Nervous system wk 1-2

• Maintain homeostasis (BALANCE!!) with ELECTRICAL signals

• Provide for sensation + higher mental functions and emotions + activates muscles and glands

• Involuntary response vs voluntary response

  • Involuntary - Heart beating, sweating etc.

  • Voluntary - Screaming

• Roles of nervous system:

  1. Sensory input (gathering info)

     1. Monitors changes occurring inside AND outside the body (the changes acts as a STIMULI)

  2. Integration:

     1. Processes and interprets sensory input and decide if action is needed

  3. Motor output

     1. A response to integrated stimuli

     2. Activates muscles (contracts it or extends it e.g.)

• Structural classification of the nervous system

  • Central nervous system (CNS)

    • Brain + spinal chord

    • Command centre

    • Takes IN info and gives instruction

  • Peripheral nervous system (PNS) --> Schwann cells: Form myelin sheath in the PNS (need to diagram and label!!)

    • Nerves outside the brain and spinal cord

    • Communication lines

• Subcategories:

  • Sensory (afferent) Division

    • Nerve fibres that carry information TO the central nervous system (telling our brain how to react)

  • Motor (efferent) division

    • Somatic (voluntary) --> Walking, running, facial expressions e.g.

      • Somatic sensory fibres

      • Somatic motor fibres

      • Voluntary actions

    • Autonomic (involuntary) --> Heartrate, sweating e.g.

      • Involuntary functions

      • Visceral motor

      • Visceral sensory

    • Sympathetic division (fight or flight) --> Involuntary

      • Regulates heart beating, and breathing e.g.

    • Parasympathetic division (rest and digest)

      • Responding to dangerous situations

• Neurons = nerve cells

  • Cells specialised to transmit messages

• Neuron anatomy (Need to know diagram + label!!):

  • Cell body

    • Nucleus

    • Large nucleolus

  • Axonal terminal connected to muscle fibres + research more on the diagram

• Extensions outside the cell body

  • Dendrites conduct impulses toward the cell body

  • Axons conduct impulses away from the cell body (only one!!)

• Axons end in axonal terminals

• Axonal terminals contain vesicles with neurotransmitters

• Axonal terminals are separated from the next neuron by a gap

  • Synaptic clef: gap between adjacent neurons (between cells) is where learning occurs (increased learning efficiency) --> Less distance the neurotransmitters travel = better memorisation/making muscle react correspondingly (muscle memory!!)

  • Synapse: Junction between joints (where info is passed) --> immediate reaction

• Nerve fibre coverings

  • Schwann cells produce myelin sheaths (Vaseline coating around a wire e.g.) in jelly-roll like fashion

  • Nodes of Ranvier are gaps in myelin sheath along the axon (research diagram + labels)

    • In multiple scleroses, the myelin sheath is destroyed (instead of waxy and vaselin like, it becomes solid --> affects how the body functions (autoimmune disease --> movement becomes more difficult e.g.)

• Neuron cell body location

  • Mostly found in the central nervous system

    • Gray matter (research) are cell bodies and unmyelinated fibres

    • Nuclei are clusters of cell bodies within the white matter (research) of the CNS

  • Ganglia are collections of cell bodies outside the CNS

• Classification of neurons

  • Sensory (afferent) neurons --> carry impulses from the sensory receptors

  • Motor (efferent) neurons --> carry impulses from the central nervous system to muscles and glands (an organ that makes one or more substances, such as hormones, sweat, saliva e.g.)

    • Endocrine glands = release substances IN the bloodstream

    • Exocrine glands = release substances OUT of the bloodstream

• Neuronal Structure

  • All contain the same key structural components --> the cell body, dendrites, the axon and the axon terminals

    • Cell body: Holds the nucleous

    • Dendrites: Elongated portions of the cell body. Extend outwards and receives input from the environment and from other neurones

    • Axons: long, thin structure down which action potentials are conducted (although neurones have many dendrites, most cells only have ONE axon)

      • Coated in myelin

      • Gaps formed by different cells are the nodes of ranvier

    • Axon terminals: Neurone sends chemical signals to other cells

      • Contain large number of mitochondria (facilitates the secretion of neurotransmitters)

• Functional classification of neurons

  • Interneurons (association neurons/relay neurons)

    • Found in neural pathways in the CNS

    • Connects sensory and motor neurons

• Central Nervous System (CNS)

  • Develops from the embryonic neural tube

    • Neural tube becomes the brain and spinal cord

    • Openings of the neural tube becomes ventricles

      • Four chambers within the brain

      • Filled with cerebrospinal fluid

• There are four regions of the brain

  • Cerebral hemispheres

  • Diencephalon

  • Brain stem

  • Cerebellum

Example: Falls into shallow river and breaks spinal cord

From where the spine was broken, neurons cannot get information from the brain to the body (if it happens have waist length, then all the legs and feet won't move due to information not able to be transmitted around the body)

Action potential:

• Rapid short-lasting electrical signal that travels along the neuron's axon, enabling communication between nerve cells

  • Involves sudden change in neuron's membrane potential

• The electrical signal is important for transmitting info throughout the nervous system

What happens when schwann cells solidify?

• Lose its ability to form myelin sheath or participate in nerve repair

  • Can happen due to various factors, like aging, disease, or injury

• Impacts nerve function + regeneration