6.1 - Receptors, survival and response Flashcards
Define tropism
growth towards a directional stimulus
Name and describe the 2 types of animal response
- taxis (directional): movement directly towards/away from stimulus
- kinesis (non-directional): change in speed of movement + rate it changes direction
What is IAA?
indoleacaetic acid: a type of auxin (growth factor), so broken down by light
Describe the effect of auxin in shoots and roots
shoots: stimulates growth so causes cell elongation
roots: inhibits (slows, not stops) growth so prevents cell elongation
Describe the effect of auxin effect in terms of phototropism
shoots: IAA diffuses from shoot tip to shaded side, so cell elongation, so bends towards light source (positive phototropism)
roots: IAA inhibits elongation so roots elongate more on lighter side and root bends away from light (negative phototropism)
Describe the effect of auxin in terms of gravitropism
shoots: IAA diffuses from upper side to lower side, causes cells to elongate and plant grows upwards (if on its side, shoot will bend upwards) = negative gravitropism
roots: IAA diffuses to lower side of roots so upper side elongates and root bends towards gravity = positive gravitropism
How is IAA transported?
usually by diffusion (active transport for short distances) e.g through phloem
Define energy transducer
converts one type of energy into another
Describe the structure and features of rod cells
- found on retina except fovea
- rhodopsin photopigment
- 3 rods synapse to 1 bipolar neurone
- high light sensitivity
- low visual acuity
- mitochondria, RER, nuclei
Why can rods detect light of very low intensity?
- retinal convergence
- 3 rods connect to one bipolar neurone
- so summation of generator potentials
Describe the structure and features of cone cells
- found on fovea
- iodopsin photopigment
- monosynaptic: separate impulses sent to brain = can distinguish light sources as separate
- low light sensitivity: iodopsin requires high light intensity to be broken down and trigger A.P.
- high visual acuity
- mitochondria, RER, nuclei
- 3 types: sensitive to blue, green, red (each cone contains only one type to detect a certain wavelength of light)
Why does colourblindness occur?
brain interprets wrong colour cone
What is rhodopsin broken down by light energy into?
retinal and opsin
(can be resynthesised)
Suggest how muscles enable the pupil to constrict
- radial muscle relaxes
- circular muscle contracts
Describe how the heart coordinates the regular contraction of the atria and ventricles
- synoatrial node (SAN) sends wave of electrical activity across atria, causing atrial contraction
- non-conducting tissue prevents immediate contraction of ventricles
- atrioventricular node (AVN) delays impulse whilst blood leaves atria and ventricles fill
- AVN sends wave of electrical activity down Bundle of His/Purkyne fibres
- causing ventricular contraction from apex upwards
Explain how the heart muscle and valves maintain a one-way flow of blood from left atrium to aorta
- higher pressure in atrium than ventricle causing atrioventricular valves to open
- ventricle has a higher pressure than atrium causing AV valves to close
- ventricle has higher pressure than aorta causing semilunar valve to open
- higher pressure in aorta than ventricle causing SLV to close
- contraction causes increase in pressure
Define myogenic
can initiate its own contractions without any nervous stimulation
Describe the role of receptors and nervous system in detecting an increase in HR
- chemoreceptors detect rise in CO2/H+/acidity/carbonic acid/fall in pH OR baroreceptors detect rise in blood pressure
- MORE impulses sent to medulla
- MORE FREQUENT impulses from medulla to SAN
- by sympathetic NS (chemo) OR parasympathetic NS (baro)
NB: FEWER impulses to medulla when blood O2 high, blood pH high, CO2 low, BP low
How does the heart coordinate both ventricles so they contract at the same time?
- electrical activity only through Bundle of His
- wave of electrical activity passes through both ventricles at the same time
Give examples of stimuli
(animals): light, pressure, moisture
(plants): light, gravity, water
Name the 2 branches of nervous system of state what they consist of
central: brain, spinal cord
peripheral: receptors, sensory neurones, motor neurones
What is the typical threshold value for a pacinian corpuscle?
-55mV
Name the 2 branches of the peripheral nervous system
- somatic (conscious)
- autonomic (unconscious)
Define cardiac impulse
impulse heart generates to contract
Where is the sinoatrial node (pacemaker) found?
right atrium
Name the 2 types of autonomic response, their neurotransmitters, neurone locations, and type of receptors
parasympathetic (rest and digest):
- acetylcholine
- middle/lower spinal cord
- baroreceptors
sympathetic (fight or flight):
- noradrenaline
- brain and base of spinal cord
- chemoreceptors
Where are baroreceptors and chemoreceptors found?
- walls of carotid arteries
- aorta walls
- medulla (brain)
Which autonomic branch (parasympathetic or sympathetic) to increase, and decrease HR/blood pressure?
HR/blood pressure too low/want to increase: sympathetic
HR/blood pressure too high/want to decrease: parasympathetic
Describe the consequences of blood pressure being too high or too low
too high: artery wall damage
too low: insufficient supply of O2 blood to respiring cells and waste removal
Describe the cause and consequences of low pH
pH decreases when high respiratory rate due to CO2/lactic acid production
too low: enzymes denature
so HR is increased to make CO2 diffuse out of alveoli more rapidly to prevent denatured enzymes
Describe the role of the SAN
initiates heartbeat, acts as a pacemaker, stimulates atrial contraction
Define stimulus
something detected by an organism (internal or external)
Describe where the 3 types of neurones carry nerve impulses from and to
sensory: from receptor to spinal cord
relay: (found in spinal cord) from sensory to motor neurone
motor: from spinal cord to effector
Define receptor
organ/specialised cell that detects change caused by stimulus
Describe the features of receptors
- only respond to specific stimuli
- stimulation leads to establishment of generator potential
Suggest the advantages of simple reflexes
- quick response
- do not have to be learnt
- protect against damage to body tissues
- help escape from predators
- enable homeostatic control
Describe the structure of a Pacinian corpuscle
- sensory neurone
- sensory neurone ending
- gel between connective tissue (lamellae)
Describe how pressure affects a Pacinian Corpuscle
- stretch mediated Na+ channels open as stretched and deformed
- Na+ floods in down electrochemical gradient
- produces generator potential
- causes action potential when reaches threshold (max response no matter how much pressure is applied)
- greater pressure = more channels open
Movement of ions in and out of Pacinian Corpuscle
sodium potassium pump
- 3 sodium ions out
- 2 potassium ions in
cell is more permeable to K+ ions than Na+ ions
