Nervous System

Question 1

A number of different proteins are involved in nerve function. Which does not require a membrane potential?

Answer 1

Diffusion of the neurotransmitter across the synapse

Question 2

Between which structures do sensory neurons carry nerve impulses

Answer 2

From receptors to the CNS

Question 3

What are the changes in the membrane potential during an action potential ?

Answer 3

1. ) Na+ ions diffuse in; inside becomes more positive

2. ) K+ ions diffuse out; inside becomes more negative

Question 4

What causes the formation of a nerve impulse on the post-synaptic membrane?

Answer 4

Neurotransmitter binding with receptor sites

Question 5

Functions of the medulla oblongata

Answer 5

Controls automatic and homeostatic activities (swallowing, digestion, vomiting, breathing and heart rate)

Question 6

Functions of the hypothalamus

Answer 6

Maintains homeostasis via coordination of the nervous and endocrine systems, produces hormones secreted by posterior pituitary

Question 7

Outline how endorphins act as painkillers

Answer 7

• Endorphins are produced by the pituitary gland that functions as the body’s natural painkiller
• Endorphins are typically released by the body during periods of stress, injury or physical exercise
• Pain is perceived in body tissues when impulses are sent from pain receptors to sensory areas of the brain
• Endorphins bind to opiate receptors on pre-synaptic neurons to block the transmission of pain signals

Question 8

Describe different aspects of the processing of visual stimuli

Answer 8

Photoreceptors (rod and cone cells) in the retina convert light into nerve impulses
- The impulses pass to bipolar cells, which relay the signal to the optic nerve (via ganglion cells)
Edge Enhancement sends signals from rods and cones, follow both vertical and lateral pathways
- Photoreceptors stimulate opposing bipolar cells but inhibit adjacent bipolar cells (lateral inhibition)
- This makes light spots lighter and dark spots darker, with the contrast greatest at the edges (edge enhancement)

Contralateral processing is when stimuli is processed on the opposite side of where it was detected

• Information from the left half of the visual field is detected by the right half of the retina in both eyes and is processed by the right hemisphere
• Information from the right half of the visual field is detected by the left half of the retina in both eyes and is processed by the left hemisphere
• At the optic chiasma, information from both eyes may swap so that the left or right visual field is processed together
• The optic nerves that swap sides are transmitting signals contralaterally, while the optic nerves that do not swap are transmitting signals ipsilaterally
• Impulses continue to the thalamus where the optical information is processed before an image forms in the visual cortex

Question 9

List two types of human sensory receptors

Answer 9

Mechanoreceptors: respond to mechanical forces and movement found in the eyes
Chemoreceptors: responds to chemical substances found in the nose/tongue

Question 10

What is the role of the hypothalamus in homeostasis?

Answer 10

Monitoring body temperature

Question 11

Between which structures do sensory neurons carry nerve impulses

Answer 11

From receptors to the CNS

Question 12

Which part of the brain has a role in the control of the heartbeat and how are message passed from this part of the brain to the heart?

Answer 12

part of the brain: medulla

type of message: nerve

Question 13

What causes the formation of a nerve impulse on the post-synaptic membrane?

Answer 13

Neurotransmitters binding with receptor sites

Question 14

Which event directly leads to an action potential?

Answer 14

Membrane potential reaches the threshold potential

Question 15

What is the effect of a neonicotinoid pesticide on the transmission of a nerve impulse between neurons in an insect?

Answer 15

It irreversibly binds with ACh receptors on the postsynaptic membrane

Question 16

How does potassium move across the membrane of a neuron during repolarization?

Answer 16

Facilitated diffusion

Question 17

Neurons transmit electrical impulses. Which statement describes part of this process?

Answer 17

Ion channels let Na+ diffuse into the cell to depolarize the membrane

Question 18

What is essential for conduction of nerve impulses to be saltatory?

Answer 18

Wrapping of myelin around the axon

Question 19

If schizophrenia is caused by an overabundance of the neurotransmitters dopamine and serotonin in the synapses of some area of the brain, which drug action could work in treating he symptoms?

Answer 19

Increased re-uptake of dopamine and serotonin by presynaptic neurons

Question 20

Distinguish using examples between innate and learned behaviors

Answer 20

Innate behavior is inherited from parents and so developing independently of the environment. Example: palmar grasp reflex: if an object touches the skin in the palm of a baby’s hand, the baby grips the object by closing its fingers around it
Learned behavior is acquired information from past experiences to adapt to new situations.
Example: human offspring inherit the capacity to learn a language, most of the time its a different language. The ability to make sense of vocal patterns and language spoken

Question 21

Using two examples, discuss how the process of learning can improve survival

Answer 21

The process of learning can improve survival as animals learn to stay away from predators and stay close to their group.
Imprinting: is learning occurring at a particular life stage and is independent of the consequences of behavior
- Imprinting occurs during a short critical period in which the organism adopts behavioural characteristics from a stimulus
- Filial imprinting - bonding to the parent - gooses learn to identify their mothers and learn to stay together

Operant Conditioning: is a form of learning which consists of trial and error experiences
- Lambs learn not to touch electric fencing, they explore their environment, and if electric fencing is used to enclose their flock, lambs sooner or later touch it, with their nose. They receive a painful electric shock, through operant conditioning they avoid touching the fence in the future

Question 22

Type of receptor cell that detect sound as well as an example

Answer 22

mechanoreceptors: hair cells in the cochlea

Question 23

Outline the role of inheritance and learning in the development of birdsong in young birds

Answer 23

The development of birdsong in young birds involves both innate and learned behaviors
Most birds are born with a crude template song that is genetically inherited (innate behaviour)
- The possession of an innate template prevents birds from adopting the songs of a different species of bird
- Whilst young, fledglings learn to expand and refine their song by listening to, and mimicking, the adult version (motor learning)
- Birds raised in isolation will lack the necessary song complexity that develops through social interaction
- The time taken to develop a birdsong differs between species and songs, but once established, the final song is rarely altered

Question 24

Outline Pavlov’s experiments into conditioning in dogs

Answer 24

Pavlov’s experiment is a form of classical conditioning where he experimented on dogs.

• Dogs normally salivate (unconditioned response) in anticipation of being fed (unconditioned stimulus)
• Pavlov sounded a bell (neutral stimulus) prior to feeding a dog
• After many repetitions, the dog came to associate the bell with food and began to salivate to the bell (conditioned response)
• Pavlov described this as a conditioned reflex – the stimulus that prompted the response had been changed

Question 25

Example of excitatory and an inhibitory psychoactive drug

Answer 25

excitatory: nicotine : Nicotine raises dopamine levels in the brain (leading to addiction) and activates parasympathetic pathways
inhibitory: THC : By preventing the inhibition of dopamine secretion, THC causes a sense of euphoria and emotional well-being

Question 26

Explain the processing of visual stimuli

Answer 26

Contralateral processing is when a stimulus is processed on the opposite side to where it was detected

• Information from the right half of the visual field is detected by the left half of the retina in both eyes and is processed by the left hemisphere, vice versa
• Information from each eye may swap at the optic chiasma, so that the right or left visual field is processed together
• The optic nerves that swap sides are moving contralaterally, while those that stay on the same side remain ipsilateral
• Impulses are conducted by the optic nerve to the thalamus, before being transmitted to the visual cortex (occipital lobe)
• Thalamic structures (e.g. lateral geniculate nuclei) are involved in coordinating eye movements and circadian rhythms

Question 27

Explain how sound is perceived by the ear

Answer 27

• Sound travels as pressure waves in the air which push the membrane of the eardrum, causing it to vibrate
• The degree of vibration will vary according to the frequency and amplitude of the sound waves
• The ear drum pushes on the bones of the middle ear (the ossicles), which magnify the vibrations
• The bones of the middle ear are known as the hammer (malleus), anvil (incus) and stirrup (stapes)
• The ossicles push against the oval window, displacing fluid within the cochlea
• Movement of the cochlear fluid affects the position of cilia on sensory hair cells
• Cilia on hair cells vary in length and each resonates to a different frequency of sound
• Activation of the hair cells generates nerve impulses which are transmitted via the auditory nerve to the brain
• The kinetic motion of the cochlear fluid is dissipated by the movement of the round window

Question 28

Outline an example illustrating adaptive value of foraging behavior patterns

Answer 28

Shore crabs are adaptive to the foraging behavior patterns.

• Shore crabs main food source is mussels.
• Big mussels have tons of meat but take much of the crab’s energy by opening them.
• With smaller mussels, they require less energy, but have less meat.
• The crabs became adaptive by finding that intermediate mussels were best fit as they require less energy as well as having perfect amount of meat
• This adaptive foraging allows the crabs to scavenge for food much faster and effectively

Question 29

Explain the effects of cocaine in terms of its action at synapses in the brain and its social consequences

Answer 29

• Cocaine acts indirectly on dopamine, which is involved in the brain’s reward pathway
• Cocaine blocks the dopamine re-uptake pump in the presynaptic terminal
• Consequently, dopamine remains active in the synapse, continuing to bind to postsynaptic receptors and causing excitation
• Suppresses appetite and enhances endurance / energy levels
• Sense of euphoria and mellowness
• Long-term use associated with medical complications and severe mental disorders
  
  • lead to loss of jobs, and distant from family

Question 30

Explain the process involved with the creation of the neural tube in chordates

Answer 30

The formation of a neural tube in embryonic chordates occurs via the process of neurulation

• Cells located in the outer germ layer (ectoderm) differentiate to form a neural plate
• The neural plate then bends dorsally, folding inwards to form a groove flanked by a neural crest
• The infolded groove closes off and separates from the neural crest to form the neural tube
• The neural tube will elongate as the embryo develops and form the central nervous system (brain and spinal cord)
• The cells of the neural crest will differentiate to form the components of the peripheral nervous system

Question 31

Describe the importance of neural plasticity in the development of the human brain

Answer 31

Neuroplasticity describes the capacity for the nervous system to change and rewire its synaptic connections
- Neuroplasticity enables individuals to reinforce certain connections (learning) or circumvent damaged regions