receptors Flashcards
what features are common to all sensory receptors?
- act as energy transducers which establish a generator potential
- respond to specific stimuli
describe the basic structure of a pacinian corpuscle
- single nerve fibre surrounded by layers of connective tissues which are separated by viscous gel and contained by a capsule
- stretch-mediated Na+ channels on plasma membrane
- capillary runs along base of layer tissue
what stimulus does a pacinian corpuscle respond to? how?
- responds only to specific stimuli
- pressure deforms membrane causing stretch mediated Na+ ion channels to open
- if influx of Na+ raises membrane to threshold potential, a generator potential is produced
- action potential moves along sensory neurone
name the 2 types of photoreceptor cell located in the retina
- cone cells
- rod cells
where are the rod and cone cells located in the retina?
rod: evenly distributed around periphery but not in the central fovea
cone: mainly central fovea no photoreceptors at blind spot
compare and contrast rod and cone cells (pacl)
- pigment
- ROD: rhodopsin
- CONE: 3 types of iodopsin - visual acuity
- ROD: low resolution because many rod cells synapse with 1 bipolar neurone
- CONE: high resolution because 1 cone cell synapses with 1 bipolar neurone so no retinal convergence - colour sensitivity
- ROD: monochromatic, all wavelenghts of light detected
- CONE: tricolour, blue green red wavelengths absorbed by different types of iodosin - light sensitivity
- ROD: very sensitive, spatial summation of sub-threshold impulses
- CONE: less sensitive, not involved in night vision
outline the pathway of light from a photoreceptor in the brain
photoreceptor → bipolar neurone → ganglion cell of optic nerve → brain
define myogenic
contraction of heart is initiated within the muscle itself rather than by nerve impulses
state the name and location of the 2 nodes involved in heart contraction
- sinoatrial node (SAN): within the wall of the right atrium
- atrioventricular node: near lower end of right atrium in the wall that separates the 2 atria
describe how heartbeats are initiated and coordinated
- sinoatrial node initiates a wave of depolarisation
- wave of depolarisation spreads across both atria causing atrial systole
- layer of fibrous, non conducting tissue delays impulse whilst ventricles fill and valves close
- atrioventricular node conveys wave of depolarisation down septum via Bundle of His, which branches out into Purkinje fibres along ventricles
- causes ventricles to contract from apex upwards
state the formula for cardiac output
cardiac output = stroke volume x heart rate
name the receptors involved in changing heart rate and state their location
- baroreceptors: detect changes in blood presure, carotid body
- chemoreceptors detect changes in pH, carotid body and aortic body
how does the body respond to an increase in blood pressure?
- baroreceptors send more impulses to cardioinhibitory centre in the medulla
- more impulses to sinoatrial node down vagus nerve via paraysympathetic nervous system
- stimulates release of acetylcholine which decreases heart rate
how does the body respond to a decrease in blood pressure
- baroreceptors send more impulse to cardioaccelatory centre in medulla
- more impulse to sinoatrial node via sympathetic nervous system
- stimulates release of noradrenaline which increases heart rate and strength of contraction
how does the body respond to an increase in CO2 concentration?
- chemoreceptors detect pH decrease and send more impulse to cardioacceleratory centre of the medulla
- more impulse to a sinoatrial node via the sympathetic nervous system
- heart rate increases so the rate of blood flow to the lungs increases
- rate of gas exchange and ventilation rate increase
