Introduction to neural control systems

Question 1

What are the main functions of the nervous system?

Answer 1

• Generate electrical signals
• Transmit those signals over distance
• Communicate with other cells
• Form complex circuits with one another

Question 2

What are neurones?

Answer 2

Nerve cells, the building blocks for neural circuits + cells that generate signals.

Their signals carry sensory information to the brain, not just from sense organs but from sensory receptors that monitor conditions within the body

Question 3

What are the structural features of nerve cells?

Answer 3

• Cell body
• Axon
• Dendrites

Question 4

What are the connections into the neuron provided by?

Answer 4

Dendrites

Question 5

What are the messages away from the neuron delivered by?

Answer 5

Axon, which can extend significant distance within the body.

Question 6

Describe a basic depiction of a neural circuit

Answer 6

• Nerve cell
• Axon
• White matter
• Grey matter
• Peripheral nerves

Question 7

What does the cell body contain?

Answer 7

• The nucleus and endoplasmic reticulum and is connected to the dendrites and axons in different ways depending on the function of the neuron

Question 8

How do neurons conduct messages?

Answer 8

• Electrically through propagation of an action potential along their length
• The threshold at which an AP is produced and the velocity that it’s propagated with varies from cell to cell

Question 9

What is the synapse formed of?

Answer 9

• Presynaptic membrane
• Synaptic gap
• Postsynaptic membrane

Question 10

Describe the presynaptic membrane

Answer 10

• This is on the cell producing the chemical message across the synapse and aiming to transmit an impulse to the postsynaptic cell, this is typically at the end of the axon, though this can vary
• There are VGCC on membrane which are activated by an action potential, which causes an influx of calcium ions and this activates the release of stored vesicles of neurotransmitter chemicals
• There are receptors on the outside of the presynaptic membrane that bind to neurotransmitters and facilitate re-uptake into the cell once the message transmission is complete

Question 11

Describe the synaptic gap

Answer 11

• Space between pre- and postsynaptic membrane
• Mostly empty to allow for efficient diffuse of neurotransmitters but can contain enzymes which degrade neurotransmitters to prevent their ongoing activity

Question 12

Describe the postsynaptic membrane

Answer 12

• Membrane of cell which is activated by neurotransmitter into synaptic gap. Typically this is on a dendrite of a particular neuron and one neuron can have multiple connections incoming from other neurons via multiple dendrites
• Postsynaptic membrane contains receptors for different neurotransmitters which are able to induce an action potential in the postsynaptic cell if enough activated
• There is also a concentration of voltage-gated ion channels to help propagate an action potential along the cell once the threshold is reached by neurotransmitter receptors being activated

Question 13

What constitutes the peripheral nerve cells?

Answer 13

• Axons leave CNS to make PNS

Question 14

What is myelination?

Answer 14

• A term in anatomy defined as process of forming a myelin sheath around a nerve to allow nerve impulses to move faster

Question 15

What makes up white matter?

Answer 15

• Myelinated axons
• Links areas of grey matter- axons only

Question 16

What makes up grey matter?

Answer 16

• Unmyelinated axons
• Packed with nerve cells
• Very connected

Question 17

What are the two types of axons in peripheral nerves?

Answer 17

• Sensory inputs (afferents) (towards CNS)
• Motor outputs (efferents) (towards PNS)

Question 18

What is the relationship between the CNS and PNS?

Answer 18

• Peripheral is connected to CNS
• Peripheral nerves innervate peripheral organs, but receive sensory information from CNS, and carry information to CNS.

Question 19

What is the difference between the somatic nervous system and autonomic nervous system?

Answer 19

• The somatic allows for voluntary control e.g. touch etc., autonomic is involuntary (breathing)

Question 20

What is the role of the cerebral cortex and hippocampus?

Answer 20

• Thinking part of brain
• Conscious perception, cognition, learning, memory, controlling voluntary movement
• Different area subserve different functions

Question 21

What is the corpus callosum?

Answer 21

• Largest white matter in brain, connects 2 hemispheres, permitting communication between left and right sides

Question 22

What is inside the diencephalon?

Answer 22

• Thalamus
• Hypothalamus

Question 23

What is the function of the thalamus?

Answer 23

• Relays signals to and from cerebral Cortex
• Also acts as general communication hub for cerebral cortex
• Sensory pathways synapse here on way to cortex
• Thalamic relays switched off during sleep

Question 24

What is the role of the hypothalamus?

Answer 24

• Controls homeostasis
• Links neural and endocrine systems
• Controls systems that regulate internal environment via autonomic nervous system
• Controls systems that generate sleep-wake cycle

Question 25

Discuss the importance of the brainstem

Answer 25

• Manages visceral function via ANS
• Manages transitions between different sleeping and waking states via modulatory pathways
• Work in partnership with cerebellum to fine-tune motor control (e.g. dexterity)

Question 26

What are the 3 parts of the brain stem?

Answer 26

• Midbrain
• Pons
• Medulla - becomes spinal cord once it reaches foramen magnum, made of grey matter

Question 27

What is the function of the spinal cord?

Answer 27

• Carries afferent and efferent axons for somatic and autonomic nervous systems (in white matter)
• Contains circuitry that generates basic motor patterns on behalf of brain