13.6-13.8 and 14.5 -14.6

Question 1

What are the main two structural systems?

Answer 1

• Central Nervous System: brain and spinal cord.
• Peripheral nervous system: neurones that connect the CNS to the rest of the body. E.g sensory neurones and motor neurones

Question 2

What two functional systems does the peripheral nervous system have?

Answer 2

• SOMATIC: This system is under conscious control and is used when you voluntarily decide to do something e.g moving your arm
• AUTONOMIC: This system works constantly and is under subconscious control, involuntary E.g heartbeat

Question 3

Which two systems is the autonomic nervous system split into?

Answer 3

• Sympathetic: ‘Fight or flight’ system

- Parasympathetic: ‘Rest and digest’ system

Question 4

Which neurotransmitter do sympathetic neurones release?

Answer 4

Noradrenaline

Question 5

Which neurotransmitter do parasympathetic neurones release?

Answer 5

Acetylcholine

Question 6

What are the five main areas of the brain?

Answer 6

• Cerebrum
• Hypothalamus
• Medulla oblongata
• Cerebellum
• Pituitary gland

Question 7

What is the role of the cerebrum?

Answer 7

• Controls voluntary actions e.g learning, memory, personality, conscious thought

Question 8

What is the role of the cerebellum?

Answer 8

• Controls unconscious functions such as posture, balance and non-voluntary movement

Question 9

What is the role of the medulla oblongata?

Answer 9

• Used in autonomic control e.g heart rate and breathing rate

Question 10

What is the role of the hypothalamus?

Answer 10

• Regulatory centre for temperature and water balance

Question 11

What is the role of the pituitary gland?

Answer 11

• Stores and releases hormones that regulate many body functions

Question 12

What are the two parts of the pituitary gland?

Answer 12

• Anterior pituitary

- Posterior pituitary

Question 13

What is the role of the anterior pituitary gland?

Answer 13

Produces six hormones, including follice-stimulating hormone, which is involved in reproduction and growth hormones

Question 14

What is the role of the posterior pituitary gland?

Answer 14

Stores and releases hormones produced by hypothalamus, such as ADH

Question 15

What is a reflex?

Answer 15

A reflex is an involuntary response to a sensory stimulus.

Question 16

What type of reflex is the knee-jerk reflex?

Answer 16

A spinal reflex- the neural circuit only goes up to the spinal cord

Question 17

What importance does the knee-jerk reflex have on survival value?

Answer 17

It helps to maintain posture and balance, allowing you to remain balanced with little effort or conscious thought.

Question 18

How does the knee-jerk reflex work?

Answer 18

1) When the leg is tapped just below the kneecap it stretches the patellar tendon. The stretch receptors detect this and a nerve impulse is passed along the sensory neurone.
2) This stimulus initiates a reflex arc that causes the extensor muscle on top of the thigh to contract.
3) At the same time, a relay neurone inhibits the motor neurone of the flexor muscle, causing it to relax.
4) This contraction coordinated with the relaxation causes the leg to kick.

Question 19

What is the blinking reflex?

Answer 19

The blinking reflex is an involuntary blinking of the eyelids.

Question 20

What is the purpose of the blinking reflex?

Answer 20

• To keep the cornea safe from damage- corneal reflex

- To keep lens and retina safe- optical reflex

Question 21

What type of reflex is the blinking reflex?

Answer 21

A cranial reflex- it occurs in the brain only

Question 22

How does the blinking reflex work?

Answer 22

1) When the cornea of the eye is irritated by a foreign body e.g dust, the stimulus triggers an impulse along a sensory neurone (the fifth cranial nerve).
2) The impulse passes through a relay neurone in the lower brain stem and sent along branches of the motor neurone (seventh cranial nerve) to initiate a motor response to close the eyelids.
3) The reflex initiates a consensual response- this means both eyes are closed in response to the stimulus,

Question 23

Why are reflexes essential for survival?

Answer 23

They avoid the body being harmed or reduce the severity of any damage.

Question 24

How do reflexes increase your chances of survival?

Answer 24

• Being involuntary responses: The decision making regions of the brain are not involved, therefore the brain is able to deal with more complex responses. It prevents the brain from being overloaded with situations where the response is always the same.
• Not having to be learnt: Present at birth and provide immediate protection
• Extremely fast

Question 25

Once a threat is detected by the autonomic nervous system, what does the hypothalamus do?

Answer 25

• The hypothalamus communicates with the sympathetic nervous system and adrenal-cortical system.
• sympathetic nervous system uses neuronal pathways to initiate body reactions whereas the adrenal-cortical system uses hormones in the bloodstream.
• The combined effects results in flight or fight response.

Question 26

What does the sympathetic nervous system do?

Answer 26

The sympathetic nervous system sends out impulses to glands and smooth muscles, and tells the adrenal medulla to release adrenaline and noradrenaline into the bloodstream.

Question 27

What does the pituitary gland do?

Answer 27

The hypothalamus stimulates the pituitary gland to secrete ACTH, which travels in the blood stream to the adrenal cortex activating the release of many hormones that prepare the body to deal with a threat.

Question 28

What are the physiological responses of the fight or flight?

Answer 28

Heart rate increases, pupils dilate, arterioles in skin constrict, blood glucose level rises, digestion inhibited

Question 29

Why do arterioles constrict in the fight or flight response?

Answer 29

So that more blood can be sent to major muscle groups e.g brain, heart

Question 30

What is adrenaline’s main function?

Answer 30

• Adrenaline’s main function during the fight and flight response is to trigger the liver cells to undergo glycogenolysis so that glucose is released into the bloodstream.
• This allows respiration to increase so more energy is available for muscle contraction.

Question 31

Outline how adrenaline works.

Answer 31

1) When adrenaline binds to its receptor on liver cell membrane, the enzyme adenylyl cyclase is activated.
2) Adenylyl cyclase triggers the conversion of ATP into cAMP.
3) The increase in cAMP levels activates enzymes called protein kinases which phosphorylate and activate other enzymes. E.g enzymes which trigger conversion of glycogen into glucose are activated.

Question 32

What are the two centres within the medulla oblongata?

Answer 32

1) Cardioacceleratory centre: Increases heart rate by sending impulses through sympathetic nervous system.
2) Cardioinhibitory centre: Decreases heart rate by sending impulses through parasympathetic nervous system.

Question 33

What are the two types of receptors that affect heart rate?

Answer 33

1) Baroreceptors (pressure receptors)- Detect changes in blood pressure
2) Chemoreceptors (chemical receptors)- Detect changes in level of particular chemicals e.g carbon dioxide

Question 34

Where are baroreceptors located?

Answer 34

Aorta, vena cava & carotid arteries

Question 35

Where are chemoreceptors located?

Answer 35

Aorta, carotid artery

Question 36

What happens when blood pressure is too high?

Answer 36

• Impulses sent to cardioinhibitory centre in medulla oblongata.
• Medulla oblongata sends impulses to SAN along parasympathetic neurones which decreases heart rate.

Question 37

effect of exercise on cardiac output / What happens when carbon dioxide level in blood increases?

Answer 37

• increased muscular/metabolic activity
• more carbon dioxide in tissues from increased respiration
• centre in medulla oblongata that speeds up heart rate (cardiostimulatory centre) increases frequency of impulses and sends it down accelerator nerve to SAN (via sympathetic nervous system)
• SAN increases heart rate
• increased blood flow removes carbon dioxide faster
• carbon dioxide levels return to normal