15.1 - Neurones And Nervous Coordination Flashcards
What are the two main forms of coordination in animals? Describe each.
1) Nervous System
- Utilises nerve cells to pass electrical impulses, stimulating target cells through neurotransmitters.
- This results in rapid, localized responses that are short-lived.
- Example: Reflex actions like withdrawing a hand from a hot surface.
2) Hormonal System
- Produces hormones transported via blood plasma to target cells with specific receptors.
- This results in slower, less specific communication with long-lasting and widespread effects.
- Example: Regulation of blood glucose concentration.
Describe the structure of a mammalian motor neurone.
1) Cell Body: Contains organelles like the nucleus and rough endoplasmic reticulum for protein production.
2) Dendrons: Extensions that subdivide into dendrites, carrying nerve impulses towards the cell body.
3) Axon: A single long fiber that transmits impulses away from the cell body.
4) Schwann Cells: Surround the axon for protection and electrical insulation, involved in phagocytosis and nerve regeneration.
5) Myelin Sheath: Formed by Schwann cell membranes, rich in myelin, insulating the axon.
6) Nodes of Ranvier: Gaps between Schwann cells, about 2-3 µm long, occurring every 1-3 mm, allowing for faster nerve impulse conduction.
What are the different types of neurones and what are their functions
- Sensory Neurones: Transmit impulses from receptors to intermediate or motor neurones. They have one long dendron and one axon.
- Motor Neurones: Transmit impulses from intermediate neurones to effectors (glands/muscles), characterized by a long axon and many short dendrites.
- Intermediate (Relay) Neurones: Transmit impulses between other neurones, such as from sensory to motor neurones, with numerous short processes.
Describe the role of Schwann cells in the structure and function of neurones.
- Schwann cells surround the axon of neurones, providing protection and electrical insulation.
- They are responsible for the formation of the myelin sheath, which consists of multiple layers of Schwann cell membranes rich in myelin, enhancing the speed of nerve impulse transmission.
- Additionally, Schwann cells perform phagocytosis to remove cellular debris and facilitate nerve regeneration.
Explain the significance of the nodes of Ranvier in myelinated neurones.
- The nodes of Ranvier are gaps in the myelin sheath of myelinated neurones that allow for saltatory conduction, where nerve impulses jump from one node to the next.
- This significantly increases the speed of conduction of electrical impulses along the axon compared to non-myelinated neurones, enhancing the efficiency of the nervous system.
Which neurone is it?
Which neurone is it?
Which neurone is it?
Fill in the gap:
Neurones are adapted to carry electrochemical charges called (1). Each neurone comprises a cell body that contains a (2) and large amounts of (3), which is used in the production of proteins and neurotransmitters. Extending from the cell body is a single long fibre called an axon and smaller branched fibres (4). Axons are surrounding by (5) cells, which protect and provide (6) because their membrane are rich in a lipid known as (7). There are 3 main types of neurone. Those that carry nerve impulses to an effector are called (8) neurones. Those that carry impulses from a receptor are called (9) neurones and those that link the other two types are called (10) neurone.
1) nerve impulses / action potentials
2) nucleus
3) rough ER
4) dentrites
5) Schwab cells
6) insulation
7) Myelin
8) motor
9) sensory
10 intermediate
What is the myelin sheath made from
- originates from the Schwann cell
- 80% proteins; 20% lipid
- no ion channels
- forms 250 layers
- prevents ion movement into and out of the axon
