receptors and controlling heart rate Flashcards
how is generator potential established in pacinian corpuscle
mechanical stimulus eg pressure deforms stretch mediated sodium ion channels
so na channels in membrane open and na diffuse into sensory neurone
greater pressure causes more na channels to open and more na enter
= depol leading to generator potential
if GP reaches threshold ap triggered
what does the pacinian corpuscle illustrate
receptors only respond to specifc stimuli
pacinian corpuscle only respond to mechanical pressure
stimulation of a receptor leads to establishment of GP - threshold met ap sent (all or nothing principal)
differences in sensitivity of light for rods and cones in retina
rods more sensitive to light - several rods connected to single neurone
spatial summation to overcome threshold to generate AP
but cones are less sensitive to light as each cone connected to single neurone so no spatial summation
differences in visual acuity of rods ad cones
rods - lower visual acuity as several rods connected to single neurone
several rods send single set of impulses to brain and the brain cant distinguish between the separate sources of light
cones high visual acuity - each cone connected to single neurone so cones send separate set of impulses to brain so it can distinguish between the separate sources of light
differences to sensitivity to colour for rods and cones
rod - monochromatic vision - 1 type of rod so one pigment
cones allow colour vision as red green and blue with Dif optical pigments so absorb Dif wavelengths of light and stimulates diff combos of cones gives a range of colour perception
cardiac muscle is myogenic?
contracts and relaxes without receiving electrical impulse from nerves
Describe the myogenic stimulation of the heart and transmission of a
subsequent wave of electrical activity
SAN acts as pacemaker
sends regular waves of electrical activity across atria causing it to contract simultaneously
non conducting tissue between atria and ventricles prevents impulse passing directly to ventricles preventing immediate contraction of ventricles
waves of electrical activity reach AVN - delays impulse
allowing atria to fully contract and empty before ventricles contract
AVN sends waves of electrical activity down bundle of his conducting wave between ventricles and apex where it branches into purkyne tissue
causing ventricles to contract simultaneously base up
Where are chemoreceptors and pressure receptors located?
aorta
carotid arteries
Describe the roles of chemoreceptors, pressure receptors, the autonomic
nervous system and effectors in controlling heart rate
parasympathetic
parasympathetic nerves are involved in decreasing heart rate.
baroreceptors detect rise in bp
chemoreceptors detect fall in blood co2 conc or rise in blood ph
sends impulses to medulla
which sends more frequency impulses to SAN along parasympathetic neurones
so less impulses from SAN to AVN
so cardiac muscle contracts less frequently
and heart rate decreases
sympathetic
involved in increasing heart rate
baroreceptors detect fall in blood pressure and rise in blood co2 conc or fall in ph
sending impulse to medulla
which sends more frequent impulses to SAN along sympathetic nerve so more frequent impulses sent from san to AVN
so cardiac muscle contracts more frequently and heart rate increases
when heart beats both ventricles contract at same time
how is this coordinated in the heart after initiation of heart beat by san
electrical activity through bundle of his
waves of electrical activity pass over both ventricles at the same time
Diabetes can damage the nervous system. Use your knowledge of the control of heart rate by the nervous system to suggest an explanation for these results.
damage to autonomic nervous system
so baroreceptors dont work properly
damage to medulla
damage to sympathetic nervous system - doesnt speed up as much
explain how nervous control in a human can cause increased cardiac output
Coordination via medulla
Increased impulses along sympathetic nerve to SAN
More impulses sent from SAN
Some drugs inhibit the transmission of nerve impulses to the heart. Explain how these drugs reduce high blood pressure.
inhibit impulse in sympathetic nerves
SAN not stimulated so heart treat cant increase
Describe the route taken when electrical impulses are transmitted from the sinoatrialnode to the muscles of the ventricles in a healthy heart
through cardiac muscle
to AVN
along bundle of his
