control of heart rate

Question 1

what is the definition of myogenic

Answer 1

its a STIMULATION of the heart and transmission of a WAVE OF ELECTRICAL ACTIVITY.- it stimulates itself rather than a nerve

Question 2

summaries and include specific details of the contraction of the hear

Answer 2

• SAN- specific muscle tissue carries WAVE OF ELECTRICAL ACTIVITY across the atria causing them to contract
• WAVE OF ELECTRICAL ACTIVE reaches AVN- it DELAYS they electrical wave to allow the ventricles to fill up before contracting
• WAVE OF ELECTRICAL ACTIVITY travels down ‘BUNDLE OF HIS’- then branches to the ‘Purkyne’ tissue fibres- which carry the wave of electrical activity to the ventricles from the bottom up then back up the walls of the heart where there’s NON-CONDUCTIVE TISSUE (between atria & ventricles)- This STOPS the immediate contrasting of ventricles when SAN is stimulated

Question 3

What are the roles and locations of chemoreceptors and pressure receptors

Answer 3

chemoreceptors are located in the AORTA & WALLS IN CAROTID ARTERY(in the neck)- ROLE; to detect the change/DROP in PH in the blood (due to the Co2 dissolving in the blood)
Pressure receptors (Pacinian Corpuscle) They are present in the DEEP SKIN mainly in fingers, soles of the feet ROLE;to detect pressure change

Question 4

Define a receptor

Answer 4

A stimulus is a detectable change in the environment. These changes can be detected by cells called receptors
EACH RECEPTOR responds to only A SPECIFIC STIMULI -leads to a ESTABLISHMENT OF A ACTION POTENTIAL/ GENERATED POTENTIAL-Causes the response

Question 5

describe the structure of a Pacinian Corpuscle

Answer 5

a SINGLE SENSORY NEURONE WRAPPED with a CONTINOUS LAYER OF TISSUE which are separated by GEL.
-the sensory neurone has a special channel proteins in its plasma membrane

Question 6

describe how the structure of the Pacinian Corpuscle is adapted to its function

Answer 6

• Plasma membrane-contains channel proteins which allow ion transportation
• Membrane surrounding the sensory neurones have STRECH-MEDIATED SODIUM CHANNELS- these will open to allow sodium ions to enter the sensory neurone only when they are STRECHED AND DEFORMED if enough sodium ions diffuse into the neurone to reach the threshold it can cause ACTION POTENTIAL

Question 7

Describe how the Pacinian Corpuscle initiates an action potential

Answer 7

when Pacinian corpuscle is in the resting state- Na+ channels are too narrow for Na+ to diffuse into sensory neurone - Resting potential maintained
When pressure is applied it DEFORMS THE NEURONE PLASMA MEMBRANE which causes the STRECH-MEDIATED CHANNELS open allowing sodium ions to diffuse into the sensory neurone- establishes a generator potential

Question 8

explain the roles of receptors and the nervous system which causes an increase in heart rate

Answer 8

• increasing in CO2 dissolves in blood- DROPS PH
• Chemoreceptors detect the drop in the aorta & carotid artery
• this causes MORE IMPULSES to be sent to the MEDULLA
• Send more IMPULSES to the SAN
• by the SYNTHETIC NERVE- which increases your heart rate

Question 9

explain how heart rate decreases after exercising

Answer 9

• Chemoreceptors detect the DECREASE in CO2
• so FEWER IMPULSES sent to the medulla
• which sends MORE IMPULSES to the SAN
• BY PARASYNTHETIC NERVE

Question 10

Q; EXPLAIN HOW BLOOD PRESSURE IS MEASURED

Answer 10

• PRESSURE RECEPTORS detect a rise in blood pressure
• MORE IMPULSES sent to the MEDULLA
• therefore MORE IMPULSES SENT to SAN
• by PARASYMPATHETIC NERVES-to lower heart rate

IF blood pressure is to low:

• pressure receptors detect a decrease in blood pressure
• FEWER IMPULSES sent to the MEDULLA
• therefore MORE IMPULSES sent to the SAN
• by SYNTHETIC NERVES

Question 11

what are plasma membranes

Answer 11

the same thing as cell-surface membranes