Control of heart rate in humans

Learning outcomes:·outline the hormonal and nervous mechanisms involved in the control of heart rate in humans.

KEYWORDS:·Cell metabolism, ·myogenic, ·pacemaker, ·sino-atrial node (SAN), ·atrio-ventricular node (AVN), ·medulla oblongata, ·cardiovascular centre, ·sympathetic, ·parasympathetic, ·bradycardia, ·tachycardia, ·baroreceptors, ·adrenalin, ·noradrenalin

Sympathetic nervous systemParasympathetic nervous systemaccelerator nervevagus nervepressure, chemo, stretch and thermo receptors

·In what kinds of situations does cell activity increase? ·during exercise, stress, etc

·What are the three ways the heart responds in these situations? ·increased heart rate, increased strength of contraction, increased stroke volume

·What are the benefits of this response? ·oxygen and glucose reaches respiring cells more quickly, carbon dioxide and other waste removed more quickly

The heart adapts to meet the requirements of your cells in different situations

·create a poster entitled 'How does the brain control the heart?'·you can use the laptop, textbook has loads of information...consider the questions below- must be finished today!·What features of the heart influence heart rate?·What part of the brain influences heart rate? How?·Which hormone influences heart rate? How?

Co-ordinating Control:At rest, the SAN controls heart rate. It has a set frequency (60-80 action potentials per minute)

This can be modified/controlled by 1. The cardiovascular centre in the medulla:·Three receptor groups send inputs to the cardiovascular centre ·Two nerves link the cardiovascular centre with the SAN2. The hormone adrenaline

Produce a summary diagram to show what controls heart rate and

how.

Plenary Question:What are the consequences of an increase in CO2 concentration in the blood?

Plenary Question:What are the consequences of an increase in CO2 concentration in the blood?·decreased pH, due to increase in HCO3- / H+ ;·detected by chemoreceptos in carotid arteries aorta and brain·impulses sent from receptors to cardiovascular centre·cardiovascular sends increased frequency of impulses along accelerator nerve to SAN·increased frquency of action potentials from SAN·heart rate increases·increased stroke volume / stronger contraction ;·more / faster, removal of carbon dioxide ;·(blood carbon dioxide falls to) norm / set point ;·negative feedback / homeostasis ;·buffering effect of haemoglobin,

·What features of the heart influence heart rate? the muscle is myogenic, the SAN (pacemaker) generates an action potential which travels through the AVN and purkyne fibres

·What part of the brain influences heart rate? the medulla oblongata How? nerves from here affect the frequency of contractions; action potentials sent along the accelerator nerve increase heart rate, those sent along the vagus nerve decrease heart rate

·Which hormone influences heart rate? How? adrenaline, specific receptors exist on heart muscle cells, when adrenaline binds cAMP acts as the second messenger to create an effect