Nervous System 1

Question 1

Describe the nervous system.

Answer 1

• The body’s command centre
• Electrical and chemical communication occurs throughout the body

Question 2

State the two main parts of the nervous system.

Answer 2

1. Central Nervous System
2. Peripheral Nervous System

Question 3

What is involved in the CNS?

Answer 3

Brain and Spinal chord

Question 4

What is involved in the peripheral nervous system?

Answer 4

Afferent Nerves: sensory neurons - messages from periphery to spinal chord

Efferent Nerves: Motor neurons - messages from spinal chord to muscle/glands

Question 5

State the divisions of the peripheral nervous system

Answer 5

CNS - Sensory division (afferent) and motor division (efferent)
Motor division - Autonomic Nervous System and Somatic Nervous system
Autonomic Nervous System - sympathetic division and parasympathetic division

Question 6

What are the building blocks of the nervous system?

Answer 6

• Neuron
• Oligodendrocytes (CNS)/Schwann cells (PNS)
• Astrocytes
• Microglia

Question 7

Describe neurons.

Answer 7

Electrically excitable cell that receives, processes and transmits information through electrical and chemical signals.

Question 8

Describe oligodendrocytes (CNS)/Schwann cells (PNS)

Answer 8

• Produce myelin
• Facilitate transmission

Question 9

Describe astrocytes

Answer 9

• Enables homeostasis
• Physical barrier/connector
• Reputake of neurotransmitters
• Support neurons

Question 10

Describe microglia

Answer 10

• Immune cells of the brain
• Phagocytose dead cells and debris

Question 10

Describe the structure of neurons.

Answer 10

1. Cell body (soma): control centre
2. Dendrite: short, branched extension of a nerve cell where impulses received from other cells at the synapses and transmitted to the cell body
3. Axons: originate at axonal hillock and allows material to be transported from cell body to axon terminal
4. Synapse: Where axon terminal meets target cell

Question 11

Describe the signals of the neurons.

Answer 11

PNS - afferent or sensory neurons signals from the periphery to CNS

Efferent neurons - motor neurons signals from CNS to the muscle/skin

CNS - Interneurons connecting brain and spinal chord

Question 12

Define nerve.

Answer 12

• A bundle of fibres that conduct impulses between the brain and spinal chord and another part of the body
• Nerves include fragments of neurons (axons) and non-neuronal cells (neuroglia)

Question 13

What is the membrane potential?

Answer 13

The difference in electrical charge between the inside and the outside of the neuron
- is a result of ion gradients

Question 14

What are excitable cells?

Answer 14

Membrane potential changes in response to stimuli e.g. neurons

Question 15

What are nerve impulses?

Answer 15

Changes in membrane potential that travel down nerves

Question 16

Describe the features of the cell membrane.

Answer 16

• Highly impermeable to ions
• Allows electrical signalling and excitability

Question 17

State the types of transport across cell membranes.

Answer 17

• Passive diffusion
• Facilitated diffusion
• Active transport
• Secretory/endocytic pathways

Question 18

Describe the membrane potential of neurones?

Answer 18

• It is more negative on the inside than the outside of the cell
• Membrane potential is due to unequal ion distribution
• A gradient of ions across the membrane provides the membrane potential

Question 19

How do action potentials travel in neurones?

Answer 19

Travel one way - from dendrites to axons

Question 20

How does an action potential changes the membrane?

Answer 20

Changes it to +30mV

Question 21

How are electrical impulses formed?

Answer 21

By ions moving into the neruon

Question 22

How is the axonal action potential made up of?

Answer 22

Movement in sodium (+ charged ion) and potassium (+ charged ion)

Question 23

What does the signal received at dendrites cause?

Answer 23

• Causes dendritic depolarisation: ligand gated ion channels and metabotropic receptors
• This depolarisation opens voltage gated sodium channels

Question 24

What is the stimulus?

Answer 24

It can be electrical mechanical or chemical.

Question 25

Describe the all or nothing principle.

Answer 25

- Stimulus has to be strong enough to reach threshold potential - Enough depolarisation to open first Na channels - Sodium channels in the membrane are sensitive to voltage and open when the threshold membrane potential is reached

Question 26

Describe action potential propagation.

Answer 26

- The action potential Is propagated down the axon by voltage sensitive channels - Na+ voltage sensitive channels open due to local change in membrane potential - Causes more Na+ channels to open - Na+ channels behind the action potential become inactive - This means action potential can only move in ONE direction.

Question 27

Describe a synapse.

Answer 27

When one neurone meets another

Question 28

Describe how neurones form networks and communicate.

Answer 28

- Electrical action potential triggers release of chemical signal (neurotransmitter) - Neurotransmitters from the pre-synapse bind to postsynaptic receptors - This triggers depolarisation of the postsynpatic neurone

Question 29

What are the two ways synapses can be described?

Answer 29

Excitatory - stimulus in second neurone Inhibitory - Stimulus in 1st make an AP less likely to occur

Question 30

What is summation?

Answer 30

The combination of graded potentials in the post-synaptic neurone.

Question 31

State and describe the structures of the brain.

Answer 31

Cerebrum - Higher functions Brain Stem - Involuntary functions, blood pressure, breathing, vomiting, sleep/arousal - includes the midbrain, pons and medulla Cerebellum - co-ordinates balance and movement Diencephalon - Homeostasis - its between brain stem and cerebrum and includes thalamus, hypothalamus and pineal gland.

Question 32

Describe the cerebrum: cortex.

Answer 32

* 2 hemispheres joined by corpus callosum * Surface folded * Frontal: reasoning, planning, speech, movement, problem solving * Parietal: movement / orientation recognition, sensory information (pain) * Occipital: visual processing * Temporal: perceptions/recognition of auditory stimuli

Question 33

Describe the cerebrum: sub-cortical structures.

Answer 33

* Basal ganglia: motor control * Limbic system: - Amygdala: emotion and memory - Hippocampus: Learning and memory (under temporal lobe) * Pituitary gland: a small gland located at the base of the brain below the hypothalamus - growth hormone, TSH

Question 34

State the four regions of the spinal chord.

Answer 34

- Cervical - Thoracic - Lumbar - Sacral

Question 35

Describe the function of the spinal cord.

Answer 35

* Connects your brain to your lower back * Carries nerve signals from your brain to your body and vice versa * Spinal cord is where information comes into the CNS and directions are sent out

Question 36

What is the distinct pattern of the spinal cord.

Answer 36

- Sensory nerves enter via dorsal root - Motor nerves leave via ventral root

Question 37

Describe the spinal cord peripheral nerves.

Answer 37

(branches off from spinal cord). Spinal nerve: a mixed spinal nerve, which carries motor, sensory, between the spinal cord and the body. Paired peripheral nerves that arise from the spinal cord. In humans there are 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each pair connects the spinal cord with a specific region of the body.