pulse sensor and ISR stops the rest of my code

Projects General Guidance
5

Something like this:

volatile unsigned int signal;
volatile bool haveSignal;

ISR(TIMER2_COMPA_vect){
  reading = analogRead(pulsePin);
  haveSignal = true;
}

void loop() {
  if (haveSignal) { // Yoo hoo! Got a new signal!
    haveSignal = false; // Record that we handled the new signal.
    noInterrupts();
    unsigned int signal = reading; // So to prevent the value from changing while we work onit.
    interrrupts();
    processSignal(signal);
  }
  // Whatever else loop() has to do.
}

void processSignal(unsigned int signal) {
  // Do something useful with your newly acquired data.
  // But don't take too long here or you will still miss events!
}