Blood pressure is the product of cardiac output and total peripheral resistance:
$\text{BP} = \text{CO} \times \text{TPR}$
Since cardiac output is the product of heart rate and stroke volume, we have:
$\text{BP} = \text{HR} \times \text{SV} \times \text{TPR}$
Stroke volume is determined by preload, contractility, and afterload. An increase in afterload leads to a reduction in stroke volume and thus a decrease in blood pressure. [1]
However, it then seems that hypertension, which increases afterload, would lead to a decrease in blood pressure and form a negative feedback loop. Is this in fact what happens in the human body?
Also, when total peripheral resistance increases, it seems to me that afterload should increase, leading again to a reduction in blood pressure. Nonetheless, peripheral resistance also directly determines blood pressure ($\text{BP} = \text{CO} \times \text{TPR}$). Which of these has a stronger effect?
1: http://pie.med.utoronto.ca/CA/CA_content/CA_cardiacPhys_strokeVolume.html