Communication, Homeostasis and Energy -> hormonal and neuronal communication Flashcards
Role of the pituitary gland
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)
Gonadotrophins function
Gonadotrophins control the deevelopment of ovaries and testes
Anti-diuretic hormone function
Anti-diuretic hormone increases the reabsorption of water in the kidneys
Thryoid gland
The thyroid gland produces thyroxine, which controls the rate of metabolism and rate that glucose is used up in respiration, and promotes growth
Adrenal gland
The adrenal glad produces adrenaline which increases heart and breathing rate and raises blood sugar level
Testes
Testes produces testosterone, which controls sperm production and secondary sexual characteristics
Pineal gland
Pineal gland produces melatonin which affects reproductive development and daily cycles
Thymus
The thymus produces thymosin which promotes production and maturation of white blood cells
Pancreas
The pancreas produces insulin which converts excess glucose into glycogen in the liver; and glucagon, which converts glycogen back into glucose in the liver
Ovaries
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
Hormones
-Hormones are chemical messengers that carry information from one part of the body to another
-Secreted directly into the blood when gland is stimulated
Movement of hormones
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
Steroid hormone effect on a target cell (eg oesterogen)
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
Non-steroid hormone effect on target cells (eg adrenaline)
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
Differences between hormonal and nervous systems
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
Adrenal gland structure
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)
Three main types of hormones produced by adrenal cortex
Three main types of hormones produced by adrenal cortex:
-Glucocorticoids
-Mineralocorticoids
-Androgens
Glucocorticoids function
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
Mineralocorticoids
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
Androgens
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
When are the hormones of the adrenal medulla released?
The hormones of the adrenal medulla is released when the sympathetic nervous system is stimulated
Hormones secreted by the adrenal medulla
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
Noradrenaline
-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
Main functions of the pancreas
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
Three important enzymes produced by the pancreas
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)
Islets of langerhans
Islets of langerhans:
-Lightly stained appearence under a microscope
-Large spherical cluster shape
-Endocrine tissue within pancrease
-Produces and secrets hormones
Pancreatic acini/acinus
Pancreatic acini/acinus:
-Darker stained appearence under a microscope
-Small, berry-like clusters
-Exocrine pancreatic tissue
-Produces and secretes digestive enzymes
Types of cells within the islets of langerhans
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)
Factors that increase blood glucose concentration
Factors that increase blood glucose concentration;
-Diet (carbohydrate-rich foods)
-Glycogenolysis
-Gluconeogenesis
Glycogenolysis
Glycogenolysis = glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream increasing blood glucose concentration
Gluconeogenesis
Gluconeogenesis: the production of glucose from non-carbohydrate sources (eg liver is able to make glucose from glycerol from lipids and amino acids)
Ways of which blood glucose concentration decreases
Ways of which blood glucose concentration decreases:
-Respiration
-Glycogenesis
Glycogenesis
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
How does insulin interact with receptors to lower blood glucose concentration?
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
How does insulin lower blood glucose concentration:
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
How does glucagon raise blood glucose concentration?
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
Antagonistic hormones
Insulin and glucagon are antogonisitc hormones in that they work against eachother
Why does blood glucose concentration fluctuate?
Blood glucose concentration fluctuates as a result of negative feedback
Mechanism of control of insulin secretion by the B cells in the islets of langerhans
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
Hyperglycaemia
Hyperglycaemia = raised blood sugar
Type 1 diabetes
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
Type 2 diabetes
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
Advantages of obtaining insulin from genetically modified bacteria
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
Use of stem cells in diabetes treatment
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)
Advantages of using stem cells
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
Coordination of the flight or fight response
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
Purpose of fight or flight physiological responses
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
Action of adrenaline
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
Cyclic AMP
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
Adenylyl cyclase
Adenylyl cyclase triggers the conversion of ATP into cyclic adenosine mono-phosphate (cAMP) on the inner surface of the cell membrane in the cytoplasm
Effect of an increase in cAMP levels (due to the action of adnylyl cyclase)
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
Where in the brain is responsible for controlling heart rate?
The medulla oblongata in the brain is responsible for controlling heart rate and making necessary changes
-made up of two centres
Two centres that the medulla oblongata is made up of
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
Baroreceptors
Baroreceptors (pressure receptors) - detect changes in blood pressure,
Chemoreceptors
Chemoreceptors:
-Chemoreceptors are chemical receptors that detect changes in the level of particular chemicals in the blood such as carbon dioxide
Where are baroreceptors located?
Baroreceptors are located in the aorta, vena cava and carotid arteries
Chemoreceptors location
Chemoreceptors are located in the aorta, the carotid artery and the medulla
The carotid artery
The carotid artery is a major artery in the neck that supplies the brain with blood
How do chemoreceptors work?
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
How baroreceptors work
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)
Why do organs need to communicate with eachother?
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
What is cell signalling?
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.
How does cell signalling work?
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)
Internal factors that we need to respond to within our body
Internal factors that we need to respond to include blood glucose concentration, internal temperature, water potential, cell pH
External factors that we need to respond to in our body
External factors that we need to respond to include humidity, external temperature, light intensity, and new or sudden sound
What is homeostasis?
Homeostasis is the process of maintaining a constant internal environment through the coordination of organisms
Example of homeostasis within our body
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
Key features of the structure of a neurone
Key features of the structure of a neurone:
-cell body
-axons
-dendrites
Cell body of a neurone
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
Dendrons/Dendrites of neurones
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
Sensory neurones
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
Relay neurones
Relay neurones transmit impulses between neurones
-Many short axons and dendrons
Motor neurones
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
Pathway of an electrical impulse
Pathway of an electrical impulse:
Receptor -> sensory neurone -> relay neurone -> motor neurone ->effector cell
What is the myelin sheath of neurones?
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
What the nodes of ranvier?
The nodes of ranvier are found between the gaps of adjacent schwaan cells
Myelinated motor neurones
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
Central nervous system
The central nervous system consists of your brain and spinal cord
Preipheral nervous system
The peripheral nervous system consists of all the neurones that connect to the CNS to the rest of the body
The somatic nervous system
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
The autonomic nervous system
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
Sympathetic nervous system
Sympathetic nervous system -> responsible for increased activity eg increased heart rate
-Fight or flight responses - neurotransmitter is noradrenalin
Parasympathic nervous system
Parasympathetic nervous system -> responsible for decreased activity eg heart rate after exercise
-Relaxing responses, neurotransmitter is acetylcholine
Features of sensory receptors
Features of sensory receptors:
-Specific to a stimulus
-Converts stimulus into nervous impulse
Types of sensory receptors
Types of sensory receptors:
-Mechanoreceptors = pressure/movement (stimulus = pacinian capsule)
-Chemoreceptor = chemical stimulus
-Thermoreceptor = heat stimulus
-Photoreceptor = light stimulus
What is a transducer?
Transducer = sensory receptor that converts stimulus into nervous impulse
Pacinian capsule
Pacinian capsule -> contains stretch-mediated sodium channels within the neurone -> when changing shape, the channel permeability changes
How the pacinian capsule converts mechanical pressure into impulse
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
What is resting potential?
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)
Why does resting potential occur?
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)
Process resulting in creation of a resting potential
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
What is action potential?
Action potential occurs when protein channels in axon membrane changes shape -> results in opening/closing of voltage-gated ion channels
Process of action potential
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)
What is a nerve impulse?
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
What occurs after action potential has passed?
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
Why is a refractory period impotrant?
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
What is saltatory conduction?
Saltatory conduction is a process where the action potential then jumps from one node to another where no myelin is present
->fast process
Factors that affect the speed at which an action potential travels
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)
‘All or nothing principle’ in terms of nervous impulses
nerve impulses - certain level of stimulus (threshold value) needed to trigger response - reaching this always creates action potential
Synapse structure
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)
