Fight or flight response and heart rate

Question 1

During fight or flight response, what does the pituitary gland release?

Answer 1

Pituitary gland is stimulated to release a hormone called ACTH,

which causes the cortex of the adrenal gland to release steroidal hormones.

Question 2

Once the sympathetic nervous system is activated, what is released?

Answer 2

Adrenaline is released from the medulla region of the adrenal gland.

Question 3

How is the body affected after adrenaline is released? ( 5 things)

Answer 3

1) Heart rate increases- blood pumped faster
2) Muscles around the bronchioles relax- DEEPER BREATHING
3) Glycogen is converted into glucose- so more glucose is available for glucose to respire ( Glycogenolysis)
4) arterioles constrict in the gut and skin, but the arterioles supplying the skin, heart, lungs and skeletal muscles DILATE, so more blood is diverted from the skin and gut to the heart, lungs etc
5) Erector pilli muscles in the skin contract, causing hairs to stand on end and the animal looks bigger.

Question 4

How the nervous system controls heart rate?

Answer 4

• SAN generates electrical impulses that cause the cardiac muscles to contract
• the rate at which SAN fires is unconsciously controlled by a part of the brain called the “Medulla”
• Animals alter their heart rate to respond to internal stimuli, e.g. preventing fainting when blood pressure is low, or to make sure heart rate is high enough to supply the body with enough oxygen.
  1) The stimuli are detected by pressure receptors and chemical receptors.
  2) The electrical impulses from the receptors are sent along sensory neurones to the medulla
• 3)THE MEDULLA then processes this information and sends impulses to the SAN along motor neurones

Question 5

Few facts about the SAN and heart rate:

Answer 5

• SAN generates electrical impulses that cause the cardiac muscles to contract
• the rate at which SAN fires is unconsciously controlled by a part of the brain called the “Medulla”
• Animals alter their heart rate to respond to internal stimuli, e.g. preventing fainting when blood pressure is low, or to make sure heart rate is high enough to supply the body with enough oxygen.

Question 6

what are baroreceptors?

Answer 6

They are pressure receptors that are stimulated by high or low BLOOD PRESSURE

Question 7

What are chemoreceptors?

Answer 7

Chemical receptors

That monitor oxygen and CO2 levels in the blood as well as the pH of the blood.

Question 8

What happens when a stimulus is high (e.g. high blood pressure) GENERAL RULE

Answer 8

• Receptors detect high pressure
• impulses are sent to the medulla, which sends impulses along the VAGUS NERVE
• Acetylcholine is secreted, which binds to receptors on the SAN.
• Heart rate decreases to help get blood pressure back to normal level.
• FOR EVERY CASE CARDIAC MUSCLES ARE ALWAYS THE EFFECTORS

Question 9

What happens when stimulus is too low : (e.g. low -oxygen conc, high C02 conc in the blood or low pH)

Answer 9

• Receptors detect CHEMICAL changes in the blood
• impulses are sent to the medulla, which sends impulses along the ACCELERATOR NERVE
• Noradrenaline is secreted , which binds to receptors on the SAN
• Heat rate increases to return O2 CO2 and pH levels back to normal