control systems Flashcards
how are resting potentials maintained
- with a sodium potassium pump
- sodium moves out, potassium in
- gated sodium channels close to prevent moving in
- outside more positive than inside
- is polarised
role of rhodopsin in light
- bleaches into retinal and opsin
- opsin blocks gated na + channels
- rod cell hyperpolarises
- no IPSP released
negative feedback description
- change occurs and is detected
- leads to the activation of a mechanism that reverses the change
- conditions return to ideal and mechanism switches off
positive feedback description
- change is detected, communication system informs effector system causing a reaction
- cycle repeats e.g blood clotting
what are endocrine glands and give example
- ductless that release hormones into blood
- adreneline - heart pumps faster, lungs increase breathing rate, blood vessels constrict, liver breaks down more glycogen, more muscle contraction
features of steroid hormones
- lipid soluble/cross membrane
- bind in cytoplasm forming TFs
- move to nucleus and binds to promotor region
- RNA polymerase transcribes
- takes longer to effect
features and action of peptide/amide hormones
- polar
- binds to receptors on cell membrane
- cAMP releases inside cell and triggers protein activation cascade
- existing inactive proteins can activate others to bring change
role of auxins
elongates cells in meristem due to larger turgor pressure and increases cell plasticity
therefore bend towards light, exist on shaded
produced in apex
role of cytokinins
stimulate meiosis and lateral bud growth - attaches to receptors on membrane to form transcription factors
forms shoots
apical dominance
- apex grows to access light
- lateral buds inhibited as apex dominates - auxin produced to grow stem
- cytokinins produced at auxillary buds for lateral stems
- auxin transported down to prevent gene activation of cytokinins
role of giberellic acid
- controls internode length and seed development
- reinforces auxins and stem growth
- end dormancy, grows in embryo
- DELLA proteins bind to TFs to keep seeds dormant
- when GA increases, amylase increaes, GA bind to DELLA which stops the inhibition of TFs
ending seed dormancy
- uptake of water causes GA formation and diffuses into food stores
- binds to DELLA - no inhibition
- transcription of genes
- food stores hydrolysed and transported to embryo
what are phytochromes
photoreceptor pigment that are blue/green and a conjugated protein
types of phytochromes
Pr - absrobs red (shorter) light
Pfr - far red (longer) light
changes r to fr in sunlight, slower change fr to r in darkness
long day and short day plants
long - Pfr is active, promotes the flowering gene - ft mRNA
short - PFR inhibits formation of ft mRNA
how impulses travel through central nervous system
stimuli
receptors
sensory neuron
motor neuron
effector muscle/gland
response
role of spinal cord
relay action potentials between receptors and effectors
role of cerebrum
voluntary responses, initiates movement and higher activity
role of medulla
controls heart rate vessel diameter and breathing
role of cerebellum
involuntary movement and fine motor
role of hypothalamus ad pituitary
links endocrine and nervous
in osmo and thermoregulation
differences between motor and sensory neurons
motor have shorter dendrons (before cell body) and longer axons (after)
sensory have cell body in midde, motor have at the end
the process of action potentials
- stimulus causes gated na + channels to open, and they diffuse though conc gradient into cell
- -55mv triggers depolarisation as na + flood in and inside becomes more positive and potential difference reaches +40mv
- repolarisation - na channels close and k+ open to let it exit the cell so inside is less positive
- hyperpolarisation when too many leave - k+ close
transmission of action potentials
- at nodes of ranviar where myelin is exposed
- saltatory conduction where na+ jumps across myelin
- after aps na+ diffuses high to low along to next node
- negative ions move back to AP (+ attracted to -)
- potential difference occurs when na+ arrives and cl- leaves
- causing gates to open and causes local current
what increases transmission speed of APs
- myelinated
- temperature
- axon diameter/amount of membrane
transmission at synapses
- AP at pre-synaptic knob
- ca2+ channels open and move in
- vesicles move to pre synaptic membrane and release transmitter via exocytosis
- NT diffuses across cleft, binds with receptors on ion channels (open) in post membrane
- na rush in post synaptic neuron and depolarise
deactivation at synapses with enzymes
- cholinesterate hydrolyses ADH to create choline and ethanoic acid
- ion channels of post membrane closes to restore resting
- products enter pre-synaptic and recombine with ATP
role and example excitatory neurotransmitter (EPSPs)
glutamate and ach
- causes na+ gates to open to cause depolarisation and can easily diffuse across synapse
role and example inhibitory neurotransmitter (IPSPs)
GABA
- attaches to receptor sites, cl- channels open and move in making it more -
- cant reach threshold
action of lidocaine
- local anaesthetic
- blocks na+ channels
- post synaptic neurone cannot depolarise and AP for pasin can’t travel to brain
action of cobra venom
- irreversible binding to ach receptors on post synaptc membrane
- na+ gates stay open and cells can’t repolarise
action of nicotine
- binds with ach receptors
- more ach produced - synapses excited - alert
- dopamine also released
rods vs cones
rods - even spread, low light, black and white mostly, convergence, rhodopsin
cones - less, more further back, high intensity light, colour, high acuity, idopsin
rod cells in the dark
- na+ actively pumped inner to outer segment through channels for a gradient
- na+ flows into pre synaptic membrane and causes depolarisation
- IPSP released to prevent depolarising
rods in dim light
- rhodopsin bleaches into retinal and opsin
- opsin closes gated na+ channels so can only pump out
- cell hyperpolarizes and no IPSP released
cones in light
uses idopsin to bleach
opsin closes na channels and cell hyperpolarises
how heart rate is controlled
sympathetic nerve is connected to SAN from accelorator region, releases noradreneline that binds to receptors
vagus nerve connects to SAN from inhibitory region and releases ach
increasing heart rate
- increased cos and lactate in blood lowers ph
- detected by chemoreceptors in arteries and send an AP to stimulate accelerator region
- travels down SAN
reducing heart rate
- baroreceptors in carotid artery, aorta and atrium detect high blood pressure
- AP stimulates inhibitory region, Ap travels to vagus and SAN, releasing ach to lower hr
what is ADH
a peptide hormone that binds to receptors on the collecting duct, the 2nd messenger triggers insertion of aquaporins- an integral protein to increases permeability
osmoregulation loop
- change is detected by the hyperthalamus
- too much water= pituitary gland secretes less ADH, less permeable, unconcentrated urine
- too little water = p gland secretes more adh, duct more permeable and has concentrated urine
thermoregulation in ectotherms and reptiles
- physiological and behavioural adaptations
- use less food in respiration, more energy for growth
- more vulnerable
thermoregulation in endotherms and mammals
- hypothalamus has thermo regulatory centre
- in low temp the heat gain centre inhibits less centre, sent via sympathetic nerve
- vasocontriction: vessels close to skin constrict so less flow to surface
- hair traps heat
- high temp: loss inhibits gain and sent via parasympathetic
- sweat takes away heat in evaporation
fate of amino acids in the liver
- glucogenesis in the liver - urea is a product
- deamination - breaking down excess amino acids by removing the amino group to produce urea
structure of a nephron
afferent and efferent arteriole
bowmans capsule and glomerulus
proximal convulated tubule
loop of henle
distal convulated tubule
collecting duct
medulla
ultrafiltration
- in endothelium of bowmans capsule capillary
- amino acids, mineral ions, glucose, urea and water is filtrate
- high hydrostatic pressure pushing blood into bowmans and low pushing back
- oncotic pressure into glomerulus
selective reabsorption
- proximal tubule
- moves glucose, aa, and water from lumen of pct cells to peritubular capillary but NOT urea
- sodium potassium pump from pct to capillary (3:2 na out k in)
- binds sodium with a specific molecule to travel across - gradient
water reabsorption
- loop of henle
- low water potential in medulla, filtate in henle
- surrounded by lots of blood vessels called vasa recta to reabsorb water and exchange 02 c02
- descending limb is permeable, water leaves by osmosis and is reabsorbed into blood
- ascending limb permeable to ions - actively pumped out and reenter descending
blood ph and ion rebsorption
distal convulated tubule
- h+ oh- and hco3 ions adjusted - ph is 7.35-.45
- selective reabsorption of useful ions using cotransporter proteins
- eg calcium and chloride
collecting ducts
collecting ducts
- permeability directed by adh
