Unit 10: Coordination and Control Flashcards
What is system integration and what does it depend on?
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 eective 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.
What are the component subsystems of a cell?
Organelles
What is a tissue? What are the component subsystems of a tissue? How do these subsystems work together?
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.
What is an organ? What are the component subsystems of an organ? How do these subsystems work together?
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
What is an organ system? What are the component subsystems of an organ system? How do these subsystems work together?
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
What is an organism? What are the component subsystems of an organism? How do these subsystems work together?
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
Describe hormonal signalling in the endocrine system
- 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)
Describe nervous signalling in the neurons
- 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
What is the role of the brain?
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.
What is the role of the spinal cord? What makes up the spinal cord?
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
What is the difference between unconscious and conscious processes?
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
What is a non-binary action?
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)
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
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
What are nerves?
Nerve = bundle of nerve fibres surrounded by a sheath
–> contains both sensory and motor neurons (each can only transmit signals one way)
Explain a pain reflex arc
= involuntary response with skeletal muscle as the effector
- RECEPTORS
sense a stimulus - SENSORY NEURONS
receive signals from receptor cells/own sensory nerve endings - INTERNEURON
(outside CNS) neurons that go between sensory and motor neuron - MOTOR NEURON
receive signals via synapses with interneurons - EFFECTORS
carry out response to stimulus when signal from a motor neuron is received
–> 1. MUSCLES - contract
–> 2. GLANDS - secrete
What is a cerebellum and what is its role
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
What is melatonin/circadian rhythms?
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
What is ephinephrine and what is its role and effects?
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)
What are the hypothalamus and the pituitary gland
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
Explain osmoregulation and puberty in terms of system integration
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
Explain the feedback control of the heart rate
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
Explain feedback control of ventilation rate following sensory input from chemoreceptors
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
Explain the control of peristalsis in the digestive system by the CNS and the enteric nervous system
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)
What are tropisms and what types are there?
Tropism = growth response to stimuli
Positive tropism = growing towards stimulus
Negative tropism = growing away from stimulus
Explain positive phototropism
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
What is and what is the role/effects of a phytohormone?
Phytohormone = plant hormone that helps control growth, development and responses to stimuli in plants
- GROWTH
- can either promote or inhibit growth by affecting rates of cell division and cell enlargement (i.e. gibberelin causing stem elongation) - DEVELOPMENT
- promote or inhibit aspects of development (i.e. ethylene ripens fruits) - RESPONSE TO STIMULI
- control tropisms (i.e. auxins control phototropism)
What is auxin and what is an auxin efflux carriers?
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
Explain the promotion of cell growth by auxin
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
Explain the interactions between auxin and cytokinin
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
Explain positive feedback in fruit ripening
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
Compare receptors and enzymes
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
What is quorum sensing? Explain its process and give an example
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
What are the differences between hormones, neurotransmitters, cytokines and calcium ions?
All are functional categories of signalling chemicals in animals
- HORMONES (i.e. insulin, glucagon, testosterone, estrogen)
- come from endocrine glands
- target cells have receptor proteins
- long effect time - 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 - CYTOKINES (i.e. interferon)
- proteins that act as chemical messages within cells/between nearby cells
- can have multiple effects depending on binding site - 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
Explain the chemical diversity of hormones and neurotransmitters
Both are small, soluble, and have a shape compatible with a receptor.
HORMONES:
steroids, amines, peptides
NEUROTRANSMITTERS:
amines, amino acids, esters, gases
Explain the localised and distant effects of signalling molecules
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
What are the differences between transmembrane receptors in a plasma membrane and intracellular receptors in the cytoplasm or nucleus
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
What is a signal transduction pathway and how is it initiated by receptors? (transduction, intracellular, transmembrane pathways)
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
- TRANSMEMBRANE PATHWAY
- ligand binds with the receptor
- receptor changes shape
- produces secondary messenger molecules
- causes changes inside the cell
What are transmembrane receptors for neurotransmitters and what are the changes to the membrane potential? (1st type of transmembrane receptors)
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
What are transmembrane receptors that activate G proteins? (2nd type of transmembrane receptors)
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
What is the mechanism of action of epinephrine receptors
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
What are transmembrane receptors with tyrosine kinase activity (3rd type of transmembrane receptors)
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
What are the intracellular receptors that affect gene expression
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
What are the effects of oestradiol and progesterone on target cells?
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
Regulation of cell signalling pathways by positive and negative feedback
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)
What is a neuron and how do they work?
Neurons = cells within nervous system that carry electrical impulses
electrical impulses = electrical signal passed between 2 cells
Explain the generation of the resting potential by pumping to establish and maintain conc. gradients of Na+ and K+ ions
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
Explain nerve impulses as action potentials that are propagated along nerve fibres
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
Explain the variation in the speed of nerve impulses
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
What are synapses and what is the role of them
Synapse = gap between cells through which signals are passed by neurotransmitters
only 20nm wide
occur between neurons and between neurons and effectors
Explain the process of the release of neurotransmitters from a presynaptic membrane
- Action potential (wave of positive voltage) reaches the end of the presynaptic neuron
- Voltage gated calcium ion channels open
- Calcium ions enter the presynaptic neuron (facilitated diffusion)
- Ions force vesicles with neurotransmitters to fuse with the membrane
- Neurotransmitters released into the synapse (exocytosis)
- Neurotransmitters diffuse across synapse
- Bind to receptors on the postsynaptic membrane
- Ion channels open
- If enough ions enter the postsynaptic cell, that generates an action potential
- Neurotransmitter is removed from the synapse (either destroyed or moves back into presynaptic neuron)
Explain the generation of an excitatory postsynaptic potential
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
Explain the depolarisation and repolarisation during action potentials
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
Explain the propagation of an action potential along a nerve
fibre/axon as a result of local
currents
local current = movement of sodium ions between polarised and depolarised regions
What can you use to measure membrane potentials?
Oscilloscope = can measure membrane potentials using electrodes
What is saltatory conduction?
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
Explain the effect of exogenous chemicals on synaptic transmission
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
What are inhibitory neurotransmitters and explain the generation of inhibitory postsynapticpotentials
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.
What are summation of the effects of excitatory and inhibitory neurotransmitters in a postsynaptic neuron
- 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
explain the perception of pain by neurons with free nerve endings in the skin
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
discuss consciousness as a property
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
What is homeostasis?
Maintaining stable internal conditions regardless of fluctuations in the external environment
examples = body temp, blood pH
Explain the negative feedback loops in homeostasis
Homeostasis utilises negative feedback loops and uses energy but allows organisms to make use of a wider range of habitats
Explain blood glucose regulation as an example of the role of hormones in homeostasis. Which cells secrete the glucagon and insulin?
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
Describe the physiological changes that form the basis of type 1 and type 2 diabetes
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
What is thermoregulation?
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)
describe thermoregulation mechanisms in humans
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
Explain the role of the kidney in osmoregulation and excretion
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
What is the role of the glomerulus, Bowman’s capsule and proximal convoluted tubule in excretion?
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
What is ultrafiltration
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)
What is selective reabsorption
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
What is the role of the loop of Henle
Medulla has high solute concentration
Descending limb
- water exits via osmosis
Ascending limb
- not permeable to water
- sodium ions leave filtrate (active transport)
Explain osmoregulation by water reabsorption in the collecting ducts
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.
Describe the changes in blood supply to organs in response to changes in activity
Arterioles:
Vasoconstriction = reduce blood flow
Vasodilation = increase blood flow
BLOOD FLOW
1. SLEEP
Brain: high
Skeletal muscle: low
Digestive system: variable
Kidneys: low
- RESTING BUT AWAKE
Brain: moderate
Skeletal muscle: moderate
Digestive system: variable
Kidneys: very high - EXERCISE
Brain: high
Skeletal muscle: very high
Digestive system: low
Kidneys: low
