transporter
3). Glucose is metabolised inside the mitochondria, resulting in ATP production
4). ATP binds to potassium channels and causes them to close (known as ATP-sensitive potassium channels)
5). potassium ions cant diffuse out, potential difference reduces
6). Depolarisation causes calcium channels to open
7). Calcium ions enter cell and causes secretory vesicles to release insulin by exocytosis

Question 40

Hyperglycaemia

Answer 40

Hyperglycaemia = raised blood sugar

Question 41

Type 1 diabetes

Answer 41

Type 1 diabetes:
-Unable to produce insulin (Beta cells in islet of langerhans do not produce it
-Could occur as a result of an autoimmune response where cells attack B cells
-Beings in childhood
-Controlled by insulin injections

Question 42

Type 2 diabetes

Answer 42

Type 2 diabetes:
-Does not respond to insulin
-Could be due to not producing enough insulin or cells not responsing to insulin
-Often due to glycoprotein insulin receptor not working properly
-Mostly as a result of obesity, inactivity and carb diet
-Controlled by diet regulation

Question 43

Advantages of obtaining insulin from genetically modified bacteria

Answer 43

Advantages of obtaining insulin from genetically modified bacteria:
-Produced in pure form, less likely to cause allergic reactions
-Can be produced in high quantities
-Cheaper production costs
-Concern of using animal products are overcome

Question 44

Use of stem cells in diabetes treatment

Answer 44

Use of stem cells in diabetes treatment:
Stem cells differentiated into pancreatic B inslet cells and injected into diabetes patient (risk of autoimmune response, immunosupressant drugs and make them prone to infection)

Question 45

Advantages of using stem cells

Answer 45

Stem cells advantages:
-Donor availability not an issue
-Reduced likelihood of rejection problems as embryoic stem cells generally not rejected
-People wouldn’t have to inject themselves with insulin

Question 46

Coordination of the flight or fight response

Answer 46

Coordination of the flight or fight response:
-Threat detected by autonomic nervous system -> hypothalamus communicates with sympathetic nervous sytem (sns) and adrenal-cortical system (acs) -> sns uses neuronal pathways to initiate body reactions wheras acs uses hormones -> this combined effect results in fight or flight response

Question 47

Purpose of fight or flight physiological responses

Answer 47

Purpose of fight or flight physiological responses:
-Heart rate increase -> more oxygenated blood around body
-Pupil dilation -> more light in for better sight
-Vasoconstriction of blood vessels -> restricts blood flow to non-essential organs
-Increased blood glucose conc -> more respiration for muscle contraction

Question 48

Action of adrenaline

Answer 48

Action of adrenaline:
1). The hormone adrenaline approaches receptor site
2). Adrenaline fuses to receptor site, and in doing so activates an enzyme inside the membrane
3). The activated enzyme converts ATP to cyclic AMP, which activates other enzymes that in turn convert glycogen to glucose

Question 49

Cyclic AMP

Answer 49

Cyclic AMP
Activated enzyme that acts as a second messenger for adrenaline, by activating other enzymes which in turn converts glycogen to glucose in liver cells

Question 50

Adenylyl cyclase

Answer 50

Adenylyl cyclase triggers the conversion of ATP into cyclic adenosine mono-phosphate (cAMP) on the inner surface of the cell membrane in the cytoplasm

Question 51

Effect of an increase in cAMP levels (due to the action of adnylyl cyclase)

Answer 51

Effect of an increase in cAMP levels (due to the action of adnylyl cyclase);
activates specific enzymes called protein kinases which phosphorylate/activate other enzymes

Question 52

Where in the brain is responsible for controlling heart rate?

Answer 52

The medulla oblongata in the brain is responsible for controlling heart rate and making necessary changes
-made up of two centres

Question 53

Two centres that the medulla oblongata is made up of

Answer 53

Two centres that the medulla oblongata is made up of:
-One increases HR by sending impulses through the symathetic nervous system, transmitted by the accelerator nerve
-Other centre decreases heart rate by sending impulses through the parasympathetic nervous system by the vagus nerve

Question 54

Baroreceptors

Answer 54

Baroreceptors (pressure receptors) - detect changes in blood pressure,

Question 55

Chemoreceptors

Answer 55

Chemoreceptors:
-Chemoreceptors are chemical receptors that detect changes in the level of particular chemicals in the blood such as carbon dioxide

Question 56

Where are baroreceptors located?

Answer 56

Baroreceptors are located in the aorta, vena cava and carotid arteries

Question 57

Chemoreceptors location

Answer 57

Chemoreceptors are located in the aorta, the carotid artery and the medulla

Question 58

The carotid artery

Answer 58

The carotid artery is a major artery in the neck that supplies the brain with blood

Question 59

How do chemoreceptors work?

Answer 59

Chemoreceptors - sensitive to changes in the pH level of th blood - if carbon dioxide incredases, pH decreases as carbonic acid is formed, then chemoreceptors detect this change and a response is triggered to increase heart rate

Question 60

How baroreceptors work

Answer 60

Baroreceptors - detects changes in pressure - when too high, impulses sent to medulla oblongata centre which decreases HR as impulses sent from medulla to SAN (opposite for low pressure)

Question 61

Why do organs need to communicate with eachother?

Answer 61

Organs need to communicate with eachother in order to perform their specific functions and operate effectively. This is especially the case as only few body systems can work in isolation.
-Example = muscle cells relying on rbc for oxygen replenishment for respiration

Question 62

What is cell signalling?

Answer 62

Cell signalling occurs when one cell releases a chemical which has an effect on another cell, known as the target cell. Coorindation relies on communication through the signalling process.

Question 63

How does cell signalling work?

Answer 63

Cell signalling works by:
-Transferring signals locally (eg between neurones at synapses where the signal is the neurotransmitter)
-Transfer signals across large distances through the use of hormones (eg ADH released by the pituitary gland)

Question 64

Internal factors that we need to respond to within our body

Answer 64

Internal factors that we need to respond to include blood glucose concentration, internal temperature, water potential, cell pH

Question 65

External factors that we need to respond to in our body

Answer 65

External factors that we need to respond to include humidity, external temperature, light intensity, and new or sudden sound

Question 66

What is homeostasis?

Answer 66

Homeostasis is the process of maintaining a constant internal environment through the coordination of organisms

Question 67

Example of homeostasis within our body

Answer 67

An example of homeostasis is the digestive organs such as the exocrine pancreas, duodenum, ileum and along with the endocrine pancreas and liver, which work together in order to maintain a constant blood glucose concentration

Question 68

Key features of the structure of a neurone

Answer 68

Key features of the structure of a neurone:
-cell body
-axons
-dendrites

Question 69

Cell body of a neurone

Answer 69

Cell body of a neurone:
-Contains th enucleus surrounded by cytoplasm
-Within the cytoplasm, there are large amounts of endoplasmic reticulum and mitochondria that are involved in the production of neurotransmitters

Question 70

Dendrons/Dendrites of neurones

Answer 70

Dendrons are short extensions which came from the cell body and divides into smaller branches known as dendrites, which are responsible for transmitting electrical impulses towards the cell body

Question 71

Sensory neurones

Answer 71

Sensory neurones transmit impulses from a sensory receptor cell to a relay neurone
-Consists of one dendron which carries the impulse to the cell body, and one axon which carries the impulse away from the cell body

Question 72

Relay neurones

Answer 72

Relay neurones transmit impulses between neurones
-Many short axons and dendrons

Question 73

Motor neurones

Answer 73

Motor neurones transmit impulses from a relay of sensory neurone to an effector, such as a muscle or gland, and have one long axons and many short dendrites

Question 74

Pathway of an electrical impulse

Answer 74

Pathway of an electrical impulse:
Receptor -> sensory neurone -> relay neurone -> motor neurone ->effector cell

Question 75

What is the myelin sheath of neurones?

Answer 75

The myelin sheath covers the axons of neurones and is made up of layers of plasma membrane - schwaan cells produce these layers by growing around the axon
-Each time they grow, a double layer of phospholipid bilayer is laid down
-The myelin sheath acts an insulating layer, allowing these myelinated neurones to conduct the electrical impulse faster

Question 76

What the nodes of ranvier?

Answer 76

The nodes of ranvier are found between the gaps of adjacent schwaan cells

Question 77

Myelinated motor neurones

Answer 77

In myelinated neurones, the electrical impulse jumps from one node to the next as it travels along the neurone, allowing it to be transmitted faster, in comparison to the non-myelinated neurones where the impulse does not jump and travels slower along the nerve fibre

Question 78

Central nervous system

Answer 78

The central nervous system consists of your brain and spinal cord

Question 79

Preipheral nervous system

Answer 79

The peripheral nervous system consists of all the neurones that connect to the CNS to the rest of the body

Question 80

The somatic nervous system

Answer 80

The somatic nervous system is under conscious control, as it is used when voluntarily deciding to do something.
-When there is sympathetic stimulation, saliva production is reduced, bronchial muscle relaxes, decreaesd urine secretion from kidneys, stomach and small intestine peristalsis reduced

Question 81

The autonomic nervous system

Answer 81

The autonomic nervous system works constantly, and is under subconscious control and is used when the body does something atuomatically
-Carries nerve impulses to glands, smooth and cardiac muscle
-Divised into sympathetic and parasympathetic

Question 82

Sympathetic nervous system

Answer 82

Sympathetic nervous system -> responsible for increased activity eg increased heart rate
-Fight or flight responses - neurotransmitter is noradrenalin

Question 83

Parasympathic nervous system

Answer 83

Parasympathetic nervous system -> responsible for decreased activity eg heart rate after exercise
-Relaxing responses, neurotransmitter is acetylcholine

Question 84

Features of sensory receptors

Answer 84

Features of sensory receptors:
-Specific to a stimulus
-Converts stimulus into nervous impulse

Question 85

Types of sensory receptors

Answer 85

Types of sensory receptors:
-Mechanoreceptors = pressure/movement (stimulus = pacinian capsule)
-Chemoreceptor = chemical stimulus
-Thermoreceptor = heat stimulus
-Photoreceptor = light stimulus

Question 86

What is a transducer?

Answer 86

Transducer = sensory receptor that converts stimulus into nervous impulse

Question 87

Pacinian capsule

Answer 87

Pacinian capsule -> contains stretch-mediated sodium channels within the neurone -> when changing shape, the channel permeability changes

Question 88

How the pacinian capsule converts mechanical pressure into impulse

Answer 88

How the pacinian capsule converts mechanical pressure into impulse:
1). Resting state = stretch-mediated channels too narrow for sodium ions to pass through (resting potential)
2). Pressure applied -> corpsicle changes shape and membrane stretches
3). When stretched, channels widen and sodium ions diffuse in
4). Becomes depolarised (generator potential)
5). Generator potential creates action potential

Question 89

What is resting potential?

Answer 89

Resting potential is when the neurone is not transmitting an impulse
-> outside of the membrane is more positively charged than inside the axon - membrane is polarised (negative)

Question 90

Why does resting potential occur?

Answer 90

Resting potential occurs as a result of the movement of sodium and potassium ions across a membrane (which has to be moved via channel proteins)

Question 91

Process resulting in creation of a resting potential

Answer 91

Process resulting in creation of a resting potential:
-Sodium ions actively transported out axon where potassium ions actively transported into axon by intrinsic protein sodium-potassium pump (movement not equal - eg 3 sodium in, 2 out)
-More sodium ions outside, more potassium ions inside, so sodium diffuse in and potassium diffuse out
-Most gated sodium channels close so less enters than potassium ions out -> more positive outside axon -> creates the resting potential of -70mV

Question 92

What is action potential?

Answer 92

Action potential occurs when protein channels in axon membrane changes shape -> results in opening/closing of voltage-gated ion channels

Question 93

Process of action potential

Answer 93

Action potential:
1). Neurone has resting potential - some potassium channels open, all sodium channels closed
2). Stimulus triggers channels to open - permeable to sodium ions - diffuses in so inside less negative
3). Change in charge - more sodium channels open + diffuse in (positive feedback)
4). Potential difference = +40mV -> sodium channels close - potassium channels open
5). Potassium ions diffuse out, change reduced, more negative inside (hyperpolarisation)
6). Channels close - sodium-potassium pump causes sodium ions out, potassium ion in (repolarisation)

Question 94

What is a nerve impulse?

Answer 94

A nerve impulse is an action potential that starts at one end of the neurone and is propagated along the axon to the other end of the neurone

Question 95

What occurs after action potential has passed?

Answer 95

After an action potential there is a short period of time when the axon cannot be excited again (known as the refractory period)->during this, voltage-gated sodium channels remain closed

Question 96

Why is a refractory period impotrant?

Answer 96

Refractory period is important because it prevents the propagation of an action potential backwards along the axon as well as forwards
->Makes sure action potentials are unidirectional + ensures action potentials don’t overlap

Question 97

What is saltatory conduction?

Answer 97

Saltatory conduction is a process where the action potential then jumps from one node to another where no myelin is present
->fast process

Question 98

Factors that affect the speed at which an action potential travels

Answer 98

Factors that affect the speed at which an action potential travels:
-Axon diameter (bigger = faster because there is less resistance to ion flow)
-Temperature (higher = faster as ions diffuse faster - only occurs up to 40 as more causes denaturation)

Question 99

‘All or nothing principle’ in terms of nervous impulses

Answer 99

nerve impulses - certain level of stimulus (threshold value) needed to trigger response - reaching this always creates action potential

Question 100

Synapse structure

Answer 100

Synapse structure:
-Synaptic cleft (gap which seperates axon of one neurone from dendrite of next neurone)
-Presynpatic neurone (neurone along which the impulase has arrived)