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A2 biology edexcel

A2 biology edexcel

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  • 1. Nervous system
    • Starter activity
    • List the differences between endocrine and nervous system
  • 2. Endocrine and nervous system Long term Short term Effect Fast Slow Response Nerves Blood Transport method Nervous system Endocrine system Properties
  • 3. Nervous system
    • Learning objectives
    • Understand the structure and function of the nervous system
    • Understand the structure and function of the neurones
    • Understand the role Schwann cells and process of myelination
  • 4. Nervous system
    • The nervous system is made up of 2 systems (central nervous system and peripheral nervous system)
    • The central nervous system consists of 2 main areas
    • (brain, spinal cord)
    • The peripheral nervous system consists of the following areas
    • (afferent (sensory) nervous system, efferent (motor) nervous system, somatic nervous system, autonomic nervous system, sympathetic division, parasympathetic division)
  • 5. Central nervous system
    • The central nervous system is made up of the brain and spinal cord
    • This is where the integration of the sensory information with the receptors will allow the appropriate response
  • 6. Peripheral nervous system
    • The peripheral nervous system is made up of the following areas
    • Afferent nervous system : Deals with sensory part of the nerve pathway (give an example)
    • Efferent nervous system : Deals with motor part of the nerve pathway (give an example)
    • Somatic nervous system : Carries the nerve impulse to skeletal muscles (give an example)
    • Autonomic nervous system : Carries the nerve impulse to smooth muscles ( give an example)
    • Sympathetic division : Active during times of stress. Its actions during the stress response comprise the fight-or-flight response, allowing the pupils to dilate
    • Parasympathetic division : Active during times of relaxation. Its actions during relax response comprise the rest-and-digest response, allowing the pupils to constrict
  • 7. Sympathetic & Parasympathetic
    • These systems (Sympathetic and parasympathetic divisions) typically function in complementary to each other. For an analogy, one may think of the sympathetic division as the accelerator and the parasympathetic division as the brake. The sympathetic division typically functions in actions requiring quick responses. The parasympathetic division functions with actions that do not require immediate reaction. Consider sympathetic as "fight or flight" and parasympathetic as "rest and digest".
    • However, many instances of sympathetic and parasympathetic activity cannot be ascribed to "fight" or "rest" situations. For example, standing up from a reclining or sitting position would entail an unsustainable drop in blood pressure if not for a compensatory increase in the arterial sympathetic tonus. Another example is the constant, second to second modulation of heart rate by sympathetic and parasympathetic influences, as a function of the respiratory cycles. More generally, these two systems should be seen as permanently modulating vital functions, in usually antagonistic fashion, to achieve homeostasis. Some typical actions of the sympathetic and parasympathetic systems are listed below:
  • 8.
    • Sympathetic nervous system Parasympathetic nervous system
    • 1. Transmitter used is noradrenaline / Transmitter used is acetylcholine
    • norepinephrine;
    • 2. Increases (frequency / rate) of Reduces (frequency / rate / speed)
    • depolarisation at SAN of depolarisation at SAN ;
    • 3. Increases the heart rate Decreases the heart rate ;
    • 4. Increases strength of / stronger / Decreases the amplitude of /
    • increases amplitude of / more decreases the strength of / less forceful} heart beat forceful heart beat ;
    • 5. Is activated during activity or periods of stress Controls when at rest ;
  • 9. Neurones
    • The entire nervous system is made up of 2 types of cells
    • Neurones : Which carry the nerve impulses
    • Neuroglia : (Schwann cells) which provide structural and metabolic support to the neurones
    • Each neurone consists of
    • Nucleus surrounded by granular cytoplasm (perikaryon)
    • Cytoplasm contain granules (nissl substances) and dense amount of ER
    • Cytoplasm processes occur from the (cell body) axon to the dendrites
    • Axon carries impulse from the body of the cell to other neurones or effectors (muscle)
    • Dendrites, branched which carry impulses from receptors or neurones across the synapse
  • 10. Neurones
  • 11. Neurones
    • Multipolar neurones : Have many dendrites from the body cell (effectors motor neurones)
    • Bipolar neurones : Have a single dendrite from the body opposite the axon
    • (receptors of sight, smell, and balance)
    • Pseudo-unipolar neurones : Also have a single dendrite and the cell body branches from the stem. (sensory neurones)
  • 12. Neurones
    • The axon is surrounded by specialised cells referred as (Schwann cells). During the fetal development stage, the Schwann cells wrap around the axon which is referred as the (myelin sheath). The region in between the Schwann cells are known as (nodes of ranvier) which allow the neurone exposure to extracellular fluid. The speed of conduction of the nerve impulse is proportional to the diameter of the axon the diameter varies between (1-20 micrometer). The conduction speed also varies between an axon being myelinated and non-myelinated. The myelin sheath provides an insulation to the electrical impulse and prevents any impairment, leakage or loss of the electrical signal (multiple sclerosis (MS)).
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