Nervous System part 1

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Questions and Answers

What is the primary function of dendrites in neurons?

To form myelin sheaths around nerve fibers

To transmit impulses away from the cell body

To provide structural support to the neuron

To receive information and pass it to the cell body (correct)

Which type of glial cell is primarily responsible for forming and maintaining myelin in the central nervous system?

Oligodendrocytes (correct)

Microglia

Ependymal cells

Astrocytes

What substance is primarily responsible for crossing the blood-brain barrier quickly?

Large molecules

Inorganic ions

Many drugs

Oxygen and glucose (correct)

What role do synaptic vesicles play in neurotransmission?

To store neurotransmitters Signup and view all the answers

What is the main characteristic of astrocytes in the central nervous system?

They provide a structural framework and support to neurons Signup and view all the answers

Which neurotransmitter is specifically mentioned in the content in relation to synapses?

Acetylcholine Signup and view all the answers

What characteristic defines the irritability of neurons?

The ability to initiate impulses in response to stimuli Signup and view all the answers

What do microglia do in response to inflammation and cell destruction?

Increase in number and become phagocytic Signup and view all the answers

What is the primary function of Schwann cells in the peripheral nervous system?

To provide myelin insulation to axons. Signup and view all the answers

Which of the following correctly describes the role of the nodes of Ranvier?

They assist in the rapid transmission of action potentials. Signup and view all the answers

Which division of the nervous system responds to external stimuli?

Peripheral nervous system. Signup and view all the answers

What best describes the function of the cell body in a neuron?

It houses the nucleus and organelles. Signup and view all the answers

Which component of the nervous system is primarily responsible for involuntary responses?

Autonomic nervous system. Signup and view all the answers

What are action potentials primarily generated by?

Changes in ion permeability of the neuron's membrane. Signup and view all the answers

Which of these characteristics is NOT associated with myelinated neurons?

Slower transmission of action potentials. Signup and view all the answers

Which of the following describes the central nervous system?

Consists of the brain and spinal cord. Signup and view all the answers

Study Notes

Nervous System Overview

The nervous system detects and responds to internal and external changes in the body.
It works alongside the endocrine system to control body function and maintain homeostasis.
The nervous system provides immediate responses, while endocrine activity is slower and prolonged.

Nervous System Divisions

The nervous system is divided into the central and peripheral systems:
- Central Nervous System (CNS): Brain and spinal cord
- Peripheral Nervous System (PNS): All other nerves

Peripheral Nervous System Divisions

The PNS is further divided into sensory and motor divisions:
- Sensory Division: Carries sensory information from the body to the CNS
- Motor Division: Carries motor commands from the CNS to the body
  - Somatic Nervous System: Voluntary control of skeletal muscles
  - Autonomic Nervous System: Involuntary control of internal organ functions
    - Sympathetic Nervous System: "Fight or flight" response
    - Parasympathetic Nervous System: "Rest and digest" response

Nervous Tissue: Cells

Nervous tissue consists of three main cell types:
- Neurones: Specialized cells that transmit nerve impulses
- Schwann Cells: Supporting cells that form the myelin sheath around axons in the PNS
- Neuroglial/Glial Cells: Supporting cells of the CNS

Neurone Structure

Neurones have distinct structural features:
- Cell Body: Contains the nucleus and other organelles
- Axon: Long, slender projection that conducts nerve impulses away from the cell body
- Schwann Cells: Wrap around axons to form the myelin sheath
- Nodes of Ranvier: Gaps between Schwann cells, facilitating rapid impulse transmission
- Dendrites: Short, branched projections that receive nerve impulses from other neurones
- Synaptic End Bulb: Terminal of the axon, containing neurotransmitters

Neurone Properties

Neurones exhibit two key properties:
- Irritability: Ability to initiate nerve impulses in response to stimuli
- Conductivity: Ability to transmit nerve impulses

Neuroglial (Glial) Cells

Neuroglial cells are non-excitable cells that support neurones in the CNS.
They continue to replicate throughout life.
There are three main types:
- Microglia: Phagocytic cells that remove debris and pathogens
- Astrocytes: Star-shaped cells that provide structural support and regulate nutrient and waste exchange
- Oligodendrocytes: Form and maintain myelin sheaths around axons in the CNS

Blood-Brain Barrier

The blood-brain barrier is a selectively permeable membrane that protects the brain from toxic substances and blood fluctuations.
It allows the passage of essential substances like oxygen, carbon dioxide, glucose, and lipid-soluble molecules.

Synaptic End Bulbs and Neurotransmission

Synaptic end bulbs are specialized structures at the end of axons, responsible for transmitting nerve impulses to other neurones or effector cells.
They contain synaptic vesicles that store neurotransmitters, such as acetylcholine and noradrenaline.
Neurotransmission occurs through the release of neurotransmitters at the synapse.

Synapse

The synapse is the junction between two neurones or a neurone and an effector cell.
It consists of:
- Pre-synaptic Neurone: Releases neurotransmitters
- Pre-synaptic Knob: Terminal of the axon containing synaptic vesicles
- Neurotransmitters: Chemical messengers released at the synapse
- Post-synaptic Knob: Receptor sites on the receiving cell
- Post-synaptic Neurone: Receives the neurotransmitter signal

Neuro-transmission

Neurotransmission involves a series of steps:
- Action Potential Arrival: Nerve impulse reaches the pre-synaptic knob
- Calcium Influx: Calcium ions enter the pre-synaptic knob
- Neurotransmitter Release: Synaptic vesicles fuse with the pre-synaptic membrane and release neurotransmitters
- Neurotransmitter Binding: Neurotransmitters bind to receptors on the post-synaptic membrane
- Post-synaptic Potential: Binding triggers a change in the post-synaptic cell's membrane potential
- Neurotransmitter Removal: Neurotransmitters are removed from the synapse, either by re-uptake into the pre-synaptic neurone or by enzymatic breakdown.