Lesson 3: CNS and Hormonal Control of the heart Flashcards
What are the 3 main factors affecting the SAN?
1 - Sympathetic nervous system
2 - Parasympathetic nervous system
3 - Medulla oblongata
Define sympathetic system.
A part of the autonomic nervous system that increases HR.
Define parasympathetic system.
A part of the autonomic nervous system that decreased HR.
Define medulla oblongata.
The most important part of the brain as it egulates processes that keep us alive such as breathing and HR.
What does the sympathetic nervous system do? (in detail)
- Increases HR by releasing adrenaline.
- Adrenaline increases the strength of ventricular contraction which then increases SV.
- Noradrenaline aids the spread of electrical impulse throughout the heart increasing HR.
- Increased metabolic activity causes increased concentration of CO2 and lactic acid, decreasing PH of blood.
- These changed are pciked up by chemoreceptors and inform the sympathetic centre to increase HR to flush out the waste products.
- This results in an INCREASED CARDIAC OUTPUT.
What does the parasympathetic nervous system do? (in detail)
- Slows down the speed of heart impulses which decreases HR.
- Releases acetylcholine which slows the spread if the impulses throughout the heart.
- This results in lower HR.
Sympathetic vs Parasympathetic, what are their differences?
Sympatheitc Nerves: “fight or flight”
- dilate pupils
- inhibit saliva
- increase heart beat
- relax airways
- inhibit activity of stomach
- simulate release of glucose; inhibit gallblader
- inhibit activity of intestines
- secrete epinphrine and norepinephrine
- relax bladder
Parasympathetic Nerves: “rest and digest”
- constrict pupil
- stimulate saliva
- decrease heart beat
- constrict airways
- stimulate activity of stomach
- inhibit release of gluscose; stimulate gallbladder
- stimulate activity of intestines
- contract bladder
What is the neural control mechanisms?
- Involves the sympathetic system and the parasympathetic system.
- Made up of two parts: Central Nervous System (CNS) which consists of the brain and spinal cord and the Peripheral Nervous System which consists of nerve cells that transmit infro to and from the CNS.
- These 2 systems are co-ordinated by the cardiac control centre located in the medulla oblongata.
- The cardiac control centre is stimulated by chemoreceptors, baroreceptors and proprioceptors.
Define receptors.
- They are biological transducers that convert energy from both external and internal environments into electrical impulses. They detect a change in the environment and stimulate electrical impulses in response.
Name the 3 receptors.
Chemoreceptors
Baroreceptors
Proprioceptors
What are chemoreceptors?
- Found in carotid arteries and aortic arch.
- Sense chemical changes.
- During exercise, they detect an increase in CO2.
- Role of blood CO2 is important in controlling the HR.
- An increase concentration of CO2 will stimulate the sympathetic nervous system, which means heart will beat faster.
What are baroreceptors?
- Contain nerve endings to respon to thestretching of the arterial wall caused by changes in BP.
- Establish a set point for BP.
- An increase or decrease below the set point triggers the barrecpetors to send a signal to the medulla oblongata in the brain.
- An increase in arterial pressure causes an increase in the stretch of baroreceptor sensors and resutls in a decrease in HR. (vice versa)
- At the start of exercise, the set point increases because the body doesnt want the HR to slow down as this would negatively affect performance - less oxygen delivered to working muslces.
What are proprioceptors?
- Sensory nerve endings located in muslces, tendons and joints that provide info about movement and body position.
- At the start of exercise, they detect an increase in muscle movement. They then send an impulse to the medulla, which then sneds an impulse through the sympathetic nervouse system to the SAN to increase HR.
- When the parasympathtic system stimulates the SAN, HR decreases.
What is the hormonal contol mechanism?
- Hormones can have an effect on exercise.
- The release of adrenaline during exercise is known as hormonal control.
- It’s a stress hormone released by the sympathetic nerves and cardiac nerve during exercise.
- It stimulates the SAN which results in a increase in speed and force of contraction, increasing cardiac output.
- Results in more blood being pumped to the working muscles so they can receive more oxygen for the energy they need.
Define ejection fraction.
The percentage of blood pumped out by the left ventricle per beat.
